Preweaning nutrient supply alters mammary gland transcriptome expression relating to morphology, lipid accumulation, DNA synthesis and RNA expression in Holstein heifer calves.. Preweaning nutrient supply alters mammary gland transcriptome expression relating to morphology, lipid accumulation, DNA synthesis and RNA expression in Holstein heifer calves.

The objective of this study was to analyze the mammary gland transcriptome to determine how preweaning nutrient supply alters the molecular mechanisms that regulate preweaning mammary development. Holstein heifers were fed via milk replacer either an elevated level of nutrient intake (ELE; on average, 5.9 ± 0.2 Mcal ME in 8.4 L of milk replacer (MR)/d, n = 6) or a restricted amount of nutrients (RES; 2.8 ± 0.2 Mcal ME in 4L MR/day, n = 5) for 54 d postnatal, at which point they were slaughtered and samples of mammary parenchyma tissue were obtained. Parenchymal mRNA was analyzed and the fold changes (FC) of 18,111 genes (ELE relative to RES) were uploaded to Ingenuity Pathway Analysis (IPA) software for transcriptomic analysis. Using a threshold of P 2) and 7 were inhibited (Z < -2). In summary, feeding ELE preweaning altered the mammary transcriptome of Holstein heifers affecting cell functions involved in the morphological and physiological development of the mammary gland. Overall design: Holstein heifer calves were subjected to restricted or elevated nutrient supply through milk replacer during the preweaning phase. From day 18 onwards, calves were also offered a commercially available concentrate. At day 54 calves were killed, whereafter mammary gland tissue was subjected to gene expression profiling.