The effects of inbreeding in a flock of Hampshire sheep Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/r781wk11q

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  • A registered flock of Hampshire sheep that had been predominantly closed for approximately 30 years was utilized to study the effects of inbreeding on productivity of the 1980 and 1981 lamb crops. Five generation pedigrees for ewes and rams were used to calculate inbreeding coefficients. The median inbreeding coefficient of 598 lambs was 10.7% and coefficients ranged from 1.4 to 29.6%. The median inbreeding coefficient of 212 ewes was 4.3% and coefficients ranged from 0.0 to 28.1%. Regression techniques were used to determine the effects of ewe inbreeding on six month fleece weight and ewe breeding weight and the effects of ewe and lamb inbreeding on days from ram introduction to conception, fertility, prolificacy, lamb survival to 7 and 90 days, weight of lamb at birth, 30, 60 and 90 days and weight of lamb weaned per ewe exposed. A one percent increase in lamb inbreeding reduced (P<.01) survival to 7 days by 1.1%, reduced (P<.01) survival to 90 days by 1.3% and reduced (P<.05) weight of lamb weaned per ewe exposed by .59 kg. A one percent increase in ewe inbreeding decreased (P<.10) ewe breeding weight by .27 kg, increased (P<.10) days from ram introduction to conception by .35 days and decreased (P<.05) fertility by .56%. The effect of ewe inbreeding on six month fleece weight and of lamb and ewe inbreeding on prolificacy and lamb weight at birth, 30, 60 and 90 days were not significantly different from zero. Weight of lamb weaned per ewe exposed was composed of fertility, prolificacy, lamb survival to 90 days and 90 day weight. Using the percentage deviation method the negative effect of lamb inbreeding on weight weaned per ewe exposed was attributed as follows: 11% to its effect on fertility, 6% to its effect on prolificacy, 80% to its effect on survival and 3% to its effect on 90 day weight.
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