Avaliação produtiva e fisiológica de vacas leiteiras sob estresse calórico suplementadas com aditivo imunomodulador e leveduras vivas

Abstract

Due to the selection for high milk production, the sensitivity of dairy cows to heat stress was increased, since the higher production increases the intake of digestible nutrients and the production of metabolic heat. The objective of this work was to compare the responses of two additives on the productive and physiological efficiency in lactating dairy cows in the summer. The experiment was carried out on a dairy farm in the municipality of Cruz Alta - Rio Grande do Sul, between January and March 2019, totaling 42 days of the experiment. Three hundred fifty lactating Holstein cows were used, all multiparous, allocated in a compost barn system, and divided into two lots. Lot 1- 200 cows (high production, average 35 kg of milk / day) and lot 2- 150 cows (average production, 27 kg of milk per day). The cows were distributed in a crossover design where they underwent 2 treatments. The additives used were: addition of live yeast (LVLevumilk® 18 grams / cow / day) and addition of immunomodulator (OMN-OmniGen-AF® 50 grams / cow / day). It was observed that the animals both in the morning and in the afternoon were exposed to temperature and humidity indexes> 68 that characterize thermal stress. The OMN increased the consumption of dry matter and organic matter, which did not happen with the LV, that showed a reduction in consumption, indicating better conversion, greater efficiency, due to the greater milk production and better use of nutrients proved by the results of feces evaluation, because the LV showed lower concentrations of fecal starch and organic matter in relation to the OMN. Cows supplemented with LV showed higher milk production, corrected milk production and fat production, urea nitrogen concentrations in milk, and lower somatic cell counts compared to those supplemented with OMN. The cows supplemented with LV had lower rectal and skin temperature, higher concentration of plasma glucose and urea nitrogen in the serum compared to the others. Supplementation of OMN is not more efficient in productive performance than supplementation of LV in diets of lactating dairy cows with heat stress.