Genetic evaluation of crossbred lamb production. 1. Breed and fixed effects for birth and weaning weight of first-cross lambs, gestation length, and reproduction of base ewes

Abstract

This is the first paper in a series that reports on a national maternal sire central progeny test program (MCPT) to evaluate the genetic variation for economically important production traits in first- and second-cross progeny of maternal and dual purpose (meat and wool) sires and the scope for genetic improvement. The MCPT program also provides direct linkages between breeds that will contribute information for across-breed genetic evaluation. Crossbred progeny by 91 sires from more than 7 maternal breeds (including Border Leicester, East Friesian, Finnsheep, Coopworth, White Suffolk, Corriedale, and Booroola Leicester) at 3 sites over 3 years with 3 link sires in common at each site and year were evaluated in this study. National estimated breeding values for the sires that were entered by industry breeders indicated that there was some selection for weight, but not other traits and the sires were generally representative of the maternal genetics available to the industry. There were 8377 base Merino and Corriedale ewes artificially inseminated with thawed-frozen semen from the 91 sires and 8193 crossbred lambs born and 6117 lambs weaned. Mixed model analyses of birth and weaning weight, lamb survival, and gestation length as well as fertility, litter size, and lamb weaning rate of the base ewes are reported. Sire breed was significant for birth weight (with a range of 4.0–4.4 kg at an average litter size of 1.8) and weaning weight (19.6–22.5 kg), as well as lamb survival (70–79%) and gestation length (147.1–150.3 days). Birth/rearing type was significant for all traits. Males were significantly heavier than females at birth and weaning, although there was no sex difference for lamb survival or gestation length when birthweight was included in the model. Pregnancy rate from the artificially inseminated base ewes varied from 40 to 84% at the 3 locations in the various years. Sire breed was significant for the number of lambs weaned per ewe lambing, but not for fetal number or litter size born. There were also significant differences in performance due to the source of the base ewes at each site.

Improving performance of Zackel sheep through cross-breeding with prolific Bluefaced Leicester under semi-intensive and extensive production systems

“…F 1 BL )TA lambs were heavier than TA lambs at all ages (p 5 0.001), except for the birth weight of the lambs from the commercial farm (Site 2), where the genotype did not have an influence on this trait (p ] 0.05). These results are in accordance with Freking and Leymaster (2004) and Fogarty et al (2005), who reported that litter size modulates the expression of foetal growth and differences in birth weight are being detected only when paternal breeds differed markedly in mature body weight.…”

“…The effect of the genotype on birth weight is modulated by the size of the litter (Alvarez et al 2010). Fogarty et al (2005) reported that differences in birth weight between genotypes decreased or disappeared in twin or triplet litters. The weight of lambs at the age of 28 and 60 days was significantly (p 5 0.001) influenced by the genotype but not by the production system (p ] 0.05).…”

Index selection in terminal sires improves early lamb growth1

“…The BWT of triplet and quadruplet born lambs was not significantly different, but singleborn lambs were heaviest, followed by twin-born lambs (results not shown). These results agree with previous estimates from the literature (Peeters et al, 1996;Fogarty et al, 2005): ewes with single lambs have significantly more resources to dedicate to their lambs, which were heavier at all ages.…”

Growth and Body Conformation Responses of Genetically Divergent Australian Sheep to Spirulina (Arthrospira platensis) Supplementation

“…Furthermore, the result of current study confirmed the widely accepted interaction between sire breed and sex on liveweight and body conformation measurements, the basis of which has been extensively studied in the last decade (Afolayan et al, 2006;Cam et al, 2010;Fogarty et al, 2005a;Fogarty et al, 2005b;Hopkins et al, 2007b;. Thus, a demonstration of the strong positive correlations between body measurements and liveweight in our present study reaffirms current consensus (Abbasi and Ghafouri-Kesbi, 2011;López-Carlos et al, 2010;Otoikhian et al, 2008;Sowande and Sobola, 2008).…”