Effects of reducing dietary amino acid density and stocking density on growth performance, carcass characteristics, meat quality, and occurrence of white striping in broiler chickens

Intermittent dilution of dietary digestible lysine lowers the incidence of white striping by suppressing the growth, lipid synthesis, and muscle damage in broiler chickens

BACKGROUND

White striping (WS) is a myopathy of breast muscle (Pectoralis major) that affects the quality and consumer acceptance of breast fillets of broiler chickens. Previous studies have shown that intermittent dilution of dietary nutrients suppresses the development of WS on the breast muscle of broiler chickens. However, the mechanism by which these interventions reduce the occurrence of WS remains inconclusive. In this study, we adopted intermittent reduction of dietary digestible lysine (dLys) density or metabolizable energy (ME) and amino acid (AA) density using chemical and fatty acid composition of breast fillets, and blood metabolites to understand the mechanism while histopathology and immunohistochemistry of breast muscles were used for confirmation.

RESULTS

Occurrence of WS was lower in broiler chickens fed 85% dLys diets in comparison with other groups. Crude protein and ether extract in breast meat of 85% dLys groups were greater (P < 0.001) and lower (P = 0.010), respectively. Serum concentrations of lipid metabolites and enzymes were lower in broiler chickens fed 85% dLys diets than control group (P < 0.05). Feeding 85% dLys diets had low degree of myodegeneration and necrosis, inflammation, lipid deposition, infiltration of T-lymphocyte (CD3+) and macrophages (Iba-1+), and low expression of heat-shock protein 70 (HSP70) than other groups (P < 0.001).

CONCLUSION

Dilution of dietary dLys to 85% of the required quantities reduces the development of WS in broiler chickens by slowing the growth, lipid synthesis, and muscle damage confirmed by lower extent of histopathological lesions. © 2022 Society of Chemical Industry.

Effects of dietary β-alanine supplementation on growth performance, meat quality, carnosine content, amino acid composition and muscular antioxidant capacity in Chinese indigenous Ningxiang pig

β-alanine has been demonstrated to improve carcass traits and meat quality of animals. However, no research has been found on the effects of dietary β-alanine in the meat quality control of finishing pigs, which are among the research focus. Therefore, this study aimed to evaluate the effects of dietary β-alanine supplementation on growth performance, meat quality, carnosine content, amino acid composition and muscular antioxidant capacity of Chinese indigenous Ningxiang pigs. The treatments contained a basal diet (control, CON) and a basal diet supplemented with 600 mg/kg β-alanine. Each treatment group consisted of five pens, with five pigs per pen. Results showed that compared with CON, supplemental β-alanine did not affect the final body weight, average daily gain, average daily feed intake and the feed-to-gain ratio of pigs. Dietary β-alanine supplementation tended to increase the pH_45 min (p = 0.071) while decreasing the shear force (p = 0.085) and the drip loss (p = 0.091). Moreover, it improved (p < 0.05) the activities of glutathione peroxidase and catalase and lessened (p < 0.05) malondialdehyde concentration. Added β-alanine in diets of finishing pigs could enhance the concentrations of arginine, alanine, and glutamate (p < 0.05) in the longissimus dorsi muscle and tended to raise the levels of cysteine, glycine and anserine (p = 0.060, p = 0.098 and p = 0.091 respectively). Taken together, our results showed that dietary β-alanine supplementation contributed to the improvement of the carcass traits, meat quality and anserine content, the amelioration of muscle antioxidant capacity and the regulation of amino acid composition in Chinese indigenous Ningxiang pigs.

Carcass characteristics, meat quality, nutrient composition, serum biochemistry and oxidant/antioxidant status in white striping-affected broiler chickens fed diets based on corn-soybean meal

1. Effects of the incidence of white striping (WS) in relation to carcass weights and yields, breast meat quality and composition, serum biochemistry and oxidant/antioxidant status of breast meat in broiler chickens were investigated.

2. The study consisted of 180, one-d-old male broiler chickens fed corn-soybean meal-based starter, grower, finisher and withdrawal diets identical to commercial chicken diets. On d 49, all the birds were slaughtered and breast fillets were visually scored for the incidence of WS. Breast meat and blood samples were collected and categorised based on the presence or absence of WS.

3. The study revealed greater slaughter weight, carcass and breast fillet weights and yields, lower pH_u and higher cooking loss of breast meat with WS lesions (P<0.05). WS-affected breast fillets had greater fat and lower crude protein contents in comparison with normal meat (P<0.001). Serum creatine kinase levels were greater in broilers with WS (P=0.011), whereas oxidant/antioxidant status of breast meat remained unaffected.

4. Taken together, the presence of WS on breast muscle altered the quality and nutrient composition of breast fillets and serum creatine kinase levels in broiler chickens fed diets based on corn-soybean meal. Nevertheless, WS was more common in heavier broilers having higher breast weight and yield.

Environmental Stress in Chickens and the Potential Effectiveness of Dietary Vitamin Supplementation

Environmental stressors can promote the vulnerability of animals to infections; it is therefore, essential to understand how stressors affect the immune system, the adaptive capacity of animals to respond, and effective techniques in managing stress. This review highlights scientific evidence regarding environmental stress challenge models and the potential effectiveness of vitamin supplementation. The major environmental stressors discussed are heat and cold stress, feed restriction, stocking density, and pollutants. Much work has been done to identify the effects of environmental stress in broilers and layers, while few involved other types of poultry. Studies indicated that chickens' performance, health, and welfare are compromised when challenged with environmental stress. These stressors result in physiological alterations, behavioral changes, decreased egg and meat quality, tissue and intestinal damage, and high mortalities. The application of vitamins with other nutritional approaches can help in combating these environmental stressors in chickens. Poultry birds do not synthesize sufficient vitamins during stressful periods. It is therefore suggested that chicken diets are supplemented with vitamins when subjected to environmental stress. Combination of vitamins are considered more efficient than the use of individual vitamins in alleviating environmental stress in chickens.

Interactive effects of dietary amino acid density and environmental temperature on growth performance and expression of selected amino acid transporters, water channels, and stress-related transcripts

Exposure to heat stress (HS) is one of the challenges facing the broiler industry worldwide. Various nutritional strategies have been suggested, such as altering dietary concentrations of some nutrients. Thus, we evaluated feeding different amino acid (AA) densities on live performance, Pectoralis (P.) muscles, and expression of selected AA transporters, water channels, and stress-related transcripts in a fast-growing broiler strain. Ross 308 chicks (n = 576) were randomly assigned to 4 dietary treatments (24 reps, 6 chicks per rep), differing in AA density (110, 100, 90, and 80% of a breeder's AA specifications). During 24 to 36 days of age, half of the birds were kept at a thermoneutral (TN) temperature of 20°C, whereas the other half were subjected to HS at 32° C for 8 h daily, making the treatment design a 4 × 2. The results revealed no interaction between housing temperature and AA density on growth performance or P. muscles weights. Feeding 80% AAs depressed BWG, FCR, and P. muscles at 36 d (P < 0.001). There was an interaction (P < 0.001) between AA density and temperature on the expression of all examined genes. Reducing the AA density beyond 100% upregulated the expression of AA transporter (CAT1, B⁰AT, b^0,+AT, SNAT1, LAT1), HSP70, HSP90, glucocorticoid receptor (GR), and AQP3 in the TN birds’ jejunum. Whereas in the HS birds, inconsistent expressions were observed in the jejunum, of which CAT1, B⁰AT, and LAT1 were markedly downregulated as AA density was reduced. In P. major of TN birds, reducing AA density resulted in upregulating the expression of all AA transporters, HSP70, GR, and AQP1, while downregulating HSP90 and AQP9. In contrast, AA reduction markedly downregulated CAT1, B⁰AT, and LAT1 in the P. major of HS birds. These findings indicate that the dietary AA level alters the expression of various genes involved in AA uptake, protein folding, and water transport. The magnitude of alteration is also dependent on the housing temperature. Furthermore, the results highlight the importance of adequate AA nutrition for fast-growing chickens under HS.