Follicular waves and hormonal profiles during the estrous cycle of carriers and non-carriers of the Trio allele, a major bovine gene for high ovulation and fecundity

A high fecundity bovine genotype has recently been discovered and genetic mapping indicates evidence for segregation of a major gene with influence on ovulation rate located on bovine chromosome 10. Cattle carrying the high fecundity allele, referred to as the Trio allele, have multiple ovulations while half-sibling, non-carriers generally have single ovulations. The present study was designed to evaluate follicle wave patterns and associated circulating hormones during the estrous cycle of Trio allele carriers (n = 7) and non-carrier half-sib controls (n = 5). We hypothesized that Trio allele carriers would exhibit multiple smaller dominant follicles and greater circulating FSH than non-carrier controls. The proportion of Trio carrier and non-carrier cows with 2 or 3-wave patterns was not different between genotypes with the majority (>70%) exhibiting 3-wave patterns. Trio carriers had greater (P < 0.01) number of ovulations (∼4 vs ∼1 ovulations) and smaller preovulatory follicles (8.9 vs. 14.9 mm; P < 0.01) than non-carrier controls. However, total luteal tissue volume and circulating progesterone, normalized to the initial ovulation or to the onset of luteolysis, were not different between genotypes (P > 0.10). Follicular waves were found to be associated with an FSH surge in both genotypes. Peak FSH concentration at each follicular wave (3-wave patterns) was not different (P > 0.05) between genotypes, but circulating FSH during the decline and nadir, encompassing the day of deviation, was greater (P < 0.05) in Trio carriers. Despite a difference (P = 0.032) in the length of the estrous cycle (23.0 vs. 25.2 d; Trio carrier and non-carriers respectively), the pattern of follicle growth, such as day of wave emergence, day of follicle deviation, and day of maximum diameter of the dominant follicle, when normalized to the FSH surge of each follicular wave were similar in Trio carriers compared to non-carriers although Trio carriers consistently had much smaller-sized follicles (P < 0.05). Thus, decreased follicle size and greater circulating FSH are key components of the mechanism that produces multiple ovulations in cattle that are carriers of the Trio high fecundity allele.

Embryo production in heifers with low or high dry matter intake submitted to superovulation

This study investigated the influence of feed intake on superovulatory response and embryo production of Nelore heifers. Pubertal heifers were kept in a feedlot and were submitted to the same diets, but with different levels of feed consumption: High (1.7 M; n = 20) or Low (0.7 M; n = 19) feed intake. Heifers in the 1.7 M treatment consumed 170% (2.6% of body weight [BW] in dry matter) and the 0.7 M heifers ate 70% (1.1% of BW in dry matter) of a maintenance diet. After 7 wk on these diets, heifers were treated with eight decreasing doses of follicle-stimulating hormone (FSH) given every 12 h, totaling 133 mg Folltropin (Folltropin-V; Bioniche Animal Health, Canada) per heifer. Seven d after AI, heifers had their uteri flushed and embryos were recovered and graded according to the International Embryo Technology Society standards. Data were analyzed using the GLIMMIX procedure of SAS and results are presented as least-squares means ± SEM (P < 0.05). At the onset of the FSH treatment (Day 0 of the protocol), 1.7 M heifers had greater body condition score (BCS), BW and serum insulin concentrations than 0.7 M heifers (4.1 ± 0.1 vs. 3.0 ± 0.1; 462.5 ± 10.1 vs. 382.7 ± 10.4 kg; and 14.3 ± 1.7 vs. 3.5 ± 0.8 μIU/mL, respectively). The 0.7 M heifers had more follicles ≥6 mm at the time of the last FSH (Day 7; 47.9 ± 6.4 vs. 23.5 ± 4.3 follicles), related to a better follicle superstimulatory response to FSH. Similarly, 0.7 M heifers had more corpora lutea at the time of embryo collection (33.6 ± 1.4 vs. 15.7 ± 0.9) than the 1.7 M heifers, which resulted in greater number of recovered embryos and ova (9.9 ± 0.7 vs. 6.7 ± 0.6) and viable embryos (5.3 ± 0.5 vs. 3.8 ± 0.4), despite having similar proportions of viable embryos (∼62%). A negative correlation between circulating insulin and follicle superstimulatory response to FSH was observed (r = -0.68). Therefore, we conclude that high feed intake, for a long period of time, compromised the superovulatory response and embryo production potential of Bos indicus heifers possibly related to the elevation in circulating insulin.

Effects of dry matter and energy intake on quality of oocytes and embryos in ruminants

The success of herd fertility involves the development of healthy follicles, viable oocytes and embryos capable of establishing and maintaining a pregnancy. Herein we discuss how nutrition interacts with reproduction throughout follicle development and pregnancy establishment, focusing on dry matter and energy intake. High feed intake, especially associated with moderate to high body condition, before and through superstimulation protocols, natural or induced single-ovulations or before ovum pick-up has detrimental effects on the quality of oocytes or embryos. Feed restriction or high energy supply can be used strategically to obtain either more or better quality oocytes or embryos. Altering diets that provide different concentrations of circulating insulin may improve ovarian status, oocyte quality, embryo development and pregnancy establishment and maintenance. Some sources of fat can positively affect reproductive performance, such as polyunsaturated fatty acids, improving embryo quality and pregnancy. In contrast, fat supplementation in the diet may compromise embryo cryotolerance. Finally, nutrition can alter concentrations of circulating or intrafollicular hormones and metabolites and the expression of genes in cattle oocytes and embryos. For an adequate feeding program to benefit reproductive performance, factors such as genetic group, source of energy, metabolic status, physiological status and level of feed intake must be taken into account.

Short communication: Follicle superstimulation before ovum pick-up for in vitro embryo production in Holstein cows

The objective was to evaluate in vitro embryo production (IVEP) in nonlactating Holstein cows after ovarian superstimulation. Cows were randomly assigned in a crossover design to 1 of 2 groups: control (n=35), which was not synchronized and not treated with hormones before ovum pick-up (OPU), or hormone-treated (n=35), in which wave emergence was synchronized and animals treated with porcine (p)-FSH in the presence of norgestomet before OPU. In the hormone-treated group, all follicles ≥7mm in diameter were aspirated for synchronization of wave emergence and cows received a norgestomet ear implant. After 36h, treatment with p-FSH (6 doses of 40mg each, 12h apart, i.m.) started. Ovum pick-up from follicles >2mm in diameter was performed 44h after the last p-FSH (coasting). Then, IVEP was performed. The total number of cumulus-oocyte complexes recovered (16.0 vs. 20.5±2.2) and number of grades I to III (viable) oocytes (10.7 vs. 12.3±1.6) did not differ between hormone-treated and control groups Additionally, no differences were found in the number of blastocysts per cow per OPU (3.0 vs. 2.6±0.5) or in blastocyst rates (17.1 vs. 12.2±2.4%) between hormone-treated and control, respectively. Thus, in this study, ovarian follicle superstimulation with p-FSH followed by coasting in nonlactating Holstein cows that had synchronization of wave emergence and progestin supplementation did not improve oocyte quality or IVEP compared to no hormonal treatment.

Effects of whole flaxseed, raw soybeans, and calcium salts of fatty acids on measures of cellular immune function of transition dairy cows

The objective of the current study was to evaluate the effects of supplemental n-3 and n-6 fatty acid (FA) sources on cellular immune function of transition dairy cows. Animals were randomly assigned to receive 1 of 4 diets: control (n=11); whole flaxseed (n-3 FA source; n=11), 60 and 80g/kg of whole flaxseed [diet dry matter (DM) basis] during pre- and postpartum, respectively; whole raw soybeans (n-6 FA source; n=10), 120 and 160g/kg of whole raw soybeans (diet DM basis) during pre- and postpartum, respectively; and calcium salts of unsaturated FA (Megalac-E, n-6 FA source; n=10), 24 and 32g/kg of calcium salts of unsaturated FA (diet DM basis) during pre- and postpartum, respectively. Supplemental FA did not alter DM intake and milk yield but increased energy balance during the postpartum period. Diets containing n-3 and n-6 FA sources increased phagocytosis capacity of leukocytes and monocytes and phagocytosis activity of monocytes. Furthermore, n-3 FA source increased phagocytic capacity of leukocytes and neutrophils and increased phagocytic activity in monocytes and neutrophils when compared with n-6 FA sources. Supplemental FA effects on adaptive immune system included increased percentage of T-helper cells, T-cytotoxic cells, cells that expressed IL-2 receptors, and CD62 adhesion molecules. The results of this study suggest that unsaturated FA can modulate innate and adaptive cellular immunity and trigger a proinflammatory response. The n-3 FA seems to have a greater effect on phagocytic capacity and activity of leukocytes when compared with n-6 FA.

Expression of estrus improves fertility and decreases pregnancy losses in lactating dairy cows that receive artificial insemination or embryo transfer

The objective was to evaluate if expression of estrus by dairy cattle altered fertility in timed artificial insemination (AI; n=5,430) or timed embryo transfer (ET; n=2,003) programs that used estradiol and progesterone (P4) to synchronize ovulation. Ovarian ultrasonography was performed on d 0 (time of AI) and 7 to determine ovulatory follicle diameter and ovulation. Only cows with a visible corpus luteum on d 7 were used in this study. At the time of controlled internal drug release removal, all cows received a tail-head device for detection of estrus and were considered in estrus when the paint of the device was completely removed by d 0. Circulating P4 concentrations were evaluated on d 7. Pregnancies per AI (P/AI) or ET (P/ET) were determined by ultrasonography on d 32 and 60. At d-32 pregnancy diagnosis, cows with expression of estrus had increased P/AI [no estrus=25.5% (222/846) vs. estrus=38.9% (1,785/4,584)] and P/ET [no estrus=32.7% (193/606) vs. estrus=46.2% (645/1,397)]. Similarly, at d-60 pregnancy diagnosis, expression of estrus increased P/AI [no estrus=20.1% (179/846) vs. estrus=33.3% (1,530/4,584)] and P/ET [no estrus=25.1% (150/606) vs. estrus=37.5% (525/1,397)]. Pregnancy loss was lower in cows that expressed estrus in timed AI [TAI; no estrus=20.1% (43/222) vs. estrus 14.4% (255/1,785)] and timed ET [TET; no estrus=22.7% (43/193) vs. estrus=18.6% (120/645)] compared with cows with no estrus. Independent of expression of estrus cows ovulating either too small or too large of follicles had lower P/AI. No effect of ovulatory follicle diameter on P/ET was noted in cows that expressed estrus; although, cows that did not express estrus tended to have lower P/ET if they ovulated larger follicles. In cows that showed estrus, follicle diameter did not affect pregnancy loss, but cows that did not show estrus and ovulated larger follicles tended to have greater pregnancy loss after TAI and had greater pregnancy loss on TET. A positive effect of d-7 P4 concentrations on P/AI was observed, independent of estrus. In contrast, no effect of P4 was found on d 7 on P/ET. Thus, expression of estrus during protocols for TAI or TET is associated with an increase in fertility and reduction in pregnancy loss. During TAI programs, optimizing follicle diameter and increasing circulating P4 on d 7 after AI were also associated with increased fertility, independent of expression of estrus. However, in cows with TET, the association of fertility with either ovulatory follicle diameter or P4 on d 7 was less dramatic and seemed to be related to whether cows expressed estrus.

Effect of injectable vitamin E on incidence of retained fetal membranes and reproductive performance of dairy cows

The objectives were to evaluate the effects of injectable vitamin E during the last 3 wk prepartum on the incidence of retained fetal membranes (RFM) and reproductive performance. Dairy cows (n=890), 390 Holsteins (132 nulliparous and 258 parous) and 500 crossbred Holstein × Gyr (199 nulliparous and 301 parous), from 3 dairy farms in Brazil were assigned to the study. In all 3 farms, from October to March, prepartum cows grazed tropical grasses and received 2 kg/d of a mixture of finely ground corn, soybean meal, and minerals and vitamins. From April to September prepartum cows received a total mixed ration composed of corn silage, finely ground corn, soybean meal, and minerals and vitamins. During the prepartum period, cows were fed 280 (farm 1), 390 (farm 2), and 480 IU (farm 3) of supplemental vitamin E per day, and throughout postpartum, cows were fed 370 (farm 1), 500 (farm 2), and 600 (farm 3) IU of supplemental vitamin E. Within each farm, cows were randomly assigned to remain as untreated controls or to receive 3 i.m. injections of 1,000 IU each of dl-α-tocopherol administered at 19.2 ± 4.3, 12.9 ± 3.3, and 6.2 ± 2.9 d before calving (VitE). Blood was sampled from 141 cows immediately before enrollment to determine the α-tocopherol and cholesterol statuses. Blood was also sampled and analyzed for concentrations of cortisol and nonesterified fatty acids in the last 3 wk of gestation. The serum concentration of α-tocopherol or α-tocopherol:cholesterol ratio did not differ between treatments and averaged 2.97 ± 0.10 μg/mL and 4.46 ± 0.16 × 10(-3), respectively. In total, 53.2% of the cows had an inadequate concentration of serum α-tocopherol based on the 3.0 μg/mL cut-off for adequacy. The risk of RFM decreased as serum α-tocopherol increased. Milk production did not differ between controls and VitE cows. Treatment with injectable α-tocopherol decreased RFM from 20.1 to 13.5%, decreased incidence of stillbirth from 14.9 to 6.8%, and tended to decrease death by 200 d postpartum. VitE cows tended to have improved pregnancy per insemination at first AI (36.7 vs. 30.1%) because of decreased pregnancy loss from 31 to 62 d of gestation (12.5 vs. 20.5%). Despite a similar insemination rate, VitE cows had 22% greater pregnancy rate than control cows. Cows receiving vitamin E had decreased circulating cortisol and nonesterified fatty acids around calving. In summary, when cows were fed limited amounts of supplemental vitamin E, 28 to 48% of the recommendations, prepartum supplementation with injectable α-tocopherol decreased incidence of RFM and improved reproduction.

In vivo embryo production in cows superovulated 1 or 2 days after ovum pick-up

The present study evaluated superovulatory responses and in vivo embryo production in cows treated with FSH starting 1 or 2 days after ovum pick-up (OPU). Thirty-three non-lactating Nelore cows were subjected to aspiration of all follicles ≥3mm for OPU. After OPU, cows were randomly divided into two groups in which the follicle superstimulatory treatments with FSH started 1 or 2 days after OPU (Groups D1 and D2, respectively). Data are presented as the least squares mean±s.e.m. The number of follicles ≥3mm before OPU was similar between groups (~34); however, cows in Group D2 had more follicles ≥3mm on the first day of FSH (15.2±2.3 vs 7.6±1.7; P=0.04) and a higher ratio of the number of follicles at first FSH/number of follicles before OPU (0.41±0.04 vs 0.24±0.02; P=0.01). In addition, Group D2 cows had a greater superovulatory response than did cows in Group D1 (18.9±2.8 vs 9.1±1.9 corpora lutea, respectively; P<0.03). However, there was no difference in the total number of recovered ova and embryos from cows in Groups D2 and D1 (5.1±1.4 vs 4.9±1.3, respectively; P>0.10). Nevertheless Group D2 cows had more freezable embryos than Group D1 cows (3.2±1.1 vs 1.3±0.5, respectively; P<0.05). Cows from Group D2 had a much higher proportion (P<0.001) of follicles ≥8mm compared with follicles ≥6mm and <8mm at the time of the last treatment with FSH. In conclusion, to obtain a greater production of viable embryos in superovulated cows after OPU, it is recommended to wait at least 2 days before starting FSH treatment.

Effect of adding a gonadotropin-releasing-hormone treatment at the beginning and a second prostaglandin F2α treatment at the end of an estradiol-based protocol for timed artificial insemination in lactating dairy cows during cool or hot seasons of the year

Our hypothesis was that fertility could be increased in a timed artificial insemination (TAI) protocol based on estradiol (E2) and progesterone (P4) by combining GnRH with E2-benzoate at the start of the protocol to increase circulating P4 during preovulatory follicle development and by using 2 prostaglandin F2α (PGF) treatments at the end to decrease P4 near TAI. Lactating Holstein cows (n=1,808) were randomly assigned during the cool or hot season of the year to receive TAI (d 0) following 1 of 3 treatments: (1) control: controlled internal drug-release insert + 2mg of E2-benzoate on d -11, PGF on d -4, controlled internal drug-release insert withdrawal + 1.0mg of E2-cypionate on d -2, and TAI on d 0; (2) 2PGF: identical to control protocol with addition of a second PGF treatment on d -2; (3) GnRH: identical to 2PGF protocol with addition of a 100-μg GnRH treatment on d -11. Pregnancy diagnoses were performed on d 32 and 60 after TAI. Season had major effects on many reproductive measures, with cool season greater than hot season in percentage of cows with corpus luteum (CL) at PGF (62.9 vs. 56.2%), ovulatory follicle diameter (15.7 vs. 14.8mm), expression of estrus (86.7 vs. 79.9%), ovulation following the protocol (89.7 vs. 84.3%), and pregnancies per artificial insemination (P/AI; 45.4 vs. 21.4%). The GnRH protocol increased percentage of cows with CL (control=56.9%; 2PGF=55.8%; GnRH=70.5%) and P4 at PGF (control=3.28±0.22; 2PGF=3.35±0.22; GnRH=3.70±0.21ng/mL), compared with control and 2PGF protocols. The GnRH protocol increased P/AI at the pregnancy diagnosis at 32d [37.3% (219/595)] and 60d [31% (179/595)] after TAI, compared with control [30.0% (177/604); 25.1% (145/604)], with intermediate results with 2PGF protocol [33.2% (196/609); 28.0% (164/609)]. The positive effects of GnRH treatment on P/AI were only detected during the cool season (GnRH=50.9%; 2PGF=44.2%; control=41.0%) and not during the hot season. In addition, the effect of GnRH was only observed in cows with low P4 (<3ng/mL) at the start of the protocol and not in cows that began the protocol with high P4. Furthermore, presence of CL at PGF interacted with follicle diameter such that cows with a CL at PGF had greater P/AI if they ovulated larger rather than smaller follicles near TAI. Thus, fertility to TAI can be improved by inducing ovulation at the beginning of an E2/P4-based protocol using GnRH treatment, particularly during the cool season of the year and in cows with low P4 at the start of the protocol.

Relationship between circulating anti-Müllerian hormone (AMH) and superovulatory response of high-producing dairy cows

The main objective of this study was to evaluate the relationship between circulating anti-Müllerian hormone (AMH) and superovulatory response of dairy cows. Holstein cows (n=72) were milked twice daily and housed and fed individually in tiestalls. All animals were synchronized and flushed at 70±3 d in milk (DIM), near peak production (39.6kg/d). Blood samples for AMH analysis were collected at 3 different stages of a synchronized estrous cycle [at a random stage (40±3 DIM), proestrus (50±3 DIM), and diestrus (57±3 DIM)]. Body weights were measured weekly from calving until embryo collection. Statistical analyses were performed with Proc CORR and Proc GLIMMIX of SAS (SAS Institute Inc., Cary, NC). The 3 AMH samples from individual cows were correlated and not influenced by day of cycle. Surprisingly, AMH tended to be negatively correlated with body weight loss from calving to embryo collection (r=-0.22). More importantly, average AMH was highly associated (r=0.65) with superovulation response (number of corpora lutea on the day of the flush, CLN), total structures collected (r=0.48), and total transferable embryos (r=0.37), but not percentage of fertilized embryos (r=-0.20) or degenerate embryos (r=0.02). When cows were classified into quartiles (Q) of circulating AMH (Q1=0.01 to 82.6pg/mL; Q2=91.1 to 132.5pg/mL; Q3=135.3 to 183.8pg/mL; Q4=184.4 to 374.3pg/mL), we observed a >2-fold difference between first and fourth AMH quartiles in superovulation response (CLN: Q1=12.0±1.5; Q2=14.7±2.0; Q3=17.2±1.2; Q4=25.6±1.5) and embryo production. In conclusion, circulating AMH concentration was strongly associated with superovulation response, and evaluation of AMH could be used to identify cows with greater responses to superstimulation and thus improve efficiency of superovulation programs in dairy cows.

Relationships between fertility and postpartum changes in body condition and body weight in lactating dairy cows

The relationship between energy status and fertility in dairy cattle was retrospectively analyzed by comparing fertility with body condition score (BCS) near artificial insemination (AI; experiment 1), early postpartum changes in BCS (experiment 2), and postpartum changes in body weight (BW; experiment 3). To reduce the effect of cyclicity status, all cows were synchronized with Double-Ovsynch protocol before timed AI. In experiment 1, BCS of lactating dairy cows (n = 1,103) was evaluated near AI. Most cows (93%) were cycling at initiation of the breeding Ovsynch protocol (first GnRH injection). A lower percentage pregnant to AI (P/AI) was found in cows with lower (≤ 2.50) versus higher (≥ 2.75) BCS (40.4 vs. 49.2%). In experiment 2, lactating dairy cows on 2 commercial dairies (n = 1,887) were divided by BCS change from calving until the third week postpartum. Overall, P/AI at 70-d pregnancy diagnosis differed dramatically by BCS change and was least for cows that lost BCS, intermediate for cows that maintained BCS, and greatest for cows that gained BCS [22.8% (180/789), 36.0% (243/675), and 78.3% (331/423), respectively]. Surprisingly, a difference existed between farms with BCS change dramatically affecting P/AI on one farm and no effect on the other farm. In experiment 3, lactating dairy cows (n = 71) had BW measured weekly from the first to ninth week postpartum and then had superovulation induced using a modified Double-Ovsynch protocol. Cows were divided into quartiles (Q) by percentage of BW change (Q1 = least change; Q4 = most change) from calving until the third week postpartum. No effect was detected of quartile on number of ovulations, total embryos collected, or percentage of oocytes that were fertilized; however, the percentage of fertilized oocytes that were transferable embryos was greater for cows in Q1, Q2, and Q3 than Q4 (83.8, 75.2, 82.6, and 53.2%, respectively). In addition, percentage of degenerated embryos was least for cows in Q1, Q2, and Q3 and greatest for Q4 (9.6, 14.5, 12.6, and 35.2% respectively). In conclusion, for cows synchronized with a Double-Ovsynch protocol, an effect of low BCS (≤ 2.50) near AI on fertility was detected, but change in BCS during the first 3 wk postpartum had a more profound effect on P/AI to first timed AI. This effect could be partially explained by the reduction in embryo quality and increase in degenerate embryos byd 7 after AI in cows that lost more BW from the first to third week postpartum.

Effect of feed restriction on reproductive and metabolic hormones in dairy cows

The objective of this trial was to evaluate the effects of feed restriction (FR) on serum glucose, nonesterified fatty acids, progesterone (P4), insulin, and milk production in dairy cows. Eight multiparous Holstein cows, 114 ± 14 d pregnant and 685 ± 39 kg of body weight, were randomly assigned to a replicated 4 × 4 Latin square design with 14-d periods. During the first 8 d of each period, cows in all treatments were fed for ad libitum feed intake. Beginning on d 9 of each period, cows received 1 of 4 treatments: ad libitum (AL), 25% feed restriction (25 FR), 50% feed restriction (50 FR), and 50% of TMR replaced with wheat straw (50 ST). Daily feed allowance was divided into 3 equal portions allocated every 8h with jugular blood samples collected immediately before each feeding through d 14. In addition, on d 12 of each period, blood samples were collected before and at 60, 120, 180, 240, 300, 360, 420, and 480 min after morning feeding. The conventional total mixed ration and total mixed ration with straw averaged 15.1 and 10.8%, 32.1 and 50.5%, and 26.8 and 17.0% for concentrations of crude protein, neutral detergent fiber, and starch, respectively. Cows that were feed and energy restricted had reduced dry matter intake, net energy for lactation intake, circulating glucose concentrations, and milk production, but greater body weight and body condition score losses than AL cows. Circulating concentrations of insulin were lower for cows fed 50 FR (8.27 μIU/mL) and 50 ST (6.24 μIU/mL) compared with cows fed AL (16.65 μIU/mL) and 25 FR (11.16 μIU/mL). Furthermore, the greatest plasma nonesterified fatty acids concentration was observed for 50 ST (647.7 μ Eq/L), followed by 50 FR (357.5 μEq/L), 25 FR (225.3 μEq/L), and AL (156.3 μEq/L). In addition, serum P4 concentration was lower for cows fed AL than cows fed 50 ST and 25 FR. Thus, FR reduced circulating glucose and insulin but increased P4 concentration, changes that may be positive in reproductive management programs.

Increasing length of an estradiol and progesterone timed artificial insemination protocol decreases pregnancy losses in lactating dairy cows

Our hypothesis was that increasing the length of an estradiol and progesterone (P4) timed artificial insemination (TAI) protocol would improve pregnancy per artificial insemination (P/AI). Lactating Holstein cows (n=759) yielding 31 ± 0.30 kg of milk/d with a detectable corpus luteum (CL) at d -11 were randomly assigned to receive TAI (d 0) following 1 of 2 treatments: (8d) d -10 = controlled internal drug release (CIDR) and 2.0mg of estradiol benzoate, d -3 = PGF2α(25mg of dinoprost tromethamine), d -2 = CIDR removal and 1.0mg of estradiol cypionate, d 0 = TAI; or (9 d) d -11 = CIDR and estradiol benzoate, d -4 = PGF2α, d -2 CIDR removal and estradiol cypionate, d 0 TAI. Cows were considered to have their estrous cycle synchronized in response to the protocol by the absence of a CL at artificial insemination (d 0) and presence of a CL on d 7. Pregnancy diagnoses were performed on d 32 and 60. The ovulatory follicle diameter at TAI (d 0) did not differ between treatments (14.7 ± 0.39 vs. 15.0 ± 0.40 mm for 8 and 9 d, respectively). The 9 d cows tended to have greater P4 concentrations on d 7 in synchronized cows (3.14 ± 0.18 ng/mL) than the 8d cows (3.05 ± 0.18 ng/mL). Although the P/AI at d 32 [45 (175/385) vs. 43.9% (166/374) for 8d and 9 d, respectively] and 60 [38.1 (150/385) vs. 40.4% (154/374) for 8d and 9 d, respectively] was not different, the 9 d cows had lower pregnancy losses [7.6% (12/166)] than 8d cows [14.7% (25/175)]. The cows in the 9 d program were more likely to be detected in estrus [72.0% (269/374)] compared with 8d cows [62% (240/385)]. Expression of estrus improved synchronization [97.4 (489/501) vs. 81% (202/248)], P4 concentrations at d 7 (3.22 ± 0.16 vs. 2.77 ± 0.17 ng/mL), P/AI at d 32 [51.2 (252/489) vs. 39.4% (81/202)], P/AI at d 60 [46.3 (230/489) vs. 31.1% (66/202)], and decreased pregnancy loss [9.3 (22/252) vs. 19.8% (15/81)] compared with cows that did not show estrus, respectively. Cows not detected in estrus with small (<11 mm) or large follicles (>17 mm) had greater pregnancy loss; however, in cows detected in estrus, no effect of follicle diameter on pregnancy loss was observed. In conclusion, increasing the length of the protocol for TAI increased the percentage of cows detected in estrus and decreased pregnancy loss.

Effects of acute feed restriction combined with targeted use of increasing luteinizing hormone content of follicle-stimulating hormone preparations on ovarian superstimulation, fertilization, and embryo quality in lactating dairy cows

Multiple metabolic and hormonal factors can affect the success of protocols for ovarian superstimulation. In this study, the effect of acute feed restriction and increased LH content in the superstimulatory FSH preparation on numbers of ovulations, fertilization, and embryo quality in lactating dairy cows was evaluated. Two experiments were performed using a Latin square design with treatments arranged as a 2 × 2 factorial: feed restriction (FR; 25% reduction in dry matter intake) compared with ad libitum (AL) feeding, combined with high (H) versus low (L) LH in the last 4 injections of the superstimulatory protocol. As expected, FR decreased circulating insulin concentrations (26.7 vs. 46.0 μU/mL). Two analyses were performed: one that evaluated the complete Latin square in experiment 2 and a second that evaluated only the first periods of experiments 1 and 2. For both analyses, follicle numbers, ovulation rates, and corpora lutea on d 7 were not different. In the first period analysis of experiments 1 and 2, we observed an interaction between feed allowance and amount of LH on fertilization rates, percentage of embryos or oocytes that were quality 1 and 2 embryos, and number of embryos or oocytes that were degenerate. Fertilization rates were greater for the AL-L (89.4%) and FR-H (80.1%) treatments compared with the AL-H (47.9%) and FR-L (59.9%) treatments. Similarly, the proportion of total embryos or oocytes designated as quality 1 and 2 embryos was greater for AL-L (76.7%) and FR-H (73.4%) treatments compared with AL-H (35.6%) and FR-L (47.3%) treatments. In addition, the number of degenerate embryos was decreased for AL-L (1.3) and FR-H (0.4) treatments compared with the AL-H (2.6) and FR-L (2.3) treatments. Thus, cows with either too low (FR-L) or too high (AL-H) insulin and LH stimulation had lesser embryo production after superstimulation because of reduced fertilization rate and increased percentage of degenerate embryos. Therefore, interaction of the gonadotropin content of the superstimulatory preparation with the nutritional program of the donor cow needs to be considered to optimize success of ovarian superstimulatory protocols.

Effects of deep-horn AI on fertilization and embryo production in superovulated cows and heifers

The primary objective of this study was to determine the effect of site of semen deposition on fertilization rate and embryo quality in superovulated cows. The hypothesis was that deposition of semen into the uterine horns would increase the fertilization rate compared with deposition of semen into the uterine body. The secondary objective was to evaluate the effect of uterine environment on fertilization rate and embryo quality. It was hypothesized that subclinical endometritis at the onset of superstimulation would decrease the fertilization rates and embryo quality. In experiment 1, 17 superovulated heifers were randomly assigned to receive artificial insemination (AI) into the uterine body or uterine horns. The total number of fertilized structures and fertilization rate from superovulated heifers was increased (P = 0.04 and P = 0.02, respectively) when semen was deposited into the uterine horns compared with the uterine body. Other embryo characteristics did not differ based on the site of semen deposition. In experiment 2, 14 lactating dairy cows were superovulated twice and were randomly assigned to receive AI into the uterine body or deep into the uterine horns using a crossover design. Neither fertilization rate nor any other embryo characteristics were improved when semen was placed deep into the uterine horns compared with the uterine body. In experiment 3, 72 superovulated lactating dairy cows were randomly assigned to receive AI into the uterine body or uterine horns. Before initiation of superstimulatory treatments, an endometrial cytology sample was collected from each cow. Ova/embryos were collected by a nonsurgical technique at 70 ± 3 days in milk. Similar to experiment 2, neither fertilization rate nor any other embryo characteristics differed based on the site of semen deposition in experiment 3. The percentage of cows with subclinical endometritis did not differ between treatments. Interestingly, there was a tendency (P = 0.09) for a reduction in embryo recovery rate and a reduction (P = 0.01) in the fertilization rate for cows with subclinical endometritis. In conclusion, deposition of semen into the uterine horns rather than into the uterine body did not improve the fertilization rate or embryo quality in superovulated cows. Subclinical endometritis decreased the fertilization rate in superovulated cows.

Estradiol and progesterone exhibit similar patterns of hepatic gene expression regulation in the bovine model

Female sex steroid hormones, estradiol-17β (E2-17β) and progesterone (P4) regulate reproductive function and gene expression in a broad range of tissues. Given the central role of the liver in regulating homeostasis including steroid hormone metabolism, we sought to understand how E2-17β and P4 interact to affect global gene expression in liver. Ovariectomized cows (n = 8) were randomly assigned to 4 treatment groups applied in a replicated Latin Square design: 1) No hormone supplementation, 2) E2-17β treatment (ear implant), 3) P4 treatment (intravaginal inserts), and 4) E2-17β combined with P4. After 14 d of treatment, liver biopsies were collected, allowing 28 d intervals between periods. Changes in gene expression in the liver biopsies were monitored using bovine-specific arrays. Treatment with E2-17β altered expression of 479 genes, P4 472 genes, and combined treatment significantly altered expression of 468 genes. In total, 578 genes exhibited altered expression including a remarkable number (346 genes) that responded similarly to E2-17β, P4, or combined treatment. Additional evidence for similar gene expression actions of E2-17ß and/or P4 were: principal component analysis placed almost every treatment array at a substantial distance from controls; Venn diagrams indicated overall treatment effects for most regulated genes; clustering analysis indicated the two major clusters had all treatments up-regulating (172 genes) or down-regulating (173 genes) expression. Thus, unexpectedly, common biological pathways were regulated by E2-17β and/or P4 in liver. This indicates that the mechanism of action of these steroid hormones in the liver might be either indirect or might occur through non-genomic pathways. This unusual pattern of gene expression in response to steroid hormones is consistent with the idea that there are classical and non-classical tissue-specific responses to steroid hormone actions. Future studies are needed to elucidate putative mechanism(s) responsible for overlapping actions of E2-17β and P4 on the liver transcriptome.

Effect of increasing GnRH and PGF2α dose during Double-Ovsynch on ovulatory response, luteal regression, and fertility of lactating dairy cows

Ovsynch-type synchronization of ovulation protocols have suboptimal synchronization rates due to reduced ovulation to the first GnRH treatment and inadequate luteolysis to the prostaglandin F2α (PGF2α) treatment before timed artificial insemination (TAI). Our objective was to determine whether increasing the dose of the first GnRH or the PGF2α treatment during the Breeding-Ovsynch portion of Double-Ovsynch could improve the rates of ovulation and luteolysis and therefore increase pregnancies per artificial insemination (P/AI). In experiment 1, cows were randomly assigned to a two-by-two factorial design to receive either a low (L) or high (H) doses of GnRH (Gonadorelin; 100 vs. 200 μg) and a PGF2α analogue (cloprostenol; 500 vs. 750 μg) resulting in the following treatments: LL (n = 263), HL (n = 277), LH (n = 270), and HH (n = 274). Transrectal ultrasonography and serum progesterone (P4) were used to assess ovulation to GnRH1, GnRH2, and luteal regression after PGF2α during Breeding-Ovsynch in a subgroup of cows (n = 651 at each evaluation). Pregnancy status was assessed 29, 39, and 74 days after TAI. In experiment 2, cows were randomly assigned to LL (n = 220) or HH (n = 226) treatment as described for experiment 1. For experiment 1, ovulation to GnRH1 was greater (P = 0.01) for cows receiving H versus L GnRH (66.6% [217/326] vs. 57.5% [187/325]) treatment, but only for cows with elevated P4 at GnRH1. Cows that ovulated to GnRH1 had increased (P < 0.001) fertility compared with cows that did not ovulate (52.2% vs. 38.5%); however, no effect of higher dose of GnRH on fertility was detected. The greater PGF2α dose increased luteal regression primarily in multiparous cows (P = 0.03) and tended to increase fertility (P = 0.05) only at the pregnancy diagnosis 39 days after TAI. Overall, P/AI was 47.0% at 29 days and 39.7% at 74 days after TAI; P/AI did not differ (P = 0.10) among treatments at 74 days (LL, 34.6%; HL, 40.8%; LH, 42.2%; HH, 40.9%) and was greater (P < 0.001) for primiparous cows than for multiparous cows (46.1% vs. 33.8%). For experiment 2, P/AI did not differ (P = 0.21) between H versus L treatments (44.2% [100/226] vs. 40.5% [89/220]). Thus, despite an increase in ovulatory response to GnRH1 and luteal regression to PGF2α, there were only marginal effects of increasing dose of GnRH or PGF2α on fertility to TAI after Double-Ovsynch.

Effect of glucocorticoid-induced insulin resistance on follicle development and ovulation

Polycystic ovarian syndrome (PCOS) is characterized by hyperandrogenemia, polycystic ovaries, and menstrual disturbance and a clear association with insulin resistance. This research evaluated whether induction of insulin resistance, using dexamethasone (DEX), in a monovular animal model, the cow, could produce an ovarian phenotype similar to PCOS. In all of these experiments, DEX induced insulin resistance in cows as shown by increased glucose, insulin, and HOMA-IR (homeostasis model assessment of insulin resistance). Experiment 1: DEX induced anovulation (zero of five DEX vs. four of four control cows ovulated) and decreased circulating estradiol (E2). Experiment 2: Gonadotropin-releasing hormone (GnRH) was administered to determine pituitary and follicular responses during insulin resistance. GnRH induced a luteinizing hormone (LH) surge and ovulation in both DEX (seven of seven) and control (seven of seven) cows. Experiment 3: E2 was administered to determine hypothalamic responsiveness after induction of an E2 surge in DEX (eight of eight) and control (eight of eight) cows. An LH surge was induced in control (eight of eight) but not DEX (zero of eight) cows. All control (eight of eight) but only two of eight DEX cows ovulated within 60 h of E2 administration. Experiment 4: Short-term DEX was initiated 24 h after induced luteal regression to determine if DEX could acutely block ovulation before peak insulin resistance was induced, similar to progesterone (P4). All control (five of five), no P4-treated (zero of six), and 50% of DEX-treated (three of six) cows ovulated by 96 h after luteal regression. All anovular cows had reduced circulating E2. These data are consistent with DEX creating a lesion in hypothalamic positive feedback to E2 without altering pituitary responsiveness to GnRH or ovulatory responsiveness of follicles to LH. It remains to be determined if the considerable insulin resistance and the reduced follicular E2 production induced by DEX had any physiological importance in the induction of anovulation.

Prostaglandin F2α regulation of mRNA for activating protein 1 transcriptional factors in porcine corpora lutea (CL): lack of induction of JUN and JUND in CL without luteolytic capacity

Porcine corpora lutea (CL) develop sensitivity to regression by prostaglandin F2α (PGF2α), termed luteolytic capacity, about 13 d after estrus. We postulated that PGF2α regulation of activating protein 1 (AP-1) transcriptional factor expression underlies acquisition of luteolytic capacity. CL were collected from gilts on day 9 (estrous cycle) or day 17 (pseudopregnancy) before or after PGF2α treatment with mRNA measured for FOS, FOSB, FOSL1, FOSL2, JUN, JUNB, and JUND and the AP-1 target genes CCL2 and SERPINE1. At 0.5 h after PGF2α, both day-9 and day-17 CL had increased (P < 0.01) mRNA for FOS (2,225% and 1,817%), JUNB (237% and 358%), and FOSB (1,060% and 925%). Intriguingly, at 0.5 h after PGF2α there was increased (P < 0.01) mRNA encoding JUN (1,099%) and JUND (300%) in day-17 but not day-9 CL. At 10 h after PGF2α there was elevated FOSB mRNA in day-17 (771%) but not day-9 CL and no PGF2α-induced change in FOS, JUN, JUND, and JUNB mRNA in day-9 or day-17 CL. Treatment with PGF2α increased mRNA for AP-1-responsive genes, CCL2 at 0.5 h (202%) and CCL2 and SERPINE1 at 10 h (719% and 1,515%), only in day-17 CL. Thus, many of the fos family of transcription factors are dramatically induced by PGF2α in CL with or without luteolytic capacity. However, PGF only induced JUN and JUND expression in CL with luteolytic capacity, a finding that may be key for understanding the acquisition of luteolytic capacity, given that JUN is the only AP-1 family member with strong N-terminal trans-activation activity.

Effect of progesterone on magnitude of the luteinizing hormone surge induced by two different doses of gonadotropin-releasing hormone in lactating dairy cows

Ovulation to the first GnRH injection of Ovsynch-type protocols is lower in cows with high progesterone (P4) concentrations compared with cows with low P4 concentrations, suggesting that P4 may suppress the release of LH from the anterior pituitary after GnRH treatment. The objectives of this study were to determine the effect of 1) circulating P4 concentrations at the time of GnRH treatment on GnRH-induced LH secretion in lactating dairy cows and 2) increasing the dose of GnRH from 100 to 200 μg on LH secretion in a high- and low-P4 environment. A Double-Ovsynch (Pre-Ovsynch: GnRH, PGF(2α) 7d later, GnRH 3d later, and Breeding-Ovsynch 7d later: GnRH, PGF(2α) 7d later, and GnRH 48 h later) synchronization protocol was used to create the high- and low-P4 environments. At the first GnRH injection of Breeding-Ovsynch (high P4), all cows with a corpus luteum ≥ 20 mm were randomly assigned to receive 100 or 200 μg of GnRH. At the second GnRH injection of Breeding-Ovsynch (low P4) cows were again randomized to receive 100 or 200 μg of GnRH. Blood samples were collected every 15 min from -15 to 180 min after GnRH treatment, and then hourly until 6h after GnRH treatment. As expected, mean P4 concentrations were greater for cows in the high- than the low-P4 environment. For cows receiving 100 μg of GnRH, the LH peak and area under the curve (AUC) were greater in the low- than in the high-P4 environment. Similarly, for cows receiving 200 μg of GnRH, the LH peak and AUC were greater in the low- than the high-P4 environment. Cows receiving 100 or 200 μg of GnRH had greater mean LH concentration in the low- than the high-P4 environment from 1 to 6h after GnRH treatment. On the other hand, when comparing the effect of the 2 GnRH doses in the high- and low-P4 environments, cows receiving 200 μg of GnRH had a greater LH peak and AUC than cows treated with 100 μg of GnRH both in the high- and low-P4 environments. For the high-P4 environment, mean LH was greater from 1.5 to 5h after GnRH treatment for cows receiving 200 μg of GnRH than for those receiving 100 μg of GnRH. In the low-P4 environment, mean LH was greater for cows receiving 200 μg of GnRH than for those receiving 100 μg of GnRH from 1 to 2.5h after GnRH treatment. We conclude that the P4 environment at GnRH treatment dramatically affects GnRH-induced LH secretion, and that a 200-μg dose of GnRH can increase LH secretion in either a high- or a low-P4 environment.