Effect of coccidia challenge and natural betaine supplementation on performance, nutrient utilization, and intestinal lesion scores of broiler chickens fed suboptimal level of dietary methionine
The aim of the present experiment was to examine the effect of coccidia challenge and natural betaine supplementation on performance, nutrient utilization, and intestinal lesion scores of broiler chickens fed suboptimal level of dietary methionine. The experimental design was a 2 x 2 factorial arrangement of treatments evaluating two levels of betaine supplementation (0 and 960 g betaine/t of feed) without or with coccidia challenge. Each treatment was fed to 8 cages of 8 male broilers (Ross 308) for 1 to 21d. On d 14, birds in the 2 challenged groups received mixed inocula of Eimeria species from a recent field isolate, containing approximately 180,000 E. acervulina, 6,000 E. maxima, and 18,000 E. tenella oocysts. At 21d, digesta from the terminal ileum was collected for the determination of dry matter, energy, nitrogen, amino acids, starch, fat, and ash digestibilities. Lesion scores in the different segments of the small intestine were also measured on d 21. Performance and nutrient digestibility data were analyzed by two way ANOVA. Lesion score data were analyzed using Pearson chi square test to identify significant differences between treatments. Orthogonal polynomial contrasts were used to assess the significance of linear or quadratic models to describe the response in the dependent variable to total lesion scores. Coccidia challenge reduced (P 0.0001) the weight gain and feed intake, and increased (P 0.0001) the feed conversion ratio. Betaine supplementation had no effect (P 0.05) on the weight gain or feed intake, but lowered (P 0.05) the feed conversion ratio. No interaction (P 0.05) between coccidia challenge and betaine supplementation was observed for performance parameters. Betaine supplementation increased (P 0.05) the digestibility of dry matter, nitrogen, energy, fat, and amino acids only in birds challenged with coccidia as indicated by the significant interaction (P 0.0001) between betaine supplementation and coccidia challenge. The main effect of coccidia challenge reduced (P 0.05) starch digestibility. Betaine supplementation improved (P 0.05) starch digestibility regardless of the coccidia challenge. For each unit increase in the total lesion score, there was a linear (P 0.001) decrease in digestibility of mean amino acids, starch, and fat by 3.8, 3.4 and 16% respectively. Increasing total lesion scores resulted in a quadratic (P 0.05) decrease in dry matter digestibility and ileal digestible energy. No lesions were found in the intestine or ceca of the unchallenged treatments. In the challenged treatments, betaine supplementation reduced (P 0.01) the lesion scores at the duodenum, lower jejunum, and total lesion scores compared to the treatment without supplements. In conclusion, coccidia challenge lowered the digestibility of energy and nutrients and increased the feed conversion ratio of broilers. However, betaine supplementation reduced the impact of coccidia challenge and positively affected nutrient digestibility and the feed conversion ratio.
Poultry science