From the abstract:

The onset of lactation is a critical period in terms of cows' performance, during which significant metabolic changes occur that affect productivity during the whole lactation. There is a great deal of variance between cows in the physiological and metabolic characteristics after calving, which affect the efficiency of food consumption and milk production during lactation. In the preliminary work we examined the transmission of insulin signal in cow's adipose tissue (AT) after calving and found that the AT of half of the tested cows did not respond to insulin. This subset of cows differed in several characteristics from the subgroup of the insulin-responding group; First, those who did not respond to insulin in their AT lost more body weight in the first month after birth, and the decline in body condition after calving was greater. Second, the milk yield and the FCM during the first 100 days were lower in cows who lost a lot of body weight after calving, so there appears to be a link between the responsiveness of the AT to the base of the tail and the weight of the body after calving and milk production. The confirmation of this finding will enable the examination of additional metabolic markers in AT using advanced bioinformatics methods that characterize sub-populations in the dairy cows herd and can serve as a tool for selection of cows that excel in their physiological adaptation to milk production.

Objectives and stages of the study: In the first year of the study, we performed an experiment in which 12 cows participated before calving in the individual feeding barn (Volcani center). Blood samples were taken 3 times a week for concentrations of metabolites and hormones, food intake and production data were collected and the energy balance was calculated. AT biopsies from the caudal base region were taken before and after a glucose tolerance test on days -14 and 10 after birth, in cows that differ in body weight loss after calving. We performed analyzes of concentrations of hormones and metabolites and analyzed the variability between cows in response to calving. In the second year we performed analyzes of blood samples and proteomic analysis of metabolic markers in cow's AT after calving, differentiated by postpartum weight loss. We also analyzed the data of 92 mature cows in the Volcani barn to examine whether the weight loss in each lactation is an internal trait that is repeated, and the link to the fertility performance of the cows at each lactation. In the third year of the study, we performed an experiment with 18 cows in the Volcani barn that examined the association between expression of AT markers in cows after calving by proteomic analysis and metabolic measures and the extent of weight loss after calving...