Injections Of Bovine Somatotropin Research Articles

Nutritional Modulation of the Somatotropin/Insulin-Like Growth Factor System: Response to Feed Deprivation in Lactating Cows

Mid-lactation Holstein cows (n = 4) were used to evaluate the effects of complete feed deprivation on circulating insulin-like growth factors (IGF) and their binding proteins (IGFBP). Comparisons were made between cows in fed and unfed conditions and included response to a single injection of bovine somatotropin (bST). Two days of feed deprivation decreased milk yield 66%. Concentrations of bST nearly doubled during feed deprivation, whereas glucose and insulin steadily decreased. Circulating concentrations of IGF-I decreased nearly 50%, IGF-II decreased 28% and IGFBP-2 increased 49% during the 2 d of feed deprivation. In contrast, IGFBP-3 was not affected. Eighteen to 24 h after the bST challenge, circulating concentrations of IGF-I rose 100% during the fed period, but there was no response during the unfed period. Blood concentrations of IGF-II decreased 17% after bST challenge in the fed period but were unchanged in the unfed period. More moderate undernutrition (80% of requirements) did not affect circulating IGFBP-2 but did alter the response of IGFBP-2 to bST. A conceptual model was developed that illustrates that nutritional regulation of the ST/IGF system represents a key component signaling the appropriate use of nutrients. Overall, results demonstrate that nutritional modulation of the ST/IGF system plays a key role in animal performance and well-being over a wide range of physiological situations.

Control of ovarian follicular and corpus luteum development for the synchronization of ovulation in cattle

The objective of this review is to integrate strategies to optimize an ovulatory control program which then serves as a platform to improve the reproductive performance of lactating dairy cows. Programmed management of follicle growth, regression of the CL and induction of ovulation led to development of the Ovsynch program. Pre-synchronization of estrous cycles followed 12 to 14 days later with the Ovsynch program increased pregnancy rates to timed inseminations. Initiation of the Ovsynch program on day 3 of the estrous cycle reduced ovulation to GnRH and resulted in a smaller proportion of excellent and good quality embryos following timed insemination. The pregnancy rate to a timed insemination of Ovsynch was greater when cows ovulated to the first injection of GnRH. The Presynch-Ovsynch program provided a platform to identify factors regulating reproductive performance; such as, parity, body condition score and anovulation. Treatment with hCG at day 5 after insemination increased pregnancy rate in lactating dairy cows. Injection of bovine somatotropin at insemination increased pregnancy rate, conceptus length and interferon-τ content in uterine luminal flushings and altered endometrial gene expression at day 17 of pregnancy. During heat stress, timed embryo transfer increased pregnancy rate and using embryos cultured with IGF-I and transferred fresh resulted in a greater pregnancy rate. Induction of ovulation with estradiol cypionate, as a component of a timed insemination program, increased fertility. Manipulation of the estrous cycle to improve follicle/oocyte competence and management of the post-ovulatory dialogue between embryonic and uterine tissues should enhance embryo development and survival.

Pre- and post-weaning injections of bovine somatotropin to optimize puberty achievement of Bos indicus beef heifers.

The present study evaluated the growth and puberty attainment of Bos indicus heifers administered recombinant bovine somatotropin (bST) or saline injections during preweaning and/or postweaning. On day 0, 177 suckling Nellore heifers were stratified by initial age and body weight (BW) (80 ± 10 d; 97 ± 16 kg), and randomly assigned, in a 2 × 2 factorial design (n = 44 to 45 heifers/treatment), to receive s.c. injections of saline (5 mL 0.9% NaCl) or sometribove zinc (Posilac; Elanco, Greenfield, IN; 6.14 mg/kg of BW0.75) on days 0 and 10 (PRE) and/or days 167 and 177 (POS). All heifers were managed as a single group in Brachiaria decumbens pastures from day 0 until 24 d postweaning (day 191), and then provided a corn silage–based TMR from days 191 to 380 to achieve 65% to 70% of mature BW at the end of the study (day 380). Heifer full BW was collected on days 0, 10, 167, 177, and monthly from days 191 to 380. Transrectal ultrasonography of ovaries was performed on days 1 and 10 of each month from days 229 to 380 to assess the percentage of pubertal heifers. Liver biopsies and blood samples from jugular vein were collected on days 0, 10, 167, 177, and 380. Additional blood samples were collected monthly from days 259 to 380 (n = 10 to 15 heifers/treatment). No interactions among day of the study, PRE, and POS injections of saline or bST were detected (P ≥ 0.11). Preweaning bST injections increased heifer average daily gain (ADG) from days 0 to 10 and plasma IGF-1 on day 10 (P ≤ 0.03), did not affect ADG from days 0 to 177, plasma IGF-1 from days 259 to 380, and any liver gene mRNA expression (P ≥ 0.19), but tended to decrease ADG from days 191 to 380 (P = 0.07) and percentage of pubertal heifers on days 349 (P = 0.07), 359 (P = 0.002), and 380 (P = 0.0001) compared with saline injections. Postweaning bST injections increased plasma IGF-1 on day 177 and overall liver mRNA expression of GHR-1A (P ≤ 0.05), decreased plasma IGF-1 from days 259 to 380 (P = 0.03), tended to decrease liver mRNA expression of GHR-1B on day 177 (P = 0.08), but did not affect ADG from days 167 to 177 and 191 to 380, and puberty attainment from days 229 to 380 (P ≥ 0.12) compared with saline injections. Thus, preweaning and postweaning injections of bST successfully increased heifer plasma IGF-1 concentrations 10 d after first injection. Postweaning injections of bST had no impact on puberty attainment, whereas preweaning bST injections of bST impaired puberty attainment of Nellore beef heifers.

29 Pre- and Post-Weaning Injections of Bovine Somatotropin to Optimize Puberty Achievement of Purebred Bos Indicus Beef Heifers.

29 Pre- and Post-Weaning Injections of Bovine Somatotropin to Optimize Puberty Achievement of Purebred Bos Indicus Beef Heifers.

Effect of bovine somatotropin injection in late pregnant Holstein heifers on metabolic parameters and steroidogenic potential of the first postpartum dominant follicle

The aim of this study was to determine the effect of pre-partum injections of bovine somatotropin (bST) in dairy heifers on metabolic markers and the steroidogenic potential of the first postpartum dominant follicle. Heifers were assigned to two groups: bST (ST; n = 29), that received two doses of bST (500 mg/dose) at −28 and −14 days relative to calving; and control (CTL; n = 30), that did not received bST. Follicular development was monitored via ultrasound every 3 days starting at 8 days in milk (DIM) in a subset of 20 heifers until the day the first large follicle reached a diameter of 16 mm. From these cows follicular fluid was aspirated and the follicular cells recovered (ST; n = 8 and CTL; n = 10). Blood samples were collected weekly for all heifers. Follicular fluid IGF-I concentrations of the first postpartum dominant follicle was higher (P = 0.05) in ST (87.1 ± 7.7 mg/mL) than CTL cows (64.3 ± 6.8 mg/mL). Also, E2 concentration in the follicular fluid was higher (P = 0.02) for ST (199.7 ± 55.9 ng/mL) than CTL cows (74.5 ± 37.7 ng/mL). The expression of LHCGR and STAR mRNA in follicular cells was higher (P < 0.05) in ST than CTL cows. Nonetheless, HSD3B, P450scc, P450c17, IGFr and CYP19A1 mRNA expression was not different between groups (P > 0.05). Serum IGF-I concentration was higher in ST treated heifers during the pre-partum period (P = 0.01) and no difference was observed in the postpartum period (P = 0.19). In conclusion, pre-partum bST treatment in dairy heifers increased intrafollicular IGF-I and expression of LHCGR and STAR mRNA in follicular cells of the first postpartum dominant follicle. These changes were associated to increased intrafollicular and serum E2 concentration, which can potentially increase the chance of ovulation of the first follicular wave.

501 Pre-weaning injections of bovine somatotropin altered liver gene expression, and enhanced puberty attainment and calving rates of Bos indicus-influenced beef heifers

A 3-yr study evaluated the effects of three 14-d apart injections of bovine somatotropin (bST) to suckling beef heifers on pre-weaning (yr 1, 2 and 3) and post-weaning growth and reproductive performance (yr 1 and 2 only). On d 0 of each yr, Angus × Brangus heifers (n = 15 heifers/treatment/yr; BW = 147 ± 20 kg; Age = 134 ± 11 d) were stratified by BW and age, and randomly assigned to receive s.c. injections of saline (SAL; 5 mL; 0.9% saline) or bST (250 mg of sometribove zinc; Posilac, Elanco, Greenfield, IN) on d 0, 14 and 28. Cow-calf pairs were allocated to 4 bahiagrass (Paspalum notatum) pastures (7-8 pairs/pasture/yr) from d 0 until weaning (d 127). Unshrunk BW and blood samples were collected on d 0, 14, 28 and 127. From d 127 to 346, heifers were pooled by treatment and allocated to bahiagrass pastures (1 pasture/treatment/yr) and fed soybean hulls-based concentrate at 1.1% BW (DM basis). Liver samples were collected via needle biopsy on d 0, 42, and at start of breeding season (d 262) of yr 3 only (6 heifers/treatment). Blood samples were collected every 9 to 10 d from d 127 to 346. Heifers were considered pubertal when 2 consecutive plasma samples had P4 ≥ 1.5 ng/mL. Resulting interactions among treatment, yr, and day were not detected for any variable measured in the study (P ≥ 0.12). During pre-weaning phase, bST heifers had greater ADG from d 0 to 42 (1.15 vs. 1.07 ± 0.026 kg/d; P = 0.03), but similar BW at weaning compared to SAL heifers (261 vs. 259 ± 1.3 kg, respectively; P = 0.25). Liver mRNA expression of GHR-1B and IGF-1 did not differ on d 0 and 42 (P ≥ 0.15), but was greater for bST vs. SAL heifers on d 262 (P ≤ 0.02). During post-weaning phase (d 127 to 347), bST heifers had similar ADG (0.17 vs. 0.12 ± 0.07 kg/d; P = 0.11), a greater (P ≤ 0.02) percentage of heifers attaining puberty at initiation of the breeding season (53 vs. 27 ± 7.9%), pregnancy (93 vs. 70 ± 6.6%) and calving rates (90 vs. 53 ± 7.3%) compared to SAL heifers. Calving distribution did not differ between treatments (P ≥ 0.15). Therefore, three 250 mg injections of bST administered at 14-d intervals, between 135 and 163 d of age, enhanced reproductive performance of Bos indicus-influenced beef heifers.

023 Pre-Weaning Injections of Bovine Somatotropin Enhanced Puberty Attainment of Bos Indicus-Influenced Beef Heifers

A 3-yr study evaluated the effects of three 14-d apart injections of bovine somatotropin (bST) to suckling beef heifers on pre-weaning (yr 1, 2 and 3) and post-weaning (yr 1 and 2) growth and puberty achievement. On d 0 of each yr, Angus × Brangus heifers (n = 15 heifers/treatment/yr; BW = 147 ± 20 kg; Age = 134 ± 11 d) were stratified by BW and age, and randomly assigned to receive s.c. injections of saline (SAL; 5 mL; 0.9% saline) or half-dose of bST (250 mg of sometribove zinc; Posilac, Elanco, Greenfield, IN) on d 0, 14 and 28. Cow-calf pairs were allocated to 4 bahiagrass (Paspalum notatum) pastures (7 to 8 pairs/pasture/yr) from d 0 until weaning (d 127). Unshrunk BW and blood samples were collected on d 0, 14, 28 and 127. From d 127 to 346, heifers were pooled by treatment and allocated to bahiagrass pastures (1 pasture/treatment/yr) and fed blackstrap molasses-based concentrate at 1.1% BW (DM basis). Post-weaning blood samples were collected every 9-10 d to determine plasma progesterone (P4) concentrations. Heifers were considered pubertal when 2 consecutive plasma samples had P4 ≥ 1.5 ng/mL. Effects of treatment × yr and treatment × yr × time were not detected for any variable measured in the study (P ≥ 0.69). During pre-weaning phase, bST heifers had greater pre-weaning mean plasma IGF-1 concentrations (115 vs. 102 ± 3.8 ng/mL; P = 0.02; yr 1 and 2 only) and ADG from d 0 to 42 (1.15 vs. 1.07 ± 0.026 kg/d; P = 0.03), but had less ADG from d 42 to 127 than SAL heifers (0.74 vs. 0.80 ± 0.022 kg/d; P = 0.04). Hence, BW at weaning did not differ between bST and SAL heifers (261 vs. 259 ± 1.3 kg, respectively). During post-weaning phase, bST heifers had similar ADG from d 127 to 347 (0.17 vs. 0.12 ± 0.07 kg/d; P = 0.11), and BW and age at puberty (290 vs. 291 ± 6.9 kg and 395 vs. 419 ± 14 d, respectively; P ≥ 0.15), but greater puberty achievement at start of breeding season (63 vs. 44 ± 7.9%) compared to SAL heifers. Hence, three half-dose injections of bST administered to suckling beef heifers at 14-d intervals, between 135 and 163 d of age, may be a feasible management practice to enhance puberty attainment at the start of the breeding season.

1274 Pre-weaning injections of bovine somatotropin enhanced puberty attainment of bos indicus-influenced beef heifers

1274 Pre-weaning injections of bovine somatotropin enhanced puberty attainment of bos indicus-influenced beef heifers

Effects of bovine somatotropin injection on serum concentrations of progesterone in non-lactating dairy cows

The objective of this experiment was to evaluate the effects of bovine somatotropin administration on serum concentrations of glucose, insulin, NEFA, IGF-I, and progesterone (P4) in ovariectomized non-lactating dairy cows receiving exogenous P4, as a model to estimate treatment effects on hepatic P4 degradation. Ten non-lactating, non-pregnant, and ovariectomized Gir×Holstein cows were assigned to the experiment (d −14 to 27). On d 0, cows were ranked by BW and BCS, and randomly assigned to one of two treatments: (1) bovine somatotropin (BST; n=5) or (2) saline control (control; n=5). Cows assigned to the BST treatment were administered s.c. injections containing 500mg of sometribove zinc on d 0, 9, and 18 of the experiment, whereas control cows concurrently received a 10-mL s.c. injection of 0.9% saline. On d −2, cows were inserted with an intravaginal releasing device containing 1.9g of P4, which remained in the cows until the end the experiment (d 27). Cow BW and BCS were assessed on d −14, 0, and 27. Blood samples were collected daily from d 0 to d 27, at 0 (immediately before), 1, and 2h relative to concentrate feeding for determination of serum glucose, insulin, NEFA, P4, and IGF-I concentrations. Concentrations of glucose, NEFA, and insulin obtained prior to feeding (0h) were used to determine pre-prandial revised quantitative insulin sensitivity check index (RQUICKI). No treatment effects were detected for BW (P=0.72) and BCS change (P=0.79) during the experiment. Beginning on d 2 of the experiment, BST cows had greater (P≤0.01) serum IGF-I concentrations compared with control cohorts (treatment×day interaction; P<0.01). Cows receiving BST had greater (P≤0.05) insulin concentrations compared with control cohorts from d 8 to d 11, d 16 and 17, as well as from d 19 to d 21 of the experiment (treatment×day interaction; P<0.01). Cows receiving BST had greater (P≤0.01) mean glucose and NEFA concentrations, as well as reduced (P<0.01) mean RQUICKI during the experiment compared with control cohorts. No treatment effects, however, were detected (P=0.73) for serum P4 concentrations. In conclusion, results from this experiment indicate that hepatic P4 catabolism is not directly regulated by circulating IGF-I, whereas BST administration decreases insulin sensitivity in non-lactating dairy cows in adequate nutritional status.

Kajian Fisiologis Penggunaan Bovine Somatotropin (bST) Pada Sapi Pra Afkir

Studies of physiological bovine somatotropin (bST) on post lactating dairy ABSTRACT. To increase of milk production nationally with used in dairy cattle business can assist to increase milk production, eighteen post lactating dairy cows in the highland Cipelang Bogor, were used to study the effect used of bovine somatotropin and lactating time. The experimental cows were assigned into a Randomized Block Design with a 3x2 factorial arrangement. The first factor was using of somatotropin (bST)with three levels (non bST injection, biweekly injection and three weekly injection). The second factor was lactating time with two levels (4th lactating time and 6 th lactating time) Parameters measured were heart rate, respiration frequency, rectal temperature, milk production efficiency, milk production, 4% FCM (fat corrected milk.), Milk composition, weigh gain, milk quality consist of protein, fat, pH. Bovine somatotropin significantly increased heart rate and respiration rate. Also bovine somatotropin injection at 4th lactating time significantly increased milk production. There were an interaction between bST dan lactating time on milk production and weight gain. Bovine somatotropin injection biweekly in cows on 4th lactating time ration increased milk production by 16-26 %, but injection in cows 6th lactating time increased milk production by 8-18 % combination with somatotropin doze 250/ml/14 days. Somatothropine supplementation was injection biweekly and three weekly did significantly affect to milk production, body temperature, heart rate, and respiration rate however in normal physiology . Bovine somatotropine can increase post lactating dairy production interval 14 days better than 21 days.

Control of ovarian follicular and corpus luteum development for the synchronization of ovulation in cattle

The objective of this review is to integrate strategies to optimize an ovulatory control program which then serves as a platform to improve the reproductive performance of lactating dairy cows. Programmed management of follicle growth, regression of the CL and induction of ovulation led to development of the Ovsynch program. Pre-synchronization of estrous cycles followed 12 to 14 days later with the Ovsynch program increased pregnancy rates to timed inseminations. Initiation of the Ovsynch program on day 3 of the estrous cycle reduced ovulation to GnRH and resulted in a smaller proportion of excellent and good quality embryos following timed insemination. The pregnancy rate to a timed insemination of Ovsynch was greater when cows ovulated to the first injection of GnRH. The Presynch-Ovsynch program provided a platform to identify factors regulating reproductive performance; such as, parity, body condition score and anovulation. Treatment with hCG at day 5 after insemination increased pregnancy rate in lactating dairy cows. Injection of bovine somatotropin at insemination increased pregnancy rate, conceptus length and interferon-tau content in uterine luminal flushings and altered endometrial gene expression at day 17 of pregnancy. During heat stress, timed embryo transfer increased pregnancy rate and using embryos cultured with IGF-I and transferred fresh resulted in a greater pregnancy rate. Induction of ovulation with estradiol cypionate, as a component of a timed insemination program, increased fertility. Manipulation of the estrous cycle to improve follicle/oocyte competence and management of the post-ovulatory dialogue between embryonic and uterine tissues should enhance embryo development and survival.

Characterization of Early Embryonic Death and Prevention of Pregnancy Wastage

Reproductive management programs will be discussed that attempt to optimize these critical windows in a manner that increases pregnancy rates. With our understanding of the dialogue between the developing embryo and the maternal reproductive tract, pharmaceutical and nutritional strategies also have increased pregnancy rates. For example, injection of bovine somatotropin at the time of insemination increases pregnancy rates in lactating dairy cows. The lactational state in modern day dairy cows contributes to a sub-fertile condition that the practitioner needs to manage based upon a thorough understanding of the underlying physiological causes. These limitations are partially amenable to improvement as part of a production medicine program.

Effects of Diet and Injection of Bovine Somatotropin on Prepubertal Growth and First-Lactation Milk Yields of Holstein Cows

To determine effects of rapid prepubertal growth on first-lactation milk production, Holstein heifers were randomly assigned to one of three treatments. Thirty-five heifers were fed a standard diet to meet NRC recommendations and produce 0.8kg of body weight (BW) gain/d (standard). Thirty-five heifers were fed a diet with higher energy (2.8 Mcal of metabolizable energy/kg) and protein (19.7% crude protein; high diet) to produce 1.2kg of BW gain/d (high). Thirty-five heifers were fed the high diet and injected daily with bovine somatotropin (bST) (25µg/kg of BW; high-bST). Diets were fed and bST was injected from 135kg of BW until pregnancy was confirmed. Heifers were inseminated after BW exceeded 363kg. Pregnant heifers were commingled and fed similar diets through gestation, parturition, and lactation. High and high-bST heifers had greater prebreeding average BW gains than standard heifers. Conversely, standard heifers had a greater average BW gain during gestation than high and high-bST heifers. High and high-bST heifers were approximately 90 d younger than standard heifers at first insemination and first parturition. Postpartum BW, body condition scores, and withers heights at parturition, and calving ease scores were not different among treatments. Standard heifers produced 14% more milk than high heifers but not more than high-bST heifers. The high-protein, high-energy diet decreased age at first parturition and first-lactation milk production, but did not affect reproduction. Injection of bST during the pre-pubertal growth period combined with the high diet decreased age at first parturition without reducing milk production.

Regulation of yield loss and milk composition during once-daily milking: a review

Once-daily milking (ODM) of ruminants results in loss of milk production. In cows this loss is very variable between individuals but in recent short-term trials, on average, the loss was 13%. Full lactation studies indicate losses of 35–50% but documentation from some commercial farms using ODM suggests that losses are lower. ODM also results in changes in mammary permeability leading to changes in milk composition through increased influx of serum proteins and ions and increased efflux of lactose and potassium. Somatic cell count is also increased by ODM. Yield loss occurs through a combination of acute and chronic changes in mammary function. Anatomical and physiological characteristics which are likely to minimise production losses on ODM include production of a concentrated milk, possession of a large cistern, good drainage from the alveolar compartment and a low initial somatic cell count. Efficient removal of strippings, use of oxytocin and/or injection of bovine somatotropin all act to restore yield during ODM. It is proposed that the mechanism of the yield loss is through changes in mammary function initiated by changes in cell shape during alveolar filling. Central to these changes is an increased permeability of the udder through impairment of tight junctions between the alveolar cells. This effect appears to be linked to a mild inflammatory response which occurs in the last 12 h of a 24-h period of milk accumulation. The ability to further reduce production losses on ODM could lead to much wider adoption of ODM. Key to this is the development of methods to identify high-producing animals tolerant of extended milking intervals.

The Effect of Recombinant Bovine Placental Lactogen on Induced Lactation in Dairy Heifers

The primary objective of this study was to determine whether bovine placental lactogen stimulated additional mammary growth as assessed by milk yield from a lactation induced by steroids. Pubertal, nonpregnant Holstein heifers (n=23) were given daily subcutaneous injections of estradiol-17β (0.05mg/kg) and progesterone (0.25mg/kg) for 7 d to initiate mammary growth. Prolactin secretion was suppressed in all heifers via bromocriptine, which was administered until d 15. Heifers were treated with either placental lactogen (40mg/d; n=12) or water (control group; n=11) for 18 d. Lactation was induced by daily injection of dexamethasone for 3 d and twice daily injections of recombinant bovine prolactin for 5 d starting on d 18. From 3 to 8 wk of lactation, milk yield of heifers treated with placental lactogen was numerically higher (22%) than the yield of control heifers, but the difference was not significant because of the high coefficient of variation. Daily injection of bovine somatotropin (d 57 to 66 of lactation) increased milk yield of both groups and stimulated a greater numerical increase in milk yield for heifers that were treated with placental lactogen. These results support the hypothesis that bovine placental lactogen is mammogenic and is one of the factors that regulates mammary growth during pregnancy.

Somatotropin Treatment Does Not Affect Nonesterified Fatty Acid Response to Adrenergic Injections in Underfed or Overfed Nonlactating Cows

This experiment was conducted to determine the respective effects of bovine somatotropin (bST) and energy balance on the in vivo responses on plasma nonesterified fatty acids and glucose to isoproterenol (a nonselective β-agonist) or epinephrine injection in nonlactating nonpregnant cows. Two groups of adult Holstein cows were either underfed (n = 4) at 75%, or overfed (n = 5) at 150% of maintenance energy requirement, respectively. Cows received or did not receive a subcutaneous injection of Sometribove (500 mg) during two experimental periods (cross-over design). Adrenergic or placebo injections (4 nmol/kg body weight of epinephrine or isoproterenol or 4 mL of sterile saline) were administered intravenously on d 7–9 after bovine somatotropin injection, 1 h before or 3.5 h after feeding for under- or overfed cows, respectively. Glucose and nonesterified fatty acid responses to each challenge were calculated as area under the response curve and above the base line, from the time of challenge until 60 min postchallenge. Basal plasma nonesterified fatty acids and their response to adrenergic injections were enhanced by underfeeding. Responses of nonesterified fatty acids to isoproterenol injection were higher than they were to epinephrine injection. Basal plasma glucose was enhanced by bovine somatotropin treatment, which increased the glucose response at 5 min after adrenergic injections. Response of plasma glucose was higher after epinephrine than after isoproterenol injection. Treatment with bovine somatotropin did not change plasma nonesterified fatty acid responses to epinephrine or isoproterenol injection in under- or overfed cows, at constant energy intake, whereas underfeeding modified these responses markedly.

A note on the effect of use of bovine somatotropin on the fatty acid composition of the milk fat in dairy cows

Commencing on day 100 ± 10 of lactation, 10 Italian Friesian cows averaging 32·6 kg milk per day were injected biweekly with recombinant bovine somatotropin (BST), while 10 other cows averaging 33-4 kg milk per day were injected with a placebo. Cows were offered ad libitum a total mixed diet throughout the lactation. The experiment lasted 16 weeks; milk samples were taken before and 16, 62 and 91 days after the commencement of BST injection. The objective was to determine the impact of biweekly injections of BST on the synthesis and proportion of milk fatty acids, particularly on cis and trans isomers and on fatty acids with an odd number of carbon atoms (C15 and C17). A decrease in the proportion of shortchain (C4 to C14) fatty acids (P &lt; 0·001) and an increase in the proportion of long-chain (C16 to C20) fatty acids (P &lt; 0·001) were observed in the first period of the treatment. With regard to cis and trans isomers, a considerable increase of the cis isomers (P &lt; 0·001), particularly C18.1cis9 (oleic acid) was observed, while differences in trans isomers were not statistically significant. Concentrations of C15 (pentadecanoic acid) were not affected but heptadecanoic acid (C17) concentration showed a considerable increase (P &lt; 0·01) but only in the sample taken after 16 days.

Effect of Recombinant Bovine Somatotropin on the Superovulatory Response to Pregnant Mare Serum Gonadotropin in Heifers

Treatment of mature heifers with recombinant bovine somatotropin (BST) increases the number of ovarian follicles of 2-5 mm in diameter. This study was carried out to investigate whether the increase in the number of small follicles induced by BST treatment can enhance the superovulatory response. In the first experiment, 24 heifers were assigned, in a randomized block design, to four treatment groups: 1) control; 2) BST; 3) pregnant mare serum gonadotropin (PMSG); 4) BST+PMSG. On Day 7 of the estrous cycle, animals in groups 2 and 4 received injections of 320 mg BST (in a sustained release formulation), while heifers in groups 1 and 3 received 10 ml saline. Five days later heifers in groups 3 and 4 were treated with a single dose of 2000 IU PMSG to induce superovulation. Embryos were recovered nonsurgically on Days 6-8 of the following cycle, and all heifers underwent laparoscopy on Day 9 to assess ovulation rate. In a second experiment, 24 heifers were assigned randomly to four treatment groups: 1) PMSG (1000 IU); 2) BST (320 mg) + PMSG (1000 IU); 3) PMSG (2000 IU); 4) BST (320 mg) + PMSG (2000 IU), and then treated as for experiment I. In both experiments, all heifers were scanned daily using real-time ultrasound from the day before BST injection until the day of ovulation to monitor dynamics of ovarian follicular growth and development, and blood samples were collected daily throughout the experimental period for measurement of peripheral progesterone, estradiol-17 beta, growth hormone (GH), and insulin-like growth factor-I (IGF-I).(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of bovine somatotropin injections on mammary blood flow in dry and lactating dairy cows

The effects of bovine somatotropin injections on mammary blood flow in dry and lactating dairy cows

The effects of bovine somatotropin injections on mammary blood flow in dry and lactating dairy cows

The effects of bovine somatotropin injections on mammary blood flow in dry and lactating dairy cows