Ultrasonographic evaluation of endometrial thickness near timed AI as a predictor of fertility in high-producing dairy cows

The objectives were to evaluate changes in endometrial thickness (ET) near the time of a synchronized ovulation and to assess the relationship of ET and fertility in lactating Holstein cows, with or without estrogen supplementation near timed ovulation. In Experiment 1, eight cows were examined with transrectal ultrasonography, once daily for 5 d, starting concurrent with PGF_2α (PGF) treatment during an Ovsynch protocol (GnRH - 7d - PGF - 72h - GnRH). The ET increased rapidly after PGF (from ∼7 to ∼9.5 mm), remained > 9 mm for the next 2 d, then decreased to ∼8 and 7.4 mm, 1 and 2 d, respectively, after the second GnRH. In Experiment 2,642 cows (total of 758 breedings) were subjected to an Ovsynch protocol (GnRH - 7d - PGF - 56h - GnRH - 16h - timed AI); cows received either no further treatment (Ovsynch) or 1 mg of estradiol-17β im 8 h before the second GnRH (Ovsynch + E2). For both uterine horns, ET was measured (∼2 cm from the internal uterine body bifurcation) before E2 treatment (48 h after PGF). In cows with ET ≤ 8 mm vs > 8 mm, rates of ovulation were 86.0% (n = 136) vs 98.1% (n = 472; P < 0.01), respectively, and percentage pregnant per AI (P/AI) were 26.7% (n = 146) vs 42.7% (n = 524; P < 0.01). Treatment with E2 increased P/AI in cows with lower ET (Ovsynch + E2 = 37.0% vs Ovsynch = 23.3%; P = 0.07), but did not significantly improve P/AI in cows with ET > 8 mm (Ovsynch + E2 = 43.4% vs Ovsynch = 42.1%). In conclusion, a single ultrasonographic evaluation of ET in Holstein cows 48 h after PGF treatment in an Ovsynch program was a good predictor of ovulation failure and pregnancy success. Perhaps poor fertility in cows with reduced ET was low peripheral E2 concentrations near AI, poor P4 priming, or luteolysis failure during timed AI procedures.     

Late immature mortality is the major influence on reproductive success of African black beetle, Heteronychus arator (Fabricius) (Coleoptera: Scarabaeidae), in a Mediterranean-climate region of Australia

In field and laboratory studies, mortality of African black beetle, Heteronychus arator, in the winter-rainfall, Mediterranean-type climate region of south-western Australia was higher in the late immature stages during summer than in the early immature stages that occur during spring, a contrast to summer-rainfall climatic regions. Greatest mortality occurred around the pupal stage in contrasting soil types, despite drying differences in summer and supplementary watering in some plots. Sampling of natural populations confirmed experimental results that mortality in late immature stages is the major factor limiting H. arator populations under a Mediterranean-type climate. Inter-generation increase in H. arator abundance was uncommon, explaining the consistent abundance typically observed between years in south-western Australia. Random dispersal of newly emerged adults in autumn was inferred to restore uniformity in adult abundance between areas of varying favourability for immature survival.     

The cow as an induced ovulator: Timed AI after synchronization of ovulation

Timed-AI after synchronization of ovulation has become one of the most used reproductive technologies developed during the past 40 years. Various adaptations of this technology are now extensively used worldwide, in the beef and dairy cattle industry. Our well-cited report, published in Theriogenology in 1995, presented a method termed Ovsynch, that used GnRH and PGF_2α to perform synchronization of ovulation and timed AI in lactating dairy cows. This report introduced Ovsynch, more as a concept of induced ovulation, and demonstrated the ovarian dynamics during the protocol. Validation and improvements on this method were subsequently performed in numerous university studies and on commercial dairies, worldwide. This review will provide a brief historical background, some personal recollections, and certain modifications that have been made in synchronization of ovulation protocols. Each section emphasizes the physiology that underlies the most widely-used synchronization of ovulation protocols and key modifications and some practical application of these protocols on commercial operations. Finally, the effect of timed AI in the US dairy industry and in the Brazilian beef cattle industry are compared. Although numerous studies have been done using these protocols, there is still substantial need for research to improve the synchronization, efficacy, simplicity, and practical application of these protocols.     

Patterns of gene expression in the bovine corpus luteum following repeated intrauterine infusions of low doses of prostaglandin F2alpha

Natural luteolysis involves multiple pulses of prostaglandin F2alpha (PGF) released by the nonpregnant uterus. This study investigated expression of 18 genes from five distinct pathways, following multiple low-dose pulses of PGF. Cows on Day 9 of the estrous cycle received four intrauterine infusions of 0.25 ml of phosphate-buffered saline (PBS) or PGF (0.5 mg of PGF in 0.25 ml of PBS) at 6-h intervals. A luteal biopsy sample was collected 30 min after each PBS or PGF infusion. There were four treatment groups: Control (n = 5; 4 PBS infusions), 4XPGF (4 PGF infusions; n = 5), 2XPGF-non-regressed (2 PGF infusions; n = 5; PGF-PBS-PGF-PBS; no regression after treatments), and 2XPGF-regressed (PGF-PBS-PGF-PBS; regression after treatments; n = 5). As expected, the first PGF pulse increased mRNA for the immediate early genes JUN, FOS, NR4A1, and EGR1 but unexpectedly also increased mRNA for steroidogenic (STAR) and angiogenic (VEGFA) pathways. The second PGF pulse induced immediate early genes and genes related to immune system activation (IL1B, FAS, FASLG, IL8). However, mRNA for VEGFA and STAR were decreased by the second PGF infusion. After the third and fourth PGF pulses, a distinctly luteolytic pattern of gene expression was evident, with inhibition of steroidogenic and angiogenic pathways, whereas, there was induction of pathways for immune system activation and production of PGF. The pattern of PGF-induced gene expression was similar in corpus luteum not destined for luteolysis (2X-non-regressed) after the first PGF pulse but was very distinct after the second PGF pulse. Thus, although the initial PGF pulse induced mRNA for many pathways, the second and later pulses of PGF appear to have set the distinct pattern of gene expression that result in luteolysis.     

Associations between emergence of follicular waves and fluctuations in FSH concentrations during the estrous cycle in ewes

Folliculogenesis was studied daily in 16 interovulatory intervals in 5 Polypay ewes from mid February through April using transrectal ultrasonic imaging. The 3-mm follicles attaining > or = 5 mm on Days--1 (ovulation=Day 0) to 11 showed significant peak numbers on Days 0, 5 and 10. The number of 3- and 4-mm follicles that did not reach > 4 mm was not significant, indicating that these follicles did not manifest a wave pattern. A follicular wave was defined as one or more follicles growing to > or = 5 mm; the day the follicles were 3 mm was the day of wave emergence, and the first wave after ovulation was Wave 1. Waves 1, 2 and 3 emerged on Days -1 to 2,4 to 7 and 8 to 10, respectively. Four interovulatory intervals in April were short (9 to 14 d), indicating the end of the ovulatory season. In the remaining 12 intervals, the ovulatory wave was Wave 3 in one interval, Wave 4 in 8 intervals, and Wave 5 or 6 in 3 intervals. The ovulatory wave followed the rhythmic pattern of Waves 1 to 3 by emerging on Days 11 to 14 in 50% of the intervals. In the remaining intervals, either the ovulatory wave was Wave 4 but did not emerge until Day 16 or other waves intervened between Wave 3 and the ovulatory wave. The longest intervals (22, 24 and 24 d) had >4 waves. Based on a cycle-detection program, peak values of FSH fluctuations were temporally associated with the emergence of waves as indicated by the following: 1) tendency (P < 0.08) for an increase in FSH concentrations between 3 and 2 days before emergence of a wave; 2) close agreement between mean number of waves per interval (mean +/- SEM, 4.1 +/- 0.3) and mean number of identified FSH fluctuations (4.5 +/- 0.3); 3) close agreement in length of interwave intervals (4.0 +/- 0.3) and interpeak (FSH) intervals (3.6 +/- 0.2); 4) positive correlation (r(2)=0.8) for number of the 2 events (follicular waves and FSH fluctuations) within intervals; and 5) a closer (P < 0.01) temporal relationship between the 2 events than would have been expected if the events were independent. The results support a relationship between transient increases in FSH concentrations and emergence of follicular waves throughout the interovulatory interval in Polypay ewes, with the 2 events occurring approximately every 4 d.     

Influence of exogenous steroids, nutrition and calf removal on reproductive performance of anestrous beef cows

Methods for inducing a fertile estrus in anestrous beef cows suckling calves were explored in three studies. Trial 1 . Eighty-two primiparous and pluriparous Brahman-Hereford crossbred and Angus cows suckling calves were divided into four groups: 1) good body condition, high level of nutrition (GH); 2) good body condition, low level of nutrition (GL); 3) poor body condition, high level of nutrition (PH); 4) poor body condition, low level of nutrition (PL). All cows received the Shang Treatment (S). Following treatment, more cows (P<0.05) ovulated in the GH group (95%) than either the GL (61%), PH (58%), or PL (53%) group. Pregnancy rates were low and were not different between groups following the insemination taking place 54 hours after implant removal or after cows had been bred for 21 days. Trial 2 . One hundred fourteen two-year-old Santa Gertrudis-Hereford crossbred cows in poor body condition were divided into four groups. Forty-nine cows received S treatment and 65 cows served as controls (C) with approximately half of each group fed a high (H) or a medium (M) level of nutrition (SH, SM, CH, CM). One cow in the SH group ovulated and was pregnant 21 days after breeding. The remaining cows failed to exhibit estrus, ovulate or become pregnant. Trial 3 . Cows used in this trial were those from Trial 2 which did not exhibit estrus nor had a palpable corpus luteum present 21 days after implant removal. Cows were divided into 1) control (C), 2) wean (W), 3) wean + Syncro-Mate-B (W+SMB) and 4) Syncro-Mate-B + wean (SMB+W). The percentage of cows ovulating by 2 and 40 days after the start of breeding was similar (P>0.05) in the W, W+SMB, and SMB+W groups but all were greater (P<0.05) than the percentage of cows ovulating in the C groups. Pregnancy rates of cows in the W+SMB and SMB+W groups were higher (P<0.05) than pregnancy rates of cows in the W and C groups by two days after the start of breeding. Pregnancy rates 40 days after the start of breeding were higher (P<0.05) for cows in the W, W+SMB) and SMB+W groups than for cows in the C group.     

Dystocia in relationship to size and shape of pelvic opening in Holstein heifers

One hundred twenty-seven Holstein heifers were measured prior to calving to obtain 1) heart girth and 2) the horizontal and vertical pelvic measurement, from which pelvic area was calculated. Dystocia scores were assigned at birth, and the heart girth of the calf and sex of the calf were recorded. There was no difference in the level of dystocia noted in heifers with different pelvic sizes. The major cause of dystocia was size of the calf. A greater proportion of the larger calves was bulls (29% vs 20%). The shape of the pelvic opening may affect dystocia through increased calf size.

Ninety-three pregnant heifers were measured on two or more occasions at approximately 60-day intervals to obtain 1) the heart girth and 2) the horizontal and vertical measurements, from which pelvic area was calculated. These measurements were used to determine heifer growth. The heifer's heart girth grew at a rate of 0.066 cm per day of gestation with a corresponding increase in pelvic area of 2.25 cm² per cm of heart girth, or 0.312 cm per day of gestation.     

Emergence and deviation of follicles during the development of follicular waves in cattle

The nature of emergence and deviation of follicles during follicular waves in cattle was studied in 3 experiments by re-examining data from previous projects. Wave emergence was defined as the day or examination (when more than 1 examination per day) the future dominant follicle was 4 mm (Day 0 or Examination 0). Deviation was defined as the beginning of the greatest difference in growth rates between the 2 largest follicles and between 2 consecutive examinations. The search for deviation in an individual wave was done retrospectively from the examination with the maximum diameter of the second largest follicle. In Experiment 1, follicles were assessed ultrasonically for 28 waves every 8 h. The number of examinations that encompassed the emergence of all growing 3-mm follicles was 10.0 +/-0.5 (mean +/-SEM; equivalent to 3.3 d) and extended from mean Examination -3.1 +/-0.3 to mean Examination 6.0 +/-0.6. A mean of 24 growing 3-mm follicles was found, and the maximal attained diameters were 4 mm (46%), 5 mm (25%), and >/=6 mm (29%). More (P<0.05) 3-mm follicles at Examinations -2 and -1 grew to >/=6 mm than to 4 or 5 mm, whereas more 3-mm follicles at Examinations 2 to 6 grew to only 4 mm. On average, the future dominant follicle appeared as a 3-mm follicle (Examination -2.1 +/-0.2) 6 and 10 h earlier (P<0.03) than for the largest (Examination -1.4 +/-0.3) and second-largest (Examination -0.8 +/-0.4) future subordinates, respectively. This result supported the hypothesis that the future dominant follicle has, on the average, an early developmental advantage. In Experiment 2 (n=33 waves), data were normalized to the day at the beginning of deviation (Day 2.8 +/-0.2) when the mean diameters of the dominant and largest subordinate follicle were 8.5 +/-0.2 mm and 7.2 +/-0.2 mm, respectively. This result suggests that the follicle selected to become dominant, as manifested by deviation, is the first follicle to develop to a decisive stage. In Experiment 3 (n=19 waves), FSH concentrations were lower (P<0.05) on the day at the beginning of deviation (8.5 +/-0.5 ng/ml) than on the day before (10.1 +/-0.8 ng/ml), with no continuing decrease after deviation. This temporal result suggests that the attainment of approximate basal levels of FSH is a component of the deviation mechanism.     

Synchronization of estrus following 7 or 9 day treatment with chlormadinone acetate (CAP)

Synchronization of estrus and fertility were determined in a series of 8 trials. Various levels of chlormadinone acetate (CAP) were fed for either 7 or 9 days. An injection of 5 mg of estradiol valerate and CAP was given at the start of the feeding period. In some trials estradiol 17β was injected near the end of the feeding period. In trial 1, 98% of the CAP-treated heifers were in estrus in a 5-day period, but only 46% conceived at first service compared to 80% in the non-synchronized heifers (P<.01).In trials 2 through 6, 0.25 mg estradiol 17β injected either 60 or 72 hours after the last CAP feeding reduced the interval to ovulation in heifers that ovulated. However, use of estradiol 17β reduced the number of heifers ovulating in most trials.In trials 7 and 8, estrus was effectively synchronized with either 7- or 9-day feeding of 7.5 or 10 mg of CAP daily followed by .5 mg estradiol 17β, 72 hours after the last CAP feeding. Pregnancy rates at first service varied from 21 to 45% in heifers in the synchronized groups, compared to 58% in the controls in trial 7 (P<.05). In trial 8 pregnancy rates at 1st service varied from 29 to 47% in treated heifers compared to 72% in controls (P<.01).In this series of trials, fertility was reduced from 24 to 43% with the use of CAP and estradiol valerate. Conception rates at first service were not improved by varying the length of feeding (7 or 9 days), level of CAP (7.5 or 10 mg) or by attempting to reduce the variation in ovulation time with estradiol 17β. None of the combinations of these three drugs used increased fertility in these trials.     

Lack of complete regression of the Day 5 corpus luteum after one or two doses of PGF2α in nonlactating Holstein cows

The early corpus luteum (CL) (before Day 6) does not regress after a single PGF_2α treatment. We hypothesized that increasing PGF_2α dose or number of treatments would allow regression of the early CL (Day 5). Nonlactating Holstein cows (N = 22) were synchronized using the Ovsynch protocol. On Day 5 (Day 0 = second GnRH treatment), cows were assigned to: (1) control (N = 5): no further treatment; (2) 1PGF (N = 6): one dose of 25 mg PGF_2α; (3) 2PGF (N = 5): two doses of 25 mg PGF_2α (50 mg) given 8 hours apart (second PGF_2α on Day 5 at the same time as the other PGF_2α treatments); (4) DPGF (N = 6): double dose of 25 mg PGF_2α (50 mg) given on Day 5. Blood samples were collected to monitor progesterone (P4) profiles in two periods. In the first period (0 to 24 hours), there were effects of treatment (P = 0.01), time (P < 0.01), and an interaction of treatment and time (P = 0.02). Group 1PGF versus control was different only at 12 hours (P = 0.02). Cows treated with DPGF were different than control at 4 hours (P = 0.04), 12 hours (P < 0.01), and 24 hours (P < 0.01). Only cows treated with 2PGF had lower P4 than control during the entire period and low P4 (0.37 ± 0.17 ng/mL) at 24 hours, usually indicative of luteolysis. In the second period (Day 5 to 15 of the cycle), there were effects of treatment (P < 0.01), time (P < 0.01), and interaction of treatment and time (P = 0.002). Group 1PGF was not different than control from Day 5 to 13 and P4 was greater than control on Day 14 (P = 0.01) and 15 (P < 0.01). Circulating P4 in DPGF cows was lower than control from Day 7 (P = 0.05) through 12 (P < 0.01). Likewise, there were differences between control and 2PGF from Day 7 to 13, but not on Day 14 and 15. On Day 15, all PGF_2α-treated groups had circulating P4 consistent with an active CL. Ultrasound evaluation confirmed that no CL from any group completely regressed during the experiment and no new ovulations occurred to account for functional CL later in cycle. In summary, a double dose of PGF_2α (twice on Day 5 or 8 hours apart) can dramatically decrease P4, consistent with classical definitions of luteolysis; however, these CL recover and become fully functional. Thus, the Day 5 CL of mature Holstein cows do not regress even to two doses of PGF_2α.