Higher weaning weight improves postweaning growth and survival in young Merino sheep

Abstract

Two monitoring projects were conducted to investigate weaner mortality in commercial Merino flocks in the Yass and the Central Tablelands Rural Lands Protection Boards located in the Southern Tablelands agricultural region of New South Wales. The projects were conducted in Yass in 2005 and in the Central Tablelands in 2006. A random sample of weaners from four flocks in the Yass board and 11 flocks in the Central Tablelands board were regularly weighed, growth rates were calculated after weaning and survival was determined by the continuing presence of an individual weaner at subsequent weighing activities. Weaning weight was the most important factor in determining postweaning liveweight, growth rates and survival with the significant impact of weaning weight on liveweight persisting for up to 6 months after weaning. Despite the lightest weaners being capable of considerable compensatory growth given sufficient postweaning nutrition, the lightest 25% of weaners were more than twice as likely to die as heavier weaners. A focus on ewe nutrition and parasite control during late pregnancy and lactation will allow Merino producers to achieve higher weaning weights that will set their weaners up for strong postweaning growth with a decreased likelihood of mortality.

Improving the nutrition of Merino ewes during pregnancy and lactation increases weaning weight and survival of progeny but does not affect their mature size

“…Progeny that were heavier at weaning remained heavier during the first summer and autumn when most deaths occurred and had higher survival rates to 12 months of age than those that were lighter at weaning. This is consistent with the findings of Denney (1990), Hatcher et al (2008) and Campbell et al (2009) and occurred despite evidence of compensatory growth by the lighter weaners. Survival rates were very sensitive to liveweight when weaning weight was below 20 kg, whereas the changes in weaner survival from increasing weaning weights above 20 kg were much smaller.…”

“…Most weaner mortalities occurred during the 5 months after weaning, which is consistent with the findings of Hatcher et al (2008) and Campbell et al (2009). The average growth rate during this period for weaners from different pre-weaning nutritional treatments was not significantly associated with mortality risk of individual progeny at either site.…”

“…Lamb growth to weaning and during the period immediately following weaning influences post-weaning mortality (Hatcher et al 2008;Hocking-Edwards et al 2008;Campbell et al 2009). The lightest 20% of Merino weaners within a flock are~3 times more likely to die than those from the middle 20% of weaning weights, and Campbell et al (2009) reported that increasing growth rates from~10 to 20 g/day during the 5 months after weaning reduced the risk of mortality by more than 70%.…”

Genetic Parameters for Growth Traits of the Hungarian Merino and Meat Sheep Breeds in Hungary

“…These correlations were only different from zero for Texel, Ile de France, German Mutton Merino and German Blackheaded. Weaning weight is the most important factor in determining postweaning liveweight, growth rates and survival of Merino lambs (Hatcher, 2008). This positive relationship was also proved in this study, except for the German Blackheaded.…”

Altering ewe nutrition in late gestation: II. The impact on fetal development and offspring performance1

“…The ability of the lamb to undergo compensatory growth postweaning has been demonstrated by Hatcher et al (2008). Similarly, Galvani et al (2014) reported that lambs reared by low milk yielding ewes had the greatest DMI and subsequently growth rate throughout the postweaning period.…”