Effects Of Porcine Somatotropin Research Articles

Effect of porcine somatotropin on metabolism, testicular size and sperm characteristics in young boars

ABSTRACT The aim of this study was to evaluate the effect of pST injections on metabolism, testicular size, and sperm characteristics in young boars. Sixty 22-day old piglets were divided into two groups: pST (n=30) and Control (n=30). The pST group was submitted to pST injections (90µg/kg body weight) every three days up to 330 days of age. Blood collections were performed weekly. Testicular weight was measures at 22, 82, 142, 202 and 365 days of age. Libido and fresh semen characteristics were evaluated between 150 and 210 days of age. Semen characteristics were also evaluated during a 72h storage period (15ºC). Testosterone, albumin, and phosphorus blood concentrations were higher in the pST group (P<0.05). The pST group had a higher IGF-I concentration in seminal plasma (P=0.05) and higher testicular weight (P<0.001) compared to the Control group. The pST group had higher ejaculate volume (P<0.001), total sperm count (P=0.047) and number of inseminating doses/ejaculate (P=0.047). During the 72h storage period, the pST group had a lower number of morphological alterations (P<0.001) compared to the Control group. In sum, pST injection in young boars increased testosterone concentration, testicular size, and sperm quality.

Effect of porcine somatotropin on metabolism and testicular characteristics of prepubertal pigs

Effect of porcine somatotropin on metabolism and testicular characteristics of prepubertal pigs

Effect of porcine somatotropin on metabolism and testicular characteristics of prepubertal pigs

The effect of pST on the testicular characteristics and metabolic parameters of prepubertal pigs was evaluated. Experiment 1 aimed to determine the interval between applications of pST based on the concentrations of circulating IGF-I. Experiment 2 aimed to evaluate the effect of pST on metabolic parameters, testicular characteristics, and expression of GHR, IGF-I and PCNA. In Experiment 1 twelve piglets with 30 days of age were used. The pST Group (n=6) was submitted to one i.m. injection of pST and the Control Group (n=6) to one placebo injection. Blood collections were performed until d 7 post pST application to determine IGF-I concentration and metabolic profile. In Experiment 2 twelve piglets with 22 days of age were used. The pST Group was submitted to pST injections every three days, and the Control Group received placebo doses during 30 days. Blood collections were performed every 3 days. Samples of liver and testicular tissue were collected to determine gene expression and testicular characteristics. In Experiment 1 IGF-I concentration was higher for the pST Group (P=0.02). In Experiment 2 the pST Group had higher body and testicular weight (P=0.06) and increased gene expression of PCNA in testes (P<0.05). However, a reduction in the number of seminiferous tubules, and Sertoli cells, and in GHR expression (P<0.05) was observed. Thus, pST administration increased body and testis development in prepubertal pigs, however it reduced the density of seminiferous tubules and Sertoli cells.

Effect of Porcine Somatotropin and Insulin on Prenatal Survival and Uteroplacental and Umbilical Cord Development in Gestating Gilts

Effect of Porcine Somatotropin and Insulin on Prenatal Survival and Uteroplacental and Umbilical Cord Development in Gestating Gilts

The effects of porcine somatotropin administration and gender on cooking properties and palatability attributes of pork muscle

Loin roasts and ham steaks from 120 Yorkshire pigs (60 barrows and 60 gilts) were utilized to evaluate the effects of porcine somatotropin (PST) treatment and gender on cooking properties and palatability attributes. Within each gender, pigs were randomly allocated to the following three treatments: 1) control, 2) prolonged-release PST implants (2 mg d−1), or 3) daily subcutaneous PST injections (2 mg d−1). All animals received a 17% crude protein diet, ad libitum. Animals received PST treatments within a body weight range of 70 ± 5 kg to 96 ± 5 kg. All animals were slaughtered and processed using simulated commercial procedures. Longissimus lumborum (loin) roasts (lumbar) and cured and smoked semimembranosus (SM) steaks were roasted to 75 and 60 °C, respectively, in a 177 °C oven, sub-sampled, and evaluated by an eight-member sensory panel. No differences in cooking properties or palatability attributable to gender were observed (P &gt; 0.05). However, cured and smoked SM steaks from pigs receiving daily PST injections were more tender both initially and overall (P &lt; 0.05) than their counterparts from control pigs. In addition, cured and smoked SM steaks from pigs receiving daily PST injections had less perceived connective tissue (P &lt; 0.05) than their counterparts from control pigs and pigs receiving prolonged-release PST implants. The cooked loins from pigs receiving prolonged-release PST implants were perceived to contain less connective tissue than their counterparts from control pigs and pigs receiving daily PST injections (P &lt; 0.05), but cooked loins from pigs receiving prolonged-release PST implants had less-desirable flavour (P &lt; 0.05) than their counterparts from pigs receiving daily PST injections. It should be noted, however, only the tenderness differences observed in the cured and smoked SM were of sufficient magnitude to be of practical importance. Consequently, it would appear PST treatments, particularly daily injections, can be utilized to achieve previously reported, potential production and carcass composition advantages, while possibly improving the eating quality of some pork products. Key words: Pork, somatotropin, PST, gender, cooking properties, palatability attributes

Effects of porcine somatotropin on the chemical body composition and fat quality in growing-finishing pigs.

Seventy eight growing-finishing pigs (male castrates and females) of the cross-breed Pietrain x (Large White x German Landrace) were used to investigate the effects of pST treatment on the chemical composition of the body, the growth of adipocytes, and the fatty acid profile of the backfat. Intramuscular injections (1 or 3 mg pST) were administered daily from an average weight of 65 kg up to slaughter. After pST treatment significant changes in all studied characteristics were observed in barrows, whereas the females exhibited very small responses. The pST caused an increase of water and protein contents and a simultaneous decrease of lipid content especially in body parts rich in fat. Furthermore, the proportion of unsaturated fatty acids increased and the fat cell diameter decreased in the backfat.

The effects of porcine somatotropin, gender and porcine stress syndrome on growth, carcass composition and pork quality

Lacombe breed pigs (72 gilts, 72 barrows) of three genotypes with respect to the porcine stress syndrome (normal, heterozygous, or homozygous for the halothane gene), were treated from 57 to 106 kg body weight with daily injections of 0.9% saline containing 0 or 3 mg of recombinant porcine somatotropin (pST) in a randomized block design. Pigs receiving pST had lower average daily feed intakes (ADF), greater average daily gains (ADG) and lower feed conversion efficiencies (FCE). Gilts relative to barrows had lower ADG, ADF and higher FCE. Gilts versus barrows and pigs treated with pST had reduced fat depths and greater loin depths at the 10th rib. Pigs homozygous for the halothane gene had reduced loin lean structure and color scores, greater light reflectance (L*), and lower soluble protein contents as expected, and these genotypic effects did not interact with pST treatment. Sex by pST treatment interactions (P &lt; 0.05) were found for loin depth, moisture content, color score and L* values indicating barrows respond more favorably to pST treatment than gilts. Generally, pST treatment, gilts relative to barrows, and possession of the halothane gene increased carcass lean and reduced subcutaneous fat levels. Sex by pST treatment interactions were found for picnic lean (lower shoulder; P &lt; 0.05), ham lean (P &lt; 0.05), and total carcass lean (P = 0.09) further supporting the theory that barrows benefit more than gilts to pST treatment. No significant interactions were found between genotype and pST treatment for any qualitative muscle traits. Thus, pST treatment had no direct effect on meat quality and was not found to interact with the halothane gene. However, pST interactions with sex indicated barrows respond quantitatively and qualitatively more favorably than gilts to pST treatment. Key words: Somatotropin, porcine somatotropin, pork, porcine stress syndrome, stress, pigs, growth

Effects of porcine somatotropin on circulating testosterone concentrations in boars and mechanism of action.

Four experiments were conducted to elucidate the effects of porcine somatotropin (pST, growth hormone) on circulating testosterone concentrations in boars. In Exp. 1, jugular-cannulated obese boars were administered 4 mg recombinant (r) pST/d for 24 d before collection of samples at 15-min intervals over 6 h for measurement of pST, testosterone, and LH. Somatotropin treatment decreased plasma concentrations of testosterone and LH (P < .05). In Exp. 2, White composite boars were administered rpST with implants (4 mg/d) for 10 to 28, 16 to 28, or 22 to 28 wk of age. Reductions in testosterone concentrations were proportional to the length of time rpST was administered; boars treated for 18 wk had the lowest testosterone concentrations. Concentrations of LH declined throughout the study in rpST-implanted boars but remained static in untreated, control boars. In vitro production of testosterone and dehydroepiandrosterone/dehydroepiandrosterone sulfate was unaffected by rpST treatment, and hCG stimulation of in vitro androgen secretion was similar in rpST and control treatments. In Exp. 3, i.v. injection of pituitary pST (USDA-B1; 5 micrograms/kg BW) into jugular-cannulated White composite and Meishan boars resulted in an acute increase in circulating LH followed by an increase in testosterone concentrations, which then declined to below preinjection levels at 6 to 7 h after pST injection. Multiple injections, two or four per day, of 5 micrograms pST/kg BW resulted in decreased testosterone concentrations in White composite boars, whereas in Meishan boars testosterone concentrations were unaffected (Exp. 4). Concentrations of LH were not different from control values in either breed, but in both breeds, four injections of pST per day produced lower LH concentrations than did two injections per day (P < .01). Depression of circulating concentrations of androgens in boars requires extended periods of pST treatment.

Thymic, gonadal, and endocrine relationships in gilts and boars administered porcine somatotropin.

We hypothesized that much of the positive effect of porcine somatotropin (pST) on the immune system would be offset by the pST/IGF stimulation of gonadal function and that there would be negative effects on thymic weight and function from increased androgens in males. Male and female hogs (78 boars, 90 gilts) representing three genetic lines (lean, obese, and crossbred meat type) received 0, 2, or 4 mg of recombinant pST/d via implant for 42 d. Blood samples were collected on 0, 7, 14, 28, and 42 d of the trial for changes in pST, IGF-I, IGF-II, thymosin beta 4, dehydroepiandrosterone/dehydroepiandrosterone sulfate (DHEA/DHEASO4), and testosterone concentrations. Thymic, splenic, gonadal, and adrenal weights were collected at slaughter (d 42). Thymic weights increased with dose of pST in both sexes (P < .01), but splenic weights were unaltered. Adrenal weights increased with dose of pST (P < .01), but gonadal weights showed no response to pST in either sex or any line. Overall, concentrations of pST, IGF, and thymosin beta 4 increased with dose of pST. Serum testosterone concentrations in boars declined with dose of pST in lean and obese lines, and DHEA/ DHEASO4 declined in all lines with pST treatment. Testicular testosterone concentrations were not different among lines or doses of pST, indicating no stimulatory effect of increased pST/IGF-I on Leydig cell function. Although pST and its effects through increased circulating IGF are thought to be overall stimulants of growth and protein accretion, the actions on the tissues of the immune system (thymus/spleen) and steroidogenic tissues (adrenal/gonadal) can be selective. Increases in thymic weights and thymosin beta 4 concentrations from pST treatment in boars were partially due to the pST-induced decline in circulatory androgens, and the responses found in this in vivo model do not support pST/IGF effects documented in in vitro systems on Leydig cell function.

Effect of Porcine Somatotropin (pST) on Body Composition, Meat Quality and Characteristics of Backfat in Genetically Different Pigs

AbstractThe influence of genotype, pST and stress reactivity on carcass composition, meat and fat quality was investigated in 57 growingfinishing pigs. Pietrain pigs contained more meat and less fat in carcass in comparison to Schwerfurter breed. Exogenous pST improved the carcass composition with regard to leaness. The inhibitory effect of pST on fat synthesis caused a reduced chemical fat in adipose tissue, reduced size and number of fat cells and an increase of relative content of polyunsaturated fatty acids. Halothane reactivity mainly influenced the composition of carcass. Stress‐positive pigs were leaner than H'pigs. The factors pST, breed and halothane reactivity slightly affected the meat quality.

Effect of porcine somatotropin (pST) treatment and withdrawal on performance and adipose tissue cellularity in finishing swine.

A 10-wk trial was conducted with 60 barrows and 60 gilts (initial weight = 47 kg) to investigate the effect of pST treatment (3 mg/d) for wk 0 to 5, 5 to 10, or 0 to 10 on performance, carcass traits, and adipose tissue cellularity of finishing hogs. The primary objective of the study was to determine the effect of 5 wk of pST treatment followed by 5 wk of withdrawal on performance and carcass traits relative to a control or to pigs treated for the entire period. After 5 wk, pST-treated pigs exhibited improved (P < .001) gain (11%) and efficiency (22%) and decreased (P < .001) feed intake (-22%) and 10th rib backfat accretion (-93%, P < .001). There was an increase in adipose cell number/gram of tissue (control, 2.57 vs pST, 3.36 x 10(6)/g; P < .005) and a decrease in cell diameter (control, 72.4 vs pST, 67.2 microns; P < .005). Backfat thickness and cell diameter increased in control pigs from wk 5 to 10. During the last 5-wk period, pST-treated animals continued to exhibit improved performance and maintained adipose cell size distribution and number similar to the pST-treated pigs at wk 5. Pigs treated for the first 5 wk and withdrawn from treatment for the second 5 wk had decreased efficiency (-12%, P < .05) and a twofold increase in backfat accretion (P < .001) relative to control. The increase in backfat thickness was accompanied by an increase in adipocyte diameter, indicative of lipid filling. Most of the benefits of pST observed during the first 5 wk were lost during the withdrawal period. Reductions in carcass fat in response to pST treatment are at least partially accounted for by inhibition of lipid filling in adipose tissue, an effect that is reversed upon cessation of treatment.

Effects of porcine somatotropin on growth and carcass composition of Meishan and Yorkshire barrows.

Effects of porcine somatotropin (pST) on growth and carcass characteristics of Meishan (Ms) and Yorkshire (Y) barrows given 3 mg of pST or saline daily were determined for two end points. First, 26 Ms and 26 Y barrows were treated from 119 d of age until the Y barrows reached 108 kg. Second, another 18 Ms barrows were treated to 108 kg BW. Age- and weight-matched treatments were analyzed. Results for both groups indicated pST effects (P < .05) for feed conversion (+) and intake (-), dressing percentage (-), percentage of carcass fat (-) and protein and water (+), leaf fat (-), backfat (BF) thickness (-), longissimus muscle area (LMA; +), skin thickness (+), muscle firmness and marbling scores (-), organ weights (+), belly (-), clear plate (-), ham (+), and total boneless cuts (BC; +). Somatotropin effects were also present for loin (-) and boneless Boston butt (BBB; +) in the age-matched group and for ADG (+), carcass weight (-), loin (-), jowl (-), and tenderloin (+) in the weight-matched group. Breed effects (P < .05), in favor of Y barrows, in both treatments existed for ADG (+) and feed intake (+), carcass weight (+), dressing percentage (+), LMA (+), skin thickness (-), muscle color and firmness scores (-), muscling score (+), all wholesale cuts (WC; +) except clear plate (age-matched), all trimmed cuts (TC; +) except picnic shoulder (weight-matched), and all BC (+). Breed effects, in favor of Y barrows, were also determined for carcass length (+), percentage of carcass ash (-), leaf fat (+), average BF thickness (+), and heart (-) and liver (-) weights in age-matched animals and percentage of carcass fat (-), protein (+), water (+), leaf fat (-), 10th rib, average, and P2 BF thicknesses (-), marbling score (-), femur length (-), and liver weights (+) in weight-matched animals. A higher response to pST (P < .05) was determined in Ms barrows than in Y barrows for percentage of carcass protein (+), liver (+), and heart (+) in the age-matched treatment and 10th rib BF thickness (-) and heart weight (+) in the weight-matched treatment. Yorkshire barrows treated with pST had more improved values for color score (+; age-matched) and BBB (+; weight-matched).

The effects of porcine somatotropin and dietary lysine on growth performance and carcass characteristics of finishing swine fed to 105 or 127 kilograms.

One hundred twenty barrows (initially 59 kg) were used to determine the effects of dietary lysine and porcine somatotropin (pST) on growth performance and carcass characteristics of finishing pigs fed to heavy market weights (127 kg). Pigs were injected daily with either 4 mg of pST or a placebo and fed diets containing either .8, 1.0, 1.2, or 1.4% lysine in a 2 x 4 factorial arrangement. Performance data were collected and evaluated for the weight ranges: 59 to 105, 105 to 127, and 59 to 127 kg. In addition, daily accretion rates of protein (DPA), lipid (DLA), moisture, and ash were determined by slaughtering six randomly selected pigs at the start of the experiment, then one pig per pen when pigs reached mean weights of 105 and 127 kg. Pigs injected with pST had greater (P < .05) ADG than control pigs at all weight ranges. Increased dietary lysine had no effect (P > .20) on ADG during the entire trial (59 to 127 kg). Although control pigs showed no increase in ADG with increasing lysine, ADG of pST-treated pigs tended to increase. This resulted in a pST x lysine interaction (P < .07) for ADG from 59 to 127 kg. Feed consumption decreased (P < .05) in pigs from 59 to 105 kg and 59 to 127 kg with pST treatment and with increasing dietary lysine. Feed conversion (G/F) was improved (P < .01) by pST administration and a tendency for a pST x lysine interaction (P < .12) was observed. At 105 kg, average backfat thickness, kidney fat, longissimus muscle area, and DPA were unaffected by dietary lysine but were improved by pST treatment (P < .01). At a slaughter weight of 127 kg, average backfat thickness decreased and DPA increased (linear, P < .05) with increasing dietary lysine and pST treatment (P < .01). Longissimus muscle area was increased and DLA was decreased (P < .01) by injections of pST but both were unchanged by dietary lysine. These data indicate that growth performance and carcass characteristics at 105 and 127 kg were improved by daily administration of 4 mg of pST. At both slaughter weights, increasing dietary lysine resulted in increased carcass leanness (increased carcass protein and decreased carcass lipid). Although increasing lysine did not improve overall (59 to 127 kg) ADG and feed efficiency, pST-treated pigs showed a greater response to increasing dietary lysine. The data indicate that pST-treated pigs (4 mg/d) require approximately 28 g/d of lysine.

Effects of porcine somatotropin and dietary phosphorus on growth performance and bone properties of gilts

One hundred eight gilts (initial weight = 58.5 kg) were used to determine the effects of porcine somatotropin (pST) and dietary P on growth performance and bone mechanical properties and mineralization during the finishing phase (58 to 105 kg) and a 35-d postfinishing phase. Gilts were injected daily with placebo (control) or 4 mg of pST and fed diets containing .4, .8, or 1.2% P in a 2 x 3 factorial arrangement. From 58 to 105 kg, administration of pST increased (P < .01) ADG and G/F and decreased (P < .01) ADFI. When mean weight of the gilts in a pen reached 105 kg, half the gilts were slaughtered and first rib, femur, and third and fourth metacarpals were collected for determination of mechanical properties and bone ash. A pST x P interaction was observed (P < .05) for rib bending moment and modulus of elasticity; maximum rib bending moment was attained by control gilts at .8% P and rib modulus of elasticity values remained constant across P levels, whereas rib bending moment and modulus of elasticity increased as dietary P increased from .4 to 1.2% in pST-treated gilts. Administration of pST decreased (P < .05) stress of the rib, femur, and metacarpals compared with control gilts. Increasing dietary P resulted in a linear (P < .10) increase in bending moment, stress, and ash content for rib, femur, and metacarpal bones. The remaining 54 gilts were individually fed 1.8 kg/d of a common diet for 35 d postfinishing.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of a porcine somatotropin implant on tissue mineral status of finishing pigs exposed to a thermoneutral or cold environment

An experiment was conducted with 24 crossbred (Landrace x Yorkshire x Duroc) finishing pigs (mean BW 85 kg) to study the effects of a single 100-mg recombinant porcine somatotropin (rpST) implant on the tissue mineral status of pigs exposed to either a thermoneutral (TN; 18 to 21 degrees C, 50 to 55% RH) or cold (C; 5 to 15 degrees C, 50 to 70% RH) environment until BW averaged 110 kg. The implants used in this study delivered an average 2.4 to 2.5 mg of rpST/d during the course of the study. Control pigs were implanted with a placebo. All diets were supplemented with minerals at levels that either met or exceeded the requirements of an 85-kg pig. At slaughter (mean BW 110 kg), tissues were collected and analyzed for selected macro- and microminerals. Pigs treated with rpST had higher (P < .05) Ca concentrations and total Ca in liver and kidney and higher (P < .05) Ca concentrations in muscle. Total P, Mg, Na, and K were all higher (P < .05) in the liver and kidneys of rpST-treated pigs. In general, rpST had little influence on Cu, Zn, and Fe in tissues. No consistent trend was evident in the response of tissue minerals to environmental temperature. Results indicated that pigs treated with rpST and supplemented with adequate minerals accumulated more minerals in certain tissues than did pigs not given rpST.

Effect of porcine somatotropin on the response of growing pigs to acute challenges of glucose, insulin and epinephrine and during a hyperinsulinemic-euglycemic clamp

Response of tissues to homeostatic signals may play a role in the mediation of nutrient partitioning effects of somatotropin. To investigate this, the effects of exogenous porcine somatotropin (pST) on the metabolic responses to a series of intravenous challenges with dextrose, insulin and epinephrine were examined in twelve crossbred barrows (65 kg). In addition, the hyperinsulinemic-euglycemic clamp technique was used to further explore effects of pST on insulin resistance in eight of these animals. Pigs received daily sc injections of either pituitary-derived pST (120 μg/kg bw) or an equivalent volume of excipient for 28 d. Treatment with pST resulted in a chronic elevation of plasma glucose, insulin and non-esterified fatty acid concentrations and lowered glucagon concentrations. Acute iv challenges of dextrose (100 mg/kg bw), insulin (1.0 μg/kg bw), and epinephrine (2.2 μg/kg bw) were administered on days 21, 22, and 23 of the treatment period, respectively. Hyperinsulinemic-euglycemic clamps were carried out on day 28. Effects of pST were most dramatic for responses associated with insulin. In pST-treated pigs, insulin response to dextrose infusion was enhanced, while glucose response to insulin was attenuated and glucose clearance rate was reduced. During the hyperinsulinemic-euglycemic clamp, dextrose infusion rate required to maintain euglycemia during physiologic elevations of insulin was reduced in pST-treated pigs to 28% of control. In pST-treated pigs, glucose response to epinephrine challenge was halved, while insulin response was increased three-fold. Therefore, one mechanism by which pST shifts the nutrient partition is by altering metabolic responses to homeostatic signals. In growing pigs, this is especially evident for glucose response to insulin.

Dose-dependent effects of exogenous porcine somatotropin on the yield, distribution, and proximate composition of carcass tissues in growing pigs2

Dose-dependent effects of porcine somatotropin (pST) on mass, distribution, and proximate composition of carcass tissues were investigated in 46 growing pigs. Barrows, weighing 30 +/- 1 kg, were assigned to five treatment groups to receive 0, 50, 100, 150, or 200 micrograms of recombinant pST/kg BW per day until pigs individually reached the 90-kg slaughter weight. Left carcass sides were fabricated into whole-sale cuts that were separated into muscle, adipose tissue, bone, and skin. Despite the reduction in dressing percentage, total muscle mass of the side was significantly increased by 3.9 to 5.7 kg (28 to 36%) by the lowest and highest doses of pST, respectively, whereas adipose tissue mass was decreased by 4.4 to 8.6 kg (38 to 74%). Bone mass was increased by 8 to 27% (P < .05), and skin mass was increased by 16 to 38% (P < .01) across the dose range. Distribution of carcass weight among the wholesale cuts was altered by pST toward lower proportions in the belly, jowl, and fat trimmings and greater proportions in the four lean cuts. Porcine somatotropin substantially reduced lipid concentration in all muscle groups in a dose-dependent manner, resulting in increased protein and moisture concentrations (P < .05). Adipose tissue lipid concentrations were reduced to an even greater extent at each dose. The progressive increase in muscle mass observed with pST doses > 50 micrograms/kg BW was less than the associated decrease in adipose tissue mass, indicating that a dose range of 50 to 100 micrograms/kg BW per day may be optimum for improving carcass value.

Porcine somatotropin and dietary lysine influence bone mineralization and mechanical properties of bones in finishing swine2

The femur, a rib, and a third metacarpal were collected from 108 barrows (initial weight = 57 kg) and analyzed to determine the effects of porcine somatotropin (pST) and dietary lysine on bone mineralization and mechanical properties. In Exp. 1, pigs were injected daily with 4 mg of pST and fed diets containing 1.0% Ca and .9% P and either .6, .8, 1.0, 1.2, or 1.4% lysine. Control pigs (placebo injection) received the .6% lysine diet. Bone wall thickness (BWT) of the femur increased (linear, P < .05) but ash content decreased (linear, P < .10) as dietary lysine level increased. Stress and ash content of the rib also decreased (linear, P < .05) with increasing dietary lysine level. In Exp. 2, pigs were injected with either 4 or 8 mg/d of pST and fed diets containing 1.1% Ca and 1.0% P and either .8, 1.0, 1.2, or 1.4% lysine. Control pigs received the .8% lysine diet. Increasing pST dosage increased BWT of the femur (linear, P < .10) but decreased ash content (linear, P < .10). In the rib, increasing pST dosage reduced stress, modulus of elasticity (linear, P < .10), and ash content (linear, P < .01). Increasing lysine level resulted in increased BWT of the femur and decreased ash content of rib, femur, and metacarpal (linear, P < .10). These data indicate that pST administration in conjunction with increasing lysine levels decreases bone ash content but increases BWT of finishing pigs.

Effect of Porcine Somatotropin (pST) on Fat Quality of Growing‐Finishing Pigs

AbstractLong‐term application of recombinat porcine somatotropin to pigs induced a decrease in fat deposition and a reduction in percentage fat in backfat and intramuscular fat. The proportion of poly‐unsaturated fatty acids especially of C18:2 increased. Lower thickness and higher water content of backfat influenced the fat quality negatively. Growth of subcutaneous adipose tissue was affected substantially by pST administration with evidence of dose dependency. During withdrawal time until slaughter a marked compensatory fat deposition occurred.

Effects of porcine somatotropin (PST) administration on the fat/lean content and processing properties of pork bellies

Porcine somatotropin (PST)-supplemented pigs were slaughtered at 109 or 131·8 kg; bellies were analyzed for compositional and bacon processing characteristics and compared with bellies from controls (slaughtered at 109 kg). Bellies from control and 109 kg, PST-treated pigs were significantly lighter (P < 0·01) in weight whereas the PST-treated bellies were significantly (P < 0·01) leaner than controls regardless of slaughter weight. The leaner bellies resulted in greater (P < 0·01) brine pickup, reduced smokehouse yields and bacon with less fat regardless of slaughter weight. Frying yield for the bacon from PST-treated pigs was significantly (P < 0·01) higher than that of the controls probably because of the fat/lean difference. The changes observed in bacon from PST-supplemented pigs appear to be due to the compositional change induced by PST administration.