Breeding Ewe Lambs: An Australasian Perspective

Abstract

A number of potential advantages have been identified for breeding ewe lambs at 7 to 9 months of age, including increased lifetime productivity and profitability. However, breeding at this young age in extensive pastoral systems, such as in Australasia, can be associated with a number of disadvantages resulting in uptake of this management procedure being relatively low. This review highlights the known differences between ewe lamb and mature ewe reproductive performance, thus differing in their management. The review then summaries the scientific literature of factors that affect ewe lamb reproductive success, with a focus on recent studies conducted under extensive pasture-based conditions in Australasia. In particular, this review outlines the importance of ewe lamb live weight and body condition score on their productivity. The potential long-term consequences of breeding a ewe lamb at a young age in terms of her future success and that of her offspring to weaning are briefly outlined. In addition, the potential impacts of selecting progeny born to ewe lambs as future replacement ewes are discussed. Throughout this review, optimal management guidelines from prior to breeding the ewe lambs until rebreeding at 2 years of age are provided. Lastly, areas requiring future research are identified and discussed.

Genome-Wide Association Studies of Live Weight at First Breeding at Eight Months of Age and Pregnancy Status of Ewe Lambs

“…This result contrasted with Fossceco and Notter [ 4 ], who reported a medium negative genetic correlation (−0.25) between live weight at three months of age and fertility in ewe lambs. Ewe lambs were bred at six months of age, at a minimum live weight of 27 kg, and were bred with ram lambs [ 4 ], both of which were reported to lower the reproductive performance of ewe lambs [ 1 , 37 ]. In addition, the live weight at three months of age used to estimate the genetic correlation with ewe lamb fertility included the live weight of both ewe and ram lambs [ 4 ], increasing the overall live weight in the estimation of the genetic correlation between these traits.…”

Additive Impacts of Liveweight and Body Condition Score at Breeding on the Reproductive Performance of Merino and Non-Merino Ewe Lambs

“…Breeding ewe lambs at seven to 10 months of age can increase the profitability of sheep enterprises depending on their reproductive performance [ 1 , 2 , 3 ]. The reproductive performance of ewe lambs is highly variable, and multiple factors contribute to this variability, as reviewed by [ 4 , 5 ]. Merino ewe lambs that are heavier due to improved nutrition pre- and post-weaning consistently achieve puberty at a younger age, are more fertile (percentage of ewes pregnant per 100 ewes exposed to fertile rams), and have a higher reproductive rate (number of fetuses per 100 ewes exposed to fertile rams) [ 6 , 7 , 8 , 9 ].…”

Effects of propylene glycol used at different doses in Akkaraman lambs rations on metabolism‐related parameters and liver gene and protein expression during different feeding periods

“…The production of lamb meat is a complex process that involves several factors, including genetics, management, and nutrition. Nutrition is one of the major crucial factors for lamb breeding, and studies are being conducted on lamb fattening using different rations and feed additives such as propylene glycol (PG) (Kenyon & Corner‐Thomas, 2022).…”