Post-partum intervals to oestrus and conception in Yankasa sheep

Abstract

The potential for twice-yearly lambings by tropical sheep is well recognized (Brown, Cameron & Ngere, 1972; Goode, Linnerud & Tugman, 1980; Osinowo, 1982). In order for ewes to lamb every 6 months the rebreeding interval must be 33 days or less. Factors affecting rebreeding in post-partum ewes have been reviewed (Hunter, 1968a, b Van Niekerk, 1979).

Reproductive performance of sheep and goats under native husbandry

“…The kidding interval of 256-1 ±31-9 days for does is longer than the lambing interval of 2095±211 days for ewes under native husbandry. The latter is shorter than the 236 days (Ademosun, 1973) and 292 ±61 days (Molokwu & Umunna, 1980) reported for ewes under intensive management, but agrees fairly well with the findings of Osinowo & Ekpe (1985). The latter workers reported a mean postpartum interval to conception of 42-5 ± 1-5 days for the same breed of ewes under intensive management; this means that a lambing interval of about 192 days is expected when a gestation period of 150 days is added to their results.…”

“…Although season of lambing has a significant influence on post-partum oestral activity in temperate regions (Barker & Wiggins, 1964), and hence on the intervals, the effects of season and age on the intervals were not considered in this preliminary investigation. However, these factors do not have strong influence on the intervals in small ruminants in the tropics (Molokwu & Umunna, 1980;Osinowo & Ekpe, 1985). Indeed, under the native husbandry, the Nigerian small ruminants are all-year breeders, as observed by Molokwu & Umunna (1980) for ewes under intensive management.…”

“…Although over 90% of small ruminant production in Nigeria is done under native husbandry or semiintensive management, relatively little information on their reproductive performance is available. However, information on the reproductive performance of Nigerian small ruminants under intensive management conducted at Research Centres or Institutes is readily available (Adu, Buvanendran & Lakpini, 1979;Adu, Brinckman & Kuteyi, 1979;Molokwu & Umunna, 1980;Osinowo & Ekpe, 1985). Such reproductive information includes age at first lambing or kidding, birth weight, lambing or kidding intervals, seasonal effects and conception rates.…”

Resumption of post-partum oestrous behaviour and associated plasma progesterone profiles in Menz ewes

“…10-5) days to first ovulation and 76-1 (s.e. However, Gonzalez et al (1987) reported ovulation in Pelibeuy ewes 20 days after lambing and Osinowo and Ekpe (1985) observed two Yankasa ewes that conceived on day 8 and 15 post partum. Ewes may show oestrus within hours or days of lambing (Land, 1971;Evans and Robinson, 1980;Osinowo and Ekpe, 1985), but such heats, like the one recorded 13 days after lambing ( Figure Id), are often false.…”