Reproduction in ewe lambs and its effect on 2-year-old performance

Abstract

Reproductive performance was studied in 1-and 2-year-old Romney and Border Leicester x Romney ewes. Control lambs were joined with vasectomised rams, and the remainder were joined with entire rams for 5 weeks. Fertility, growth rate, and weaning rate were higher in crossbred ewe lambs, and birth rank effects were small. Conception rate to first service was negatively related to liveweight gain over joining. Weaning rate (57070 lambs weaned/ewe joined) was lower than normally expected from adult ewes. Lamb survival was improved in previously lambed 2-year-old ewes, whereas oestrous and ovarian activity, fertility, fecundity, and lamb growth were unaffected. Ewe liveweight and fleece weights were temporarily reduced. It is concluded that lambing in l-year-old ewes can enhance their reproductive performance as 2-year-olds.

Effect of hogget nutrition in pregnancy on lamb birthweight and survival to weaning

“…In support of the present findings, Moore et al (1989) reported that lamb survival to weaning was not affected by hogget pasture allowance in pregnancy when daily herbage allowances ranged from 2-10 kg DM. Singleton-and twin-lamb survival rates to weaning were 76.2 and 61.7%, respectively in the present study which were similar to those previously reported by McMillan (1983), McMillan & McDonald (1983), and Moore et al (1989). McMillan (1983) and McMillan & McDonald (1983) stated that optimal survival rates for lambs born to hoggets were achieved in the birthweight range of 3.3-4.1 kg.…”

“…Singleton-and twin-lamb survival rates to weaning were 76.2 and 61.7%, respectively in the present study which were similar to those previously reported by McMillan (1983), McMillan & McDonald (1983), and Moore et al (1989). McMillan (1983) and McMillan & McDonald (1983) stated that optimal survival rates for lambs born to hoggets were achieved in the birthweight range of 3.3-4.1 kg. In the present study the average birthweights of all nutritional treatments were within this range.…”

“…In contrast, in the mature ewe the aim is generally not to increase conceptus-free liveweight. It is likely that the affects of poor nutrition in pregnancy would be more pronounced in the hogget than in the mature ewe, as hoggets tend to give birth to relatively lightweight lambs (McMillan 1983;McMillan & McDonald 1983) which display low survival rates (McCall & Hight 1981;Craig 1982;McMillan 1983;McMillan & McDonald 1983;Moore et al 1989). Interestingly, Wallace et al (1996Wallace et al ( , 1997 and Wallace (2000) reported that a very high level of hogget nutrition using concentrates increased foetal loss via spontaneous non-infectious abortion, decreased lamb birthweight and colostrum production, and increased neonatal losses.…”

“…In the present study, hoggets were not weaned until January, which would have limited the time available for "low" group hoggets to achieve adequate two-tooth mating weights. Interestingly, field studies to date have not reported decreased two-tooth reproductive performance from hogget lambing (McCall & Hight 1981 ;Craig 1982;McMillan & McDonald 1983;Moore et al 1989).…”

The effect of breeding hoggets on lifetime performance

“…However, the relative size of the differences, when apparent, was relatively small (maximum of 3 kg weight and 0.2 condition score). The results of previous studies support the negative impact of hogget breeding on two-tooth live weight (Keane 1974;Baker et al 1981;McMillan & McDonald 1983). However, other studies found that the live weight effect was no longer apparent in later years (Cannon & Bath 1969;Dyrmundsson 1973;Baker et al 1978Baker et al , 1981.…”