Search

Dietary betaine may reduce carcass fat in growing pigs. We explored the effects of betaine on short-term growth and in vivo and in vitro fatty acid oxidation. Pigs were housed in metabolism crates and fed diets containing either 0% (control), 0.125% or 0.5% betaine at 80% of ad libitum energy intake. Fatty acid oxidation was measured during intravenous infusions of 1-(13)C-palmitate and in hepatocytes incubated in the presence or absence of betaine and carnitine. CO2 and palmitate isotopic enrichments were determined by mass spectrometry. Pigs consuming 0.125% and 0.5% betaine for at least 9 days had growth rates that were 38% and 12% greater than controls, respectively. Feed efficiency was also improved with betaine. Fasting increased palmitate oxidation rates 7-8-fold (P < 0.01), but betaine had no effect in either the fed or fasted state (P > 0.1). For hepatocytes, carnitine but not betaine enhanced palmitate oxidation. This response suggests that previously observed reduction in adipose accretion must be via a mechanism other than oxidation. Betaine had no effect on plasma non-esterified fatty acids or urea nitrogen. Under the confinement conditions in this study, dietary betaine improved animal growth responses, but it had no apparent effect on either whole body or hepatic fatty acid oxidation.

The effect of multiple lipopolysaccharide (LPS) challenges in swine undergoing long-term treatment with porcine somatotropin (PST) was determined. Changes in aspartate serine transaminase (AST) occurred only at 24h following the first LPS challenge dose (P<0.05), while PST treatment moderated any change from occurring. Nonesterified free fatty acid (NEFA) levels were elevated in PST treated animals for the first 3 days following daily LPS treatment (P<0.05), while LPS treatment alone had no effect on plasma NEFA levels. Plasma urea nitrogen (PUN) levels were unchanged by LPS following the initial LPS challenge, but were decreased following the second challenge dose (P=0.014). These changes were long lasting, with a return to normal PUN levels not evident until Day 6. The PST treatment mitigated changes in PUN (P<0.05) when LPS was administered. Haptoglobin plasma levels, along with lipid peroxide production were not affected by LPS challenge or PST administration. LPS challenge reduced the levels of immunoreactive heat shock protein 70 (HSP70) throughout the entire challenge period (P<0.001). PST-LPS animals had normal levels of this protein. The results of the present study demonstrate that long-term PST treatment mitigates the adverse effects of subchronic LPS administration.

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.

The dietary dose responsiveness of conjugated linoleic acid (CLA) addition relative to the fatty acid profile of edible lean tissue was examined in grower pigs treated with or without porcine somatotropin (pST). Gilts and barrows were fed CLA at 0, 0.25, 0.5, 1.0, or 2.0% of diet by weight from 20 to 55 kg BW. Additional pigs were administered (pST) at 0 or 100 microg x kg BW x d(-1) and fed either 0.5 or 2.0% CLA. Animals were fed diets containing 18% CP, 1.2% lysine, and 3.5 Mcal of DE/kg at 110% of ad libitum intake. The fatty acid profile in latissimus dorsi and dorsal s.c. adipose tissue samples was determined by gas chromatography. Dietary CLA replacement of corn oil increased the percentage of total fatty acids as stearic acid, whereas the percentages as oleic and linolenic acids were reduced in lattisimus muscle. Treatment with CLA + pST increased the percentages of linoleic and arachidonic acids while reducing the percentages of palmitic and oleic acids in lattisimus muscle. Dietary CLA increased the percentages of palmitic and stearic acids in s.c. adipose tissue while reducing the percentages of oleic, linoleic, linolenic, and arachidonic acids. The percentage of palmitic acid was reduced in s.c. adipose tissue, whereas linoleic acid was increased with CLA + pST. No synergistic effect was detected between CLA and pST for reducing carcass lipid content in grower pigs. However, pST increased the percentage of polyunsaturated fatty acids in lattisimus muscle and s.c. adipose tissue while reducing the percentages of saturated fatty acids in swine fed CLA.

The ontogeny of the somatotropin/insulin-like growth factor system was examined in well-fed pigs under basal conditions and during a short-term challenge of porcine ST (pST). The study was conducted with two replicates of eight castrate male pigs from 3.8 kg BW (10 d of age) to 92 kg BW (129 d of age). Pigs were reared individually with ad libitum access to milk replacer through 23 d of age. Thereafter, pigs were fed a corn, soybean meal, and dry skim milk diet formulated to exceed nutrient requirements by approximately 30%. Pigs were randomly assigned to receive daily i.m. injections of either 0 (buffer) or 120 microg/kg BW of pST for a duration of 4 d starting at 10, 19, 33, 43, 63, 83, and 125 d of age. Blood was collected via jugular venipuncture on d 0 and 4 of the challenge. Circulating levels of IGF-I were not dramatically affected by age, but levels of IGF-II were low from 10 to 19 d of age and then increased through later stages of growth. Circulating concentrations of IGF binding protein (BP)-3 increased with age (P < .05), but levels of IGFBP-2, a 30-kDa IGFBP, and IGFBP-4 were unchanged (P > .10). The pST challenge reduced plasma urea nitrogen at all ages, but the magnitude of the response was less in younger pigs compared with the maximum response in pigs greater than 30 kg BW (63 d of age). The IGF-I response to the pST challenge also increased from approximately 30% in young pigs to a threefold increase in older pigs. Regardless of age, concentrations of IGF-II were minimally affected by the pST challenge. Circulating levels of IGFBP-3 increased and IGFBP-2 levels decreased in response to the pST challenge, and the magnitude increased with age. The high nutritional status of pigs in the early phases of growth diminished the postnatal changes in IGF-I and IGFBP-2, but not IGF-II or IGFBP-3. Overall, data demonstrate a developmental regulation of the ST/IGF system, with pST challenges altering circulating concentrations of IGF-I, IGFBP-3, and IGFBP-2 coincident with changes in amino acid metabolism.

Growing (35 kg body weight) and finishing (85 kg body weight) swine challenged with endotoxin (Escherichia coli O55:B5) at a dose of either 2 or 20 microg/kg produced tumor necrosis factor (TNF)alpha in a dose-response relationship as measured by bioassay. Peak TNFalpha plasma levels were observed 1-2 hr post-challenge, returning to basal values 4 hr post-challenge. However, both an enzyme-linked immunosorbent assay specific for swine TNFalpha and total human TNFalpha demonstrated no dose-response relationship; peak plasma levels of immunoreactive TNFalpha were also observed 1-2 hr post-challenge. Maximal plasma interleukin-6 levels occurred 1-2 hr post-challenge and remained elevated through 8 hr post-challenge; there was no effect of lipopolysaccharide dose or metabolic status. Although the metabolic status of the animals also affected glucose levels, with growing animals exhibiting greater sensitivity compared with finishing animals, endotoxin-induced decreases in blood glucose levels were primarily dose-dependent. In contrast, changes in plasma urea nitrogen and free fatty acid (FFA) levels were strictly related to the metabolic status. Urea nitrogen levels were unchanged in growing swine, whereas they were increased in finishing swine and remained elevated 24 hr post-challenge. FFA levels in growing and finishing swine increased 3-6 hr post-challenge. FFA levels returned to basal values for finishing swine 24 hr post challenge, but in growing swine remained elevated 24 hr post-challenge. Plasma aspartate transaminase levels were increased through 24 hr post-challenge; animals given a dose of 20 microg/kg exhibited the greatest increase. Similarly, swine challenged with a dose of 20 microg/kg also exhibited the greatest increase in levels of conjugated bilirubin; there was no effect on unconjugated (free) bilirubin. These results demonstrate that endotoxin challenge of swine result in a pattern of changes that are dependent on both the dose of endotoxin used and the metabolic status of the animal examined.

Two experiments were conducted with cross-bred barrows to determine the effect of somatotropin administration on liver enzyme activities. In the first experiment, pigs growing from 26 to 55 kg body weight were given two doses of pituitary porcine somatotropin (pST; 0 and 100 micrograms per kg body weight) and three levels of dietary energy (60, 80 and 100% of free choice intake). In the second experiment, pigs growing from 30 to 60 kg body weight were given two doses of recombinant porcine somatotropin (rpST; 0 and 100 micrograms per kg body weight) and five levels of dietary crude protein (110, 150, 190, 230 and 270 g crude protein/kg diet). Liver arginase (ARG, EC 3.5.3.1) and aspartate aminotransferase (AAT, EC 2.6.1.1) activities were then determined in organ samples taken at slaughter time. Dietary energy did not change liver ARG. Activities of both ARG and AAT increased as dietary crude protein increased. Both pST and rpST decreased ARG, AAT and serum utrea nitrogen. There was a lack of interaction between rpST therapy and dietary protein on either ARG or AAT activities, suggesting that set nutritional states are not required for expression of pST effects.

We conducted two experiments to determine the efficacy of exogenous porcine somatotropin (pST) on enhancing performance during an early phase of growth (10 kg initial BW) when pigs are already growing efficiently and have high rates of lean deposition and low rates of lipid deposition. In Exp. 1, performance was measured on 45 barrows that received one of five daily doses (0, 50, 100, 150 and 200 microg/kg BW) of recombinant pST. In Exp. 2, 27 barrows were used in a slaughter-balance study in which two groups received daily either buffer (control) or 120 microg/kg BW of pST and the third group was slaughtered for initial body composition. In both experiments, pigs received daily i.m. injections of their respective dose for 20 d. The diet was fed for ad libitum consumption and calculated to contain 3.5 Mcal DE/kg, 22.3% CP, and 1.5% lysine. Administration of pST failed to alter overall growth rate or efficiency of gain in either experiment. However, in Exp. 2 pigs treated with pST had increased deposition rates of protein and water but reduced lipid deposition rates. Furthermore, pST treatment resulted in characteristic reductions in plasma urea nitrogen and elevations in glucose and NEFA. Plasma concentrations of insulin and IGF-I were also increased, but pST reduced IGF-II and IGF binding protein-2. Overall, the data demonstrated that very young pigs respond to pST with enhanced lean tissue accretion and metabolic changes, but the response is attenuated compared with previous studies in older growing pigs.

Barrows were restrictively fed starting at 20 kg BW to determine the effects of endotoxin on growth performance of control and somatotropin-treated pigs. The following treatments were used: 1) daily i.m. vehicle injection until 55 kg BW; 2) daily i.m. injections of 100 micrograms of recombinant porcine somatotropin (pST)/kg BW, until 55 kg; 3) i.v. saline injections for 7 d consecutively starting at 60 kg BW; 4) i.v. injections of 1 microgram of bacterial lipopolysaccharide (LPS)/kg BW for 7 d starting at 60 kg BW; and 5) the combined LPS+pST treatment, with pST injections from 20 kg through the 7 d of LPS treatment. Pigs evaluated for LPS effects were fed to 60 kg anticipating a weight loss. Pigs were bled at 0800 and 1100 at 55 kg and on d 7 of LPS treatment. Rectal temperatures were taken on d 7. Treatment with pST increased ADG by 13 to 20% and improved feed:gain by 17 to 23% before LPS treatment. During the 7 d of LPS injections, ADG and feed:gain did not differ, although feed efficiency was impaired and variable. Rectal temperatures at 1100 were progressively increased: control < LPS < LPS-pST (P < .01). Protein accretion was improved 27% by pST treatment, and lipid accretion was decreased 45% before LPS. Lipid stores decreased (P < .01) after LPS treatment in the pST-treated pigs. Lipopolysaccharide treatment and(or) decreased feed intake reduced the hyperinsulinemia and hyperglycemia (P < .01) associated with pST treatment. These results indicate that LPS induced a simulated septicemia and that the effects were not negated by pST treatment. The observed hyperthermia was additive, possibly due to increased lean body mass induced by pST combined with the pyrogenic effect of LPS.

Objective: To determine whether recombinant porcine somatotropin (PST) or chromium picolinate (CrP) affected cytokine production and metabolism in swine after endotoxin challenge exposure., Animals: 20 Poland China X Landrace pigs, 5/group., Procedure: Pigs were given CrP-supplemented feed at body weight of 20 kg; PST treatment began at 60 kg, and both treatments continued through body weight of 90 kg. At 90 kg, pigs were challenge exposed with 20 micrograms of lipopolysaccharide (LPS)/kg of body weight. Blood samples were obtained at various times through 24 hours after LPS challenge exposure., Results: In all pigs not given PST, glucose concentration decreased 2 to 4 hours after LPS. In PST-treated pigs, blood glucose concentration was decreased at 6 to 8 hours after LPS. Plasma insulin concentration paralleled changes in glucose concentration. Nonesterified fatty acid concentration was high 2 to 24 hours after LPS in pigs not given PST and at 6 to 24 h in PST-treated pigs. Plasma urea nitrogen concentration was high at 6 to 24 hours after LPS in pigs not given PST. The urea nitrogen values in PST-treated pigs were lower at all times. Serum aspartate transaminase activity was high 6 to 24 hours after LPS in pigs not given PST, whereas PST treatment prevented the increase in this enzyme activity. In untreated (PST) pigs, plasma bilirubin (total and direct) concentrations were high 4 to 8 hours after LPS and returned to normal at 24 hours. The PST- and CrP-treated pigs maintained normal plasma bilirubin concentrations. Interleukin 6 activity was unaffected by CrP and PST treatments. Treatment with CrP and PST decreased the tumor necrosis factor alpha response to LPS, compared with that in control pigs., Conclusions: PST, and to a lesser extent CrP, provide protection against the adverse metabolic effects of LPS-induced septic shock.

Chromium (Cr) and somatotropin have been shown to increase lean body mass in pigs but by independent mechanisms. Somatotropin and Cr also affect blood glucose, lipids, and tissue trace metal concentrations. Twenty-four castrated male pigs were divided into four groups: 1) control basal diet; 2) basal diet + 300 micrograms of Cr/kg of diet as Cr picolinate; 3) basal diet + pituitary porcine somatotropin (ppST; 100 micrograms/kg live weight injected daily); and 4) basal diet + Cr + ppST. Pigs were fed the diets from 30 to 60 kg body weight and then killed. Supplemental Cr led to increased total Cr in kidney (1.1 vs 2.3 micrograms) and liver (5.9 vs 8.8 micrograms) but not in the heart independent of ppST treatment. Chromium concentrations in longissimus muscle were less than 1.5 ng/g in all samples, and any increases due to supplemental Cr were not detected. Somatotropin treatment led to decreased hepatic Cr, Cu, Fe, and Zn concentrations and increased total renal Cu, Fe, and Zn. These data demonstrate that supplemental Cr causes increased tissue Cr in the liver and kidney but not in the heart or muscle in control and somatotropin treated pigs. Somatotropin treatment caused decreased kidney and liver Cr concentrations that were offset by increased tissue weights. Somatotropin effects on tissue Cr, Cu, Zn, and Fe were variable and difficult to evaluate due in part to growth hormone-induced changes in organ weights.

This research was conducted to evaluate the characteristics of muscle fiber growth and the effects of porcine somatotropin (pST; 100 micrograms.kg-1 BW.d-1) administration on the morphology of 12 muscles located in different regions of the body in barrows growing from 20 to 90 kg BW. In the course of the growth of control pigs, the percentage distribution of beta R fibers did not show any changes in all 12 muscles, whereas the percentage of alpha R and alpha W fibers changed in different patterns in different muscles. The administration of pST had no effect on fiber type distribution. The cross-sectional area of alpha W fibers was the largest of the three fiber types, and beta R and alpha R fibers were of similar size in all muscles. All fiber types in all muscles increased in cross-sectional area by an average of 120% from 20 to 60 kg BW. After 60 kg BW, the growth of alpha W fibers in seven (early maturing) muscles and alpha R fibers in one muscle out of the 12 muscles was not apparent. The increase of their cross-sectional area was an average of 12%, but the area of the other muscle fibers continued to increase by an average of 38% until 90 kg BW. The administration of pST increased the area of alpha W fibers in four out of seven of these early-maturing muscles by an average of 25%, suggesting some possible relationships between pST effects and the rate of muscle fiber maturation. Most of the muscles that responded to pST treatment were located in hindlimb region.

In a 2 x 2 treatment array (n = 4 pigs/treatment), the effects of feed intake (ad libitum vs. restricted to 60% ad libitum) and the daily administration of excipient buffer or porcine pituitary-derived growth hormone (GH) at a dose of 100 micrograms/kg body weight per day on serum GH profile and human growth hormone-releasing factor (hGRF) response were examined in barrows weighing 55 kg. Feed intake treatment was implemented from 25 to 55 kg live weight. Buffer or GH treatment was implemented for 10 d before sampling. After GH treatment, the integrated serum GH concentration area was 25% greater in barrows fed restrictively. Data are consistent with the suggestion that GH dose to improve the efficiency of lean tissue deposition be adjusted according to feeding regimen. The serum GH response to hGRF was also altered by level of feed intake. The ad libitum feeding of buffer-treated animals resulted in a monophasic serum GH response to hGRF, whereas barrows fed restrictively had a biphasic response to hGRF. Together, these data suggest that feed intake pattern alters GH secretion and as such could influence the practical implementation of somatotropin as a metabolism modifier in swine.

The effect of dietary chromium picolinate (CrP) and recombinant porcine growth hormone, somatotropin (rPST) administration on growth performance and cytokine production in Landrace-Poland China gilts was determined using a 2 by 2 treatment array. Treatments were: (1) control (basal diet), (2) CrP-supplemented diet (basal diet + 300 micrograms Cr3+/kg diet as CrP), (3) rPST (100 pg/kg body weight/day), and (4) rPST+CrP. CrP-supplemented diets were fed beginning at 20 kg body weight through 90 kg. Administration of rPST was begun at 60 kg weight and continued through 90 kg. All rPST treated pigs demonstrated improvements in growth performance versus controls. Pigs given CrP-supplemented diets showed no differences in growth performance. At 90 kg, pigs were challenged with endotoxin (lipopolysaccharide, 0.2 microgram/kg i.v.). Blood samples were collected at 0, 1, and 3 h postchallenge. Plasma IL-6 levels increased from 23 U/ml at time 0 to 1,927 U/ml at 3 h for control swine. Swine from the CrP treatment group had IL-6 levels of 8,130 U/ml at 3 h post-LPS. There were no differences in plasma IL-6 from pigs in the rPST and rPST+CrP treatment groups compared to the controls. Endotoxin challenge had no effect on either blood glucose levels or induction of TNF-alpha in any treatment group. PBMC from CrP-treated animals produced more IL-2 than peripheral blood mononuclear cells from all other groups.

The level of protein in the diet both before and during treatment with beta-adrenergic agonist (BAA) was investigated with regard to its effect on growth performance and carcass characteristics of pigs. A total of 76 pigs were divided into two groups and given ad libitum access to diets containing either 12 or 18% crude protein (CP) during growth from 15 to 60 kg. At 60 kg, six pigs from each group were slaughtered and carcass composition was determined. For the test period (growth from 60 to 90 kg) the remainder of the pigs were divided into eight groups of eight pigs each. Half of the pigs from each of the two dietary pretreatment groups were switched to the other diet and half remained on the same diet. Of the four dietary groups, half were fed 0 mg/kg (controls) or 1 mg/kg of BRL 47672. During the test period, all pigs were fed at 90% of their calculated ad libitum DE intake. All pigs were slaughtered at 90 kg and carcass composition was determined. Addition of BRL 47672 to the diet resulted in an overall improvement (P < .05) in daily gain (.72 vs .64 kg) and gain/feed (.28 vs .26); the greatest improvement occurred with pigs fed the 18% CP diet (24 and 14% for daily gain and gain/feed, respectively). Pigs that had received BRL 47672 also had 12% less backfat, 10% less carcass lipid, 16% larger longissimus muscle area, and 5% more carcass protein (P < .05 for each), and the greatest changes occurred in pigs fed the 18% CP diet (-26, -16, +21, and +10%, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Sixty crossbred barrows (average 30 kg) were used in a 5 x 2 factorial treatment array to examine interactions between dietary protein concentration (11, 15, 19, 23, or 27% CP) and recombinant porcine somatotropin (rpST: 0, excipient buffer vs 100 micrograms.kg-1.d-1) for 42 d on muscle fiber morphology and meat tenderness. Diets were isocaloric (3.8 Mcal of DE/kg) and of equal lysine (4.9 g/Mcal of DE) achieved by diluting soybean meal with cornstarch and by addition of crystalline lysine. Dosage of rpST and feed intake (80% of predicted ad libitum) were adjusted weekly. Four muscles (longissimus = LM; semimembranosus = SM; semitendinosus = ST; triceps brachii = TB) were evaluated. Percentages of muscle fiber types (beta R, alpha R, alpha W) for the LM, SM, and TB were not influenced by rpST treatment. More alpha R and fewer alpha W fibers were found in the ST muscle of rpST-treated pigs. No interactions were observed between rpST treatment and dietary protein for muscle fiber type distribution. Dietary protein had no consistent influence on the distribution of muscle fiber types in all four muscles. Area of fibers generally increased in rpST-treated pigs compared with controls when diets contained 19% or more CP. The LM shear force was increased (13%) by rpST treatment for chops frozen after 5 d of storage in the cooler, but not in those chops frozen within 1.5 h postmortem. Dietary protein had a variable influence on tenderness. These data indicate that muscle fiber growth (hypertrophy) in pigs is positively influenced by rpST treatment. Marginal dietary protein intake reduces muscle fiber growth responses to rpST.

A study was conducted to determine the feasibility of using differences in the natural abundance of dietary 13C as a means of in vivo labeling. Four female pigs were fed a C3 plant diet (barley, soybean meal and alfalfa) and four were fed a C4 plant diet (corn and corn gluten meal). The pigs were continually fed the diets from 8 wks of age to maturity and through pregnancy until they had themselves produced offspring. The resulting piglets were sacrificed at various time intervals (0 to 165 days) after switching either the piglets or their mothers' to the opposite diet. Changes in the delta 13C levels in samples of milk and tissues following the diet change were monitored by isotope ratio mass spectrometry. The differences in the delta 13C content of the two diets was 12.9 parts per mil (/1000). After piglets born to a sow fed the C3 diet were switched at one day of age to a surrogate sow fed the C4 diet, tissue delta 13C levels of the piglets were nearly identical to the diet of the surrogate sow by 11 days while those switched from C4 to C3 grew more slowly and differed from the diet by 2-5/1000. When the mothers diet was switched, 15-20 days later the delta 13C in the milk had changed by only 2-3/1000, indicating that the body rather than the diet was the primary source of carbon in the milk. At 28 days after the piglets diet was switched at weaning, the tissue delta 13C had changed by 8.4/1000 (C4 to C3) and 2.9/1000 (C3 to C4). The delta 13C level in the liver changed more rapidly than in the muscle or fat and the rate of change was also influenced by the size and growth rate of the pig.

Twenty-four castrated male pigs were used in a 2 x 2 treatment array to determine the main effects of and interactions between dietary chromium supplementation and pituitary porcine somatotropin (ppST) administration on growth performance and serum hormone and metabolite concentrations. The treatments were 1) control (basal diet); 2) chromium (basal diet+300 micrograms/kg diet added trivalent chromium as chromium picolinate); 3) ppST (100 micrograms/(kg body wt.d); and 4) chromium+ppST. Treatments were administered when pigs weighed between 30 and 60 kg. Blood was collected when pigs weighted 45 and 60 kg. All pigs treated with ppST exhibited improvements in growth performance (P < 0.05). Pigs given chromium showed no improvements in growth rate, feed efficiency or composition of gain. Measurements at 60 kg body weight revealed that ppST increased the cholesterol:HDL cholesterol ratio (P < 0.05). Chromium lowered serum insulin and glucose concentrations relative to controls (P < 0.05) and normalized the increase in glucose and insulin resulting from ppST treatment. No ppST x chromium interactions were noted, suggesting these changes in glucose and insulin metabolism are exerted through different mechanisms. These results indicate that chromium does not affect growth performance of young growing pigs. Chromium does normalize altered hormone and metabolite concentrations resulting from ppST treatment.

Three groups of eight gilts weighing 20, 40, or 60 kg were fitted with indwelling venous catheters to determine daily integrated circulating levels (DICL, serum concentration above baseline x time) of insulin, growth hormone (GH), glucagon, glucose, urea, and nonesterified fatty acids (NEFA) in response to acute challenge with porcine pituitary GH (pGH). Pigs were fed a common diet containing 18% CP and 3.5 Mcal of DE/kg between 0800 and 1200 (85% of ad libitum). Blood and urine were collected at 2- or 4-h intervals for 4 d. On d 2, 3, and 4, four pigs in each group were injected i.m. at 0800 with pGH (.1 mg/kg) and four pigs (controls) were injected with buffer. In control pigs DICL of GH was 20.4, 14.1, and 10.2 ng pGH.h.mL-1 in 20-, 40-, and 60-kg pigs, respectively. The DICL of GH in pGH-treated pigs was 4.2-, 7.0-, and 10.7-fold greater in 20-, 40-, and 60-kg pigs, respectively, than in controls. The DICL of insulin in control pigs was 7.9, 9.7, and 9.4 ng.h.mL-1 and was increased (P < .001) in pGH-treated pigs by 118, 213, and 276% in 20-, 40-, and 60-kg pigs, respectively. Although serum levels of glucose were increased (P < .001) by pGH treatment, the acute elevation observed in 60-kg pigs was more consistent relative to 20- and 40-kg pigs. In contrast, the acute reduction in blood urea upon pGH injection was more apparent in 20-kg gilts.(ABSTRACT TRUNCATED AT 250 WORDS)

Thirty-two crossbred barrows were used to determine the effects of frequency of administration of equivalent total dosages of recombinant porcine somatotropin (rpST) on growth performance, tissue accretion rates, and hormone and metabolite status of pigs. Treatments were control (buffer-injected daily), 60 micrograms/kg BW daily (4 injections/4 d), 120 micrograms/kg BW injected every other day (2 injections/4 d), or 240 micrograms/kg BW given every 4th d (1 injection/4 d). Treatments were initiated at 35 BW and continued until each pig had consumed a total of 440 Mcal of DE intake. Pigs were fed a diet that contained 16% CP, 1.2% lysine, and 3.5 Mcal of DE/kg at 85% of calculated ad libitum intake. Feed intake and rpST dose were adjusted at 8-d intervals. The 240 micrograms/kg BW treatment did not decrease appetite beyond the 15% restriction already imposed in the experimental design. Treatment groups responded to rpST in a frequency-dependent manner. Average daily gain was improved by 10, 23, and 36%, respectively, as injection frequency was increased from 1/4 to 2/4 to 4/4 d. Muscle weights were increased uniformly (15% on average) on a BW basis by all rpST treatments. Carcass (21, 42, and 63%), visceral (43, 65, and 112%), and empty body (22, 43, and 65%) protein accretion rates were increased by rpST treatment in a frequency-dependent fashion, respectively. Lipid accretion also was reduced in carcass and empty body (31% on average) by all rpST injection schemes relative to controls; however, visceral lipid accretion was increased by 59% by rpST. Protein utilization efficiency increased linearly by 24, 45, and 65% as the frequency of injection of rpST was increased from 1/4 to 2/4 to 4/4 d. Hormones and metabolites exhibited frequency-related profiles as well. These results suggest that frequency of administration greatly influences the magnitude of responsiveness to rpST and that optimal benefit would be realized by a delivery system that mimicked a daily surge, at minimum, of rpST.

The effect of ractopamine, a beta-adrenergic agonist, on growth, nutrient utilization, and carcass composition was studied in pigs fed either 18% CP, 12% CP, or 18% CP restricted (RES = 67% of ad libitum) diets. The 18 and 12% CP diets provided 3.52 and 3.68 Mcal of DE/kg, respectively. All pigs were fed a low-protein (12% CP) diet during pretreatment growth from 15 to 60 kg. Ractopamine at 20 or 30 ppm (30 ppm for RES pigs) in the diet was fed from 60 kg live BW until slaughter at 105 kg (9 pigs/treatment). No ractopamine treatment effect (P greater than .05) was observed for either daily gain or gain/feed, although gain/feed was improved by 8% in both of the ad libitum groups. Ractopamine treatment resulted (P less than .01) in an overall reduction of carcass lipid by 8%, an increase of carcass protein by 5%, and a 21% improvement in the efficiency of protein utilization; the greatest changes occurred in the pigs fed the 12% CP diet (-17%, +11%, and +32%, respectively). The ad libitum daily feed intake was 15% less for pigs fed the 12% CP diet than for those fed the 18% CP diet (P less than .01), and there was a 10% reduction in intake of both diets with the addition of ractopamine (P less than .05). Both carcass lipid and protein deposition seemed to be closely related to energy intake (P less than .01).(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Thirty-six barrows were used in a 2 X 3 factorial treatment array to determine the effects of time of injection (0800 [AM] or 1800 [PM]) of recombinant porcine somatotropin (rpST) (0, 50, or 100 micrograms.kg BW.d-1 adjusted weekly) relative to time of feeding on growth performance, carcass composition, serum hormones and metabolites, and muscle RNA, DNA, and protein. Pigs were fed at 85% of ad libitum and allowed access to feed between 0800 and 1200. Treatments were initiated at 38 kg and continued until each pig consumed an average of 7.5 Mcal of DE/d. There was no significant effect of injection time for any measure of growth performance or composition of gain even though rpST treatment improved most criteria evaluated. Treatment with rpST increased ADG by 30%, improved feed:gain by 23%, reduced lipid accretion by 46%, increased protein accretion by 69%, and increased loin eye area (LEA) by 26%. Time of injection also had no effect on serum hormones or metabolites, except for nonesterified fatty acids (NEFA), which were 20% higher in the AM-injected animals. Treatment with rpST increased (P less than .05) RNA concentration (21%) and RNA/DNA (17%) in longissimus dorsi (LD) muscle. In semimembranosus (SM) muscle, however, rpST administration resulted in an increased (P less than .05) DNA concentration (10%) and a decreased DM content (4%). These results suggest that rpST influences growth differently in these two muscles. We conclude that time of rpST administration (AM vs PM) has no effect on its metabolic properties and, therefore, no effect on growth performance in the pig.

Twenty-four barrows were used to investigate the effects of exogenous porcine somatotropin (pST) administration (0 and 100 micrograms.kg-1.d-1) between 30 and 60 kg on longissimus muscle morphology and meat tenderness of pigs grown to 90 kg. Administration of pST was by daily i.m. injection. Pigs were fed a fortified diet in restricted amounts between 30 and 60 kg and had ad libitum access to this diet from 60 to 90 kg. Excipient pigs had fewer alpha R fibers and more alpha W fibers than pST-treated pigs (P less than .05). Administration of pST increased (P less than .05) muscle fiber area for all three fiber types at both the 60 kg (34%) and 90 kg (29%) slaughter weights. Furthermore, pST administration increased shear-force (30% at 60 kg; 19% at 90 kg) of the longissimus muscle, indicating that pST administration reduced meat tenderness. All the pST-treated pigs exhibited the "giant fiber syndrome" and a high proportion (62%) of pST-treated pigs exhibited pale, soft, exudative muscle. Whether the giant fiber anomaly resulted from increased muscle protein accretion rate or fiber degeneration is unknown. Results indicated that the stimulatory effects of pST on muscle growth are sustained following cessation of hormone treatment. However, the incidence of pale, soft, exudative muscle in 62% of the pST-treated pigs indicates that pST potentially has undesirable side effects.

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)

The effect of ractopamine, a phenethanolamine beta-adrenergic agonist, on growth, nutrient utilization and carcass composition was studied in two lines of pigs that were fed high (24%) or low (12%) protein diets. Of the two lines of pigs that had been selected for seven generations for rapid lean growth when fed either the higher (HS line) or low (LS line) protein diet, the HS line tended to exhibit a leaner carcass when fed either diet. Ractopamine, at 20 ppm in the diet, was fed from 60 kg live body weight until slaughter at 90 kg. When compared with their respective line-diet control group, the greatest response to ractopamine treatment was observed in the LS-12 group; at 90 kg, that group had 31% less carcass lipid (P less than .05) and 17% more carcass protein (P less than .05). Considering the change that took place only between 60 and 90 kg live body weight, this translated into 57% less lipid and 59% more protein deposited in the carcasses with ractopamine treatment. This group also was 73% more efficient (P less than .05) in converting dietary protein to carcass protein but 39% less efficient (P less than .05) in energy utilization. Response to ractopamine treatment was least by the LS-24 group, followed by the HS-12 and HS-24 groups. A line x diet x treatment interaction (P less than .05) was noted for whole-carcass lipid, backfat, longissimus muscle area and efficiency of protein utilization.(ABSTRACT TRUNCATED AT 250 WORDS)

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

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.

An experiment with crossbred swine was conducted over six generations of selection based on an index (Index) of average daily gain in weight (ADG) in a test period from 56 d of age to 91 kg gross weight and average backfat thickness (ABF) measured from ultrasonic scans at 91 kg. Test pigs of the high protein select (HS) and control (HC) lines were fed a 24% crude protein (CP) diet and pigs of the low protein select (LS) and control (LC) lines were fed a 12% CP diet during the test period. The extent of genetic (selection line) x environmental (dietary) interaction effects was determined based on feeding closely related boars and gilts from both the HS and LS lines on both diets. Tests were conducted in 1986 and 1987 with progeny of the fifth and sixth generations of selection. Records for 472 pigs sired by 37 boars and out of 101 dams were analyzed for effects of selection and diets on AGE of pig at 91 kg, ADG, ABF, LMA (longissimus muscle area at the last rib) and Index. Statistically significant interactions effects of line x diet were noted (P less than .01) for AGE, ADG and Index, traits with low to moderate heritabilities (h2). For ABF and LMA, body composition traits with moderate or higher h2, interaction effects of line x diet were near zero. These results suggest that for best all-around future performance, traits such as AGE and ADG, selection probably should be practiced under dietary conditions under which future populations will be produced. For body composition traits such as ABF and LMA, selection probably would be more effective if pigs were fed a more enriched protein diet. However, as a practical matter, to more rapidly improve the genetic merit of the swine population, both the central station and on-the-farm testing programs should be conducted under standard commercial production systems.

Two experiments were conducted with young, growing pigs to evaluate the effects of protein levels and supplemental lysine on growth, body characteristics and urea cycle enzyme activities. In the first experiment, 8-week-old pigs weighing 17 kg were fed two levels of protein (12 or 20%) until they reached slaughter weight of approximately 95 kg. In the second experiment, three levels of protein (12, 18 or 24%) and one level of additional lysine (9 g/kg of diet added to the 12% protein diet) were fed for the same interval. After slaughter, urea cycle enzyme activities (argininosuccinate synthetase, EC 6.3.4.5; argininosuccinate lyase, EC 4.3.2.1; and arginase, EC 3.5.3.1) were determined in liver homogenates. Early growth of pigs was improved by increasing the protein level (12%) but not by adding the limiting amino acid lysine to the 12% diet. The cross sectional area of the Longissimus dorsi muscle at slaughter was increased by protein level (12%) or by adding lysine to the 12% protein diet. In contrast, subcutaneous fat was decreased only by increasing the dietary protein level. The activities of arginase, argininosuccinate synthetase and argininosuccinate lyase were increased in a linear fashion by increasing the dietary protein level. In contrast, adding lysine to the 12% protein diet did not increase urea cycle enzyme activities.

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.

Lipid compared with carbohydrate calories in the diet of peripartal sows was examined for specific metabolic effects. Blood samples from second-parity Yorkshire sows fed isocaloric-isonitrogenous diets that differed by either glucose or corn oil supplying 20% of the daily metabolizable energy intake were assayed for growth hormone (GH), insulin and prolactin (PRL) concentrations. On d 97 to 103 of gestation, serum GH levels were reduced following feed intake; the reduction was greater (P less than .05) in glucose-fed sows during the postprandial period. Insulin concentration was increased following consumption of either diet, but to a greater (P less than .05) extent in glucose-fed sows corresponding to the greater (P less than .05) blood glucose response. Basal, fasting concentrations of PRL were not affected by dietary energy source; however, thyrotropin-releasing hormone (TRH) infusion resulted in a greater (P less than .05) PRL response of fat-fed sows. Samples obtained on d 8 to 11 of lactation revealed that TRH stimulated (P less than .05) GH secretion and the response was greater (P less than .05) in fat-fed sows. Plasma insulin concentration was increased (P less than .05) following feeding, and the increase was greater (P less than .05) in glucose-fed sows. Similar to the response measured in gestating sows, TRH-induced increases in PRL was greater in fat-fed, lactating sows. Sham-nursing did not influence maternal PRL concentration compared with the immediate increase noted following natural nursing. No effect of dietary energy source on reproductive performance characteristics was noted. Results of this study have shown that dietary lipid, compared with carbohydrate, selectively increased the sensitivity of the pituitary gland to a GH and PRL secretagogue such as TRH. The beneficial effects of lipid in the diet of peripartal swine may be attributable, in part, to the effect of dietary lipid on maternal pituitary PRL synthesis and(or) release.

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.

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.

One,three-butylene glycol (BG) was isocalorically substituted for glucose and fed ad libitum to lean (XB) and obese (HL) swine at 0, 10, and 20% of the total dietary ME from 25 kg body weight until slaughter at 90 kg. BG depressed rate and efficiency of gain in both groups. Plasma beta-hydroxybutyrate concentration was increased by the ketogenic energy substitution. Plasma glucose and free fatty acids were not influenced by diet composition. Adipose tissue utilization of glucose for lipogenesis was depressed by BG in both XB and HL animals after 4 wk of treatment. Insulin added in vitro increased glucose utilization by approximately 20% in adipose tissue from both breed groups; however, the BG induced depression of glucose utilization for fatty acid synthesis was still evident. Insulin-stimulated glucose utilization was greater in XB then in L swine. After 12 wk of dietary treatment, animals given BG had significantly increased plasma insulin concentration and decreased plasma urea concentrations. Although the absolute rates of lipogenesis had decreased after 12 wk of treatment, similar diet-related results were obtained. Insulin did not stimulate glucose utilization by adipose tissue from animals of either breed group at this latter sampling. Fatty acid esterification was slightly depressed by BG at the 4 wk sampling, but after 12 wk of treatment, only a significantly breed group effect was evident. Subcutaneous fat thickness, loineye area and carcass percentage lean cuts were not influenced by diet composition. This experiment demonstrated that ketogenic energy and substitution in the diet does depress the rate of de novo lipogenesis from glucose as measured by in vitro incubation of swine adipose tissue. Supplementation of the incubation media with massive quantities of insulin did not reverse the dietary treatment effects, and animals of both lean and obese phenotypes responded similarly to the dietary treatment. The absence of dietary treatment effects on indices of body fat content suggest that ketone bodies may be substituted for glucose as a lipogenic substrate in swine.

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.

Two experiments were conducted with second-parity sows fed either 5 or 50% alfalfa meal diets (Exp. 1) or 5, 50 or 95% alfalfa meal diets (Exp. 2) beginning 30 d after breeding and continuing through lactation, 21 d postpartum. Diets in both experiments were calculated to be equal in crude protein, but different in metabolizable energy content. Feed intake was restricted to 2 kg/d during gestation and ad libitum during lactation. Sows were tethered in metabolism crates 45 d after breeding. Total feces were collected during two 5-d collection periods, 60 and 100 d after breeding. Digestibilities of dry matter, fiber components (neutral detergent fiber, acid detergent fiber, hemicellulose and cellulose), protein and energy were determined in both experiments for all diets and periods of gestation. In both experiments, there was a reduction (P less than .05) in digestibility of dry matter, fiber components, protein and energy with increasing fiber levels for both periods of gestation. In Exp. 1, the decrease in digestibility of dry matter, neutral detergent fiber, acid detergent fiber, cellulose and energy was greater at 100 d gestation than at 60 d in sows fed 50% alfalfa. In Exp. 2, 50 and 95% dietary alfalfa reduced 60-d digestibilities of dry matter, all fiber constituents, energy and protein; these digestibilities were further reduced (P less than .05) at 100 d of gestation. In Exp. 1, weight gains of sows fed 5 and 50% alfalfa diets from breeding to 109 d gestation, were 42 and 18 kg/sow (5 greater than 50% level, P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Records for pigs included in an experiment on reciprocal recurrent selection conducted from 1956 through 1971 at the USDA Beltsville Agriculture Research Center were analyzed to obtain estimates of heritabilities and genetic correlations and to derive prediction equations for estimating weight of lean cuts (WTLC) and percentage of lean cuts of shrunk slaughter weight (LCPC). Lean cuts growth rate (LCGR) was then estimated as WTLC/age of pig at slaughter. The base population consisted of two unrelated crossbred strains. A total of 1,294 records of F1 and F2 crossbred pigs were analyzed with one barrow and one gilt from each litter. Estimates of heritabilities and genetic correlations were computed with sire components of variance and covariance from a nested analysis of variance with an assumed model of years, strain-lines within years, sire within strain-lines, dams within sires and residual. Degrees of freedom were 307 for sires in strain-lines, 270 for dams in sires and 646 for residual. Heritability (h2) estimates were .42 +/- .13, .41 +/- .13 and .27 +/- .18 for WTLC, LCPC and LCGR, respectively, and .71 +/- .16, .38 +/- .13, .31 +/- .13 and .25 +/- .15 for carcass length, average backfat thickness, longissimus muscle area and ADG in BW, respectively. These estimates were apparently the first published genetic estimates involving LCGR based on carcass data. It was recommended that prediction equations to estimate WTLC, LCPC and LCGR for use in swine testing programs be derived from current meat-type pigs.

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

Analyses of variance were computed for records on growth and body composition traits made in 1983 by 255 boars and gilts in selected and control lines of Durocs and Yorkshires and their reciprocal crossbreds. Previous selection over a period of several generations was mainly on an index of sow productivity including preweaning litter sizes and weight. Animals in the select lines were selected for high index values; animals in the control lines were selected to average near the mean index values of that year and line. Breeding animals in all four lines during that period were basically randomly selected with regard to growth rate or body composition traits. The same boars sired both purebred and crossbred litters in 1983. Traits analyzed were average daily gain (ADG) during a standard test period from 56 d of age to 90.7 kg and average backfat thickness (ABF) and longissimus muscle area (LMA) from ultrasonic scans at 90.7 kg. Crossbred pigs had greater (P less than .01) ADG than purebred pigs, but did not differ (P greater than .05) in ABF or LMA. Heterosis was 8.2% for ADG. Crossbreds with Yorkshire dams had thinner (P less than .01) ABF and larger (P less than .01) LMA than crossbreds with Duroc dams. Boars had greater (P less than .05) ADG, thinner (P less than .01) ABF and smaller (P less than .01) LMA than gilts. Correlations between 38 half-sib family averages of purebred and crossbred pigs of the same sex and the same sires were .07, .37 and .24 for ADG, ABF and LMA, respectively. Implications of the above and additional findings for swine breeding strategies are discussed.

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.

Systemic ketosis was induced in first-parity gilts by the isocaloric substitution of glucose with 1,3-butylene glycol to supply 20% of the total dietary energy beginning on d 23 (23 BG) or d 60 (60 BG) of gestation. Ketosis reduced (P less than .05) maternal plasma glucose, urea N and insulin concentrations. Fetal carcass dry matter and carcass glycogen contents were reduced (P less than .05) by maternal ketogenic calorie substitution, whereas fetal hepatic glycogen and lipid contents were not influenced by maternal treatment. Neural acetate oxidation was reduced (P less than .05) in the 23 BG and 60 BG fetuses, with a concurrent increase (P less than .05) in beta-hydroxybutyrate (BOHB) oxidation. Neural lipogenesis measured from acetate and BOHB substrates was nominal in the d 105 pig fetus. Fetal hepatic acetate and BOHB utilization for lipogenesis were increased (P less than .05) by maternal ketosis. Reproductive performance characteristics (litter size, number stillborn and birth weight) were not improved by maternal ketosis. The substantial improvement in lactation weight gain by litters from 23 BG and 60 BG dams (20%, P less than .05) may suggest a carryover effect of gestation dietary treatment on lactation performance.

Maternal ketosis was induced in sows by feeding 20% of the dietary energy as 1,3-butylene glycol (BG), medium-chain triglycerides (MCT), or a combination of the two. Brain development and hepatic glycogen synthetase and phosphorylase were assessed in 105-day-old fetuses as a function of maternal diets. Butylene glycol was more ketogenic than MCT. Furthermore, maternal ketosis induced by BG increased fetal brain weight, protein content, and cell size. Maternal ketosis also increased fetal liver glycogen possibly by causing the accumulation of glucose residues in the liver by suppressing liver glycolysis. In addition, glycogen synthetase alpha was increased by maternal ketosis. A fetal form of synthetase was noted in the liver which was stimulated by glucose-6-phosphate (G6P) in the presence of Na2SO4, an inhibitor of the G6P-dependent form of the enzyme.

Urea and deuterium oxide (D2O) space were compared by simultaneous infusion into pigs weighing approximately 55 or 90 kg. Urea was cleared from the plasma pool more rapidly than D2O and appeared to equilibrate at a relative concentration which was lower than that of D2O. Consequently, urea and D2O space values were closest when extrapolated to zero time values. Correlations between urea space and D2O space were highest at 15 minutes post infusion (R2 = .75) or between urea space at 15 minutes and D2O at equilibrium (R2 = .86). Results of urea and D2O space measurements were compared with water, lipid and protein content of the carcass. Urea space at 15 minutes and D2O space at 35 minutes most closely approximated total body water while D2O space at 15 minutes was nearly equivalent to empty body water. Overall, D2O space at equilibrium had the highest correlations with carcass values of water, lipid and protein and appears to be preferable to urea space for estimating carcass composition in pigs.