Interval from calving to conception 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.

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.

Response of dairy cows treated with bovine somatotropin to a luteolytic dose of prostaglandin F2 alpha

The objective of this study was to evaluate the timing of follicular waves in cows treated with bovine somatotropin (bST) by measuring ovarian responses to a luteolytic dose of PGF 2 alpha on d 12 of the estrous cycle. Thirty lactating cows (26 Holstein and 4 Guernsey) were assigned to receive bST (500 mg; n = 18) or saline (control; 1.5 ml; n = 12) every 14 d for three injection cycles. On d 12 of a synchronized estrous cycle, cows were injected with PGF 2 alpha to induce luteolysis. Following PGF 2 alpha, 9 cows ovulated from the dominant follicle during the first follicular wave (4 cows treated with bST and 5 control cows), and 14 cows ovulated from the dominant follicle during the second follicular wave (8 cows treated with bST and 6 control cows). Of the cows that ovulated during the second follicular wave, cows treated with bST had more class 3 follicles (> or = 10 mm) than did control cows. Concentrations of estradiol rose earlier after PGF 2 alpha injection in cows treated with bST than in control cows. This rise in estradiol was parallel to the development of dominant follicles. Serum concentrations of FSH were decreased in cows treated with bST. During the first and second estruses, equivalent numbers of cows treated with bST and control cows ovulated, but fewer cows treated with bST expressed estrus. These results are consistent with the hypothesis that cows treated with bST have reduced FSH, a faster turnover of dominant follicles, and differences in the timing of follicular waves. Treatment of cows with bST also increased the incidence of undetected estrus.

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.