Reproductive problems in dairy cows frequently begin prior to calving. One of the regular practices you should consider when subfertility is suspected in your herd is to use lab tests that may help detect critical physiological changes happening in the cow around calving that otherwise would go unnoticeable until a clinical condition appears. Even worse, when the clinical condition is diagnosed, reproductive failure is already under way.
Important management problems during the transition period or in your regular heat detection program can be monitored with the lab tests presented in this article. The objective of this article is to outline and briefly describe the most common reproductive and metabolic parameters that producers and consultants can use to identify possible problems related to fertility in high producing dairy herds. An important aspect when collecting samples to measure reproductive hormones or metabolites is sample size and time of collection, so management decisions can be made with confidence.
Under normal conditions, circulating progesterone is very low (<1 ng/mL of serum) for cows displaying signs of heat, and will stay low for about three days. Then progesterone begins to rise above 1 ng/mL, reflecting the activity of a new corpus luteum during the remaining of metaestrus and diestrus. Producers can collect blood samples from cows at the time of insemination for either heat detection or fixed-time A.I. (TAI) programs. With this procedure we can estimate the proportion of cows with high progesterone at the time of insemination, thus determining the proportion of false positive heats. Ideally another blood sample should be collected 7 to 10 days after A.I. to detect anovular cows.</p />
Normally, no more than 10% of the cows should have progesterone in serum greater than 1 ng/mL. As pointed out by several research groups, cows with high circulating progesterone near A.I. are less likely to conceive, as shown in Figure 1 below (adapted from Souza et al., 2007).
Progesterone can be measured from the serum or milk samples and is a useful tool to evaluate the proportion of cows not cycling at the end of voluntary waiting period (VWP). And more importantly it can be used to track compliance on a TAI protocol or to determine accuracy of estrus detection as stated above.
Based on this information, your herd veterinarian can create a benchmark or change management practices in order to induce cyclicity and maximize fertility results. In addition, your herd veterinarian can use therapeutic treatments to induce cyclicity for individual animals. You, as a manager, can also review your heat detection program and responsibilities for injections during your TAI protocol.