Farm Table says:
The effects of calf gender
What is the problem?
Researchers from the University of Liverpool and the Dairy Veterinarians Group in the US were interested in the effect of sexed semen on milk yield and fat content in Holstein cows. Sexed semen can be used to reduce the number of dairy bull calves born in the UK, which are typically unwanted and raise ethical and welfare concerns for the industry. A milk recording data set was used to evaluate calf gender and the effect on milk yields and fat properties.
What did the research involve?
Information was gathered from The Cattle Information Service (CIS) milk recording database. The criteria for data inclusion in the study were as follows:
- first and second lactation animals only
- Holstein Friesian breed
- milk fatty acid content recorded
- calf gender
- milk yeild
This resulted in 211,932 animals with usable data from 2,000 herds, from Feb 2013 to Dec 2014. The data base is from the UK. Additional selection criteria were applied before analysis, which included both univariable and multivariable linear regression models for lactation’s one and two.
What were the key findings?
Researchers state that a heifer calf gave a 1% milk yield advantage with first lactation heifers, while bull calves gave a 0.5% advantage in second lactation. Heifer calves were associated with a 0.66kg reduction in saturated fatty acid content in first lactation, with no significant difference between the genders in second lactation. The research found no relationship between calf gender and milk mono- or polyunsaturated fatty acid content.
The researchers summarise that in comparison to nutrition and genetics, the effect of calf gender on milk yield and saturated fatty acid content was minor.