Search

Unidentified heats contribute to declining fertility rates in English dairy herds. Several techniques have been advocated to improve heat detection rates. Despite demonstrable technical efficacy and cost-effectiveness, uptake is low. A study in South West England used the Theory of Reasoned Action (TORA) to explore dairy farmers' attitudes and beliefs towards heat detection techniques. Few farmers were convinced that following prescribed observation times, milk progesterone testing and using pedometers would fit their system or improve on their current heat detection practices. Perceived difficulty of using a technique was not a constraint on adoption. Without promotion that addresses identified barriers and drivers to adoption, little change in current practice can be expected.

The effect of using on-farm milk progesterone testing to monitor return to cyclicity after parturition and to classify correctly and to treat cystic cows was evaluated using modeling and simulation. The test was evaluated assuming low and high accuracies of progesterone measurement, first breeding policy of 40 d, average estrus detection rate of 55%, and an average fertility rate of 55%. Three testing schemes (starting milk progesterone testing on d 30, 40, or 50 after parturition) were compared against a control to evaluate the effect of monitoring return to cyclicity on cows' reproductive and economic performance. For this purpose, the use of the test was an economically justifiable management intervention. Starting to test on d 30 after parturition was the most effective scheme, reducing days open by 18 d, replacement rate by 2.4%, and increasing net return per cow per year by $11. Starting to test on d 50 postpartum was not economically justifiable. Accuracy of the test, within the range used in this study, was unimportant. Testing was most profitable in herds with low fertility and low efficiency of estrus detection. The use of the test to classify follicular and luteal cysts and to select the appropriate therapy was not economically justifiable because of the low proportion of cystic cows and the high variation in response to therapy.

SUMMARYDairy cows were inseminated on the basis of oestrus detection alone (Control, n = 206) or in conjunction with milk progesterone profiles (Experimental, n = 204). Milk samples were taken at 4–5 day intervals to determine oestrous cyclicity and on alternate days (at strategic times) to determine the time of ovulation. Progesterone profiles were consulted routinely as an aid to oestrus detection, and also to identify and aid diagnosis of cows with reproductive disorders. Cycling cows not observed in oestrus were inseminated on the basis of their progesterone profile alone. Animals showing oestrus within 2 days of a progesterone-timed insemination were inseminated again. In Experiments 1 and 2, inseminations were given from Day 42 post partum, but AI was delayed (mean time of 68±1·1 days after calving) in Experiment 3.The median interval from calving to first insemination was not significantly different between Experimental and Control groups, but the time of conception was earlier (P < 0·05) and the median calving interval shorter (P < 0·05) in progesterone-monitored cows in Expts 1 and 3. In addition, the percentage of cows served within 21 days of the start of the service period was greater (P < 0·05) in Experimental groups in Expts 1 and 2. This was reflected by an increase in the proportion (P < 0·05) of cows pregnant by 85 and 100 days after calving. The frequency with which the interservice interval equated to the length of the oestrous cycle was increased (P < 0·01) by progesterone testing (84·1% and 53·9% in Experimental and Control cows, respectively). Conception rates did not differ significantly between groups, but the number of double inseminations (P < 0·001) and thus the mean number of inseminations/conception (P < 0·01) were greater in progesterone-monitored cows. Conception rate was lower (P < 0·05) in cows that failed to show oestrus, and to the first insemination in double-inseminated cows.Progesterone testing reduced (by 44–66%, P < 0·01) the number of cows presented for veterinary examination and the mean time of presentation (P < 0·05), and also influenced the diagnosis made.

Results from milk progesterone assays can provide ovarian information, making it possible to monitor the reproductive status of the cow. Rapid, simple, and accurate on-farm milk progesterone tests are commercially available. Procedures for performing milk progesterone tests are specific for each test; however, principles of testing are similar. On-farm tests are designed to determine the relative progesterone concentration ("high" or "low") rather than obtaining a precise concentration. Evaluation of results is based on either a color or agglutination reaction with comparison to known standards. Potential uses of progesterone testing in a reproductive management program are: 1) identifying errors in detection of estrus, 2) predicting time of estrus, 3) assisting in pregnancy diagnosis, 4) differentiating types of ovarian cysts, and 5) evaluating response to endocrine therapy.

A commercial pregnancy testing service for cows became available to United Kingdom dairy farmers in 1975. The service met an immediate demand from farmers attempting to reduce losses due to delayed conception, $1.20 per cow per day, and after 18 mo approximately 5% of cows were being tested. Approximately one in six (16.5%) of the cows tested, which had not been detected in estrus by 24 days after insemination, were negative to the test; monthly variation was in the proportion of negative tests. Accuracy was 100% for the negative tests in herds where cow identification was good, and 85.2% for positive tests mainly because of fetal loss and insemination during the luteal phase. Other applications of the milk progesterone test in improving herd management are in limited use. These uses, which include the confirmation of estrus, fertility monitoring, and clinical applications, are of value to veterinarians and others in investigating subfertile herds or problem cows but, because of cost, are unlikely to find widespread application.