| dc.description.abstract | The production performance of 425 Javanese ewes based on 1143 records produced at the Cicadas sheep Research Station of the Research Institute of Animal Production, Bogor, Indonesia, was evaluated in this study. Although the focus was on the effect of prolificacy and some major environmental causes of variation on lamb survival and ewe output at weaning, the analysis included other traits such as litter size, age at first lambing and lambing interval. Results concerning variation of litter size were consistent with previous studies and with a major gene hypothesis proposed to explain the genetic variation of the trait.
Three lines of prolificacy classified as noncarriers or low line (LL) and carriers of the gene: medium (ML) and high line (HL) averaged 1.24, 1.81 and 2.26 lambs, respectively. from Ewes different prolificacy lines performed distinctly in different years (P<0.01); with HL animals being more sensitive to environmental fluctuation. Primiparous ewes had 10 to 13% smaller litters (P<0.01) than ewes at later parities. The repeatability for litter size was 0.51 while the within line 0.33, 0.15 and 0.24 Heritability was 0.62. for LL, Changes ML, in and HL, respectively. survival were due to Prolificacy-Year and ewe weight gain during gestation (P<0.01).
Survival in the HL was 44% lower than that of ML and LL in poor years. Lamb survival for quadruplets was 86, 67, 44, singles, and twins, triplets and 31% respectively. Lower survival of their lambs (64.9%) as compared to later parities (74.6%) (P<0.01), was recorded in primiparous ewes mainly due to low body weights. Two main causes associated with lamb mortality were studied: ewe weight gain during gestation and lamb birth weight, which have a relative contribution of in the determination of this trait…dst | id |
