Effect of shearing on lamb growth and carcase performance

NJ Mclean, HJB Craig, PF Fennessy, MJ Behrent, JI Kerslake and AW Campbell - Proceedings of the New Zealand Society of Animal Production 2015. Vol 75: 215

Type: Research Paper
Knowledge level: Advanced

Farm Table says:

A study that includes the financial aspect of shearing lambs and the differences in growth rates seen between different shearing treatments.

What is the problem?

This study investigated the belief that shearing lambs improve lamb growth rates and performance. The authors suggest previous research has given varying results due to variations in environments and aimed to investigate this management tool on final finishing and lamb performance in a modern system.

What did the research involve?

The study was conducted on three properties in New Zealand, starting April 2015, and used a randomized experimental design to assign one of 4 treatments to 1,183 lambs – shorn fasted, bellied fasted, woolly fasted or woolly not fasted. Lambs that were shorn fasted, bellied fasted and woolly fasted were held in the yards overnight after weighing and fasted before shearing. The woolly not fasted group was weighed and returned to the paddock directly after. Once treatments were applied, lambs were re-weighed and returned to the not fasted mob.

After shearing treatments, lambs had unrestricted grazing on pasture with cover between 1700 – 2200 kg/DM per hectare. Lambs were weighed twice and sent for live slaughter once the desired live weight was reached. Growth rate difference calculations were adjusted for fasting and the removal of wool to give a true indication of the effect the different treatments had on lamb performance. Average daily gain (ADG) was then calculated, and the differences between treatments analyzed for ADG, carcase weight and meat yield were calculated. Variations between sites were corrected for.

A financial analysis was included, using a fixed carcase weight, averaging 18 kg and a fixed price of $5.20/kg. Average fleece weight was calculated as 1.85 kg and fleece value fixed at $5.40/kg. Shearing costs were also factored in using amounts obtained from the Lincoln Farm Technical Manual (2013). Further details of the financial assumptions can be found by following the link.

What were the key findings?

Shorn fasted lambs grew 12g/day faster than woolly fasted lambs, with this like the other two treatment groups. It was concluded this difference in growth did not overcome the effect of weight loss from overnight fasting. No differences were seen between groups for carcase weight, meat yield or proportion of lambs at slaughter.

Final comment

Though there was no economic benefit seen from shearing lambs on carcase weight or meat yield, if that value of wool is considered, shorn lambs were of greater value to the farmer.

2015 - New Zealand - NJ Mclean, HJB Craig, PF Fennessy, MJ Behrent, JI Kerslake and AW Campbell - Proceedings of the New Zealand Society of Animal Production 2015. Vol 75: 215
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