D.J. Ambrose

Pregnancy rates to timed artificial insemination in dairy cows treated with gonadotropin-releasing hormone or porcine luteinizing hormone

We compared the effects of porcine luteinizing hormone (pLH) versus gonadotropin-releasing hormone (GnRH) on ovulatory response and pregnancy rate after timed artificial insemination (TAI) in 605 lactating dairy cows. Cows (mean+/-SEM: 2.4+/-0.08 lactations, 109.0+/-2.5 d in milk, and 2.8+/-0.02 body condition score) at three locations were assigned to receive, in a 2x2 factorial design, either 100 microg GnRH or 25mg pLH im on Day 0, 500 microg cloprostenol (PGF) on Day 7, and GnRH or pLH on Day 9, with TAI 14 to 18h later. Ultrasonographic examinations were performed in a subset of cows on Days 0, 7, 10, and 11 to determine ovulations, presence of corpus luteum, and follicle diameter and in all cows 32 d after TAI for pregnancy determination. In 35 cows, plasma progesterone concentrations were determined 0, 3, 4, 5, 6, 7, and 12 d after ovulation. The proportion of noncyclic cows and cows with ovarian cysts on Day 0 were 12% and 6%, respectively. Ovulatory response to first treatment was 62% versus 44% for pLH and GnRH and 78% versus 50% for noncyclic and cyclic cows (P<0.01). Location, ovulatory response to first pLH or GnRH, cyclic status, presence of an ovarian cyst, and preovulatory follicle size did not affect pregnancy rate. Plasma progesterone concentrations after TAI did not differ among treatments. Pregnancy rate to TAI was greater (P<0.01) in the GnRH/PGF/pLH group (42%) than in the other three groups (28%, 30%, and 26% for GnRH/PGF/GnRH, pLH/PGF/GnRH, and pLH/PGF/pLH, respectively). Although only 3% of cows given pLH in lieu of GnRH on Day 9 lost their embryo versus 7% in those subjected to a conventional TAI using two GnRH treatments, the difference was not statistically significant. In summary, pLH treatment on Day 0 increased ovulatory response but not pregnancy rate. Cows treated with GnRH/PGF/pLH had the highest pregnancy rate to TAI, but progesterone concentrations after TAI were not increased. In addition, preovulatory follicle diameter did not affect pregnancy rate.

Clinical and research applications of real-time ultrasonography in bovine reproduction: a review.

Transrectal real-time ultrasonography has proved to be a rapid and reliable technique for studying reproductive functions in cattle. Through ultrasonography it is now established that follicular growth occurs in wave-like patterns during each estrous cycle. It has been shown that follicular growth and regression continue during early pregnancy, as well as in the postpartum anestrous period. Ultrasound has also helped us to understand the influence of dominant follicles on medium and small follicles. Among the numerous demonstrated applications of ultrasonography, early pregnancy diagnosis, fetal sexing, and postpartum reproductive management appear to be promising areas for immediate application. The new information that has been generated through ultrasound has thrown light on hitherto poorly understood areas of ovarian follicular dynamics, corpus luteum function, pregnancy establishment, and embryonic development in cattle, thereby opening newer areas for research. Still there is great potential for the continued application of this technology to further our understanding of the reproductive processes and to maximize reproductive efficiency of the bovine species. The significant contributions of real-time ultrasonography to the study of bovine reproduction in general and its practical applications in particular are discussed in this paper. The need for taking up technology assessment studies and for the introduction of low-cost portable equipment are stressed. Literature search for this review was done by scanning Current Contents Series 1991-92, AGRICOLA 1980-92, and MEDLINE 1990-92.

Progesterone supplementation before timed AI increased ovulation synchrony and pregnancy per AI, and supplementation after timed AI reduced pregnancy losses in lactating dairy cows

One of the causes of poor fertility in high producing dairy cows is inadequate progesterone. Therefore, we determined the efficacy of an intravaginal insert containing 1.55 g of progesterone (PRID) given before and/or after timed AI (TAI) on ovarian response, plasma progesterone concentrations, pregnancy per AI (P/AI) and pregnancy losses. Lactating dairy cows at three locations were assigned (Day 0) to an Ovsynch protocol with (N = 294) or without (N = 314) a PRID. The Ovsynch protocol consisted of two injections of 100 μg gonadorelin (GnRH) 9 days apart and one injection of 500 μg cloprostenol (PG) 7 days after the first GnRH treatment. Insertion and removal of PRID occurred concurrent with the first GnRH and PG treatments, respectively. Timed AI was carried out 12 to 16 hours after the second GnRH. Ovarian status of a subset of 217 first service cows had been presynchronized with 2 treatments of PG 14 days apart with the last PG given 12 days before the first GnRH of the Ovsynch protocol. Body condition score (scale of one to five) was recorded at TAI. Ultrasonographic examinations were done in all cows at first GnRH, at PG, at TAI, and 24 hours after TAI for response to treatment and at 32 and 60 days after TAI for confirmation of pregnancy. At 4.5 days after TAI (Day 14), cows that responded to PG and ovulated after the second GnRH treatment were reassigned to receive (N = 223) or not receive (N = 229) a PRID for 7 days. Blood samples were taken for progesterone determination at PG treatment, at TAI, and post TAI on Days 14 and 21. The PRID treatment pre-TAI reduced the percentage of cows ovulating before TAI (5.8% vs. 11.1%), and significantly increased P/AI in nonpresynchronized cows (41.3% vs. 25.1%). Cows ovulating in response to the first GnRH treatment, cyclic cows, and cows with body condition score of 2.75 or more had increased P/AI, but the addition of a PRID pre-TAI to these cows did not increase P/AI. The PRID treatment post TAI did not affect P/AI, but reduced pregnancy losses (6.1% vs. 11.4%) between 32 and 60 days of gestation. The reduction in pregnancy losses tended (P = 0.10) to be significant in acyclic cows receiving a PRID than in those not receiving a PRID (5.6% vs. 33.3%). Plasma progesterone concentrations at PG treatment and on Day 21 (11.5 days after TAI) were linearly associated with P/AI. In conclusion, progesterone supplementation pre-TAI increased P/AI in nonpresynchronized cows. Progesterone supplementation post TAI reduced pregnancy losses, particularly in acyclic cows.

Synchronization of ovulation in cyclic gilts with porcine luteinizing hormone (pLH) and its effects on reproductive function.

The overall objective was to evaluate the use of porcine luteinizing hormone (pLH) for synchronization of ovulation in cyclic gilts and its effect on reproductive function. In an initial study, four littermate pairs of cyclic gilts were given altrenogest (15 mg/d for 14 d). Gilts received 500 microg cloprostenol (Day 15), 600 IU equine chorionic gonadotropin (eCG) (Day 16) and either 5mg pLH or saline (Control) 80 h after eCG. Blood samples were collected every 4h, from 8h before pLH/saline treatment to the end of estrus. Following estrus detection, transcutaneous real-time ultrasonography and AI, all gilts were slaughtered 6d after the estimated time of ovulation. Peak plasma pLH concentrations (during the LH surge), as well as the amplitude of the LH surge, were greater in pLH-treated gilts than in the control (P=0.01). However, there were no significant differences between treatments in the timing and duration of estrus, or the timing of ovulation within the estrous period. In a second study, 45 cyclic gilts received altrenogest for 14-18d, 600 IU eCG (24h after last altrenogest), and 5mg pLH, 750 IU human chorionic gonadotropin (hCG), or saline, 80 h after eCG. For gilts given pLH or hCG, the diameter of the largest follicle before the onset of ovulation (mean+/-S.E.M.; 8.1+/-0.2 and 8.1+/-0.2mm, respectively) was smaller than in control gilts (8.6+/-0.2mm, P=0.05). The pLH and hCG groups ovulated sooner after treatment compared to the saline-treated group (43.2+/-2.5, 47.6+/-2.5 and 59.5+/-2.5h, respectively; P<0.01), with the most synchronous ovulation (P<0.01) in pLH-treated gilts. Embryo quality (total cell counts and embryo diameter) was not significantly different among groups. In conclusion, pLH reliably synchronized ovulation in cyclic gilts without significantly affecting embryo quality.

Comparison of 2 enzyme immunoassays and a radioimmunoassay for measurement of progesterone concentrations in bovine plasma, skim milk, and whole milk

The objective of this study was to compare 2 enzyme immunoassays (EIAs) with a radioimmunoassay (RIA) as to sensitivity and accuracy in the measurement of the progesterone (P4) concentration in bovine plasma, skim milk, and whole milk. The 72 samples from 24 lactating dairy cows expected to have either a high P4 concentration (cows in diestrus or pregnant) or a low P4 concentration (cows in estrus or anestrus) were analyzed by RIA, solid-phase EIA (SPEIA), which included a solvent extraction step, or direct EIA (DEIA) without solvent extraction. The overall mean concentrations of P4 did not differ (P < 0.4) among the assays. However, for the cows that were in diestrus or pregnant, the mean P4 concentrations (and standard error) were higher (P < 0.03), regardless of sample type, with RIA than with SPEIA, at 7.3 (0.7) and 6.1 (0.6) ng/mL, respectively. When only the high-P4 samples analyzed by RIA were compared, the mean P4 concentration was higher (P < 0.001) in whole milk than in skim milk, at 9.8 (1.0) and 4.1 (0.7) ng/mL, respectively. Although the mean P4 concentrations in the low-P4 samples did not differ (P < 0.80) among assays, the proportions of cows with a P4 concentration > or = 1 ng/mL were 3%, 14%, and 44% for RIA, SPEIA, and DEIA, respectively (P < 0.01; DEIA > SPEIA > RIA).

Characterisation of the bacterial microbiota of the vagina of dairy cows and isolation of pediocin- producing Pediococcus acidilactici

BackgroundUterine infections in dairy cows lower profitability of dairy operations. Infections of the reproductive tract are related to the overgrowth of pathogenic bacteria during the first three weeks after parturition. However, alterations in the vaginal microbiota composition in the first weeks after parturition remain poorly documented.ResultsIn this study, bacteria isolated from the vagina of healthy pregnant, and infected postpartum cows were characterised by random amplification of polymorphic DNA (RAPD) analysis and partial 16S ribosomal RNA (rDNA) gene sequencing. Populations of bacilli and lactic acid bacteria of the genera Enterococcus, Lactobacillus, and Pediococcus were present in both healthy and infected cows. Infected cows had a significant increase in the vaginal enteric bacteria population which consisted mainly of Escherichia coli. Three E. coli isolates harboured the gene coding for Shiga-like-toxin (SLT) I or II. Several isolates of the Pediococcus acidilactici were found to produce the bacteriocin pediocin AcH/PA-1. Quantitative PCR analyses of vaginal mucus samples collected from ten metritic cows before and after parturition confirmed the presence of the Lactobacillus group (Lactobacillus spp., Pediococcus spp., Leuconostoc spp., and Weissella spp.); Enterobacteriaceae, E. coli, and bacilli. The presence of the pediocin AcH/PA-1 structural gene and SLT genes were also confirmed with qPCR.ConclusionsIn conclusion, overgrowth of pathogenic bacteria, particularly E. coli, after parturition likely contributes to the development of metritis. Our microbiota analysis extends the information related to the composition of commensal bacteria in the bovine female reproductive tract and may facilitate the development of novel intervention strategies for prevention of uterine infections in dairy cows.

Neither duration of progesterone insert nor initial GnRH treatment affected pregnancy per timed-insemination in dairy heifers subjected to a Co-synch protocol

Our objectives were to: 1) compare response to cloprostenol, synchrony of ovulation, and pregnancy per timed-AI (P/TAI) in a 5 d versus a 7 d Co-synch + PRID protocol (Experiment 1); and 2) investigate whether the initial GnRH is necessary to achieve acceptable P/TAI in a 5 d Co-synch + PRID protocol (Experiment 2) in dairy heifers. In Experiment 1, 64 Holstein heifers, 15 to 17 mo, were assigned by age to receive 100 μg of GnRH and a PRID for 5 or 7 d (PRID5 and PRID7, respectively). At PRID removal 500 μg of cloprostenol (PGF) was given i.m. Heifers received the second GnRH treatment concurrently with TAI at 72 (PRID5) or 56 (PRID7) h after PRID removal. Transrectal ultrasonography monitored ovarian dynamics, ovulation synchrony, and pregnancy status (28 and 45 d after TAI). Plasma progesterone concentrations were determined at PRID removal and TAI. Five of seven heifers that ovulated before TAI became pregnant, and only two heifers did not respond to PGF treatment in the PRID5 group. Five PRID5 and 2 PRID7 heifers failed to ovulate after the second GnRH. However, P/TAI did not differ between PRID5 (59.4%) and PRID7 (58.1%). Overall ovulation response to first GnRH treatment was only 31.7%, and a larger proportion of heifers that did not ovulate became pregnant (65.1 versus 45.0%). In Experiment 2, 56 Holstein heifers, assigned as in Experiment 1, were subjected to a PRID5 protocol with (PRID5G) or without (PRID5NoG) GnRH at PRID insertion; all heifers were TAI 72 h after PRID removal. Transrectal ultrasonography and progesterone determinations were performed as in Experiment 1. Pregnancy per TAI did not differ whether or not heifers received GnRH at PRID insertion (67.9 versus 71.4%). Consistent with our previous findings, seven of nine heifers that ovulated before TAI became pregnant, and only two heifers did not respond to PGF treatment. Combining both experiments, length of proestrus but not ovulatory follicle diameter was identified as a significant predictor of probability of pregnancy 28 d after TAI, with a maximum predicted probability of 80.1% when the length of proestrus was 3 d. In summary, a PRID5 protocol resulted in comparable P/TAI to a PRID7 protocol. Most of the heifers that ovulated before TAI in the PRID5, PRID5G, and PRID5NoG protocols became pregnant. More than one PGF or a GnRH treatment at PRID insertion in a 5 d Co-synch + PRID protocol was not required to achieve acceptable P/TAI in dairy heifers.

Reproductive performance of dairy cows is influenced by prepartum feed restriction and dietary fatty acid source.

The objective of this study was to determine the effects of feed restriction and source of dietary fatty acids during the close-up dry period on postcalving reproductive performance of dairy cattle. Thirty-four days before expected calving, pregnant Holstein cows (n = 72; parity 1 to 5) were randomly assigned to 1 of 6 treatments. Treatments were ad libitum (AL) or 24% feed restriction (FR) in combination with 1 of 3 oilseed supplements at 8% of diet dry matter: canola, linola, or flax to enrich the rations with oleic, linoleic, or linolenic fatty acids, respectively. After calving, cows were fed a common lactation diet that contained no oilseeds. Measurements of uterus, corpus luteum, and follicles were obtained by ultrasonography twice weekly from 7 +/- 1 d after calving until the first ovulation. Cows (n = 66) were subjected to timed artificial insemination (TAI), and pregnancy was determined 32 d later. Feed-restricted cows had lower dry matter intake and lost more body weight prepartum. Energy balance (Mcal/d) was negative in FR cows prepartum but they had a less severe negative energy balance postpartum. The dietary source of fatty acid did not affect energy balance. Cows fed AL had a higher incidence of uterine infections (10/37 vs. 2/35) but tended to have fewer ovarian cysts (2/37 vs. 7/35) than FR cows. Mean (+/-SE) interval from calving to uterine involution did not differ among dietary treatments (26.8 +/- 1.8 d). Interval from calving to first ovulation was longer in cows fed canola than in those fed either linola or flax (34.7 +/- 3.1 vs. 23.7 +/- 3.2 and 21.0 +/- 3.1 d, respectively). A greater percentage of cows fed AL conceived to the first TAI (47.1 vs. 18.8) and tended to have fewer mean days open (157 +/- 10.8 vs. 191 +/- 10.1) than cows fed FR. In summary, FR cows had a lower incidence of uterine infections, but they were less fertile as reflected by a lower percent pregnancy to first TAI and increased days open. Cows fed diets enriched in linoleic or linolenic fatty acids had a lesser incidence of ovarian cysts and ovulated sooner with no effect on energy balance or fertility.

Ovarian and endocrine responses associated with the treatment of cystic ovarian follicles in dairy cows with gonadotropin releasing hormone and prostaglandin F2alpha, with or without exogenous progesterone.

The objectives of this observational study were to document ovarian and endocrine responses associated with the treatment of cystic ovarian follicles (COFs) in dairy cows, using gonadotropin releasing hormone (GnRH) and prostaglandin F2alpha (PGF) with or without exogenous progesterone. A secondary objective was to determine pregnancy establishment following synchronization of ovulation and timed insemination in cows diagnosed with COFs. In trial I, 18 Holstein cows diagnosed with COFs received 2 injections of 100 microg GnRH, 9 d apart, with 25 mg PGF given 7 d after the 1st GnRH. A new follicle developed in all 18 cows after the 1st GnRH, and 83% of cows ovulated following the 2nd GnRH. Cows were inseminated 16 h after the 2nd GnRH. Of the 17 cows available for pregnancy diagnosis, 7 were confirmed pregnant. In trial II, 8 cows with COFs received GnRH and an intravaginal progesterone device (CIDR) concurrently, then PGF 7 d later. The CIDR was removed 2 d after PGF administration. Plasma estradiol concentrations declined following CIDR insertion. In all cows, a new follicle developed following GnRH treatment; estradiol-surge and estrus occurred spontaneously after CIDR-removal. Seven of 8 cows ovulated the new follicle. In dairy cows diagnosed with COFs, treatment with GnRH followed by PGF 7 d later, with or without exogenous progesterone, resulted in the recruitment of a healthy new follicle; synchronization of ovulation and timed insemination resulted in a 41% pregnancy rate.

Impact of selection for residual feed intake on breeding soundness and reproductive performance of bulls on pasture-based multisire mating

There is concern in the beef industry that selecting bulls for feed efficiency based on residual feed intake (RFI) may have a negative impact on bull reproductive performance and fertility. Here we investigated the impact of selection of bulls for low RFI on breeding soundness evaluation (BSE), reproductive performance, and fertility of bulls under natural service in multisire mating groups on pasture. Of the 412 RFI-tested bulls available, 98 (23.8%) were culled for performance, type, temperament, or other reasons, and 88 (21.4%) were culled for failing BSE, for an overall cull rate of 45.1%. From among the 314 bulls subjected to BSE, 32 (10.2%), 20 (6.4%), and 36 (11.4%) were culled for poor feet and legs, scrotal circumference, and semen quality, respectively. The BSE traits were not different (P > 0.10) between bulls categorized as either inefficient (+RFI) or efficient (-RFI), but the proportion of bulls that failed to meet the 60% minimum sperm motility requirement tended (P = 0.07) to be greater in the -RFI group than in the +RFI group (10.2% vs. 4.4%, respectively). In a subpopulation of 115 bulls, individual progressive sperm motility was greater (P < 0.05) in +RFI (85%) than -RFI (80%) bulls. A multisire natural mating experiment was conducted during 2 consecutive breeding seasons (2006 to 2007 and 2007 to 2008) using 18 +RFI and 18 -RFI bulls. The overall calving rate (calves born/cows exposed) was 72.9%. Mean number of progeny per sire was significantly greater (P < 0.01) in -RFI bulls (18.3) than in +RFI bulls (11.8). Selection for feed efficiency based on RFI appears to have no detrimental impact on reproductive performance and fertility in beef bulls bred in multisire groups on pasture. However, the decreased sperm motility and the greater number of progeny per sire associated with -RFI status need further investigation.