Growth hormone increases whole-body protein turnover in growing pigs.

Ten pigs with an average initial live weight of 65 kg were used to investigate the effects of daily exogenous porcine pituitary growth hormone (pGH; .1 mg.kg-1.d-1) for a 13-d period on N retention and whole-body protein turnover. Feed intake was restricted to both the control (treated with excipient) and pGH-treated groups to ensure that animals in each group consumed equal amounts. Whole-body protein turnover was estimated from the excretion of 15N in urinary urea and ammonia after a single oral dose of [15N]glycine. Nitrogen balance and whole-body N flux were increased by 35 to 40% with pGH treatment (P less than .001). Protein synthesis and breakdown were increased by 56 and 59% (P less than .001), respectively, in pGH-treated pigs relative to controls. These higher rates of protein turnover seemed to lower slightly the efficiency of the metabolic process for protein deposition. However, the absolute increment in protein synthesis rate was greater than that for breakdown, leading to the increased net N retention. Thus, pGH treatment improved the utilization of dietary amino acids for protein deposition.     

Effects of exogenous porcine growth hormone administration between 30 and 60 kilograms on the subsequent and overall performance of pigs grown to 90 kilograms

Twenty-eight barrows were used to investigate the effects of exogenous porcine growth hormone (pGH) administration (0 and 100 micrograms.kg-1.d-1) between 30 and 60 kg on the subsequent and overall performance and carcass composition of pigs grown to 90 kg. The pGH was administered by daily i.m. injection and all pigs were fed one diet. Control animals were pair-fed to the intake noted for pGH-treated pigs between 30 and 60 kg and all pigs were fed ad libitum from 60 to 90 kg. Pigs administered pGH had an improved rate (36%) and efficiency (28%) of gain and an improved protein accretion rate (46%) compared to excipient-treated pigs. Pigs previously treated with pGH continued to exhibit superior (P less than .01) rate and efficiency of gain, and the gain was associated with enhanced protein accretion during the quiescent (postinjection) period compared with excipient counterparts. Administration of pGH between 30 and 60 kg reduced carcass fat and increased carcass protein and water at 90 kg, although fat accretion rate was comparable to that of control pigs. Results indicate that, to varying degrees, the stimulatory effects of pGH on growth performance are sustained following cessation of hormone treatment.     

Effects of gender and genotype on the response of growing pigs to exogenous administration of porcine growth hormone

Sixty crossbred pigs (Large White x Landrace) were used in a 2 x 2 x 2 factorial experiment to investigate the effects of gender (intact males vs females) and strain (A vs B) on the response to exogenous porcine growth hormone (pGH) administration (0 [excipient-treated] vs .1 mg pGH.kg live weight-1.d-1). All pigs had ad libitum access to their diet; pGH was administered daily from 60 to 90 kg live weight. All aspects of growth performance and body composition were affected to different degrees by gender and pGH. Strain A pigs had a higher capacity for protein accretion, superior growth performance and contained less fat in the eviscerated carcass and empty body compared with Strain B pigs. Within each strain, intact males ate more feed, had a higher rate of protein deposition and exhibited faster and leaner growth than females. Exogenous pGH administration increased average protein deposition and growth rate by 84 and 34%, respectively, and reduced average feed intake, fat deposition rate, feed:gain and carcass fat content by 14, 59, 37 and 33%, respectively. The magnitude of the changes in growth performance, tissue accretion rates and body composition elicited by pGH were independent of strain. However, within each strain the improvement in feed:gain and reduction in carcass fat measurements elicited by pGH were proportionately larger for females than for intact males.     

Interrelationships between energy intake and endogenous porcine growth hormone administration on the performance, body composition and protein and energy metabolism of growing pigs weighing 25 to 55 kilograms live weight

Thirty-six barrows were used in a 2 X 3 factorial experiment to investigate the effects of porcine growth hormone (pGH) administration (USDA-pGH-B1; 0 and 100 micrograms.kg body weight-1.d-1) and three levels of feeding of a single diet (EI; ad libitum, 1.64 and 1.38 kg/d) on the performance, body composition and rates of protein and fat deposition of pigs growing over the live weight phase 25 to 55 kg. Raising EI resulted in linear increases in growth rate and in protein and fat accretion but had no effect on the feed to gain ratio (F/G). Carcass fat content and carcass fat measurements also increased with EI, whereas carcass protein and water decreased (P less than .01). Growth hormone administration resulted in improvements in growth rate (16 to 26%), F/G (23%), protein deposition (34 to 50%) and increases in carcass protein and water at each level of feeding, but reduced ad libitum feed intake (P less than .01), carcass fat content (P less than .01) and carcass fat measurements (P less than .01). Estimated maintenance energy expenditure was increased by pGH administration (2.02 vs 1.72 Mcal digestible energy/d). Results indicate that the effects of pGH on growth performance and energy and protein metabolism were largely independent of, and additive to, the effects of energy intake.     

Stimulation of pig growth performance by porcine growth hormone: determination of the dose-response relationship

The present study was undertaken to determine the relationship between dose of porcine growth hormone (pGH) and growth performance of pigs. Porcine GH was administered daily for 35 d [buffer-injected control = (C); 10 micrograms/kg body weight (BW) = (L); 30 micrograms/kg BW = (M); 70 micrograms/kg BW = (H)] to barrows (initial wt = 50 kg). Growth rate was significantly increased by pGH (14% for H dose vs C). Feed efficiency was increased in a dose-related manner (L = 7%, M = 10%, H = 17%) by pGH. There was a concurrent change in carcass composition of pGH-treated pigs. The H dose of pGH decreased the percentage of carcass lipid by 25% (P less than .05). Muscle mass was significantly increased in H vs C pigs (31 vs 26 kg). Serum insulin-like growth factor 1 (IGF-1) concentration increased in a manner that was linearly related to the pGH dose (r = .87). No antibodies to pGH were detected in any of the pigs. In summary, these results extend our earlier findings that pGH increases growth performance markedly. Based on the present findings it appears that the maximally effective dose of pGH is greater than 70 micrograms.kg BW-1.d-1 since several indices of the growth-promoting and metabolic effects of pGH (% carcass protein, % carcass lipid and feed efficiency) had not plateaued.     

Interrelationships between sex and exogenous growth hormone administration on performance, body composition and protein and fat accretion of growing pigs

Forty-five pigs with an average initial live weight of 60 kg were used to investigate the effects of daily exogenous porcine pituitary growth hormone administration at two dose levels (pGH; 0, excipient buffer injected, and 100 micrograms.kg-1.d-1) for a 31-d period on the performance and body composition of boars, gilts and barrows allowed to consume feed ad libitum. Excipient boars consumed less feed, exhibited faster and more efficient growth (P less than .01) and produced less fat and more protein and water (P less than .01) in the empty body compared with excipient barrows, which in turn contained more fat and less water (P less than .05) in the empty body than did excipient gilts. These differences were largely eliminated by pGH administration, which induced differential effects in growth performance and body composition in boars, gilts and barrows. Growth hormone administration improved growth rate by 13, 22 and 16% and feed conversion efficiency by 19, 34 and 32% in boars, gilts and barrows, respectively. The reduction of body fat content (g/kg) elicited by pGH was 22, 36 and 33% for boars, gilts and barrows, respectively, with a corresponding increase (P less than .01) of body protein and water content. The magnitude of the pGH responses was greatest for gilts and barrows compared with boars, negating intrinsic sex-effect differences in growth performance and body composition of pigs. Pigs used in this study and treated with pGH exhibited a rate of protein deposition (approximately 225 g/d) far greater than previously reported, and as such redefine the genetic capacity for lean tissue growth by the pig.     

Interrelationships of exogenous porcine growth hormone administration and feed intake level affecting various tissue levels of iron, copper, zinc and bone calcium of growing pigs

Trace mineral status was evaluated in a 2 x 3 factorial treatment array with a total of 34 barrows growing from 25 to 55 kg live weight. Treatments included three levels of feed intake (100, 80 and 60% of ad libitum intake) and exogenous pituitary growth hormone (pGH) therapy (0 and 100 micrograms/kg BW daily). Blood was collected prior to slaughter for the determination of hematocrit and serum trace metal concentrations; tissues (liver, heart, kidney, bone and muscle) were obtained when pigs were slaughtered at 55 kg. Hematocrits and serum Fe were lower in pGH-treated pigs than in controls at all levels of feed intake. Serum Cu was increased by feed restriction but was not altered by pGH therapy. The concentration of serum Zn was not affected by either treatment. Concentrations of hepatic Fe and Cu were lower in pGH-treated pigs than in controls but were higher in feed-restricted pigs than in ad libitum-fed pigs. However, the total amounts of hepatic Fe and Cu were similar in pGH-treated pigs to concentrations in controls. The concentration of hepatic Zn was not influenced by either pGH treatment or feed intake. Femur weights were marginally greater in pGH-treated pigs, probably due to elevated water content. Iron concentration in bone was higher in pGH-treated pigs than in control pigs, whereas Ca, Cu and Zn were not influenced by pGH treatment or feed restriction. Feed intake and pGH treatment did not influence the concentrations of Fe, Cu or Zn in muscle. These findings indicate that pGH therapy affects the metabolism of Fe but has little impact on the overall composition of body ash.     

Influence of dietary protein and recombinant porcine somatotropin administration in young pigs: II. Accretion rates of protein, collagen, and fat.

The present study was conducted to determine the effects of different dietary protein levels and recombinant porcine somatotropin (rpST) administration on deposition rates of protein, fat, water, ash, and collagen in pigs. Ten groups of six barrows (30 kg BW) were restrictively fed (80% of ad libitum) one of five diets containing 11, 15, 19, 23, or 27% CP. Diets were isoenergetic and all contained equivalent amounts of lysine. Thirty barrows were treated daily with rpST (100 micrograms/kg) by i.m. injection; remaining pigs were treated with diluent for 42 d. At all levels of dietary protein intake, carcass and empty body accretion rates of protein, water, and ash were greater in rpST-treated pigs than in respective controls. The magnitude of change elicited by rpST was lowest in pigs consuming 11% CP. Administration of rpST resulted in a 34% decrease in the accretion rate of fat; increasing protein intake resulted in a linear decrease in fat accretion in control and rpST-treated pigs. Accretion rates of protein, water, ash, and fat were increased in viscera of rpST-treated pigs compared with respective controls; rates of visceral protein and water accretion were increased as dietary protein was increased, whereas deposition of fat was decreased in control and rpST-treated pigs. Administration of rpST resulted in an overall 66% increase in the utilization efficiency of dietary protein for empty body protein deposition. Protein intake had minimal effect on the concentration of collagen in the carcass; however, rpST treatment increased concentrations of total and soluble collagen by 30 and 33%, respectively. Recombinant pST had little influence on collagen crosslinking or maturation. Deposition rate of carcass collagen was increased 63% in rpST-treated pigs compared with respective controls.     

Effects of growth hormone administration on vitamin D metabolism and vitamin D receptors in the pig

Twelve 36-kg pigs were given either 100 micrograms/kg porcine pituitary growth hormone (pGH) or placebo injections daily for 33 days. Serum was obtained weekly for analysis of minerals and vitamin D metabolites. On day 34, the pigs were sacrificed and renal and duodenal tissue were obtained for analysis of vitamin D receptor content (VDR). Animals treated with pGH grew faster and had a higher rate of bone accretion than did control animals. Serum concentrations of 1,25-dihydroxyvitamin D (1,25-(OH)2D) were significantly higher in pGH-treated pigs than in control pigs at all time points following initiation of treatment, with the greatest difference observed at day 28 (42.4 +/- 4.9 pg/ml in controls vs. 65.4 +/- 4.7 pg/ml in pGH-treated pigs). Serum 24,25-dihydroxy-vitamin D tended to be lower in pGH-treated pigs than in control pigs, being significantly lower on day 21 of the experiment (3.22 +/- .52 vs. 6.73 +/- 1.22 ng/ml, respectively). Serum concentrations of 25-hydroxyvitamin D and calcium were unaffected by pGH treatment. Kidneys of control pigs contained significantly more unoccupied vitamin D receptors than did kidneys from pGH-treated pigs (73.3 +/- 4.3 vs. 58.3 +/- 4.1 fmoles/mg protein). Duodenal tissue unoccupied vitamin D receptor content was similar in both pGH-treated (245 +/- 17.9 fmoles/mg protein) and control (263 +/- 21.8 fmoles/mg protein) pigs. Duodenal occupied vitamin D receptor concentration was similar in both pGH-treated (6.8 +/- .75 fmoles/mg protein) and control pigs (5.32 +/- .77 fmoles/mg protein).(ABSTRACT TRUNCATED AT 250 WORDS)     

Stimulation of pig growth performance by porcine growth hormone and growth hormone-releasing factor

The current study was undertaken to determine the effects of human growth hormone-releasing factor [hpGRF-(1-44)-NH2] on growth performance in pigs and whether this response was comparable to exogenous porcine growth hormone (pGH) treatment. Preliminary studies were conducted to determine if GRF increased plasma GH concentration after iv and im injection and the nature of the dose response. Growth hormone-releasing factor stimulated the release of pGH in a dose-dependent fashion, although the individual responses varied widely among pigs. The results from the im study were used to determine the dose of GRF to use for a 30-d growth trial. Thirty-six Yorkshire-Duroc barrows (initial wt 50 kg) were randomly allotted to one of three experimental groups (C = control, GRF and pGH). Pigs were treated daily with 30 micrograms of GRF/kg body weight by im injection in the neck. Pigs treated with pGH were also given 30 micrograms/kg body weight by im injection. Growth rate was increased 10% by pGH vs C pigs (P less than .05). Growth rate was not affected by GRF; however, hot and chilled carcass weights were increased 5% vs C pigs (P less than .05). On an absolute basis, adipose tissue mass was unaffected by pGH or GRF. Carcass lipid (percent of soft-tissue mass) was decreased 13% by GRF (P less than .05) and 18% by pGH (P less than .05). Muscle mass was significantly increased by pGH but not by GRF. There was a trend for feed efficiency to be improved by GRF; however, this was not different from control pigs. In contrast, pGH increased feed efficiency 19% vs control pigs (P less than .05). Chronic administration of GRF increased anterior pituitary weight but did not affect pituitary GH content or concentration. When blood was taken 3 h post-injection, both GRF- and pGH-treated pigs had lower blood-urea nitrogen concentrations. Serum glucose was significantly elevated by both GRF and pGH treatment. This was associated with an elevation in serum insulin. These results indicate that increasing the GH concentration in blood by either exogenous GH or GRF enhances growth performance. The effects of pGH were more marked than for GRF. Further studies are needed to determine the optimal dose of GRF to administer in growth trials and the appropriate pattern of GRF administration in order to determine whether GRF will enhance pig growth performance to the extent that exogenous pGH does.     

Effects of porcine growth hormone on glucose metabolism of pigs: I. Acute and chronic effects on plasma glucose and insulin status

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.     

Interrelationships between exogenous porcine somatotropin (PST) administration and dietary protein and energy intake on protein deposition capacity and energy metabolism of pigs

Exogenous porcine somatotropin (PST) administration stimulates protein deposition and inhibits lipogenesis, resulting in dose-related improvements in growth performance and reduction of carcass fat content. However, the associated impacts of this technology on dietary nutrient requirements and energy partitioning between maintenance, protein, and fat remain unclear. Studies with pigs between 25 and 60 kg body weight indicate that, because of unknown improvements in amino acid utilization and(or) in the energy available for protein synthesis, only marginal increases in dietary protein percentage are required to support 20 to 25% improvements in protein deposition induced by PST administration. In contrast, an increased dietary protein concentration is required to support maximal protein deposition in pigs 60 to 100 kg. Exogenous PST administration increased the maintenance energy requirement and altered the relationship between energy intake and protein deposition, although the magnitude of these changes and the consequent effects on expression of dietary protein (amino acid) requirements was influenced by gender. Albeit limited, information suggests that PST alters nutrient demand at the tissue level. Information of this type will form the basis for rational decisions concerning the method for expression of dietary nutrient requirements (% vs g/d) for PST-treated pigs. Further quantitative information is required on the effects of PST dosage on the relationship of protein deposition to energy intake and on any underlying changes in amino acid utilization and metabolism.     

Influence of dietary protein and recombinant porcine somatotropin administration in young pigs: growth, body composition and hormone status

The influence of dietary protein and recombinant porcine somatotropin (rpST) administration on growth and body composition was investigated in barrows. Ten groups of six pigs starting at 30 kg were restrictively fed (approximately 80% of ad libitum) one of five diets containing 11, 15, 19, 23 or 27% protein. Diets contained skim milk (12%). Soybean meal diluted with cornstarch was used as the supplemental source of dietary protein. Diets were isocaloric (3.8 Mcal DE/kg) and all contained the same amount of lysine (18 to 20 g/kg). Thirty pigs were treated daily with rpST (100 micrograms/kg) by i.m. injection; the remaining pigs were treated with sterile diluent (control) for 42 d. Growth rate was greater in rpST-treated pigs at all levels of protein intake; however, the magnitude of the response to rpST treatment was lowest among pigs fed the diet containing 11% protein. Feed:gain ratio, backfat depth and carcass fat content were decreased in rpST-treated pigs compared to respective controls. Additionally, the concentration of carcass fat decreased concomitantly with an increase in dietary protein intake. Concentration of carcass protein increased linearly as dietary protein increased in control and rpST-treated pigs. In contrast, treatment with rpST was associated with an increased visceral mass; the concentration of protein and fat in the viscera was influenced by protein intake but not by rpST. These results, characterized by few treatment interactions, suggest that when energy intake is kept constant and appropriately fed pigs serve as controls, dietary protein and rpST influence growth and body composition by independent mechanisms.(ABSTRACT TRUNCATED AT 250 WORDS)     

Evaluation of various extracted vegetable oils, roasted soybeans, medium-chain triglyceride and an animal-vegetable fat blend for postweaning swine

A total of 280 crossbred pigs weaned at 21 d of age and weighing approximately 6 kg were utilized in five replicates to evaluate pig growth responses when fed a basal diet or one of several dietary lipid sources during a 4-wk postweaning period. A basal corn-soybean meal-corn starch-dried whey diet was compared with diets supplemented at a 7.75% level with one of the following lipid sources: corn oil, coconut oil, soybean oil, medium-chain triglyceride (MCT) or an animal-vegetable blend. A sixth treatment evaluated a roasted soybean diet formulated to an energy:lysine level equivalent to that of the fat-supplemented diets. In Exp. II, 36 crossbred weanling barrows were used to determine apparent fat and N digestibilities when soybean oil, roasted soybean, coconut oil or the MCT-supplemented diets were fed. Although pigs fed coconut oil grew somewhat faster, fat inclusion generally did not increase pig growth rate or result in lowered feed intake during the initial weeks postweaning; during the latter portion of the starter phase the addition of dietary fat resulted in a higher growth rate but feed intake was unaffected, resulting in an overall improvement in feed-to-gain ratio (P less than .05) for all but the roasted soybean diet. Pigs fed coconut oil had higher serum triglyceride and lower serum urea concentrations than did pigs fed diets containing most other lipid sources. Pigs fed MCT and coconut oil diets had a higher (P less than .01) apparent fat digestibility during the initial 2 wk postweaning than pigs fed soybean oil or roasted soybean diets. Pigs fed MCT and roasted soybeans had poorest growth rates; apparent fat and N digestibilities were lowest (P less than .05) for the roasted soybean diet.     

Interrelationships between dietary lysine, sex, and porcine somatotropin administration on growth performance and protein deposition in pigs between 80 and 120 kg live weight

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.     

Amino acid and energy interrelationships in pigs weighing 20 to 50 kilograms: II. Rate and efficiency of protein and fat deposition

Two experiments were conducted to investigate the relationships between amino acids and DE for pigs weighing 20 to 50 kg. In Exp. 1, there were three dietary lysine levels that were either adjusted (1.50, 2.35 and 3.20 g/Mcal DE) for five DE levels (3.00 to 4.00 Mcal/kg) or unadjusted (.45, .71 and .96% of the diet) for three DE levels (3.50 to 4.00 Mcal/kg). In Exp. 2, diets containing six lysine:DE ratios (1.90 to 3.90 g/Mcal) at two DE levels (3.25 and 3.75 Mcal/kg) were fed. Pigs were housed individually, and could eat and drink ad libitum. When pigs weighed 50 kg, their empty body composition was determined by the urea dilution technique in Exp. 1 and by prediction equations based on backfat in Exp. 2. For the adjusted diets in Exp. 1, protein deposition and protein deposition:DE intake increased (P less than .01) slightly as DE levels increased. These criteria decreased linearly (P less than .001), and fat deposition increased (P = .11) as DE increased when lysine:DE ratios were not maintained. As lysine levels increased, protein deposition and protein deposition: DE intake increased (P less than .001) in both the adjusted and unadjusted diets. In Exp. 2, there was no effect of DE on either the rate or efficiency of protein deposition. Both protein deposition and protein deposition:DE intake increased (P less than .001) and fat deposition decreased as lysine:DE ratios increased up to 3.00 g lysine/Mcal DE. Protein deposition: lysine intake decreased (P less than .01) progressively as the lysine:DE ratio increased. Regression analyses indicated the protein deposition increased up to 3.00 g lysine/Mcal DE. The results demonstrate the need to adjust lysine according to energy levels and indicate that the optimum ratio for protein deposition was approximately 3.00 g lysine/Mcal DE (or 49 g of balanced protein/Mcal DE).     

日粮蛋白质水平对乌金猪肝脏组织脂类代谢相关基因表达的影响

为探讨日粮蛋白质水平对乌金猪肝脏组织脂类代谢相关基因表达的影响,试验选取体重约15 kg的乌金猪54头,随机分为3组,每组18头,为低、中和高蛋白质组,其在15～30、30～60及60～100 kg生长阶段的蛋白质水平分别为14%、12%、10%,16%、14%、12%和18%、16%、14%。猪在体重为30、60和100 kg时屠宰,取其肝脏组织,Real-time PCR定量检测脂类代谢相关基因的表达水平。结果显示,在30、60和100 kg时,乌金猪肝脏组织中ACC、FAS、SREBP-1C基因的表达水平均随着蛋白质水平的升高而降低;CPT-Ⅰ和PPARα基因的表达水平则随着蛋白质水平的升高而升高。由此表明,日粮高蛋白质水平显著降低肝脏脂肪酸合成代谢基因(ACC、FAS和SREBP-1C)的表达(P<0.05),提高脂肪酸分解代谢基因(CPT-Ⅰ和PPARα)的表达水平(P<0.05);脂肪酸合成减少,且被氧化的量增加,两者共同作用导致用于合成甘油三酯(TG)的脂肪酸含量降低,从而减少了从肝脏组织被运输到各个组织的TG含量,使机体沉积TG的能力降低。     

Effects of porcine growth hormone on glucose metabolism of pigs: II. Glucose tolerance, peripheral tissue insulin sensitivity and glucose kinetics

This study was conducted to determine whether the increase in serum glucose observed in pigs treated chronically with pGH is due to an increase in hepatic glucose output or to an impairment in glucose clearance. Barrows (n = 4 per treatment) were treated with pituitary derived pGH (ppGH), recombinant pGH analog (rpGH) or vehicle. Pigs were treated for 28 d by daily i.m. injections. Insulin tolerance and glucose tolerance tests (GTT) were performed on d 19 and 21, respectively, following treatment with pGH. Glucose turnover was quantified on d 28 using [6-3H]glucose. Chronically treating pigs with pGH resulted in a significant decrease (26%; P less than .05) in glucose clearance, as determined by the GTT. Glucose clearance was affected similarly by ppGH and rpGH. Intra-arterial glucose infusion markedly increased plasma insulin concentration in pGH-treated pigs. Peak plasma insulin response was 87% and 58%, respectively, higher (P less than .05) in ppGH- and rpGH-treated than in control pigs. Insulin infusion elicited a marked hypoglycemia in pigs; however, the extent and duration of hypoglycemia were significantly less in pGH-treated pigs (ppGH or rpGH). Glucose production rates were 23% higher (P = .085) in ppGH-treated than in control pigs. These results establish that the hyperglycemia induced by pGH is the result of an increase in hepatic glucose output and a concurrent impairment in glucose clearance.     

Synergistic effects of betaine and conjugated linoleic acid on the growth and carcass composition of growing Iberian pigs

An experiment was conducted to determine the efficacy of dietary betaine, CLA, or both as growth promotants and carcass modifiers in growing Iberian pigs. Twenty gilts (20 kg of BW) were individually penned and fed barley- and soybean meal-based diets (12% CP, 0.81% Lys, and 14.8 MJ of ME/kg of DM) containing either no added betaine or CLA (control), 0.5% betaine, 1% CLA, or 0.5% betaine + 1% CLA, at 95% of ad libitum energy intake. An additional group of 5 pigs was slaughtered at the beginning of the experiment to obtain the initial body composition. At 30 kg of BW, a balance experiment was conducted. At 50 kg of BW, pigs were slaughtered and viscera was removed and weighed. Betaine or CLA alone did not affect growth performance. However, betaine + CLA increased ADG (601 vs. 558 g, P = 0.03) and gain relative to ME intake (25.4 vs. 22.2 g/MJ, P = 0.03) compared with control pigs. Digestibility of nutrients and metabolizability of energy did not differ among diets (P = 0.46 to 0.75). Carcass protein, water, and lean deposition (g/d) increased (19.8, 24.2, and 23.4%, respectively, P < 0.01) in pigs fed betaine + CLA compared with control pigs. Similarly, protein deposition relative to ME intake increased by 28% in betaine + CLA-supplemented pigs (P < 0.05). Fat and mineral deposition did not differ among treatments. Carcass protein, water, and lean content (g/kg of carcass) of pigs fed betaine + CLA-supplemented diets tended to increase (P = 0.07 to 0.09) and carcass fat content tended to decrease (P = 0.09). Similarly, estimated composition of carcass gain was affected, such that water and lean content tended to increase (P = 0.06 to 0.08), whereas fat tended to decrease (P = 0.08) in pigs fed betaine + CLA-supplemented diets. Longissimus muscle area was not altered by treatments (P = 0.49). The liver of pigs fed betaine + CLA diets had increased weight (19%, P < 0.05) compared with control pigs. Overall, dietary supplementation of betaine + CLA increased ADG, protein, water, and lean deposition in growing Iberian gilts. There appears to be a synergistic action when betaine and CLA are used together.     

Effect of dietary betaine on nutrient utilization and partitioning in the young growing feed-restricted pig

The purpose of this study was to examine the effects of dietary betaine over a range of concentrations (between 0 and 0.5%) on growth and body composition in young feed-restricted pigs. Betaine is associated with decreased lipid deposition and altered protein utilization in finishing pigs, and it has been suggested that the positive effects of betaine on growth and carcass composition may be greater in energy-restricted pigs. Thirty-two barrows (36 kg, n = 8 pigs per group) were restrictively fed one of four corn-soybean meal-skim milk based diets (18.6% crude protein, 3.23 Mcal ME/kg) and supplemented with 0, 0.125, 0.25, or 0.5% betaine. Feed allotment was adjusted weekly according to BW, such that average feed intake was approximately 1.7 kg for all groups. At 64 kg, pigs were slaughtered and visceral tissue was removed and weighed. Carcasses were chilled for 24 h to obtain carcass measurements. Subsequently, one-half of each carcass and whole visceral tissue were ground for chemical analysis. Linear regression analysis indicated that, as betaine content of the diet was elevated from 0 to 0.5%, carcass fat concentration (P = 0.06), P3 fat depth (P = 0.14) and viscera weight (P = 0.129) were decreased, whereas total carcass protein (P = 0.124), protein deposition rate (P = 0.98), and lean gain efficiency (P = 0.115) were increased. The greatest differences over control pigs were observed in pigs consuming 0.5% betaine, where carcass fat concentration and P3 fat depth were decreased by 10 and 26%, respectively. Other fat depth measurements were not different (P > 0.15) from those of control pigs. In addition, pigs consuming the highest betaine level had a 19% increase in the carcass protein:fat ratio, 23% higher carcass protein deposition rate, and a 24% increase in lean gain efficiency compared with controls. Dietary betaine had no effects (P > 0.15) on growth performance, visceral tissue chemical composition, carcass fat deposition rate, visceral fat and protein deposition rates, or serum urea and ammonia concentrations. These data suggest that betaine alters nutrient partitioning such that carcass protein deposition is enhanced at the expense of carcass fat and in part, visceral tissue.