Abstract
The data base for body weights and growths of 411 Hamra lambs were used to estimate genetic parameters. These lambs were obtained from 31 rams and 493 ewes between 2012 and 2017. Traits analysed were weights at birth (BW), 30 days (W30), 90 days (W90) of age, and average daily gains from 10 to 30 (ADG10-30) and30-90 (ADG30-90) days. REML estimates of variance and covariance components were obtained assuming animal models that included the fixed effects for year-type of birth (2012 single, 2012 twin, . ., 2017 single, 2017 twin), sex (male, female), and ewes age at lambing (< 18, 18-30, 30-42, 42-54, >54 months). Heritabilities were 0.12, 0.06 and 0.11 respectively for BW, W3Oand W90and the average daily gains were 0.05 and 0.17 for ADG0-30and ADG30-90. The estimates of genetic correlations showed no genetic antagonisms among the growth traits. The genetic correlations estimated were positive and medium to high, except those between ADG30-90 and ADG0-30 and between ADG30-90 and W30 which were slightly negative. Phenotypic correlations were positive and ranged from 0.12 to 0.85. They were high between adjacent weights and between ADG and their corresponding weights.
Highlights
The small ruminants contribute substantially to the livelihoods and food security of rural Mediterranean farms in dry areas of the North Africa region (Bengoumi et al, 2013).because of instability of resources and inputs, climatic challenges, conflicts and security, livestock rearing in the marginal dry areas is challenged by low productivity and poor access to markets
The programs undertaken by government for the development of this genetic resources capital were confronted to a limited knowledge of the basic genetic material and the inexistence of in situ conservation strategies, as illustrated by the case of the reduction of more than 50 % for the Hamra sheep breed (Yerou, 1998, 2013).The Hamra or Daghma breed is native to eastern Morocco; its extension area is between ChottEch-Chergui in the east, of Saharian Atlas in the south-east, Morocco in the west and the Tlemcen and Saida mountains in the North
The analyses of variance showed that the fixed models explained 35to 51% of the phenotypic variances in all traits, and that effects of year-type of birth, the sex were important environmental sources of variation for all growth traits (p
Summary
The small ruminants contribute substantially to the livelihoods and food security of rural Mediterranean farms in dry areas of the North Africa region (Bengoumi et al, 2013).because of instability of resources and inputs, climatic challenges, conflicts and security, livestock rearing in the marginal dry areas is challenged by low productivity and poor access to markets. In order to achieve this genetic improvement, it is necessary to properly select the superior parents of future generations. For all this it is necessary a good knowledge of genetic parameters heritability, correlation, covariance and variance (Thompson et al, 2005).Otherwise knowledge of the genetic parameters for economically important traits of animals is necessary, is essential in order to evaluate the breeding values of individuals, made an effective plan and program breeding, and evaluate effects of selection. Despite its good conformation and excellent quality meat, the effect never ceases to regress. It was estimated at 6 million in 1969s more than 2.5 million head in the 1980s, is at present only about 0.5 million head.
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