Abstract
This study investigated potential carry-over effects of increased growth rates prior to breeding at seven months of age on mammary glands of two-year-old ewes bearing one or two lambs, and examined the association between ewe mammary structures and the growth of their progeny. Ewe live weight and mammary ultrasound measures were recorded at 119 days of pregnancy, 29 days of lactation (L29), and weaning of the progeny (L79) in 64 two-year-old ewes selected from two treatments. The heavy group (n = 32) was preferentially fed prior to their first breeding at seven months of age, achieving an average live weight of 47.9 ± 0.38 kg. The control group (n = 32) weighed an average of 44.9 ± 0.49 kg at breeding. Lambs (n = 74) were weighed at birth, L29 and L79. Udder ultrasound measures did not differ (p > 0.10) between treatments, indicating no carry-over effects of treatments on mammary glands of two-year-old ewes. The association between ultrasound measures and lamb growth seemed to differ depending on lamb birth rank. More research is needed to further investigate these associations and determine whether ultrasonography could be used to identify ewes whose progeny would have greater growth rates based on birth rank.
Highlights
Higher growth rates between weaning and puberty can have detrimental effects on mammary gland development and milk production in ewe lambs [1,2,3,4,5,6]
These findings are consistent with Haslin et al [15,26] that indicated that increased growth rates prior to ewe lambs’ first breeding at seven months of age had no effect on ultrasound measures and morphology of the mammary gland during pregnancy and lactation nor subsequent lamb weaning weights
The present results suggest that there were no carry-over effects of increased growth rates between weaning and breeding at seven months of age on the morphology and dimensions of the internal structures of the mammary gland of two-year-old ewes
Summary
Higher growth rates between weaning and puberty can have detrimental effects on mammary gland development and milk production in ewe lambs [1,2,3,4,5,6]. The allometric phase of mammary gland development in ewe lambs occurs between two and five months of age [1,7]. During this phase, parenchymal development will determine future development of the alveoli and, subsequently, milk production [4,5,6]. About potential carry-over effects of an increased growth rate of ewe lambs between weaning and their first breeding at seven months of age on the mammary gland of ewes and its internal structures
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