Document Type : Research Paper
Author
Department of Agriculture, Payame Noor University (PNU), Tehran, Iran.
Abstract
Keywords
Main Subjects
Extended Abstract
Introduction
The economic benefit of dairy cattle breeding units is a function of milk production volume, reproductive efficiency and herd health that various environmental and physiological factors such as nutrition, parity and offspring sex can play a role in the incidence of these traits. In order to sustainably maintain in the income of production units, breeders must create a proper balance between maximizing production and minimizing production costs. Various studies have shown that various environmental and physiological factors are effective on milk production in cows. Environmental factors can include nutrition, milking frequency, water consumption, season and heat stress. Also, other factors include animal genetics, parity, age, body condition score, nutrition level, animal health, and calf sex. In cattle, the effect of calf sex on economic traits is important from the financial and income aspects.
Research purpose
the main aim of this study was to investigate the effect of calf sex on production, reproductive and udder health traits in Isfahan Holstein cows.
Materials and Methods
In this research, the calving data of 37038 Holstein dairy cows belonging to 13 industrial herds located in Isfahan province during the years 2005 to 2017 were used. The information was including of production traits (milk, fat and protein 305 days, fat and protein percentage) and performance traits (the number of days from calving to first service, calving interval and somatic cell score). To ensure the normality of production data distribution, univariate procedure (Proc Univariate) was used. To investigate the effect of calf sex on the production and health traits, the mixed linear model procedure and on the reproduction traits, GLIMMIX procedure of SAS9.4 software were used.
Results Statistical analysis showed that the effect of the independent variables of parity and dystocia on all production and performance traits were significant (P<0.05). As well as, the effect of auxiliary variables of age of first calving, calf birth weight and length of dry period on production and reproduction traits were significant. (P<0.05). It was also found that the effect of the independent variable of calf sex, as well as the interaction effect of parity and calf sex were significant on studied traits, except for the traits of fat and protein production 305 days, calving interval and somatic cell score (P<0.05). The results showed that cows with female calf had higher 305-days of milk (90.7 kg) in compared to cows with male calf (P<0.01). For percentage of 305-d fat and protein and the number of days from calving to first service, the effect of calf sex different was low but significant (P<0.05). However, no significant difference was observed between male and female calves for traits of fat and protein production 305 days, calving interval and somatic cell score (P>0.05). The mechanism of milk production is a complex process that is influenced by many factors, including the type of diet and the amount of genetic potential. Also, the sex of the calf has a significant effect on the production of mother's milk. Various researches have shown that the concentration of sex hormones is different between male and female fetuses and can be potentially effective on increasing or decreasing milk production. Various reasons have been given for the decrease in milk production of mothers with the birth of a male calf. One reason is that carrying a larger calf during pregnancy causes more food to be distributed to the fetus and as a result reduces milk production. In this regard, the birth of a male calf can reduce the production of mother's milk during that lactation period. Also, among other main factors, we can mention the influence of calf sex on mother's hormonal levels and as a result, the amount of subsequent milk production. For example, the concentration of insulin-like hormone 3 is higher in cows with male calves, and an increase in its level causes a decrease in mother's milk production. But some researchers reported different results of the effect of calf sex on the mother's productive and functional traits. In general, it is challenging to determine the model for complex traits such as productive traits due to the effect of various genetic and environmental factors. Therefore, the difference in the results of the effect of the calf sex on the production and performance of the mother can be due to the difference in the methods of data analysis and the use of different effective factors in the model.
Conclusion
According to the results, it seems necessary to consider the effect of calf sex in the genetic evaluation of Isfahan Holstein cows and also cost-benefit analysis of the use of sexed semen in herds.
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