Heritability of ram mating success in multi-sire breeding situations

Abstract

Multi-sire mating of a mob of ewes is commonly used in commercial sheep production systems. However, ram mating success (defined as the number of lambs sired by an individual) can vary between rams in the mating group. If this trait was repeatable and heritable, selection of rams capable of siring larger numbers of lambs could reduce the number of rams required for mating and ultimately lead to increased genetic gain. However, genetic correlations with other productive traits, such as growth and female fertility, could influence the potential for ram mating success to be used as a selection trait. In order to investigate this trait, parentage records (including accuracy of sire assignment) from 15 commercial ram breeding flocks of various breeds were utilised to examine the repeatability and heritability of ram mating success in multi-sire mating groups. In addition, genetic and phenotypic correlations with growth and female fertility traits were estimated using ASReml. The final model used for the ram mating success traits included age of the ram and mating group as fixed effects. Older rams (3+years old) had 15% to 20% greater mating success than younger rams (1 or 2 years of age). Increasing the stringency of the criteria for inclusion of both an individual lamb, based on accuracy of sire assignment, or a whole mating group, based on how many lambs had an assigned sire, increased repeatability and heritability estimates of the ram mating success traits examined. With the most stringent criteria employed, where assignment of sire accuracy was >0.95 and the total number of lambs in the progeny group that failed to have a sire assigned was<0.05, repeatability and heritability for loge(number of lambs) was 0.40±0.09 and 0.26±0.12, respectively. For proportion of lambs sired, repeatability and heritability were both 0.30±0.09. The two ram mating traits (loge(nlamb) and proportion) were highly correlated, both phenotypically and genetically (0.88±0.01 and 0.94±0.06, respectively). Both phenotypic and genetic correlations between ram mating success and growth and other female fertility traits were low and non-significant. In conclusion, there is scope to select rams capable of producing high numbers of progeny and thus increase selection pressure on rams to increase genetic gain.

Genetic parameter estimates for bull prolificacy and its relationship with scrotal circumference in a commercial beef cattle population

“…Results suggest that although CC is lowly heritable genetic progress could be made for the complex trait of bull prolificacy. However, the estimate from the current study is less than the estimate of 0.26 reported by Juengel et al (2019) from a sheep population comprised of field data from multiple breeds.…”

“…Estimates of heritability for sire prolificacy are limited in the literature. A recent example in rams, where prolificacy was defined as log e (number of lambs), reported heritability and repeatability estimates of 0.26 ± 0.12 and 0.40 ± 0.09, respectively ( Juengel et al, 2019 ) illustrating that underlying genetic control of this trait complex exists. Unfortunately, given the fact that this trait expresses later in life, after an animal has become a parent, selection can be impeded due to the delay in phenotypic observations to inform genetic merit estimates (i.e., Estimated Breeding Values).…”

Consistent variations in personality traits and their potential for genetic improvement of biocontrol agents:Trichogramma evanescensas a case study

“…As a comparison, breeding programmes for livestock animals generally make use of traits with higher heritability. Heritability values for morphological, physiological, behavioural or other traits linked to fitness and considered in these breeding programmes generally range from 0.17 to 0.70 in sheep, pigs, cows and fish (Juengel et al, 2019;Kavlak & Uimari, 2019;Moretti, de Rezende, Biffani, & Bozzi, 2018;Vargas Jurado, Leymaster, Kuehn, & Lewis, 2016). However, in order to select traits with low heritability values, the method of genomic selection is already used for livestock animals (e.g.…”

Consistent variations in personality traits and their potential for genetic improvement in biocontrol agents: Trichogramma evanescens as a case study

“…As a comparison, breeding programmes for livestock animals generally make use of traits with higher heritability. Heritability values for morphological, physiological, behavioural or other traits linked to fitness and considered in these breeding programmes generally range from 0.17 to 0.70 in sheep, pigs, cows and fish(Juengel et al, 2019;Kavlak & Uimari, 2019;Moretti, de Rezende, Biffani, & Bozzi, 2018; Vargas Jurado, Leymaster, Kuehn, & Lewis, 2016). However, in order to select traits with low heritability values, the method of genomic selection is already used for livestock animals (e.g Hayes, Bowman, Chamberlain, & Goddard, 2009)…”