Estimation of genetic parameters for growth traits and kleiber ratio in dorper sheep breed.

The study aimed to estimate genetic and phenotypic parameters for growth traits and Kleiber ratio in Dorper sheep breed. Data used in this study were collected over 12 years (2012-2023) at Debre Birhan Agricultural Research Center sheep research station in Ethiopia. Studied traits were body weights at birth (WT0), weaning (WT3), six month (WT6), and yearling (WT12) age; average daily gains from birth to weaning (ADG0-3), from weaning to six months (ADG3-6), from six months to yearling (ADG6-12); and Kleiber ratios from birth to weaning (KR1) and from weaning to six months (KR2). The (co)variance components were estimated with different animal models using Average Information Restricted Maximum Likelihood (AI-REML) procedure. The best-fitted model for each trait was determined using likelihood ratio tests. Phenotypic performance for WT3, WT6, WT12, ADG0-3 and ADG3-6 showed a decline trend at a rate of 0.216 kg, 0.794 kg, 0.671 kg, 2.601 g and 4.865 g over years respectively. However, WT3, WT6, WT12, ADG0-3 showed a positive genetic improvement trend at a rate of 0.029 kg, 0.043 kg, 0.049 kg and 0.257 g over years respectively. Year of birth had a significant effect (P < 0.001) on all studied traits. Model including direct genetic as well as permanent environmental effect (Model 2) was chosen as the most appropriate model for WT0. Model which included only direct genetic effect (Model 1) was the best-fit model for all other studied traits. Direct heritability estimates based on suitable models were 0.07 ± 0.06, 0.11 ± 0.06, 0.09 ± 0.07, 0.11 ± 0.09 0.11 ± 0.06, 0.00 ± 0.04, 0.15 ± 0.07 and 0.00 ± 0.04 for WT0, WT3, WT6, WT12, ADG0-3, ADG3-6, KR1 and KR2 respectively. The variance ratio for the permanent environmental effect was 0.13 ± 0.04 for WT0. Genetic correlations among the traits ranged from negative (-0.39) for WT0-KR1 to high (0.99) for WT3-ADG0-3 and phenotypic correlations ranged from negative (-0.31) for WT0-KR1 to high (0.98) for WT3-ADG0-3. The low direct heritability estimates for the studied traits indicated that genetic improvement by direct selection might be difficult. Further investigation for the unexpected declined trend of phenotypic performance over years need to be required.

Substitution of concentrate mixture with dried brewery spent grains improved biological and economical performance of 50% Dorper × Menz crossbred sheep.

The study aimed to investigate the potential of dried brewery spent grains (DBG) to substitute concentrate mixture (CM) in a diet of growing 50% Dorper × Menz crossbred ram lamb. Randomized complete block design (RCBD) was used for this study, and experimental animals were stratified into 7 blocks based on their initial body weight and age. Ram lambs from each block were randomly assigned to one of the five treatments. Native pasture hay (NPH) was fed to all experimental animals as a basal diet (ad libtum at 20% refusal) and supplemented with 400 g CM (T1) or 300 g DBG + 100 g CM (T2) or 200 g DBG + 200 g CM (T3) or 100 g DBG + 300 g CM (T4) or 400 g DBG (T5). Natural pasture hay and total dry matter (TDM) intake were not affected (P > 0.05) by the inclusion of DBG in the CM; however, supplement intake was greater (P < 0.0001) for DBG than CM alone-supplemented group. Metabolizable energy intake was decreased (P < 0.0001) as CM was substituted with DBG, whereas apparent digestibility was comparable (P > 0.05) among treatments. The treatments with the substitution of 50%, 75%, and 100% of CM with DBG were superior (P < 0.001) in body weight gain to the 100% CM-supplemented group, and the substitution of 25% CM with DBG had an intermediate growth rate. The partial budget analysis revealed that the substitution of 50% and 100% CM with DBG gave greater net returns of Birr 881.19 and 854.91 per head, respectively. Based on MRR, 200 g CM + 200 g DBG is the best treatment, and using this treatment, a farmer can benefit from ETB 8.94 for every 1 ETB investment. Hence, sole DBG or a mixture of DBG with a CM can be used for supplementation in growing 50% Dorper crossbred ram lambs.

Genetic evaluation of growth rate and efficiency-related traits in Dorper × local crossbred sheep population.

The present study was carried out to estimate genetic and phenotypic parameters for growth rate and efficiency-related traits in Dorper crossbred sheep population. Data on body weight collected from 2012 to 2021 at Debre Birhan Agricultural Research Center, Amhara Regional State, Ethiopia, were used to estimate phenotypic and genetic parameters for daily gain from birth to weaning (DG0-3), daily gain from weaning to 6 months (DG3-6), and daily gain from 6 months to yearling (DG6-12) and corresponding Kleiber ratios (KR0-3, KR3-6, KR6-12), efficiency of growth (GE0-3, GE3-6, GE6-12), and relative growth rate (RG0-3, RG3-6, RG6-12). Genetic parameters were estimated by restricted maximum likelihood (REML) procedure fitting six different univariate animal models and the most appropriate model for each trait was determined by log-likelihood ratio test. Multivariate analysis was carried out to estimate correlations between traits. Year and season of birth had a significant effect (p<0.001) in all studied traits. Direct heritability estimates for DG0-3, DG3-6, DG6-12, KR0-3, KR3-6, KR6-12, GE0-3, GE3-6, GE6-12, GR0-3, GR3-6, and GR6-12 were 0.45±0.15, 0.04±0.06, 0.15±0.11, 0.30±0.08, 0.13±0.11, 0.14±0.12, 0.34±0.15, 0.39±0.17, 0.31±0.14, 0.25±0.08, 0.23±0.13, and 0.23±0.13 respectively. Genetic correlation estimates between DG3-6 and other traits were positive and high in magnitude to their respective growth phase (0.95, 0.86, and 0.91 for KR3-6, GE3-6, and GR3-6 respectively). As the Dorper crossbred sheep are reaches market weight at about 6 months of age, focusing on improving traits measured during weaning to 6 months of age is more feasible. Selection based on DG3-6 is recommended to improve efficiency-related traits.

Coat color alterations over the years and their association with growth performances in the Menz sheep central nucleus and community-based breeding programs.

In the traditional Menz sheep breeding, communities select against black coat color and therefore its frequency is declining over time. We hypothesize that this exercise is causing the loss of an important gene pool. Data collected from on-station Menz sheep nucleus (n = 1992) and community-based breeding program (CBBP) (n = 5578) were analyzed to (1) assess color proportion dynamics over years and (2) associate phenotypic performances and estimated breeding values (EBVs) for growth traits with coat color of the animals. The on-station nucleus considered growth trait as selection criteria, while CBBP focused on a combination of growth and morphological characters. The results showed that the proportion of black coat color increased across years in the on-station nucleus flock (2.1% per year). However, in the CBBP, flocks' proportion of black coat color declined over time (1.03-1.05% per year). Birth and growth traits of black-colored sheep were consistently superior (P < 0.05) to white-colored sheep. Mean yearling weight and EBV of black rams used in the on-station flock was 24.3 kg and 3.7 kg, respectively, while the values for white-colored sheep were 19.7 kg and 1.6 kg, respectively. This variation in growth performances of Menz sheep among different colors may be due to the linkage between color and growth performance genes. Thus, selection against black coat color in the CBBPs seems to have an adverse effect on the genetic progress of growth traits in the Menz sheep. Understanding the core reasons behind the prevailing selection against black coat color and devising measures to address them should be considered. Developing a black line targeting specific markets might also be worthy to maximize production as well as maintain qualities associated with black color.