Yield and fertility relationships in dairy cattle

Area of Science:

• Animal Breeding and Genetics
• Dairy Science
• Reproductive Biology

Background:

• Optimizing dairy cattle breeding requires understanding the genetic interplay between milk yield and reproductive fertility.
• Previous studies suggest potential antagonism between high yield and fertility, impacting herd efficiency.

Purpose of the Study:

• To estimate heritability for various yield and fertility traits in dairy cattle.
• To investigate phenotypic and genetic correlations between yield and fertility across parities.

Main Methods:

• Data from artificial insemination and test-day milk yield records were analyzed.
• Heritability estimates were derived using Henderson Method 3, maximum likelihood, and restricted maximum likelihood.
• Phenotypic and genetic correlations were calculated for first, second, and third parities.

Main Results:

• Heritability estimates for yield traits were within previously reported ranges.
• Fertility traits exhibited very low heritability (0 to 0.03).
• Phenotypic correlations between early lactation yield and fertility were slightly positive, becoming negative later in lactation.
• Genetic correlations between yield and fertility were generally positive and less affected by lactation stage than phenotypic correlations, with antagonism moderating across parities.

Conclusions:

• Genetic antagonism between milk yield and fertility in dairy cattle may be of limited practical concern due to low genetic variance in fertility traits.
• Breeding strategies can potentially improve yield without significant negative impact on fertility.