In research, daily individual progesterone and lutenyzing hormone (LH) measurements are also used to track the profile of these hormones during the estrous cycle. Thus, it is possible to predict the phase of the estrous cycle and the time of ovulation based on intense progesterone and LH samplings. Unfortunately, this technique is somewhat expensive and labor intensive, therefore, not considered for practical application in normal reproductive routines on dairy farms.
The number of cows to be sampled varies with herd size, and insemination protocol, since they will determine the number of cows inseminated in a single day. Ideally a minimum of 30 cows should be sampled.
Get assistance from you herd veterinarian to collect blood samples if needed. Follow the standard protocol for blood collection from the coccygeal artery or vein (tail vein) using a 10 cc vacuum tube without anticoagulants or additives.
Collected blood samples should be stored at upright position (see example in Picture 1) in the refrigerator for one (1) hour to allow for serum separation. Transfer the serum to a smaller sterile container (1.5 or 2.0 ml Ependorf container. Example in Picture 2.) and put all serum samples in the freezer. You can keep collecting and freezing samples until you have enough to justify shipment and analysis, which is about 30 samples. Ship the serum samples with lots of ice in a thermo-isolated container with overnight delivery to Accelerated Genetics headquarters in Baraboo, Wis. or the lab of your choice.
KETONE BODIES OR BETAHYDROXYBUTYRATE (BHBA):
Ketone bodies build up in the bloodstream when the pre-fresh or fresh cow’s liver is over saturated with fat mobilized from body reserves and there is not enough glucose to convert it into energy. In this case, fat takes an alternative pathway and is converted to ketone bodies. It is known that higher circulating ketone bodies near calving are correlated with lower fertility results in dairy cows.
A recent report (Walsh et al., 2007), using a large number of dairy cows, defined a threshold for circulating ketone bodies at two weeks (14 days) postpartum and subsequent pregnancy outcomes. They observed that cows presenting serum BHBA ≥ 1,400 μmol/L (or 14.4 mg/dL) were less likely to conceive. It was also found that animals that did not present high levels of BHBA postpartum had days open equals to 108. In contrast, animals with high levels of BHBA in the first two weeks postpartum had days open equals to 130.