Effects of Mechanical Ventilation and Water Spraying on Growth Performance,Apparent Nutrient Digestibility,Rumen Fermentation Parameters and Serum Indexes of Heat-Stressed Beef Cattle
This experiment was to investigate the effects of mechanical ventilation and water spraying on growth performance,apparent nutrient digestibility,rumen fermentation parameters and serum indexes of heat-stressed beef cattle.Thirty-two Simmental crossbred bulls aged about 12 months with body weight of(420.22±46.67)kg were randomly divided into 2 groups,they were control group(CON group)and mechanical venti-lation and water spraying group(MVWS group),with 16 replicates per group and 1 cattle per replicate.Beef cattle in the two groups were exposed to mild or moderate heat stress environment most of the time during the experiment.The cattle barn of the MVWS group was equipped with mechanical ventilation and water spraying,while no treatment was done in the CON group.The experiment lasted for 45 days,with a pre-test period of 15 days and a formal test period of 30 days.The results showed as follows:1)compared with the CON group,the respiratory rate(RR)and rectal temperature(RT)of the beef cattle in the MVWS group were extremely significantly reduced(P＜0.01).2)Compared with the CON group,the growth performance and nutrient ap-parent digestibility of beef cattle in the MVWS group had no significant changes(P＞0.05),however,the av-erage daily gain(P=0.089)and dry matter intake(P=0.075)showed a significant increase trend.3)Com-pared with the CON group,the beef cattle in the MVWS group had an extremely significant increase in rumen fluid pH(P＜0.01),and had a significant increase in the concentration of butyrate and acetate/propionate(A/P)ratio(P＜0.05).4)Compared with the CON group,the contents of total cholesterol(TCHO)and cortisol(CORT),alanine aminotransferase(ALT)activity in the serum of beef cattle in the MVWS group were ex-tremely significantly decreased(P＜0.01),and the triglyceride(TG)content was significantly decreased(P＜0.05),while the high-density lipoprotein(HDL)content was significantly increased(P＜0.05).5)Com-pared with the CON group,the activities of superoxide dismutase(SOD)and glutathione peroxidase(GSH-Px)and total antioxidant capacity(T-AOC)in the serum of beef cattle in the MVWS group were extremely significantly increased(P＜0.01),while the content of malondialdehyde(MDA)was extremely significantly decreased(P＜0.01).6)Compared with the CON group,the contents of tumor necrosis factor-a(TNF-a),interleukin-1β(IL-1β)and interleukin-6(IL-6)in the serum of beef cattle in the MVWS group were ex-tremely significantly decreased(P＜0.01),while the content of immunoglobulin A(IgA)was extremely sig-nificantly increased(P＜0.01),and the content of immunoglobulin G(IgG)was significantly increased(P＜0.05).In conclusion,under the heat stress conditions,mechanical ventilation and water spraying in cattle barn can reduce the rectal temperature and respiratory rate of beef cattle,increase the contents of immunoglobulins and antioxidant level in the serum,reduce the accumulation of free radicals in the body,and effectively allevi-ate the negative effects of heat stress on the physiological and immune function and antioxidant ability of beef cattle.[Chinese Journal of Animal Nutrition,2024,36(7):4388-4399]
heat stressbeef cattlemechanical ventilation and water sprayingantioxidantimmune
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