Genetic and environmental effects on lambing and neonatal behaviour of Dormer and SA Mutton Merino lambs

Cloete, S.W.P.; Scholtz, A. J.; Gilmour, A.; Olivier, J.J.

doi:10.1016/s0301-6226(02)00117-3

Cited by 40 publications

(21 citation statements)

References 18 publications

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“…Estimates of total heritability for preweaning lamb survival in the current study were similar to those reported by Morris et al (2000;0.029) and Brien et al (2010;0.01). However, they were lower than that reported by Lopez-Villalobos and Garrick (1999;0.042), Everett-Hincks et al (2005;0.16, using a different dataset and model) and Cloete et al (2002;0.28). Reported estimates of the genetic compo nents of lamb survival indicate limited genetic variation (Petersson and Danell, 1985;Hall et al, 1995;Lopez-Villalobos and Garrick, 1999;Morris et al, 2000;Fadilli and Leroy, 2001;Cloete et al, 2002;, Safari et al, 2005 and that lamb survival is controlled mainly by nonadditive genetic factors.…”

Section: Discussionmentioning

confidence: 57%

Genetic parameters for lamb birth weight, survival and death risk traits 1

Everett-Hincks

Mathias-Davis

Greer

et al. 2014

Journal of Animal Science

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This paper reports genetic parameters for lamb survival and mortality traits on sheep farms in New Zealand. Lamb survival and mortality records were obtained from 38 flocks (103,357 lambs) from 5 yr of lambing data (2007 to 2011) and include many breeds and their crosses (predominantly Romney, Perendale, Coopworth, and Texel). A number of models were tested, all including environmental weather effects and investigating the random environmental effect of dam and litter (dam/year) as well as logit transformation for binary traits. Total heritability (direct + maternal) estimates were low for lamb viability at birth (0.01), lamb death risk to dystocia (0.01), and lamb death risk to starvation exposure (0.01) from birth to 3 d of age in an analysis accounting for direct and maternal genetic effects and the maternal environmental effects. Lamb survival heritabilities reported are very low (total heritabilities range from 0.02 to 0.06). The total heritabilities for the lamb death risk traits are lower than reported estimates of survival to 3 d of age or to weaning suggesting selection for the postmortem traits are not warranted at this time within these flocks. The total heritability for lamb birth weight was moderate (0.38) and the genetic correlations with the lamb death risk traits suggested that directional selection on lamb birth weight would have an effect on survival, although it is likely to have a nonlinear effect and therefore an optimum birth weight at which survival is maximized. This study has also shown that the total heritabilities may be overestimated when not accounting for maternal genetic and environment effects and in particular not accounting for the random environmental effect of litter (dam/year).

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Section: Discussionmentioning

confidence: 57%

Genetic parameters for lamb birth weight, survival and death risk traits 1

Everett-Hincks

Mathias-Davis

Greer

et al. 2014

Journal of Animal Science

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“…Tosh & Kemp, 1994;Al-Shorepy, 2001;Hassen et al, 2003), although significant correlations are not ubiquitous (e.g. Cloete et al, 2002). It has been suggested that this antagonism will limit the potential for genetic improvement of commercial flocks through artificial selection.…”

Section: Discussionmentioning

confidence: 99%

Maternal genetic effects set the potential for evolution in a free‐living vertebrate population

Wilson

Coltman

Pemberton

et al. 2004

J of Evolutionary Biology

186

221

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Heritable maternal effects have important consequences for the evolutionary dynamics of phenotypic traits under selection, but have only rarely been tested for or quantified in evolutionary studies. Here we estimate maternal effects on early‐life traits in a feral population of Soay sheep (Ovis aries) from St Kilda, Scotland. We then partition the maternal effects into genetic and environmental components to obtain the first direct estimates of maternal genetic effects in a free‐living population, and furthermore test for covariance between direct and maternal genetic effects. Using an animal model approach, direct heritabilities (h2) were low but maternal genetic effects (m2) represented a relatively large proportion of the total phenotypic variance for each trait (birth weight m2 = 0.119, birth date m2 = 0.197, natal litter size m2 = 0.211). A negative correlation between direct and maternal genetic effects was estimated for each trait, but was only statistically significant for natal litter size (ram = −0.714). Total heritabilities (incorporating variance from heritable maternal effects and the direct‐maternal genetic covariance) were significant for birth weight and birth date but not for natal litter size. Inadequately specified models greatly overestimated additive genetic variance and hence direct h2 (by a factor of up to 6.45 in the case of birth date). We conclude that failure to model heritable maternal variance can result in over‐ or under‐estimation of the potential for traits to respond to selection, and advocate an increased effort to explicitly measure maternal genetic effects in evolutionary studies.

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“…Within-breed studies indicate that ewe maternal behaviour may be affected by genotype even when that characteristic had not been included in the selection criteria [103][104][105]. For example, Merino ewes selected for superfine wool were less maternally responsive and had higher lamb mortality than broader wool Merinos [103].…”

Section: Selecting For Better Mothersmentioning

confidence: 99%

From birth to colostrum: early steps leading to lamb survival

2006

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-New-born lambs have limited energy reserves and need a rapid access to colostrum to maintain homeothermy and survive. In addition to energy, colostrum provides immunoglobulins which ensure passive systemic immunity. Therefore, getting early access to the udder is essential for the neonate. The results from the literature reviewed here highlight the importance of the birth site as the location where the mutual bonding between the mother and her young takes place. Attraction to birth fluids by the periparturient ewe leads to intense licking of the lamb. Grooming not only dries, cleans and stimulates the newborn it also facilitates bonding through learning of its individual odour. Ewes having twins should ideally stay on the birth site for at least six hours in order to establish a strong bond with both lambs and favour lambs survival. However, primiparous ewes or ewes having high levels of emotivity are more likely to exhibit poor maternal behaviour. In addition, difficult parturition and weather conditions have an indirect effect on the behaviour of the mother and are other major causes of lamb death. On the lamb's side, rapid access to the udder and early suckling are extremely important. Delayed lactation or insufficient colostrum yield may be fatal especially since suckling has strong rewarding properties in the establishment of a preference for the mother, which in turn increases lamb survival. Insufficient access to the udder in mothers leaving the birth site too soon after parturition, especially in twin-bearing ewes, could also partly account for the high incidence of loss of mother-young contact and subsequent death in such lambs. Strategies to improve neonatal survival should be aimed at maximising lamb vigour, colostrum production, and mutual mother-young bonding through adequate feeding in late pregnancy and selection on behaviour.energy reserve / colostrums / suckling / maternal behaviour / bonding / ewe / lamb / nutrition / survival

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Genetic and environmental effects on lambing and neonatal behaviour of Dormer and SA Mutton Merino lambs

Cited by 40 publications

References 18 publications

Genetic parameters for lamb birth weight, survival and death risk traits 1

Genetic parameters for lamb birth weight, survival and death risk traits 1

Maternal genetic effects set the potential for evolution in a free‐living vertebrate population

From birth to colostrum: early steps leading to lamb survival

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