The population parameters and age composition of ewes and rams in Khuzestan province sheep flocks

In order to estimate some population parameters in sheep flocks of Khuzestan province, information of 100 flocks from rural rearing systems with two breeds of Arabic and Lori-Bakhtiari sheep were used during the years 2017 - 2019. The data were collected through a questionnaire and interview with the farmers. Data was analyzed by SAS 9.1 software. The average of the number of breeding ewes, the number of breeding rams, duration of ram stay in the flock and ram to ewe ratio were achieved 173.67 heads, 9.56 heads, 5.96 years and 5.65%, respectively. Accordingly, the average of effective size and the rate of inbreeding of flocks were 34.9 heads and 3 percent per generation, respectively. In general, the results showed that the estimated effective size was less than the minimum size recommended by FAO (50 heads) for having less than 1 percent inbreeding per generation. So, it may result in having flocks with inbreeding rate which is 3 times more than the permissible rate. Increasing of inbreeding in the flocks can decrease production performance, reproductive performance and increase genetic abnormalities. Therefore, based on the estimated inbreeding rate for sheep flocks in the province (3 percent per generation), it is necessary to prevent further increasing in inbreeding rate and its negative consequences by training farmers about issues such as suitable ram to ewe ratio, supplying breeding rams from out of the flock and keeping rams in flock for a shorter period of time, as well as, using rotational mating scheme