Mammary Gland Structures Are Not Affected by an Increased Growth Rate of Yearling Ewes Post-Weaning but Are Associated with Growth Rates of Singletons.

Emmanuelle Haslin,Paul R Kenyon,Stephen T Morris,Adrian J Molenaar,Rene A Corner-Thomas,Hugh T Blair

doi:10.3390/ani11030884

Emmanuelle Haslin, Paul R Kenyon + Show 4 more

Open Access

PDF Available

https://doi.org/10.3390/ani11030884

Copy DOI

Export

Save

Cite

Journal: Animals	Publication Date: Mar 19, 2021
Citations: 3	License type: CC BY 4.0

Affiliation: Massey University, AgResearch

Abstract
Highlights/Summary
Full-Text PDF
Similar Papers

Abstract

Listen

Simple SummaryIncreased growth rates of ewe lambs between three and seven months of age can potentially have negative impacts on mammary development and milk production, affecting their capacity to wean a lamb as yearling ewes. This experiment was designed to examine the impacts of an increased growth rate of ewes between weaning and their first breeding at seven months of age on mammary development using ultrasonography and to establish if mammary ultrasound measures could be indicators of growth of yearling ewe progeny. Mammary measures were taken in late pregnancy, early lactation and weaning in 59 single-bearing yearling ewes either preferentially fed and achieving 47.9 kg at breeding at seven months of age, or fed to achieve 44.9 kg at breeding. Mammary measures did not differ between live-weight gain treatments, indicating no evidence of negative effects on mammary development of yearling ewes. Some mammary measures, however, were positively associated with the growth of the progeny to weaning suggesting that ultrasonography has the potential to identify yearling ewes that would wean heavier lambs.The experiment aimed to examine the impacts of an increased growth rate of ewes between three and seven months of age on udder development using ultrasound and to establish whether ultrasonography could be used to identify ewe mammary structures that may be indirect indicators of singleton growth to weaning. Udder dimensions, depths of gland cistern (GC), parenchyma (PAR) and fat pad (FP) were measured in late pregnancy (P107), early lactation (L29), and at weaning (L100) in 59 single-bearing yearling ewes selected from two treatments. The ‘heavy’ group (n = 31) was preferentially fed prior to breeding achieving an average breeding live-weight of 47.9 ± 0.38 kg at seven months of age. The ‘control’ group (n = 28) had an average breeding live-weight of 44.9 ± 0.49 kg. Udder dimensions, GC, PAR and FP did not differ between treatments. Lamb growth to L100 was positively associated (p < 0.05) with PAR at P107 and GC at L29. There was no evidence of negative effects of the live-weight gain treatments on udder development of yearling ewes as measured by ultrasonography. The results suggest that this ultrasound method has the potential to identify pregnant yearling ewes which would wean heavier singletons.

Highlights

A major determinant for achieving puberty and successful breeding of yearling ewes at seven months of age is the attainment of 40–70% of mature live-weight [1,2]
It was hypothesised that yearling ewes with an increased growth rate would have a reduced mammary parenchymal and a greater fat pad area compared with yearling ewes with a lower growth rate
While the impact of the parenchymal depth in late pregnancy on singleton growth to weaning was moderate, the results suggested that the ultrasound method could potentially be used as a technique to identify pregnant yearling ewes that will wean heavier singletons

Summary

Introduction

A major determinant for achieving puberty and successful breeding of yearling ewes at seven months of age is the attainment of 40–70% of mature live-weight [1,2]. Heavier live-weights at breeding have been shown to improve the reproductive performance of yearling ewes resulting in a greater number of yearling ewes mated during the breeding period, increased fertility rate, litter size, and lambing percentage [2,3] Using this combined knowledge, farmers aim to feed their Romney-type yearling ewes to achieve suitable growth rates post-weaning to ensure they reach liveweights greater than 40 to 45 kg at breeding at seven months of age. As previously described by Haslin et al [20], at weaning, at approximately 86 days of age (127 days prior to breeding; P-127), 270 twin-born Romney ewe lambs (hereafter called yearling ewes) were allocated to one of the two treatment groups using a stratified random sampling procedure to ensure that the average live-weight of the groups did not differ (28.6 ± 0.16 kg). Cereal-based concentrate feed mass offered to the heavy group at a rate of 200 g/yearling ewe/day for 68 days (P-119 to P-51) and 300 g/yearling ewe/day for 51 days (P-51 to P0; Figure 1)

Results

Discussion

Conclusion