Review: Semen handling, time of insemination and insemination technique in cattle

peer-reviewedIn cattle artificial insemination plays not only a vital role in the successful establishment of pregnancy, which is a prerequisite for initiation of the subsequent lactation, but also in accelerating genetic improvement and facilitating the distribution of semen from genetically elite sires. The latter has been greatly facilitated by the ability to successfully cryopreserve semen. The objective of an insemination is to ensure that there is an adequate reservoir of competent, capacitated, motile sperm in the caudal region of the oviductal isthmus, the site of the main sperm reservoir in the cow, at the time of ovulation to ensure fertilisation. Handling of semen, particularly the 0.25 ml straw, is critically important. Thawed semen needs to be protected from cold and heat shocks and inseminated within 6 to 8 min of thawing. Uterine horn insemination give a modest improvement in conceptions rates particularly in situations where conception rates are low following uterine body inseminations. Most of the studies that evaluated heterospermic insemination were conducted on fresh semen only, and many lacked adequate replication. Consequently, it is difficult to deduce if there are real benefits from using heterospermic semen. While the interval from oestrous onset to time of ovulation would appear to be similar for cows and heifers at about 28 h there is huge variation (standard deviations of 5 to 6 h) around this average. While best conception rates are achieved when cows are inseminated from mid oestrus to a few hours after the onset of oestrus, this is difficult to achieve in practice. There is emerging evidence that having one insemination time, when all cows requiring insemination in the herd on that day are inseminated, does not compromise fertility provided insemination technique is good and the semen used is of high fertility

Effects of synchronization treatments on ovarian follicular dynamics, corpus luteum growth, and circulating steroid hormone concentrations in lactating dairy cows

Lactating dairy cows (n = 57) >= 45 d postpartum at first service were enrolled in a randomized complete block design study to evaluate treatments to synchronize estrus and ovulation. At 10 d before artificial insemination (AI), animals were randomly assigned to 1 of 3 treatments: (1) d - 10 GnRH (GnRH1; 10 mu g of buserelin, i.m.) and controlled internal drug release insert [CIDR, 1.38 g of progesterone (P4)]; d - 3 PGF(2 alpha) (PGF; 25 mg of dinoprost, i.m.); d - 2 CIDR out; and AI at observed estrus (CIDR_OBS); (2) same as CIDR_OBS, but GnRH (GnRH2) 36 h after CIDR out and timed AI (TAI) 18 h later (CIDR_TAI); or (3) same as CIDR_TAI, but no CIDR (Ovsynch). Transrectal ultrasound was used to assess follicle size before ovulation and on d 4, 8, and 15 after the presumptive day of estrus (d 0) to measure the corpus luteum (CL). Blood samples were collected to determine concentrations of estradiol (E2; d - 10, - 9, - 3, - 2, - 1, and 0) and P4 (d - 10, - 9, - 2, - 1, 0, 1, 4, 6, 8, 11, and 15). No treatment differences were observed in either circulating concentrations of P4 or the ovulatory response to GnRH1 at the onset of synchronization treatments. Circulating concentrations of P4 were greater for CIDR_OBS and CIDR_TAI compared with Ovsynch at 24 h after CIDR insertion (5.34 and 4.98 vs. 1.75 ng/mL) and immediately before CIDR removal (1.65 and 1.48 vs. 0.40 ng/mL). Peak circulating concentrations of E2 were greater for CIDR_OBS compared with Ovsynch (3.85 vs. 2.39 pg/mL), but CIDR_TAI (2.82 pg/mL) did not differ from either CIDR_OBS or Ovsynch. The interval from PGF injection to peak circulating E2 did not differ between CIDR_TAI and Ovsynch (52.1 vs. 49.8 h). Both CIDR_TAI and Ovsynch, however, had shorter intervals from PGF injection to peak circulating E2 concentrations compared with CIDR_OBS (67.8 h). The diameter of the dominant follicle before ovulation was greater for CIDR_OBS compared with Ovsynch (18.5 vs. 16.0 mm) but CIDR_TAI (17.1 mm) did not differ from either of the other treatments. The mean interval from PGF to ovulation was longer for CIDR_OBS (100.0 h) compared with CIDR_TAI and Ovsynch (84.4 and 83.2 h, respectively). Use of CIDR_OBS resulted in increased preovulatory follicle size and greater circulating concentrations of E2 due to a longer period of preovulatory follicle growth. Progesterone supplementation during synchronization and GnRH on the day before TAI affected ovulatory follicle size, and periovulatory circulating concentrations of P4 and E2. No differences, however, in postovulatory P4 or luteal volume profiles were observed

Evaluation of protocols to synchronize estrus and ovulation in seasonal calving pasture-based dairy production systems

Lactating dairy cows (n = 1,538) were enrolled in a randomized complete block design study to evaluate protocols to synchronize estrus and ovulation. Within each herd (n = 8), cows were divided into 3 calving groups: early; mid; and late; based on days in milk (DIM) at mating start date (MSD). Early calving cows (n = 1,244) were >= 42 DIM at MSD, mid-calving cows (n = 179) were 21 to 41 DIM at MSD, and latecalving cows (n = 115) were 0 to 20 DIM at MSD. Cows in the early, mid-, and late-calving groups were synchronized to facilitate estrus or timed AT (TAI) at MSD (planned breeding 1; PB1), 21 d (PB2), and 42 d (PB3) after MSD, respectively. For each PB, cows in the relevant calving group were stratified by parity and calving date and randomly assigned to 1 of 4 experimental groups: (1) d - 10 GnRH (10 mu g of i.m. buserelin) and controlled internal drug release insert (CIDR; 1.38 g of progesterone); d -3 PGF(2 alpha) (25 mg of i.m. dinoprost); and d 2 CIDR out and AT at observed estrus (CIDR_OBS); (2) same as CIDR_OBS, but GnRH 36 h after CIDR out and TAI 18 h later (CIDR_TAI); (3) same as CIDR_TAI, but no CIDR (Ovsynch); or (4) untreated controls (CTRL). The CIDR_OBS, CIDR TAI, and Ovsynch had shorter mean intervals from calving to first service compared with the CTRL (69.2; 63.4, and 63.7 vs. 73.7 d, respectively). Both CIDR_OBS (predicted probability; PP of pregnancy = 0.59) and CIDR_TAI (PP of pregnancy = 0.54) had increased odds of conceiving at first service compared with Ovsynch [PP of pregnancy = 0.45; odds ratio (OR) = 1.81 and OR = 1.46, respectively], and Ovsynch had decreased likelihood of conceiving at first service (OR = 0.70) compared with CTRL (PP of pregnancy = 0.53). Both CIDR_TAI {hazard ratio; HR [95% confidence interval = 1.21 (1.04, 1.41)]} and Ovsynch [HR (95% confidence interval) = 1.23 (1.05, 1.44)] were associated with an increased likelihood of earlier conception compared with the CTRL. A greater proportion of cows on the CIDR_TAI treatment successfully established pregnancy in the first 42 d of the breeding season compared with the CTRL (0.75 vs. 0.67 PP of 42-d pregnancy, respectively). Protocols to synchronize estrus and ovulation were effective at achieving earlier first service and conception in pasture-based seasonal calving dairy herds. However; animals that conceived following insemination at observed estrus had a decreased likelihood of embryo loss to first service compared with animals bred with TAI (PP of embryo loss after first service = 0.05 vs. 0.09; OR = 0.52)