Browsing by Author "Van Ryssen, Jannes Bernardus Jansen."

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Aspects of the copper-molybdenum-sulphur interactions in sheep.
(1979) Van Ryssen, Jannes Bernardus Jansen.; Stielau, Werner Johannes.
No abstract available.
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.
The effect of form of nitrogen on the efficiency of protein synthesis by rumen bacteria in continuous culture.
(1991) Kernick, Brian Louis.; Van Ryssen, Jannes Bernardus Jansen.; Mackie, Roderick Ian.
The aim of this study was to examine the effect of the form of nitrogen available to mixed rumen bacteria on the efficiency of microbial protein synthesis. A novel, solid substrate, continuous culture fermentor which proved capable of maintaining representative populations of mixed rumen bacteria under steady state conditions, at predetermined growth rates was developed for the study. A series of experiments wherein maize straw, alkaline hydrogen peroxide-treated wheat straw, rye grass or a mixture of maize straw and maize starch were used as substrates were performed in the fermentor. The effect of supplementing these substrates with different forms of nitrogen, namely peptides in the form of a partial hydrolysate of casein, or ammonium salts alone or ammonium salts plus branched-chain volatile fatty acids, on digestion of the substrate and microbial protein synthesis was investigated. Supplementation of maize straw with peptides increased microbial protein synthesis, however this was only significant (P<0.05) when the availability of nitrogen and specific growth rate of the bacteria were not limiting. Organic Matter digestion was not affected by peptide supplementation. Replacement of casein hydrolysate with sunflower oilcake as a source of amino acid nitrogen further increased microbial protein synthesis. The form of nitrogen supplementation did not affect the digestion of constituent cell wall monosaccharides of maize straw. Supplementation of alkaline hydrogen peroxide-treated wheat straw with either branched-chain volatile fatty acids or casein hydrolysate increased the synthesis of microbial protein significantly (P<0.05) and caused a slight, but insignificant increase in the digestion of cellulose-glucose. The efficiency of microbial protein synthesis on rye grass was high, relative to the other substrates, and unaffected by the supplementation of either branched-chain volatile fatty acids or peptides. On media containing high levels of starch, microbial protein synthesis as well as Organic Matter digestion were increased by peptide supplementation, but these differences were only significant (P<0.05) when the bacteria were growing at a high specific growth rate. In all of these experiments, peptide supplementation was accompanied by extensive degradation and deamination of amino acids which offset any increase in microbial protein synthesis. Peptide supplementation therefore resulted in far less efficient overall utilization of protein.
Theoretical and applied aspects of voluntary feed intake by ruminants, with special reference to the kinetics of rumen digestion.
(1994) Pienaar, Johannes Petrus.; Van Ryssen, Jannes Bernardus Jansen.
The aim of these studies was to examine the factors which determine voluntary feed intake and feed quality in ruminants. In the first experiments, the concepts of ruminal digestion kinetics were conceptualised and measured in animals. These concepts were applied practically in feed evaluation studies which followed. In vivo studies on alkali treated wheat straw explained why voluntary intake of ruminants increased when roughages are treated with alkali. The effect of washing the treated feed to remove excess sodium was also studied. The explanation was found in terms of ruminal digestion kinetics, showing that the mean rate of digestion was not changed, but chemical treatment improved the potential digestibility, thereby increasing the active pool size in the rumen which resulted in a faster clearance rate from the rumen. A study of the effect of starch fermentation on the kinetics of roughage fermentation in the rumen, revealed that the fermentation of different diets were affected in a different manner. The paramount factor was found to be a reduced rate of forage fermentation in the presence of starch fermentation in the rumen. A study of Pennisetum clandestinum revealed the reasons why animal performance on kikuyu pasture is often lower than what would be expected from the digestibility and chemical composition of the material. It was shown that a high soluble nitrogen content of the material was the most likely reason for low voluntary intakes, low ruminal fill and therefore poor animal performance on lush kikuyu pasture. A method was developed by which the concepts of ruminal digestion kinetics (MRT method) are used to determine voluntary feed intake with grazing animals. The method gave a mean intake that was similar to the mean obtained when intake was calculated from faecal collections, but had the advantage of a clearer pattern of intake. The accuracy obtained when using the MRT method to estimate voluntary feed intake was confirmed in a second experiment where actual intakes were known, and predicted intake was very close to actual intake. Indirect methods were developed by which two important determinants of voluntary intakes, i.e. rate and extent of digestion may be estimated. The Tilley & Terry in vitro method was adapted to allow the estimation of fermentation rates from rates of gas production. Digestion rates obtained with in vitro gas production agreed well with in sacco estimates. In vivo digestion rates were much slower than those obtained in vitro or in sacco. This discrepancy is yet unexplained, and is in contrast with the results of a previous experiment where in sacco and in vivo results were in good agreement. Increasing the mean particle size of the fennenting forages resulted in a small but statistically significant decrease in fennentation rate. Stirring the fennentation vessels did not have any positive effect on fennentation rate. Total volume of gas produced was not a good indicator of in vitro digestibility because gas production measures ruminal digestion, while in vitro digestibility includes both a ruminal and an acid pepsin phase. The rate of in vitro gas production, as measured by pressure changes in the fennentation vessels, is a practical method that was easily automated by using a data logger. The automated measurement of rate and ex'tent of digestion allows their inclusion into routine analyses for feed evaluation and the results obtained so far indicate that the system is sufficiently accurate to give useful estimates of voluntary feed intake and animal production.
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.