Milk yield and genomewide expression profiling in the mammary gland of beef primiparous cows in response to the dietary management during the pre- and postweaning periods1

Abstract

Accelerated growth programs during prepubertal 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 on gene expression of the mammary gland in Parda de Montaña primiparous cows. Female calves ( = 16) were involved in a 2 × 2 factorial experiment. In the preweaning period (PRE-W; 0-6 mo), female calves were either fed a creep feed supplement (Creep) or fed only their dam's milk (Control). In the postweaning period (POST-W; 6-15 mo), heifers received either a high-energy diet (91.7 MJ/d) or a moderate-energy diet (79.3 MJ/d). 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 the 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 ( < 0.01), milk CP, crude fat, lactose, nonfat solids, and casein content throughout lactation and increased somatic cell count in the third ( < 0.05) and fourth month of lactation ( < 0.10). The energy level during the POST-W had no effect on milk production and quality. Gene expression in the mammary gland was affected by the diet in the PRE-W and POST-W, with the PRE-W diet having the greatest impact. During the PRE-W, creep feeding resulted in upregulation of genes related to immune response and chemokine activity, suggesting that these animals might be in a compromised immune status. Therefore, this strategy would not be recommendable; meanwhile, increasing the energy level in the diet during the POST-W would be recommendable, because it had no deleterious effects on milk yield and composition.

Beef Cows’ Performance and Metabolic Response to Short Nutritional Challenges in Different Months of Lactation

“…The lower basal milk yield values with progressing lactation agree with previous data on Parda de Montaña cows (Casasús et al, 2004;Dervishi et al, 2017), and suggest that the peak milk yield had already been reached at the start of the experiment, in month 2, as described by Sapkota et al (2020) for beef cows. In the present study, the reduced milk yield caused by feed restriction falls in line with those reported by other studies of comparable lengths and restriction severities in beef cows (− 12%;De La Torre et al, 2022) and dairy cows (− 13 to − 20% in Abdelatty et al, 2017;Laeger et al, 2012;Nielsen et al, 2003).…”

“…The negative correlation herein observed between lactose content and somatic cell count has been associated with inflammatory reactions in milk secretory cells (Cinar et al, 2015). However in our study, somatic cell count was always below the threshold for subclinical mastitis (200 × 10 3 cells/mL; Dervishi et al, 2017).…”

“…Concerning milk composition, the basal milk protein and lactose contents were similar, but fat content was higher than those previously reported in Parda de Montaña cows with a similar milk yield (Casasús et al, 2004;Dervishi et al, 2017). This difference was probably related to the sampling method.…”