Milk yield and genome-wide expression profiling in mammary gland of beef primiparous cows in response to the dietary management during the pre- and post-weaning periods

Dervishi, E. ;Blanco, M. ;Rodriguez Sanchez, J.A. ;Sanz, A. ;Calvo, J.H. ;Casasus, I. 2017. Milk yield and genome-wide expression profiling in mammary gland of beef primiparous cows in response to the dietary management during the pre- and post-weaning periods. Journal of Animal Science, DOI: 10.2527/jas2017.1736

Accelerated growth programs during pre-pubertal periods have been promoted to advance the first calving of beef heifers. The objectives of the present study were to evaluate nutrition-induced changes on first lactation milk yield and composition and in gene expression of the mammary gland in Parda de Montaña primiparous cows. Female calves (n=16) were involved in a 2 x 2 factorial experiment. In the pre-weaning period (PRE-W, 0-6 mo), female calves were either creep-fed or fed only on their dam’s milk (Creep vs. Control). In the post-weaning period (POST-W, 6-15 mo), heifers received either a high (91.7 MJ/d) or a moderate energy diet (79.3 MJ/d) (High vs. Moderate). All the heifers were managed together from breeding (15 mo) to the end of their first lactation (32 mo). Animal performance, milk production and quantity during the first lactation, plasma glucose, IGF-I and leptin concentrations, and RNA samples from mammary gland at the end of the first lactation of the primiparous cows (32 mo) were analyzed. The BW and ADG of the primiparous cow during its first lactation were not different among treatments; however, creep feeding during PRE-W reduced milk production (P < 0.01), milk crude protein, crude fat, lactose, non-fat-solids casein content throughout lactation, and increased somatic cell count (SCC) in the third (P < 0.05) and fourth mo of lactation (P < 0.10). The energy level during the POST-W period had no effect on milk production and quality. Gene expression in mammary gland was affected by the diet in the PRE-W and POST-W periods, with PRE-W diet having the greatest impact. Creep feeding during the PRE-W period resulted in up–regulation of genes related with immune response and chemokine activity, suggesting that these animals might be in a compromised immune status. Thus, this strategy would not be recommendable; meanwhile increasing the energy level in the diet during the POST-W period would be recommendable as it had no deleterious effects on milk yield and compositio