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ABSTRACT. The data set for estimation of genetic and phenotypic parameters of reproductive traits in Kordi sheep were collected from 1996 to 2013. The reproductive traits included age at first lambing (AFL), number of lambs born (NLB/EL) and weaned (NLW/EL) per ewe in each lambing, total weight of lambs born (TWLB/EL) and weaned (TWLW/EL) per ewe in each lambing, total number of lambs born (TNLB) and weaned (TNLW) per ewe, total weight of lambs born (TWLB) and weaned (TWLW) per ewe. The genetic parameters were estimated through restricted maximum likelihood method using WOMBAT. The effects of environmental factors (year of lambing, type of birth, maternal age at lambing) on all reproductive traits were significant (p < 0.01). Direct heritability, maternal heritability and the ratio of maternal permanent environmental variance to phenotypic variance for reproductive traits were estimated in the range from 0.07 to 0.18, 0.03 to 0.08 and 0.01 to 0.03, respectively. Genetic and phenotypic correlations between reproductive traits were estimated to be positive and within the range of 0.09 to 0.96 and 0.02 to 0.29, respectively. The results suggest that selection based on number of lambs born per ewe can be more effective than other traits in improving reproductive performance in Kordi ewes.Keywords: heritability, direct and maternal effect, genetic and phenotypic correlation, animal models.Estimativas de parâmetros genéticos e fenotípicos para características reprodutivas em ovinos Kordi nativos do Irã RESUMO. O conjunto de dados para a estimativa de parâmetros genéticos e fenotípicos de características reprodutivas em ovinos Kordi foi coletado de 1996 a 2013. As características reprodutivas incluíram idade ao primeiro parto, número de cordeiros nascidos e desmamados por ovelha em cada parição, peso total de cordeiros nascidos e desmamados por ovelha em cada parição, número total de cordeiros nascidos e desmamados por ovelha, peso total de cordeiros nascidos e desmamados por ovelha. Os parâmetros genéticos foram estimados pelo método de máxima verossimilhança restrita usando WOMBAT. Os efeitos dos fatores ambientais (ano de parto, tipo de nascimento, idade materna de parição) em todas as características reprodutivas foram significativos (p < 0,01). A herdabilidade direta, a herdabilidade materna e a razão entre variância ambiental permanente materna e variância fenotípica para características reprodutivas foram estimadas na faixa de 0,07 a 0,18; de 0,03 a 0,08 e de 0,01 a 0,03, respectivamente. As correlações genéticas e fenotípicas entre as características reprodutivas foram estimadas como sendo positivas e na faixa de 0,09 a 0,96 e de 0,02 a 0,29, respectivamente. Os resultados sugerem que a seleção baseada no número de cordeiros nascidos por ovelha pode ser mais eficaz do que outras características para melhorar o desempenho reprodutivo em ovelhas Kordi.Palavras-chave: hereditariedade, efeito direto e materno, correlação genética e fenotípica, modelos animais.

Data collected on 2550 Kurdi lambs originated from 1505 dams and 149 sires during 1991 to 2015 in Hossein Abad Kurdi Sheep Breeding Station, located in Shirvan city, North Khorasan province, North-eastern area of Iran, were used for inferring causal relationship among the body weights at birth (BW), at weaning (WW), at six-month age (6MW), at nine-month age (9MW) and yearling age (YW). The inductive causation (IC) algorithm was employed to search for causal structure among these traits. This algorithm was applied to the posterior distribution of the residual (co)variance matrix of a standard multivariate model (SMM). The causal structure detected by the IC algorithm coupling with biological prior knowledge provides a temporal recursive causal network among the studied traits. The studied traits were analyzed under three multivariate models including SMM, fully recursive multivariate model (FRM) and IC-based multivariate model (ICM) via a Bayesian approach by 100,000 iterations, thinning interval of 10 and the first 10,000 iterations as burn-in. The three considered multivariate models (SMM, FRM and ICM) were compared using deviance information criterion (DIC) and predictive ability measures including mean square of error (MSE) and Pearson's correlation coefficient between the observed and predicted values (r(y, )) of records. In general, structural equation based models (FRM and ICM) performed better than SMM in terms of lower DIC and MSE and also higher r(y, ). Among the tested models ICM had the lowest (36678.551) and SMM had the highest (36744.107)DIC values. In each case of the traits studied, the lowest MSE and the highest r(y, ) were obtained under ICM. The causal effects of BW on WW, WW on 6MW, 6MW on 9MW and 9MW on YW were statistically significant values of 1.478, 0.737, 0.776 and 0.929 kg, respectively (99% highest posterior density intervals did not include zero).

This study was conducted to compare the carcass characteristics and quantity of carcass and non-carcass components of 2- and 3-year-old male camels fattened for either 3 or 6 months. Twelve 2-year-old camels with an average body live weight of 268.5 ± 21.4 kg and twelve 3-year-old camels with an average body live weight of 307.5 ± 29.9 kg were used in a completely randomized design with a 2 × 2 factorial arrangement. For carcass analysis, three camels from each group were selected and slaughtered. The results showed that camel age and fattening period had no significant effect on average daily gain (ADG). Older camels and a longer fattening period resulted in heavier hot and cold carcass weights. Three-year-old camels had a higher dressing percentage compared to 2-year-old camels, regardless of the period of fattening. Analysis of non-carcass components showed that the heaviest component was the hide and 2-year-old camels fattened for 90 days had the greatest weight of hide as percentage of cold carcass weight. Total muscle weight was greater for the 3-year-old camels compared to the 2-year-old ones, regardless of the fattening period, and camels fattened for 180 days had heavier weight than those fattened for 90 days, regardless of age at fattening. However, the greatest weight of total muscle was detected in camels at 2 years of age fattened for 180 days when it was expressed as percentage of carcass weight. The highest and the lowest total fat content as kilogram or as percentage of cold carcass was observed in 3-year-old camels fattened for 180 days and 2-year-old camels fattened for 180 days, respectively. Our results suggested that the best age for slaughtering is 2 years old with the fattening period of 180 days.