J.N.S. Sales

Equine chorionic gonadotropin improves the efficacy of a timed artificial insemination protocol in buffalo during the nonbreeding season

Two experiments were conducted to evaluate the effects of equine chorionic gonadotropin (eCG) treatment on ovarian follicular response, luteal function, and pregnancy in buffaloes subjected to a timed artificial insemination (TAI) protocol during the nonbreeding season. In experiment 1, 59 buffalo cows were randomly assigned to two groups (with and without eCG). On the first day of the synchronization protocol (Day 0), cows received an intravaginal progesterone (P4) device plus 2.0 mg estradiol benzoate im. On Day 9, the P4 device was removed, all cows were given 0.150 mg PGF(2α) im, and half were given 400 IU eCG im. On Day 11, all cows were given 10 μg of buserelin acetate im (GnRH). Transrectal ultrasonography of the ovaries was performed on Days 0 and 9 to determine the presence and diameter of the largest follicle; between Days 11 and 14 (12 hours apart), to evaluate the dominant follicle diameter and the interval from device removal to ovulation; and on Days 16, 20, and 24 to measure CL diameter. Blood samples were collected on Days 16, 20, and 24 to measure serum P4. In experiment 2, 256 buffaloes were assigned to the same treatments described in experiment 1, and TAI was performed 16 hours after GnRH treatment. Pregnancy diagnosis was performed by ultrasonography 30 days after TAI. Treatment with eCG increased the maximum diameter of dominant follicles (P = 0.09), ovulation rate (P = 0.05), CL diameter (Pxa0= 0.03), and P4 concentrations (P = 0.01) 4 days after TAI, and pregnancy per AI (52.7%, 68/129 vs. 39.4%, 50/127; P = 0.03). Therefore, eCG improved ovarian follicular response, luteal function during the subsequent diestrus, and fertility for buffalo subjected to a TAI synchronization protocol during the nonbreeding season.

Donor category and seasonal climate associated with embryo production and survival in multiple ovulation and embryo transfer programs in Holstein cattle.

The present study investigated the effect of Holstein donor category (cows vs. heifers) and climate variation (hot vs. cooler season) on the efficiency of in vivo embryo production programs as well as embryo survival after transferred to Holstein recipient cows. A total of 1562 multiple ovulation (MO) procedures (cows: n = 609, and heifers: n = 953) and 4076 embryo transfers (ETs) performed in two dairy herds were evaluated. Donor cows had greater number of CLs (10.6 ± 0.6 vs. 7.5 ± 0.4; P < 0.0001) and ova/embryos recovered (7.6 ± 0.6 vs. 4.6 ± 0.4; P < 0.0001) compared with donor heifers. However, fertilization rate (47.9 vs. 82.4%; P < 0.0001) and proportion of transferable embryos (31.5 vs. 67.4%; P < 0.0001) were lower in donor cows than heifers, respectively. Regardless of donor category, the proportion of freezable embryos was less (P < 0.001) during hot season than in cooler season (21.4 vs. 32.8%). However, greater decline in the proportion of freezable embryos during the hot season was observed in cows (21.7 vs. 10.7%) compared with heifers (46.2 vs. 38.1%; P = 0.01). In contrast, the season on which the embryo was produced (hot or cool) did not affect pregnancy rate on Day 31 (30.5 vs. 31.7%; P = 0.45) and 45 (25.3 vs. 25.1%; P = 0.64) of pregnancy. Regardless of the season in which the embryos were produced, embryonic survival after transferring embryos retrieved from donor cows was greater on Days 31 (36.0 vs. 30.7%; P = 0.001) and 45 (28.3 vs. 23.1%; P = 0.001) of pregnancy when compared with embryos from donor heifers. In conclusion, MO embryo production efficiency decreased during the hot seasons both in cows and heifers; however, the decline was more pronounced in donor cows. Regardless of the embryo source, similar pregnancy rate was observed in the recipient that received embryos produced during the hot and cooler seasons. Curiously, embryos originating from donor cows had higher embryonic survival when transferred to recipient cows than embryos originating from heifers.

Different circulating progesterone concentrations during synchronization of ovulation protocol did not affect ovarian follicular and pregnancy responses in seasonal anestrous buffalo cows

Three experiments were designed to evaluate the effect of different circulating progesterone (P4) concentrations during synchronization of ovulation protocol for timed artificial insemination of seasonal anestrous buffalo cows. In the first trial, ovariectomized cows were randomly allocated into one of three groups: using new P4 devices (G-New; n = 8), using devices previously used for 9 days (G-Used1x; n = 8), and using devices previously used for 18 days (G-Used2x; n = 8). The P4 device was maintained for 9 days, and the circulating P4 concentration was measured daily. The circulating P4 concentrations during the P4 device treatment were the lowest for G-Used2x (1.10 ± 0.04 ng/mL), intermediate for G-Used1x (1.52 ± 0.05 ng/mL), and the highest for G-New (2.47 ± 0.07 ng/mL; P = 0.001). In the second trial, 31 anestrous cows had their ovarian follicular dynamics evaluated after receiving the treatments described previously (G-New [n = 10], G-Used1x [n = 11], and G-Used2x [n = 10]). At insertion of the P4 device, cows were administered 2.0 mg of estradiol benzoate. Nine days later, the P4 device was removed and cows were administered 0.53 mg of cloprostenol sodium plus 400 IU of eCG. Forty-eight hours after P4 device removal, 10 μg of buserelin acetate was administered. There were no differences among the groups (G-New vs. G-Used1x vs. G-Used2x) in diameter of the largest follicle at P4 device removal (9.0 ± 0.8 vs. 10.1 ± 0.9 vs. 8.6 ± 0.8 mm; P = 0.35), in interval from P4 device removal to ovulation (77.1 ± 4.5 vs. 76.5 ± 4.7 vs. 74.0 ± 4.4 hours; P = 0.31), or in ovulation rate (80.0% vs. 81.8% vs. 60.0%; P = 0.51). In experiment 3, 350 anestrous cows were randomly assigned into one of the three treatments described previously (G-New, n = 111; G-Used1x, n = 121; G-Used2x, n = 118) and received a timed artificial insemination for 16 hours after buserelin treatment. The 30-day pregnancy rates did not differ among groups (55.9% vs. 55.4% vs. 48.3%; P = 0.39). Thus, the low circulating P4 concentrations released from a used P4 device efficiently control the ovarian follicular growth and had no detrimental effect on the pregnancy rates of the seasonal anestrous buffalo cows.

A comparison of two different esters of estradiol for the induction of ovulation in an estradiol plus progestin-based timed artificial insemination protocol for suckled Bos indicus beef cows.

The abilities of two different estradiol esters to induce ovulation in a timed AI (TAI) synchronization protocol in suckled Bos indicus cows were evaluated. In Experiment 1 (synchrony of ovulation), 31 cows were submitted to an estradiol/progestin-based synchronization protocol (Day 0) and randomly assigned to one of three treatments at the time of progestin removal on Day 8: 0.5 or 1.0mg of estradiol cypionate (EC) at that time or 1.0mg of estradiol benzoate (EB) 24h later (Day 9). To determine the timing of ovulation, ultrasound examinations were performed every 12h from ear implant removal to 96 h after the removal. Orthogonal comparisons were performed to determine the effects of estradiol ester and the effects of the dose of EC on reproductive parameters. Although neither the E2 ester (P = 0.83) nor the dose of EC (P = 0.55) affected the ovulation rate, the interval from progestin removal to ovulation was longer (P=0.04) in EC-treated cows (1.0mg EC = 71.1 ± 3.6 and 0.5mg EC = 78.0 ± 3.5) than EB-treated cows (EB = 66.0 ± 2.3) was detected. Ovulation in 0.5-mg-EC-treated cows was less synchronous than that in 1.0-mg-EC-treated cows (distribution curves compared using kurtosis). In Experiment 2 (pregnancy per AI; P/AI), 660 cows at two different locations received the same synchronization protocol (n = 361 at Farm A and n = 299 at Farm B) and were treated with estradiol esters as in Experiment 1 [0.5mg EC (n = 220) or 1.0mg EC (n = 219) at the time of progestin removal or 1.0mg EB (n = 221) 24h later]. The cows were inseminated 54 to 56 h after progestin removal. As applied in the Experiment 1, orthogonal comparisons were performed to evaluate the effect of estradiol ester and the dose of EC on P/AI. Although the type of estradiol ester used did not affect the P/AI (P = 0.57; EB - 43.0% vs. EC - 44.6%), the P/AI was higher (P=0.03) in cows treated with 1.0mg EC (55.7%) than in those treated with 0.5mg EC (38.6%). In summary, the administration of 0.5mg EC at the time of progestin removal altered the distribution of ovulation and resulted in a lower P/AI when compared with the use of 1.0mg EC in suckled B. indicus cows. However, the P/AI following the administration of 1.0mg EC at the time of progestin removal did not differ from that after the administration of 1.0mg EB 24h later.

Effects of equine chorionic gonadotrophin on follicular, luteal and conceptus development of non-lactating Bos indicus beef cows subjected to a progesterone plus estradiol-based timed artificial insemination protocol

The aim of this study was to evaluate the effects of equine chorionic gonadotropin (eCG) on ovarian follicular responses, corpus luteum (CL) development and conceptus length on day 16 after timed artificial insemination (TAI). A total of 124 cows at day 0 (D0) received 2 mg of estradiol benzoate (EB) and the insertion of a progesterone (P4) intravaginal device. Eight days later, the device was removed, and cows received 0.15 mg of prostaglandin and 0.5 mg of estradiol cypionate (EC), and were randomly assigned to 1 of 2 treatments: eCG (n=60), in which cows received 300 U of eCG; and control (n=64). Cows were TAI 48 h after P4 device removal. The diameter of the largest follicle (LF) present on D8 and D10 and of CL on D15 and D26 were measured. Conceptus recovered rate, conceptus length, CL diameter and weight were determined at slaughter on D26. Plasma P4 concentration was determined on D15 and D26. Follicular growth from D8 to D10 (P=0.03), the diameter of CL at D15 (P=0.03) and D26 (P=0.003) and the CL weight at day 26 (P=0.04) were greater in the eCG group than the control. However, there was no effect of eCG treatment on oestrus occurrence, conceptus recovery rate and length, or P4 concentrations on either D15 or D26. In conclusion, although eCG increases follicular responses and the diameter of the CL, this gonadotropin treatment does not influence the length of the conceptus or the P4 concentration on the subsequent oestrus cycle.