Influence of composition and storage conditions on diet quality and productivity of broiler chickens.

Abstract

Two experiments were conducted to assess the effects of varying storage temperature and relative humidity (RH) on feed quality and nutritive value of such diets when fed to broiler chickens. The diets used in experiment two were higher in lipids than those used in experiment one. All other features of the diets tested lin the two experiments were identical. Diets were also supplemented with or without inhibitor during storage. Prior to feeding, the diets were also supplemented with or without a fungal detoxifier. Laboratory analysis showed that the diets contained Aspergillus spp, Penicillium spp and Fusarium spp with no toxins identified. Storage at high temperature (30°C) over one month increased dry matter (DM) content by about 1%, which was accompanied, by an increase of between 3.5-5% in crude protein (CP) as well as 3-4% fat (Experiments One and Two). After two months of storage, high storage temperature decreased DM content by about 1.6%, which resulted in a decrease in the levels of CP and fat in most of the diets (Exp. One). In experiment two, an increase of about 0.5% in the DM content was observed in diets stored at low temperature (15°C) followed by an increase of about 3% in fat content. Variable changes were observed in the micromineral contents. In experiment one, there was an increase in Fe and Zn content after one month, followed by variable decreases in the second month, while in experiment two, there was a decline in the concentrations of Fe, Zn and Cu by about 21, 16 and 26%, respectively throughout the storage period. Rancidity developed with time in all the diets but there was a tremendous reduction (p<0.001) in the rate of oxidation by 15% and 20% with supplemental inhibitor (antioxidant) in experiment one and two, respectively but no reduction in free fatty acid (FFA) content. High storage temperature (30°C) and RH (80%) increased FFA content from 3.5 to about 15% in experiment one (p<O.OOl, R2 = 0.73) and to about 17% in experiment two (p<0.001, R2 = 0.84) during the storage period of 60 days. Storage at low temperature (l5°C) and RH (50%) similarly decreased peroxide value (Pv) by about 16% in experiment one (p<O.OOl, R2 = 0.84) and in experiment two by 25% (p<0.001, R2 = 0.89) over time. Inclusion of the antioxidant decreased the concentration of Pv by about 10% in experiment one (p<O.OOl) and by 20% in experiment two (p<0.001). Feed intake of birds was unaffected. Storage temperature did not influence body weight (Experiment one) but in experiment two, high feed storage temperature decreased (p<0.001) body weight by about 3%. Supplementation of diets with the inhibitor improved (p<0.001) body weight only in experiment two. Further supplementation with the detoxifier markedly improved (p<0.01) body weight in both experiments. Low RH increased feed conversion efficiency (FCE) by 6% in experiment one (p<O.OOl) and in experiment two (p<0.01). Improvements (p<0.05) in FCE were observed on diets stored at low temperature in experiment one and with further supplemental detoxifier, (p<O.Ol). No significant differences were noticeable in body weight or in FCE in experiment two. Mortality was unaffected by treatments. The relative liver weight of birds was markedly reduced as a result of low storage temperature and RH. Dietary supplemental inhibitor or detoxifier reduced (p<0.001) liver weight between 8 and 10% in both experiments. On the other hand, heart weight was unaffected by storage conditions. However, in experiments one and two, the detoxifier caused a reduction (p<O.OOl) of 11% in heart weight unlike the inhibitor. Proventriculus weight was reduced (p<0.05) by feeding diets stored at low RH in experiment one by 4%, while no effects were observed in experiment two. Both studies showed no changes in the proventriculus weight when the inhibitor and detoxifier were added. Storage at low temperature and RH in experiment one caused a significant decrease (p<0.01) of 4% gizzard weight unlike in experiment two. The inhibitor reduced gizzard weight by about 7% in experiment one (p<0.001) and experiment two (p<0.05). Further supplemental detoxifier decreased gizzard weight in experiment one (p<0.01) and two by 6% (p<0.001). Spleen weight was not affected by any of the treatments except in experiment one, where the weight of the spleen was reduced (p<0.05) by detoxifier from 0.13- 0.12g/100g body weight (7.7%). Storage conditions did not affect the biochemistry of serum obtained from the chicks in experiment one, while in experiment two, high temperature decreased (p<0.05) total phosphorus from 3.4-2.9 mmoVI and high RH decreased (p<0.05) serum protein (3.3-3.1g/100ml) as well as globulin (1.74-1.58g/100ml). Supplemental inhibitor increased serum protein (p<0.05)' by 6% and globulin (p<0.01) by about 12% (experiment one) and albumin (p<0.05) by 7% (experiment two). Further supplementation with the detoxifier increased (p<O.OOl) phosphorus by about 3.5% (experiment one), while in the second experiment, serum phosphorus and albumin were increased (p<0.05). No signs of 'rubbery' bones were observed in birds in these studies. Furthermore, there were no observable changes as a result of storage conditions or addition of inhibitor in diets. However, it was observed that supplemental detoxifier increased bone ash from an average of 51.2 to 51.8% in experiment one and in experiment two, 50.6-52.5%. The results of the studies indicated a development of feed contamination (quality loss) over time with tremendous rate of increase observed in diets devoid of the preservatives (antioxidant and mold inhibitor). Further supplementation of the detoxifier markedly improved productivity as well as some of the serum biochemical parameters measured.