Manipulating the Performance and Oxidative Responses of Dairy Cattle Under Long-term Environmental Heat Stress Upon Zinc-Methionine Complex Dietary Inclusion

Dairy cows are susceptible to heat stress due to levels of milk production and feed intake. Dietary supplemental amino acids, particularly rate-limiting amino acids e.g., methionine (Met), may alleviate the potential negative consequences. Zinc (Zn) is beneficial to the immune system and mammary gland development during heat stress. We investigated the impact of a source of rumen-protected Zn-Met complex (Loprotin, Kaesler Nutrition GmbH, Cuxhaven, Germany) in high producing Holstein cows during a long-term environmental heat stress period. Sixty-two multiparous Holstein lactating cows were allocated in a completely randomized design to 1 of 2 dietary treatments as basal diet without (control) or with supplemental Zn-Met complex (RPZM) at 0.131% of diet DM. Cows in the RPZM group had higher energy-corrected milk as well as milk fat and protein concentration. Zn-Met complex supplemented cows had lower haptoglobin and IL-1B concentration compared with the control. RPZM supplementation resulted in better oxidative status, indicated by higher total antioxidant status and lower malondialdehyde concentrations. Enhanced performance of animals upon Zn-Met complex supplementation could be partly the result of improved oxidative and immune status. Data generated herein could develop novel feeding concepts, i.e., particular feed additives, which can be practically implemented to maintain animal’s productivity and longevity during periods of heat stress.