Genetic parameters for reproduction and lamb production and their components and liveweight, fat depth and wool production in Hyfer sheep

Abstract

Hyfer is a new composite breed suited to specialized lamb production and developed from Dorset (+), Booroola Merino (+)and Trangie Fertility Merino (+) genotypes. Genetic parameters estimated by restricted maximum likelihood methods are reported for liveweight, wool production and a range of reproduction and lamb production traits. Estimates of heritability were 0 44 � 0.10, 0.222 � 0-08 and 0.28 � 0.08 for liveweight, ultrasonic fat depth (C site) and fat depth adjusted for liveweight respectively, for 1454 rams averaging 14 months of age, which were the progeny of 130 sires. The genetic correlation for ram liveweight and fat depth was 0.06 � 0.17 and -0.30 � 0.16 with adjusted fat depth. Estimates of heritability for ewe liveweight at 12-18 months of age and greasy fleece weight at 11-19 months of age were 0.61 � 0.10 and 0.38 � 0.08 respectively, with a genetic correlation of 0.35 � 0.13, based on 1619 ewes, which were the progeny of 135 sires. A maternal effect was significant for ewe liveweight and its inclusion in the model reduced the estimate of heritability to 0.44 � 0.09. Young ewes were joined three times in two years in an accelerated 8-monthly lambing system, and joinings commenced in mid-February, late October and mid-June. The estimates of heritability for overall ewe performance were for lambs born 0.09 � 0.03, lambs weaned 0.04 � 0.02 and weight of lamb weaned 0 -06 � 0.02 (all per ewe joined). Heritabilities for the component traits were: fertility 0 -03 � 0 02, litter size 0.19 � 0.04 and lamb survival 0.07 � 0.03. Estimates of repeatability for the corresponding traits ranged from 0.11 to 0.15, except for litter size (0.26 � 0.02). Estimates of heritability for lambs born, lambs weaned and weight weaned were higher for the first joining than when estimates were based on three joining records. This was associated with higher heritability for fertility from first joining (0.10 � 0.06) than for all three records and the reverse for lamb survival. Estimates of heritability for mean ewe performance were considerably higher and in agreement with the values predicted from the repeatability analyses and number of records, illustrating the value of using repeated ewe records for selection. The genetic correlations between the component traits and overall measures of lamb production were not high enough to consider using component traits as indirect selection criteria. The genetic correlations of liveweight with reproduction traits were positive, but generally not significant, and ranged from 0.01 to 0.63, except for litter size (-0.19 � 0.17). The genetic correlations of greasy fleece weight with reproduction traits were generally smaller than those for liveweight, were not significant and ranged from -0.12 to 0.32. These results, together with others, will be used to compile parameter sets for use in LAMBPLAN to provide meatsheep breeders with comprehensive breeding objectives incorporating growth, leanness, wool and reproduciton.

Genetic parameters for ewe reproduction with objectively measured wool traits in Elsenburg Merino flock

“…Direct heritability (h 2 a ) was estimated at 0.10 ± 0.03 for NLB1, 0.07 ± 0.02 for NLW1, and 0.10 ± 0.03 for TWW1. Fogarty et al (1994) reported a higher value for NLB1 (0.20 ± 0.08) than that reported in the current study using data from Hyfer sheep. The estimate for TWW1 in this study is higher than that of 0.02 reported earlier in the Tygerhoek Merino flock (Duguma et al, 2002).…”

“…Number of lambs weaned per ewe joined over three lambing opportunities (NLW3) was heritable at 0.12 ± 0.03 in the current study. Comparable estimates for NLW3 suggested a range of 0.02 to 0.29 (Fogarty et al, 1994;Snyman et al, 1998b;1998c;Olivier et al, 2001;Cloete et al, 2002;Duguma et al, 2002;Cloete et al, 2003;Van Wyk et al, 2003;Cloete et al, 2004;Safari et al, 2005;Olivier & Cloete, 2006;Vatankhah & Talebi, 2008;Afolayan et al, 2009;Mokhtari et al, 2010;Rashidi et al, 2011;Mohammadi et al, 2012;Boujenane et al, 2013;Olivier, 2014). The current estimate of NLW3 is higher than the value of 0.05 derived from eight reports by Safari et al (2005).…”

<b>Estimates of genetic and phenotypic parameters for reproductive traits in Iranian native Kordi sheep

“…Moreover, ratio of permanent environmental variance on phenotypic variance for NLB/EL, NLW/EL, TWLB/EL and TWLW/EL ranged from 0.01 to 0.03. The estimates for NLB/EL and NLW/EL are within the range of the studies conducted by Fogarty, Brash, and Gilmour (1994) and Mokhtari et al (2010). Reported estimates of heritability for NLB/EL by Mohammadi et al (2012) were 0.11 for Makooei sheep and by Ekiz et al (2005) and Van Wyk, Fair, and Cloete (2003) for Merino and Dormer sheep was 0.053 and 0.059, respectively.…”

Composite trait selection to improve reproduction and ewe productivity: a review

“…Several genetic correlations with litter weight weaned have been estimated (Table 2). The breeds from which these estimates were derived include: Australian Hyfer (a cross of Booroola Merino, Trangie Merino and Dorset; Fogarty et al 1994); Australian Merino (Cloete et al 2002a);South African (Cloete et al 2004) Merino; a grouping of USA Dorset, Finnsheep, Rambouillet, Suffolk, Targhee and two composite lines (Rosati et al 2002); and four USA breeds independently, Columbia, Polypay (a fourbreed cross including Finnish Landrace), Rambouillet and Targhee (Bromley et al 2001). Estimates were also derived from a large crossbred ewe population (sires from many different maternal breed types, and Merino dams; Afolayan et al 2008).…”