Effects of an immunomodulatory feed additive on feed intake behavior, skin temperature, and milk yield in dairy cows during the hot season

Abstract

Heat stressing conditions alter behavior and physiology which results in impaired performance of dairy cows. The objective of this study was to evaluate the effect of an immunomodulatory additive on feed intake, behavior, physiological parameters, and productivity of dairy cows during heat stress. Forty-two Holstein cows (610 ± 77.5 kg body weight, 28.2 ± 4.12 kg/d milk yield, and 179 ± 90 days in milk) were used in a complete block randomized design to evaluate the following treatments: Control (CON): basal diet without immunomodulatory additive; and OmniGen-AF (OMN): basal diet plus 56 g/d of OmniGen-AF (Phibro Animal Health, Teaneck, NJ, USA) fed during 6 wks. Throughout the trial, the air temperature, relative humidity, and temperature-humidity index averaged 25.9 ± 1.53 ºC, 68.1 ± 7.67 %, and 74.7 ± 2.17, respectively. Cows fed OMN showed increased dry matter intake, fat-corrected milk production, and milk concentrations of fat and protein compared to CON. OMN tended to increase milk yield and body condition score. OmniGen-AF increased serum glucose concentration and had no effect on feed intake behavior, feed particle sorting index, or physiological parameters (heart rate, respiration rate, and rectal temperature). OMN decreased or tended to decrease the surface temperature of the rumen region of cows throughout the day. Thus, OmniGen-AF improves feed intake, body condition score, fat-corrected milk yield, and milk solids of dairy cows under heat-stress conditions.