By Andrew Sandeen
Managing heifer inventories on a dairy farm is not always an easy responsibility. Having too few heifers brings a lot of risk to the future outlook and limits opportunities for strategic animal sales. Having too many heifers stretches facility space, depletes feed inventories, and often costs more than will likely be recouped. Deciding which heifers to keep and which to sell, as well as breeding decisions, can be a challenge.
At discussion meetings in southwestern Pennsylvania, dairy producers indicated through informal surveys that the total number of non-lactating heifers on their farms relative to the total number of lactating cows declined in the past year, suggesting these producers realized an oversupply at some point and made efforts to correct the numbers. However, the job is not yet complete. All the survey respondents indicated a desire to get the percentage of heifers down even further. It is common for dairy farms to have an overabundance of heifer calves, which should prompt management adjustments to decrease those numbers.
There is an important opportunity to evaluate options before breeding takes place. The ideal is to identify which matings will result in the greatest positive progress for the dairy herd and to complement that with the most economical options for other matings.
Some dairy inventory corrections can be accomplished using beef semen, a practice which has quickly been adopted nationwide. Genetic rankings can be used to help identify the lower end animals to mate to beef sires. The benefit is that beef on dairy crossbred calves often have more sale value than Holstein bull calves.
Selecting only the females with the best genetics for new dairy matings is wise, but we know genetics is only half of the equation for phenotypic performance. In thinking about the big picture of heifer inventories, strategic decision-making can continue after calves are born and heifer inventory numbers are more certain. What other factors that affect the value of a heifer might be worth considering?
Health is a big factor. Even elite genetics will be limited in animals that have not received adequate and timely colostrum. Heifers with recurring respiratory problems are another group that stands little chance of high performance. These are the types of animals to target for strategic marketing to lessen the heifer surplus before they hit the milking herd.
A few recent research studies provide some additional food for thought, identifying factors which may influence breeding and heifer inventory decisions for some farms.
In a New Zealand study (Handcock et al., 2021), the offspring of dams at least nine years old had lower milk production than offspring from younger cows, presumably because of lower genetic merit. This follows the general understanding that, as genetic progress advances, the genetic makeup and production of offspring from younger animals exceeds that of older cows.
In a Florida study (Carvalho et al., 2020), daughters of primiparous (first lactation) cows had several advantages over daughters from multiparous cows. They were less likely to die as heifers, they became pregnant earlier, they had about 5% less pregnancy loss, they calved earlier, and they were less likely to have clinical disease (retained placenta, metritis, mastitis, lameness, digestive problems, or respiratory ailments) during their first lactation.
In the same Florida study, daughters of cows which had clinical diseases during the lactation in which the pregnancy was generated had a lower incidence of clinical disease as a young heifer and as a first-lactation cow, presumably due to altered factors in the uterus during pregnancy that improve resilience to health challenges later in life. The cows with no clinical disease that had offspring which were approximately 10% more susceptible to clinical disease. From this study, it seems that offspring from primiparous cows and from older cow which had health challenges during their lactation could generally be favored over offspring from healthy, older cows.
In a different Florida study (Laporta et al., 2020), heifers from cows that were heat stressed during their dry period produced at least five pounds less milk per day, on average, during their first three lactations than heifers from cows that were more adequately cooled during the dry period. Even granddaughters of the heat-stressed cows were less productive. Therefore, heifers born to animals that have experienced heat stress in their dry periods could be moved higher on the list for potential removal from the dairy herd when numbers need a downward adjustment.
Results from these recent research studies might not lead to clear-cut selection protocols for ensuring successful prioritization of dairy heifers, but they do provide more clues to some of the factors which can affect dairy efficiency.
Be thoughtful about breeding and strategic selling decisions. It will impact the generations to come.
Source : psu.edu