|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: American Society of Animal Science Southern Section Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 2/16/2018
Publication Date: 3/11/2018
Citation: Holland, P.W., Hulsman-Hanna, L.L., Vonnahme, K.A., Reynolds, L.P., Taylor, J.B., Riley, D.G. 2018. Genetic Parameters for Lamb Mortality Associated with Pneumonia. American Society of Animal Science Southern Section Meeting. 96 Suppl S1:1.
Interpretive Summary: Not required.
Technical Abstract: High mortality in lambs has a significant impact on the sheep industry’s economics. Genetic parameters for mortality are typically evaluated as an overall mortality, but not due to a specific cause of death. Mortality due to pneumonia in lambs was evaluated using a generalized linear mixed model assuming a binomial distribution and a logit link function. Records from 1996 to 2005 (D1; n = 29,464) and 2006 to 2015 (D2; n = 18,375) were analyzed in distinct analyses to ensure convergence was met. Mortality from pneumonia accounted for approximately 1% of the records in both decades. Fixed effects investigated included lamb breed and dam breed (purebred and crossbred Columbia, Polypay, Rambouillet, and Targhee; n = 14), type of birth (single, twin, triplet, quadruplet or greater), sex (male or female), and age of dam (1, 2, 3 to 5, and 6 years and older). Random effects included additive genetic, maternal additive genetic, their covariance, and maternal permanent environment. Bonferroni correction for multiple test was applied for significance at alpha = 0.05 (alpha/n(tests) = 0.003). Breed of lamb and dam were not significant effects in either decade. In D1, mortality due to pneumonia was greater in triplets (0.0110 +/- 0.0089) than in singles (0.0063 +/- 0.0051; P = 0.002). No sex difference was detected in either decade (P > 0.003). Furthermore, lamb mortality from pneumonia was greater in yearling dams (0.0135 +/- 0.0109) than 2-yr-olds (0.0067 +/- 0.0054; P < 0.001), 3- to 5-yr-olds (0.0061 +/- 0.0049; P < 0.001), and dams 6 yr and older (0.0048 +/- 0.0039; P < 0.001) in D1. Similar patterns were observed in D2 for these same fixed effects. For D1 and D2, the estimates of heritability were 0.31 +/- 0.13 and 0.14 +/- 0.31, respectively. Estimates of maternal additive and maternal permanent environmental variances as proportions of the phenotypic variance were 0.01 +/- 0.15 for D1 and 0.10 +/- 0.36 for D2, and 0.14 +/- 0.14 for D1 and 0.09 +/- 0.33 for D2, respectively. Additive-maternal correlations were -0.81 +/- 3.54 for D1 and -0.76 +/- 1.49 for D2. Differences in heritability could be due to lack of breed types, changes in relatedness of the population across decades, as well as modification of lambing facilities.