Effects of recombinant porcine somatotropin on growth and carcass traits in meishan pigs

Effects of recombinant porcine somatotropin (rpST) on growth, feed intake, feed conversion, back-fat thickness and lean percentage were examined in growing Meishan pigs. The experiment comprised 42 barrows of which 20 were administered 14 mg rpST twice a week i.m., starting at 40 kg, the others received a placebo. Pigs were fed ad libitum a diet containing 9.2 MJ net energy and 156 g crude protein kg⁻¹ and were slaughtered at 90 kg liveweight. From 40 to 90 kg liveweight, rpST effects were: daily gain +17.9%; feed intake −5.1%; feed conversion −17.5%; backfat thickness −29.8%; lean percentage +16.0%. The effects of rpST in Meishan are much larger than in a similar experiment with leaner western pigs. Development of synthetic breeds with Meishan in combination with the use of rpST in cross-bred fattening pigs may be a way to economically exploit the high fertility of Meishan.     

Effect of feed intake and exogenous porcine somatotropin on longissimus muscle fiber characteristics of pigs weighing 55 kilograms live weight

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.     

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.     

Effect of recombinant porcine somatotropin on growth and carcass quality in growing pigs: interactions with genotype, gender and slaughter weight

Effects of recombinant porcine somatotropin (rpST) on growth, lean tissue growth, feed intake, feed conversion, lean tissue feed conversion, backfat thickness and lean percentage were examined in 96 growing pigs. The experiment used barrows and gilts from the genotypes Duroc, F1 (Dutch Yorkshire x Dutch Landrace) and Pietrain. Half the pigs received 14 mg rpST i.m. twice each week starting at 60 kg; others received a placebo. Pigs had ad libitum access to a diet containing 2,162 kcal net energy and 182 g crude protein per kilogram and were slaughtered at either 100 or 140 kg live weight. From 60 to 100 and from 100 to 140 kg, live weight responses to rpST averaged as follows: daily gain, +4.5 and +19.9%; feed intake, -4.4 and +3.5%; feed conversion, -8.4 and -13.9%; backfat thickness, -13.8 and -22.8%; lean percentage, +4.4 and +8.7%; lean tissue growth rate, +8.6 and +35.8%; and lean tissue feed conversion, -13.1 and -24.9%. No gender x rpST interaction was detected. However, a genotype x treatment interaction was significant for backfat thickness at both slaughter weights, showing a higher response to rpST in Duroc than in Pietrain and F1. Growth performance was improved more by rpST in F1 and Pietrain than in Duroc, especially at higher weights, but carcass traits were improved more by rpST in Duroc. The response to rpST in lean tissue growth rate from 60 to 100 kg was highest in fatter animals (Duroc, barrows), whereas from 100 to 140 kg, response in lean tissue growth rate to rpST was highest in leaner animals (Pietrain, F1, gilts).     

Evaluation of recombinant porcine somatotropin on growth performance, carcass characteristics, meat quality, and muscle biochemical properties of Belgian Landrace pigs.

The dose related effects of recombinant porcine somatotropin (rpST) on growth, carcass characteristics, muscle properties, and meat quality were investigated in lean Belgian Landrace finishing pigs. Ninety-six pigs (48 barrows and 48 gilts) were injected daily with either vehicle, 1.5, 3, or 6 mg of rpST from 60 to 97.5 kg live weight. Each treatment group consisted of six pens of four pigs each (two of each sex). Pigs were given ad libitum access to a high-protein (20.4% CP) cereal-based diet. Administration of rpST increased (P less than .05) growth rate (16.3 to 25.4%) and improved (P less than .05) feed efficiency (16.9 to 29.4%). Feed consumption was reduced (12%; P less than .05) only in the 6 mg of rpST group. Liver, kidney, and heart weights were increased (P less than .05) in the 3 and 6 mg of rpST groups. Although the Belgian Landrace pigs are bred for superior carcass quality, rpST further improved (P less than .05) carcass composition at all dose levels as evidenced by a reduction (10 to 50%) in a number of subcutaneous fat depth measurements, an increase (10 to 20%) in longissimus muscle area, and an improvement in the lean cut:fat cut ratio. Rate of pH decline in the gluteus and longissimus muscles was similar, but rapid, in all groups (pH after 30 min = 5.74 to 5.94); the ultimate (24 or 72 h) pH was .15 to .2 pH units higher (P less than .05) in the pigs that received the 3 and 6 mg of rpST doses.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of sex and exogenous porcine somatotropin on longissimus muscle fiber characteristics of growing pigs

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.     

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.     

The effects of porcine somatotropin and dietary lysine on growth performance and carcass characteristics of finishing swine

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)     

Effects of exogenous porcine somatotropin (pST) administration on growth performance, carcass traits, and pork meat quality of Meishan, Pietrain, and crossbred gilts

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.     

Relationship of mode of porcine somatotropin administration and dietary fat to the growth performance and carcass characteristics of finishing pigs.

Ninety-six pigs were used to investigate the relationship of diet (control vs fat-supplemented with equal energy:protein ratios), porcine somatotropin (pST) administration (non-treated; 2 mg/d, daily injection; and 2 mg/d, 6-wk implant), and sex (barrows and gilts) to performance and carcass characteristics. Diet and pST treatments were initiated at 87 kg of BW and continued for 38 d. Both the fat-supplemented diet (P less than .001) and pST treatment (P less than .0001) improved feed efficiency. The effects of diet were accounted for by differences in energy density of the diets. Across diets, pST improved gain:feed ratio by 29 and 16% in pigs treated by daily injection and the implant, respectively; the two modes of delivery resulted in different responses (P less than .01). Circulating insulin-like growth factor I (IGF-I) levels, determined from blood samples drawn on d 35, were increased 2.5-fold above those of controls in pigs treated by either daily injection or the implant. However, the elevation of glucose and decrease in blood urea nitrogen concentrations in response to pST were of a greater magnitude in pigs treated by daily injection. Similarly, reductions in backfat thickness and the rate of backfat accretion determined by ultrasound were greater in response to the daily injection of pST than in response to the implant. Lean meat ratio, calculated from measurements with a Fat-O-Meater probe, was increased by 6 and 13% by the implant and daily injection, respectively. It is concluded that although the use of an implant that delivers pST on a continuous basis was as effective as the same dose administered as a bolus injection for increasing IGF-I levels, it was less effective in improving feed efficiency and carcass quality.     

Effect of exogenous porcine somatotropin administration on nitrogen and energy metabolism in three genotypes of pigs

Effects of exogenous administration of porcine recombinant somatotropin (rpST) on protein gain and metabolic rate were measured in three genotypes (castrated males) of pigs (Pietrain, Duroc and a crossbreed between Dutch Yorkshire and Dutch Landrace). Six pigs of each genotype were assigned at approximately 60 kg to receive pST doses of either 0 (C) or 14 mg (T) administered i.m. twice weekly over 10 wk. Pigs were housed in individual metabolism cages at a room temperature of 20 to 22 degrees C and received feed at 2.6 times maintenance. Protein gain (N x 6.25) was measured over the final 6 wk of the 10-wk test period. For 2 wk in the test period (wk 2 and wk 5), six pigs of each treatment x genotype group were placed in a large respiration chamber and energy balances (in protein and fat) and metabolic rate were measured. Rate of weight gain measured over the final 6 wk of the experimental period increased by 105 g/d (13%) with rpST administration (P less than .01). Daily protein gain over 6 wk was increased by 48 g/animal with application of rpST (P less than .001). There was a genotype x treatment interaction (P less than .01) for protein gain. Daily protein gain in Durocs with pST treatment was increased (39%) more than in crossbreds (31%). Daily fat gain was decreased by 42 g/animal (P less than .001) by T. Daily heat production with rpST was increased by 12 kcal/kg.75, which is comparable to a 12% increase in the maintenance energy requirement.     

The effect of human growth hormone-releasing factor or porcine somatotropin on serum hormones and metabolites, growth performance and carcass traits in swine

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)     

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)     

Effect of a hot environment on performance, carcass characteristics, and blood hormones and metabolites of pigs treated with porcine somatotropin.

A study was conducted to compare the effects of a single 100-mg recombinant porcine somatotropin (rpST) implant on performance, carcass characteristics, and blood hormones and metabolites of 40 finishing pigs exposed to either a thermoneutral (TN; 18 to 21 degrees C) or hot environment (H; 27 to 35 degrees C) for 28 or 35 d. Pigs in H gained at a slower rate (P less than .01) than pigs in TN. Control and rpST-treated pigs gained at similar rates in respective environments. The rpST-treated pigs consumed 13% less feed (P less than .01) than the control pigs in both environments, and pigs in H consumed 19% less feed (P less than .01) than pigs in TN. Feed efficiency for rpST-treated pigs was 15% better (P less than .01) than that for control pigs; environment had no effect on feed efficiency. When slaughtered, pigs treated with rpST had less (P less than .01) leaf fat and less (P less than .01) 10th rib backfat than control pigs. Pigs in H had a lower (P less than .01) final BW and less leaf fat and backfat than pigs in TN. The rpST and H had various effects on blood hormones and metabolites. The results demonstrated that the benefits of this form of rpST treatment achieved under TN were also achieved in H with no interactions between the hormone and environment.     

Effects of exogenous somatotropin during early gestation on maternal performance, fetal growth, and compositional traits in pigs

The objective of this study was to determine the effects of maternal treatment with porcine somatotropin (pST) during early gestation on embryonic survival, fetal development, and internal environment for fetal growth. Sixty-two crossbred gilts received daily injections of either 3 mL of a placebo (control, n = 31) or 6 mg of pST (n = 31) from d 10 to 27 of gestation. Representative gilts were slaughtered on d 28, 37, and 62 of gestation. The remaining gilts were allowed to farrow. It was found that embryonic survival was not influenced by pST treatment (P > 0.10). However, pST affected the growth and composition of the maternal (endometrium) and fetal (chorion) parts of the placenta. Thus, endometrial RNA concentration tended to be increased by pST at d 37 (P = 0.15), and it was increased at d 62 (P < 0.05) of gestation, which is indicative of increased capacity for protein synthesis. At birth, placental chorion weight (P < 0.10) and contents of DM and protein (P < 0.05) were increased due to pST treatment, but no effects were detectable up to d 62 of gestation. Maternal pST treatment was effective at increasing nutrient supply to the embryo as suggested from elevated glucose concentrations in amniotic and allantoic fluids (P < 0.05) at d 28 of gestation. With regard to prenatal growth, embryonic DNA concentration was slightly elevated at d 28 (P < 0.10), but pST did not induce any changes in average embryonic, fetal, or neonatal weights. However, within litters, the birth weights of piglets in the 25% lowest weight group (LW) were increased by pST treatment vs control LW pigs (1,241+/-55 vs 1,099+/-59 g, P < 0.10). Thirty-eight neonates from 15 litters divided among the three weight groups were examined for body composition. The weight of the intestinal tract was increased above average after maternal pST treatment (P < 0.01). Additionally, the amounts of tissues such as bone (P = 0.12) and s.c. fat (P = 0.06), and of protein, fat (P = 0.10), and ash (P < 0.05) were increased, whereas the relative body composition remained unchanged by pST (P > 0.10). On average, muscle protein concentration was elevated due to pST (P < 0.01), and, in LW piglets, plasma IGF-I concentration was increased (P < 0.10). The results suggest that maternal somatotropin is a critical factor in early pregnancy capable of influencing placental nutrient transfer and placental growth. It thereby selectively improves the growth conditions for the smaller littermates.     

Growth performance and carcass characteristics of pigs administered recombinant porcine somatotropin during 30 to 110 kilogram live weight

To determine growth performance during and after injection of recombinant porcine somatotropin (rpSt), crossbred Yorkshire gilts and barrows (n = 54/gender, 27 to 42 kg BW) were blocked by BW and gender (n = 3 blocks/gender). Within each block, three pigs/gender were assigned randomly to each of six pens/block. A diet containing 24.8% CP was fed ad libitum. During the live weight period of 30 to 110 kg, pigs either remained as controls (one pen/block) or were injected (i.m.) daily with rpSt (120 micrograms/kg BW) during either 30 to 60, 30 to 100, 30 to 110, 60 to 100 or 60 to 110 kg BW. Thus, three gilts and three barrows in each of three pens received each treatment. Pigs were slaughtered at either 60 kg BW (1 d after rpSt injection) or 110 kg BW (1 d, 10 d or 70 d after rpSt injection). Relative to controls, pigs injected with rpSt exhibited faster and more efficient growth during the injection period (P less than .05) but slower and less efficient growth during 10 d after cessation of injection (P less than .05). Carcasses of pigs slaughtered 1 d or 10 d after rpSt injection were leaner than controls (P less than .05), but among the pigs treated with rpSt, carcasses of pigs withdrawn from rpSt for 10 d contained more fat (P less than .05) and had a lower percentage of muscle (P less than .05) than carcasses of pigs withdrawn from rpSt for 1 d. Growth and carcass measurements were similar (P greater than .05) between controls and pigs killed 70 d after rpSt injection.(ABSTRACT TRUNCATED AT 250 WORDS)     

Interaction of dietary protein content and exogenous porcine growth hormone administration on protein and lipid accretion rates in growing pigs

Sixty-six intact male pigs were used to investigate the relationships between exogenous porcine growth (pGH) administration (0, excipient-treated, and .09 mg recombinant pGH.kg-1.d-1) and dietary protein content (8.3, 11.4, 14.5, 17.6, 20.7 and 23.8%) on protein and lipid accretion rates over the live weight range of 30 to 60 kg. Feed intakes were restricted (1.84 kg.pig-1.d-1) and pGH was administered daily by i.m. injection. Rate of protein deposition increased with increasing dietary protein up to 17.6 and 20.7%, respectively, for control and pGH-treated pigs; both growth and protein deposition were enhanced by pGH on the four higher protein diets but remained unaffected by pGH administration to pigs given the two lowest protein diets. Plasma IGF-I concentration was elevated by pGH administration in pigs given the four higher protein diets but unaffected by pGH with the two lowest protein diets. Rate of fat deposition was depressed on all dietary protein treatments by pGH administration; carcass fat content of control and pGH-treated pigs declined with each increase in dietary protein up to 17.6 and 23.8%, respectively. The results demonstrate that pGH acts independently on protein and lipid metabolism.     

Effects of increasing crude glycerol and dried distillers grains with solubles on growth performance, carcass characteristics, and carcass fat quality of finishing pigs

This study was conducted to determine the effects of dietary crude glycerol and dried distillers grains with solubles (DDGS) on growing-finishing pig performance, carcass characteristics, and carcass fat quality. We hypothesized that because dietary crude glycerol has been observed to increase carcass SFA, it might ameliorate the negative effects of DDGS on fat quality. The 97-d study was conducted at a commercial swine research facility in southwestern Minnesota with 1,160 barrows (initial BW = 31.0 ± 1.1 kg). Pigs were blocked by initial BW, and pens were randomly allotted to 1 of 6 dietary treatments with 7 replications per treatment. Treatments were arranged in a 2 × 3 factorial with main effects of crude glycerol (0, 2.5, or 5%) and DDGS (0 or 20%). All corn-soybean meal-based diets contained 3% added fat (choice white grease). There were no glycerol × DDGS interactions for any response criteria evaluated. Increasing dietary glycerol did not affect finishing pig growth performance. Adding 20% DDGS to the diet did not affect ADG; however, finishing pigs fed diets with added DDGS had greater (2.47 vs. 2.41 kg/d; P = 0.02) ADFI and poorer (0.39 vs. 0.40; P = 0.01) G:F than pigs not fed DDGS. Feeding increasing dietary glycerol or 20% DDGS did not affect carcass characteristics. For carcass fat quality, feeding 20% DDGS resulted in decreased (P < 0.01) palmitic and oleic acids, total SFA and total MUFA, and increased (P < 0.01) linoleic, total PUFA, total unsaturated fatty acids, and iodine value in jowl fat, belly fat, and backfat. Increasing dietary crude glycerol increased myristic acid (linear, P < 0.05) and MUFA (quadratic, P < 0.05) in jowl fat and increased (quadratic, P < 0.05) oleic acid and MUFA in backfat. In conclusion, feeding 20% DDGS to finishing pigs increased ADFI, reduced G:F, and increased carcass fat iodine value, whereas feeding crude glycerol did not influence growth performance, carcass characteristics, and had a minor influence on fatty acids of carcass fat. Both of these biofuel coproducts can be used in combination without affecting finishing pig performance or carcass traits; however, feeding crude glycerol did not fully mitigate the increased unsaturation of carcass fat observed when feeding DDGS.     

饲料中添加紫花苜蓿多糖对育肥猪生长性能和胴体品质的影响

为研究紫花苜蓿多糖对育肥猪生长性能及胴体品质的影响,选择体重相近的健康三元杂交育肥猪180头,随机分成3组,每个组3个重复,每个重复20头,1组饲喂基础日粮为对照组,2、3组分别在基础日粮中添加5.0%、10.0%紫花苜蓿多糖,预试验10 d,试验期60 d。在试验1 d和60 d测定生长性能指标,试验结束测定胴体品质。结果表明:(1)试验2、3组试验末重和平均日增重分别较对照组提高5.8%、6.2%、14.0%、14.9%(P <0.05),试验2、3组料重比分别较对照组降低4.6%、5.0%(P <0.05)。(2)试验2、3组屠宰率和瘦肉率分别较对照组提高4.2%、4.0%、5.8%、6.9%(P <0.05);试验2、3组胴体率均高于对照组(P> 0.05),试验2、3组背膘厚和眼肌面积分别较对照组降低7.8%、10.0%、8.9%、8.7%(P <0.05)。(3)试验2、3组肉质评价指标大理石评分、肉色、剪切力、p H24 h较对照组相比,均差异性不显著(P> 0.05)。综述所述,日粮中10.0%紫花苜蓿多糖可以提高育肥猪的生长性能和胴体品质。