Summary
Lamb efficiency is an important consideration for lamb finishers and lamb producers. Producers are often faced with challenges that impact on efficiency of production, yet it remains difficult to quantify these impacts. In the course of their development many lambs are subjected to a period of restricted nutritional intake. Such a restriction in cattle has been shown to impact upon their subsequent growth and performance, compromising their ability to meet market specifications when sold at the same age as unrestricted contemporaries. These animals also require longer periods on feed to reach market specifications, markedly increasing the cost of finishing (Wright et al, 1986), if indeed they are able to reach target slaughter weights at all (Ryan et al, 1993). In addition, producers are often faced with a challenge of managing tail end lambs, these lambs are light at weaning and take longer to reach a given market specification, representing a challenge to the producer.
There are numerous questions about the subsequent management of these tail end lambs, i.e. Should they be sold in the saleyards at weaning? Should they be put into a light slaughter market (Muslim kill)? or should they be retained and finished at a later date and if so, how long should they be retained for? These management questions centre on making the most efficient use of this resource by addressing at what age and stage of development is the lambs efficiency optimised? A comprehensive review of available literature on lamb efficiency was conducted. In addition, 350 lambs, representing 21 sire groups were tested for feed intake and efficiency.
As a result of monitoring the efficiency of a diverse group of lambs it was possible to develop industry guidelines that outline the key drivers for improved efficiency of lambs during finishing. Identifying the optimum time to finish a specific group of lambs maximises potential returns. Management of lambs prior to finishing must consider the inherent variations within a group of lambs, variations such as genetic potential, weaning weight and age will all influence the optimum time to finish the lambs.
To meet the needs of the scientific community two scientific papers: The effect of a pre-weaning nutritional restriction on lamb development and efficiency during finishing and The impact of weaning weight and age during finishing on lamb development and efficiency during finishing are being submitted for publication. Findings Previously restricted lambs were lighter at all time points post the period of nutritional restriction, and it is unlikely that they would have compensated to a point of similar body weights as unrestricted lambs.
An early nutritional restriction in ewe lambs worsens feed efficiency during finishing (by approximately 3 FCR units). However, the early nutritional restriction had no impact on the later feed efficiency of wether lambs. For both light and heavy weaning weight lambs, decreasing sire PFAT by 1.5mm improved lamb efficiency by about 5 FCR units. In general lambs that were light at weaning gained less weight during finishing than lambs that were heavy at weaning, however the weight gain of these lighter lambs was characterised by proportionately more lean deposition resulting in increased LMY at slaughter. However, this did not result in differences in FCR. Lambs finished at older ages grew slower, deposited proportionately more fat, and had reduced LMY, all characteristics demonstrated by more mature animals. This slower growth was associated with poorer FCR in the older lambs. Lambs with low weaning weights can have acceptable FCR for an intensive finishing system, but there is a significant decrease in FCR, irrespective of weaning weight, when lambs are taken out to older ages. In these cases lambs that are light at weaning are best sold at younger ages and targeted at a lighter market specification.
Those sectors of the industry closest to the work (lamb finishers) have already benefited from research outcomes. Lamb finishers (those based on grain or grass) are able to improve the efficiency of their lamb finishing operations by utilising project recommendations. Lamb energetics was specifically developed with a whole of chain approach, and as such awareness of project outcomes has not been limited to lamb finishers. Should seed stock producers have access to technologies or tools such as breeding values that facilitate improvements in feed efficiency, whole of chain improvements are almost assured. Awareness of and interest in the efficiency of finishing lambs has not been confined to terminal lamb operations. Almost unexpected at the start of the project was the surge in interest (towards the conclusion of the project) in maternal efficiency from a reproduction and metabolic viewpoint. So while those operations that include a lamb finishing component are best placed to take advantage of research findings, seed stock producers and lamb breeders are also positioned to take advantage of flow on benefits.
