Genetic parameters of body weight and ascites in broilers: effect of different incidence rates of ascites syndrome.

1. The objectives of the current study were to investigate the effect of incidence rate (5%, 10%, 20%, 30% and 50%) of ascites syndrome on the expression of genetic characteristics for body weight at 5 weeks of age (BW5) and AS and to compare different methods of genetic parameter estimation for these traits. 2. Based on stochastic simulation, a population with discrete generations was created in which random mating was used for 10 generations. Two methods of restricted maximum likelihood and Bayesian approach via Gibbs sampling were used for the estimation of genetic parameters. A bivariate model including maternal effects was used. The root mean square error for direct heritabilities was also calculated. 3. The results showed that when incidence rates of ascites increased from 5% to 30%, the heritability of AS increased from 0.013 and 0.005 to 0.110 and 0.162 for linear and threshold models, respectively. 4. Maternal effects were significant for both BW5 and AS. Genetic correlations were decreased by increasing incidence rates of ascites in the population from 0.678 and 0.587 at 5% level of ascites to 0.393 and -0.260 at 50% occurrence for linear and threshold models, respectively. 5. The RMSE of direct heritability from true values for BW5 was greater based on a linear-threshold model compared with the linear model of analysis (0.0092 vs. 0.0015). The RMSE of direct heritability from true values for AS was greater based on a linear-linear model (1.21 vs. 1.14). 6. In order to rank birds for ascites incidence, it is recommended to use a threshold model because it resulted in higher heritability estimates compared with the linear model and that BW5 could be one of the main components of selection goals.

Effects of dietary n-3 fatty acids and vitamin C on semen characteristics, lipid composition of sperm and blood metabolites in fat-tailed Moghani rams.

Sixteen fertile rams were randomly allotted to four groups and fed either of the four diets for 14 weeks: (1) control diet (COD) without fish oil (FO) and vitamin C (VC), (2) diet containing 2.5% FO (FOD), (3) diet containing 300 mg/kg DM VC (VCD), and (4) diet containing 2.5% FO and 300 mg/kg DM VC (FCD). Semen was collected at 14-d intervals from 1 April to 10 July (out of the physiologic breeding season in Iran). Semen volume and percentages of motile and progressively motile sperm were increased by FO and VC feeding. A significant interaction was also found between FOD and VCD on motility and progressive motility percentage (P<0.05). HOS-test and percentage of sperm with normal acrosome improved significantly by FO and VC. Rams fed FCD had better HOS-test and higher proportion of sperm with normal acrosome than rams in other groups (82.4 and 93.6%, respectively). Diets containing FO and FO and VC increased the proportion of docosahexaenoic acid in sperm (P<0.05). The activity of lactate dehydrogenase in the seminal fluid was significantly affected by VC and the interaction between FO and VC (P<0.05). Blood metabolites, except glucose, were affected positively by FO. The results showed that dietary supplementation with FO and VC improved seminal quality and may have beneficial effects on fertility in Moghani rams.