For years the dairy industry has been searching for the ideal time for first insemination. Traditionally, farms have aimed for a 12-month calving interval requiring a successful breeding before 90 days in milk. For many dairy herds this is a reasonable time frame for breeding, but a recent study from the Swedish University of Agricultural Sciences suggested that delayed breeding on some animals in the herd can benefit their reproduction and production.
The study published in the Journal of Dairy Science looked specifically at first-lactation cows in 18 commercial dairy herds in Sweden. The researchers split the group of 338 cattle into two groups — those to be bred before 90 days and those to be held until 185 days in milk. The latter group represented a calving interval of 16.3 months.
The extended voluntary waiting period (VWP) group was selected based on three criteria in early lactation.
- They were in the top 10% of cows with the highest genomic persistency index.
- They had a difficult calving or disease during the first month of lactation.
- They were higher yielding during day 4 to 33 after calving than herdmates.
Half of the cattle that qualified for the extended VWP were held until at least 185 days in milk to be bred, while the other half were conventionally bred before 90 days in milk. Animals not qualifying for one of the three above criteria were also bred by 90 days in milk.
So, was there a difference?
Cows on the extended VWP protocol had a higher first-service conception rate at 60% than those that met the criteria for extended VWP but were still bred by 90 days in milk (45%). The extended VWP group also required fewer inseminations per conception (1.67) than their herdmates that also qualified for the extended VWP and were bred by 90 days in milk. Those that did not meet the criteria for early VWP fell between the other two groups in first-service conception rate (51%) and inseminations per conception (1.85).
Full lactation milk yield and daily milk yield were lowest in the conventional VWP group that didn’t qualify for extended VWP. Daily milk yield was similar between the other two groups with whole lactation milk yield being understandably higher in the extended VWP group.
In all, researchers concluded that extending the voluntary waiting period in first-lactation dairy cattle provided a benefit in the form of fewer inseminations and better first-service conception rates without reducing milk yield by the extended calving interval.
The author is a dairy farmer in Kansas and a former associate editor at Hoard’s Dairyman. Raised on a 150-cow dairy near Valley Center, Kansas, Maggie graduated from Kansas State University with degrees in agricultural communications and animal sciences.
