Response of growth performance and cecum microbial community to cyclic heat stress in broilers.

Heat stress (HS) can affect growth performance through alterations in specific gut microbiota, which greatly threatens poultry production. How HS affects the mechanisms of microbial changes in the poultry cecum and the complex interactions between cecal microbial changes and growth performance have not yet been well evaluated. This study was conducted to examine the changes in growth performance and cecal microbiotal community in cyclic heat stress (CHS)-treated broilers. A total of 200 twenty-eight-day-old female Arbor Acres (AA) broilers were equally allotted into neutral ambient temperature group (TN group, 24 ± 1°C, 24 h/day) and CHS group (33 ± 1°C, 8 h/day) with five replicates of 10 broilers each, respectively. Growth performance, cecum microbial diversity, flora composition, and community structure were analyzed on days 35 and 42. The decreased average daily feed intake (ADFI), average daily gain (ADG), and the increased feed/gain ratio (F:G) were observed in heat-stressed broilers on days 35 and 42. The alpha and beta diversity index had no significant changes at the two experimental periods (P > 0.05). At the genus level, CHS significantly increased the relative abundance of Enterococcus at 42 days (P < 0.05). Based on the analysis of linear effect size feature selection, CHS made an enriched Reyranella and a reduced Romboutsia and Ruminiclostridium at 35 days of age (P < 0.05). CHS made an enriched Weissella and Enterococcus at 42 days of age (P < 0.05). The present study revealed that CHS reduces broiler growth performance and alters the microbial community of the cecum microbiota and the abundance of species. These findings are of critical importance to alleviate the negative effects of CHS on broiler chickens' growth performance by maintaining gut microbial balance.

Effect of dietary supplemental vitamin C and betaine on the growth performance, humoral immunity, immune organ index, and antioxidant status of broilers under heat stress.

Heat stress (HS) has become one of the important factors affecting the development of animal husbandry. The purpose of this experiment was to investigate whether vitamin C (Vc) and betaine (Bet) improve immune organ index and humoral immunity by enhancing the antioxidant status of immune organs, thus protecting broilers from HS-induced injuries. A total of 200 28-day-old Ross 308 broilers were randomly assigned into 5 groups (n = 4 replicates/group, 10 broilers/replicate) which were reared at different ambient temperatures (24 ± 1°C or 33 ± 1°C). The control group fed basal diet, while high-temperature groups were either fed a basal diet (HS group) or a basal diet supplemented with 250-mg Vc/kg diet (HSVc group), 1000-mg Bet/kg diet (HSBet group), and 250-mg Vc plus 1000 mg Bet/kg diet (HSVcBet group), respectively. On day 42, growth performance, humoral immune function, immune organ index, and antioxidant capacity were measured. HS reduced the productive performance of broilers, antibody potency against the Newcastle disease virus (NDV) and sheep red blood cells (SRBC), indices of thymus and bursa, and antioxidant capacity of immune organs. Adding Vc alone or in combination with Bet improved performance, NDV and SRBC antibody potency, thymus and bursa indices, and antioxidant capacity of immune organs in heat-stressed broilers, with the most effective being combination. In summary, HS reduces the antioxidant capacity and immune organ development status of broiler immune organs. Vc and/or Bet can improve the development of immune organs and restore part of the production performance by regulating the antioxidant status of immune organs, among which the combined addition of Vc and Bet has the best effect.