Date of Award
Doctor of Philosophy
A total of 136,775 records from Holstein calvings were obtained from the National Association of Animal Breeders (NAAB). The objectives of this study were: (1) to characterize the sources of variation (genetic and environmental) affecting calf livability in Holsteins, (2) to determine its association with calving difficulty and the feasibility of sire evaluation for calf livability, (3) to estimate the genetic relationship between livability in first parturition dams (heifers) and subsequent parturition dams (cows), and (4) to estimate the genetic relationship between the contribution of the calf (direct effect) and the contribution of the dam (maternal effect) to calf livability. Sex of calf, parity of dam, linear and quadratic effects of gestation length had highly significant effects on calf livability. Calf mortality was greater for males (7.6%) than for females (5.6%). First parity dams showed 10.5% calf mortality versus 5.6% in later parities. Dead calves had 1.2 days shorter gestation length than live calves (279.6 days). A nonlinear relationship was found between calf mortality and size of calf, regardless of parity-of-dam and sex-of-calf effects. Calf mortality was greater at both extreme sizes of calf. Dystocia was a major effect associated with calf livability. Calf losses increased from about 3% for dams not experiencing dystocia to about 56% for those with calving difficulty scored as 5; only 1.74% of births were scored 5;Although a large difference in calf mortality was observed among sires (1% to 16%), heritability estimates were quite low. Heritability estimates were 1.02% for livability coded as (1) alive, (2) dead at birth and (3) dead by 48 hours, and 1.54% for livability coded as (1) alive, (2) dead. Using mixed model multitrait methodology, the genetic correlation between livability and calving difficulty was estimated to be 0.66. Heritability estimates through this methodology were 0.9% for calf livability and 4.1% for calving difficulty;Heritability estimate for calf livability in heifers (0.4%) was not different from zero. The estimate (0.6%) in cows was. The genetic correlation between calf livability in cows and heifers was 0.32;Maternal heritabilities (0.5% and 0.6%) were greater than the dam heritabilities (0.4 and 0.5%), respectively, for heifers and cows. Genetic correlations between maternal and direct effects were both -0.52 for heifers and cows.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Mario Luiz Martinez
Martinez, Mario Luiz, "Genetic and environmental effects on perinatal mortality in Holsteins " (1982). Retrospective Theses and Dissertations. 7514.