Mg Of Recombinant bST Research Articles

Serum hormone profiles, pregnancy rates, and offspring performance of Rambouillet ewes treated with recombinant bovine somatotropin before breeding1,2

An experiment was conducted to examine effects of bovine ST (bST) on serum hormone concentrations, pregnancy rates, and offspring performance. Before initiation of a fall breeding period, 75 Rambouillet ewes (68.8 ± 1.5 kg) received an intravaginal insert containing 0.3 g of progesterone (P4) to synchronize onset of estrus. After 12 d, inserts were removed (d 0), and ewes (stratified by BW and age) received either 0 (control, n = 37) or 250 (n = 38) mg of recombinant bST (Posilac, Monsanto, St. Louis, MO, subcutaneously). Ewes were joined with fertile rams 24 h after insert removal. Blood samples were collected from 12 ewes in each treatment group daily from d 0 to 20 after insert removal. Serum IGF-I concentrations were 315 and 437 (± 58) ng/mL in control and bST-treated ewes 2 d after receiving bST (P = 0.02) and remained increased (P < 0.03) in bST-treated ewes throughout the 13-d period (P < 0.05). Serum prolactin (P > 0.10) and estradiol (P = 0.65) were similar between treatments. Serum triiodothyronine (T3) and thyroxine (T4) concentrations were similar (P > 0.20) between treatments from d 0 through 8. Controls had greater (P < 0.04) serum T3 and T4 concentrations than treated ewes did until d 18. Serum P4 was similar (P > 0.10) in control and bST-treated ewes from d 0 through 3 but was increased (P < 0.05) from d 4 to 8 in control ewes. Serum P4 was again similar (P > 0.10) between treatments from d 9 to 20. Serum insulin concentrations were 0.44 and 1.74 (± 0.19) ng/mL in control and bST-treated ewes, respectively, 1 d after receiving bST (P < 0.001) and remained increased (P < 0.03) in bST-treated ewes through d 9 (P < 0.03). Serum glucose was increased (P = 0.003) from d 0 to 10 in bST-treated ewes compared with controls. Thirty-three of 37 (89%) control ewes were pregnant, whereas 27 of 38 (71%) bST-treated ewes were pregnant (P = 0.05). As a percentage of ewes lambing, 61% and 39% of control ewes produced single and twin lambs, respectively, compared with 41% and 59% of bST-treated ewes (P = 0.12). Lamb 60-d adjusted weaning weights were 23.0 and 21.2 (± 0.65) kg for offspring produced by control and bST-treated dams, respectively (P = 0.04). In conclusion, serum IGF-I, insulin, and glucose were greater whereas serum T3, T4, and P4 were less in bST-treated ewes than in controls. Pregnancy rates and offspring adjusted weaning weights were decreased by bST treatment immediately before breeding.

Effect of recombinant bovine somatotropin on milk production and composition of cows with Streptococcus uberis mastitis.

The protective effect of bovine somatotropin (bST) during experimental Streptococcus uberis mastitis in cows was studied. The left quarters of 10 cows were infected with 500 cfu of S. uberis O140J. Five cows were subcutaneously treated with 500 mg of recombinant bST 7 d before and after infection, and 5 control cows received the excipient. In the treated cows, total milk production significantly increased after the first and second bST treatments. After infection, milk production decreased 24 and 40% in the infected quarters, 6 and 14% in the uninfected quarters, and 15 and 28% overall for treated and control cows, respectively. In the bST group, milk production was completely restored after 3 wk, but, in the control group, total production and the production of the infected quarters remained lower than preinfection production. The increase in somatic cell count occurred earlier and more rapidly in the control group, and the return to normal values was also more rapid in these cows. The amount of bacteria in milk was higher in the control cows. Changes in milk composition, such as lactose, protein, fat, Na+, K+, and Cl-, were significantly more pronounced in the control cows. Also, clinical symptoms were more prominent in the control cows. Somatotropin protected the mammary gland from excessive production losses and compositional changes during a subsequent episode of experimentally induced Streptococcus uberis mastitis and significantly improved the normalization of production and composition, which indicates a beneficial effect on the restoration of the integrity of the blood-milk barrier.

Effect of bovine somatotropin on neutrophil functions and clinical symptoms during Streptococcus uberis mastitis.

The effect of recombinant bovine somatotropin (bST) on the chemiluminescence, diapedesis, and expression of adhesion receptors (CD11a, CD11b, CD18) of isolated polymorphonuclear leukocytes was studied. The plasma concentrations of insulin-like growth factor-I (IGF-I), bST, cortisol, and alpha-lactalbumin were also monitored. In addition, general and local clinical symptoms and the differentiation of circulating leukocytes were also studied during experimentally induced Streptococcus uberis mastitis in cows. Ten cows were infected with 500 cfu of S. uberis O140J in both left quarters. Five cows were subcutaneously treated with 500 mg of recombinant bST 7 d before and after infection, and 5 control cows received the excipient. General (fever, tachycardia, inappetance, and depression) and local symptoms (swelling, pain, firmness, and flecks in milk) were more acute, severe, and longer-lasting in control cows. Treatment with bST had no effect on chemiluminescence and diapedesis of circulating polymorphonuclear leukocytes and no effect on the expression of adhesion receptors. Recombinant bST induced significantly higher IGF-I and bST concentrations in plasma. The leukopenia observed after infection was less pronounced in the bST-treated cows, and the number of circulating band neutrophils and metamyelocytes was significantly lower in the treated group. The concentration of cortisol did not differ between both groups, but the blood concentration of alpha-lactalbumin significantly increased in both groups from 6 d after infection. These results showed that treatment with recombinant bST improves animal welfare by protecting the cows from severe local and general clinical symptoms during subsequent S. uberis mastitis, but that it has no effect on chemiluminescence, diapedesis, and the expression of adhesion receptors of circulating polymorphonuclear leukocytes.

Effect of Recombinant Bovine Somatotropin and Calcium Salts of Long-Chain Fatty Acids on Milk from Italian Buffalo

Fifty-one lactating Italian river buffalo were used in an 84-d study to evaluate the effects of recombinant bovine somatotropin (bST) and Ca salts of long-chain fatty acids on productive performance. Treatments were 1) control diet, 2) the control diet plus 0.3 kg/d of added Ca salts of long-chain fatty acids, 3) the control diet plus 320mg of recombinant bST injected every 21 d for four cycles, and 4) the control diet plus 0.3 kg/d of added Ca salts of long-chain fatty acids and 320mg of recombinant bST administered as previously described. Administration of bST and Ca salts of long-chain fatty acids increased milk production. Milk fat percentage was not affected by treatments. The percentage of short-chain fatty acids in milk fat was reduced by the addition of Ca salts. Medium-chain, long-chain, and unsaturated fatty acids in milk fat were increased by bST treatment. Milk protein percentage was decreased by the addition of Ca salts of long-chain fatty acids. Milk casein content, as a percentage of total protein or as a percentage of true protein, was unaffected by bST. Body condition score was lowered by bST administration, but the addition of Ca salts of long-chain fatty acids reduced body condition loss in buffalo that were treated with somatotropin.

Pregnancy Incidence in High Producing Dairy Cows Treated with Recombinant Bovine Somatotropin

Reproductive performance in cows exposed for two lactations to recombinant bST was measured using unconditional logistic regression. Intramuscular administration of 17.2, 51.6, and 86mg of recombinant bST/d per cow started at d 70 postpartum and ended at dry-off or 305 d postpartum. Performance was measured as the cumulative incidence of cows becoming pregnant by 305 d postpartum. Within each parity group, cows treated with bST had higher total milk yield. During the first study lactation, the log odds of a cow becoming pregnant decreased linearly as dose increased, following adjustment for serum cholesterol, blood urea N, average daily milk yield, peak milk yield, net energy balance, and body condition score. However, differences in pregnancy incidence between treated and untreated cows were statistically significant only at the higher dose categories, the 51.6 and 86.0mg of recombinant bST per cow. During the second study lactation, pregnancy rates were similar to those in the first lactation; rates reduced as recombinant bST dose increased. The singular exception was for cows exposed to recombinant bST during the previous lactation but not during the second. In the latter group, previously treated cows had higher pregnancy incidence than did the controls.

Effects of Treatment of Dairy Cows with Recombinant Bovine Somatotropin over Three or Four Lactations

Jersey, Dutch Red and White, and Friesian cows were subcutaneously injected with 640mg of recombinant bST at 28-d intervals from 87 to 115 d after calving through four successive lactations. A TMR (6.72 MJ of NEL and 168g of CP/kg of DM) was fed for ad libitum consumption. The bST effects per day were 3.3kg for milk yield, 189g for fat yield, 109g for protein yield, 157g for lactose yield, 4 MJ of NEL for feed intake, and –4kg for body weight. Responses in blood parameters measured 7 d after injection were –.007ml for glucose, –1.3mg of N/l00ml for urea, 221 μmol/L for 3-hydroxybutyrate, 59 μmol/L for NEFA, 65 ng/L for insulin, 2.8μg/L for thyroxine, and 26.7μg/L for somatotropin. Somatic cell count in milk was 75,000 cells/ml higher in treated cows. Concentrations of NEFA, Ca, Mg, and phosphorus were unaffected. Repeatability of the maximum response in milk yield after bST treatment was low: .2 within and .5 between lactations. Cows treated in the previous lactation had slightly more retained placentas, and birth weight of their calves was 2kg less. No differences were observed between treated and control cows in disease incidence. Six treated cows were culled in third and fourth lactations. No indications for tissue damage, inflammation, or stress after bST injections were detected.

Growth and Subsequent Lactation in Primigravid Holstein Heifers After Prepartum Bovine Somatotropin Treatment

Thirty-seven primigravid Holstein heifers (600.7±9.4kg) were used to determine the effect of recombinant bST, administered during the last trimester of gestation, on growth and subsequent 270-d milk yield. Treatments consisted of daily subcutaneous injections of saline or of 20 or 40mg of recombinant bST. Four weeks before expected date of parturition, 8 heifers (3 receiving saline, 3 receiving 20mg of bST, and 2 receiving 40mg of bST) were fitted with jugular catheters, and blood plasma bST and insulin-like growth factor-I concentrations were determined in samples collected during a 9-h period. Feed efficiency (DMI/gain) was improved in heifers treated with 20mg of bST, but DMI was not affected by treatment. Average daily gain was increased in heifers treated with 20mg of bST, but not in those treated with 40mg of bST. Fat-uncorrected milk yield following prepartum bST treatment was 19% higher in heifers treated with 20mg of bST, but the 40-mg dose of bST did not increase milk yield. Percentage of milk fat was lower in heifers treated with 20mg of bST prepartum, but daily milk fat yields did not differ among groups. Solids-not-fat yield was highest in the group treated previously with 20mg of bST. The higher milk yield of these heifers became significant (P<.05) only after 90 d of lactation. Plasma bST and insulin-like growth factor-I concentrations were both elevated in bST-treated animals. There was indirect evidence that the increased milk in heifers previously treated with 20mg of bST was due to enhanced mammogenesis. However, further research studying changes at the mammary tissue level is needed to confirm this hypothesis.

Kinetics of Amino Acid Extraction by Lactating Mammary Glands in Control and Sometribove-Treated Holstein Cows

Studies of mammary arteriovenous difference were conducted on multiparous lactating Holstein cows (n = 21) on d 35, 70, 105, and 126 of lactation to examine kinetic relationships between arterial concentration and mammary gland extraction of AA. Additionally, these cows were paired by previous lactational performance and assigned to bST-treated or control groups to examine the effect of bST treatment on AA concentration and extraction by lactating mammary glands. Treated cows were injected daily with 40mg of recombinant bST from d 71 through 126 of lactation. Arterial concentrations of Asp, Ser, Asn, Gly, β-aminoisobutyrate, and Met were increased. Concentrations of Val, Ile, Leu, Phe, Orn, and Lys were decreased in bST-treated cows compared with controls. Increased extractions of Asp and Met by mammary glands in treated versus control cows were correlated positively with treatment-induced changes in arterial concentrations of these AA. However, increased mammary extractions of Arg, cystathionine, Leu, and Lys by bST-treated compared with control cows were not correlated with bST-induced changes in arterial concentrations of these AA. Extractions of Asn, His, Thr, Arg, Tyr, Met, cystathionine, cystine, Ile, Phe, Orn, Glu, Gly, Tau, Cit, Leu, and Val were correlated linearly with arterial concentrations (r2 >.15) of each AA. Extractions of Asp, Glu, Ser, Asn, Gly, Gln, Tau, His, Cit, Thr, Pro, Tyr, Val, cystine, Ile, Leu, Trp, Orn, and Lys also were correlated with arteriovenous differences of Met.

Effects of Bovine Somatotropin on Physiologic Responses of Lactating Holstein and Jersey Cows During Hot, Humid Weather

Thirty-one lactating Holstein and Jersey cows were used to determine the effects of daily injections of 0 or 20mg of recombinant bST on physiologic responses during hot, humid weather. Body temperature was determined by measuring milk temperature at each milking. Jugular blood was sampled for serum analysis of selected hormones, blood metabolites, and fatty acids, and arterial blood was sampled for blood pH and blood gas analysis. Milk was characterized for fatty acid composition. Blood pH was unchanged, but partial pressure of blood CO2, blood bicarbonate, base excess, and total CO2 declined with administration of bST. Serum triglycerides increased 89% in cows receiving bST. Blood urea nitrogen tended to decline in cows receiving bST. Serum cortisol, triiodothyronine, and thyroxine did not change, but insulin-like growth factor-1 increased 128% with bST use. Reduced milk short-chain fatty acids, increased milk long-chain fatty acids, and increased blood serum C18:1 fatty acid content occurred in cows administered bST and probably reflected tissue mobilization. Cows administered bST in hot weather had higher milk temperatures. Alterations in physiologic and metabolic measures in association with higher milk temperature suggest an interaction of bST use with hot, humid weather and reflect the need to minimize the effects of heat stress.

Effects of Bovine Somatotropin on Dry Matter Intake, Milk Yield, and Body Temperature in Holstein and Jersey Cows During Heat Stress

Thirty-one lactating Holstein and Jersey cows were used to determine the effect of daily injections of 0 or 20mg of recombinant bST in hot, humid weather. The comparison period lasted 80 d, from mid-June through August. The maximum and minimum ambient temperature and relative humidity averaged 34.6 and 22.2°C and 100 and 59.8%, respectively. Body temperatures of somatotropin-treated Holsteins were elevated over controls by .2 and .3°C at the a.m. and p.m. milkings, respectively, whereas corresponding treatment effects for Jerseys were .5 and .6°C, thus demonstrating a breed by treatment interaction. The response of milk and FCM yields and apparent efficiency of production to somatotropin administration depended on the level of production prior to treatment. Cows at low pretreatment production increased milk and FCM yields to a greater degree than did cows at higher production. A breed by treatment interaction showed that Holsteins increased milk and FCM yields more than Jerseys upon administration of somatotropin. Intake of DM was not affected by treatment. Cows administered bST lost BW and condition score. Greater heat stress was associated with the higher milk production of cows administered bST.

Dose Response to Recombinant Bovine Somatotropin from Weeks 15 to 44 Postpartum in Lactating Dairy Cows

Forty Holstein cows were used in an experiment to determine the response of cows to daily subcutaneous injections of 0, 10.3, 20.6, and 30.9mg of recombinant bST. Injections began between 98 and 104 d postpartum and continued for 29 wk, up to 70 d prepartum, or a maximum of 400 d postpartum. Increasing recombinant bST increased milk yield and 3.5% FCM yield in a linear fashion and by 5.2 and 5.7 kg/d, respectively. Milk composition was not changed, and DM intake as a percentage of BW increased from 3.39 to 3.80% with increasing (30.9 mg/d) bST. Feed efficiency (3.5% FCM/DM intake) was increased from 1.35 to 1.64 with increasing dose, suggesting improved efficiency of use of DM intake, primarily by dilution of maintenance. Increasing bST reduced BW gain linearly from .46 kg/d for the control to .22 kg/d for the 30.9 mg/d treatments. Days open tended to be greatest and number of services tended to be higher for cows treated with 30.9 mg/d bST. Calf birth weight, weight of cows at calving, and incidence of metabolic diseases during subsequent calving were not affected by bST. Somatotropin treatment resulted in somewhat smaller increases in milk yield than that reported in previous studies. Long-term health effects and effects on reproduction could not be determined from the relatively few cows used in this study.