Tail Chalk Research Articles

Conception rates and serum progesterone concentration in dairy cattle administered gonadotropin releasing hormone 5 days after artificial insemination

The objectives of this study were to determine the effect of administration of exogenous GnRH 5 days after artificial insemination (AI) on ovarian structures, serum progesterone concentration, and conception rates in lactating dairy cows. In experiment 1, 23 Holstein cows were synchronized using the Ovsynch protocol. Five days after AI (day 0) cows were assigned randomly to receive either saline (saline; n = 11) or 100 μg GnRH (GnRH; n = 12). To examine ovarian structures, ultrasonography was performed on day 1 and every other day beginning on day 5 until day 13. On days 5 and 13 blood samples were obtained to measure serum progesterone concentrations. All cows in the GnRH-treated group developed an accessory corpus luteum (CL), whereas cows in the saline group did not. Mean serum progesterone concentrations did not differ between GnRH and saline groups on day 5 (1.64 ± 0.46 ng/ml versus 2.04 ± 0.48 ng/ml). On day 13 serum progesterone concentrations were greater ( P < 0.05) in the GnRH group compared with saline (5.22 ± 0.46 ng/ml versus 3.36 ± 0.48 ng/ml). In experiment 2, 542 lactating cows, at two different commercial dairies, were used to test the effect of administering GnRH 5 days after AI on conception rates. Cows were synchronized and detected for estrus according to tail chalk removal. Cows detected in estrus received AI within 1 h after detection of estrus. Five days after AI, cows were assigned randomly to receive either GnRH ( n = 266) or saline ( n = 276). Pregnancy status was determined by palpation per rectum of uterine contents approximately 40 days after AI. There was no effect of farm on conception rate. There was no effect of treatment as conception rates did not differ between GnRH and saline groups (26.7% GnRH versus 24.3% saline). Regardless of treatment, days in milk, parity, milk yield, and number of services had no effect on the odds ratio of pregnancy. In summary, the results of this study indicated that GnRH administered 5 days after AI increased serum progesterone by developing an accessory CL but did not improve conception rates in dairy cattle.

Use of Intravaginal Progesterone-Releasing Inserts in a Synchronization Protocol before Timed AI and for Synchronizing Return to Estrus in Holstein Heifers

Holstein heifers (n = 189) were submitted to a 42-d artificial insemination (AI) period in which they underwent AI after once-daily evaluation of rubbed tail chalk. At the onset of the AI period (d 0), heifers were assigned randomly to receive synchronization of ovulation and timed AI (TAI; d 0: 100μg of GnRH; d 6: 25mg of PGF2α; d 8: 100μg of GnRH + TAI) either without (GPG; n = 95), or with inclusion of a CIDR insert (CIDR; n = 94) from d 0 to 6. No CIDR heifers received AI before d 8 compared with 24% of GPG heifers, and pregnancy rate per AI (PR/AI) at 30 d after TAI did not differ between treatments. To synchronize return to estrus for heifers failing to conceive after TAI, heifers (n = 166) receiving TAI to first service were randomly assigned to receive no further treatment (control; n = 85) or receive a new CIDR insert between 14 and 20 d after TAI (Resynch; n = 81). No Resynch heifers received AI during CIDR treatment compared with 35% of control heifers, and the proportion of heifers receiving AI within 72h after the day of CIDR removal was 78 vs. 50% for Resynch vs. control heifers, respectively. No treatment×inseminator interaction was detected at first or second AI; however, overall PR/AI was modest for heifers throughout the experiment due to poor performance of 2 of the 3 herd inseminators (14, 6, and 58% PR/AI, respectively). Inclusion of CIDR inserts suppressed estrus during the TAI protocol with no reduction in PR/AI. Resynchronization of estrus using CIDR inserts resulted in tighter synchrony of estrus among nonpregnant heifers compared with untreated controls.

Fertility of holstein dairy heifers after synchronization of ovulation and timed AI or AI after removed tail chalk.

Nonlactating Holstein dairy heifers (n=352) 13 mo of age were managed using a 42-d artificial insemination (AI) breeding period in which they received AI after removed tail chalk evaluated once daily. At AI breeding period onset (d 0), heifers were randomly assigned to receive synchronization of ovulation (100 microg of GnRH, d 0; 25 mg of PGF2alpha, d 6; 100 microg of GnRH, d 8) and timed AI (TAI; d 8) and AI after removed tail chalk for the entire AI breeding period (GPG; n=175), or AI after removed tail chalk for the entire AI breeding period (TC; n=177). As expected, 17.7% (31/175) of GPG heifers received AI after removed tail chalk before scheduled TAI. Pregnancy rate per artificial insemination (PR/AI) at approximately 30 d after first AI tended to be greater for TC (46.5%) than for GPG (38.3%) heifers. No treatment x inseminator interaction was detected; however, overall PR/AI was low for heifers in both treatments due to variation among the 3 inseminators (24.8, 30.0, and 58.0%). Pregnancy loss from approximately 30 to approximately 75 d after first AI was 10% and did not differ between treatments. Based on survival analysis, days to first AI was greater for TC than for GPG heifers, whereas days to pregnancy across the 42-d AI breeding period did not differ between treatments. Overall, 81.2% of GPG heifers receiving TAI synchronized luteal regression and ovulated within 48 h after the second GnRH injection. We conclude that this synchronization protocol can yield acceptable fertility in dairy heifers if AI to estrus is conducted between treatment with GnRH and PGF2alpha and AI efficiency is optimized.

Comparison of a prostaglandin-F2α-based reproductive program with an estrus detection-based reproductive program on a large commercial dairy herd

The purpose of this study was to describe biological outcomes of two reproductive management strategies in commercial dairy cows: estrus detection with and without the use of prostaglandin-F2α. At regular preinsemination examinations, cows were allocated randomly to two cohorts: 1) prostaglandin cohort -- cows with palpable corpora lutea were injected with 25 mg dinoprost tromethamine and were bred by appointment 72 and 96 hours later, followed one week later by standard estrus detection practices (twice daily observation and tail chalking, with breeding approximately 12 to 24 hours later); and 2) estrus detection cohort -- cows identified as exhibiting estrus (observed estrus) were bred through the above standard procedures, without exposure to prostaglandin therapy. Age, milk production, weight, milk progesterone levels and reproductive data were collected for all cows. Although certain between-cohort effects were statistically significant, no differences could be found between the cohorts regarding standard measures of reproductive performance (average days in milk at conception (P=0.79), services per conception (P=0.48), proportion of animals failing to conceive to artificial insemination (P=0.53), and survival analysis on time to conception (P=0.30). With evidence for biological equivalence between the two reproductive strategies, nonbiological standards such as economics or ease of execution would be appropriate in choosing between the two strategies.

Duration of Estrous Cycles Subsequent to Two Injections of Prostaglandin F2α Given at a 14-Day Interval in Nonlactating Holstein Cows

Data from previous experiments in our laboratory indicated that estrous cycles following synchronization with two injections of prostaglandin F2α often averaged more than 21 d. To investigate whether this could be an effect of prostaglandin F2α, 54 mature heifers and nonlactating Holstein cows were used in a crossover experiment in which estrous cycles either occurred spontaneously or followed two injections of prostaglandin F2α at a 14-d interval (induced estrus). One estrous cycle of each type was recorded for each animal. Blood samples were collected twice weekly for analysis of progesterone. Cattle were observed twice daily for estrus with the aid of tail chalking and an androgenized cow. Estrous cycles following induced estrus were longer than those following spontaneous estrus (24.2 vs. 22.7 d). Ninety-two percent of the cycles following spontaneous estrus were 17 to 25 d in duration compared with 71% of the cycles following induced estrus. If the first prostaglandin F2α was given when progesterone was greater than 1ng/ml, the estrous cycle following treatment was longer than if the first prostaglandin F2α was given when progesterone was less than 1ng/ml (26.0 vs. 22.6 d). This experiment demonstrates that two injections of prostaglandin F2α increase the incidence of estrous cycles greater than 25 d. Stage of the estrous cycle at time of the first injection of prostaglandin F2α may contribute to this effect.

Estrus detection efficiency and the effects of using prostaglandin-F2α in a commercial dairy herd

The purpose of this study was to define the biological efficiency of a standard estrus detection regimen, both with and without use of prostaglandin-F2α, under commercial dairy conditions. At regular pre-breeding examinations, cows were allocated randomly to two cohorts: (1) prostaglandin (PT) — cows with palpable corpora lutea were injected with 25 mg dinoprost tromethamine and bred 72 and 96 h later; and (2) heat detection (HD) — cows identified as being “in heat” through twice daily observation with tail chalking were bred ∼ 12 h later. Age, body weight, milk production and reproductive data were collected for all cows, as were milk samples for progesterone analysis. Prostaglandin use significantly affected the sensitivity of the estrus detection test, lowering it by half (0.26 vs. 0.53), plus it increased the proportion of false negatives by 61% (0.34 vs. 0.21) over controls. Consequently, the predictive value of a positive test in the PT cohort was lowered by 14% (0.79 vs. 0.90) compared with control animals. Over both cohorts, the standard estrus detection test displayed a low sensitivity and a high specificity, characteristic of a diagnostic test, but not of a screening test. The findings from this dairy suggest that current recommended estrus detection procedures may be inappropriate for their declared purpose of being screening tests for estrus and that routine prostaglandin use may exacerbate the problem.