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1.
Seventy-two finishing pigs (initial weight = 57.6 kg) were utilized to determine the effects of porcine somatotropin (pST) and dietary lysine level on growth performance and carcass characteristics. Pigs were injected daily with 4 mg pST in the extensor muscle of the neck and fed either a pelleted corn-sesame meal diet (.6% lysine, 17.8% CP) or diets containing .8, 1.0, 1.2 or 1.4% lysine provided by additions of L-lysine.HCl. All diets were formulated to contain at least twice the required amounts of other amino acids. Control pigs received a placebo injection and the .6%-lysine diet. Increasing levels of dietary lysine resulted in increased ADG and improved feed conversion (quadratic, P less than .01) for pST-treated pigs. The calculated daily lysine intake was 16.6, 13.6, 19.6, 25.1, 29.6 and 33.6 g for the control and pST-treated pigs fed .6, .8, 1.0, 1.2 and 1.4% lysine, respectively, over the entire experiment. Breakpoint analysis indicated that cumulative ADG and feed conversion were optimized at 1.19 and 1.22% lysine, respectively. Longissimus muscle area and trimmed ham and loin weights increased as dietary lysine was increased among pST-treated pigs (quadratic, P less than .01). Breakpoint analysis indicated that 1.11% lysine maximized longissimus muscle area, whereas trimmed ham and loin weights were maximized at .91 and .98% lysine, respectively. Adjusted backfat thickness was not affected by dietary lysine, but pST-treated pigs had less backfat (P less than .05) than control pigs did. Percentage moisture of the longissimus muscle increased (linear, P less than .05), as did percentage CP (quadratic, P less than .05), whereas fat content decreased (linear, P less than .05) as lysine level increased. Similar trends in composition were observed for muscles of the ham (semimembranosus, semitendinosus, and biceps femoris). Shear-force values from the longissimus and semimembranosus were lowest for control pigs, but they increased as dietary lysine level increased among pST-treated pigs. Sensory panel evaluations indicated that juiciness and tenderness decreased (linear, P less than .05) as dietary lysine level increased. Plasma urea concentrations decreased linearly (P less than .01) on d 28 as lysine level increased, whereas plasma lysine and insulin were increased (quadratic, P less than .01). Plasma glucose and free fatty acid concentrations on d 28 tended to increase (quadratic, P less than .10) with increasing dietary lysine level.(ABSTRACT TRUNCATED AT 400 WORDS)  相似文献   

2.
Twenty-four barrows were used to investigate the effects of exogenous porcine somatotropin (pST) administration (0 and 100 micrograms.kg-1.d-1) between 30 and 60 kg on longissimus muscle morphology and meat tenderness of pigs grown to 90 kg. Administration of pST was by daily i.m. injection. Pigs were fed a fortified diet in restricted amounts between 30 and 60 kg and had ad libitum access to this diet from 60 to 90 kg. Excipient pigs had fewer alpha R fibers and more alpha W fibers than pST-treated pigs (P less than .05). Administration of pST increased (P less than .05) muscle fiber area for all three fiber types at both the 60 kg (34%) and 90 kg (29%) slaughter weights. Furthermore, pST administration increased shear-force (30% at 60 kg; 19% at 90 kg) of the longissimus muscle, indicating that pST administration reduced meat tenderness. All the pST-treated pigs exhibited the "giant fiber syndrome" and a high proportion (62%) of pST-treated pigs exhibited pale, soft, exudative muscle. Whether the giant fiber anomaly resulted from increased muscle protein accretion rate or fiber degeneration is unknown. Results indicated that the stimulatory effects of pST on muscle growth are sustained following cessation of hormone treatment. However, the incidence of pale, soft, exudative muscle in 62% of the pST-treated pigs indicates that pST potentially has undesirable side effects.  相似文献   

3.
Thirty two barrows were used in a 2 x 3 factorial arrangement to evaluate the effects of porcine somatotropin (pST) administration (USDA-pGH-B1; 0 and 100 micrograms.kg BW-1.d-1) and feed intake (FI; ad libitum [A], 1.64 [R1:80% of A] and 1.38 [R2:60% of A] kg/d) on longissimus (LM) muscle fiber characteristics of pigs growing from 25 to 55 kg live weight. The administration of pST resulted in an increase (P less than .05) in muscle fiber size (all three fiber types) and shear-force (17.1%). The percentage of muscle fiber types was not affected by pST treatment. Feeding of the diet at restricted levels (R1 and R2) resulted in smaller (P less than .05) beta R and alpha W fibers compared with feeding ad libitum. Pigs with ad libitum access to their diet had fewer alpha R fibers and more alpha W fibers in the LM compared with those fed at R1 and R2 levels. Restricted feed intake (R1 and R2) resulted in lower (P less than .05) shear-force values compared with ad libitum feeding. The present study indicates that pST administration of young barrows results in an increase in muscle hypertrophy. Restricted FI reduces both transformation from alpha R to alpha W fibers and muscle fiber hypertrophy.  相似文献   

4.
Sixteen crossbred sows (Yorkshire x Duroc) were used to determine the effect of recombinantly derived porcine somatotropin (pST) on lactational performance and the pattern of plasma metabolites and growth rate of nursing pigs. Daily s.c. injections of either pST (8.22 mg.sow-1.d-1) or excipient were administered at 1000 on d 12 through d 29 of lactation. Jugular cannulas were inserted in three sows/treatment and hourly blood samples were collected on d 11 to 13 and d 28 to 29 of lactation to determine the effect of treatment on plasma concentrations of somatotropin, glucose and nonesterified fatty acids in plasma. Milk production and weight of nursing pigs were determined pretreatment (d 9 and 10) and on d 16, 22 and 28. Milk production of sows receiving pST progressively increased above that of control sows and was 22% greater on d 28. Milk composition was not affected by treatment with pST (P greater than .10), so that the increase in yields of milk fat, lactose and solids paralleled the increases in milk yield. Total milk protein yield tended to be higher in sows receiving pST, but protein yield was greater (P less than .10) only on d 28. Pigs suckling sows treated with pST weighed .34 kg more at the end of the lactation period (P less than .05). Sows receiving pST consumed less feed (P less than .05) during the treatment period, and, as a result, lost more weight (P less than .10) and backfat (P less than .05) than control sows. Average concentrations of plasma somatotropin were elevated approximately 2.5-fold above baseline levels by exogenous pST. No acute alterations in plasma glucose or nonesterified fatty acids were observed in response to pST treatment, however, sows receiving pST had a chronic elevation of plasma glucose on d 29 of lactation.  相似文献   

5.
Two experiments were conducted to evaluate whether administration of recombinant porcine somatotropin (pST) to sows (Hampshire-Yorkshire) enhanced lactational performance. In Exp. 1, sows (n = 84) were fed a corn-soybean meal diet (17.8% CP), or a similar diet with 8% added fat, from d 108 of gestation to d 28 of lactation. Half of the sows fed each diet were injected with 6 mg/d of pST from d 108 of gestation to d 24 of lactation. Diets were fed at 2.27 kg/d from d 108 of gestation until farrowing and then were self-fed during lactation. By d 3 of lactation, litter size was standardized at 8 to 10 pigs per litter. Treating sows with pST resulted in a 10-fold increase (P less than .001) in serum somatotropin at 4 h postinjection. Serum glucose was increased (P less than .01) and serum triglycerides, creatinine, and urea N were decreased (P less than .01) by pST. During the summer, apparent heat stress occurred in pST-treated sows, resulting in 14 deaths. Most (10) of the deaths occurred just before, during, or shortly after farrowing. Fewer (P less than .08) deaths occurred when pST-treated sows were fed the diet with added fat. Sows treated with pST consumed less feed (P less than .10) and lost more backfat (P less than .10) during lactation than controls. Increasing the dietary fat did not prevent these changes. Weaning weights of pigs and milk yield of sows (estimated by deuterium oxide dilution) were not affected by pST treatment. In Exp. 2, sows (n = 42) were injected weekly with 0 or 70 mg of pST on d 3, 10, 17, and 24 of lactation. Litters were standardized by d 3 at 8 to 10 pigs, and sows were fed the same control (low fat) diet as in Exp. 1. Sows treated with pST consumed less feed and lost more weight and backfat during lactation than untreated sows. Litter size, average pig weaning weights, and milk yield were not influenced by pST treatment. These data indicate that a 6-mg daily injection of pST from 6 d prepartum to d 24 of lactation or a 70-mg weekly injection of pST from 3 d postpartum to d 24 of lactation does not increase milk production in lactating sows.  相似文献   

6.
Forty-eight pigs of three known stress susceptibility classes were injected daily with porcine somatotropin (pST; 4 mg/d) or a placebo. Each pig was injected in the neck once daily until taken off test, starting when the pigs weighed 59 kg. The pST treatment was terminated at weekly intervals when individual pigs reached 109 kg, but animals continued to be fed for six additional days to allow for required withdrawal time. The effect of pST and stress classification on the sensory, physical, and chemical characteristics of pork chops was observed. Also, the effect of two end-point temperatures (71 and 77 degrees C) on the sensory attributes was observed. The pST treatment of animals resulted in a small but significant decrease in panel scores for tenderness, juiciness, and flavor. Stress susceptibility class, however, decreased panel scores for tenderness only. The pST treatment reduced intramuscular fat and increased moisture in the longissimus muscle, but stress susceptibility class had no effect on proximate composition. The pST treatment and stress susceptibility decreased and increased Hunter L values of chops, respectively, indicating darker and lighter colors, respectively. Furthermore, a greater end-point temperature reduced sensory scores for tenderness and juiciness. These results suggest that pST treatment does not cause an increased incidence of pale, soft, exudative muscle. Also, the use of a lower temperature of end-point doneness (71 degrees C) should be implemented to optimize palatability of broiled pork chops regardless of pST treatment.  相似文献   

7.
Four experiments using 580 barrows and 580 gilts (Study 1) and seven experiments using 500 barrows and 500 gilts (Study 2) were conducted at various geographical locations in the United States to determine the dose response of a pelleted form of porcine somatotropin (pST) relative to ADG, feed/gain (F/G), and percentage of carcass protein. Average initial weights for Studies 1 and 2 were 67.6 and 72.6 kg, respectively, and four pigs/pen were slaughtered when they achieved weights of 106.5 to 111.0 kg. In Study 1, pigs were implanted subcutaneously with pelleted pST doses of 0, 12, 24, 36, or 48 mg/wk and self-fed a corn-soybean meal diet containing 13.75% CP. Study 2 included two control groups self-fed a diet containing either 13.75 or 17% CP with added lysine. The pST-treated pigs were administered 12, 24, or 36 mg/wk, and all were offered the 17% CP diet. The pST treatments in Study 1 resulted in a linear reduction (P less than .05) in average daily feed intake (ADFI) and a quadratic (P less than .05) improvement in F/G and percentage of carcass protein. The pST treatments in Study 2 resulted in a linear reduction in ADFI (P less than .05), a linear improvement in F/G, and a quadratic increase in the percentage of carcass protein (P less than .05). Average daily gain was not affected in either study with this form of pST. The greatest increase in efficiency of lean gain was observed with the 36-mg dose for both Study 1 (9.4%) and Study 2 (10.8%). In Study 1, the force required to shear cores of the longissimus muscle was increased linearly with pST treatment (P less than .05). There was a similar linear increase in Study 2 with pST treatment (P less than .05); however, there was also an effect of sex (P less than .05) on shear force (gilts greater than barrows) that was similar in magnitude to that observed for pST treatment. Differences in sensory evaluation because of pST were minor and of the same magnitude as those observed between barrows and gilts. It was therefore concluded that weekly administration of pST improved F/G and percentage of carcass protein with no detrimental effects on palatability of cooked lean pork.  相似文献   

8.
The dose-dependent effects of porcine somatotropin (pST) on cellular aspects of skeletal muscle growth, muscle composition and measures of pork quality were investigated in growing barrows and gilts. Eighty crossbred pigs weighing 46 kg were assigned randomly to receive daily subcutaneous injections of 0, 30, 60, 120 or 200 micrograms pST/kg BW until they weighed 100 kg. Semitendinosus muscle weights were increased with pST dose (linear, P less than .001) by 21%. Percentage of type I and type II muscle fibers was not changed with pST, but cross-sectional area of type I and type II fibers was increased in parallel with muscle weight. Percentage of moisture increased (P less than .01) and percentage of lipid decreased (P less than .01) as pST dose increased. The pH of the longissimus 24 h postmortem increased (P less than .01) .1 to .2 units with increasing pST dose, but subjective evaluation for color, firmness and wateriness of the longissimus indicated no discernible treatment effect. Gardner color difference meter "Rd" and "A" values decreased (P less than .01) with a pST dose of 60 micrograms/kg or more, signifying a slightly darker and less red color, respectively, of the longissimus muscle. Weight loss of loin chops 2.54 cm thick cooked to 71 degrees C (20.3% to 23.7%) and shear force of cores 1.27 cm in diameter (2.89 to 3.76 kg) were not related to pST treatment or dose.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

9.
Thirty-seven pigs with an initial live weight of 60 kg were used to investigate the effects of daily exogenous porcine somatotropin (pST) administration at two dose levels (0 and 100 micrograms.kg-1.d-1) for a 31-d period on muscle fiber characteristics and meat tenderness of boars, gilts and barrows. Excipient boars and gilts had more alpha W and fewer alpha R fibers than did those receiving pST. The percentage of muscle fiber type for barrows was not affected by pST treatment. The administration of pST resulted in an increase in muscle fiber size for all three fiber types in all three sexes, but these changes were of greater magnitude in barrows (31.8%) and gilts (27.8%) than in boars (9.3%). Somatotropin negated the intrinsic sex effect differences in fiber area of the pigs. There was no difference in tenderness among excipient boars, barrows and gilts; however, with the inclusion of pST, shear force decreased in boars and gilts and increased in barrows. A high proportion of the pST-treated pigs contained giant fibers in the longissimus muscle. Furthermore, a small proportion of the pST-treated pigs exhibited pale, soft, exudative muscle. Whether the giant fiber anomalies occurred through increased muscle activity or from fibers undergoing degenerative changes was not determined.  相似文献   

10.
Seventeen to twenty-three females of lean (Pietrain, PI), fat (Meishan, MS), or intermediate genotype (PI x [3/4 Large White x 1/4 MS]), referred to as crossbred (CR), were injected between 60 and 100 kg live weight with 6 mg/d of porcine somatotropin (pST) and compared to similar numbers of control females receiving the vehicle only. Average daily gain increased similarly in the three genotypes (125 g/d). Feed conversion ratio tended to decrease to a higher extent in MS (-2.0 kg of feed/kg of gain) than in the other two genotypes (-1.1 and -.9 kg of feed/kg of gain for CR and PI, respectively). A significant genotype x treatment interaction was also observed for backfat thickness (BF) and fat, muscle, and bone development. Effects of pST in PI, CR, and MS pigs were, respectively, -6.2, -9.6, and -16.1 mm for BF and 3.0, 6.8, and 11.8% carcass muscle. The influence of pST on physical measurements of meat quality was rather low, although desirable effects (P less than .05) were obtained on the reflectance and water-holding capacity of PI and CR. Intramuscular fat content was reduced by approximately 1% in MS and CR but not in PI. The metatarsals of pST-treated animals had a higher water content (except in PI), a lower mineralization, and a lower breaking strength (except in MS). The existence of breed variations in the response to pST might result in changes of the relative merit of crossbreeding schemes.  相似文献   

11.
Prepubertal gilts of obese (n = 24) or lean (n = 24) genetic lines were injected (s.c.) daily with 0, 2, or 4 mg of porcine somatotropin (pST) for 6 wk starting at 160 d of age to determine whether pST affects follicular function. Blood and ovaries were collected at slaughter 24 h after the last injection. Surface follicles greater than or equal to 1.0 mm in diameter were counted, and pools of follicular fluid (FFL) and granulosa cells were collected from 1.0- to 3.9-mm (small) and 4.0- to 6.9-mm (medium) follicles. Oocytes were collected from small and medium follicles and evaluated for maturational stage and viability. Porcine somatotropin increased (P less than .08) the numbers of small but not the numbers of medium follicles per gilt (P greater than .10). Oocyte maturation and viability were not affected by pST or genetic line. Porcine somatotropin increased (P less than .05) concentrations of insulin-like growth factor I (IGF-I) in serum and FFL of both obese and lean gilts; IGF-I was lower (P less than .01) in lean gilts. Treatment with pST decreased (P less than .05) IGF-II in FFL of lean but not in that of obese gilts. Dose of pST and line had no effect on concentrations of progesterone in FFL of small or medium follicles or on concentrations of estradiol in FFL of small follicles.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

12.
A multisector model was formulated to simulate the effects of recombinant porcine somatotropin (pST) on the U.S. hog-pork industry. A producer sector submodel was specified for nine hog-producing states, and a retail-wholesale sector was specified on a national level. Four pST adoption scenarios were tested; these differed in the extent of feed cost reduction (15 vs 25%) with or without premium pricing ($3 per animal). Simulation results show that, in general, national producer and retail prices will fall and pork consumption and production will increase due to pST use during the 5 yr of adoption. Responses to pST in terms of percentage of sows farrowing among states differed; states that produce more pork responded less than states that produce less. Downward price adjustments occurred and began stabilizing in the 4th yr; hog farmers will need to use pST to remain competitive.  相似文献   

13.
Forty-eight Yorkshire cross pigs of three stress susceptibility classes (stress positive, stress-carrier, and stress negative) were injected daily with porcine somatotropin (pST; 4 mg/d) or placebo. Each pig was injected in the neck once daily until taken off test, starting when the pigs weighed 59 kg. Porcine somatotropin treatment was terminated at weekly intervals as individual pigs reached 109 kg, but animals continued to be fed for six additional days to allow for required withdrawal time. The effect of pST and stress classification on the sensory, physical, chemical, and processing characteristics of cured semimembranosus (SM) muscle was evaluated. Treatment of animals with pST had no effect on the sensory scores, lipid and protein content, cooking yields, or color values of SM muscle slices. Semimembranosus muscles from stress-positive animals, however, had reduced sensory scores for texture, flavor, and overall palatability. Semimembranosus muscles from stress-positive pigs also had smaller cooking yields and greater Hunter a and b values of processed slices. The greater Hunter a and b values suggested that the color of these slices were redder and yellower than the color of SM muscle slices from negative and carrier animals. Semimembranosus muscles from stress-susceptible animals also had a significantly lower lipid content. Treatment of animals with pST did not significantly alter sensory, chemical, or processing characteristics of SM muscle slices from these animals.  相似文献   

14.
The effect of porcine somatotropin (pST) on the lipid profiles of adipose tissue and muscle was investigated. Sixteen crossbred barrows were injected daily with either 3 mg of pST or a placebo. After slaughter, total lipid and fatty acid composition of raw subcutaneous (SC) adipose and intermuscular (IM) adipose tissue and longissimus muscle were determined. The SC adipose tissue from pST-treated pigs had a 7.5% decrease in total lipid content; specific fatty acids 16:0, 18:0, and 18:1(n-9)c decreased most. The IM fat from pST-treated pigs had lower levels of 16:0 and 20:0. There was no effect of pST treatment on the lipid profile of the longissimus muscle. The data suggest that pST treatment produces small but significant changes in the saturated fatty acid content of adipose tissue in pigs.  相似文献   

15.
To alleviate the need for daily injection of porcine somatotropin (pST), a sustained-release implant (pSTSR) was devised that continuously delivers a daily dose of 2 mg of pST for 42 d. Ninety-six white composite (Large White x Landrace) finishing barrows (83.6 +/- 1.2 kg BW) were assigned to receive zero or two pSTSR implants (4 mg pST/d) and to consume one of six diets differing in total Lys concentration (0.29, 0.52, 0.75, 0.98, 1.21, or 1.44%, as-fed basis). Diets were formulated to be isocaloric and based on the ideal protein concept. Pigs were housed individually, allowed ad libitum access to feed and water, and slaughtered at 112 kg of BW. The pSTSR affected neither ADG (P = 0.88) nor 10th rib LM area (LMA; P = 0.51), but it decreased (P < 0.01) ADFI, average backfat thickness, 10th rib fat depth, weights of leaf fat and ham fat, improved (P < 0.05) G:F, and increased (P < 0.01) weights of four trimmed lean cuts (T-cuts), and percentages of ham lean and bone. Increasing total Lys increased ADG (quadratic; P < 0.05) and ADFI (linear; P < 0.01). The G:F, plasma urea N concentrations (PUN), and T-cuts were affected by the interaction pSTSR x dietary Lys (P < 0.01). Without pSTSR, the G:F did not differ (P = 0.37) among pigs fed 0.52% and greater total Lys. With pSTSR, the G:F was less (P < 0.05) for pigs fed 0.52% than 0.98 and 1.44% total Lys. Increases in dietary total Lys resulted in increased PUN (P < 0.01), and incremental increases were less in pSTSR-implanted pigs. Maximal yield of T-cuts was at 0.98% dietary total Lys in nonimplanted pigs and 1.21% total Lys in pSTSR-implanted pigs. Estimates of total Lys requirements of pigs without and with pSTSR, respectively, were 0.52 and 0.86% for growth (ADG and G:F) and 0.73 and 0.88% for lean production (LMA and T-cuts). Equivalent apparent ileal digestible Lys requirements of pigs without and with pSTSR, respectively, were 0.44 and 0.68% for growth, and 0.62 and 0.75% for lean production. With ADFI of 3.5 kg daily, an intake of approximately 26.1 g of total daily Lys (0.75%) or 22.4 g of apparent ileal digestible Lys is needed to maximize lean production in finishing barrows receiving 4 mg pST/d via sustained-release implant.  相似文献   

16.
Forty-eight pigs of three known stress classifications were injected daily with porcine somatotropin (pST; 4 mg/d) or placebo. The effects of pST and stress classification on the sensory, physical and chemical characteristics of loin chops were observed. Chops from pST-treated animals were less tender and juicy than chops from control animals. Positive stress classification also significantly decreased juiciness but had no effect on tenderness and flavor. A significant interaction was observed for initial juiciness and sustained juiciness between chops from pST and stress-positive pigs. Whereas chops from carriers and normal pigs showed a reduction in juiciness traits with the pST treatment, among stress-positive animals both initial and sustained juiciness were increased with pST treatment. Treatment with pST had no effect on the fat, protein, and moisture content of the longissimus muscle. Furthermore, stress classification had no effect on the fat and moisture content of the longissimus muscle, but protein content was significantly higher in loin chops from stress-positive animals. Chops from pST-treated animals had significantly higher maximum shear force values, required more energy to break the sample, and had higher yield point values than chops from control animals, but stress classification did not affect the shear force values significantly. Treatment of stress-susceptible animals with pST does not lead to an increased incidence of pale, soft, exudative meat and may improve juiciness attributes of chops from stress-positive animals. However, pST treatment of animals, in this trial, led to a reduction of juiciness and tenderness of pork loin chops.  相似文献   

17.
Neonatal pigs were treated with lipolytic agents to determine whether this would cause a long-term decrease in their ability to deposit fat, with a consequent increase in muscle growth and feed efficiency. Groups of 25 female piglets were given clenbuterol (100 microg/kg BW), porcine somatotropin (pST; 100 microg/kg BW), pST plus clenbuterol, or saline injections from 3 d to 40 d of age. Five piglets from each group were then slaughtered to determine body composition. Clenbuterol and pST both increased ADG up to weaning when given separately (24%, P < 0.05; 20%, P < 0.1 respectively) but did not reduce fat deposition. In contrast, pigs given clenbuterol plus pST showed no increase in ADG and a 41% reduction in carcass fat (P < 0.05). Clenbuterol caused a marked decrease in beta2-adrenoceptor density in porcine adipose tissue (P < 0.001) and skeletal muscle (P < 0.01). This effect was attenuated by concurrent pST treatment, which helps to explain the synergistic effect of these drugs on fat deposition. Once the drugs were withdrawn at 40 d, the anabolic effect of pST gradually disappeared, so that the live weight of pST-treated and control pigs was identical at 168 d. Clenbuterol withdrawal caused the rapid loss of extra weight gained, plus an additional 4 to 5 kg live weight that was never recovered. During the 4-wk finishing period there was an increase in feed intake in pigs that had previously undergone treatment with pST (23%, P < 0.1), with no increase in ADG, and so feed efficiency was impaired (P < 0.05). Pigs that were treated with pST plus clenbuterol showed no marked increase in feed intake during this period. Carcasses from clenbuterol-treated pigs tended to be leaner at 168 d, but there was no long-term effect of pST or the combined treatment on carcass composition. Overall, the treatment of neonatal pigs with repartitioning agents was counter-productive, due to the withdrawal effects of the beta-adrenefgic agonist and the delayed long-term effect of pST on feed intake.  相似文献   

18.
Twelve barrows (61 kg) received daily injections of either pituitary-derived porcine somatotropin (pST; 120 micrograms/kg body weight) or an equivalent volume of excipient. Blood samples were taken 1 d before initiation and on d 9 of treatment to characterize the temporal patterns of blood hormones and metabolites. Nitrogen (N) and energy (E) balances were performed on d 14 through 19 of treatment. Pigs treated with pST retained more N than controls (38.4 vs 23.0 g/d, P less than .01) and had a slightly higher apparent digestibility of N and E (88 vs 84% and 88 vs 85%, respectively, P less than .05). However, this improvement in apparent digestibility was probably a consequence of the lower feed intake (23% reduction) rather than a direct effect of pST. Treatment with pST resulted in chronic elevations in circulating concentrations of insulin-like growth factor I (406 vs 171 ng/ml), glucose (114 vs 86 mg/dl), insulin (3.9 vs 1.6 ng/ml), and nonesterified fatty acids (NEFA; 135 vs 59 mu Eq/liter). Diurnal patterns of glucose, insulin, and NEFA were also altered in pST-treated pigs. Plasma urea N levels were decreased with pST treatment (9.6 vs 24.0 mg/dl), but the diurnal pattern was unaltered. Our results indicate that the effect of pST is primarily on postabsorptive use of nutrients. In growing pigs, pST exerts a profound effect on N metabolism and on circulating concentrations of hormones and metabolites.  相似文献   

19.
Previous studies have documented the effectiveness of porcine somatotropin (pST) administered by daily injection in promoting lean tissue growth in lean and obese pigs and the influence of sex and genotype. The present study examined the accretive responses in pigs of different lines and sexes to a slow release formulation of pST (pST-SR). Implants that deliver 2.0 mg of pST/d were implanted in genetically lean and obese barrows and gilts at 65 +/- .7 kg BW (mean +/- SE). Pigs received no, one, or two implants (i.e., doses of 0, 2.0, and 4.0 mg of pST/d). Pigs (four per line x sex x dose) were housed individually and continuously supplied with fresh water and a 19% CP diet containing 1.08% lysine. Pigs were slaughtered on d 0 (four per line x sex) and at the end of the trial (approximately 42 d after implantation) for estimation of initial composition and calculation of accretion rates. Blood samples were collected at d 0, 7, 14, 28, and 42 to measure endocrine and metabolite responses to pST-SR. Sustained-release pST elevated (P < .05) circulating pST throughout the trial with peak concentrations at d 7. On d 7, serum pST concentrations in the pigs given 2.0 mg of pST-SR per day were 16-fold greater than those in control pigs, and in pigs given 4.0 mg of pST-SR per day pST concentrations were 33-fold greater than in controls. Elevated serum pST resulted in increased (P < .05) serum concentrations of insulin-like growth factor (IGF)-I, IGF-II, insulin, and glucose and in reduced (P < .05) concentrations of urea nitrogen and IGF binding protein (IGFBP)-2. Gain was not influenced by pST-SR dose; however, feed consumption was reduced (P < .05) and efficiency of gain was increased (P < .05). Accretion of all body components except cold carcass weight, cecum, and untrimmed Boston butt and ham were changed (P < .05) with pST-SR administration. Heart and stomach were the only components of the carcass and offal whose accretion was not affected by line or sex. Increases in accretion of carcass components (< 75%) induced by sustained-release pST were considerably less than those measured in the organs (liver, 157%; lungs, 748%). The pST-SR treatment resulted in elevated serum concentrations of pST and its mediators and improved efficiency and composition of gain.(ABSTRACT TRUNCATED AT 400 WORDS)  相似文献   

20.
The dose-dependent effects of porcine somatotropin (pST) on growth performance and composition of carcass gain were investigated in 150 growing pigs. The experiment involved two genotypes (barrows from the Pig Improvement Company [PIC] and a University of Nebraska [NEB] gene pool line) and two sexes (PIC barrows and boars). At 30 kg, pigs were randomly assigned within each genotype and sex subclass to receive daily i.m. injections of 50, 100, 150, or 200 micrograms of pST/kg BW or an equivalent volume of an excipient. A diet (3.5 Mcal of DE/kg) supplemented with crystalline amino acids and containing 22.5% CP was available on an ad libitum basis until pigs were slaughtered at approximately 90 kg live weight. Excipient-treated PIC barrows exhibited faster and more efficient growth (P less than .001) and a higher capacity for carcass protein accretion (P less than .001) but similar rates of lipid deposition compared to excipient-treated NEB barrows. Within the PIC genotype, control boars grew at a rate similar to that of barrows, but they were more efficient (P less than .05) and deposited more carcass protein (P less than .05) and less lipid (P less than .001). Carcass protein accretion rate increased (P less than .001) up to approximately 150 micrograms of pST.kg BW-1.d-1, whereas lipid deposition decreased (P less than .001) with each incremental dose of pST. Although differences between PIC boars and barrows for all criteria were negated with increasing pST dose, they were maintained between the two genotypes. Polynomial regressions suggested that a slightly higher pST dose was required to optimize the feed:gain ratio compared with rate of gain and that the dose (micrograms per kilogram BW per day) was a function of the genotype and sex (feed:gain: 185, 170, and 155; rate of gain: 155, 155, and 125 for NEB barrows, PIC barrows, and PIC boars, respectively).  相似文献   

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