Search

One suggested approach to improve the reproductive performance of dairy herds is through the targeted management of subgroups of biologically similar animals, such as those with similar probabilities of becoming pregnant, termed pregnancy risk. We aimed to use readily available farm data to develop predictive models of pregnancy risk in dairy cows. Data from a convenience sample of 108 dairy herds in the UK were collated and each herd was randomly allocated, at a ratio of 80:20, to either training or testing data sets. Following data cleaning, there were a total of 78 herds in the training data set and 20 herds in the testing data set. Data were further split by parity into nulliparous, primiparous, and multiparous subsets. An XGBoost model was trained to predict the insemination outcome in each parity subset, with predictors from farm records of breeding, calving and milk recording. Training data comprised 74,511 inseminations in 45,909 nulliparous animals, 86,420 inseminations in 39,439 primiparous animals, and 158,294 inseminations in 32,520 multiparous animals. The final models were evaluated by predicting with the testing data, comprising 31,740 inseminations in 19,647 nulliparous animals, 38,588 inseminations in 16,215 primiparous animals, and 65,049 inseminations in 12,439 multiparous animals. Model discrimination was assessed by calculating the area under receiver operating characteristic curves (AUC); model calibration was assessed by plotting calibration curves and compared across test herds by calculating the expected calibration error (ECE) in each test herd. The models were unable to discriminate between insemination outcomes with high accuracy, with an AUC of 0.63, 0.59 and 0.62 in the nulliparous, primiparous and multiparous subsets, respectively. The models were generally well-calibrated, meaning the model-predicted pregnancy risks were similar to the observed pregnancy risks. The mean (SD) ECE in the test herds was 0.038 (0.023), 0.028 (0.012) and 0.020 (0.008) in the nulliparous, primiparous and multiparous subsets respectively. The predictive models reported here could theoretically be used to identify subgroups of animals with similar pregnancy risk to facilitate targeted reproductive management; or provide information about cows' relative pregnancy risk compared with the herd average, which may support on-farm decision-making. Further research is needed to evaluate the generalizability of these predictive models and understand the source of variation in ECE between herds; however, this study demonstrates that it is possible to accurately predict pregnancy risk in dairy cows using readily available farm data., (The Authors. Published by Elsevier Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).)

Two experiments were conducted with Holstein-Friesian cows in the Republic of North Macedonia and with Holstein cows in Kansas. We hypothesized that 1 dose of PGF 2α administered on d 8 (Ov-8×1) instead of d 7 (Ov-7×1) in an Ovsynch program [GnRH-1 (d 0)–7 d–PGF 2α –56 h–GnRH-2–16 h–timed artificial insemination (AI)] would increase the proportion of cows with complete luteolysis compared with controls receiving a single dose on d 7. Cows were treated with Ov-7×1 or with Ov-8×1 in experiment 1 (n = 347), using only a single dose of PGF 2α. In experiment 2 (n = 452), a third treatment was added (Ov-7×2), in which a second dose of PGF 2α was administered on d 8. Progesterone was measured in blood samples collected before the first or only PGF 2α administration and 72 h later before insemination. Complete luteolysis was defined as having occurred when progesterone was ≥1 ng/mL before PGF 2α and ≤0.3 ng/mL 72 h later (time of AI). Follicles and luteal structures were mapped before GnRH-1 and PGF 2α administrations. The results of experiment 1 demonstrated a greater percentage of multiparous cows in OV-8×1 having complete luteal regression compared with multiparous Ov-7×1 cows, whereas treatments were equally effective in primiparous cows, as reflected in the concentrations of progesterone before AI. Furthermore, pregnancy per AI did not differ between treatments. Results in experiment 2 revealed that 99.3% of cows in the Ov-7×2 treatment receiving the second dose of PGF 2α had complete luteolysis, regardless of parity, compared with significantly fewer cows in the Ov-7×1 and Ov-8×1 treatments (91.2 and 90.6%, respectively). Neither concentrations of progesterone, which averaged <0.4 ng/mL at AI, nor pregnancy per AI differed among the 3 treatments. In both experiments, when status of luteal function before PGF 2α treatment was examined [cows with no corpus luteum (CL) before GnRH-1 but which had formed a new CL in response to ovulation after GnRH-1; cows with an older CL (the same CL that was detected before GnRH-1); or cows with both a new and an older CL], treatments did not differ in causing complete luteolysis. Furthermore, complete luteolysis in experiment 2 did not differ regardless of whether cows had 1, 2, or 3 or more CL before PGF 2α administration. Pregnancy per AI did not differ among treatments, indicating that any of the 3 treatments might produce similar pregnancy outcomes with the flexibility of applying either of the 7- or the 8-d treatments. [ABSTRACT FROM AUTHOR]

The main objective was to assess the associations of subclinical hypocalcemia (SCH), diagnosed at parturition (SCH-0) and 7 d in milk (SCH-7), with fertility in a herd of grazing dairy cows. Additional objectives were to characterize Ca concentration on 0 and 7 d in milk (DIM), assessing the risk factors for SCH-0 and SCH-7 and also the relationship with health status (metritis, endometritis, subclinical ketosis, and culling). A prospective observational study was carried out in a dairy farm in Argentina. Holstein cows (n = 126) were body condition scored (BCS, 1-5) on -21 ± 3, 0, 7 ± 3, and 28 ± 7 DIM and blood was collected on 0 and 7 ± 3 DIM to determine Ca and ß-hydroxybutyrate concentrations. Calcium concentrations <2.0 and <2.14 mmol/L were used to define SCH-0 and SCH-7, respectively. The associations of SCH with (1) the odds for pregnancy to first service (P1AI) and pregnancy by 100 DIM (P100) were evaluated by logistic models, (2) the services per pregnancy was evaluated by a Poisson regression model, and (3) the hazards of insemination and pregnancy were evaluated with proportional hazards regression models whereas median days from calving to first insemination and to pregnancy were estimated by Kaplan-Meier method. Additionally, Ca concentration was assessed by linear regression models, and the associations of SCH-0 and SCH-7 with the odds for metritis, endometritis, subclinical ketosis, and culling were evaluated by logistic models. Calcium concentrations were similar at 0 and 7 DIM (2.40 vs. 2.41 mmol/L, respectively); they were higher in cows calving in fall than in summer (2.58 vs. 2.24 mmol/L), and they also were higher in primiparous than in multiparous cows (2.53 vs. 2.28 mmol/L, respectively). The proportion of cows having SCH-0 and SCH-7 was 27.3 and 39.3%, respectively. Fall-calving cows had lower odds for SCH- 0 [odds ratio (OR) = 0.31, 95% confidence interval (CI) = 0.12-0.86] than summer-calving cows, multiparous cows had higher odds for SCH-0 (OR = 3.96, 95% CI = 1.09-14.39) than primiparous cows, and cows with prepartum BCS =3.00 had higher odds for SCH-0 (OR = 4.03, 95% CI = 1.17-13.89) than in cows with BCS <3.00. Conversely, parity and prepartum BCS were not important predictors for SCH-7. Surprisingly, SCH-0 was not a risk factor for SCH-7. Cows with SCH-0 had lower odds for P1AI (OR = 0.26, 95% CI = 0.07-0.99) than normocalcemic cows, given that P1AI was 14 versus 38%, respectively. The hazard of first service was not associated with SCH-0 (hazard ratio = 1.03, 95% CI = 0.63-1.70) but cows with SCH-0 had lower hazard of pregnancy (hazard ratio = 0.39, 95% CI = 0.16-0.98) and took 32 d longer to get pregnant (105 vs. 73) than normocalcemic cows. Conversely, SCH-7 was not associated with fertility. Finally, SCH-0 and SCH-7 were associated with the odds for subclinical ketosis and metritis, respectively. In conclusion, SCH-0 but not SCH-7 is associated with reduced fertility in a herd of grazing dairy cows, but both were associated with health status. [ABSTRACT FROM AUTHOR]

The objective of this study was to determine the relative importance and contribution of several physiological factors as predictors of pregnancy risk in an Ovsynch (GnRH-1 - 7 d - PGF2α - 56 h - GnRH-2 - 16 h - artificial insemination) timed artificial insemination program: (1) age of the corpus luteum (CL; original CL, new CL, or both in response to GnRH-1) and resulting progesterone concentrations as they affected luteolysis, ovulation after GnRH-2, and pregnancy risk; (2) progesterone concentration before GnRH-1 and GnRH- 2 on subsequent ovulatory response to GnRH-1 and GnRH-2 as well as pregnancy risk; and (3) a combination of these factors in a multivariable logistic regression model to predict pregnancy risk. Original data from 7 published studies were combined including ovulatory responses to both GnRH injections, blood progesterone concentrations before GnRH-1, before PGF2α, and at 48 h after PGF2α, pregnancy per artificial insemination at d 32 and 60 after artificial insemination, and intervening pregnancy loss. Ovulation outcomes were greater at lesser progesterone concentrations after both GnRH injections despite the fact that pregnancy outcomes were greatest when progesterone exceeded 3 ng/mL before GnRH-1 and PGF2α, suggesting that greater progesterone concentration before GnRH-1 and incidence of ovulation act via different mechanisms to improve subsequent fertility. Ovulation after GnRH-2 and subsequent pregnancy outcome were positively related to lesser concentrations of progesterone at 48 h after PGF2α; however, for maximal pregnancy outcome, progesterone should be <0.5 ng/mL. Cows with a CL that also formed a new CL after GnRH-1 had the greatest pregnancy outcome, whereas cows with only a new CL (i.e., anovulatory cows and those at or near estrus without a CL at GnRH-1) had the poorest pregnancy outcome. Pregnancy loss was not affected by CL status during the timed artificial insemination program. Receiver operator curves produced cut points of progesterone concentration that predicted ovulation and pregnancy risk. Selected cut points of progesterone concentration 48 h after PGF2α produced true positive risks greater than 90% and false positive risks less than 25%, thus demonstrating the high predictability of ovulation after GnRH-2 and subsequent pregnancy outcome based on progesterone concentration. We conclude that progesterone concentration is highly predictive of ovulation and pregnancy risk in addition to body condition, size of ovulatory follicle, and parity. [ABSTRACT FROM AUTHOR]

Cows managed for extended lactation go through several estruses before rebreeding. The aims of this study were (1) to quantify the effect of the first 8 estruses after calving on milk yield, milking frequency, and estrous behavioral activity, and (2) to determine the effects of early lactation live weight gain (LWG) as an indication of energy balance on milk yield, plasma insulin-like growth factor 1 (IGF-1) concentration, estrous behavioral activity, interval from calving to first estrus, between-estrus intervals, and pregnancy risk. Milk yield, live weight, and estrous behavioral activity were measured daily in 62 Holstein cows, 17 primiparous and 45 multiparous, managed for an 18-mo calving interval. Blood plasma obtained at wk 3, 5, 12, and 24 after calving was analyzed for IGF-1. Estrus was detected by use of milk progesterone profiles combined with visual observations (i.e., mounting behavior and other). The cows were divided into 2 groups: the cows having a negative LWG in each of the first 5 wk post-partum and the cows having a positive LWG in at least 1 of the first 5 wk after calving. The results indicate a similar decrease of 0.56 kg of milk per day of estrus during each of the 8 consecutive estruses. The activity level was 17 ± 1 movements per hour higher during the 8 estruses compared with the basic activity level. More cows expressed mounting behavior at estrus 8 than at estrus 2 (63.3 and 45.9%, respectively). The negative LWG cows had lower IGF-1 and higher milk production than the positive LWG cows. Both LWG groups had similar interval from calving to first estrus, on average 55 d. To conclude, the decrease in milk yield during estrus is marginal and similar in consecutive estruses. Moreover, estrous behavior is more highly expressed in the later estruses compared with the earlier estruses. Reproductive parameters (frequency of mounting, pregnancy risk, interval to first estrus, and between-estrus intervals) were not influenced by the live weight change during early lactation. [ABSTRACT FROM AUTHOR]