Level and effect of inbreeding in a flock of Horro sheep at Bako Research Center
2002
Solomon Abegaz (Ethiopian Agricultural Research Organization, Addis Abeba (Ethiopia))
Levels of inbreeding were calculated in a flock of Horro sheep kept at Bako Research Center during the period 1978-1997. Using regression methods, the effect of lamb and dam inbreeding level on weight at birth (BW), at weaning (WW), at six month (6MW) and one year (YW) of age, on survival to different ages (3 and 7 days and one, three, six and 12 months(and on litter size at birth were studied. Flock average inbreeding coefficient during the study increased to more than 2in the year 1991 and decreased thereafter. Proportion of inbred animals also increased to about 81. Regression of performance on inbreeding showed that 1increase in inbreeding coefficient of the lamb resulted in a decrease in weight of -4, 6, 31 and 103 g BW, WW, 6MW, and YW, respectively. Except for YW which approached significant level (p=0.06)all effects were not significant. A percent increase in inbreeding coefficient of the dam has also resulted in a decrease in BW, WW, 6MW, and YW of -1, -4, 33 and 33 g, respectively. All were not significant. The effect of individual and dam inbreeding on litter size at birth was also not significant (p0.05). Significant (p0.05) negative effect both individual and dam inbreeding was observed on survival to 30 days of age. Dam in breeding has also a significant (p0.05) effect on survival to yearling. Effects on survival to other growth stages were all non significant. Analysis from categorization of inbreeding levels indicated that higher levels of inbreeding are detrimental. In spite of the low level of inbreeding in the current study there are some significant and non-significant negative trends due to inbreeding. Thus it is advisable to avoid particularly higher levels of inbreeding.
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