Mammary gland differential growth during pregnancy in superovulated Javanese thin-tail ewes

Abstract

Twenty-one pregnant ewes (12 non-superovulated and nine superovulated prior to mating) were used to study the effect of superovulation on mammary gland differential growth at weeks 7 and 15 of pregnancy. The experimental ewes were slaughtered at the respective stage of pregnancy and the mammary glands were excised to determine mammary gland growth and development by measuring mammary dry fat-free tissue (DFFT), mammary DNA, RNA, collagen, protein and glycogen. In the ewes slaughtered at Week 7 of pregnancy, superovulation increased ( p < 0.05) mammary DFFT (g) (by 33%), mammary collagen concentrations (μg/mg DFFT) (by 23%), total mammary RNA (mg) (by 33%), collagen (mg) (by 64%), protein (mg) (by 34%), and glycogen (mg) (by 29%) without any difference in mammary RNA, protein and glycogen concentrations (μg/mg DFFT), and total mammary DNA. In the ewes sacrificed at Week 15 of pregnancy, superovulation increased ( p < 0.05) mammary RNA and glycogen concentrations (μg/mg DFFT) (by 82 and 22%, respectively) without any difference in DFFT, mammary DNA, collagen, and protein concentrations (μg/mg DFFT), total mammary DNA, RNA, collagen, protein and glycogen. The results of the experiment indicated that the reported increase in milk production in the superovulated-lactating ewes was made possible through the greater hormonal stimulation of the mammary ductal growth in the early phase of pregnancy, and of epithelial cell multiplication and activities during the later phase of pregnancy.