Production in mature corriedale ewes first mated at 7 to 11 or 18 months of age

Abstract

Production in 210 mature Corriedale ewes first mated between 7 and 11 or at 18 months of age was studied at Paysandu, Uruguay. Ewes were classified into one of the following five classes according to their oestrous and lambing performance in 1968: (1) reared a lamb; (2) lambed but lamb died; (3) mated but did not lamb; (4) oestrus detected by vasectomized ram, true mating deferred for 12 months; and (4) no oestrus, mating deferred for 12 months. Records on flock performance and mortality were kept from all ewes from 1969 to 1973, when the dental status of all ewes present was assessed. There were no significant differences between classes in number of ewes lambing per ewe exposed to the ram, number of lambs born per ewe exposed to the ram, number of lambs weaned per ewe exposed to the ram, weight of lamb weaned per ewe exposed to the ram, and pre-mating body weight. Greasy fleece weight varied significantly (P<0-01) with class of ewe. The least squares means for ewe classes 1 to 5 were 3-93, 3-99, 4-06,4-12 and 3-92 kg respectively. Class 4 ewes differed significantly (/ > <0-01) from class 1 ewes and from class 2, 3 and 5 ewes (i > <0-05). Class 3 ewes differed significantly (/ > <0-05) from class 1 ewes. Other differences were not significant. Ewe mortality between 1969 and 1973 was independent of class of ewe. The dental status of ewes appeared to vary with class of ewe. Early mating of Corriedale ewes apparently had no adverse effects on mature reproductive performance, but somewhat reduced wool production. If mating is to take place for the first time at 18 months of age, ewes that have shown oestrus previously are likely to exhibit greater overall productivity (wool plus lambs).

The effect of breeding hoggets on lifetime performance

“…The lack of a negative effect of hogget breeding on longevity has been also previously reported to at least 6 years of age (Cannon & Bath 1969;Baker et al 1978Baker et al , 1981Ponzoni et al 1979). These findings do TwinÁsingle, born as a twin but reared as a singleton; tripletÁtwin, born as a triplet but reared as a twin; tripletÁsingle, born as a triplet but reared as a singleton.…”

“…Similarly, no negative effect on lamb weaning weight and apparent lamb survival has been reported previously (Cannon & Bath 1968;Baker et al 1978;Ponzoni et al 1979) and, indeed, Baker et al (1981) reported that those ewes that which were bred as hoggets weaned a heavier lamb in later years, with greater apparent survival.…”

“…This clearly indicates that any reduction in twotooth reproductive performance is more than outweighed by the positive effect of an additional breeding as a hogget. Others have previously reported that hogget breeding did not negatively affect ewe pregnancy rates and number of lambs born per ewe as the ewe aged from 2 to 6 years (Cannon & Bath 1969;Baker et al 1978, 1981, Ponzoni et al 1979. It should be remembered that the extra potential benefit from a greater number of foetuses per ewe lifetime, by breeding as a hogget, will only result in a greater weight of lambs weaned per ewe if farmers ensure that hoggets are fed to reach suitable target live weights pre-breeding and in pregnancy (Schreurs et al 2010).…”

Effect of Breeding Heavier Romney Ewe Lambs at Seven Months of Age on Lamb Production and Efficiency over Their First Three Breeding Seasons

“…Kenyon et al [ 1 ] recommended that, in New Zealand, a minimum live weight target should be 40 kg at breeding for Romney-type ewe lambs. To date, studies have focused on the effects of breeding ewe lambs on lifetime performance and efficiency compared to those not bred until 17–19 months of age [ 5 , 6 , 7 , 8 , 9 ], rather than the influence of their ewe lamb breeding live weight per se.…”