The estimation of variance components for prolificacy and growth traits of Sakız sheep

Abstract

The aim of the current study was to investigate the fix effects which are considered to influence ewe prolificacy, growth traits and to estimate genetic parameters for fertility, litter size at birth (LSB) and litter size at weaning (LSW), survival rate (SR), birth weight (BW), weaning weight (WW), yearling weight (YLW), average daily gain from birth to weaning (ADG) of Sakız sheep. Data and pedigree information of Sakız sheep used in this study were collected at the Marmara Animal Livestock Research Institute from 2001 to 2008. Estimates of genetic parameters were obtained by the use of DFREML package programs. The material ewe was classified according to birth year (8), age of ewe at lambing (6). The lamb material was classified year, age of dam, birth type and sex. The effects of years and ages of ewe were not significant for fertility (P > 0.05), litter size at birth (LSB), but the year effect was significant for LSW (P < 0.05). The effects age of ewes, sex and birth types of lambs were significant (P < 0.05, P < 0.01 and P < 0.001) of birth weight (BW), weaning weight (WW), yearling live weight (YLW) and average daily gain (ADG) of Sakız sheep.

Estimates of heritability were 0.035 for LSB, 0.189 for LSW, 0.163 for survival rate, 0.188 for BW, 0.174 for WW, 0.148 for YLW and 0.251 for ADG, respectively.

Introduction

The Sakız breed, in particular, may play an important role in the sheep production of Turkey in producing prolific and milky crossbred dams through crossbreeding with other native breeds. The best breeding policy in Sakız breed in the future will be keeping their purity and improving their production characteristics through selection. Sakız is the Turkish name for the Greek island of Chios in the Aegean Sea. The Chios breed of Greece and Sakız breed of Turkey is probably the same breed. The Sakız breed is also called Çeşme in Turkey. Management of Sakız sheep is quite different from the other sheep breed. Sakız sheep are kept in groups of 2–6 animals to supply meat and milk required by individual families (Yalçin, 1986). The largest flock in Turkey (150 heads) is being kept in Bandırma Marmara Livestock Research Institute.

The Sakız has a high milk yield and an outstanding prolificacy. Average live weight of Sakız sheep was found to be 40–45 kg for body weight, 4.6–3.4 kg for birth weight, 18.9–24.9 kg for 3 months, 32.6–46.2 kg for yearling weight, 76.6–88.8% for lamb survival rate, 58–180 kg for lactation milk yield and 1.7–2.3 for liter size reported by Özcan (1965), Ceyhan et al. (2007), Çörekçi and Evrim, 2000, Çörekçi and Evrim, 2001.

Efficiency of lamb production is controlled by reproduction, mothering ability and milk production of the ewes, as well as growth rate and survival of the lamb (Rao and Notter, 2000). Profitability of sheep production for meat depends to a great extent of lamb weight, so the selection objectives must concentrate on growth traits (Tosh and Kemp, 1994).

The estimates of direct heritability for prolificacy and lamb weight traits in literatures have ranged from 0.03 to 0.18 for litter size at birth, 0.13 to 0.18 for litter size at weaning (Abdulkhaliq et al., 1989, Hanford et al., 2006, Ekiz et al., 2005, Ligda et al., 2000, Hanford et al., 2003, Notter and Hough, 1997, Hagger, 2002), and 0.00 to 0.18 for survival rate (Abdulkhaliq et al., 1989, Long et al., 1989, Wyk et al., 2003, Fogarty, 1995). Reported estimates direct heritability for different sheep breeds range from 0.00 to 0.38 for lamb birth weight, 0.025 to 0.49, for weaning weight (Babar et al., 2003, Bahreini, et al., 2007, Duru and Koyuncu, 2005, Hanford et al., 2006, Ligda et al., 2000, Maria et al., 1993, Carrillo and Segura, 1993, Hanford et al., 2003 Nakagawa et al., 2005; Notter and Hough, 1997, Ozcan et al., 2005, Reale et al., 1999, Sawalha et al., 2005, Szwaczkowski et al., 2006, Tosh and Kemp, 1994, Wuliji et al., 2001, Wyk et al., 2003) and 0.12 to 0.25 for yearling weights (Reale et al., 1999, Ozcan et al., 2005), and 0.11 to 0.33 for average daily gain (Carrillo and Segura, 1993, Maria et al., 1993, Notter and Hough, 1997, Ozcan et al., 2005).

Sakız is one of the most important sheep breeds with milk and litter size in the world. But this breed is faced to extinction as other native breeds nowadays. That is why Ministry of Agriculture and Rural Affairs has started Turkey native animal genetic resources conversation project since 1985.

One of the objectives of this study was to estimate variance component due to direct genetic effects and permanent maternal genetic effects for ewe prolificacy and lamb growth traits using an animal model with data from purebred Sakız ewe. Another objective of our study was to complete the information on genotype characteristics to help Turkish conservation programs on native animal genetic resources.