Masters Degrees (Animal and Poultry Science)

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Nutritional restriction of the growth rate of broiler breeder replacement pullets.
(1971) Gous, Robert Mervyn.; Stielau, Werner Johannes.
No abstract available.
Suckling behaviour and fertility in beef cows on pasture.
(1990) Stewart, Iona Boles.; Lishman, Arthur William.
The suckling behaviour of 66 Hereford and Simmentaler cows was studied. The average frequency of suckling in 24 hours was four times, and the average duration of each suckling bout was 10 minutes. Suckling events were not evenly distributed throughout the 24 hour period. Regardless of suckling frequency or days post partum, the most favoured suckling period was between 04:00 and 06:00, i.e. dawn. The lowest incidence of suckling was recorded in the period from midnight to dawn. The longest interval between two suckling bouts over the 24 hours always occurred before the dawn and became longer as the calf grew older (p<0,01). Once the mating season commenced, the onset of oestrus was positively correlated (p<0,01) to the length of the longest inter-suckling period. Suckling behaviour was not affected by the milk yields of the cows studied . In a follow up investigation, 88 cows were separated from their calves for 12 hours out of 24, for the fortnight prior to the start of the breeding season. Fifty-six percent of the 44 cows which were separated from their calves from 18:00 to 06:00 (dayfeeders) exhibited oestrus within 28 days of the breeding season, compared to 22% of the group separated from 06:00 to 18:00 (p<0,01). It was concluded that not only the suppression of suckling may be involved in the onset of ovarian activity . The specific time period during the 24 hours when suckling is prohibited may also play a role.
The use of the N-alkane technique for measuring herbage dry matter intake in horses.
(1995) Stevens, Dominic Myles.; Van Ryssen, Jannes Bernardus Jansen.; Stewart, Peter Greig.
The use of n-alkanes as indigestible markers for the estimation of herbage dry matter intake in grazing ruminants, is reported to have significant advantages over other markers used for this purpose (Dove and Mayes, 1991). The use of n-alkanes to estimate herbage intake in horses has not previously been reported, and was therefore investigated in this study. A preliminary trial, carried out in order to investigate possible practical problems in applying the technique to horses, showed that administration of the external marker (C32) in the form of coated grass pellets was satisfactory. Practical difficulties likely to be encountered in carrying out further indoor feeding/faecal collection trials were highlighted during this trial. Four, mature, thoroughbred geldings were used in an indoor feeding and total faecal collection trial to determine the accuracy of intake estimates made using the C31:C32 and C32:C33 n-alkane pairs. The faecal recovery of C31, C32, C33 and C36 as well as the ability of these n-alkanes to provide estimates of diet digestibility were also investigated. Estimates of intake made using the C32:C33 pairs were not significantly different (P< 0.05) from measured intake when the horses were consuming fresh Lolium perenne or Pennisetum clandestinum, P. clandestinum hay or a mixture of concentrates and hay. Overall, error of intake estimate using this n-alkane pair in the total collection trial was 4.8 ± 7%. The C31 :C32 n-alkane pair gave estimates of intake for individual animals that gave significant differences (P<0.05) from measured values when the horses were consuming P. clandestinum hay and the hay + concentrate diet. However, mean intakes were not significantly different (P>0.05) from measured intakes for the fresh L. perenne or P. clandestinum, or hay diet. Overall error in intake estimate was 8.5 ± 16%. Faecal grab samples taken twice daily gave mean estimated intake values which were not significantly different from measured intakes However, estimates of the intake of certain individual animals were found to be significantly different from measured values, using either of the n-alkane pairs. The overall error in intake estimate was 15.1 ± 14% and 4.0 ± 14% for the C31:C32 and C32:C33 estimates respectively. The faecal recovery of the n-alkanes was significantly lower (P< 0.05) when horses consumed L. perenne than when consuming the P. clandestinum grass, grass hay or a mixture of hay and concentrates. The recovery of the C31 , C32 and C33 n-alkanes were similar to those reported for ruminants (Dove and Mayes, 1991). However, there was no significant increase in n-alkane recovery with increasing chain length, and the recovery of C36 was significantly lower than reported in previous studies with ruminants, suggesting differences in behaviour of n-alkanes in the digestive tracts of ruminants and horses. Single doses of C32 resulted in peak faecal concentrations of C32 being reached between 20 and 32 hours after marker administration, after which the levels of the n-alkane decreased rapidly. Complete C32 excretion appeared to be complete 56-64 hours after final dose administration. Single, daily doses of C32 appeared to be insufficient to produce a steady state of faecal C32 marker excretion in the horse, the extent of which may have been influenced by the diet being consumed, resulting in marked diurnal variation in faecal n-alkane concentrations. The results of this trial showed that reasonable estimates of herbage intake in the horse may be obtained using the C32:C33 n-alkane pair. The C31:C32 n-alkane pair was a less reliable indicator of intake but may still be used to provide intake estimates. However, more frequent administration of external n-alkanes than once daily dosing, may be necessary to improve the accuracy of intake estimates made using faecal grab samples, due to the diurnal variation found in this study. The low faecal recovery of the n-alkanes observed in this study made limited their use as digestibility indicators. However, no comparable data is available to confirm the results of this trial. Further investigation is needed with regard to the difference in behaviour of the n-alkanes in the digestive tracts of ruminants and horses. The frequency of external n-alkane marker administration, and the impact of diurnal variation in faecal marker concentration, needs further investigation if the n-alkane technique is to be used successfully with grazing horses.
Capacitation of Nguni semen for in vitro fertilization of bovine oocytes.
(1995) Durrans, Lesley Jane.; Lishman, Arthur William.
In vitro maturation, fertilization and culture is a technique which is increasingly utilised in the animal science industry for embryo production. However, optimal conditions for in vitro maturation, fertilization and culture have not been clearly defined and much research is being done to improve this situation. If these techniques are to be valuable in the production of large numbers of animals in short periods, they must be efficient and reliable. The first part of this investigation aimed to produce comparable rates of fertilization from each of 5 Nguni bulls tested in an in vitro fertilization trial. It was hypothesised that each bull would respond favourably to one or more of the treatments tested. A complete randomised block design was set up to account for block and day effects. A total of 2422 cumulus-oocyte complexes were matured and fertilized with swim-up separated frozen-thawed Nguni semen incubated for 1 min in Ca-ionophore A23187 (0.1, 0.2 or 0.4 µM) or for 15 min in heparin (0.05, 10 or 25 µg/ml). Controls for parthenogenesis and capacitation or acrosome reaction in the fertilization medium were included. Presumptive zygotes were transferred to CR1aa medium and supplemented with 10% and S% FCS on days 4 and 7 post-insemination, respectively. Bull performance was assessed using four criteria: embryo cleavage, a score based on a cleavage index (Score 1; minimum -1, maximum 6) and one which gave greater weight to morulae and blastocysts (Score 2; minimum -1, maximum 10) and blastocyst production. Day effects were highly significant (P<0.001). Parthenogenetic activation of 31.6% of oocytes occurred. Depending on the bull used, cleavage rates (%±s.e.m.) varied from 29.S±2.2 to 40.6±2.6, Score 1 from 0.30±0.07 to 0.6S±0.07, Score 2 from 0.30±0.07 to 0.72±0.08 and % blastocysts from 0.6±0.6 to 4.8± 1.1. Treatment did not significantly affect performance and there were no bull x treatment interactions. However, bull differences in performance were observed. The IVF system employed was not stable and did not produce repeatable results. It was concluded that treatment concentrations tested may have been too low or, alternatively, that treatment effects were being masked by a factor influencing the IVF system more strongly than the treatments tested. In the second part of this investigation, laboratory tests to determine semen quality were examined. It was hypothesised that semen quality would correlate with performance determined during the in vitro trial and, thus, provide predictors for bull fertility in vitro. A dual staining procedure which detects live/dead or acrosome reacted/not acrosome reacted sperm was also utilised to determine whether bull x treatment interactions may have existed in the in vitro trial but were obscured by other factors influencing the IVF system. Sperm motility and abnormal morphology were assessed using light microscopy on whole frozen-thawed semen samples. Statistical analysis could not be done because of lack of replication. Percentages of immotile sperm were high (60.16% to 78.51%), with considerable variation in progressive motility (13.90% to 34.35%) between bulls. A large variation in numbers of morphologically normal sperm was observed between bulls (66% to 90%), with major deformities (9% to 19%) accounting for most of the abnormalities. High negative correlations with performance (as defined in the in vitro trial) were found between % normal sperm and % proximal droplets (r=-0.66 to -0.88). Percentage of minor abnormalities, distal droplets and coiled tails correlated positively with fertility (r=0.67 to 0.91). Motility did not correlate highly with any of the criteria used to assess bull performance. Correlations of semen quality to performance were contradictory to expected results and this may have been due to swim-up separation of sperm for the in vitro trial which was not carried out for semen quality assessment. At present, these semen quality tests do not allow prediction of bull fertility in vitro. Assessment of sperm stained for evaluation of live/dead and acrosome reacted/not acrosome reacted was a lengthy procedure. Again, statistical analysis was not possible due to the lack of replication. High percentages of sperm were characterised as dead (52.4% to 100%). Bulls did respond differently to the various treatments, as determined by the proportion of acrosome reacted sperm and live acrosome reacted sperm. Thus, bull x treatment interactions were apparent, suggesting that the IVF system was more strongly influenced by other factor(s) which reduced sensitivity to the treatments tested. In summary, more research is needed to stabilise the IVF system if production of large numbers of embryos is to become economically viable.
The effect of different methods of controlling urolithiasis on ovine mineral metabolism.
(1995) MacCallum, Kim Barbra.; Van Ryssen, Jannes Bernardus Jansen.
The widespread use of high-energy, low roughage diets among feedlot sheep has lead to the development of several production diseases (Bide et al., 1973). One of the least easily identifiable is urolithiasis, yet it is an important cause of death among feedlot sheep (Emerick, 1988). The primary causative factors of urolithiasis are an alkaline urine and a high urinary P level (Bushman et al., 1965a, 1965b, 1968). The prevention of this disease therefore involves the use of an anionic salt such as NH4Cl in the diet, to acidify the urine, or the use of a high Ca:P ratio in order to decrease urinary P levels (Bushman et al., 1965a; Robbins et al., 1965). At present NH4Cl is included in sheep rations with the express purpose of preventing urolithiasis. However, this method has a disadvantage as anionic salts have been shown to cause metabolic acidosis (Harmon & Britton, 1983) and therefore the second means of prevention, that of a high Ca:P ratio, may be the more suitable method. For this reason, an experiment was designed in order to determine whether NH4Cl or a high Ca:P ratio was the better method of urolithiasis prevention with respect to the animal's performance, mineral metabolism and acid-base status. Furthermore, the effect of Ca and NH4Cl on Se metabolism was studied as very little work has previously been done on this subject. With this objective in mind, a growth trial and digestibility study were conducted. For the growth trial, a 3 x 2 x 2 factorial experiment was designed with three levels of NH4Cl (0, 0.75 and 1.5%) at a high (4: 1) and medium (2.5: 1) Ca:P ratio. Se was included in the diet at a level of 0 and 0.3mg/kg. The trial extended over a period of 74 days, and during this time weight and feed intake were measured, and blood, urine and faecal samples were collected for mineral and acid-base status analysis. At slaughter, the liver, kidney, heart, pancreas and a portion of the Longissimus dorsi muscle were removed for mineral analysis. Fluid from various sections of the digestive tract was sampled for digesta pH determination. The digestibility trial was designed as a 4 x 4 latin square change-over design which was based upon a ten day preliminary period and a five day collection period. Urine volume and pH were measured, and faecal mass and feed intake recorded to allow for the determination of the digestibility of the treatment feeds. NH4Cl was found to affect most criteria considered. Increasing levels of NH4Cl caused performance criteria (mass and feed intake) to decrease, as did blood pH, HC03 and BE values. Liver and kidney dry mass, and the urinary excretion of Ca, P and Mg increased. Urine pH and faecal mineral excretion decreased. The effect of 0.75 % NH4Cl on the animal was not significantly different to that of the 0% NH4Cl diet. However, 1.5% NH4Cl had a significantly adverse effect on the animal. The high Ca: P ratio was found to improve mineral retention although absorption decreased as evidenced by an increased faecal mineral excretion. Blood acid-base status was adversely affected by the higher limestone level as blood pC02 levels increased causing blood pH to decrease. Thus, a high limestone level was symptomatic of respiratory acidosis, although blood pC02 levels were not sufficiently high to allow for this classification. The NH4Cl x Se interaction significantly affected blood acid-base status, urine pH and urinary P excretion. The addition of Se to the diet was found to have a slight alkalizing effect on the animal, as it raised blood acid-base status and urine pH above that of the diet containing no additional Se. The NH4Cl x Se interaction also caused urinary P excretion to increase, especially at an NH4Cl level of 1.5%. The NH4Cl x Ca interaction produced varied results, as the high Ca x 1.5% NH4Cl diet had the most detrimental effect on mass and feed criteria and blood BE values, while the most acidic combination according to abomasal and duodenal pH, blood pH, urine volume and urinary mineral excretion was the medium Ca x 1.5% NH4Cl diet. From the results of the current investigation, it was concluded that the best method of preventing urolithiasis was through the addition of 0.75% NH4Cl to the diet, as this resulted in an acidic urine and yet had no significantly adverse effect on the performance, mineral metabolism or acid-base status of the animal.
Performance of Hereford and Holstein heifers on kikuyu pasture (Pennisetum clandestinum), using n-alkanes for determination of digestibility and dry matter intake.
(1995) Horne, Tim.; Stewart, Peter Greig.
Kikuyu pasture (Pennisetum clandestinum) is potentially the most important source of roughage used to feed dairy heifers in summer in KwaZulu-Natal. It is commonly believed that on kikuyu pasture beef breed females grow at a faster rate than those from dairy breeds when no supplementation is given. Little conclusive evidence is, however, available to support this. Explanations as to why such differences may exist are also limited. Eight Hereford and eight Holstein heifers of similar age and maturity stage were used in a trial. The trial was run over a twenty week period. For the first ten weeks all the animals in the trial grazed ad libitum kikuyu pasture with no supplementation except for a mineral lick. Over this (grass only) period the two breed groups formed the two treatments. During the second ten week period of the trial all of the Holsteins and four of the Herefords were fed a restricted but equivalent amount (1 .7 kg) of a maize meal based concentrate. The use of a computerized, mobile feeding system allowed concentrate intake of individual animals to be measured. Animal height, weight and condition score readings were taken weekly over the grass only and the concentrate (final seven weeks) periods of the trial. Herbage intake and digestibility were estimated using n-alkanes as indigestible markers in two experiments conducted during the grass only and concentrate periods. The Herefords had a significantly higher ADG than the Holsteins (0.82 vs. 0.04 kg/day; P < 0.01) over the grass only period. During the concentrate period the rate of mass gain of the Holstein treatment did not differ significantly (P >0.05) from the Hereford treatment receiving concentrate. The Herefords receiving concentrate were also not significantly different (P > 0.05) in rate of mass gain from the Herefords not receiving concentrate. Rate of height gain was not significantly different (P> 0.05) between treatments over either the concentrate or the grass only periods. During the grass only period the Holsteins lost condition (0.07 condition score units per week) whilst the Herefords gained condition at an equivalent rate. The voluntary intake of concentrates was not significantly different (P > 0.05) between the Herefords and Holsteins (19.19 vs. 16.40 g/kg/L.W(liveweight) (0.75)). Regression coefficients relating level of concentrate intake to rate of mass gain were also not significant (P > 0.05) for either of the treatments receiving concentrate. The use of n-alkanes as indigestible markers showed the intake of the Holstein treatment to have an intake 55% (P < 0.0 1) higher than the Herefords (185.4 vs. 120.5 g/kg L.W(0.75)) over the first experiment where both treatments were grazing ad lib. kikuyu alone (grass only period). During the concentrate period intake of the Herefords receiving concentrate exceeded that of the Holsteins (P < 0.01) by 23% (139.1 vs. 113.1 g/kg L.W(0.75)). Review of the literature, suggests that the double alkanes technique greatly over-estimated intake. Errors in herbage sampling (accentuated by pasture rotation in the first experiment), a low daily dose of the synthetic alkane (C(32)) and incorrect estimation of the C(32) content in the daily doses are identified as possible causes of the over-estimation of intake. Faecal recoveries of the herbage n-alkanes were demonstrated to increase with increasing chain length and hence C(35) was proposed as the most reliable herbage alkane for dry matter digestibility determination. Digestibility differences between treatments estimated using the C(35) alkane were not significantly different (P > 0.05) in either the first or second experiments. The mean digestibility estimates (using the C(35) alkane) for the first and second experiments were 64.9 and 56.61 %, respectively. In conclusion, higher growth rates of Herefords on kikuyu pasture would seem to be primarily due to differences in the dry matter intake of the grazed herbage. Further work using other breeds of dairy and beef animals is required. The underlying cause of differences in dry matter intake between breeds also requires investigation.
Attempts to improve the yield of bovine blastocysts by incorporating insulin, selenium and transferrin in the In Vitro system.
(1996) Bowles, Chloe Melissa.; Lishman, Arthur William.
To produce an embryo via in vitro maturation, in vitro fertilization and in vitro culture methods it is vital to obtain consistent results and at the same time a large number of bias to cysts from the immature oocytes collected, especially when only a small pool of these oocytes are available. The aim of the present investigation was to improve maturation rates, fertilization rates and blastocyst production rates by adding insulin (10 µg/ml), selenium (10 ng/ml) or transferrin (10 µg/ml) to the media. These were added individually or in different combinations and a complete randomised block design was set up to account for block and day effects. It was hypothesised that each treatment would improve maturation and fertilization rates and blastocyst production rates. It was found that of the treatments added to the maturation medium, Selenium at 10 ng/ml improved maturation percentages (80.4% vs 61.8%) and also increased fertilization percentages (68.0% vs 58.4%) and the number of bias to cysts produced (24.6% vs 11.5%). None of the treatments had a beneficial effect on fertilization rates or on blastocyst production rates when added to the fertilization medium. The treatments added to the culture medium showed that Transferrin at 10 µg/ml or Transferrin in combination with Insulin and Selenium increased the percentage of bias to cysts produced by in vitro culture methods (35.3% and 31.5% vs 18.7%). The addition of Transferrin also increased the percentage of bias to cysts that hatched (21.9% vs 14.2%) showing an improvement in the viability of the blastocysts produced. It is recommended that the maturation medium should include Selenium at 10 ng/ml. The fertilization process should have none of the investigated substances added to it and the culture medium should include Transferrin at 10 µg/ml. This combination should optimize the number of viable blastocysts that are produced in a bovine in vitro system.
Responses in growing pigs to lysine and threonine limiting feeds and environmental temperature.
(1996) Arnold, Gary Desmond.; Gous, Robert Mervyn.; Ferguson, Neil Stuart.
In this thesis two experiments were conducted. The objective of the first experiment was to measure the response of a range of dietary threonine concentrations and environmental temperatures on the performance of young pigs. Large White x Landrace entire male pigs (n=48) at 12 kg live weight were assigned to one of six dietary threonine treatments (n=2) and one of four temperature treatments. Dietary threonine concentrations were formulated as 8.9 g Threonine/kg food (T1); 6.7 g/kg (T2); 6.2 g/kg (T3); 4.9 g/kg (T4); 3.6 g/kg (T5); 4.9 g/kg (T6). To check that threonine was limiting the most diluted diet (T5) was supplemented with synthetic threonine. The animals were fed ad libitum and housed in environmentally-controlled facilities. The experiment was conducted using four different temperature regimes; 18.1 (±0.38)°C, 21.9 (±0.19)°C, 26.1 (±0.50)°C and 29.9 (±0.34)°C. On reaching 25 kg live weight the pigs were slaughtered and the carcasses prepared to obtain samples for carcass analysis. There were significant differences (P < 0.001) in the rate of growth (ADG) between dietary treatments with the highest gains on T1 (0.571 kg/d). There were significant differences (P < 0.01) in ADG between temperature treatments with the highest growth rate at 22°C (0.527 kg/d) and the lowest at 30°C (0.428 kg/d). Food intakes were significantly affected by temperature (P < 0.001) and unaffected by dietary threonine concentrations. There was a 26.1 % increase in feed intake at 18°C when compared to the feed intake at 26°C. The highest FCE was recorded at 26°C (449 g gain/kg food) and the lowest at 18°C (386 g gain/kg food). There was an 18.4% reduction in body protein content at 25 kg live weight between pigs fed on Tl as opposed to those fed on T5. Dietary treatment had a significant effect (P < 0.001) on the fat composition of the empty carcass. The highest fat content was on T5 (4.898 kg) and the lowest on T1 (2.041 kg). Temperature had a significant effect (P < 0.001) on lipid growth rates. Threonine accretion rates were higher (P < 0.001) for pigs fed on T1 (3.52 g/d) than those fed on T2 to T5. The lowest threonine retention was on T5 at 1.49 g/d. Linear regression of daily carcass threonine accretion on daily threonine intake resulted in an efficiency of threonine utilization for pigs between 12 kg and 25 kg live weight of 38%. The objective of the second experiment was to measure the response of dietary lysine concentrations and environmental temperature on the performance of young pigs. Large White x Landrace entire male pigs (n=48) were assigned to one of six dietary lysine treatments (n=2) and one of four temperature treatments. Dietary lysine concentrations were formulated as 12.7 g Lysine/kg food (T1); 10.8 g/kg (T2); 8.9 g/kg (T3); 7.0 g/kg (T4); 5.1 g/kg (T5); 7.0 g/kg (T6). To check that lysine was limiting, the most diluted diet (T5) was supplemented with synthetic lysine. The animals were fed ad libitum and housed in environmentally controlled facilities. The experiment was conducted using four different temperature regimes; 18.1 (±0.19)°C, 22.0(±O.17)°C, 25.7 (±O.32)°C and 29.6 (±O.40)°C. On reaching 25 kg live weight the pigs were slaughtered and the carcasses prepared for chemical analysis. There were significant differences (P < 0.001) in ADG between dietary lysine treatments, with the highest gains on T1 (0.621 kg/d) and the lowest on T5 (0.395 kg/d). There were significant differences (P < 0.001) in ADG between temperature treatments, with the highest growth rate at 22°C (0.588 kg/d) and the lowest at 30°C (0.466 kg/d). Food intakes were significantly affected by dietary treatment (P < 0.05) and environmental temperature (P < 0.001). The highest feed intake was on T4 (1.284 kg/d) and the lowest on T1 (1.080 kg/d). There was a 21.4% increase in feed intake at 18°C (1.394 kg/d) when compared to the feed intake at 30°C (1.096 kg/d). The highest FCE was recorded at 22°C (491 g gain/kg food) and the lowest at 18°C (417 g gain/kg food). There was an 19.9% reduction in body protein of pigs at 25 kg live weight fed on T1 (3 .715 kg) as opposed to those fed on T5 (2.976 kg). Dietary treatment had a significant effect (p < 0.001) on the fat content of the empty carcass. There was an increase of 134% in the fat content of the empty carcass between those pigs fed on T5 as opposed to those fed on T5. The highest fat content was on T5 (4.926 kg) and the lowest on T1 (2.103 kg). There were significant differences in protein accretion rates (p < 0.001) between the dietary and temperature treatments. The highest PR was on T1 (91.85 g/day) and at 18°C (77.08 g/day). The highest THL (P < 0.05) was at 18°C (12.84 MJ/d). Lysine accretion rates were highest on T1 (6.475 g/d) and lowest on T5 (2.726 g/d). Linear regression of daily carcass lysine accretion on daily lysine intake showed that the efficiency of lysine utilization for pigs between 12 kg and 25 kg live weight was 37%.
Some factors affecting weaning weights of calves.
(1996) Kunene, Nokuthula Winfred.; Lishman, Arthur William.
A mixed model study was carried out on the field data records of 9798 Simmmental and 1725 Hereford calves born during the period 1992 to 1994, and obtained from the Animal Improvement Institute, Irene. The records were used to evaluate the influence of type of management systems used by breeders, type of vegetation, sex of calf, age of dam, year of birth and season of birth on 205 day weight of calves and some two way interactions between these effects. The analysis were carried separately for each breed. Type of management did not significantly affect the 205 day weight of Hereford calves, the least-squares means of calves from extensive, semi-extensive and intensive systems were 195.8, 196.9 and 197 kg, respectively. However, the effect was highly significant (P<.01) for Simmmental calves with weaning weights of 217.4, 238.3 and 261.2 kg for extensive, semi-extensive and intensive production systems, respectively. The Simmmental data were divided for further analysis according to the three management systems. All the main effects on the 205 day weight of Simmmental calves were highly significant for all the management systems. Simmmental calves raised in the combination of fynbos and pastures under the semi-extensive management system weaned the heaviest calves (295.8 kg) and those raised in the mixed grassveld under the extensive system weaned the least (202.4 kg) . The Simmmental male calves were 10, 9.8 and 17.9 kg heavier than female calves in the extensive, semi-extensive and intensive systems respectively. The mature age of the dam was between the 52 to 57, 58 to 117 and 52 to 57 month age groups with weaning weights of 230.7, 257.7 and 266.4 kg in the extensive, semi-extensive and intensive systems respectively. The deviations of weight of calves of the mature dams from those of young dams (16 to 27 months) were 26.9, 30 and 20 kg under the extensive, semi-extensive and intensive systems, respectively. The main effects on the 205 day weight of Hereford calves, except the type of management, were highly significant (P<.01). The Hereford calves raised in the sweetveld areas produced the highest weights (218.6 kg) but those raised on the karroo were the lightest (188.1 kg). The best calving seasons were autumn and winter, with the mean weight of 215.1 kg and 202.9 kg, respectively. Summer and spring born calves weighed 180.2 and 188.2 kg, respectively. The Hereford male calves were 13.2 kg heavier than the heifers. The maturity age of the dams was between the 72 to 95 month age group with the deviation of 20 kg in weaning weight of their calves from those of the young dams (22 to 27 months old). The sex and age-of-dam interaction for both breeds indicated an overall correction factor for sex of calf and of age of dam. Multiple adjustment factors were used to remove sex of calf differences, whereas additive adjustment factors were used to remove age-of-dam differences.
An investigation into growth in Jersey, Holstein and Hereford heifers on kikuyu pasture (Pennisetum clandestinum) using N-Alkanes to estimate intake and ruminal outflow rate.
(1997) Fushai, Felix M.; Stewart, Peter Greig.
The experiment was designed to investigate why dairy heifers perform poorly on kikuyu pasture compared to a beef breed like the Hereford. The main assumption was that the lower growth rate in dairy breeds was due to low intake as a result of slower passage of digesta out of the reticulorumen. Eight animals in each breed (Jersey, Hereford and Holstein) were grazed continuously on 6.25 hectares of kikuyu. The Jerseys had to be dropped from the second part of the experiment due to health problems. The experiment was conducted from December to April and was split into two trials with half the animals in each breed on a maize supplement during the last eight weeks of the experiment. During the first trial (T1), average daily gain was 1.18, 0.54 and 0.2 kg per daily in Herefords, Holsteins and Jerseys respectively. Herefords grew significantly faster than both the Holsteins and the Jerseys (p<0.01). The Holsteins also grew significantly faster than the Jerseys (p<0.05). In trial 2 (T2), average daily gains were 0.732 and 0.561 in Herefords and Holsteins respectively. Supplemented Herefords had and average daily gain of 0.797 compared to 0.668 kg in non-supplemented animals. Supplemented Holsteins had an average daily gain of 0.497 compared to the 0.624 in non-supplemented animals. There were no differences in growth in T2 (p>0.05). N-alkane estimated intake in T1 using the C32/C33 alkane pair was 117.7, 92.7 and 97.6g/kg LW(0.75) in Herefords, Holsteins and Jerseys respectively. The Herefords had significantly higher intake compared to both the Holsteins and the Jerseys (p<0.05). In T2, the Herefords had a significantly higher intake (p<0.05) of 104.4 compared to 98.0g/kg LW(0.75) in the Holsteins. In T1, n-alkane estimated digestibility was 59.8, 56.8 and 51.4% in Herefords, Holsteins and Jerseys respectively. The Herefords had significantly higher apparent digestibility compared to the Jerseys (p<0.05). In T2, the Herefords had a digestibility of 61.6 compared to the Holsteins at 60.5%. The difference was not significant (p>0.05). Estimated outflow rate (kl) using Cr(2)O(3) was 0.056, 0.062, 0.061 and 0.056/h in supplemented Herefords, non-supplemented Herefords, supplemented Holsteins and non-supplemented Holsteins respectively when data was fitted into a multi-compartment model. When the data was fitted into a two-compartment model, estimated kl values were 0.069, 0.063, 0.090, and 0.061/h also respectively. When data obtained from using alkane coated hay was used, kl values obtained by a graphical procedure were 0.035, 0.042, 0.038 and 0.042/h also respectively. Neither breed nor supplement had a significant effect on outflow rate (p>0.05).
The interactions between maturity type and pre-feedlot plane of nutrition on the growth and performance of steers.
(1997) Dominy, Neil John.; Stewart, Peter Greig.
The growth of tissues (bone, muscle and fat), along their natural growth curve, is controlled by a complex array of interactions. Growth gradients exist between the tissues and the body as a whole, bone being earlier maturing than muscle, and muscle being earlier maturing than fat. Growth waves within each tissue express its rate of deposition within in each area of the body. Differences between maturity types with respect to tissue growth, is that the earlier maturing animal is further along its normal growth curve. Comparison between maturity types must therefore be performed at an equal physiological age. Restriction of nutrients to the growing animal results in an alteration of the body composition. The most affected tissue being the tissue with the highest growth impetus at the time. Severe restriction (loss of liveweight), can result in the tissues following a reverse order of their deposition. Re-alimentation results in tissue growth at a rate superior to animals of an equal chronological age. Those tissues that were most restricted in their growth, are the ones that show the most compensation. A trial was carried out, to examine, the question of animals of differing pre-feedlot planes of nutrition, and maturity type, performances within the feedlot at an equal physiological age. Four treatments were used comprising earlier maturing fat and thin animals and later maturing fat and thin animals. Earlier maturing comprised Hereford and Sussex breeds, while later maturing comprised Charolias and Simmentaler breeds. The pre-feedlot planes of nutrition were imposed for 103 days, with the fat animals gaining at 0.40 kg per day and the thin animals at 0.10 kg per day. Both treatment groups lost condition but started the feedlot period significantly different with respect to liveweight and condition. Physiological age was to be determined, by the weight of the animals body protein, as a proportion of the maturity types, mature body protein weight. The urea dilution technique was used to determine the body composition of the treatments at any one point of time. Due to complications with the application of the technique, the body compositions of the animals were not determined with any degree of certainty. Thus it was impossible to compare the feedlot performances of the treatments at equal physiological ages, or compare their changes in tissue weights over time. Differences in tissue deposition rates were measured. Compensating animals had significantly higher growth rates in terms of height. This equates to a higher rate of bone tissue growth. As height measurements were not taken during the pre-feedlot period this could not be attributed to compensatory growth. Ultrasonic measurements of eye-muscle diameters, showed that the compensating animals and the later maturing fat animals to be growing at a non-significantly different rate. This could, possibly, be due to the animals depositing at the maximum allowable rate. Subcutaneous fat deposition was measured as change in condition score. Compensating animals deposited fat at a significantly faster rate, with no significant differences between maturity types being apparent. All animals were slaughtered at a set condition. This resulted in the early maturing fat animals, spending a significantly shorter period of time in the feedlot. Analysis of subcutaneous fat depths found no significant differences between treatments, indicating that the animals had been slaughtered at equal condition scores. Fat distribution over the measured sites however showed that there were significant differences between the compensating animals. The earlier maturing being to fat and the later maturing being to thin. Thus the two groups could have spent a shorter or longer period of time in the feedlot respectively. liveweight changes over time were as predicted. The late maturing treatments had significantly higher growth rates than their respective earlier maturing treatments. The compensating treatments also had significantly higher growth rates than respective non-compensating treatments. Only the early maturing thin animals managed to make up the deficit sixty kilograms. Feed and net energy available for growth (NEg) intakes, were complicated, with anomalies being found in the data distribution. Animals feed and NEg intakes increased linearly, before peaking at the same point of time irrespective of maturity type, and then followed a linear trend of significantly different slope. The quadratic model failed to follow the data trend accurately enough so the broken stick model was used. Compensating animals ate significantly more food and NEg per kilogram of metabolic weight (W (0.75)). There utilisation of the food and NEg was however significantly more efficient than the non-compensating animals. No significant differences were found between maturity types within pre-feedlot treatments. Further investigation is required into the anomalies surrounding the analysis of the feed and NEg intake data. A biological justification must be found for the use of the broken stick model. The change in the linear trend after peak feed intake appears to be due to a restriction. This restriction should be determined as it affects animals irrespective of nutritional requirements.
Matching the nutritional requirements to performance in broiler breeder hens.
(1997) Goddard, Leanne Lisl.; Gous, Robert Mervyn.
Quantitative food restriction during the rearing and laying period has become the standard management procedure in commercial broiler breeder operations to control the rapid growth rate of broiler breeders. This raises problems with the amount of each nutrient to be supplied each day. Food allowances are manipulated according to the pattern of egg production. Birds are fed a generous allowance early in lay followed by a period of mild regulation over peak production and a subsequent reduction in allowance as egg production declines in the later part of lay. In the past little work has been done on developing the theory of determining the nutrient requirements of broiler breeders. Consequently, this generally accepted method of feeding these breeders is without a sound theoretical basis. The objective of this study was to address two aspects concerned with meeting the requirements of broiler breeder hens during the laying period, specifically in the later stages of lay. The first is the obesity in broiler breeders that results from an excessive intake of energy and leads to a decrease in egg production. The second is the rapid decline in egg production in ageing hens. Individual data were collected from broiler breeder hens in two experiments. The first to determine the extent to which broiler breeder hens could be made to utilize excess body lipid reserves whilst maintaining laying performance. The second to measure the responses to lysine at different ages and to determine if the efficiency of utilization of lysine changes at different ages. Results from the first experiment indicated that broiler breeders can utilize their body fat reserves as an energy source providing that their protein intake is sufficiently high and that they could maintain egg production for at least a limited period of time. Birds fed an energy intake of 1490 kJ ME/bird d and a protein intake of 25.8 g/bird d showed no decline in egg production compared to birds fed much higher energy intakes (1900 to 2000 kJ ME/bird d). It was concluded from this experiment that if birds become overfat at any stage in their productive lives this situation can possibly be rectified by feeding them diets with low energy contents. In the later stages of lay and on cold days birds can probably be fed energy intakes below their requirements with no detrimental effect on egg production. Results from the second experiment indicated that the efficiency of utilization of protein declines as broiler breeders age. The efficiency of utilization of lysine was significantly lower for birds of 53 and 65 weeks of age compared to birds of 31 and 42 weeks of age. This decline in efficiency with age was attributed to the fact that efficiency decreases when the rate of lay decreases to below 50%. There was therefore no indication that the protein requirements decrease as the laying year progresses although egg production declines. It was suggested that new methods of feeding broiler breeder hens later in lay be investigated because the present method of decreasing the food allowance at this time is probably not the most ideal way to achieve maximum performance.
Performance of feedlot cattle with reference to carbohydrate digestion of maize versus hominy chop.
(1997) Van der Veen, Rudolf Hibbe.; Stewart, Peter Greig.
No abstract available.
The use of choice feeding and mixture experiments to evaluate protein sources used in broiler feeds.
(1997) Swatson, Harry Kofi.; Gous, Robert Mervyn.
No abstract available.
An investigation of factors influencing rate of lay, egg weight and embryonic growth in broiler breeder hens.
(1998) McLoughlin, Leigh.; Gous, Robert Mervyn.
The laying performance of broiler breeder hens is characteristically poor. Of the eggs that are produced, a large proportion are rejected before setting because they are either too small or excessively big, and of the eggs that are set, hatchability rates are often low, depending on the age of the hen. Since so much is still unknown about broiler breeders, many avenues of research would be fruitful. In this study, four disparate aspects were investigated as a means of improving the number of hatchable eggs per hen. The effect of linoleic acid intake on egg weight of broiler breeders and laying hens was compared. Analysis of both published and experimental data revealed that egg weight was influenced significantly by this fatty acid. Breeder egg production was affected concomitantly. Increasing linoleic acid intake of young hens would increase early egg size and the number of eggs set, while decreasing the linoleic acid intake of ageing breeders would decrease egg size and production. The influence of 20 week body weight and nutrient intake on early laying performance of 360 broiler breeders was determined. The excellent performance achieved was independent of 20 week body weight. Laying performance and weight gain increased as food allocation and nutrient density increased. A comparison of theoretical and recommended nutrient intakes revealed that hens are overfed pre-peak and that energy intakes should not decline post-peak as is recommended. The investigation into the effect of breeder age (egg size) on embryonic and chick growth revealed that exponential embryonic growth was restricted within small eggs due to a lower yolk supply, rate of yolk absorption, and water loss. Chicks from small eggs were light, and grew relatively slowly. However, during times of chick shortage, small eggs could be used successfully if managed correctly. In the fourth experiment in this series, the response of laying hens to dietary tryptophan was measured successfully, but the objective of comparing this response with that of broiler breeders failed. As a result of overestimating the tryptophan requirement of breeders, the coefficients of response could not be estimated. It was concluded that an additional breeder tryptophan trial should be conducted.
An evaluation of effective energy in the formulation of diets for laying hens.
(1998) Young, Marion Belinda.; Gous, Robert Mervyn.
Emmans (1994) introduced a concept of energy utilisation applied across species, in which a heat increment in feeding is considered to be linearly related to five measurable quantities. Subtracting the heat increment of feeding from the metabolisable energy supplied defines the energy supply scale called effective energy. Two trial protocols were developed and run in controlled environment chambers at hot and cold temperatures using laying hens in individual cages. The first trial tested the response of hens at temperatures of 18°C and 32°C to the dilution of a basal diet with ingredients selected to promote a heat increment in different manners, according to the effective energy system. Diluents were soy protein isolate, fishmeal, sunflower oil, husks and sugar and starch mix. Six diets were offered to Amberlink and Hyline Brown hens for two successive periods of six weeks at the two temperatures. Responses in performance and calculated heat production indicated that heat increments could be induced by particular diluents. These affected the response in laying performance of the birds, particularly at high environmental temperatures. A second protocol tested the absolute value of the effective energy system by using Amber link hens for three consecutive seven week periods at 30°C, 20°C and 30°C, respectively. High and low effective energy diets were formulated, and blended, and compared against commercial high and low density diets. The effective energy diets and the commercial diets were also offered as a choice to the hens. The data illustrate a marked linear response to the effective energy in the diet. High effective energy produced the same response as a high nutrient density at high temperatures. Highest performances in lay were achieved on the choice diets. The hens demonstrated the ability to change the proportion of the choice of the effective energy diets at the different temperatures. Dynamic heat exchanges with the environment become significant, especially at higher temperatures in the thermally active hen. Effective energy considers this heat response, and can assist in ameliorating the response of the laying hen to high environmental temperatures when incorporated into principles of feed formulation.
The biological and economic responses of growing pigs to nutrient density.
(1999) Nelson, Lyska Michelle.; Gous, Robert Mervyn.; Ferguson, Neil Stuart.
No abstract available.
The digestibility, intake and faecal marker patterns of Hereford and Friesland bulls consuming kikuyu (Pennisetum clandestinum) using N- alkanes.
(2000) Mann, Joanne.; Stewart, Peter Greig.
Kikuyu is an important summer pasture species in South Africa for animal production, and is seemly suitable for growing out dairy replacement heifers. Previous research by Horne (1996) and Fushai (1997) showed that Friesland heifers had disappointing growth performance on kikuyu and concluded that there was an intake problem. In this study, Friesland (FB) and Hereford bulls (HB) were compared (with respect to growth, intake digestibility, faecal marker excretion patterns and time spent grazing) to investigate the previously identified intake problem of Friesland heifers. Growth parameters (weight, height and condition score) were measured (during summer and autumn) for five FB (remaining three Friesland bulls were excluded due to disease) and eight HB while on kikuyu pasture. The average daily gain was 0.66 kg per day with no significant difference between treatments. Average height and condition score gain were not significantly different. The alkane method was used (and was compared with Calan gate intake estimates) to determine intake and digestibility estimates (seven days). The alkane method compared favourably with the Calan gate estimation of feed intake (coefficient of variation was 22 %). No significant differences were found between the breeds for intake and the average intake was 93 g DM/kg W 0.75/day. Apparent dry matter digestibility (calculated by alkane method) was 6 % higher (P < 0.05) in the Friesland bulls over the Hereford bulls. Apparent dry matter digestibility estimates were measured (three FB and three HB; five days) while animals were confined to metabolic crates. Dry matter digestibility was not significantly different between treatments with the average estimate being 696 g/kg DM. However, intake was 11 % greater (P < 0.05) for the Friesland bulls when expressed on a metabolic basis (g DM/kg W 0.75/day). Amount of faeces produced and nutrient digestibility estimates (crude protein, NDF and ADF) were the same for the breeds. The dry matter of faeces varied in that the Friesland bulls produced faeces 25 % drier than the Hereford bulls. Faecal marker excretion patterns were plotted (four days) after oral administration of an alkane marker (three FB and three HB). The Grovum and Williams (1973) model indicated no significant differences in the digesta flow between treatments. Mean retention time was 45 hours for the alkane marker. QDQ curve analysis fitted two separate curves (r 2 =0.91) but peak times were not significantly different. The average peak time was 23.7 hours. A gompertz curve (r 2 =0.97) was fitted to accumulated marker concentration. Linear parameters were significantly different, the Hereford bulls having a greater accumulation of marker concentration over time. Animal activity (time spent grazing, ruminating and idling) was recorded over a 24 hour period (five FB and eight HB). The study was performed twice. There was no significant difference in animal activity between the breeds. The average bull spent 30 % of the day grazing, 34 % of the day ruminating and 36 % of the day was spent idling. At slaughter the heart, liver, lungs and spleen were weighed (five FB and five HB). No significant differences were found when organ weight was divided by metabolic weight. No significant differences were found in the growth rate, feed intake and feed digestibility when comparing Friesland and Hereford bulls on kikuyu pasture, in contrast to the findings of Horne (1996) and Fushai (1997) using Friesland heifers.
The long and short term effects of Leucaena leucocephala on ram fertility.
(2000) Byebwa, Bonaventure Kafuzi.; Nsahlai, Ignatius Verla.
No abstract available.
Meeting nutritional requirements of mature broiler breeder hens.
(2001) Mbambo, Siyabonga.; Slippers, S. C.; Gous, Robert Mervyn.
The overall objectives of this study were to compare the response of broiler breeder hens to dietary lysine at peak rate of lay and late in the laying cycle when rate of lay has declined, to compare the coefficients of response to those previously published, to determine whether there is any interaction between the response to lysine and to energy, and to compare the responses to lysine when broiler breeders are fed either wheat- or maize-based diets. Two experiments lasting 10 weeks were conducted on individually caged broiler breeder hens. In the first experiment, birds from 36 to 46 weeks of age were used, whilst in the second experiment birds from 52 to 62 weeks of age were used. In the first experiment each hen was offered 160 g/d of one of 12 dietary treatments, six dietary lysine concentrations based on both maize and wheat. In the second experiment each hen was offered 150 g/d of one of 12 dietary treatments, consisting of six concentrations of lysine at two different dietary energy levels (low and high) . All the diets in both experiments were produced by diluting one of the concentrate (summit) mixes with the appropriate protein-free dilution diet. Each lysine-limiting diet was designed to supply approximately 1350 mg lysine/bird d when fed at 160 and 150g/bird d for the first and second experiment, respectively, whilst the most diluted feed supplied only 270 mg lysine/bird d. In both experiments birds fed the highest contents of lysine consumed virtually all of the food allocated to them. However, birds on the most diluted diets consumed less than half of the daily intake of the birds on the summit feeds. By fitting the Reading Model to the data from each experiment, the coefficients of response were calculated to be 8.44E and 0.01W for wheat-based diets, 7.75E and 0.02W for maize-based diets, 10.23E and 4.57W for low energy series diets, and 9.29E and 0.01W for high energy series diets. The pooled data for both energy series produced coefficients of 9.41E and 0.00W. Since Bowmaker (1986) estimated the body weight coefficient for broiler breeders to be 11.2 it was then decided to use an assumed body weight coefficient of 10 and the 'a' coefficient was recalculated using the equation: a = (I-bW)/ E. The overall a coefficient became 15 and 13 for wheat- and maize-based diets, and 16 and 18 for low and high-energy series with a mean of 17. On the bases of the coefficients from the Reading Model a broiler breeder hen weighing 3 kg and producing 45 g of egg output per day would need 380, 349 and 423 mg of lysine/d from wheat and maize-based diets, and pooled energy series, respectively. Both the low and high-energy series curves had the same shape, implying there was no interaction between the response to lysine and to energy. Using the calculated 'a' coefficients, because they accounted for maintenance requirements, and assuming an egg contains 8.3 mg lysine/g, the efficiency of utilization of lysine for egg production is estimated as being 0.55, 0.64 and 0.49 for wheat- and maize-based diets, and pooled energy series data, respectively. The efficiency derived for the older flock is lower than the one derived for a younger flock indicating that the efficiency of utilization of the limiting amino acid for egg production declines with age in broiler breeder hens. Broiler breeder hens that were fed maize-based diets were more efficient than those fed on wheat-based diets.

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