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ABSTRACT
Mating between closely related (than the average of population) individuals is termed as inbreeding and is unavoidable in commercial breeding programmes in dairy cattle. Consequences of inbreeding include genetic drift, loss of hetrozygosity, and decrease in genetic variance. In breeding coefficients were estimated through using a total of 7345 pedigree records of Sahiwal cattle maintained at 6 institutional herds viz. LES, Jahangirabad (Khane wal), Khizerabad (Sargodha), Bahadurnagar (Okara), Kalurkot (Bhakar), Fazilpur (Rajanpur) and Shergarh (Okara) of Punjab province of Pakistan from year of birth 1973 to 2007. The overall inbreeding coefficient of all animals was 0.56%. Total 766 (10 sires and 756 cows) animals (10.43%) were found inbred. The average inbreeding coefficient amongst inbred animals was 5.33%. Maximum average inbreeding coefficient (25%) was observed in the herds maintained at Kalurkot, Fazilpur and Shergarh having relative small population size. It was followed by Jahangirabad and Khizerabad, while the lowest value of IBC was at Bahadurnagar with the highest number of animals inbred. Minimum (2.48%)IBC was found in the cows born during 1996 with 34 number of cows. The maximum 68 inbred cows were observed in the birth year, 2001.
Key words: Inbreeding Coefficient, Sahiwal cattle.
INTRODUCTION
Inbreeding occurs when animals mated to each other have common ancestors and is unavoidable in commercial breeding programmes in dairy cattle. Consequences of inbreeding include genetic drift, loss of hetrozygosity, and decrease in genetic variance (Hinrichs and Thaller, 2011). The knowledge of genetic variability within populations has received increasing attention over recent years (Wooliams et al, 2002). In populations under selection pressure, the inbreeding within the progeny of reproducing individuals can be higher than that expected under pure genetic drift. On the other hand, the goal in conservation programmes for endangered breeds is to restrain the rate of inbreeding. Considering both selection and conservation, some simple demographic parameters have a large impact on the evolution of the genetic variability and largely depend on the management of the population (Gutiérrez et al, 2003; Goyache et al, 2003). Zebu cattle flourish well under tropical environments where as Sahiwal dairy cattle breed is known to be the best amongst Zebu cattle breeds due to relatively high milk producing ability, resistance against tropical diseases like ticks and heat tolerant and more...