Metabolic status of crossbreed F1 Holstein x Gyr dairy cows during the transition period in two different seasons in Brazil

Crossbreed F-1 Holstein x Gyr cows are proving to be a good alternative to pure Holstein for milk production under tropical conditions. In order to further assess the characteristics of these cattle, we focused on clarifying the metabolic pattern of F-1 Holstein x Gyr dairy cows during the most critical phase in the lactation cycle, the transition period, and compared their performance in two seasons. Blood samples were collected from 15 cows during summer (January to April) and from 13 cows during winter (May to August), beginning 3 weeks prior to the estimated calving date until 30 days post-calving. We found that the season had a considerable influence on the metabolic status of the cattle. With the exception of aminotransferase, non-esterified fatty acids (NEFA), and beta-hydroxybutyrate (BHB), which showed no seasonal variation, all evaluated metabolites showed a different pattern between summer and winter. Liver functions were enhanced during the postpartum period, with increased liver enzyme activity and increased concentrations of cholesterol and BHB being recorded. During this period, the cows had a negative energy balance and a relatively high number of animals experienced subclinical ketosis and had high NEFA concentrations. Overall, we found that the metabolic profile of cows differed substantially between summer and winter, particularly in response to the different environmental and management conditions. Despite these differences, however, the average milk production of crossbreed 1/2 Holstein 1/2 Gyr dairy cows was similar in both seasons, indicating that this crossbreed of daily cows is a good option for milk production in tropical environments.