Age at puberty and possibility of early breeding in Awassi ewes

Abstract

SummarySixty-four weaned Awassi ewe lambs were used in the present study to estimate age at puberty and to investigate whether early breeding from such ewe lambs is possible. After weaning at 4 months old ewe lambs were divided at random into two experimental groups. One group, designated as moderate, was fed to attain 40 kg live weight at 12 months of age, while the other (high) was planned to reach 50 kg at the same age. Fertile rams were run with the ewe lambs at 6 months of age. Twenty ewe lambs, 10 from each treatment, were slaughtered and their ovaries were examined for the presence of corpora lutea and largest follicles.The overall age at first oestrus was found to be 293 days. Ewe lambs of the high nutritional treatment reached puberty earlier than those of the moderate one (274 v. 312 days). Likewise, single-born lambs reached puberty earlier than twin-born ones (273 v. 312 days). Treatment differences explained 16·5% while type of birth explained 16·3% of the total variance in age at first oestrus. Ewe lambs of the high nutritional treatment experienced more heats than those of the moderate one. Simple correlation coefficients between age at first oestrus and date of birth, daily gain and live weight at puberty were 0·21, 0·09 and 0·75, respectively. Results indicated that ovulation may not occur during the first and second oestrus. From 44 ewe lambs only 12, 10 from the moderate and 2 from the high treatment, lambed 13 viable lambs. Reasons for such a low conception rate (27·3%) are discussed.

Environmental influences on hogget lambing performance and the relationship between hogget and two-tooth lambing performance

“…In general, conception rates reported for each oestrus are low, (Keane 1974b;Allison et al 1975;Baker et al 1978;Youniss et al 1978;Quirke 1979). This has been attributed to ovulation failure and inadequate behavioural responses in hoggets at mating (Edey et al 1977(Edey et al , 1978Youniss et al 1978). Little has been reported on embryonic mortality in hoggets.…”

Morphometric traits with reproduction and production performances of indigenous and exotic sheep breeds of Bangladesh

“…Well-fed lambs come to puberty at nine months, but with inadequate nutrition, puberty may not be onset until twenty months (Gatenby et al, 1997). Awassi lambs on a good diet show the first oestrus at an average age of 274 days (Younis et al, 1978), while Rambouillet crossbred lambs puberty in Rajasthan at about 615 days (Kishore et al, 1982). Unlike temperate regions, the season has an insignificant influence on the age at puberty in the tropics (Ibrahim, 1998).…”