Abstract
The examination was made on the effect of systematic factors (parturition group, calving season, birth type, calf gender, and birth type-calf gender interaction) and age at first conception on the expression of reproductive traits (gestation length, service period, fertility intensity and calf birth weight) in 143 Simmental cows. The overall mean (?) for gestation length, service period, intercalving period and calf birth weight was 284.14 days, 153.82 days, 416.92 days and 35.40 kg, respectively. The parturition group effect on all fertility traits was highly significant (P<0.01). The calving season statistically significantly (P<0.05) affected the intercalving period and calf birth weight. Birth type induced very significantly longer gestation (P<0.01) and higher calf birth weight in singles (P<0.01) and significantly longer service period in twins (P<0.05). Calf gender had a very significant effect (P<0.01) only on calf birth weight, and the interaction between birth type and calf gender significantly affected gestation duration only (P<0.05). The regression effect of age at first conception on all fertility traits was not significant (P>0.05).
Highlights
Introduction and Literature ReviewIn order to accurately assess the breeding value of certain individual cows in a population, it is necessary to examine the paragenetic factors affecting variability of phenotypic values, namely, of reproductive traits
The overall mean of the least square means corrected for the effect of the systematic factors examined was 284.14 days for gestation length, 153.82 days for the service period, 416.92 days for the intercalving period and 35.40 kg for calf birth weight
Calf gender did not bring about statistically significant differences (P>0.05) in gestation duration gestation was somewhat shorter in male calves, whereas the interaction between calf gender and birth type induced significant differences (P
Summary
In order to accurately assess the breeding value of certain individual cows in a population, it is necessary to examine the paragenetic factors affecting variability of phenotypic values, namely, of reproductive traits. The factors include, among others, calving sequence, calving season, calf gender, birth type and age at first conception. The effect of paragenetic factors on the expression of reproductive traits. Bogdanović, M.M. Petrović was investigated by Skalicki (1983), Burfening et al (1987), Fis and Wilton (1989), Perisic (1998 and 2002), Strapak et al (2000), Djurdjevic (2001), Bakir et al (2004), Petrovic D.M. et al (2004), Pantelic et al (2005) who concluded that the systematic effects significantly affected the phenotypic value of reproductive traits. The aim of the paper was to assess the factors affecting reproductive trait variability by analysing data on Simmental cows
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