Genetic importance of fat and eye muscle depth in Merino breeding programs
D. J. Brown A B and A. A. Swan AA Animal Genetics and Breeding Unit*, University of New England, Armidale, NSW 2351, Australia.
B Corresponding author. Email: dbrown2@une.edu.au
Animal Production Science 56(4) 690-697 https://doi.org/10.1071/AN14645
Submitted: 19 June 2014 Accepted: 10 September 2014 Published: 7 July 2015
Abstract
Australian Merino breeders have traditionally selected animals for breeding predominately on the basis of wool characteristics. Over recent decades, an increasing proportion of Merino breeders are interested in producing a ewe that can be used for prime-lamb production, but that also performs well for wool characteristics. Correlations between ultrasound carcass traits and other traits such as wool, internal parasite resistance and reproduction traits, are not very well known. The aims of this study were three-fold: (1) to estimate the genetic relationships between ultrasound carcass traits and wool, internal parasite resistance and reproduction traits, (2) to determine the value of recording ultrasound carcass traits in Merino breeding programs, and (3) to evaluate the impact of improving ewe genetic merit for fatness on their reproduction performance. Ultrasound fat and eye muscle depth had small to moderate genetic correlations with most traits, with positive correlations observed for bodyweight, fibre diameter, fibre curvature and reproduction, and negative correlations observed for fleece weight, fibre diameter coefficient of variation, worm egg count and breech wrinkle. As expected on the basis of these genetic correlations, estimated breeding values for fat depth of ewes had a positive association with their observed reproduction performance, but the effect explained only minimal variation in reproductive performance, and was extremely variable among flocks and years. A range of measurement scenarios was investigated for three standard MERINOSELECT indexes. Measuring fat and eye muscle depth resulted in 3%, 4% and 21% additional economic index gain for the fine, medium and dual purpose indexes, respectively, whereas measuring reproduction traits directly resulted in 17%, 27% and 45% additional gain in the economic index. Dual purpose index gains benefited more from measuring ultrasound carcass traits as it is the only index with a direct economic value placed on carcass traits. Measuring fat and eye muscle depth also resulted in a greater reduction in worm egg count. The results indicated that desirable genetic progress can be made in wool, ultrasound carcass, internal parasite resistance and number of lambs born and weaned simultaneously using multiple trait selection to account for the mix of favourable and unfavourable correlations between these traits. These results also demonstrated that the best method to maximise economic gain is to measure as many traits (or closely correlated traits) in the breeding objective as possible.
Additional keywords: genetic relationships, internal parasite resistance, Merino sheep, reproduction, ultrasound carcass traits, wool.
References
Ap Dewi I, Saatci M, Ulutas Z (2002) Genetic parameters of weights, ultrasonic muscle and fat depths, maternal effects and reproductive traits in Welsh Mountain sheep. Animal Science 74, 399–408.Brown DJ, Huisman AE, Swan AA, Graser H-U, Woolaston RR, Ball AJ, Atkins KD, Banks RB (2007) Genetic evaluation for the Australian sheep industry. Proceedings of the Association for the Advancement of Animal Breeding and Genetics 17, 187–194.
Brown DJ, Swan AA, Gill JS (2010) Within- and across-flock genetic relationships for breech flystrike resistance indicator traits. Animal Production Science 50, 1060–1068.
| Within- and across-flock genetic relationships for breech flystrike resistance indicator traits.Crossref | GoogleScholarGoogle Scholar |
Brown DJ, Swan AA, Gill JS, Banks RB (2013) Strategies to objectively group Merino flocks in Sheep Genetics. Proceedings of the Association for the Advancement of Animal Breeding and Genetics 20, 66–69.
Bunter KL, Brown DJ (2013) Yearling and adult expressions of reproduction in maternal sheep breeds are genetically different traits. Proceedings of the Association for the Advancement of Animal Breeding and Genetics 20, 82–85.
Ferguson MB, Young JM, Kearney GA, Gardner GE, Robertson IRD, Thompson AN (2010) The value of genetic fatness in Merino ewes differs with production system and environment. Animal Production Science 50, 1011–1016.
| The value of genetic fatness in Merino ewes differs with production system and environment.Crossref | GoogleScholarGoogle Scholar |
Gilmour AR, Gogel BJ, Cullis BR, Welham SJ, Thompson R (2009) ‘ASReml user guide release 3.0.’ (VSN International Ltd: Hemel Hempstead, UK)
Greeff J, Safari E, Fogarty NM, Hopkins DL, Brien FD, Atkins KD, Mortimer SI, van der Werf JHJ (2008) Genetic parameters for carcass and meat quality traits and their relationships to liveweight and wool production in hogget Merino rams. Journal of Animal Breeding and Genetics 125, 205–215.
| Genetic parameters for carcass and meat quality traits and their relationships to liveweight and wool production in hogget Merino rams.Crossref | GoogleScholarGoogle Scholar | 1:STN:280:DC%2BD1czhslejtg%3D%3D&md5=efdefb81d5df60e5cd2947925e06b36aCAS | 18479272PubMed |
Huisman AE, Brown DJ (2008) Genetic parameters for body weight, wool, and disease resistance and reproduction traits in Merino sheep: 2. Genetic relationships between body weight traits and other traits. Australian Journal of Experimental Agriculture 48, 1186–1193.
| Genetic parameters for body weight, wool, and disease resistance and reproduction traits in Merino sheep: 2. Genetic relationships between body weight traits and other traits.Crossref | GoogleScholarGoogle Scholar |
Huisman AE, Brown DJ (2009) Genetic parameters for bodyweight, wool, and disease resistance and reproduction traits in Merino sheep. 3. Genetic relationships between ultrasound scan traits and other traits. Animal Production Science 49, 283–288.
| Genetic parameters for bodyweight, wool, and disease resistance and reproduction traits in Merino sheep. 3. Genetic relationships between ultrasound scan traits and other traits.Crossref | GoogleScholarGoogle Scholar |
Huisman AE, Brown DJ, Ball AJ, Graser H-U (2008) Genetic parameters for weight, wool, and disease resistance and reproduction traits in Merino sheep: 1. Description of traits, model comparison, variances and their ratios. Australian Journal of Experimental Agriculture 48, 1177–1185.
| Genetic parameters for weight, wool, and disease resistance and reproduction traits in Merino sheep: 1. Description of traits, model comparison, variances and their ratios.Crossref | GoogleScholarGoogle Scholar |
Mortimer SI, Swan AA, Brown DJ, van der Werf JHJ (2014) Genetic parameters revisited for ultrasound scanning traits in Australian sheep. In ‘Proceedings 10th world congress of genetics applied to livestock production’, Vancouver, Canada, August 2014.
Newton JE, Brown DJ, Dominik S, van der Werf JHJ (2014) Genetic and phenotypic parameters between yearling, hogget and adult reproductive performance and age of first oestrus in sheep. Animal Production Science 54, 753–761.
| Genetic and phenotypic parameters between yearling, hogget and adult reproductive performance and age of first oestrus in sheep.Crossref | GoogleScholarGoogle Scholar |
Safari E, Fogarty NM, Gilmour AR (2005) A review of genetic parameter estimates for wool, growth, meat and reproduction traits in sheep. Livestock Production Science 92, 271–289.
| A review of genetic parameter estimates for wool, growth, meat and reproduction traits in sheep.Crossref | GoogleScholarGoogle Scholar |
Safari E, Fogarty NM, Gilmour AR, Atkins KD, Mortimer SI, Swan AA, Brien FD, Greeff JC, van der Werf JHJ (2007) Genetic correlations among and between wool, growth and reproduction traits in Merino sheep. Journal of Animal Breeding and Genetics 124, 65–72.
| Genetic correlations among and between wool, growth and reproduction traits in Merino sheep.Crossref | GoogleScholarGoogle Scholar | 1:STN:280:DC%2BD2s3nvVCrsw%3D%3D&md5=6d4366f3ee82e51766434249130414daCAS | 17488356PubMed |
Sheep Genetics (2014) ‘MERINOSELECT indexes.’ (Sheep Genetics: Armidale, NSW) Available at http://www.sheepgenetics.org.au/Getting-started/ASBVs-and-Indexes/MERINOSELECT-Indexes [Verified 22 September 2014]
Swan AA, Brown DJ, van der Werf JHJ (2016) Genetic variation within and between subpopulations of the Australian Merino breed. Animal Production Science 56, 87–94.
| Genetic variation within and between subpopulations of the Australian Merino breed.Crossref | GoogleScholarGoogle Scholar |
Young JM, Thompson AN, Curnow M, Oldham CM (2011) Whole-farm profit and the optimum maternal liveweight profile of Merino ewe flocks lambing in winter and spring are influenced by the effects of ewe nutrition on the progeny’s survival and lifetime wool production. Animal Production Science 51, 821–833.
| Whole-farm profit and the optimum maternal liveweight profile of Merino ewe flocks lambing in winter and spring are influenced by the effects of ewe nutrition on the progeny’s survival and lifetime wool production.Crossref | GoogleScholarGoogle Scholar |
