Population genetic structure analysis and effect of inbreeding on body weights at different ages in Iranian Mehraban sheep

Abstract

The objective of this study was to describe the population structure and inbreeding, and to quantify their effects on weights at different ages of Mehraban sheep in Iran. The analysis was based on the pedigree information of 26990 animals and 10278 body weight records from birth to yearling age. Data and pedigree information were collected during 1994 to 2011 by the breeding station of Mehraban sheep. The population structure was analyzed using the CFC program. Inbreeding of all animals was calculated by INBUPGF90 program. All animals were grouped into three classes according to their inbreeding coefficients: the first class included non-inbred animals (F=0); and the second and third classes included inbred animals (0<F<0.05 and F≥0.05, respectively). The average inbreeding in Mehraban sheep was 1.69%. Founder equivalent (fe) values were estimated to be 4244, 3116 and 2965 during 1994-1999, 2000-2005 and 2006-2011, respectively. The effective population sizes (Ne) were 363, 5080 and 5740 during 1994-1999, 2000-2005 and 2006-2011, respectively. Generation interval was 2.15 years for this breed of sheep. Regression coefficients of birth weight, 3-month weight, 6-month weight and yearling weight on lamb inbreeding were estimated to be -6.34±0.69, -14.68±5.33, 48.00±9.43 and 98.65±15.65, respectively. Both positive and negative inbreeding effects were found in the current study. The utilization of a program for designed mating system, in the present flock, could be a suitable approach to keep the level of inbreeding under control.

Population genetic structure analysis of Shall sheep using pedigree information and effect of inbreeding on growth traits

“…Consistent with the low average coancestry between animals in this breed of sheep (0.0072%), Eteqadi et al (2014), Yavarifard et al (2014) and Rochus and Johansson (2017) reported low levels of coancestry in Guilan, Mehraban and Gute sheep breeds, respectively. The average coancestry coefficient could be applied for inbreeding coefficient prediction at subsequent generation; therefore, this parameter would be considered in animal breeding plans (Eteqadi et al 2014).…”

“…The average coefficients of inbreeding and coancestry were low in Shall sheep. Average inbreeding in this sheep breed (1.62%) was greater than the values reported for Guilan sheep (0.15%, Eteqadi et al 2014), Segureña sheep (0.60%, Barros et al 2017), Dorper sheep (0.32%, Kiya et al 2019) and Lori-Bakhtiari sheep (1.26%, Vatankhah et al 2019), but was lower than the average inbreeding rate in Moghani sheep (2.93%, Ghavi Hossein-Zadeh 2012a), Mehraban sheep (1.69%, Yavarifard et al 2014), Brazilian Morada Nova hair sheep (6.73%, McManus et al 2019), and French dairy sheep (2.34-3.11%, Rodr ıguez-Ramilo et al 2019). The range of inbreeding in the current sheep population (from 0 to 38%) indicated that some matings of close relatives happened, but the number of these types of matings was generally low.…”

“…Most breeding plans may attempt to minimise inbreeding accumulation and calculate the increase by measuring the new inbreeding or change in inbreeding per generation (DF) (Boichard et al 1997) in order to restrict the likely negative impact of inbreeding on different traits (Eteqadi et al 2014). A similar expanding trend for inbreeding was obtained by Barczak et al (2009), Ghavi Hossein-Zadeh (2012a), Eteqadi et al (2014), Yavarifard et al (2014), Kiya et al (2019) and Vatankhah et al (2019) in multi-breed sheep population, Moghani, Guilan, Mehraban, Dorper and Lori-Bakhtiari sheep breeds, respectively. The sharp and or irregular change of inbreeding in some years could result from the variations in the number of equivalent generations (Santana et al 2011;Ghavi Hossein-Zadeh 2016).…”

“…The Shall sheep, as a large-sized fat-tailed breed, is reared principally for meat production, but the sale of excess lambs is the principal source of income for breeders , 2015. There are different reports in the literature on the population genetic structure of sheep breeds (Pedrosa et al 2010;Ghavi Hossein-Zadeh 2012a;Eteqadi et al 2014;Yavarifard et al 2014;Barros et al 2017;Figueredo et al 2019;Kiya et al 2019;Vatankhah et al 2019), but there were no published reports of population structure analysis in Shall sheep. Therefore, the main objective of this study was to describe the population structure, genetic variability and inbreeding in Shall sheep of Iran using pedigree analysis.…”

Inbreeding affected differently on observations distribution of a growth trait in Iranian Baluchi sheep

“…Inbreeding depression emerging as a change in performance per unit of inbreeding increase is generally known as an initial consequence of inbreeding. Inbreeding depression degrades the growth, production, health, reproduction and survival traits [6,7,8,9]. Different breeds, populations and traits apparently vary in terms of their responses to inbreeding [5 and 10].…”