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This study aimed to evaluate the growth performance and Kleiber ratio (KR) and to determine the growth curve of Dorper × Tumele sheep under a smallholder management system. Growth and efficiency-related traits were analyzed by using the general linear model (GLM) procedure of SAS. Gompertz, Logistics, Brody, Monomolecular, and Negative exponential models were used to determine the growth curve, and growth curve parameters were estimated via the nonlinear regression model (NLIN) procedure of SAS. The overall least-squares means of the birth weight, weaning weight, 6-month weight, and yearling weight were 3.29, 13.7, 17.3, and 23.4 kg, respectively. Dorper × Tumele lambs grew faster during the preweaning period (115.3 ± 1.19 g day−1) than during the postweaning periods (44.1 ± 1.26 g day−1 to 33.5 ± 1.13 g day−1). Likewise, a higher KR was observed during the pre-weaning age (16.1 ± 0.08 g/day/kg0.75) than during postweaning periods (5.08 ± 0.13 g/day/kg0.75 to 3.10 ± 0.09 g/day/kg0.75). Brody, a model without an inflection point was the best-fitted growth function for Dorper × Tumele sheep under a smallholder management system. The highest and lowest asymptotic weight was observed for Brody (23.8 ± 0.22 kg) and Logistics (20.7 ± 0.11 kg) models, respectively. The maturation rate ranged between 0.21 (Brody) and 0.66 (Logistics). Based on the Brody model, the correlation between asymptotic weight and maturity rate was −0.92. The growth parameter estimate in this study indicates that Dorper × indigenous sheep had a better speed to achieve mature weight and the early mature crossbred sheep are less likely to exhibit high adult weight. The rapid growth of crossbred sheep during the early period can provide more profit to the farmer by reducing the cost of sheep production inputs. Therefore, crossing Tumele with Dorper sheep and integrating with improved management would be suggested to improve productivity and profit from sheep production.

Accurate performance evaluation and genetic parameters estimation are the prerequisites for any successful genetic improvement program. This study was conducted to estimate genetic parameters for growth and Kleiber ratio traits in Boer x Central Highland goats. On-station data collected from 2009 to 2018 were utilized for the study. A general linear model procedure of the Statistical Analysis System (SAS, version 9.0) was used to analyze fixed effects, and genetic parameters were estimated using the WOMBAT software fitted animal model. The log-likelihood ratio test was used for selecting the best fitted model. Based on best fitted models, the total heritability (h2t) estimate for birth weight (BWT), weaning weight (WWT), six-month weight (SMWT), nine-month weight (NMWT), and yearling weight (YWT) were 0.38, 0.12, 0.05, 0.30, and 0.28, respectively. The total heritability (h2t) estimates for weight gain from birth to weaning (ADG1), 3 to 6 months (ADG2), 6 to 9 months (ADG3), and 9 to 12 months of age (ADG4) were 0.09, 0.08, 0.16, and 0.14, respectively. The heritability estimates for Kleiber ratios in different growth phases were found to be low (0.09 to 0.18) based on the selected models. Even with this figure, including the Kleiber ratio in the selection criteria would be imperative to improve the feed efficiency of crossbred goats. The direct genetic correlation estimates among growth traits range from 0.60 ± 0.14 to 0.97 ± 0.12. Except for NMWT, ADG4, and Kleiber ratio from 9 months to yearling age, the maternal effect had a significant influence on all considered traits. However, the contribution of the maternal genetic effect was more important for early growth traits. Thus, considering both the direct additive genetic effect and the maternal genetic effect is imperative for accurate genetic evaluation and for high selection response. The moderate heritability estimates for most of the growth traits implies the possibility of selection in conjunction with crossbreeding for a better genetic response. The positive and high genetic correlation estimates among growth traits confirm the possibility of a selection of goats at an early age.

Genetic improvement program will only be successful when accompanied by a good understanding of the influence of environmental factors, knowledge of the genetic parameters, and the genetic relationships between the traits of interest. Thus, this study aimed to evaluate the influence of non-genetic factors on growth traits and Kleiber ratios and to estimate genetic parameters for early growth traits in Dorper x indigenous sheep. The effects of fixed factors were analyzed by the general linear model procedure of SAS and the genetic parameters were estimated by AI-REML algorithm using a WOMBAT computer program fitted animal model. The log-likelihood ratio test was used for selecting the best-fitted model from four models. The overall least-squares means for birth weight (BW), weaning weight (3MW), six-months (6MW), nine-month (9MW), and yearling (12WT) were 3.03 ± 0.02, 14.5 ± 0.18, 20.4 ± 0.26, 24.8 ± 0.31, and 28.3 ± 0.40 kg, respectively. The overall least-square means for Kleiber ratio from birth to weaning (KR1), weaning to six-month (KR2), six to nine-month (KR3) and nine-month to yearling age (KR4) were 16.8 ± 0.10, 6.41 ± 0.17, 4.55 ± 0.21 and 3.38 ± 0.20 g/kg of metabolic weight, respectively. The inclusion of maternal genetic effect exerted a significant influence on BW and it explains 20% of the phenotypic variation. The total heritability (h2t) estimates for BW, 3MW, ADG1 and KR1 were 0.10, 0.14, 0.16 and 0.12, respectively. The phenotypic correlation varied from − 0.11 to 0.98 whereas the direct genetic correlation ranged from − 0.32 to 0.98. The mean inbreeding coefficient was 0.105% with annual rate of 0.02%. The heritability estimates for growth traits and Kleiber ratio suggests that slow genetic progress would be expected from the selection. However it is, integration of selection with crossbreeding program with this level of variation would enhance the genetic gain. Therefore, selection should be conducted based on breeding values estimated from multiple information sources to increases the selection response.

Genetic improvement programme will only be successful when accompanied by a good understanding of the influence of different environmental factors, knowledge of the genetic parameters and the genetic relationships between the traits of interest. This study aimed to evaluate the influence of non-genetic factors on growth traits and Kleiber ratios and to estimate genetic parameters for early growth traits in Dorper × indigenous crossbred sheep. The effects of fixed factors were analysed by the general linear model procedure of statistical analysis system, while the genetic parameters were estimated using a WOMBAT computer program fitted animal model. The overall least-square mean for birth weight (BRW), weaning weight (3MW), six-month weight, nine-month weight, and yearling weight were 3.03 ± 0.02, 14.5 ± 0.18, 20.4 ± 0.26, 24.8 ± 0.31, and 28.3 ± 0.40 kg, respectively. The overall least-square mean for Kleiber ratio from birth to weaning (KR1), weaning to six months, six to nine months and nine months to yearling age were 16.8 ± 0.10, 6.41 ± 0.17, 4.55 ± 0.21 and 3.38 ± 0.20 g/kg of metabolic weight, respectively. The inclusion of maternal genetic effect had a significant influence on BRW, and it explains 20% of the phenotypic variation. The total heritability estimates for BRW, 3MW, birth to weaning average daily weight gain and KR1 were 0.10, 0.14, 0.16 and 0.12, respectively. The phenotypic correlation varied from -0.11 ± 0.05 to 0.98 ± 0.02, whereas the direct genetic correlation ranged from -0.32 ± 0.40 to 0.98 ± 0.17. The mean inbreeding coefficient was 0.105% with an annual rate of 0.02%. The heritability estimates for growth traits and Kleiber ratio suggest that slow genetic progress would be expected from the selection. However, the integration of selection with crossbreeding programme can enhance genetic gain. Therefore, selection should be conducted based on breeding values estimated from multiple information sources to increase the selection response.

The objective of this study was to evaluate the growth and efficiency-related traits of the Boer x Central Highland goats. Besides, genetic and non-genetic factors affecting growth and efficiency-related traits (Kleiber ratios) were identified. Data were collected for nine years and a general linear model procedure of SAS was employed to detect the significance of fixed effects. The overall least-squares mean live weight at birth, 3-, 6-, 9- and 12 months of age were 2.52±0.01, 9.81±0.13, 13.8±0.15, 17.8±0.19, and 20.5±0.29 kg, respectively. The average weight gains from birth to 3 months, 3 to 6, 6 to 9 and 9 to 12 months of age were 80.3, 37.5, 41.9, and 31.2 g day-1, respectively. Exotic gene level, dam genotype, birth type, season and year of kidding had a significant effect on growth traits. The overall least-squares mean of Kleiber ratio from birth to 3 months, 3 to 6 months, 6 to 9 months, and 9 month to yearling age were 13.99±0.11, 5.23±0.14, 4.66±0.16, and 2.95±0.18 g/kg0.75, respectively. Parity, birth type, blood level, season and year of birth had a significant influence on the expression of efficiency-related traits (Kleiber ratios) in different growth phases. In terms of growth performance and efficiency-related traits, F2 and F3 crossbreds did not show any benefit over F1 crossbreds. Furthermore, increasing Boer blood level above 50% would be meaningless under the existing minimal input production system. Therefore, besides to improving the management of goats, producing the first filial generation would be ideal for medium to high input production systems.

Kid survival is very critical to be profitable in goat production. Thus, this study was conducted to identify genetic and non-genetic factors affecting the survival rate of Boer x Central Highland goat and to estimate genetic parameters for survival using linear animal and Weibull proportional hazard model. Data collected from the Sirinka goat breeding station were utilized for this study. Survival analysis was conducted with a Weibull proportional hazard model using Survival Kit version 6.1 software. The genetic parameters for survival traits were estimated using both Survival Kit fitted sire model and ASREML software fitted animal model with logit function. Four models for survival traits were fitted in order to optimize the model for each trait in the animal model. The log-likelihood ratio test was used for selecting the best-fitted model. The proportion of right-censored kids up to 3, 6 and 12 months of age was 77.8, 66.2 and 57.9 %, respectively. From the total death, about 73.1 % of death occurred up to 140 days of age. Gastrointestinal parasites, septicemia, pneumonia are the leading causes of death. Birth type, birth weight, dam breed and year of birth are the most important risk factors for kid mortality. Based on selected linear animal models, total heritability (h2t) estimates for the survival of kids at 3, 6 and 12 months of age were 0.006, 0.096 and 0.098, respectively. The maternal permanent environmental effect explains 6% of the phenotypic variation in survival up to weaning age. However, the impact of the maternal effect on post-weaning survival was found to be negligible. The genetic correlation between birth weight and survival to yearling age was 0.55 ± 0.15. The heritability estimates for survival at 3, 6 and 12 months of age from the Weibull proportional hazard model were 0.10, 0.13 and 0.18, respectively. As both pre- and post-weaning survival traits are economically important traits, including in the selection index of the breeding program would be paramount. Besides selection, using a local goat as a dam line and improving management in the flock would be an option to improve the survival of kids.

Productivity and profitability of sheep farming are highly influenced by lamb survival and ewe reproductive performance. Thus, this study was conducted to evaluate the survival and reproductive performance of crossbred sheep. Data collected from 2009 to 2018 from Sirinka sheep breeding stations were utilized for this study. Survival analysis was conducted by using Survival Kit 6.12 software with the Weibull model and the general linear model of SAS 9.0 was used to analyze reproductive traits. The overall mean survival rate of Dorper x Tumele crossbred lambs at 3, 6 and 12 months of age were 86.0, 76.6, and 67.9%, respectively. About 46.8% of mortality from the total death was observed during the first 120 days of life. Gastrointestinal parasites, pneumonia and septicemia were the major causes of lamb mortality. Birth weight, birth type, sex and year of lambing were the most important risk factors for survival of crossbred lambs. The overall least-squares means for litter size at birth, litter size at weaning, total litter weight at birth and total litter weight at weaning were 1.10 lambs, 0.94 lambs, 3.28 kg and 15.5 kg, respectively. Birth type, sex and year of lambing were the most determinants of ewe productive traits. Tumele and their crossbred sheep had good mothering ability necessary to successfully raise lambs to weaning. The current crossbreeding program which aims to improving growth performance had a positive influence on the survival rate of lambs. Improvement of environmental in the flock, special care for small lambs and indirect selection based on birth weight would lead to further survival improvement., Agricultural Science; Biological Sciences; Veterinary Medicine; Crossbreeding, fitness traits, genetic trend, heritability, risk factors.

Foot and mouth disease (FMD) is contagious, acute viral disease of all cloven-hoofed animals. The disease is endemic in Ethiopia and causes multiple outbreak every year all over the country. While it is important to understand to the transmission dynamics of FMD outbreaks for appropriate control intervention, no such study has been done in Ethiopia. Thus, the aims of this study were to estimate the basic reproduction number (R0) of FMD and simulate FMD transmission dynamics of FMD in Amhara region of Ethiopia. Basic reproduction number (R0) was estimated from age stratified sero-prevalence data through maximum likelihood estimation. A stochastic SIR (susceptible-infectious-recovered) compartmental FMD model was formulated and parameterized using literature and age stratified sero-prevalence field data. The R0 of FMD in the region was estimated to be 1.27 (95%CI: 1.20-1.34). The simulation of the SIR model showed only 24% (95% CI: 16-32%) of the infection introduced in the region caused major outbreaks. Out of the major outbreaks 25% of them tend to persist in the region. Major outbreaks cause 38.9% (95% CI: 38.8-39.1%) morbidity and 0.0019% (95% CI: 0.0018-0.0020%) mortality in cattle and the outbreaks stayed for an average of 690 days (95%CI: 655-727). Validation of the model prediction with farmer's field experience indicated a fairly similar result especially for the predicted morbidity caused by outbreaks. This study revealed low transmission of FMD within the Amhara region cattle population indicating not very high vaccination coverage is needed, if control through vaccination is envisaged at regional level. However, owing to several simplified assumptions made during the modeling, this conclusion should be taken cautiously.