|HOLLAND, PAUL - Texas A&M University|
|HULSMAN-HANNA, LAUREN - North Dakota State University|
|VONNAHME, KIMBERLY - North Dakota State University|
|REYNOLDS, LAWRENCE - North Dakota State University|
|Taylor, Joshua - Bret|
|RILEY, DAVID - Texas A&M University|
Submitted to: Western Section of Animal Science Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 4/12/2017
Publication Date: 6/1/2017
Citation: Holland, P., Hulsman-Hanna, L.L., Vonnahme, K.A., Reynolds, L.P., Taylor, J.B., Riley, D.G. 2017. Estimation of genetic parameters and effects of birth type, sex, and age of dam on lamb mortality. Western Section of Animal Science Proceedings. 68:172-176. Available: https://www.asas.org/docs/default-source/western-section/asasws_western_book_060217.pdf?sfvrsn=e72946d1_0.
Technical Abstract: Lamb mortality has a significant impact on economic loss in the sheep industry. In this study, lamb mortality was evaluated two ways: 1) all mortality prior to weaning (i.e., preweaning mortality) and 2) mortality at birth (or when found). Mortality was evaluated assuming binomial distribution and logit link function using generalized linear mixed models. Bonferroni correction for multiple tests was applied for significance at a = 0.05 (a/ntests = 4.39 × 10-4). Males had greater (P < 0.001) preweaning mortality, but there was no sex difference detected for mortality at birth (P = 0.043). Preweaning lamb mortality was greater for very young ewes (1 year old), but mortality at birth was greater for both very young (1.5 years or less) and very old ewes (8 and 9 years old). The estimate of heritability for preweaning mortality was 0.123 ± 0.016, which was lower than mortality at birth: 0.241 ± 0.027. As a proportion of phenotypic variance, maternal additive genetic effects were 0.105 ± 0.020 and 0.082 ± 0.039 for preweaning mortality and mortality at birth, respectively. Furthermore, maternal permanent environmental effects were 0.025 ± 0.016 and 0.286 ± 0.032, and estimates of correlation of additive genetic-maternal additive genetic effects were -0.026 ± 0.140 and -0.344 ± 0.178. Preweaning mortality results were consistent with other similar work in sheep; however, mortality at birth results were quite different and merit additional exploration. Heritability estimate of additive genetic effects for mortality at birth were almost double the estimate for preweaning mortality. Genetic evaluation could be accelerated and selection implemented with more impact using breeding values for mortality at birth.