Location: Dale Bumpers Small Farms Research CenterTitle: Genetic parameters for ewe reproductive performance and peri-parturient fecal egg counts and their genetic relationships with lamb body weights and fecal egg counts in Katahdin sheep
|Ngere, Lauretta - Orise Fellow|
|Miller, James - Louisiana State University|
|Morgan, James - Katahdin Hair Sheep International|
|Notter, David - Virginia Tech|
Submitted to: Journal of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: 12/15/2017
Publication Date: 2/4/2018
Citation: Ngere, L., Burke, J.M., Miller, J.E., Morgan, J.L., Notter, D.R. 2018. Genetic parameters for ewe reproductive performance and peri-parturient fecal egg counts and their genetic relationships with lamb body weights and fecal egg counts in Katahdin sheep. Journal of Animal Science. 96 (E-Suppl. 1), 70.
Technical Abstract: Genetic parameters for ewe reproductive traits [number of lambs born (NLB) and number of lambs weaned (NLW)] and ewe peri-parturient rise (PPR) fecal egg counts (FEC) at lambing (PPR0) and at 30-d post lambing (PPR30), and their genetic relationships with lamb BW and FEC in Katahdin sheep were estimated. There were 20,204 ewes sired by 1,043 rams and born by 5,662 dams between 2007 and 2013 available for this study. There were 23,060 records of NLB and NLW from 9,295 ewes. For PPR0, 1,230 records were available from 750 ewes, and 1,070 records of PPR30 were available from 611 ewes. Animal models were employed to estimate genetic parameters for all traits in both univariate and bivariate analyses using ASReml. Random effects fitted were direct genetic, permanent environmental and residual. Fixed effects were ewe management group and ewe age for all traits, ewe birth type (for PPR0), ewe rearing type (for PPR30), and days post-lambing at first FEC collection and 30-d FEC for ewe fitted as covariates for both PPR0 and PPR30, respectively (all P < 0.05). Heritability estimates for NLB, NLW, PPR0 and PPR30 were 0.09 ± 0.01; 0.06 ± 0.01; 0.35 ± 0.06 and 0.24 ± 0.07, respectively. Estimates of permanent environmental variance as a proportion of total phenotypic variance were 0.02 ± 0.01 for NLB, 0.03 ± 0.01 for NLW, 0.05 ± 0.06 for PPR0, and 0.13 ± 0.07 for PPR30. Genetic, phenotypic, permanent environmental and residual correlations between NLB and NLW were 0.88 ± 0.03, 0.74 ± 0.004, 0.54 ± 0.15, 0.23 ± 0.003, respectively; and between PPR0 and PPR30 were 0.96 ± 0.07, 0.46 ± 0.03, 0.98 ± 0.50, 0.18 ± 0.05, respectively. Genetic correlations between ewe reproductive traits and PPR were low (0.11 to 0.14; SE = 0.13 to 0.19). Estimates of genetic correlation between ewe reproductive traits and their BW as lambs ranged from 0.07 to 0.20 with SE 0.12 to 0.18. The genetic association of PPR with lamb BW ranged from -0.03 to 0.29 with SE 0.15 to 0.22. Moderate (0.27 to 0.40) and high (0.56 to 0.77) genetic correlations were found between ewe reproductive traits and lamb FEC and between PPR and lamb FEC, respectively. Correlations between maternal genetic effects on BW and direct genetic effects on PPR were low (-0.08 to 0.10), while those between maternal genetic effects on BW and ewe reproductive traits were variable (-0.36 to 0.11).