Not all cows react the same way to the same environment or action. There are slight physiological, genetic, and maintenance variations that cause some animals to thrive where others struggle, and vice versa. Finding those cows that are resilient is often one of a farm’s main goals.
Why, then, do we generally treat all cows like they are the same? This was the question posed by Cornell University’s Julio Giordano during the Dairy Cattle Reproduction Council Annual Meeting.
Of course, the answer is because it streamlines the farm’s operations and works fairly well. However, Giordano is investigating if more specialized attention to reproduction can pay off. In short, does it pay to be more specific to an individual cow’s needs?
Sorting cows into “buckets,” as he called it, for receiving different attention can be done in a few ways. He discussed how differentiating cows based on estrus expression in the voluntary waiting period (VWP) can provide some benefits.
About half of cows will express a heat before the end of the VWP when the farm wants to begin breeding, Giordano stated. These cows are associated with better reproduction: they have a higher pregnancy per A.I. than cows that don’t show a heat in the VWP, and a greater percentage are pregnant by 150 days in milk (roughly 78% versus 66%).
What Giordano studied was that these cows would perhaps not need a timed A.I. protocol to achieve acceptable reproduction, therefore reducing hormone use and labor while more strategically using timed A.I. Cows may even be able to be bred earlier than if they were on the protocol, he added.
In the study, cows that showed a heat during the VWP were given one more month to show another heat, which they were bred off of. If they didn’t show another heat, they were put on timed A.I., as were all cows that didn’t express estrus at all during the VWP. Giordano said that in this specific case, about 85% of cows were bred from a detected heat.
At the first service, conception rate was higher for the cows that were on timed A.I. This is not the way to maximize first service conception rate, Giordano admitted. However, the speed at which cows get pregnant after calving can be very similar between the two groups. He pointed out that the cows bred off estrus and timed A.I. had the same pregnancy rate after calving, days open, and percent of animals pregnant by 150 days in milk. For farms looking to use less timed A.I., working off of a cow’s individual physiology, as reflected by heat during the VWP, can work.
Still, Giordano advised not classifying cows into groups solely based on one factor. Genomic data, indexes, and more all provide even more information with which to decide how a cow will best respond to a breeding service. He noted that highly fertile cows, as identified by daughter pregnancy rate (DPR) numbers, performed even better when bred off a heat. The data is there for a reason, and it supports treating cows individually where possible.
