Mating Conditions and Management Practices Influence Pregnancy Scanning Outcomes Differently between Ewe Breeds

Amy L Bates; Shawn R McGrath; Susan M Robertson; Gordon Refshauge

doi:10.3390/ani12212908

Mating Conditions and Management Practices Influence Pregnancy Scanning Outcomes Differently between Ewe Breeds

Animals (Basel). 2022 Oct 24;12(21):2908. doi: 10.3390/ani12212908.

Authors

Amy L Bates^{1

2}, Shawn R McGrath^{1

2}, Susan M Robertson^{1

2}, Gordon Refshauge³

Affiliations

¹ School of Agricultural, Environmental and Veterinary Sciences, Charles Sturt University, Wagga Wagga, NSW 2678, Australia.
² Gulbali Institute, Charles Sturt University, Wagga Wagga, NSW 2678, Australia.
³ New South Wales Department of Primary Industries, Cowra, NSW 2794, Australia.

Abstract

Sheep production in southern Australia may vary by breed, time of year, production output (wool, meat, or both), region and seasonal influence. Sheep producers with flocks of approximately 300-500 ewes (n = 58) were recruited across southern Australia to take part in a survey and mating variables were collected from over 30,000 ewes between October 2020 and August 2021. A Bayesian Network (BN) was developed to identify the interrelatedness and most influential variable on pregnancy and fetal number (of pregnant ewes) outcomes under different scenarios. The BN analysis indicated a low association between the variables explored, however, were breed dependent. In wool-based breeds a mating liveweight of 60-69.5 kg predicted the lowest non-pregnant and greatest number of fetuses, and in shedding ewes 70-79.5 kg predicted the lowest non-pregnant rate and 90-99.5 kg the greatest number of fetuses. Pregnancy rate and fetuses per ewe were optimized at ram percentages of 1.5% for Composite and Merino ewes and 2% for Maternal ewes. A mating BCS 4 resulted in greatest pregnancy rate and number of fetuses across all breeds. Curvilinear relationships between mating liveweight, BCS and ram percentage were observed with pregnancy rate and fetal number. Practically, reproductive potential is best managed on a breed basis and with consideration of all variables explored.

Keywords: Bayesian network; flock management; mating condition score; mating liveweight; pregnancy scanning; ram percentage; sheep.

Grants and funding

This research was funded by Meat and Livestock Australia and Australian Wool Innovation (Project No. L.LSM.0020), the New South Wales Department of Primary Industries, Charles Sturt University and an Australian Government Research and Training Scholarship awarded to A.L.B.