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.     

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.     

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.     

Genotype and sex effects on the relationship between energy intake and protein deposition in growing pigs

Seventy-two crossbred (Large White X Landrace) pigs were used in a 3 X 7 factorial experiment to investigate the response of two strains of boars (strains A and B) and of castrated male pigs (strain B) to seven levels of intake of a single diet (ranging from 5.3 Mcal digestible energy [DE]/d to ad libitum) between 45 and 90 kg live weight. All aspects of growth performance and body composition were affected to different degrees by both strain and sex. At all levels of energy intake strain A boars grew faster, had a lower feed to gain ratio and contained less fat and more water in the empty body than strain B boars, which in turn exhibited faster live weight gain and more efficient and leaner growth than castrated males. The magnitude of the differences in growth performance between strain A and strain B boars and castrates increased with increased energy intake above 7.88 Mcal DE/d, and these differences were associated with concomitant strain differences in their respective capacity for protein growth and in the relationship between energy intake and protein deposition. For strain A boars the rate of protein deposition increased linearly from 92 to 188 g/d with increased energy intake from 5.3 Mcal DE/d to ad libitum. For strain B boars and castrates the rate of protein deposition increased linearly with increased energy intake up to 7.88 Mcal DE/d, but thereafter it remained constant at 128 and 85 g/d, respectively. For castrates protein deposition was depressed (P less than .01) when the diet was offered ad libitum. Strain A boars had a higher energy requirement for maintenance (3.55 Mcal DE/d) than strain B boars (2.77 Mcal DE/d) or castrates (2.60 Mcal DE/d). Strain A boars also contained less protein and more water in the fat free empty body than the other two pig types.     

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.     

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.     

The growth performance of the progeny of two swine sire lines reared under different floor space allowances

A total of 736 pigs was used in a study with a 2 x 2 x 2 factorial arrangement to investigate the effects of and interactions between sire line (Line A vs. B), floor space (unrestricted vs. restricted), and gender (barrow vs. gilt) on growth performance, BW, and protein and estimated lipid accretion curves from 40 to 120 kg of BW. Pigs were by eight Line-A and nine Line-B sires mated with PIC C22 dams. Line A was of Pietrain ancestry and Line B was a synthetic line. The unrestricted floor space treatment consisted of small groups (four pigs) with 0.93 m2/pig of floor space for the entire grow-finish period. Pigs in the restricted floor space were in larger groups (12 pigs) with 0.37 and 0.56 m2/pig of floor space for the grower and finisher phases, respectively. Pigs were given ad libitum access to a three-phase dietary program, and one and three nipple waterers were available in the groups of 4 and 12 pigs, respectively. No sire line x floor space interactions were found for any of the traits measured. Line A pigs grew more slowly (50 g/d, P < 0.05), took longer (4.1 d, P < 0.05) to reach harvest weight (120.3 kg), and had similar feed intakes, but a lower gain:feed ratio (2.8%, P < 0.05) than Line B pigs. Line A pigs had greater longissimus muscle depth (P < 0.05) and estimated protein accretion rate (P < 0.05) than Line B pigs, but Line A and Line B pigs had a similar estimated percentage of lipid-free soft tissue. Pigs reared in the restricted floor space grew more slowly (105 g/d, P < 0.05) and consumed less feed (280 g/d, P < 0.05) but had a similar (P > 0.05) gain:feed ratio to pigs reared in the unrestricted floor space. Pigs reared in the unrestricted floor space had greater (P < 0.05) predicted protein and lipid accretion rates throughout the growth period than pigs reared in the restricted floor space. Differences between genders for growth traits and carcass measurements were in agreement with previous research. The differences in growth performance, carcass measures, and compositional growth curves between these two sire lines were similar in the two floor spaces.     

持续高温对不同性别北京油鸡生长性能、肉质性状及脂肪沉积的影响

本研究旨在考察持续高温对不同性别北京油鸡生长性能、肉质性状及脂肪沉积的影响.选择健康、体况相近的49日龄北京油鸡公母各72只(公鸡平均体质量(608.58±13.07)g;母鸡平均体质量(518.50±8.33)g)随机分在2个处理中:(1)高温组,(35±0.37)℃;(2)适温组,(25±0.38)℃,分别在2个人工环境气候舱中饲养.每个处理设6个重复,每个重复6只鸡.试验持续23 d.测定试验第1～11、12～22和1～22天的生产性能指标及第12和23天时的胴体性状、肉质性状及脂肪沉积率.结果表明;1)热暴露1～11 d,公母鸡的日增体质量都显著降低(P＜0.01),料重比无明显变化(P＞0.05).热暴露12～22 d,公鸡的日增体质量显著降低(P＜0.01),而母鸡无明显变化(P＞0.05),同时,公鸡的料重比显著提高(P＜0.01);2)与适温组相比,高温组各性别北京油鸡的肉质性状均无明显变化(P＞0.05);3)对公鸡而言,热暴露12 d时腹脂、肌间脂肪和皮下脂肪沉积率及胴体率、腿比率与适温组相比均无显著差异(P＞0.05).热暴露23 d时各部位脂肪沉积率均显著降低(P＜0.01),而胴体率和腿比率显著提高(P＜0.05);对母鸡而言,热暴露12d时腹脂、肌间脂肪沉积率显著降低(P＜0.05),热暴露23 d时皮下脂肪率显著降低(P＜0.05),腹脂、肌间脂肪沉积率及胴体率、腿比率与适温组相比均无显著差异(P＞0.05).结果提示,热暴露12 d,各性别油鸡的日增体质量均显著降低,随着热暴露进一步延续,公鸡日增体质量的降低幅度加大,而母鸡的已无明显变化;随着热暴露时间的延长,公鸡的脂肪沉积逐渐下降,而母鸡的脂肪沉积下降程度有所缓解.     

The relationship of average backfat thickness of feedlot steers to performance and relative efficiency of fat and protein retention

Selection for growth and improved carcass merit has resulted in cattle that are variable in composition of gain during the finishing phase. This study assessed the relative performance among cattle with different levels of initial backfat thickness. It also exploited the ability to track carcass composition in the live animal with ultrasound estimates of backfat and marbling. A procedure was developed to partition and estimate relative efficiency of fat and protein gain. The trial periods were the last 43 or 50 d before slaughter and included 10 pens (average of 27 animals per pen) that ranged in average backfat thickness from 6.3 to 13.1 mm. There was no correlation (r2 = 0.0026) between average backfat thickness and G:F (g/kg of DMI). Correlations between average backfat thickness and ADG or DMI were also nearly zero (r2 = 0.0007 and 0.0042, respectively). Fat deposition from NEg was 3.98 times more efficient than protein deposition. Carcass backfat thickness was a poor predictor of carcass marbling score (r2 = 0.083), even though backfat thickness was an important predictor of the percentage of empty body fat (r2 = 0.807). The results indicate that a measure of backfat thickness on the live animal during the finishing phase is not an effective predictor of future feed efficiency. They also confirm that protein accretion is energetically expensive, and that using a single coefficient for predicting gain from NEg is valid regardless of whether gain is predominantly muscle or fat. These data document that there is little relationship between body composition and marbling score, which is contrary to models that assume a USDA quality grade target at a specified percent fat end point.     

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.     

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.     

Danish investigations concerning body composition of pigs in relation to nutrition,sex and slaughter weight

Several Danish investigations were carried out in order to elucidate the influence of nutrition, sex and slaughter weight on the body composition in pigs. In this paper we discuss whether selection of breeding animals should be based mainly on: (1) per cent meat in the carcass, (2) a combination of per cent meat, daily gain and feed consumption per kg live weight gain, or maybe better, (3) a combination of per cent meat and feed consumption per kg meat produced.Investigations comprising five different energy and protein levels and 1100 pigs slaughtered at live weights varying from 80 to 120 kg showed that both feeding intensity and slaughter weight influenced the carcass composition. Increasing feeding intensity and increasing slaughter weight caused a deterioration in the ratio between meat and subcutaneous fat. The feeding intensity had only little influence on kg meat produced whereas increasing feeding intensity caused an increase in kg subcutaneous fat produced.The females contained more meat than did the male castrates. Besides, the deterioration in carcass composition due to increasing slaughter weight and feeding intensity were lower in the females than in the male castrates. Daily gain increased with increasing feeding intensity. The investigations indicate maximal protein synthesis to take place within the live weight area of 90–100 kg.High correlations were found between the chemical composition of the different anatomical fractions in 90-kg pigs. The empty pigs (live weight minus the content of the digestive tract) weighed on average 80.8 kg, of which 42.0% was dry matter. The dry matter contained 41.1% protein, 51.1% chemical fat, 7.7% ash and 7080 kcal per kg. The meat fraction contained 55% of the protein, 30% of the chemical fat and 38% of the energy in the empty pigs.     

Influence of sex and castration of females on growth performance and carcass and meat quality of heavy pigs destined for the dry-cured industry

Crossbred pigs (n = 240) from Pietrain x Large White sires mated to Landrace x Large White dams, with an average age of 100 d (60.5 +/- 2.3 kg of BW), were used to investigate the effects of sex and slaughter weight (SW) on growth performance and on carcass and meat quality characteristics. There were 6 treatments arranged factorially, with 3 classes (intact females, IF; castrated females, CF; and castrated males, CM) and 2 slaughter weights (114 and 122 kg of BW). Each of the 6 combinations of treatments was replicated 4 times, and the experimental unit was a pen with 10 pigs. Castrated males and CF ate more feed, grew faster, and had more carcass backfat depth and fat thickness at the gluteus medius muscle but lower loin yield than IF (P < 0.05). In addition, CF and CM had more intramuscular fat (P < 0.05) and less linoleic acid content in the subcutaneous fat (P < 0.01) than IF. Pigs slaughtered at 122 kg of BW had lower ADG (P < 0.05), decreased G:F (P < 0.05), and more gluteus medius fat than pigs slaughtered at 114 kg of BW (P < 0.05). It was concluded that CF and CM had similar productive performance and meat quality characteristics when slaughtered at the same age, and that castration of females improved ADG and increased weight and fat content of primal cuts with respect to IF. Therefore, castration of females is recommended in pigs destined for the dry-cured industry because of the beneficial effects on quality of the primal cuts.     

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.     

Effect of the beta-adrenergic agonist cimaterol (CL 263,780) on the growth and carcass characteristics of finishing swine

A randomized complete-block design was used to evaluate the effects of the beta-adrenergic agonist, cimaterol (CL 263,780), on growth rate, feed efficiency and carcass composition of finishing swine. The drug was fed at four levels (0, .25, .5 and 1.0 ppm) to a total of 240 pigs from 64.5 to 103.7 kg live weight. Growth rate and feed efficiency were measured during the 7-wk feeding trial. Feeding cimaterol depressed feed intake, improved feed efficiency and did not alter rate of gain. Carcass evaluation showed that pigs continuously fed cimaterol had 13.2, 9.3 and 9.2% less fat measured at the 10th rib, P2 and average backfat (BF) locations, respectively, compared with controls. Cimaterol-fed pigs had increased loin eye areas (10.9%), and increased semitendinosus (11.8%) and biceps femoris (8.9%) weights compared with controls. The semitendinosus muscles of the cimaterol-fed pigs had less fat and the femur bones were shorter and lighter weight than controls. There were no detected differences in structural soundness of the live pigs, but postmortem evaluation of the hooves indicated that pigs fed 1.0 ppm cimaterol had a higher incidence of hoof lesions. Pigs withdrawn from cimaterol for 7 d were comparable in performance and carcass characteristics with those continuously fed the drug except that carcass fat measurements had generally returned to control values. The data indicate that cimaterol improved the feed efficiency of finishing pigs and increased the lean:fat ratio of their carcasses. Withdrawal of cimaterol caused compensatory fat deposition.     

Postweaning growth, feed efficiency and chemical composition of sheep as affected by prenatal and postnatal testosterone

Data were collected from intact males, castrated males and ewe lambs to investigate the effect of presence or absence of testosterone prenatally and during the postweaning period on postweaning growth, feed intake and carcass chemical composition. Half the lambs from each sex were the progeny of dams that had received five injections of testosterone cyprionate from d 32 through d 87 of gestation. Linear contrasts were used to detect differences. Postweaning daily gain of intact males was greater (P less than .01) than that of male castrates. Ewe lambs from treated dams had approximately 12% greater rate of growth (P less than .04) than ewe lambs from control dams. Ewe lambs from dams that had been treated were 28% more efficient (P less than .01) in the conversion of food to weight than those from untreated dams. Ewe lambs from treated dams had heavier livers (P less than .07). Carcass protein for intact males was greater (P less than .11) than for castrates, and extractable fat was less (P less than .05). Masculinization of growth characteristics of ewe lambs affected the quantity of carcass fat relative to control ewes (7.59 vs 8.92 kg). These ewe lambs also had more water in the carcass than did the control ewes (13.93 vs 12.29 kg). Administration of exogenous testosterone to pregnant ewes over an interval of time approximating time of sexual differentiation in the fetus enhances postweaning growth rate, feed conversion efficiency and chemical composition of genetic females.     

Influence of genotype and sex on the response of growing pigs to recombinant porcine somatotropin.

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

长白×北京黑F_1代猪适宜粗蛋白与赖氨酸、粗蛋白比的研究

用2个蛋白水平和2个赖蛋比值作2×2析因设计,将32头始重25公斤的长白×北黑F_1代猪随机分成4组,每组8头,进行饲养试验;将16头阉公猪也分为4组,每组4头,进行N—平衡试验,研究了以玉米—豆饼为基础的饲粮蛋白质和赖蛋比水平对猪在20—60公斤和60—90公斤两个体重阶段的生产性能,氮沉积和90公斤时胴体品质的影响。粗蛋白由16—14％降至14—12％时极显著降低了胴体瘦肉率、背最长肌蛋白含量和日氮沉积量,提高了背膘厚,对增重和饲料效率等无明显影响。赖蛋比4.5—4.5％提高到5.0—4.5％,除降低 日采食量、增重和屠宰率(P<0.05)外,对其余指标均无影响。本试验结果表明:长×北F_1代瘦肉猪饲粮适宜粗蛋白为16—14％,赖蛋比为4.5—4.5％。     

Impact of betaine on pig finishing performance and carcass composition

Two experiments were conducted to evaluate the effect of betaine supplementation of finishing diets on growth performance and carcass characteristics of swine. Experiment 1 included 288 pigs in a 2 x 2 x 3 factorial arrangement of treatments consisting of barrows and gilts of two genetic populations fed diets with 1.25 g/kg supplemental betaine from either 83 or 104 kg to 116 kg and control pigs fed betaine-devoid diets. Pigs were housed three pigs per pen with eight replicate pens per treatment. Diets were corn-soybean meal-based with 300 ppm added choline. Genetic populations differed (P < 0.05) in fat depth (2.24 vs 2.93 cm) and longissimus muscle depth (53.8 vs 49.1 mm) at 116 kg. Betaine reduced feed intake (P < 0.05); however, real-time ultrasound measurements were not affected. In Exp. 2, 400 pigs were used in a 2 x 2 x 2 factorial arrangement of treatments to evaluate the effect of sex (barrow or gilts), betaine (0 or 1 g/kg of diet), and crude protein (CP) (0.70% lysine = 12.7% CP or 0.85% lysine = 15.0% CP) when fed from 60 to 110 kg live weight. Pigs had been assigned to either a high- or low-protein feeding regimen at an average initial weight of 11.3 kg and were maintained on their respective protein levels throughout the experiment. For a 56-d period from 61.7 kg to 113.6 kg, pigs were fed diets with 300 ppm added choline. Within each protein level, pigs were randomly assigned to diets containing 0 or 1 g/kg betaine. Pigs were group-housed (four to five pigs per pen). Pig weight and feed intake were recorded every 28 d. Real-time ultrasound measurements were recorded initially and at d 28 on 64 pigs, and on all pigs prior to slaughter. Growth rate was fastest and feed intake greatest for barrows (P < 0.05) and for pigs receiving 12.7% crude protein. A crude protein x betaine interaction (P < 0.05) was observed from d 28 to 56 with pigs fed the 15% CP diet growing fastest when supplemented with 1 g/kg betaine, and pigs receiving the 12.7% CP diet growing fastest when the diets contained 0 g/kg betaine. Gilts more efficiently (P < 0.05) converted feed into body weight gain, as did pigs receiving the 12.7% CP diet (P < 0.05). Longissimus muscle area and fat measurements were unaffected by betaine or dietary protein on d 28. However, by d 56 betaine reduced average fat depth in barrows (P < 0.05; 3.21 vs 3.40 cm), but not in gilts. Betaine may be more effective at altering body composition in barrows than in gilts.     

Development of a model to describe the compositional growth and dietary lysine requirements of pigs fed ractopamine

The objective of this research was to use recent ractopamine research data to develop an updated mathematical model to describe the daily compositional growth of pigs fed ractopamine. Mean increases of 18.2, 23.1, and 25.0% for daily protein accretion were assumed for 5, 10, and 20 ppm of ractopamine for an overall gain of 40 kg of BW gain during the feeding period. The relative effect of ractopamine described the rapid increase and subsequent decrease in the effect of ractopamine as a function of BW gain or days on test and ractopamine concentration (RC, ppm). The reduction in ME intake produced by ractopamine was described as 0.036 x (RC/20)(0.7) multiplied by the ME intake for the first 20 kg of BW gain, and then increasing to 0.078 x (RC/20)(0.7) at 40 kg of BW gain feeding period. The ratio of fat-free muscle gain to protein accretion increased by 14 to 16% with the feeding of ractopamine, depending on the dietary lysine/essential AA levels. The ratio of carcass fat gain to empty body lipid gain was increased when lysine and essential AA requirements were met. Daily protein accretion and fat-free lean growth were described as functions of dietary lysine/essential AA intakes. The percentage of lysine in protein accretion increased with the feeding of ractopamine from 6.80 to 7.15%, depending on ractopamine concentration. Equations predicting carcass measurements, such as fat and longissimus muscle depths from carcass weight and composition, were modified to incorporate prediction biases produced by ractopamine. For the four concentrations of ractopamine (0, 5, 10, and 20 ppm, respectively) during a 78 to 110 kg of BW feeding period, the model predicted performance levels for ADG (1.03, 1.15, 1.16, and 1.16 kg/d), gain:feed (kg of ADG/kg of ADFI; 0.360, 0.401, 0.412, and 0.425), dressing percentage (75.1, 76.0, 76.3, and 76.4), percentage fat-free lean (48.7, 51.0, 51.5, and 52.2), longissimus muscle area (38.8,41.8,42.5, and 43.5 cm2), 10th-rib fat depth (22.1, 19.8, 19.3, and 18.7 mm), and fat-free lean gain (321, 446, 467, and 495 g/d), comparable to recent research data. The model allows the effect of ractopamine to be added to farm specific pig growth curves. It can be used to evaluate ways to optimize the use of ractopamine, including duration of ractopamine feeding, concentration of ractopamine, and dietary lysine concentration.