N-acetyl-L-cysteine improves the performance of chronic cyclic heat-stressed finisher broilers but has no effect on tissue glutathione levels.

1. It was hypothesised that dietary N-acetyl-L-cysteine (NAC) in feed, as a source of cysteine, could improve the performance of heat-stressed finisher broilers by fostering glutathione (GSH) synthesis. GSH is the most abundant intracellular antioxidant for which the sulphur amino acid cysteine is rate limiting for its synthesis.2. In the first experiment, four levels of NAC: 0, 500, 1000 and 2000 mg/kg were added to a diet with a suboptimal level of sulphur amino acids in the finisher phase. In the second experiment, NAC was compared to other sulphur amino acid sources at equal molar amounts of digestible sulphur amino acids. Birds were allocated to four groups: control, 2000 mg/kg NAC, 1479 mg/kg L-cystine, and 2168 mg/kg Ca-salt of 2-hydroxy-4-(methylthio)butanoic acid. A chronic cyclic heat stress model (temperature was increased to 34°C for 7 h daily) was initiated at 28 d of age.3. In the first experiment, growth performance and feed efficiency in the finisher phase were significantly improved by graded NAC. ADG was 88.9, 92.2, 93.7 and 97.7 g/d, and the feed-to-gain ratio was 2.18, 1.91, 1.85 and 1.81 for the 0, 500, 1000 and 2000 mg/kg NAC treatments, respectively. However, liver and heart GSH levels were not affected by NAC. On d 29, liver gene transcript of cystathionine-beta-synthase like was reduced by NAC, which suggested reduced trans-sulphuration activity. The second experiment showed that L-cystine and Ca-salt of 2-hydroxy-4-(methylthio) butanoic acid were more effective in improving performance than NAC.4. In conclusion, N-acetyl-L-cysteine improved dose-dependently growth and feed efficiency in heat-stressed finishing broilers. However, this was not associated with changes in tissue GSH levels, but more likely worked by sparing methionine and/or NAC's and cysteine's direct antioxidant properties.

Detrimental Effect of Tannin on Growth Performance, Visceras Weight and Blood Biochemistry in Broiler Chickens Reared Under Tropical Area.

Restriction of antibiotic growth promoters (AGP) in Indonesia reduces broiler production due to bacterial diseases. Some poultry farmers have attempted to replace AGP with phytogenic compounds, such as tannin as an in-feed additive. Therefore, this study was carried out to investigate the effects of tannin administration on the production performance, viscera weight, and lipoprotein levels of tropically-raised broiler chickens. Cobb Strain broiler chicks aged one day were used in an experiment with a completely random design, three treatments, and four replicate pens, each containing nine birds. Three dietary treatments were assigned to the birds: basal diet (negative control), basal diet+0.03% Zn Bacitracyn (positive control), and basal diet+0.05% tannin for the starter phase of 1-21 days and the grower phase of 22-42 days, respectively. Tannin supplementation significantly increased the feed conversion ratio in all phases relative to the control group. Tannin supplementation in the diet significantly reduced daily feed intake during the grower phase, final body weight, carcass weight, intestine weight, liver weight, and total visceral weight, compared to the control group. Tannin had lower levels of aspartate aminotransferase but higher levels of low-density lipoprotein and alanine aminotransferase. Tannin addition in broiler diets might not improve growth performance and health. Therefore, it is not suggested as a substitute for AGPs in broiler diets.