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1.
The objectives of this study were to determine the effects of daily injection of bovine somatotropin (bST) on the metabolism of N and 1-[14C]leucine and on hormone and metabolite concentrations in growing beef steers. Injection of bST increased N retention (P less than .05) primarily through decreased (P less than .10) urinary N excretion. Plasma concentration of somatotropin, insulin and glucose increased (P less than .01) and of urea-N (P less than .01) and alpha-amino-N (P less than .10) decreased with bST compared with excipient injection. Total leucine flux was not altered by treatment; however, the partition of flux was. Leucine oxidation decreased (P less than .05) and leucine used for protein synthesis (P less than .10) increased, with bST compared with excipient injection. During excipient injection, 10.3 g protein were synthesized for each gram crude protein deposited, whereas during bST injections only 6.4 g were required. The average maximum contribution of myofibrillar protein degradation to whole body protein degradation, calculated from excretion of 3-methylhistidine, was 16%. Although the ratio of protein deposition/protein synthesis was low for both excipient- and bST-injected steers, the incremental efficiency of protein deposition was 50%, reflecting a dilution of protein synthesis required for turnover and a proportionately greater increase in protein synthesis than protein degradation with bST injection. In growing beef steers, bST stimulated whole body protein synthesis and decreased leucine oxidation. The change in partition of leucine flux, but not of total flux (irreversible loss), demonstrates a chronic redirection in metabolism consistent with homeorhetic control. These data from steers injected with bST suggest mechanisms by which bST affects metabolism during normal growth. 相似文献
2.
Milk production is increased in lactating cows treated with bovine somatotropin (bST) because a greater portion of absorbed nutrients are partitioned for milk synthesis. This homeorhetic action may be caused by alterations in response of key tissues to homeostatic signals. To examine this theory, acute metabolic challenges were administered to 8 multiparous Holstein cows (61 +/- 2 days postpartum) receiving daily subcutaneous injections of pituitary-derived bST (26.3 mg) or excipient during two 14-day treatment periods (crossover experimental design). Treatment with bST increased milk yield 12%. Feed intake did not change so that net energy balance decreased (+ .5 vs. -4.3 Mcal/day). Plasma concentrations of nonesterified fatty acids (NEFA) were chronically elevated in bST-treated cows, consistent with energy balance differences. However, baseline concentrations of glucose, insulin, and glucagon in plasma did not differ. On the last 3 days of treatment, individual metabolic challenges were administered via jugular cannulas: epinephrine (700 ng/kg BW), glucose (250 mg/kg BW), insulin (1.0 micrograms/kg BW), and glucagon (175 ng/kg BW). Plasma glucose was reduced after the insulin challenge to a lesser extent during bST treatment. In bST-treated cows, the increase in plasma NEFA in response to epinephrine was greater, and NEFA concentrations were lowered to a greater extent after insulin and glucose challenges. Glucose, insulin, and glucagon removal rates were not altered, nor was plasma glucose response to epinephrine or glucagon challenges. Treatment of lactating cows with bST primarily altered the response of adipose tissue to homeostatic signals which affect lipid metabolism. 相似文献
3.
Metabolic responses to exogenous bovine somatotropin in Friesian cows of low or high genetic merit 总被引：1，自引：0，他引：1
A Michel S N McCutcheon D D Mackenzie R M Tait B W Wickham 《Domestic animal endocrinology》1991,8(2):293-306
Basal hormone/metabolite concentrations and responses to intravenous challenges of glucose, insulin and epinephrine were examined in Friesian cows from selection lines of low or high genetic merit treated with recombinantly-derived bovine somatotropin (bST) or control formulation in a 2 x 2 factorial design. Cows from the low genetic merit (low breeding index, LBI) line had previously been shown to be more responsive to the galactopoietic effects of bST (50 mg/day) than those from the high breeding index (HBI) line. Despite this, comparisons of metabolic differences were not confounded by differences in energy balance because bST treatment had also caused an increase in voluntary intake of cut pasture. Circulating levels of somatotropin, insulin-like growth factor-I (IGF-I) and insulin were greater in bST-treated than control cows but neither bST treatment nor selection line influenced basal concentrations of glucose, non-esterified fatty acids (NEFA), beta-hydroxybutyrate, urea or creatinine. Treatment with bST produced a small increase in sensitivity of cows to the lipolytic effects of epinephrine and this effect was similar in both selection lines. HBI cows had greater circulating insulin levels following the glucose challenge than LBI cows but bST treatment did not affect the insulin response to exogenous glucose. Whereas bST treatment retarded the glycogenolytic response to epinephrine and the clearance of blood glucose in response to insulin in LBI cows, it had no effect on epinephrine-stimulated glycogenolysis, and caused enhanced glucose clearance in response to insulin, in HBI cows. Results are consistent with bST altering the homeorhetic control of metabolism but do not adequately explain the greater responsiveness of LBI cows to the galactopoietic effects of bST. 相似文献
4.
D Schams F Graf J Meyer B Graule M Mauthner C Wollny 《Journal of animal science》1991,69(4):1583-1592
Twelve second-lactation Deutsches Fleckvieh cows, (FV, a dual-purpose breed) and 12 German Black and White (BW, a dairy breed) were used to evaluate similarities and differences in the response to a prolonged-release formulation of sometribove (N-methionyl bovine somatotropin, bST). Cows were milked twice daily and fed a basic diet (70% corn silage, 30% alfalfa hay) ad libitum plus 1 kg of concentrate. Additionally, concentrates and supplements were offered at the rate of 1 kg for each 22 kg of milk produced above 12 kg/d. Six cows of each breed were treated s.c. with 500 mg of sometribove at 14-d intervals from wk 9 to 29 postpartum (pp). Blood was collected by jugular vein puncture once weekly from wk 7 to 33 pp and daily for 14 d after the first and last (11th) injection of bST. Somatotropin (ST), insulin-like growth factor I (IGF-I), insulin, thyroid hormones, nonesterified fatty acids (NEFA), liver enzymes, and blood metabolites were evaluated. During bST treatment, plasma ST increased significantly on d 7 in both breeds and then decreased on d 14 after injection. Plasma IGF-I was positively correlated with ST. Plasma NEFA were high on d 7 and decreased on d 14. In response to bST, the average milk yield increased for FV and BW cows by 5.1 kg/d (29.7%) and 5.0 kg/d (28%), respectively, and 4% fat-corrected milk (FCM) increased by 5.0 kg/d (28%) and 5.3 kg/d (19.9%), respectively. Milk content of fat, protein, lactose, number of somatic cells, and body weight were similar across treatments.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
5.
《Domestic animal endocrinology》1994,11(2):209-216
Effects of daily injectable or sustained-release bovine somatotropin (bST) administrations on plasma and milk bST and insulin-like growth factor-I (IGF-I) concentrations were monitored in 74 lactating cows through early, mid- and late lactation. Treatments beginning at wk 4 of lactation were excipient (CO, 24 cows) at 2 wk intervals, daily injections of 10.3 mg bST (DI, 25 cows) and 350 mg sustained-release bST at 2 wk intervals (SR, 25 cows). The duration of treatments was 40 wk. Data were first analyzed for the overall mean concentrations covering the 40 wk treatment period. Overall mean plasma bST, milk bST and plasma IGF-I concentrations were significantly increased by both bST treatments (p<0.05). On the other hand, milk IGF-I concentrations were significantly increased (p<0.05) only in the DI group. Next, data were analyzed according to stage of lactation. The bST treatments resulted in significant increases (p<0.05) in plasma and milk bST concentrations for all early, mid- and late lactation periods. Even though plasma IGF-I concentrations were higher (p<0.05) in all lactation periods for bST treatment groups, higher milk IGF-I concentrations (p<0.05) occurred only in mid- and late lactation periods for the DI group. The patterns of bST and IGF-I concentrations in milk follows those of the plasma after bST treatments. 相似文献
6.
类胰岛素生长因子及其营养调控 总被引：8，自引：0，他引：8
动物肝脏分泌及肝外组织合成的类胰岛素生长因子 (IGF)是动物生长发育的重要调节因子 ,也是生长激素和营养物质发挥促生长作用的主要介导因子。IGF本身的合成与分泌不但受生长激素的影响 ,也受营养状况的调节。本文在介绍IGF的研究历史和生化特性基础上 ,综述了IGF在机体物质代谢和细胞生长中的调节作用以及激素和营养状况对IGF合成与分泌的影响 ,为进一步研究IGF与营养的关系提供参考 相似文献
7.
8.
The effect of exogenous bovine somatotropin (bST) treatment on the temporal pattern of insulin-like growth factor-I (IGF-I) in serum of four multiparous Holstein cows was examined. Cows (190 +/- 24 days postpartum) were treated with daily subcutaneous injections of recombinant bST (40 mg) or excipient for 12-day periods in a crossover experimental design. During excipient treatment, concentrations of IGF-I in serum were relatively constant throughout the day and averaged 70 ng/ml. Following the first bST injection, serum IGF-I began increasing after a lag of 5 to 7 hr and progressively increased over the first 2 days of treatment. Serum IGF-I levels were approximately 2-fold greater than control values at the end of day 1 of bST treatment, with a 3-fold elevation observed at the end of day 2. Concentrations of IGF-I in serum plateaued by day 3 of bST treatment. Serum concentrations of IGF-I did not follow the oscillating pattern of bST in serum resulting from daily bST injections. Milk yield (3.5% fat-corrected) plateaued after 6 days of bST treatment and was increased 61% (+15.3 kg). Both IGF-I and milk yield remained essentially constant across days for the remainder of treatment. Following cessation of treatment, serum IGF-I and milk yield gradually declined, returning to control values after approximately 4 days. The temporal pattern of circulating concentrations of IGF-I is consistent with a role for IGF-I in mediating a portion of the effects of exogenous bST in lactating cows. 相似文献
9.
B A Crooker D E Otterby 《Veterinary Clinics of North America: Food Animal Practice》1991,7(2):417-437
Cows that produce large quantities of milk require more management and higher quality of management than cows producing smaller quantities of milk. This is true whether improvements in milk production occur through genetic selection, increased milking frequency, or use of bovine somatotropin (bST). The milk response to use of bST is similar (10 to 15%) to that of three times a day (3x) milking and we expect that the management required to maintain the increased production through successive lactations with bST will be similar to that required for the 3x herd. Maximum economic benefit from use of bST will be achieved by dairy managers who (1) feed cows to maximize intake of diets with appropriate nutrient content and balance, (2) maintain proper body condition of their cows, and (3) have health and reproduction management programs that prevent rather than cure problems. Efficient use of record-keeping systems that enable the manager to monitor individual cow status will be advantageous. Economic forces will continue to bring change to the dairy industry. The manager that plans for change and ensures that the dairy's management programs allow for the most economically efficient production will be in position to adapt to these changes. The well-managed dairy will be able to adopt new, efficiency-enhancing technologies, such as bST, to ensure the continued opportunity to compete in the dairy industry. 相似文献
10.
Heat stress compromises efficient animal production by marginalizing nutrition, management, and genetic selection efforts to maximize performance endpoints. Modifying farm infrastructure has yielded modest success in mitigating heat stress-related losses, yet poor production during the summer remains arguably the costliest issue facing livestock producers. Reduced output (e.g., milk yield and muscle growth) during heat stress was traditionally thought to result from decreased nutrient intake (i.e., a classic biological response shared by all animals during environmental-induced hyperthermia). Our recent observations have begun to challenge this belief and indicate heat-stressed animals employ novel homeorhetic strategies to direct metabolic and fuel selection priorities independently of nutrient intake or energy balance. Alterations in systemic physiology support a shift in carbohydrate metabolism, evident by increased basal and stimulated circulating insulin concentrations. Perhaps most intriguing given the energetic shortfall of the heat-stressed animal is the apparent lack of basal adipose tissue mobilization coupled with a reduced responsiveness to lipolytic stimuli. Thus, the heat stress response markedly alters postabsorptive carbohydrate, lipid, and protein metabolism independently of reduced feed intake through coordinated changes in fuel supply and utilization by multiple tissues. Interestingly, the systemic, cellular, and molecular changes appear conserved amongst different species and physiological states. Ultimately, these changes result in the reprioritization of fuel selection during heat stress, which appears to be primarily responsible for reduced ruminant animal productivity during the warm summer months. 相似文献
11.
12.
A B Slebodziński E Brzezińska-Slebodzińska E Styczyńska M Szejnoga 《Domestic animal endocrinology》1999,17(2-3):161-169
Thyroid hormones (TH) and somatotropin (ST) play critical role in lactation. One explanation of their multiple physiological actions is based on the functional interrelationships among ST, TH, and thyroxin deiodinase (5'D). This enzyme is present in the mammary tissue, milk cellular components, and whole milk and is responsible for intramammary production of triiodothyronine (T3). In rats in which the 5'D isozymes in the mammary gland and in the liver are similarly of type I (5'D-I), an enhancement of mammary 5'D-I causes a reduction of hepatic 5'D-I activities. This opposite rearrangement in the mammary and hepatic deiodinating activities is thought to be a factor of a homeorhetic response characterized by an increased and compartmentalized energy expenditure of the mammary gland. In the cow, the mammary 5'D is the type II (5'D-II) deiodinase. The 5'D-II, owing to its high catalytic efficiency, secures T3 production, making tissues relatively independent from the circulatory levels of TH and from variations in the hepatic 5'D-I activity. No significant alterations of 5'D-II isozymes were found during a low T3 syndrome. Location of tissue deiodinases in the cow, the 5'D-II in the mammary gland, and the 5'D-I in the liver make it so that T3 production in these two tissues can be dissociated in time to secure better local requirement for T3 supporting lactation. To date, attempts to evidence that the alterations in iodothyronines blood levels and in tissues' 5'Ds activity during lactation are due to ST action have not received clear experimental support in either cows or rats. 相似文献
13.
Apparent absorption and retention of Ca, P, Mg, K, Cu, Mn, Zn, and S were determined in Holstein heifers treated with recombinant bovine somatotropin (bST). Six heifers (initial BW averaged 104 kg) were assigned to various doses of bST in a 6 x 6 Latin square design with six consecutive 21-d periods. Treatments were daily i.m. injections of 0, 6.7, 33.3, 66.7, 100, or 200 micrograms of bST/kg of BW on d 8 to 21 of each period. All heifers were fed a hay-concentrate diet, and nutrient digestibilities and balances were determined on d 14 to 20 of each period. Mineral concentrations in feed, water, excreta, and blood plasma were determined with an inductively coupled argon plasma-emission spectrometer. Exogenous bST did not affect apparent absorption or retention of Ca, P, Mg, K, Cu, Mn, or Zn. Plasma CU concentration was greater (P less than .05) in heifers receiving bST (82 micrograms of Cu/dl) than in those receiving excipient (73 micrograms of Cu/dl); plasma concentrations of other elements were not affected by bST. Injection of bST did not affect S absorption, but urinary S excretion decreased (P less than .05) and S retention increased (P less than .05) as dose of bST increased. The amount of S retained (1.5 g/d) when the heifers received the largest dose of bST was approximately 50% greater than the amount retained when heifers received excipient. These results demonstrate that bST affects the postabsorptive metabolism of S. Generally, bST did not affect nutrient digestibilities. Effects of bST on dietary mineral requirements were not determined because of the relatively short (14 d) treatment periods. 相似文献
14.
Harrell RJ Thomas MJ Boyd RD Czerwinski SM Steele NC Bauman DE 《Journal of animal science》1999,77(11):2934-2941
The ontogeny of the somatotropin/insulin-like growth factor system was examined in well-fed pigs under basal conditions and during a short-term challenge of porcine ST (pST). The study was conducted with two replicates of eight castrate male pigs from 3.8 kg BW (10 d of age) to 92 kg BW (129 d of age). Pigs were reared individually with ad libitum access to milk replacer through 23 d of age. Thereafter, pigs were fed a corn, soybean meal, and dry skim milk diet formulated to exceed nutrient requirements by approximately 30%. Pigs were randomly assigned to receive daily i.m. injections of either 0 (buffer) or 120 microg/kg BW of pST for a duration of 4 d starting at 10, 19, 33, 43, 63, 83, and 125 d of age. Blood was collected via jugular venipuncture on d 0 and 4 of the challenge. Circulating levels of IGF-I were not dramatically affected by age, but levels of IGF-II were low from 10 to 19 d of age and then increased through later stages of growth. Circulating concentrations of IGF binding protein (BP)-3 increased with age (P < .05), but levels of IGFBP-2, a 30-kDa IGFBP, and IGFBP-4 were unchanged (P > .10). The pST challenge reduced plasma urea nitrogen at all ages, but the magnitude of the response was less in younger pigs compared with the maximum response in pigs greater than 30 kg BW (63 d of age). The IGF-I response to the pST challenge also increased from approximately 30% in young pigs to a threefold increase in older pigs. Regardless of age, concentrations of IGF-II were minimally affected by the pST challenge. Circulating levels of IGFBP-3 increased and IGFBP-2 levels decreased in response to the pST challenge, and the magnitude increased with age. The high nutritional status of pigs in the early phases of growth diminished the postnatal changes in IGF-I and IGFBP-2, but not IGF-II or IGFBP-3. Overall, data demonstrate a developmental regulation of the ST/IGF system, with pST challenges altering circulating concentrations of IGF-I, IGFBP-3, and IGFBP-2 coincident with changes in amino acid metabolism. 相似文献
15.
To determine the effects of bovine somatotropin (bST) treatment beginning at 3 ages on the growth rate and components of the somatotropic axis, 40 beef cattle (200 +/- 21 d of age) were randomly assigned to 1 of 4 treatments (10 animals/treatment). Three of the treatment groups received bST (33 mug/kg of BW) daily beginning at 200, 250, or 300 d of age until all animals reached 400 d of age; the fourth group served as controls (0 bST). Animals were housed in pens (5 animals per pen; 2 pens per treatment) and fed a diet formulated for an ADG of 1.2 kg/d. Feed intake (per pen) was measured daily, and BW was determined weekly. Blood samples (10 mL) and ultrasound measurements were collected at 200, 250, 300, 350, and 400 d of age. Serum concentrations of ST and IGF-I were determined by RIA and IGFBP-2 and -3 by ligand blot procedures. Overall, cattle gained 284.0 +/- 14.7 kg of BW with a treatment x week interaction (P < 0.01), such that during the treatment period ADG was 11.6, 8.7, and 15.8% greater (P < 0.05) in cattle treated with bST beginning at 200, 250, and 300 d, respectively, relative to controls during the same time frame. Average DMI was 13.6% less (P < 0.05) in bST-treated cattle than in controls. Increases in ADG coupled with a reduction in DMI resulted in 11.7, 14.0, and 26.4% increases (P < 0.01) in the efficiency of gain (G:F) in bST-treated cattle beginning at 200, 250, and 300 d of age, respectively, compared with contemporary controls. Backfat thickness increased (P < 0.05) over time, but the magnitude of the increase was less in the bST-treated cattle (treatment x week interaction; P < 0.05). Area of the LM increased (P < 0.05) over time but was similar across treatment groups. Serum concentrations of ST, IGF-I, and IGFBP-3 increased (P < 0.05), whereas IGFBP-2 decreased (P < 0.05) over time. The changes in the components of somatotropic axis were more pronounced in bST-treated cattle compared with controls, with the greatest magnitude of response in animals that began bST treatment at 300 d of age. In conclusion, the exogenous bST-induced growth response was greater in animals that began to receive bST administration at 300 d of age and received it for a shorter period (100 d) compared with animals that received bST beginning at 200 or 250 d of age. 相似文献
16.
Correlation of blood and milk components with the milk yield response to bovine somatotropin in dairy cows 总被引：1，自引：0，他引：1
Our aim was to correlate the individual variation in the milk yield response (MYR) of Holstein dairy cows to bovine somatotropin (bST), with changes in milk plasmin and plasminogen activities as well as with plasma hormone and metabolite levels. Thirty-two housed multiparous Holstein cows (90 +/- 3.8 days post partum) received daily subcutaneous injections of saline for 1 week followed by subcutaneous injections of 20 mg/day of bST for 2 weeks. Blood samples were taken at approximately 4h intervals over 24 h at the end of the saline and bST treatment periods. Milk samples were also taken at the end of the saline and bST treatment periods. The difference in milk yield between the saline and the second week of bST treatment (MYR) varied considerably between animals (from -0.2 to +8.6 kg/day, relative to the saline treatment week). Low milk yield before bST treatment was associated with a high MYR. The plasma growth hormone response to treatment was negatively correlated with MYR. Plasma insulin-like growth factor-1 response to treatment was positively correlated with MYR. Furthermore, a high MYR to bST was associated with a lower milk plasminogen level before treatment and a greater reduction in the level of plasminogen in milk following treatment. 相似文献
17.
The transition from pregnancy to lactation is the most stressful period in the life of a cow. During this transition, homeorhetic adaptations are coordinated across almost every organ and are marked by changes in hormones and metabolism to accommodate the increased energetic demands of lactation. Recent data from our laboratory showed that changes in circadian clocks occur in multiple tissues during the transition period in rats and indicate that the circadian system coordinates changes in the physiology of the dam needed to support lactation. Circadian rhythms coordinate the timing of physiological processes and synchronize these processes with the environment of the animal. Circadian rhythms are generated by molecular circadian clocks located in the hypothalamus (the master clock) and peripherally in every organ of the body. The master clock receives environmental and physiological cues and, in turn, synchronizes internal physiology by coordinating endocrine rhythms and metabolism through peripheral clocks. The effect of the circadian clock on lactation may be inferred by the photoperiod effect on milk production, which is accompanied by coordinated changes in the endocrine system and metabolic capacity of the dam to respond to changes in day length. We have shown that bovine mammary epithelial cells possess a functional clock that can be synchronized by external stimuli, and the expression of the aryl hydrocarbon receptor nuclear translocator-like gene, a positive limb of the core clock, is responsive to prolactin in bovine mammary explants. Others showed that 7% of genes expressed in breasts of lactating women had circadian patterns of expression, and we report that the diurnal variation of composition of bovine milk is associated with changes in expression of mammary core clock genes. Together these studies indicate that the circadian system coordinates the metabolic and hormonal changes needed to initiate and sustain lactation, and we believe that the capacity of the dam to produce milk and cope with metabolic stresses in early lactation is related to her ability to set circadian rhythms during the transition period. 相似文献
18.
Rausch MI Tripp MW Govoni KE Zang W Webert WJ Crooker BA Hoagland TA Zinn SA 《Journal of animal science》2002,80(1):94-100
The objective of this study was to determine the effects of level of feeding on growth, feed efficiency (gain:feed; G:F), body composition (BC), and serum concentrations of somatotropin (ST), IGF-I, and IGF-binding proteins (BP) in growing beef cattle supplemented with bovine (b) ST. In each of two consecutive years, 40 growing beef cattle were blocked by weight (average BW: yr 1 = 316 kg, yr 2 = 305 kg) and used in a 2 x 2 factorial arrangement with main effects of bST (0 or 33 microg x kg BW(-1) x d(-1)) and level of feed intake (ad libitum [AL] or 0.75 AL). Relative to uninjected cattle, treatment with bST increased ADG 9.6% (1.14 vs 1.25 kg/d; P < 0.05) and increased G:F 8.1% (12.3 vs 13.3 gain [g]:feed [kg]; P < 0.05), whereas ADG in AL animals was 39% greater than that in 0.75 AL animals (1.39 vs 1.00 kg/d; P < 0.05). There was a tendency (P = 0.10) for a bST x level of feeding interaction, such that the increase in ADG with bST was greater in AL cattle than in 0.75 AL cattle (10.6 vs 7.8%; P = 0.10). Serum concentrations of ST were greater in 0.75 AL cattle than in AL cattle (13.0 vs 8.6 ng/mL; P < 0.05) and in bST-treated cattle than in uninjected cattle (16.3 vs 5.2 ng/mL; P < 0.05). Due to a bST x level of feeding interaction (P < 0.01), the magnitude of the increase in serum ST to exogenous bST was greater (P < 0.01) in 0.75 AL cattle than in AL cattle. Relative to uninjected cattle, treatment with bST increased (P < 0.05) serum concentrations of IGF-I and IGFBP-3 and reduced (P < 0.05) concentrations of IGFBP-2. Similarly, AL cattle had greater (P < 0.05) serum concentrations of IGF-I and IGFBP-3 and reduced (P < 0.05) IGFBP-2 compared with 0.75 AL cattle. In summary, treatment with bST increased growth rate and G:F and stimulated serum IGF-I and IGFBP-3 while reducing IGFBP-2. Feeding at 0.75 ad libitum intake reduced the magnitude of response for each of these variables. Thus, limit-feeding may reduce the effect of exogenous bST on growth rate by blunting bST-induced increases in IGF-I and IGFBP-3 and bST-induced decreases in IGFBP-2. 相似文献
19.
Davis JJ Sahlu T Puchala R Herselman MJ Fernandez JM McCann JP Coleman SW 《Journal of animal science》1999,77(1):17-24
Fourteen Angora does (35+/-2 kg), each with a single kid and in the first month of lactation, were used to determine ongoing (Period 1) and residual (Period 2) effects of chronic bovine somatotropin (bST) treatment. Specifically, we sought to determine whether chronic bST treatment was capable of improving milk yield, and thus kid growth, and mohair production of nursing does. The experiment consisted of a 2-wk pretreatment period, 5 wk of weekly subcutaneous treatment of slow-release bST (n = 7; Period 1), and a 4-wk posttreatment period (Period 2). The weekly dose of bST was calculated to release 100 microg/(kg BW.d(-1)). To estimate milk production, kids were separated from the does daily for 5 h, and their BW was recorded before and after suckling. The difference in BW was taken as milk production for 5 h. Fiber growth was measured by shearing does at the start of the experiment and at the end of Periods 1 and 2. Dry matter intake and BW of does were not affected by bST (P>.05). Average daily gain of kids that were suckling bST-treated does was higher (P<.05) than for kids of untreated does during Period 1 (184 vs. 139 g/d) but not during Period 2 (140 vs. 136 g/d; P>.10). Treatment with bST did not affect (P>.10) milk composition or clean fleece production in either period. Injection of bST did not affect (P>.10) plasma concentrations of glucose (mean = 49.5 mg/dL), urea N (mean = 19 mg/dL), total protein (mean = 72.5 g/d), or NEFA (mean = 122 microEq/L). During the period of bST treatment, plasma concentrations of somatotropin and IGF-I were increased (P<.05), concentrations of thyroxine and cortisol were decreased (P<.10), and plasma insulin levels were unchanged (P>.10) by bST. In conclusion, treatment of Angora dams with bST did not change DMI or mohair growth, but it improved growth of their kids. 相似文献
20.
Administration of exogenous bovine ST (bST) increases growth rate, feed efficiency, and carcass quality in beef cattle. The magnitude of response to bST in beef cattle is variable and related to the age of the animal. Our objective was to determine the response of the somatotropic axis, in particular IGF-I, IGFBP-2, and IGFBP-3, to bST treatment from birth to 1 yr of age. Blood samples were collected before and after a single injection of bST (500 mg) every 50 d from birth to 1 yr of age in male and female Hereford calves. Body weights and serum concentrations of ST, IGF-I, IGFBP-2, and IGFBP-3 were determined. At birth, serum concentrations of ST, IGF-I, and IGFBP-3 increased (P < 0.05) following bST treatment. From 50 to 350 d of age, average concentrations of ST and IGF-I were greater (P < 0.05) in males, whereas IGFBP-2 concentrations were greater (P < 0.05) in females. No gender differences in IGFBP-3 concentrations were observed. Following bST treatment, IGF-I increased (P < 0.05) from 50 to 350 d of age, IGFBP-2 decreased (P < 0.05) from 50 to 200 d of age, and IGFBP-3 increased (P < 0.05) at 250 d of age. At 250 d of age, baseline concentrations of IGFBP-2 decreased (P < 0.05). Due to the positive response of IGFBP-3 and decreased baseline IGFBP-2 at 250 d of age, we conclude that this is an age at which the somatotropic axis is most responsive to exogenous bST, and it therefore may be an appropriate age to begin bST treatment in beef calves to realize the positive influence of bST on BW gain, feed efficiency, and carcass composition. 相似文献