Reproductive performance in high producing dairy cows treated with recombinant bovine somatotropin

Pregnancy success of lactating Holstein cows after a single administration of a sustained-release formulation of recombinant bovine somatotropin

Background

Results regarding the use of bovine somatotropin for enhancing fertility in dairy cattle are variable. Here, the hypothesis was tested that a single injection of a sustained-release preparation of bovine somatotropin (bST) during the preovulatory period would improve pregnancy success of lactating dairy cows at first service.

Results

The first experiment was conducted in a temperate region of Mexico. Cows inseminated following natural estrus or timed artificial insemination were given a single injection of bST or a placebo injection at insemination (n = 100 cows per group). There was no significant difference between bST and control groups in the proportion of inseminated cows diagnosed pregnant (29 vs 31% pregnant). The second experiment was performed during heat stress in Florida. Cows were subjected to an ovulation synchronization regimen for first insemination. Cows treated with bST received a single injection at 3 days before insemination. Controls received no additional treatment. As expected, bST did not increase vaginal temperature. Treatment with bST did not significantly increase the proportion of inseminated cows diagnosed pregnant although it was numerically greater for the bST group (24.2% vs 17.8%, 124–132 cows per group). There was a tendency (p = 0.10) for a smaller percent of control cows to have high plasma progesterone concentrations (≥ 1 ng/ml) at Day 7 after insemination than for bST-treated cows (72.6 vs 81.1%). When only cows that were successfully synchronized were considered, the magnitude of the absolute difference in the percentage of inseminated cows that were diagnosed pregnant between bST and control cows was reduced (24.8 vs 22.4% pregnant for bST and control).

Conclusion

Results failed to indicate a beneficial effect of bST treatment on fertility of lactating dairy cows.

Influence of body condition and bovine somatotropin on estrous behavior, reproductive performance, and concentrations of serum somatotropin and plasma fatty acids in postpartum Brahman-influenced cows1,2

Ninety-nine multiparous Brahman-influenced (1/4 to 3/8 Brahman) cows were managed to achieve low (BCS = 4.3 +/- 0.1; n = 50) or moderate (BCS = 6.1 +/- 0.1; n = 49) body condition (BC) to determine the influence of bovine somatotropin (bST) on estrous characteristics, reproductive performance, and concentrations of serum GH and plasma NEFA. Beginning 32 d postpartum, cows within each BC were assigned randomly to treatment with or without bST. Non-bST-treated cows received no treatment, and treated cows were administered bST (Posilac, 500 mg s.c.) on d -35, -21, and -7 before initiation of the breeding season. On d -7, all cows received an intravaginal, controlled internal drug-releasing (CIDR) device. On d 0 (initiation of the 70-d breeding season), the CIDR were removed and cows received prostaglandin F2alpha (PGF2alpha). Blood samples were collected from the median caudal vein of the cows at each bST treatment and at d -28 and 0. Estrous behavior was monitored by radiotelemetry during the first 30 d of the breeding season. Growth hormone was increased (P < 0.05) in low and moderate BC cows treated with bST. The percentage of cows detected in estrus during the first 30 d of the breeding season was decreased (P = 0.05) for low BC (64%) compared with moderate BC (82%) cows. The interval to first estrus tended (P = 0.07) to be shorter in low BC-bST-treated cows (3.7 +/- 1.9 d) than in moderate BC-bST-treated cows (9.6 +/- 1.8 d). During the first 30 d of the breeding season, cows in low BC had a decreased (P = 0.02) number of mounts received and increased (P = 0.001) quiescence between mounts compared with cows in moderate BC. The number of mounts received was reduced (P = 0.04) in bST-treated cows. More (P = 0.02) cows treated with bST became pregnant during the first 3 d of the breeding season compared with non-bST-treated cows. The cumulative first-service conception rate tended (P = 0.07) to be greater for bST-low BC cows than non-bST-treated cows in low or moderate BC. On d 0, NEFA were greater (P < 0.05) in bST-treated vs. non-bST-treated cows. Low BC and bST reduced the intensity of behavioral estrus in postpartum Brahman-influenced cows. However, bST increased the first-service conception rate during the first 30 d of breeding and pregnancy rates during the first 3 d of breeding in postpartum Brahman-influenced cows.

Timing of onset of somatotropin supplementation on reproductive performance in dairy cows

The objective of this field trial was to determine whether delaying the start of recombinant bovine somatotropin (rbST) supplementation from 9 to 10 wk postpartum to 17 to 18 wk postpartum would improve reproductive performance in lactating dairy cows. Cows from nine herds (n = 798 cows; 766 Holsteins, 32 Jerseys) were assigned at random to receive rbST supplementation at 14-d intervals beginning during wk 9 to 10 (n = 399) or wk 17 to 18 (n = 399) after calving. Effects of herd, season of calving, parity, and onset of rbST supplementation (9 to 10 wk vs. 17 to 18 wk) on days to first service and days open were determined. In primiparous but not multiparous cows, there tended to be fewer days to first service and fewer days open when onset of rbST supplementation was delayed. Percentages of cows pregnant at 150, 200, and 250 d postpartum were also examined. Time of onset of rbST did not affect percentages of multiparous cows pregnant at 150, 200, and 250 d postpartum. However, there appeared to be a slight tendency for percentages of pregnant primiparous cows to be greater at 200 and 250 d postpartum for those receiving rbST supplementation beginning at 17 to 18 wk compared to those receiving rbST starting at 9 to 10 wk. In conclusion, delaying the start of rbST supplementation to wk 17 to 18 postpartum had no beneficial effect on reproductive performance of multiparous cows but tended to improve some measures of reproductive performance in primiparous cows.

Effect of calcium soaps of fatty acids and administration of somatotropin on milk production, preovulatory follicular development, and plasma and follicular fluid lipid composition in high yielding dairy cows

The effect of fat and bovine somatotropin (bST) on preovulatory follicular hormones and lipids was evaluated by feeding cows for 150 d from parturition a control diet, a control diet plus 0.55 kg/d of calcium soaps of fatty acids, or a control diet with 500 mg of bST injected every 14 d. Fourteen days after a synchronized or natural estrus, cows were injected with a PGF2 alpha analogue; 48 h later, follicular fluid from all ovarian follicles > 8 mm was aspirated. Cows fed fat or injected with bST produced more milk and milk solids than did control cows, and cows on the bST treatment lost more body condition after calving than did cows on the other treatments. Both treatments changed the proportion of estradiol-active follicles (> 400 ng of estradiol/ml of follicular fluid) and the correlation between follicular fluid estradiol concentration and the total number large follicles per cow. In follicles aspirated between 60 and 90 DIM the percentage of estradiol-active follicles was 67, 40, and 0 for cows on the control, calcium soaps of fatty acids, and bST treatments, respectively. After 90 DIM, no differences existed between treatments in the percentage of estradiol-active follicles. Estradiol concentration in follicular fluid was correlated with DIM at follicle aspiration (r = 0.51). The proportion of oleic acid in free fatty acids in plasma at 50 DIM was lower in control cows and was lower in follicular fluid of estradiol-active follicles. Both calcium soaps of fatty acids and bST had a considerable effect on follicular development and activity and the composition of fatty acids in follicles.

Effect of long-term infusion with recombinant growth hormone-releasing factor and recombinant bovine somatotropin on development and function of dominant follicles and corpora lutea in Holstein cows

The objective of this study was to evaluate the effects of recombinant bovine growth hormone-releasing factor (rGRF) or recombinant bovine somatotropin (rbST) on growth and function of the first-wave dominant follicle and corpus luteum. Primiparous Holstein cows (117 d postpartum) were infused with 12 mg/d of rGRF (n = 10) or 29 mg/d of rbST (n = 10) for 63 d, and non-infused cows (n = 10) were controls. At slaughter on d 5 of an estrous cycle, blood and ovaries were collected and data from cows with a corpus luteum were analyzed (control, n = 8; rGRF, n = 5; rbST, n = 6). Treatment with rGRF or rbST increased somatotropin (ST) and IGF-I in serum similarly compared with controls. In contrast, rbST-treated cows had higher concentrations of ST in follicular fluid (FF) compared with rGRF-treated and control cows. In addition, rbST, but not rGRF, increased the number and decreased the size of estrogen-active follicles (EA; estradiol > progesterone concentrations in FF), increased the abundance of IGF binding proteins-2, -3, and -4 in FF from EA follicles, and increased the number but decreased the size of corpora lutea and decreased concentration of progesterone in serum compared with controls. Based on these results, we concluded that long-term infusion of rbST alters growth and function of the first-wave dominant follicle and the corpus luteum in cattle.

Recombinant bovine somatotropin: association with reproductive performance in dairy cows

A clinical trial was performed to determine the effect of bST on reproductive performance in dairy cows on 4 Michigan dairy farms when bST was used according to labeled directions. Holstein cows (n = 555) at 4 Michigan dairy farms were randomly assigned to receive bovine somatotropin (bST) or to serve as untreated controls. Bovine somatotropin (500 mg, s.c.) was administered every 14 d beginning at 63 to 69 d of lactation and continuing until approximately 21 d prior to the end of lactation or until the producer removed the animal from the herd. A total of 229 (42.57%) animals consisting of 112 (48.91%) controls and 117 (51.09%) bST-treated cows were not diagnosed pregnant and were considered as having reproductive failure by 150 d of lactation and 92 (17.10%) of the animals consisting of 45 (48.91%) controls and 47 (51.09%) bST-treated cows had reproductive failure at the end of their lactation. No significant difference in the incidence of reproductive failure existed between the study treatment groups during either time frame. Cows with cystic ovarian disease had more instances of reproductive failure at 150 d of lactation than cows without this disease. Cows with dystocia, twin births, metritis, displaced abomasum and cystic ovarian disease had more instances of reproductive failure by the end of lactation than cows without these diseases. The bST-treated cows developed more nonspecific off feed conditions during the study lactation and had more twin births at the calving following bST administration compared to control cows. No differences were found between the study treatment groups in calculations of reproductive parameters. Logistic regression analysis found no significant effect of bST on reproductive failure; the odds ratios for the bST treatment effect on reproductive failure at 150 d of lactation and reproductive failure at the end of lactation were 0.95 (95% CI 0.67 to 1.36) and 0.95 (95% CI 0.59 to 1.54), respectively. Overall, bST was not found to have a significant impact on reproductive performance in the herds studied.

Effect of additional cobalt, copper, manganese, and zinc on reproduction and milk yield of lactating dairy cows receiving bovine somatotropin

The objective of this study was to determine whether organically complexed Co, Cu, Mn, and Zn would improve the reproductive performance and milk and milk component production in lactating dairy cows that began receiving bovine somatotropin in the ninth week of lactation. Holstein (n = 50) and Jersey (n = 10) cows were blocked by breed, lactation number, and incidence of retained fetal membranes. Two diets assigned within blocks and fed from parturition until 154 d of lactation were control or control supplemented daily with 26 mg of Co as Co glucoheptonate, 125 mg of Cu as Cu-Lys, 199 mg of Mn as Mn-Met, and 359 mg of Zn as Zn-Met. Cows were fitted with electronic pressure-sensing devices in the second week of lactation for detection of estrus. Ovarian structures were determined via transrectal ultrasonography at 7-d intervals from parturition until observation of the first corpus luteum. Blood samples were taken at 7-d intervals and analyzed for plasma concentrations of progesterone, insulin, and urea nitrogen. Onset of luteal activity was identified by progesterone concentrations > or = 1 ng/ml. Retained fetal membranes increased days to first estrus (detected via electronic estrous detection), first luteal activity, and first corpus luteum in control cows but not in supplemented cows. Days to first observed estrus were greater for control cows than for supplemented cows. Days to first service, days open, days from first service to conception, services per conception, milk yield, milk components, and somatic cell counts were similar for control and supplemented cows. Supplementation with complexed trace minerals effectively reduced days to first estrus.

Plasma GH, IGF-I, and conception rate in cattle treated with low doses of recombinant bovine GH

Blood and uterine concentrations of GH and insulin-like growth factor (IGF)-I are correlated with improved fertility in cattle. We tested incremental doses of a 14-d sustained release recombinant bovine GH (rbGH) to increase blood GH and IGF-I (Experiments 1 and 2). Conception rate after administration of an optimized rbGH dose was also tested (Experiment 3). In Experiment 1, lactating Holstein cows (n = 18) were randomly assigned to receive 0 (n = 5), 100 (n = 5), 200 (n = 5), or 500 (n = 3) mg sc rbGH. Increasing the doses of rbGH was associated with increased serum concentrations of GH and IGF-I. The 100- and 200-mg doses caused an IGF-I release that was below and above, respectively, the perceived optimum response. Therefore, Experiment 2 was designed to test a rbGH dose (167 mg), which was intermediate to the doses tested in Experiment 1. Lactating and nonlactating postpartum beef cows were treated with 0 (n = 9) or 167 (n = 9) mg rbGH at insemination. Plasma concentrations of GH and IGF-I were greater in rbGH-treated cows than in controls. Lactating cows had initial IGF-I concentrations that were lower than nonlactating cows. The 167-mg dose of rbGH increased plasma IGF-I concentrations in lactating cows to the levels of those of nonlactating cows. In Experiment 3, cows and heifers were administered either 0 or 167 mg rbGH at insemination. The conception rate for rbGH-treated and control cows was 54.4 and 49.5% (n = 617), and 46.0 and 46.3% for heifers (n = 1123), respectively. Herd (P<0.01) and parity (P<0.01) affected conception rate, but conception rates for rbGH and control cattle were similar. In summary, low doses of rbGH increased blood GH and restored blood IGF-I concentrations in lactating cows to those of nonlactating cows, but the conception rate in cows and heifers was not affected by administration of 14-d sustained-release rbGH at insemination.

Effect of calcium soaps of fatty acids and administration of somatotropin in early lactation on productive and reproductive performance of high producing dairy cows

This study examined the mechanisms by which calcium soaps of fatty acids and bovine somatotropin (bST) affect production and reproduction of high producing cows. Calcium soaps of fatty acids were fed at 2.2% dry matter, and 500 mg of Zn-sometribove (Monsanto Inc., St Louis, MO) were injected subcutaneously every 14 d from 10 to 150 d in milk (DIM). Production of fat-corrected milk was increased by 3.5 kg/d when calcium soaps of fatty acids were fed, by 6.1 kg/d when bST was administered, and by 7.4 kg/d when calcium soaps of fatty acids were fed and bST was administered. Body weight was similar for cows on all treatments until 85 DIM after which cows that were treated with bST had lower body weights. Body condition scores decreased more for cows treated with bST and began increasing later and more slowly. Treatment with bST resulted in more cows that experienced first ovulation after 30 DIM, and more cows on the control treatment exhibited first estrus before 35 DIM. Days open were greater when bST was administered. After the first artificial insemination, conception rates were similar for cows on the control treatment and for cows fed calcium soaps of fatty acids; conception rates after the first artificial insemination were low for all cows treated with bST. Pregnancy rates at 120 and 150 DIM were decreased by bST. Number of DIM to first ovulation, number of DIM to first estrus, and days open were negatively correlated with glucose and cholesterol concentrations in plasma. Production of fat-corrected milk was correlated with days open and with concentrations of triglycerides in plasma, nonesterified fatty acids, and cholesterol. Increased production had different effects on reproduction when induced by calcium soaps of fatty acids or bST treatment. Some of the adverse effects of bST treatments were alleviated by calcium soaps of fatty acids.

Follicular function in lactating dairy cows treated with sustained-release bovine somatotropin

The objective of this study was to determine the long-term, short-term, and residual effects of bovine somatotropin (bST) on ovarian function. Twenty-six Holstein cows were assigned to one of four groups and given either bST (500 mg) or saline for seven injection cycles (14 d between injections). Groups were 1) seven injection cycles of saline (control), 2) seven injection cycles of bST, 3) three injection cycles of bST followed by four injection cycles of saline, and 4) three injection cycles of saline followed by four injection cycles of bST. Beginning in the middle of the fourth injection cycle, an estrous cycle was synchronized for study. Serum concentrations of bST and insulin-like growth factor I were lowest during saline injections and increased after bST injections. Growth of the first wave dominant follicle was similar; however, start of the second follicular wave was approximately 48 h earlier in those cows treated with bST (groups 2, 3, and 4). Cows treated with somatotropin had a similar pattern of follicular growth, but tended to have more class 1 (3 to 5 mm) follicles and had more class 2 (6 to 9 mm) follicles than did the control cows. Peak concentrations of serum FSH were lower and occurred earlier for the cows treated with bST. There were no differences in the long-term or short-term effects of bST on ovarian function. Furthermore, cows that were switched from bST to saline (group 3) showed a residual effect of bST for up to 3 wk.

Interaction among bovine somatotropin, insulin, and gonadotropins on steroid production by bovine granulosa and thecal cells

The objective of the present study was to determine the interactions among bST, insulin, and gonadotropins on steroid production by granulosa and thecal cells from bovine follicles. Basal production of estradiol by granulosa cells from small (1 to 5 mm) and large (> or = 8 mm) follicles (expressed as picograms of estradiol per 10(5) cells per 24 h) was not affected by 50 or 300 ng/ml of bST, but 300 ng/ml of bST inhibited estradiol production that was induced by FSH plus insulin in cells from small and large follicles. Progesterone production and proliferation by granulosa cells from large follicles were not affected by 3 to 100 ng/ml of bST. In cultures of thecal cells that exhibited a > 3-fold increase in androstenedione production induced by LH, 3 to 30 ng/ml of bST further increased androstenedione production by 29 to 42%, but cell proliferation and progesterone production were unaffected by bST. In cultures of thecal cells that exhibited a < 2-fold increase in androstenedione production induced by LH, 3 to 30 ng/ml of bST inhibited androstenedione production by 32 to 33% and inhibited cell proliferation by 9 to 13%, but progesterone was unaffected by bST. In summary, only pharmacologic doses of bST inhibited estradiol production by granulosa cells, but physiologic doses of bST altered androstenedione production by thecal cells, which indicated that bST might not have an important role in granulosa cell function but might play a role in thecal cell function in cattle.