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1.
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   

2.
To examine the effects of exogenous porcine (p) ST on measures of stress and immune function in weaned pigs with or without transport, pigs (20 +/- 1 d of age) received daily injections of pST (0.5 mg/kg; n = 16) or saline (n = 16) for 5 d. On d 5, a blood sample was collected immediately before injection. At 4 h postinjection, pigs were weighed, sampled for blood, injected with di-nitrophenyl-conjugated keyhole limpet hemocyanin, and weaned. One half of the pigs in each group were transported for 3 h before placement in the nursery. Pigs were weighed, and blood was collected on 1, 7, and 14 d postweaning. Statistical significance was set at P < 0.05. Serum IGF-I concentrations were increased by pST and decreased by weaning, but not affected by transport. The free cortisol index was elevated in all pigs 1 d postweaning, although less in transported versus nontransported pigs. By 7 d postweaning, the free cortisol index returned to prewean values. Serum concentrations of immunoglobulin (Ig) G increased in all pigs by 14 d postweaning, but were not affected by pST or transport. Serum IgM concentrations were elevated at 7 and 14 d postweaning. Before weaning and again 1 d postweaning, pigs treated with pST had greater concentrations of IgM than did control animals. Circulating neutrophils increased in pST-treated pigs 4 h after the final pST injection. Improved immune function in weaned pigs by pST may lead to greater health and growth in a commercial setting.  相似文献   

3.
Somatotropin and adipose tissue metabolism: substrate and temporal effects   总被引：2，自引：0，他引：2  
The purpose of these studies was to determine the time course for changes in feed intake, blood metabolites, and lipogenic activity in adipose tissue in response to the initiation of porcine somatotropin (pST) treatment and following withdrawal from treatment in barrows. An initial study was conducted to determine the impact of chronic pST treatment (4 wk of daily injection; 0 vs 4 mg/d) on adipose tissue lipid metabolism in barrows (initial weight 67 kg). Feed efficiency was improved 27%, backfat thickness was decreased 43%, and glucose and lactate oxidation and incorporation into lipid in adipose tissue was reduced 70 to 86% in pST-treated pigs. Palmitate esterification was decreased 44%, whereas palmitate oxidation was unaffected. In vitro metabolism of lactate, glucose, and palmitate in liver slices was not affected by pST treatment. The time-course for changes in intake and adipose tissue metabolism in response to 7 d of pST (0 vs 4 mg/d) treatment and 7 d of withdrawal was examined in subsequent studies in barrows (initial weight 75 kg). Feed intake during pST treatment was significantly (P < .05) less than in control pigs within 24 h of the initiation of treatment and remained low through 3 d after withdrawal. Adipose tissue biopsies were obtained on d 0, 1, 2, 4, and 7 of the treatment phase and on d 2, 4, and 7 after withdrawal from 7 d of treatment. Maximal inhibition of lipogenesis by pST treatment in adipose tissue in vitro was observed on d 4 (-68%) and d 7 (-69%). Similarly, fatty acid synthase activity declined during the treatment period, with the greatest change noted on d 7 (-26%). After withdrawal from treatment, lipogenesis gradually increased, returning to control values 7 d after withdrawal. Levels of IGF-I began to increase from d 1 to d 7 of treatment, continually decreased during withdrawal, and were normalized by the end of the withdrawal period. Plasma urea nitrogen concentrations decreased during treatment, increased during the withdrawal phase, and were normalized 4 d after the last pST treatment. Overall results indicate that most of the metabolic changes in response to pST occur within 1 wk of treatment and return to pretreatment values after 7 d of withdrawal from treatment.  相似文献   

4.
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   

5.
Six sets of four littermate barrows initially averaging 75.5 kg BW were equally fed (within blocks) fortified corn-soybean meal diets (1.30% lysine) containing two concentrations of Ca (.50 and 1.00%) and P (.45% and .90%) in a 34-d test. One-half of the pigs were injected with 4 mg of porcine ST (pST)/d. Following a 7-d adjustment period, total collection of feces and urine was performed during two periods (d 1 to 10 and d 20 to 30) for the determination of Ca and P apparent digestibility (absorption) and retention. Pigs were bled after each period (d 10, 20, and 30) for the determination of serum metabolites associated with Ca, P, and bone metabolism. Feed intake for the 30-d period averaged 2,020 g/d. There were no treatment x period interactions, so the absorption and retention data were pooled across periods. The absorption and retention of Ca and P were greater (P<.01) in pigs fed the higher Ca and P levels. Within each Ca and P level, pST reduced (P<.01) fecal Ca and P excretion. Administration of pST did not affect urinary P excretion, but it increased (P<.03) urinary Ca excretion in pigs fed the low-Ca diet. The absorption and retention of Ca and P were increased (P<.01) by pST; however, the increases in Ca retention and P absorption and retention on an absolute basis (g/d) were more pronounced in pST-treated pigs consuming the higher Ca and P diet (interaction, P<.10). Serum concentrations of 1,25-dihydroxyvitamin D3, osteocalcin, and IGF-I on d 10 and 30 were increased (P<.07) with pST administration. However, the increases in 1,25-dihydroxyvitamin D3 and osteocalcin in pST-treated pigs were more pronounced when the lower dietary Ca and P levels were fed (interaction, P<.08). Urinary excretion of hydroxyproline increased (P<.01) with pST administration, but this effect was more pronounced in pST-treated pigs fed the lower Ca and P diet (interaction, P<.09). These results suggest that pST increases the absorption and retention of Ca and P independent of dietary Ca and P level. However, serum measures associated with Ca, P, and bone metabolism in pST-treated pigs were dependent on the Ca and P content of the diet, suggesting an effect of pST on the homeostatic control of Ca, P, and bone metabolism.  相似文献   

6.
Crossbred barrows were used for in vivo studies investigating hormonal regulation of lipogenesis. The first experiment examined an in vivo method for determining rates of lipogenesis. Three barrows were infused with [U-14C]glucose and incorporation of radioactivity into triglycerides was determined in up to five biopsies of subcutaneous adipose tissue obtained over 7 h. Incorporation was linear after blood glucose specific radioactivity had reached a plateau and was constant over the entire infusion. For the second experiment, eight pigs (71 +/- 2.5 kg) were allocated to one of two treatments involving daily injections of excipient (control) or porcine somatotropin (pST; 120 micrograms/kg of BW). On d 10, beginning 15 h after injection, glucose incorporation into adipose tissue lipid was determined under both basal and hyperinsulinemic/euglycemic conditions. Basal glucose incorporation into lipid, particularly fatty acids, was markedly reduced (greater than 90%) during pST treatment. Although glucose incorporation was increased to a similar extent in both groups by hyperinsulinemia, the pST-treated pigs still exhibited markedly lower rates. Based on kinetic data, the decrease in lipid accretion of pST-treated pigs was primarily the result of a decrease in the rate of de novo synthesis. Furthermore, the reductions in glucose incorporation into fatty acids, glucose irreversible loss rate, and feed intake that occur with pST treatment were quantitatively similar.  相似文献   

7.
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   

8.
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   

9.
A monoclonal antibody (mAb), PS-7.6, to porcine somatotropin (pST) significantly enhanced the growth responses to pST injections in hypophysectomized (hypox) rats but could not be tested in pigs because of the large quantity of antibody required for a growth trial. Because pST inhibits the hypoglycemic effects of insulin, an insulin tolerance test procedure was established to measure pST activity in jugular-catheterized pigs. Doses of 0, 30, 100, and 300 μg/kg per day of pST were split and administered subcutaneously (sc) in equal portions twice daily for 2 d. After a 17-hr fast, plasma samples were obtained at 10-min intervals for 30 min before an intravenous injection of insulin (0.08 IU/kg) and then for an additional 50 min. Because pST increased fasting plasma glucose concentrations, preinsulin glucose values were used as a covariate to adjust the postinsulin concentrations. pST caused a dose-dependent increase in resistance to the insulin injection in these pigs. The areas under the curves (AUC) for plasma glucose were 22.l, 29.0, 39.0, and 47.2 mg/dl per min for the 0, 30, 100, and 300 μg/kg pST doses, respectively. Because different doses of pST could be detected, the PS-7.6 enhancement of pST treatment was evaluated. In the first experiment, five pigs/group each received sc injections of either vehicle, pST (75 μg/kg; 3.0 mg/d), pST (75 μg/kg) + PS-7.6 at 3.75 mg/kg, or pST (75 μg/kg) + PS-7.6 at 15 mg/kg for 2 d before the insulin test. The pST and PS-7.6 were combined and incubated for at least 1 hr at room temperature before being injected. The injection of pST alone did not significantly change insulin tolerance activity (23.1 vs. 21.1, AUC, but insulin resistance was enhanced when this dose of pST also included PS-7.6 (27.4 and 29.5, AUC, respectively; P < 0.05). In a second experiment, the effects of PS-7.6 and PS-4.2, a mAb that did not potentiate the pST-stimulated growth of hypox rats, were compared. The five pigs/treatment received either vehicle, pST (75 μg/kg), pST (75 μg/kg) + PS-7.6 (3.75 mg/kg), or pST (75 μg/kg) + PS-4.2 (3.75 mg/kg) for 2 d. The administration of pST increased the resistance to insulin (26.7 vs. 18.8, AUC; P < 0.01), which was markedly potentiated by PS-7.6 (54.3, AUC, P < 0.001) but not affected by PS-4.2 (27.6 AUC. The injection of PS-7.6 at 7.5 mg/kg without exogenous pST did not alter the sensitivity to insulin. These results indicate that PS-7.6, but not PS-4.2, enhanced the insulin antagonistic activity of pST in swine, suggesting that an enhancement of pST-stimulated growth would also occur in PS-7.6-treated pigs.  相似文献   

10.
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   

11.
Daily injection of ovine and bovine somatotropin (oST and bST, respectively) has been shown to improve performance and carcass quality of finishing lambs. To evaluate responses to continuously released bST and porcine ST (pST), which have 99 and 91% sequence homology with oST, respectively, finishing lambs were implanted with 2-wk Alzet pumps containing bST or pST, which was released at rates of 2 or 4 mg/d. Six-week growth rate and feed efficiency responses to bST were greater than those to pST (P less than .05). Overall feed efficiency was improved 15% and growth rate was increased 16% in lambs treated with 4 mg/d of bST compared with control lambs and neither trait was affected in pST-treated lambs. Performance responses were reflected by changes in circulating glucose, blood urea nitrogen, and insulin-like growth factor I (IGF-I) concentrations. Scatchard analysis of sera with relative binding of greater than 30% revealed that average binding capacities and affinities of pST-treated lambs were 7.0 mg/liter and 6.0 x 10(9) liters/mol, respectively, and of bST-treated lambs were .8 mg/liter and 1.3 x 10(9) liters/mol, respectively. In addition, lambs with high-capacity pST antibodies had lower 6-wk IGF-I concentrations than those of controls, suggesting that these antibodies may have been attenuating responsiveness to pST. It is concluded that continuously released bST, but not pST, improves performance of finishing lambs.  相似文献   

12.
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   

13.
The acute and chronic effects of porcine growth hormone (pGH) administration on glucose homeostasis of pigs were investigated in the present study. Twelve Yorkshire barrows (average BW = 65 kg) fitted with femoral artery catheters were allotted to three groups. Pigs received acute, intra-arterial injections of either pituitary pGH, a recombinantly derived pGH analog (ppGH or rpGH, 100 micrograms/kg BW) or saline. Acute injection of pGH did not affect fasting plasma glucose or insulin status. Pigs then were treated daily by i.m. injection for 24 d with 70 micrograms ppGH/kg BW. Serum glucose and insulin concentrations during the fed and fasted states were higher in pGH-treated than in control pigs. On d 25, an acute intra-arterial injection of ppGH (100 micrograms/kg BW) elicited increases in plasma glucose and insulin in pigs chronically treated with pGH. The area circumscribed by the glucose and insulin response curves 5 min to 7 h postinjection was 40% (P less than .005) and 177% (P less than .001), respectively, higher in ppGH-treated than in control pigs. These data indicate that pGH does increase plasma glucose and insulin in the fed and fasted states; however, this response is only observed after chronic pGH administration. In addition, pGH is capable of increasing plasma glucose and insulin acutely in the pig. This effect, however, only is observed in pigs treated chronically with pGH. The mechanisms by which pGH elicit these effects on glucose homeostasis are not known.  相似文献   

14.
Forty barrows (77.9 +/- 5.5 kg BW) were allotted to one of five treatment groups to examine the effects of various doses of human growth hormone-releasing factor (1-44)NH2 (hGRF) or porcine somatotropin (pST) administered twice daily on serum hormones and metabolites, performance and carcass traits. Barrows were injected s.c. with either a placebo, 10 micrograms hGRF.kg BW-1.12 h-1, 20 micrograms hGRF.kg BW-1.12 h-1, 20 micrograms pST.kg BW-1.12 h-1 or 40 micrograms pST.kg BW-1.12 h-1 for a 36-d growth trial. Blood samples were collected from 13 barrows at intervals for 360 min after injection on d 21. Compared with the placebo, 10 micrograms hGRF.kg-1.12 h-1 increased (P less than .01) serum pST and insulin and decreased (P less than .001) urea N. Injecting 20 micrograms hGRF/kg.12 h-1 elevated (P less than .001) serum pST, insulin and insulin-like growth factor-I (IGF-I) but lowered (P less than .001) urea N. Exogenous pST increased (P less than .001) serum pST, insulin, IGF-I and glucose but decreased (P less than .001) urea N. Growth rate tended to increase, and feed intake and feed/gain decreased, in a dose-related manner in response to hGRF. Also, pigs receiving 10 or 20 micrograms hGRF.kg-1.12 h-1 had reduced (P less than .1) backfat and increased (P less than .1) loineye area and percentage lean in the ham compared with pigs receiving the placebo. At equal doses, pST elicited more dramatic improvements in performance and carcass criteria than did hGRF.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

15.
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   

16.
Sixty male and 60 female crossbred pigs were allocated to an experiment to investigate the effects of porcine somatotropin (pST) administration (0 or 6 mg/d) and dietary lysine content on growth performance, tissue deposition, and carcass characteristics over the live weight range of 80 to 120 kg. Pigs receiving pST were given diets containing 6.9, 7.8, 8.8, 9.7, 10.6, or 11.5 g lysine/kg, whereas control pigs received diets containing 4.8, 5.8, 6.9, 7.8, 8.8 or 9.7 g lysine/kg. These dietary levels ranged from 0.40 to 0.70 g available lysine/MJ of DE for pST-treated pigs and from 0.28 to 0.58 g available lysine/MJ of DE for control pigs. Pigs were individually housed in pens, and there were five replicates of each treatment. All diets contained 14.5 MJ of DE/kg and were offered for ad libitum consumption to pigs between 80 and 120 kg live weight. Growth rate increased exponentially and food conversion ratio (FCR) decreased exponentially with increasing levels of lysine. In addition, there was a significant sex x pST interaction such that pST reduced the sex difference in FCR. Growth rate was faster in boars than in gilts and was increased by pST at the higher levels of dietary lysine. Similarly, FCR was lower for boars than for gilts and was decreased by pST at the higher dietary lysine levels. The optimum growth rate and FCR were defined as the lysine level at which growth rate and FCR were 95% and 105%, respectively, of the lysine plateau. The optimum growth rate and FCR were achieved at similar dietary lysine contents and were approximately 0.35 and 0.52 g available lysine/MJ of DE for control and pST-treated pigs, respectively. Protein deposition in the carcass increased exponentially with increasing dietary lysine level, was higher in boars than in gilts, and was increased by pST at the higher dietary lysine contents. Sex had no effect on dietary lysine required to maximize protein deposition. The dietary lysine contents required to ensure 95% of plateau protein deposition of 104 and 153 g/d were 0.39 and 0.55 g available lysine/MJ of DE for control and pST-treated pigs, respectively. The increase in lysine requirement with pST seems to be commensurate with the increase in protein deposition.  相似文献   

17.
Three litters of four pigs from each of four different groups were used to evaluate the effect of porcine somatotropin (pST) on growth performance, body gain composition, energy and N metabolism, and in vitro cytochrome oxydase (final enzyme of the respiratory chain) activity of tissues. The four groups included boars from a synthetic line (SG1) or the Large White breed (SG2) and barrows from the Large White breed (SG3) or crossbred between Large White and Meishan breeds (SG4). Inherent capacity for daily lean tissue growth (LTG) decreased from SG1 to SG4. Within a litter, one pig was slaughtered and dissected at the beginning of the experiment (55 kg BW) and the three others were fed the same daily supply of protein and amino acids (26 g of lysine/d) but relative daily energy levels were either 113 (without pST: E1/0), 100 (3 mg of pST/d: E2/pST) or 87 (3 mg of pST/d: E3/pST). The 100 energy level corresponded to the ad libitum intake of E2/pST pigs. Two energy and N balances were carried out in respiration chambers during the experimental period. Pigs were slaughtered and dissected at approximately 95 kg BW and composition of gain was estimated using the comparative slaughter technique. In E1/0 pigs, daily BW, lean, and N gain were affected (P less than .01) by group; 566, 471, 374, and 315 g/d of lean tissue gain in SG1, SG2, SG3, and SG4 pigs, respectively. At high ME intake (E2/pST vs E1/0), pST increased daily BW (+14%), lean (+27%), or N (+26%) gain and reduced adipose tissue (-50%) gain, but the pST effect was inversely related to LTG: for N, the improvement was 2.8, 7.1, 7.0, and 11.1 g/d in SG1, SG2, SG3, and SG4 groups, respectively. Energy restriction (E3/pST vs E2/pST) reduced (P less than .001) adipose tissue gain in all groups but did not affect lean tissue or N gains in SG1, SG2, and SG3 pigs. In the pST-treated pigs of the SG4 group, the lean tissue or N gains were reduced (P less than .01) by energy restriction. Energy restriction combined with pST treatment (E3/pST) led to negligible amounts of fat deposited (40 g/d for SG1 + SG2 + SG3 pigs) and a gain:feed ratio higher than 500 g/kg (580 in SG1 pigs). The increased heat production measured in pST-treated pigs was due to its maintenance component: 275 vs 257 kcal of ME.kg BW-.60.d-1 (P less than .01).(ABSTRACT TRUNCATED AT 400 WORDS)  相似文献   

18.
Two experiments were conducted to assess the effects of porcine ST (pST) on the responses to a near-ideal blend of AA for pigs from 22 to 60 kg BW. Eighty Hampshire × Yorkshire gilts (40 gilts/experiment) were individually penned and assigned to a 4 × 2 factorial arrangement of treatments, consisting of 4 diets with and without pST injection. A fortified corn-soybean meal basal diet was formulated to contain 1.50% total Lys and Thr, Met, and Trp were added to obtain a near-ideal blend of these AA relative to Lys. In 3 additional diets, Lys was reduced to 1.25%, 1.00%, or 0.75% by diluting the basal diet with cornstarch, cellulose, and sand, such that the diets also contained the same ratios of AA. Pigs that received pST were administered a daily intramuscular injection of 2 mg of pST. Data from the 2 experiments were pooled. Administration of pST increased ADG (P < 0.01), G:F (P < 0.01), and LM area (P < 0.01), and decreased ADFI (P < 0.03), last rib backfat (P < 0.01), and 10th rib backfat (P < 0.01). Also, estimated carcass muscle and calculated lean gain increased (P < 0.01) in pST-treated pigs. Administration of pST also increased (P < 0.01) the percentage, total gain and accretion rate of water, protein, and ash in the carcass, and decreased (P < 0.01) the percentage, total gain, and accretion rate of carcass fat. Growth rate, G:F, and carcass traits improved (P < 0.01), percentage of carcass proteinand water increased (P < 0.01), and carcass fat percentage decreased (P < 0.01) with increasing dietary Lys. The percentage, total gain, and accretion rate of carcass protein increased to a greater extent in pST-treated pigs than in untreated pigs, resulting in a pST × Lys interaction (P < 0.05). The results indicated that pST improves performance, leanness, and protein accretion in pigs from 22 to 60 kg BW, and that these responses to dietary Lys and a near-ideal blend of AA is greater in growing pigs treated with pST than untreated pigs.  相似文献   

19.
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   

20.
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   

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