Besides having a beneficial effect on milk production, live yeast have also shown to have a possible effect on the immune system in cows kept in heat stressed conditions.
Heat stress is a growing concern for the dairy industry due to its adverse affects on productivity, health, reproduction, and therefore the profitability of the dairy operation. Earlier studies showed that yeast supplementation improved lactation performance of dairy cows suffering heat stress. However, less information exists concerning the effects of a yeast supplement on immune function and insulin sensitivity in transition dairy cows during the hot months of summer. Therefore, the objective of this study was to examine how a yeast supplement would affect milk production, blood metabolites, insulin sensitivity traits, and immunological measures of dairy cows during hot months of summer.
In the May edition of Animal Feed Science and Technology, a research team from Iran and South Korea write about their study to determine effects of feeding a live yeast supplement on the productive performance, blood metabolic profile, the immune function, and insulin sensitivity traits of transition dairy cows during the hot months of summer. From 21 d before expected date of calving until d 60 postpartum, 2 groups of multiparous Holstein cows (6 cows per treatment) were fed a diet without or with a live yeast supplement (4g yeast/d/head). The cell-mediated immune and humoral responses were established through phytohemagglutinin challenge and ovalbumin immunisation, respectively.
It was shown that prepartum dry matter intake was greater in yeast-fed cows; however, this difference disappeared after parturition. Cows receiving a yeast supplement produced more milk (+1.40 kg/d) and had greater concentrations of milk fat and total solid than those receiving no yeast. Loss of body condition score from calving to d 21 postpartum tended to be lower in yeast-fed cows than control cows. Yeast supplementation had no effect on the response variables to the glucose tolerance test. Plasma concentration of Hsp70 was also lower on d 14 and 28 after parturition in yeast-fed cows. Yeast supplementation enhanced cellular immune function; however, it had no effect on immunoglobulin G secretion against ovalbumin immunisation. Overall, live yeast supplementation benefited milk production and milk composition, lowered plasma level of Hsp70, and enhanced the lymphocyte proliferative response in transition dairy cows, which may suggest an immunomodulatory effect of yeast supplement.