Reproductive performance of dairy cows managed with a program aimed at increasing insemination of cows in estrus based on increased physical activity and fertility of timed artificial inseminations

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Abstract

The objective of this study was to compare the reproductive performance of lactating dairy cows using a treatment (TRT) program for second and subsequent artificial insemination (AI) services aimed at (1) increasing AI upon estrus detection based on increased physical activity (AIAct) and (2) increasing fertility of timed AI (TAI) services for cows not AIAct through presynchronization of the estrous cycle and improved physiological milieu before TAI. Cows in the control (CON) group were managed with a program that combined AIAct and TAI after the Ovsynch protocol. After nonpregnancy diagnosis (NPD) by transrectal ultrasonography at 31 ± 3 d after AI, cows received the following treatments: (1) CON (n=634), AIAct any time after a previous AI and resynchronization with the Ovsynch-56 protocol (GnRH-7d-PGF2α-56 h-GnRH-16 h-TAI) 1d after NPD, or (2) TRT (n = 616): cows with a corpus luteum (CL) ≥ 20 mm (TRT-CL) received a PGF2α injection 1d after NPD, whereas cows with no CL or a CL < 20 mm (TRT-NoCL) received a GnRH injection 3d after NPD. Cows in TRT-CL and TRT-NoCL not AIAct were enrolled in a 5-d Ovsynch + progesterone protocol (GnRH + controlled internal drug release-5d-PGF2α + controlled internal drug release removal-24 h-PGF2α -32 h-GnRH-16 h-TAI) 9 and 7d after the PGF2α or GnRH injection, respectively, to receive TAI. The hazard of pregnancy up to 270 DIM was similar for cows in the CON and TRT group (hazard ratio = 1.07, 95% CI = 0.95 to 1.21), but it was affected by parity (primiparous greater than multiparous cows). Median days to pregnancy for the CON and TRT group were 111 and 110 d, respectively. When evaluated after 104 DIM (first time point at which cows were affected by the treatments), the hazard of pregnancy was similar for the CON and TRT group (hazard ratio = 1.15, 95% CI = 0.95 to 1.39). Based on this analysis, median days to pregnancy for the CON and TRT group were 161 and 178 d, respectively. Thus, in spite of increasing the proportion of cows AIAct (29 and 10% for TRT and CON), median days to insemination after NPD were greater for cows in the TRT (17 d) than the CON (10 d) group, which coupled with similar fertility to AIAct, and TAI failed to improve overall reproductive performance. A low proportion of cows with a CL at NPD (65.2%) and a poor response to PGF2α may explain the poor estrus detection efficiency in the TRT group. We concluded that, when compared with a typical estrus detection and TAI program for cows failing to conceive to previous AI services, a program aimed at increasing the proportion of cows AIAct after NPD and fertility of TAI services increased the proportion of cows AIAct but failed to reduce days to pregnancy during lactation because of greater days to AI after NPD.

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Comparison of ovarian function and circulating steroids in estrous cycles of Holstein heifers and lactating cows.

R Sartori, J Haughian, R D Shaver … (2004)

Ovarian function was compared between nulliparous heifers (n = 29; 10 to 16 mo old) and lactating Holstein cows (n = 31; 55.9 +/- 3.5 d postpartum). Follicular dynamics, corpus luteum growth, and regression, and serum steroid concentrations were evaluated through ultrasonography and daily blood sampling. Most heifers (27 of 29) but only 14 of 31 cows had typical spontaneous estrous cycles after cycles were initiated. Twelve cows had atypical cycles, and 5 became anovulatory during the study. The 12 cows with atypical estrous cycles had low serum estradiol after luteolysis and failed to ovulate the dominant follicle present at luteolysis. Heifers and cows with typical cycles were compared directly. Interovulatory intervals were similar between heifers (22.0 +/- 0.4 d) and cows (22.9 +/- 0.7 d). Those animals had estrous cycles with either 2 (15 heifers; 11 cows), 3 (9 heifers; 2 cows), or 4 follicular waves (3 heifers; 1 cow). Cows ovulated later after luteolysis than heifers (5.2 +/- 0.2 vs. 4.6 +/- 0.1 d, respectively), and had more multiple ovulations (17.9 vs. 1.9%). Maximal serum estradiol concentration preceding ovulation was lower in cows than in heifers (7.9 +/- 0.8 vs. 11.3 +/- 0.6 pg/mL) even though ovulatory follicles were larger in cows (16.8 +/- 0.5 vs. 14.9 +/- 0.2 mm). Similarly, maximal serum progesterone concentration was lower for cows (5.6 +/- 0.5 vs. 7.3 +/- 0.4 ng/mL), whereas maximal volume of luteal tissue was larger for cows than heifers (11,120 +/- 678 vs. 7303 +/- 308 mm3). Thus, higher incidence of reproductive anomalies in lactating cows, such as low conception rate, ovulation failure, delayed ovulation, and multiple ovulations, may be due to lower circulating steroid concentrations in spite of larger ovulatory follicles and luteal structures.

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Effects of presynchronization and bovine somatotropin on pregnancy rates to a timed artificial insemination protocol in lactating dairy cows.

C Orlandi, Luiz Lopes, C Risco … (2001)

The objective was to examine the effects of presynchronization and bovine somatotropin (bST) on pregnancy rates to a timed artificial insemination protocol in lactating dairy cows. Lactating Holstein cows (n = 543) were assigned randomly in a 2 x 3 factorial experiment in which cows received a presynchronization treatment or not, and were treated with bST (500 mg) at 63 +/- 3, 73 +/- 3, or 147 +/- 3 d postpartum. The latter group was used as a control. Presynchronization treatment consisted of two injections of PGF2alpha (25 mg) given 14 d apart, with the second injection of PGF2alpha being administered 12 d before initiation of the timed artificial insemination protocol. All cows received GnRH (100 microg) at 63 +/- 3 d postpartum, an injection of PGF2alpha (40 mg) 7 d later, a GnRH injection at 48 h after PGF2alpha and were inseminated 16 to 20 h later. Cows were resynchronized if determined to be nonpregnant at ultrasonography at 32 d after insemination with a GnRH injection (100 microg), an injection of PGF2alpha (40 mg) 7 d later, and a GnRH injection at 48 h after PGF2alpha and were inseminated 16 to 20 h later. Cows were examined for pregnancy at 32 d and reexamined at 74 d after insemination. No differences in pregnancy rates were observed between cows receiving bST treatment at 63 +/- 3 d postpartum or at 73 +/- 3 d postpartum. An interaction between presynchronization and bST treatment indicated that pregnancy rates were increased for cows treated with bST when cows were presynchronized. When anestrous cows were excluded from the analyses, both an effect of bST and of presynchronization were observed, indicating that bST increased pregnancy rates regardless of presynchronization treatment and that presynchronization also increased pregnancy rates independently of bST treatment. Presynchronization and bST treatment may be used to increase first-service pregnancy rates to a timed artificial insemination protocol.

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Reproductive management of lactating dairy cows using synchronization of ovulation.

R Pursley, Milo Wiltbank, Michael Kosorok (1997)

Lactating dairy cows have poor reproductive efficiency because of low fertility and low rates of estrus detection. To eliminate the dependence on detection of estrus, we have recently developed a timed artificial insemination (AI) protocol that synchronized the time of ovulation using GnRH and PGF2 alpha. The effectiveness of this protocol as a management tool was compared with standard reproductive management. Lactating dairy cows (n = 333) from three herds were randomly assigned at parturition to two groups. Control cows were managed according to the typical reproductive strategy of the farm that relied on detection of estrus, the a.m.-p.m. breeding rule, and periodic use of PGF2 alpha. Treated cows had timed AI after synchronization of ovulation with GnRH and PGF2 alpha. For both groups, the voluntary waiting period was 50 d postpartum. Pregnancy diagnosis was performed by ultrasound between 32 and 38 d post-AI. Nonpregnant cows were inseminated again using the original treatment until diagnosed as pregnant or until culled from the herd. Median days to first AI (54 vs. 83) and days open (99 vs. 118) were lower for treated cows than for control cows, respectively. Pregnancy rates for the first AI were similar (37% vs. 39%) for the two groups even though treated cows were bred at an earlier time postpartum. More treated cows than control cows were pregnant at 60 d (37% vs. 5%) and at 100 d (53% vs. 35%) after calving. Thus, this protocol allowed effective management of AI in lactating dairy cows without the need for estrus detection.