Luteal Tissue Volume Research Articles

A Circular Economy Approach to Integrate Divergent Ruminant Production Systems: Using Dairy Cow Feed Leftovers to Enhance the Out-of-Season Reproductive Performance in Goats.

Based on a circular economy approach, we evaluated the possible effect of targeted supplementation with leftover feed from dairy cows (i.e., intensive system) on the reproductive performance of crossbred/rangeland goats (i.e., extensive system) in arid Northern Mexico. During the deep-anestrous season (i.e., March-April, 25° North), multiparous goats (n = 38) with a similar body weight (BW) and body condition score (BCS) were randomly assigned to two groups: (1) supplemented group (SG; n = 19; BCS: 1.76 ± 0.07; BW: 43.7 ± 1.8 kg), receiving 400 g goat d-1 of dairy-cow-feed leftovers prior to grazing; and (2) non-supplemented group (NS; n = 19; BCS: 1.76 ± 0.06; BW: 44.3 ± 2.5 kg). Both groups were directed to the rangeland for a period of ≈8 h. While the experimental period lasted 36 d, the experimental breeding considered 11 d (d0-d10). The anovulatory status of goats was ultrasonographically confirmed on days -20, -10, and -1 prior to male-female interaction. Previously, bucks were separated for 3 weeks from the experimental females and received exogenous testosterone every third day (i.e., 50 mg i.m.) prior to mating. With respect to the response variables, namely BW, BCS, blood glucose levels (BGLs), estrus induction (GIE, %), latency to estrus (LTE, h), estrus duration (ED, h), and luteal tissue volume (LTV, mm), no differences (p > 0.05) occurred between experimental groups. However, the response variables, namely goats ovulating (GO, %; 78.9 vs. 47.3), total number of corpuses luteum (TNCL, n; 27 vs. 13), ovulation rate (OR, n; 1.42 vs. 0.73), multiple ovulation (MO, %; 73.3 vs. 55.5), and pregnancy rate on d 36 (PRd36, %, 68.4 vs. 36.8), favored (p < 0.05) the SG over the NS goats. Our results demonstrate that connecting the circularity of two divergent ruminant production systems (i.e., cow-intensive and goat-extensive) by using dairy cows' feed leftovers as a targeted supplementation strategy in anestrous goats under a marginal-rangeland production system enhanced out-of-season reproductive outcomes (i.e., ovulation rate and pregnancy rate), thus benefiting marginal goat producers and their families.

An Enhanced Body Condition Improved Sexual Behavior, Ovarian Structure and Function, and Reproductive Fitness in Rangeland-Crossbred Dairy Goats

The possible effect of body condition score (BCS) on ovarian function, sexual behavior, (i.e., females and males; appetitive and consummative), estrus, ovulation, and reproductive performance was investigated in crossbred dairy goats under extensive conditions. Based on their BCS, female goats (n = 48) were divided into two experimental groups, either with a low (LG; 1.0 ± 0.2 units; n = 26) or with a high BCS (HG: 2.5 ± 0.9 units; n = 22). Bucks n = 4; cc = 2.5. Female sexual behavior (i.e., acceptance of anogenital sniffing and approach, flight, and tail wagging) was higher in the HG (p &lt; 0.05). In addition, bucks exposed to HG goats showed more approach and mounting attempts (p &lt; 0.01). There were no significant differences (p &gt; 0.05) between the groups in either the follicular diameter or size. Interestingly, although follicular volume, pregnancy rate, kidding rate, and total number of kids born alive were higher in the HG goats (p &lt; 0.05), there were no significant differences (p &lt; 0.05) in fetal mortality and prolificacy between the HG and LG goats. In addition, the response variables of female ovulation, total number of corpus luteum, ovulation rate, corpus luteum diameter, and luteal tissue volume were more favorable in the HG goats (p &lt; 0.05). Our research results demonstrate that a higher BCS improves not only the reproductive responses, but also sexual behavior (i.e., female and male). Larger ovarian structures, higher ovulation rates, higher pregnancy and kidding rates, and higher prolificacy were observed in the HG goats managed under a marginal semiarid extensive production system.

Luteotropic effects of human chorionic gonadotropin administered 7.5 days after synchronous estrous induction in Morada Nova ewes

This study was conducted in ewes to assess effects of human chorionic gonadotropin (hCG) administration after imposing an estrous induction treatment regimen. Ewes (n = 115) were treated with a 60 mg medroxyprogesterone-intravaginal-sponge for 6 d plus 200 IU of equine chorionic gonadotropin (eCG) im and 37.5 μg d-cloprostenol im 36 h before sponge removal (Day 0). After natural mating, ewes having at least one corpus luteum (CL; n = 108) were administered either 1 mL of saline (G-Control; n = 53) or 300 IU of hCG (G-hCG; n = 55) on Day 7.5 after sponge removal (Day 0). Ovarian ultrasonography and blood collection were performed on Days 7.5, 13.5, 17.5, 21.5, and 30.5. Accessory CL (aCL) were observed in 81.5 % (G-hCG) and 0.0 % (G-Control) of ewes (P = 0.0001). Diameter, area, and volume of luteal tissue were greater (P < 0.05) in G-hCG from Day 13.5 to 30.5. Progesterone (P4) concentrations were greater (P < 0.05) on Days 13.5, 17.5, 21.5 and 30.5 for ewes of the G-hCG group. Pregnancy percentage was similar (P = 0.25) between groups [47.1 % (G-control) compared with 60.0 % (G-hCG)], although total number of lambs produced by estrous synchronized ewes was greater (P = 0.005) in ewes of the G-hCG group (90.9 % compared with 66.0 %). In conclusion, hCG administration 7.5 days after sponge removal from Morada Nova ewes during the non-breeding season is an effective treatment to induce aCL formation, improve luteal tissue biometry and P4 concentrations, and to enhance the total number of lambs born.

Trio a novel bovine high-fecundity allele: II. Hormonal profile and follicular dynamics underlying the high ovulation rate.

The newly discovered Trio high-fecundity allele produces multiple ovulations in cattle. This study evaluated (1) size and growth rates of follicles in Trio carriers during a synchronized follicular wave, induced by follicle aspiration; (2) follicle-stimulating hormone (FSH) patterns associated with the follicular wave; (3) size of corpora lutea (CL) and circulating progesterone; and (4) intrafollicular estradiol concentrations prior to normal deviation. Trio carriers had mean dominant follicles that were significantly smaller in diameter and volume than noncarriers. Onset of diameter deviation occurred at ∼3 days after the last follicle aspiration in both genotypes despite Trio carriers having much smaller individual follicles. Follicles of Trio carriers grew at a slower rate than noncarrier follicles (∼65% in mm/day or ∼30% in mm3/day) resulting in much smaller individual dominant follicles (∼25% volume). However, total dominant follicle volume, calculated as the sum of all dominant follicles in each animal, was similar in carriers and noncarriers of Trio throughout the entire follicular wave. Circulating FSH was greater in Trio carriers during the 24 h encompassing deviation. Trio carriers had significantly more ovulations than noncarriers, and individual CL volume was smaller, although total luteal tissue volume and circulating P4 were not different. Thus, increased ovulation rate in Trio carriers relates to smaller individual follicles (one-third the volume) near the time of deviation due to slower follicle growth rate, although time of deviation is similar, with increased circulating FSH near deviation leading to selection of multiple dominant follicles in Trio carriers with similar total follicle volume.

Additional small dose of prostaglandin F2α at timed artificial insemination failed to improve pregnancy risk of lactating dairy cows

Two experiments were performed to test the hypothesis that administering PGF2α concurrent with timed artificial insemination (AI) in lactating dairy cows would enhance pregnancy per AI (P/AI). In experiment 1, lactating Holstein cows (n = 289) in one herd were enrolled after a non-pregnancy diagnosis (30–36 d after AI) to synchronize subsequent ovulation before AI. Cows were assigned randomly to receive (im) 10 mg of PGF2α concurrent with timed AI (Day 0; treatment) or no injection (control). Blood samples were collected on Days −3, 0, and 13 to determine serum concentrations of progesterone. Ovaries were scanned via transrectal ultrasonography to determine follicle diameters (Day −3), subsequent ovulation risk (Day 13), and total volume of luteal tissue (Day 13). Diagnosis of pregnancy occurred on Days 32 and 80 after AI. Ovulation risk post-AI exceeded 90% and did not differ between treatments. In addition, PGF2α treatment only numerically increased progesterone (5.7 ± 0.3 vs. 6.2 ± 0.3 ng/mL) or luteal tissue volume (8.9 ± 0.4 vs. 9.8 ± 0.5 ng/mL) on Day 13 by 8.8% (P = .206) or 10.1% (P = .134) in control and treated cows, respectively. Pregnancy per AI at Days 32 (P = .50) and 80 (P = .33) did not differ between treatments. Cows with progesterone >0.5 ng/mL at timed AI had reduced (P < .001) ovulation risk but risk was unaffected by treatment. In experiment 2, lactating dairy cows (n = 1828) in two commercial dairy herds were enrolled at time of insemination (Day 0), and assigned randomly to treatment or control as described in experiment 1. Initial (Days 32–35) and confirmed (Days 63–68) pregnancy diagnosis revealed no differences in P/AI or pregnancy loss. Pregnancy diagnosis on Days 32–35 produced percentage increases in P/AI for primiparous compared with multiparous cows (20.8%; P = .002), for first-service compared with repeat-service cows (26%; P = .001), and cows in one herd compared with the second herd (36%; P < .001). Pregnancy loss was greater (P = .001) for cows inseminated at first (10.0%) vs. later services (5.3%) but was unaffected by treatment. Cows treated with PGF2α in one herd produced more twins than control cows (11.7 vs. 3.2%), whereas no treatment difference was detected in the second herd (5.6 vs. 5.6%), respectively. We conclude that im treatment of lactating dairy cows with 10 mg of PGF2α concurrent with timed AI did not improve P/AI or embryo survival, but increased twinning in one herd.

4 Relationship Between Ovarian Vascularity, Cumulus–Oocyte Morphology and Luteal Development in Four-Month-Old Calves After FSH Stimulation

The objectives of this study were to determine the effect of LH on the blood flow to the ovaries of 4-month-old calves after 2 FSH stimulation protocols, and to examine the relationship between ovarian vascularity after superstimulation to the morphology of the cumulus–oocyte complexes (COC) and luteal function. We hypothesise that ovarian vascularity (detected by 3-dimensional (3D) analysis of Doppler ultrasound cineloops) will increase in response to LH, and the magnitude of change in vascularity would be predictive of (1) a greater proportion of expanded COC, (2) greater development of luteal tissue volume and vascularity at 3 and 7 days after follicle aspiration, and (3) higher levels of plasma progesterone. Ovarian superstimulation was initiated at the beginning of an induced follicular wave in 4-month-old beef calves (n = 16), and beef cattle &gt;16 months of age (control group, adults; n = 8) using either a traditional 4-day or an extended 7-day FSH protocol (n = 8 calves and n = 4 controls per group). Power Doppler ultrasound cineloops were recorded immediately before (i.e. 12 h after the last FSH treatment) and 24 h after LH treatment (before ultrasound-guided follicular aspiration for oocyte collection) to assess ovarian vascularity, and 3 and 7 days after follicular aspiration to assess luteal tissue volume and vascularity. Video segments were analysed in Fiji and Imaris software to obtain the 3D ovarian vascularity index (ratio of blood flow volume to tissue volume). The ovarian vascularity index tended to increase &gt;1.7-fold in response to exogenous LH in both prepubertal calves (pre-LH 1.5 ± 0.4% v. post-LH 2.6 ± 0.7%; P = 0.08) and adult cattle (pre-LH 2.2 ± 0.6% v. post-LH 4.7 ± 0.9%; P = 0.07). Calves with a recovery of &gt;75% of expanded COC had a higher ovarian vascularity index (10.7 ± 2.6% v. 4.8 ± 1.6%; P = 0.06) and luteal vascularity index (15.7 ± 4.5% v. 5.7 ± 2.1%; P &lt; 0.05) 7 days after aspiration than those with &lt;75% expanded COC. Calves in the 7-day FSH protocol had &gt;10-fold higher concentration of plasma progesterone on Day 3 (12.7 ± 7.3 ng mL−1 v. 1.2 ± 0.4 ng mL−1; P &lt; 0.05) and Day 5 (50.6 ± 28.0 ng mL−1 v. 4.5 ± 1.0 ng mL−1; P &lt; 0.05), and ~2-fold higher luteal vascularity index at 7 days after follicle aspiration (13.7 ± 4.6% v. 7.7 ± 2.8%; P &lt; 0.05) than calves in the 4-day FSH protocol, whereas no difference (P &gt; 0.05) was found in control (adult) animals. In conclusion, there was an increase in ovarian vascularity resulting from LH treatment in prepubertal calves and adult cattle. A greater proportion of expansion of COC at 24 h after LH treatment (an indicator of follicular maturation) was related to higher ovarian and luteal vascularity on Day 7 after collection in prepubertal calves, but not in adults. Luteal vascularity on Day 3 was reflective of plasma progesterone concentration, and prepubertal calves in the 7-day FSH protocol had greater plasma progesterone than calves in the 4-day FSH protocol. The use of FSH in calves allows a greater number of follicles for oocyte collection as it does in adult cattle. Research was supported by an NSERC grant.

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.

Concentrations of luteinizing hormone and ovulatory responses in dairy cows before timed artificial insemination

The objective was to determine the incidence of LH surges and ovulatory responses in lactating dairy cows enrolled in a timed artificial insemination (TAI) program. Cows were assigned randomly to 2 presynchronization treatments: (1) Pre10 (n=37): 2 injections of PGF2α (PG; PG-1 and PG-2) 14 d apart (Presynch); or (2) PG-3-G (n=33): one 25-mg injection of PG (Pre-PG) administered 3 d before a 100-µg GnRH injection (Pre-GnRH). Ten days after PG-2 or Pre-PG, all cows were enrolled in a 7-d Ovsynch TAI program [injection of GnRH (GnRH-1) 7 d before PG (PG-3) and GnRH (GnRH-2) administered at either 56 or 72 h after PG-3; TAI at 72 h]. Blood was collected to determine LH at (1) Pre-GnRH: 48 to 80 h after PG-2 and hourly from 72 to 78 h (Pre-GnRH at 72 h); (2) GnRH-1: 0 to 6 h after GnRH-1; and (3) GnRH-2: 48 to 80 h after PG-3 and hourly from 56 to 62 h or 72 to 78 h for cows injected with GnRH-2 at 56 or 72 h after PG-3, respectively. Ovaries were scanned and pregnancy per TAI (P/AI) was diagnosed 31 and 61 d post-TAI by transrectal ultrasonography. The Pre-GnRH injection increased the incidences of LH surges (100 vs. 43%) and ovulation (91 vs. 60%) and subsequent concentrations of progesterone in PG-3-G cows compared with Pre10 cows, respectively. Seven days later, incidence of ovulation (48 to 62%) and occurrence of LH surges (100%) did not differ between treatments after GnRH-1. In contrast, LH concentrations and area under the LH curve of Pre10 cows were greater than that of PG-3-G cows because progesterone was greater in PG-3-G than in Pre10 cows (4.6±0.4 vs. 2.8±0.4 ng/mL), respectively. Concentrations of LH did not differ after GnRH-2 at either 56 or 72 h; however, 1 cow receiving GnRH-2 at 56 h and 3 cows at 72 h had early spontaneous LH surges before GnRH-2. Ovulation was suppressed overall in 210 blood collection windows in cows with elevated progesterone concentrations. When progesterone was <1 ng/mL after either PG-2 or PG-3 injections, GnRH-induced LH surges occurred in more than 90% of cows, and incidence of ovulation exceeded 80%. Pregnancy per AI tended to differ for PG-3-G (56.7%) compared with Pre10 (37.8%) and for 56 h (54.5%) compared with 72 h (38.2%), with the Pre10–72 h treatment combination producing less than half (22.2%) the pregnancies compared with all other treatment combinations. Furthermore, in these same cows, post-TAI luteal tissue volume tended to be compromised. We conclude that incidences of GnRH-induced LH surges and ovulation are suppressed in cows with elevated progesterone, possibly contributing to some loss in P/AI in TAI programs.

Macroscopic and histological characteristics of fluid-filled ovarian structures in dairy cows

The primary objective of this study was to use macroscopic and histological features of corpora lutea with a cavity and anovulatory cystic ovarian structures, present in 90 pairs of abattoir-derived dairy cow ovaries, as the basis to clarify the nomenclature of ovarian structures. Excluding morphologically normal ovarian fol-licles (antrum < 2 cm, wall < 1 mm), there were 27 fluid-filled ovarian structures. Ovulatory structures > 16 mm in diameter were designated as Group A (cavity ≤ 10 mm and wall > 10 mm) or Group B (cavity > 10 mm and wall < 10 mm). The volume of luteal tissue was less (P < 0.05) in Group B than in Group A, whereas that of a solid corpus luteum (CL) was intermediate (least square means ± SEM: 72 ± 1.92, 11.22 ± 1.57 and 5.84 ± 1.92 cm3, respectively). There was a greater proportion (P < 0.05) of small luteal cells in Group B compared to a solid CL, whereas Group A was intermediate (58.6 ± 5.3, 37.4 ± 5.3 and 44.0 ± 4.4%, respectively). Connective tissue was thicker (P < 0.05) in Group B than in Group A (295.4 ± 46.9 vs. 153.9 ± 38.2 μm). Based on the above-mentioned characteristics and differences, Groups A and B were designated as a CL with a cavity and a cystic CL, respectively. Furthermore, there were three groups of anovulatory ovarian structures. Structures in Group C were termed persistent/anovulatory follicles (overall diameter and wall thickness ≤ 20 and 1-3 mm, respectively). Finally, Groups D and E were designated as a follicle-fibrous cyst and a follicle-luteinised cyst (based on histological structure) for anovulatory structures with an overall diameter and wall thickness of ≥ 20 and ≤ 3 mm, and ≥ 20 and ≥ 3 mm, respectively.

Physiological and practical effects of progesterone on reproduction in dairy cattle

The discovery of progesterone (P4) and elucidation of the mechanisms of P4 action have an important place in the history of endocrinology and reproduction. Circulating P4 concentration is determined by a balance between P4 production, primarily by the corpus luteum (CL), and P4 metabolism, primarily by the liver. The volume of luteal tissue and number and function of large luteal cells are primary factors determining P4 production. Rate of P4 metabolism is generally determined by liver blood flow and can be of critical importance in determining circulating P4 concentrations, particularly in dairy cattle. During timed artificial insemination (AI) protocols, elevations in P4 are achieved by increasing number of CL by creating accessory CL or by supplementation with exogenous P4. Dietary manipulations can also alter circulating P4, although practical methods to apply these techniques have not yet been reported. Elevating P4 before the timed AI generally decreases double ovulation and increases fertility to the timed AI. Near the time of AI, slight elevations in circulating P4, possibly due to inadequate luteal regression, can dramatically reduce fertility. After AI, circulating P4 is critical for embryo growth and establishment and maintenance of pregnancy. Many studies have attempted to improve fertility by elevating P4 after timed AI. Our recent meta-analysis and manipulative study indicated small fertility benefits (3% to 3.5%) mostly in primiparous cows. Thus, previous research has provided substantial insight into mechanisms regulating circulating P4 concentrations and actions. Understanding this prior research can focus future research on P4 manipulation to improve reproductive success.

Ovarian characteristics, serum concentrations of progesterone and estradiol, and fertility in lactating dairy cows in response to equine chorionic gonadotropin

We hypothesized that administration of eCG during the proestrous maturation phase of the preovulatory ovarian follicle would increase follicle size and serum estradiol concentrations. Our objectives were to evaluate the effects of eCG administration on preovulatory ovarian follicle size and growth rate, serum concentrations of estradiol and progesterone, estrual activity, posttreatment luteal activity, and pregnancy per AI. Lactating Holstein cows milked thrice daily were enrolled in a Presynch-Ovsynch timed AI program before the first AI. Cows (N = 128) in a single herd were given two doses of prostaglandin F2α (PGF2α) 14 days apart (Presynch), with the second dose 11 days before the onset of an Ovsynch protocol (treatment with GnRH 7 days before and 56 hours after PGF2α, with AI 16 to 18 hours after the second GnRH treatment). Cows were assigned randomly to receive either saline or 400 IU eCG concurrent with PGF2α treatment of the Ovsynch protocol (Day 0). Serum concentrations of progesterone and estradiol were assessed to determine if eCG would increase estrual activity, improve ovulatory response to GnRH, and enhance postovulatory luteal function. Compared with controls, treatment with eCG did not increase diameter or growth rate of the largest follicle during 48 hours after eCG, but tended (P = 0.09) to increase growth rate of the second largest follicle. Serum estradiol concentrations and estrual activity were not altered by eCG. Serum progesterone concentrations did not differ between treatments on Days 0, 2, 4, 9, or 16 after eCG treatment. Number of CL per cow on Days 9 and 16 after administration of eCG did not differ between treatments, but total luteal tissue volume tended (P = 0.06) to be greater on Day 16 for eCG-treated cows compared with controls. Pregnancy per AI at first service was similar between eCG (35.3%) and control cows (39.0%). We concluded that eCG treatment administered 3 days before insemination at the dose of 400 IU failed to increase follicle growth size and growth rate 48 hours after treatment, and did not enhance pregnancy outcomes in dairy cattle programmed for AI at first service.

Improving fertility to timed artificial insemination by manipulation of circulating progesterone concentrations in lactating dairy cattle

This manuscript reviews the effect of progesterone (P4) during timed AI protocols in lactating dairy cows. Circulating P4 is determined by a balance between P4 production, primarily by the corpus luteum (CL), and P4 metabolism, primarily by the liver. In dairy cattle, the volume of luteal tissue is a primary determinant of P4 production; however, inadequate circulating P4 is generally due to high P4 metabolism resulting from extremely elevated liver blood flow. Three sections in this manuscript summarise the role of P4 concentrations before breeding, near the time of breeding and after breeding. During timed AI protocols, elevations in P4 are generally achieved by ovulation, resulting in an accessory CL, or by supplementation with exogenous P4. Elevating P4 before timed AI has been found to decrease double ovulation and increase fertility to the timed AI. Slight elevations in circulating P4 can dramatically reduce fertility, with inadequate luteolysis to the prostaglandin F2α treatment before timed AI being the underlying cause of this problem. After AI, circulating P4 is critical for embryo growth, and for establishment and maintenance of pregnancy. Many studies have attempted to improve fertility by elevating P4 after timed AI with marginal elevations in fertility. Thus, previous research has provided substantial insights into mechanisms regulating circulating P4 concentrations and actions. Understanding this prior research can focus future research on P4 manipulation to improve timed AI protocols.

Human chorionic gonadotropin influences ovarian function and concentrations of progesterone in prepubertal Angus heifers1

The effects of administering hCG on subsequent ovarian structure dynamics and concentrations of progesterone in prepubertal heifers were evaluated. Forty-seven purebred Angus heifers were assigned randomly to 1 of 3 treatments: 1) 100 μg of injection of GnRH (GnRH; n = 16); 2) 1,000 IU injection of hCG (H1000; n = 16); and 3) 500-IU injection of hCG (H500; n = 15). From d -1 to 9 relative to treatment (d 0), daily blood samples were collected to determine concentrations of progesterone and ovaries of each heifer were examined daily by transrectal ultrasonography. Diameter of all follicles ≥ 4 mm and all luteal structures were mapped. Disappearance of the largest follicle occurred within 2 d in a greater percentage (P < 0.05) of all heifers in the H1000 treatment (87.5%) compared with GnRH heifers (43.8%), whereas H500 heifers (73.7%) were intermediate. A new luteal structure formed after follicle disappearance in a greater (P < 0.05) percentage of all heifers treated with H1000 (87.5%) and H500 (73.7%) heifers compared with that in GnRH-treated heifers (18.8%). The largest follicle present in ovaries of H1000 and H500 heifers was smaller (P < 0.05) than that of GnRH heifers from d 2 to 5. Heifers treated with H1000 (1.72 ± 0.19 ng/mL) had peak concentrations of progesterone on d 6 that were greater (P < 0.05) than H500 heifers (1.34 ± 0.20 ng/mL), which were greater than heifers treated with GnRH (0.31 ± 0.19 ng/mL). The mean volume of luteal tissue was greater (P < 0.05) in H1000 heifers (1.54 ± 0.15 cm(3)) than in H500 heifers (1.15 ± 0.15 cm(3)), which was greater (P < 0.05) than in heifers treated with GnRH (0.23 ± 0.15 cm(3)). We conclude that hCG was more effective than GnRH in its ability to cause disappearance of the largest follicle, increase volume of luteal tissue in the subsequent developing luteal structures, and increase concentrations of progesterone in prepubertal heifers. In addition, hCG seems to be more effective when administered at 1,000 IU than at 500 IU.

Administration of human chorionic gonadotropin 7 days after fixed-time artificial insemination of suckled beef cows1

We determined the effects of administering hCG 7 d after a fixed-time AI (TAI) on ovarian response, concentrations of progesterone, and pregnancy rates in postpartum suckled beef cows. Cows at 6 locations received 100 microg of GnRH (Fertagyl, Intervet Animal Health, Millsboro, DE) and a controlled internal drug release (CIDR) device (CIDR EAZI-Breed, Pfizer Animal Health, New York, NY), followed in 7 d by 25 mg of PGF(2alpha) (Lutalyse, Pfizer Animal Health) and CIDR removal. At 64 h after CIDR removal, cows received an injection of GnRH and AI (d 0), and then were stratified by days postpartum and parity and assigned randomly to 2 treatments administered 7 d after TAI: 1) 1 mL of saline (saline; n = 252); or 2) 1,000 IU of hCG (Chorulon, Intervet Animal Health; n = 254). Blood samples were collected on d -21, -10, and 33 relative to TAI (d 0) at all locations, on d 7 and 68 at 5 locations, and on d 14 at 1 location to determine concentrations of progesterone. Transrectal ultrasonography was used to determine pregnancy status on d 33 and 68 at all locations, to monitor response of follicles and corpora lutea (CL) in response to treatment at 1 location (n = 106) on d 7 and 14, and to determine the number of CL present in pregnant cows on d 33 in 3 locations (n = 130). Pregnant cows had greater (P < 0.05) concentrations of progesterone at the time of treatment (d 7) compared with nonpregnant cows (3.7 +/- 0.1 vs. 2.6 +/- 0.2 ng/mL, respectively). On d 14, hCG-treated cows had a greater (P < 0.05) volume of luteal tissue (12.1 +/- 0.5 vs. 7.3 +/- 0.5 cm(3), respectively) and greater concentrations of progesterone (6.8 +/- 0.4 vs. 5.4 +/- 0.5 ng/mL, respectively) compared with saline-treated cows. A greater (P < 0.01) percentage of hCG-treated cows (90.6%) had multiple CL on d 14 compared with saline-treated cows (0%), and a greater percentage of pregnant cows treated with hCG (74.6%) had multiple CL on d 33 compared with saline-treated cows (3.0%). Pregnancy rates of hCG-treated cows (56.3%) tended (P = 0.07) to differ from those of saline-treated cows (50.0%). Concentrations of progesterone in pregnant hCG-treated cows were greater (P < 0.05; 7.7 +/- 0.3 vs. 5.8 +/- 0.3 ng/mL, respectively) on d 33 than for pregnant saline-treated cows, but were similar between treatments on d 68 (7.2 +/- 0.3 vs. 6.7 +/- 0.4 ng/mL, respectively). We conclude that treatment with hCG increased the volume of luteal tissue on d 14 and concentrations of progesterone on d 14 and 33 after TAI. Treatment with hCG tended to increase pregnancy rates at 5 of 6 locations from 1.1 to 27 percentage points (average = 10.2) compared with saline, but cumulative pregnancy rates determined on d 68 after TAI were similar between treatments.

Primeira onda folicular e ovulação de vacas primíparas da raça Holandesa alimentadas com diferentes fontes energéticas durante o período de transição

Avaliou-se o efeito da adição de diferentes fontes energéticas na dieta de vacas leiteiras, durante o período de transição, sobre a primeira onda folicular e o intervalo parto-primeira ovulação. Foram utilizadas 40 vacas primíparas da raça Holandesa, no período de 28 dias antes da data prevista do parto até o 46º dia pós-parto. As vacas foram submetidas a quatro tratamentos (grupos) durante o período de transição: grupo-controle e grupos tratados com, Megalac-E (sais de cálcio de ácidos graxos da soja), soja tostada ou propileno-glicol. Avaliações ultrassonográficas foram realizadas do 10º ao 46º dia pós-parto, com a classificação dos folículos ovarianos em quatro classes (I, II, III e IV) de tamanho e do registro do volume do tecido luteal. Amostras de sangue foram coletadas nos dias 10, 17, 24, 31, 38 e 45 após o parto para análise de progesterona. O padrão de crescimento folicular mais eficiente foi apresentado pelos animais dos grupos Megalac-E e propileno-glicol, que foram caracterizados pela redução no número de folículos de classes I e II e aumento no número de folículos de classes III e IV. Os intervalos entre o parto e a primeira ovulação dos grupos controle, Megalac-E, soja tostada e propileno-glicol foram de 29, 23, 30 e 37 dias, respectivamente (P&lt;0,05).

Migration and neuronal activity of GnRH-1 neurons

The objective was to determine the incidence of LH surges and ovulatory responses in lactating dairy cows enrolled in a timed artificial insemination (TAI) program. Cows were assigned randomly to 2 presynchronization treatments: (1) Pre10 (n = 37): 2 injections of PGF2α (PG; PG-1 and PG-2) 14 d apart (Presynch); or (2) PG-3-G (n = 33): one 25-mg injection of PG (Pre-PG) administered 3 d before a 100-µg GnRH injection (Pre-GnRH). Ten days after PG-2 or Pre-PG, all cows were enrolled in a 7-d Ovsynch TAI program [injection of GnRH (GnRH-1) 7 d before PG (PG-3) and GnRH (GnRH-2) administered at either 56 or 72 h after PG-3; TAI at 72 h]. Blood was collected to determine LH at (1) Pre-GnRH: 48 to 80 h after PG-2 and hourly from 72 to 78 h (Pre-GnRH at 72 h); (2) GnRH-1: 0 to 6 h after GnRH-1; and (3) GnRH-2: 48 to 80 h after PG-3 and hourly from 56 to 62 h or 72 to 78 h for cows injected with GnRH-2 at 56 or 72 h after PG-3, respectively. Ovaries were scanned and pregnancy per TAI (P/AI) was diagnosed 31 and 61 d post-TAI by transrectal ultrasonography. The Pre-GnRH injection increased the incidences of LH surges (100 vs. 43%) and ovulation (91 vs. 60%) and subsequent concentrations of progesterone in PG-3-G cows compared with Pre10 cows, respectively. Seven days later, incidence of ovulation (48 to 62%) and occurrence of LH surges (100%) did not differ between treatments after GnRH-1. In contrast, LH concentrations and area under the LH curve of Pre10 cows were greater than that of PG-3-G cows because progesterone was greater in PG-3-G than in Pre10 cows (4.6 ± 0.4 vs. 2.8 ± 0.4 ng/mL), respectively. Concentrations of LH did not differ after GnRH-2 at either 56 or 72 h; however, 1 cow receiving GnRH-2 at 56 h and 3 cows at 72 h had early spontaneous LH surges before GnRH-2. Ovulation was suppressed overall in 210 blood collection windows in cows with elevated progesterone concentrations. When progesterone was <1 ng/mL after either PG-2 or PG-3 injections, GnRH-induced LH surges occurred in more than 90% of cows, and incidence of ovulation exceeded 80%. Pregnancy per AI tended to differ for PG-3-G (56.7%) compared with Pre10 (37.8%) and for 56 h (54.5%) compared with 72 h (38.2%), with the Pre10–72 h treatment combination producing less than half (22.2%) the pregnancies compared with all other treatment combinations. Furthermore, in these same cows, post-TAI luteal tissue volume tended to be compromised. We conclude that incidences of GnRH-induced LH surges and ovulation are suppressed in cows with elevated progesterone, possibly contributing to some loss in P/AI in TAI programs.

Concentrações séricas hormonais em vacas azebuadas submetidas à baixa e alta ingestão alimentar

O objetivo deste trabalho foi avaliar a influência da ingestão alimentar nas concentrações séricas de hormônios reprodutivos e metabólicos em vacas azebuadas. Dezoito vacas foram divididas em dois grupos: 170% (alta ingestão = A) e 66% (baixa ingestão = B) da dieta de manutenção. Com 21 dias nas dietas experimentais, as vacas tiveram o estro sincronizado. Posteriormente, os ovários foram avaliados por ultra-sonografia transretal e sangue foi coletado diariamente até o dia 7 do ciclo (ovulação = dia 1). Na análise estatística, utilizou-se o teste t. As vacas ganharam 1,1 kg por dia no grupo A e perderam 1,5 kg por dia de PV no grupo B. Apesar de não ter havido diferença entre os grupos no diâmetro máximo do folículo ovulatório, o grupo A apresentou pico pré-ovulatório de estradiol sérico menor. Não foi observada diferença entre os grupos quanto ao volume luteal e concentração sérica de progesterona no dia 7 do ciclo e de FSH, IGF-I e insulina séricos no período peri-ovulatório. As dietas experimentais não alteraram a função ovariana e as concentrações séricas de hormônios reprodutivos e metabólicos, com exceção do estradiol, sugerindo que, no grupo de alta ingestão, ocorreu maior metabolismo desse hormônio.

Ovarian Structures and Circulating Steroids in Heifers and Lactating Cows in Summer and Lactating and Dry Cows in Winter

Two experiments compared follicular and luteal development and circulating steroid concentrations from induced luteolysis to ovulation in lactating Holstein cows (n=27; 40.0±1.5kg milk/day) vs. nulliparous heifers (n=28; 11 to 17 mo-old) during summer (Experiment 1), and in lactating (n=27; 45.9±1.4kg milk/d) vs. dry cows (n=26) during winter (experiment 2). All females received PGF2α 6 d after ovulation and were monitored until next ovulation by daily ultrasound and assay of serum progesterone (P4) and estradiol (E2). Every female was used two or three times. In Experiment 1, lactating cows had high incidence of multiple ovulation (63.5%) compared with heifers (1.3%). Among single ovulators, there was no difference in maximal size of ovulatory follicles between lactating cows and heifers (15.8 vs. 16.5mm, respectively). However, lactating cows had lower peak serum E2 (8.6 vs. 12.1pg/ml), took longer to ovulate after luteolysis (4.6 vs. 3.8 d), developed more luteal tissue volume (7293.6 vs. 5515.2mm3), and had lower serum P4 on d 6 after ovulation (2.0 vs. 3.0ng/ml) than heifers (data included multiple ovulators). In experiment 2, multiple ovulations were similar between lactating and dry cows (17.9 vs. 17.2%, respectively). Peak serum E2 was also similar between lactating and dry cows (7.6 vs. 8.5pg/ml) although lactating cows had larger ovulatory follicles (18.6 vs. 16.2±0.4mm). Lactating cows took longer to ovulate (4.8 vs. 4.2 d), developed more luteal tissue (7599 vs. 5139±468mm3), but had similar serum P4 (2.2 vs. 1.9ng/ml) compared with dry cows. Therefore, lactating cows had similar or lower circulating steroid concentrations than dry cows or heifers, respectively, despite having larger ovarian structures.

Evaluating recipient and embryo factors that affect pregnancy rates of embryo transfer in beef cattle

The objectives of this experiment were to determine the effects of corpus luteum characteristics, progesterone concentration, donor-recipient synchrony, embryo quality, type, and developmental stage on pregnancy rates after embryo transfer. We synchronized 763 potential recipients for estrus using one of two synchronization protocols: two doses of PGF2alpha (25 mg im) given 11 d apart (Location 1); and, a single norgestomet implant for 7 d with one dose of PGF2alpha (25 mg im) 24 h before implant removal (Location 2). At embryo transfer, ovaries were examined by rectal palpation and ultrasonography. Of the 526 recipients presented for embryo transfer, 122 received a fresh embryo and 326 received a frozen embryo. Pregnancy rates were greater (P < 0.05) with fresh embryos (83%) than frozen-thawed embryos (69%). Pregnancy rates were not affected by embryo grade, embryo stage, donor-recipient synchrony, or the palpated integrity of the CL. Corpus luteum diameter and luteal tissue volume increased as days post-estrus for the recipients increased. However, pregnancy rates did not differ among recipients receiving embryos 6.5 to 8.5 days after estrus (P > 0.1). There was a significant, positive simple correlation between CL diameter or luteal tissue volume and plasma progesterone concentration (r = 0.15, P < 0.01 and r = 0.18, P < 0.01, respectively). There were no significant differences in mean CL diameter, luteal volume or plasma progesterone concentration among recipients that did or did not become pregnant after embryo transfer. We conclude that suitability of a potential embryo transfer recipient is determined by observed estrus and a palpable corpus luteum, regardless of size or quality.

An ultrasonographic study of luteal function in breeds of sheep with different ovulation rates

Development and demise of luteal structures were monitored using daily transrectal ultrasonography in 2 breeds of sheep differing in ovulation rates (nonprolific Western white-faced cross-bred, n=12 and prolific pure-bred Finn sheep, n=7), during 1 estrous cycle in the mid-breeding season. Jugular blood samples were collected once a day for radioimmunoassay (RIA) of progesterone. The mean diameter of ovulatory follicles was higher in Western white-faced than in Finn ewes (6.4 ± 0.2 and 5.3 f 0.2 mm, respectively; P<0.001). The mean volume of luteal structures was higher (P<0.05) in Western white-faced compared with Finn sheep from Days 5 to 15 of the cycle (Day 0=day of ovulation). This accounted for the higher (P<0.05) total luteal volumes recorded in Western white-faced ewes on Day 7 and from Days 11 to 15, despite the higher ovulation rate in Finn ewes (2.7 ± 0.3 and 1.7 ± 0.2, respectively; P<0.05). Mean serum progesterone concentrations were higher (P<0.05) in Western white-faced than in Finn ewes from Days 4 to 14. Daily total luteal volumes were positively correlated with daily serum progesterone concentrations throughout the cycle in Finn sheep (r≥0.40, P<0.02), and during luteal growth and regression (r>0.60, P≤0.00001) but not during mid-cycle in white-faced ewes (x0.16; P=0.22). During the growth of the corpora lutea (CL), luteal tissue volume increased faster (P<0.05) than serum progesterone concentrations in both breeds of sheep. During luteolysis, the decrease in luteal volumes parallelled that in serum progesterone concentrations in Finn (P=0.11) but not in Western white-faced ewes, where luteal volumes decreased more slowly (P=0.02) in relation to progesterone secretion. Increased ovulation rate in prolific Finn ewes resulted in more but smaller CL, and lower serum progesterone levels compared with nonprolific Western white-faced ewes. We conclude that breed-specific mechanisms exist to control the formation of luteal tissue and progesterone secretion in cyclic ewes differing in prolificacy. The mechanisms may involve ovulation of Graafian follicles at different sizes and inhibitory paracrine effects of CL on co-existing CL. O 1999 by Eisevier science Inc.