Dynamic dams for lamb production: More $$$s from crossbred ewes with the right genetics

Summary

This Technical Bulletin provides results and take-home messages from the combined analysis of the MCPT (maternal sire central progeny test), along with implications for the various sectors of the lamb industry. By applying the results to ensure their ewe flocks comprise superior maternal genetics, lamb producers can obtain immediate benefits.

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Excerpt from the report

The Maternal sire Central Progeny Test (MCPT) has progeny tested 91 sires from many maternal breeds including Border Leicester, Coopworth, East Friesian and Finnsheep at 4 sites (Cowra, NSW, Hamilton and Rutherglen Vic and Struan, SA).Common sires were used to provide genetic links across the sites and years to enable combined analysis of the data. The major focus was on evaluation of the 1stX ewe progeny which were grown out and mated for 3 lambings and their 2ndX slaughter lambs. The survival and growth of the 1st Xlambs and carcase performance of 1st Xwethers were also evaluated in the first phase. Performance of the 2,700 1stX ewes was assessed by their lamb turnoff rate, the growth and carcase merit of their 11,000 2ndX lambs and their wool production.

The results have clearly demonstrated the considerable genetic variation among maternal genetics that can be exploited to dramatically improve productivity and profitability of lamb enterprises. While there were some significant differences between the maternal sire breeds in performance of their progeny, the variation among individual sires within the breeds was far greater for most production traits. The range among the 18 Border Leicester sires tested was over $40 gross margin / ewe / year in the profitability of their 1stX daughters. This means a $20,000 higher annual profit for a 1000 ewe enterprise by having 1stX ewes sired by top rather than average maternal genetics.

Variation in lambing rate of the 1stX ewes was the major profit driver that contributed to the differences in gross margins. Over 80% of enterprise income was derived from lamb sales and less than 20% from wool.There were differences of up to 45% for lamb weaning rate between 1stX ewe progeny groups of sires within a breed. In addition there were significant differences in 2ndX lamb growth (up to 3.6 kg for post weaning weight) and carcase fat (2.2 mmGR or almost half a fat score). These differences contributed to the gross margin through total weight of carcase turned off and varying proportions of the carcases meeting market specifications. There were also large differences between breeds and sires within breeds for early age of puberty, milk production and weight and fibre diameter of wool from the 1stX ewes. Most breeds had at least some sires that had high performing 1stX daughters.

Taking account of the variation in feed requirements for the 1stX ewes and their 2ndX lambs, which affects carrying capacity, generally had little impact on the rankings of the maternal sires, with a couple of exceptions. The best sire groups of 1stX ewes varied to some extent at least with the production system. For example some groups of ewes with very high lambing rates performed relatively better in a spring rather than autumn joining system because of better lamb survival at a lambing time when weather conditions were more benign. The importance of carcase weight and fat levels also varies with the target market (domestic or export and saleyard or grid based selling). This emphasises the importance of breeders clearly identifying their production and marketing system and matching it with the most appropriate genetics.

Using LAMBPLAN EBVs to maternal sires results in higher performing crossbred ewes. The correlations between the maternal sire LAMBPLAN EBVs and the growth, carcase and wool production performance of their progeny in MCPT were positive and moderately high. The relative performance of the sires in the growth and carcase of their 1stX progeny was also consistently expressed in their 2ndX progeny. The relationships between LAMBPLAN EBVs of the maternal sires and 1stX ewe reproduction traits were positive although lower than for growth and carcase traits. This reflects the smaller number of animals with recorded reproduction information in the LAMBPLAN data base compared to growth and carcase traits, resulting in lower accuracy of these EBVs. The more widespread recording of reproduction information on maternal breed animals should improve the accuracy of these reporduction EBVs.

Lamb producers can benefit immediately from applying the results of the MCPT project by ensuring that their ewe flocks comprise superior maternal genetics. This means breeding or purchasing crossbred ewes that are by rams with high LAMBPLAN EBVs for the traits that match the lamb enterprise and ensuring that they are bred from high performing base eweflocks. The results show that an increase of $20 gross margin/ewe/year can be achieved from 1stX ewes by top maternal sires compared to those by average sires.