This experiment was conducted to investigate the effects of marigold flavonoids on growth perform-ance,nutrient apparent digestibility,serum antioxidant and immune indices of heat stressed beef cattle.Sixty healthy Simmental bulls without disease were randomly divided into 4 groups with 15 bulls per group according to the principle of similar body weight[(518.32±25.59)kg].The control group(M0 group)was fed a total mixed ration(TMR),and the experimental groups were fed the TMR supplemented with 3(M3 group),6(M6 group)and 9 g/(d·head)(M9 group)marigold flavonoids,respectively.The experiment lasted for a total of 67 days,including 7 days of pre-feeding and 60 days of formal feeding.The average temperature and humidity index was 80.06 during the experiment,and beef cattle were in a state of moderate heat stress.The results showed as follows:1)compared with M0 group,the respiratory rate of M6 group on day 40 was sig-nificantly decreased(P＜0.05).2)Compared with M0 group,the average daily gain(ADG)of M3 and M6 groups was significantly increased(P＜0.05),and the ratio of feed to gain(F/G)was significantly decreased(P＜0.05).3)On day 60,compared with M0 group,the dry matter(DM)apparent digestibility of M6 and M9 groups was significantly increased(P=0.05),the crude protein(CP)apparent digestibility of M6 group was significantly increased(P＜0.05),and the calcium(Ca)and phosphorus(P)apparent digestibility of M3 and M6 groups was significantly increased(P≤0.05).4)On day 60,compared with M0 group,the serum malondialdehyde(MDA)content of M3 and M6 groups was significantly decreased(P＜0.05),and the serum total antioxidant capacity(T-AOC)of M6 group was significantly increased(P=0.05).5)On day 60,com-pared with M0 group,the contents of immunoglobulin A(IgA)and interleukin-2(IL-2)in serum of M3,M6 and M9 groups were significantly increased(P＜0.05),and the serum tumor necrosis factor-α(TNF-α)con-tent of M6 group was significantly decreased(P＜0.05).In conclusion,dietary supplementation of marigold flavonoids can effectively reduce the respiratory rate of heat-stressed beef cattle,improve growth performance,enhance the body antioxidant capacity and immune function,and the supplementation of 6 g/(d·head)mari-gold flavonoids has the best effect.[Chinese Journal of Animal Nutrition,2024,36(9):5736-5747]
维普
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