No abstract

This study was conducted to relate the performance of broiler chickens fed diets containing growth-promoting antibiotics to changes in the intestinal microbiota. The technique of denaturing gradient gel electrophoresis (DGGE) of amplicons of the region V3 of 16S rDNA was used to characterize the microbiota. Two experiments were conducted, one with broilers raised in battery cages and the other with broilers raised in floor pens. Antibiotics improved the performance of the chickens raised in floor pens only. Avilamycin, bacitracin methylene disalicylate, and enramycin induced changes in the composition of the intestinal bacterial community of the birds in both experiments. The number of bacterial genotypes found in the intestinal tract of chickens was not reduced by the antibiotics supplemented in either environment. However, the changes in the composition of the intestinal bacterial community induced by antibiotics may be related to improvement in growth performance. This was indicated by the suppression of 6 amplicons and the presence of 4 amplicons exclusive to the treatment that had the best performance in the floor pen experiment.

The effects of supplementing canthaxanthin on productive and reproductive aspects of broiler breeders were examined in this study. In total, 360 female pullets and 36 roosters were placed in an open-sided house with 12 pens, each pen with an area of 7.0 m(2) (3.5 × 2.0 m). At 42 wk of age, the breeder hens and roosters were distributed into 2 experimental groups with similar BW and uniformity. From 46 to 66 wk of age, one group received 6 mg/kg of canthaxanthin supplemented in the diet and the other group received the diet without the addition of canthaxanthin (control diet). Body weight was measured every 28 d, the laying rate was calculated weekly, and mortality was evaluated at the end of the study. Twenty-one weekly incubations were performed to evaluate fertility and incubation responses. To evaluate the antioxidant effect of canthaxanthin at different storage times and during the incubation process, eggs from each treatment were subject to thiobarbituric reactive substances analysis. Body weight, mortality, and laying rate were not affected by the inclusion of canthaxanthin in the breeder's diets. An increase in hatchability of total and fertile eggs (P ≤ 0.0001 and P ≤ 0.0003, respectively) in breeders fed canthaxanthin during the experimental period was observed. Canthaxanthin also improved breeder fertility and reduced embryo mortality. This can be attributed to reductions in embryo mortality in the first 48 h of incubation and in the last wk of incubation. No differences were observed in BW and quality of the chicks. A reduction of thiobarbituric reactive substances was observed in yolks from stored hatching eggs produced by breeders fed diets plus canthaxanthin. The same effect was observed in yolks of eggs stored for 4 d and incubated for 7 d. The supplementation of broiler breeder diets with canthaxanthin improved the hatchability rate, fertility, and reduced the presence of thiobarbituric reactive substances in eggs.

Trypsin inhibitors ( TI ) resident in soybeans affects protein utilization. While heat treatment influences residual TI, it simultaneously affects the structure and solubility of the soybean proteins and confounds any response to exogenous proteases. Using purified TI, the effect of exogenous protease to TI can be dissociated from changes in the soybean protein. Thus, the current study was designed to evaluate the growth performance and protein utilization responses of broiler chickens to purified TI and exogenous protease. Soybean meal ( SBM ) was preanalyzed for basal TI (2,996 TIU/g SBM), formulated into nutritionally adequate experimental diets to contain 1,033 TIU/g diet, and purified TI was added at 9,000 TIU/g diet. A total of 320 Cobb-500 broiler chicks were allocated to 4 diets, each with 8 replicate cages and 10 birds per replicate. The experimental diets were arranged as a 2 × 2 factorial with factors being dietary TI (1,033 or 10,033 TIU/g) and exogenous protease (0 or 15,000 PROT/kg). On day 7, 14, and 21 posthatching, protease supplementation improved the BW gain ( P < 0.01) and gain to feed ratio ( P < 0.05) of birds. On day 14 and 21 posthatching, the relative weight of pancreas increased ( P < 0.05) with added TI but was reduced ( P < 0.001) with protease supplementation. Apparent ileal digestibility of all amino acids, except methionine, decreased ( P < 0.001) with added TI but increased ( P < 0.05) with protease supplementation. Jejunal MUC-2 was downregulated ( P < 0.01) and SCL7A-2 was upregulated ( P < 0.05) by protease supplementation. Duodenal trypsin and chymotrypsin activities reduced ( P < 0.05) with added TI but increased (P < 0.01) with protease supplementation. Exogenous protease produced longer villi ( P < 0.05) and deeper crypts ( P < 0.01) in the jejunal tissue. In conclusion, dietary addition of purified TI negatively affects nutrient utilization by broiler chickens. Furthermore, the study showed that the efficacy of the exogenous protease might be independent of dietary TI concentration.

A study was conducted to evaluate the effects of dietary α-amylase and β-xylanase supplementation of corn-soy diets, formulated with or without supplemental phytase, on growth performance, energy utilization, and starch digestibility in broiler chickens. A total of 336 slow-feathering, Cobb × Cobb 500 male broilers were randomly distributed to 6 treatments having 8 replicates of 7 birds each. Birds were fed a common starter diet to d 14 post-hatch (3,050 kcal/kg AMEn, 21.7% CP, 1.05% Ca, and 0.53% nPP). The experimental diets were provided afterwards until d 25. A 2 × 3 factorial arrangement of 2 control diets (basal = corn-soy diet without added phytase or PHY = corn-soy diet formulated with 1,000 phytase units/kg) and 3 carbohydrase supplementations (0, 80 kilo-Novo α-amylase units/kg, or 80 kilo-Novo α-amylase units/kg + 100 fungal β-xylanase units/kg) was used from d 14 to 25. Excreta were collected from 21 to 24 d and all birds were euthanized at 25 d for jejunum and ileum content collection. Samples of feed, excreta, and jejunal and ileal digesta were analyzed for determination of total tract retention and ileal apparent digestibility. No interactions between diet and carbohydrase were observed. Broilers fed diets formulated with phytase or supplemented with amylase + xylanase had higher BW gain (BWG) and lower FCR (P < 0.05) when compared with birds fed diets without carbohydrases. Relative to the basal diet, AMEn was increased (P < 0.01) by 70 kcal/kg and 99 kcal/kg when birds were fed the diet supplemented with amylase and amylase + xylanase, respectively. Starch digestibility in the jejunum and ileum was increased (P < 0.05) by 3.5% and 2.4%, respectively, when birds were fed the diet supplemented with amylase + xylanase. Results from this experiment show that corn-soy diets having phytase and supplemented with amylase and xylanase led to increased growth performance, AMEn, and starch digestibility in broilers. Furthermore, the efficacy of exogenous amylase and xylanase was independent of the presence of microbial phytase.