Effects of combining three fungal phytases with a bacterial phytase on plasma phosphorus status of weanling pigs fed a corn-soy diet.

The objective of this study was to determine possible synergistic effects of supplementing one of three fungal phytases: Aspergillus fumitagus PhyA (AFP),A. niger PhyA (ANP), or Peniophora lyci phytase (PLP) with an Escherichia coli AppA phytase (EP) in diets for pigs. Three experiments, each lasting for 4 wk, were conducted with a total of 106 weanling pigs (5 wk old). The corn-soybean meal basal diet (BD) contained no supplemental inorganic P. In Exp. 1, 35 pigs (8.6 +/- 1.0 kg BW) were fed (as-fed basis) BD + AFP at 750 U/ kg of feed, BD + inorganic P (0.2% P), or BD + PLP at 500, 750, or 1,000 U/kg feed. Pigs fed BD + AFP or BD + 0.2% P had higher (P < 0.05) plasma inorganic P concentrations than those fed BD + PLP at the end of the trial (wk 4). In Exp. 2, 35 pigs (8.1 +/- 0.9 kg BW) were fed BD + AFP, EP, PLP, a 1:1 mix of AFP:EP, or a 1:1 mix of PLP:EP at 500 U/kg. Pigs fed the AFP:EP mixture had growth performance and plasma measures similar to those fed either enzyme alone. Pigs fed the PLP:EP mixture had lower (P < 0.05) plasma alkaline phosphatase activity than those fed BD + PLP. Pigs fed BD + PLP had lower (P < 0.05) plasma inorganic P concentrations than pigs fed BD + EP, and higher (P < 0.05) plasma alkaline phosphatase activity than all other groups at wk 4. In Exp. 3, 36 pigs (9.1 +/- 1.2 kg BW) were fed BD + ANP, EP, or a 1:1 mix of ANP:EP at 500 U/kg feed. Pigs fed the two enzymes together had lower (P < 0.05) plasma inorganic P concentration than those fed BD + EP and lower (P < 0.05) plasma alkaline phosphatase activity than pigs fed BD + ANP at wk 4. In conclusion, although the four phytases showed different effects on plasma P status of weanling pigs, there was no synergistic effect between any of the three fungal phytases and the bacterial phytase on the plasma measures or growth performance under the conditions of the present study.

Evaluation of fat sources on cholesterol and lipoproteins using pigs selected for high or low serum cholesterol.

At approximately 8 weeks of age, four-way cross (Chester White×Landrace×Large White×Yorkshire) pigs (n=24) were selected based on genetically high (H) or low (L) serum cholesterol levels-12 from each genetic group-to determine the relationship between genetics, fat source, and sex class on plasma cholesterol, growth, carcass characteristics, and cholesterol and lipid content of muscle and adipose tissues. Boars and gilts, six each from the two genetic groups, were assigned randomly to one of three dietary treatments for 46 days. A standard grower diet was modified to include beef tallow (T), corn oil (CR) or coconut oil (CC), and the pigs were given ad libitum access to feed. Cholesterol was added to each diet to ensure the diets contained the same amount of cholesterol. Except for the plasma lipids, there were no differences between boars and gilts at the initial evaluation or at the end of the treatment; therefore, sex means were pooled for statistical analyses. Body weight was unaffected by diet on days 18, 29 or 46. Blood samples were taken on days 1, 29, and 46 via the anterior vena cava. Plasma total cholesterol (TC) and low density lipoprotein cholesterol (LDL) concentrations were greater in the H than L groups (overall TC in H and L pigs=150 and 124 mg/dl, respectively, and LDL in H and L pigs=105 and 76 mg/dl, respectively). Pigs fed diets containing saturated fats had greater TC and LDL than pigs fed unsaturated fats (TC=165, 149, and 126 mg/dl for T, CC, and CR diets, respectively, and LDL=108, 88, and 77 mg/dl for T, CC, and CR diets, respectively). There were significant time×gene×sex interactions for both TC and LDL yielding subtle differences in the response of the sexes from the two genetic groups over time. Pigs were slaughtered on day 46, and carcass data were collected. There were no differences in fat at the first rib, 10th rib, last rib, or last lumbar vertebra, but differences (P <0.05) were found between genetic groups for M. longissimus thoracis et lumborum (LTL) muscle area (H=21.0±0.8 cm(2), L=18.1±1.0 cm(2)) and USDA muscle score (H=2.1±0.1, L=1.7±0.1). There were no genetic or diet effects for cholesterol content of pre-rigor or post-rigor LTL muscle. Neither genetics nor dietary treatment affected the cholesterol content of the adipose tissue. There were no differences in fat percentage between genetic groups for muscle or adipose tissue. There were differences (P <0.05) in total lipid content among the dietary treatments for the pre-rigor (T=6.0±0.6%, CC=4.3±0.3%, CN=3.9±0.5%) and post-rigor (T=6.4±0.9%, CC=4.1±0.3%, CN=5.0±0.4%) LTL. Cholesterol accretion in muscle and adipose tissues of growing pigs was not influenced by source of fat in the diet or by their genetic propensity for high or low plasma cholesterol.

Effectiveness of an experimental consensus phytase in improving dietary phytate-phosphorus utilization by weanling pigs.

Consensus phytase is a new biosynthetic, heat-stable enzyme derived from the sequences of multiple homologous phytases. Two experiments were conducted to determine its effectiveness, relative to inorganic P and a mutant enzyme of Escherichia coli phytase (Mutant-EP), in improving dietary phytate-P availability to pigs. In Exp. 1, 36 pigs (3 wk old, 7.00 +/- 0.24 kg of BW) were fed a low-P corn-soybean meal basal diet plus consensus phytase at 0, 250, 500, 750, 1,000, or 1,250 U/kg of feed for 5 wk. Plasma inorganic P concentration, plasma alkaline phosphatase activity, bone strength, and overall ADG and gain:feed ratio of pigs were improved (P < 0.05) by consensus phytase in both linear (R2 = 0.20 to 0.70) and quadratic (R2 = 0.30 to 0.70) dose-dependent fashions. In Exp. 2, 36 pigs (4 wk old, 9.61 +/- 0.52 kg BW) were fed the basal diet + inorganic P at 0.1 or 0.2%, consensus phytase at 750 or 450 U/kg of feed, Mutant-EP at 450 U/kg of feed, or 225 U consensus + 225 U Mutant-EP/kg of feed. Pigs fed 750 U of consensus phytase or 450 U of Mutant-EP/kg feed had plasma inorganic concentrations and bone strength that fell between those of pigs fed 0.1 or 0.2% inorganic P. These two measures were 16 to 29% lower (P < 0.05) in pigs fed 450 U of consensus phytase/kg of feed than those of pigs fed 0.2% inorganic P. Plasma inorganic P concentrations were 14 to 29% higher (P < 0.05) in pigs fed Mutant-EP vs. consensus phytase at 450 U/kg at wk 2 and 3. In conclusion, the experimental consensus phytase effectively releases phytate P from the corn-soy diet for weanling pigs. The inorganic P equivalent of 750 U of consensus phytase/kg of feed may fall between 0.1 and 0.2%, but this requires further determination.

Effects of stocking rate and crude protein intake during gestation on ground cover, soil-nitrate concentration, and sow and litter performance in an outdoor swine production system.

Pregnant gilts (n = 126) were assigned randomly to 12 0.4-ha old world-spar bluestem (Bothriochloa ischaemum) pastures in an outdoor swine (Sus scrofa) production system to examine effects of stocking rates (17.5 or 35 gilts/ha; 7 or 14 gilts per pasture) and dietary N on percentage of ground cover, soil nitrate (NO3-) concentration, and reproductive performance. Treatments were arranged factorially with two stocking rates and two diets equivalent in dietary lysine but different in CP (control = 14.7% CP vs experimental = 12.6% CP) with three pastures per treatment. The experiment was repeated during a second parity with the same animals on the same treatments. Each triangular gestation pasture was subdivided into three regions: 1) near the point or radial center; 2) the middle region that contained a hut and a wallow area; and 3) the outer section where gilts were fed each day. Soil samples (15 cm deep) were taken at the beginning and end of the 306-d study, and soil nitrate-N concentrations were determined. Percentage of ground cover was visually estimated initially and every 30 d thereafter through d 306. Before farrowing, gilts were moved to identical pastures for farrowing and were fed a common 16% CP sorghum (Sorghum bicolor)-based lactation diet beginning at the time of movement to the farrowing pasture. Pregnant gilts were weighed at the time of assignment to treatments in the gestation pastures, when they were moved to farrowing pastures, and at weaning. Production data included total number of pigs born per sow, number of pigs born alive or dead, average birth weight, number of pigs weaned, average weaning weight, and mortality. No differences (P > 0.05) were observed between treatments in soil NO3- concentrations. Percentage of ground cover was decreased (P < 0.01) by the higher stocking rate when grazing was initiated in March/April but recovered rapidly after removal of pigs. More (P < 0.01) pigs were weaned per sow (8.4 vs 7.1+/-0.34) from higher gestation-stocking rate groups. Pig mortality in farrowing was greater (P < 0.05) for lower gestation-stocking rates (25.7% vs. 18.1+/-1.9%). A stocking rate of 35 sows/ha might have increased production potential but was associated with a rapid loss of ground cover during spring.

Perinatal ontogeny of brain growth in the domestic pig.

The perinatal development of the brain is highlighted by a growth spurt whose timing varies among species. The growth of the porcine cerebrum was investigated from the third trimester of gestation (70 days postconception) through the first 3.5 weeks of postnatal life (140 days postconception). The shape of the growth curves for cerebrum weight, total protein mass, total cell number (estimated by DNA content), and myelination (estimated by cholesterol accretion) were described. The growth velocity of cerebrum weight had two peaks, one at 90 days and the other at 130 days postconception, whereas that of total protein was greatest from 90 to 130 days postconception, and that of total DNA was greatest between 90 and 110 days and again at 130 days postconception. The growth velocity for total cholesterol continued to increase during the entire period, suggesting that myelination continued after the growth spurts for cells (protein and DNA). The growth velocity patterns observed in these contemporary pigs suggest that this species may be an appropriate model for human brain development, not only in the perinatal pattern of increase in mass of the cerebrum, as established previously, but also with regard to the patterns of cellular development and myelination.

Dietary intrinsic phytate protects colon from lipid peroxidation in pigs with a moderately high dietary iron intake.

High iron consumption has been proposed to relate to an increase in the risk of colon cancer, whereas high levels of supplemental sodium phytate effectively reduce iron-induced oxidative injury and reverse iron-dependent augmentation of colorectal tumorigenesis. However, the protective role of intrinsic dietary phytate has not been determined. In this study, we examined the impact of removing phytate present in a corn-soy diet by supplemental microbial phytase on susceptibility of pigs to the oxidative stress caused by a moderately high dietary iron intake. Thirty-two weanling pigs were fed the corn-soy diets containing two levels of iron (as ferrous sulfate, 80 or 750 mg/kg diet) and microbial phytase (as Natuphos, BASF, Mt. Olive, NJ, 0 or 1200 units/kg). Pigs fed the phytase-supplemented diets did not receive any inorganic phosphorus to ensure adequate degradation of phytate. After 4 months of feeding, liver, colon, and colon mucosal scrapings were collected from four pigs in each of the four dietary groups. Colonic lipid peroxidation, measured as thiobarbituric acid reacting substances (TBARS), was increased by both the high iron (P< 0.0008) and phytase (P< 0.04) supplementation. Both TBARS and F2-isoprostanes, an in vivo marker of lipid peroxidation, in colonic mucosa were affected by dietary levels of iron (P< 0.03). Mean hepatic TBARS in pigs fed the phytase-supplemented, high iron diet was 43%-65% higher than that of other groups although the differences were nonsignificant. Moderately high dietary iron induced hepatic glutathione peroxidase activity (P= 0.06) and protein expression, but decreased catalase (P< 0.05) in the colonic mucosa. In conclusion, intrinsic phytate in corn and soy was protective against lipid peroxidation in the colon associated with a moderately high level of dietary iron.

Maternal dietary protein deficiency decreases nitric oxide synthase and ornithine decarboxylase activities in placenta and endometrium of pigs during early gestation.

Little is known about the mechanism responsible for retarded placental and fetal growth induced by maternal dietary protein malnutrition. On the basis of the recent finding that nitric oxide (NO) and polyamines (products of L-arginine) play an important role in embryonic and placental development, the present study was designed to determine whether protein deficiency decreases placental and endometrial activities of NO synthase (NOS) and ornithine decarboxylase (ODC) (the first and key regulatory enzyme in polyamine synthesis). Primiparous gilts selected genetically for low or high plasma total cholesterol concentrations (low line and high line, respectively) were mated and then fed 1.8 kg/d of isocaloric diets containing 13% or 0.5% crude protein. At d 40 or 60 of gestation, they were hysterectomized, and placenta and endometrium were obtained for incubations, NOS and ODC assays, and measurements of free amino acids and polyamines. Maternal dietary protein restriction decreased arginine and ornithine concentrations, constitutive and inducible NOS activities and NO production, as well as ODC activity and polyamine concentrations in placenta and endometrium of both lines of gilts. Placental NO synthase activity and NO generation were lower in high line gilts than in low line gilts. ODC activities and polyamine concentrations in placenta and endometrium were decreased at d 60 compared with d 40 of gestation. These changes in placental and endometrial synthesis of NO and polyamines during early gestation may be a mechanism responsible for reduced placental and fetal growth in protein-deficient gilts and for altered conceptus development in high line gilts.

Pigs fed cholesterol neonatally have increased cerebrum cholesterol as young adults.

Sixty-eight female neonatal pigs selected for seven (Experiment 1) or eight (Experiment 2) generations for high (HG) or low (LG) plasma cholesterol were used to test the hypothesis that neonatal dietary cholesterol fed during the first 4 or 8 wk of postnatal life increases the cholesterol content of the cerebrum in young adulthood following free access to a high-fat (15%), high-cholesterol (0.5%) diet from 8 to 20 or 24 wk of age. Pigs were removed from their dams at 1 d of age and given free access to a sow-milk replacer diet containing 9.5% coconut fat and 0 or 0.5 % cholesterol. All pigs (except four HG and four LG pigs in Experiment 2, which were deprived of cholesterol throughout the study) were fed the high-fat, high-cholesterol diet from 8 wk to termination at 20 or 24 wk of age. Cerebrum weight and cholesterol concentration were higher in pigs fed cholesterol neonatally than in those deprived of cholesterol neonatally in both experiments, but weight and cholesterol concentration were unaffected by genetic line. Cholesterol concentrations in longissimus and semitendinosus muscles and in subcutaneous fat were unaffected by diet or genetic line. We conclude that dietary cholesterol deprivation during the first 4 to 8 wk of life in piglets is associated with lower cholesterol concentration and total content in the young adult cerebrum than in pigs supplemented with cholesterol in early life. These data support previous observations and suggest the possibility of a metabolic need for neonatal dietary cholesterol in normal brain development.

Adding wheat middlings, microbial phytase, and citric acid to corn-soybean meal diets for growing pigs may replace inorganic phosphorus supplementation.

Three experiments were conducted with 96 growing Landrace x Yorkshire x Duroc crossbreds to determine the collective effectiveness of cereal phytase from wheat middlings, microbial phytase, and citric acid in improving phytate-P bioavailability in corn-soy diets. In Exp. 1, 40 gilts (7 wk old) were fed five diets for 8 wk. Diets 1, 2, and 3 were low-P, corn-soybean meal diets (CSB) + 0, .1, or .2% inorganic P (Pi) as calcium phosphate, respectively. Diet 4 was a similar corn-soy diet that included 15% wheat middlings (461 cereal phytase U/kg). Diet 5 was the CSB + microbial phytase (1,200 U/kg; Natuphos, BASF, Mount Olive, NJ). In Exp. 2, 16 barrows (8 wk old) were fed two diets for 6 wk. Diet 1 was the same as Diet 3 of Exp. 1 (.2% Pi). Diet 2 was Diet 4 of Exp. 1 + microbial phytase (300 U/kg). In Exp. 3, 40 barrows and gilts (6 wk old) were fed four diets for 6 wk. Diets 1 and 2 were the same as those in Exp. 2. Diet 3 was Diet 2 of Exp. 2 + 1.5% citric acid. Diet 4 was similar to Diet 3 but contained 10 instead of 15% wheat middlings. In Exp. 1, pigs fed the low-P, CSB (Diet 1) had lower (P < .05) ADG, ADFI, plasma Pi concentration, bone strength, and mobility score than pigs of the other four treatments. Measurements for pigs fed the 15% wheat middlings diet were not significantly different from those of pigs fed the CSB + .1% Pi or microbial phytase. In Exp. 2, ADG (P=.06) during wk 1 to 3 and gain:feed ratio (P < .02) and plasma Pi concentration (P < .005) during all weeks favored pigs fed the CSB + .2% Pi compared with the other diet including 15% wheat middlings. In Exp. 3, identical ADG during all weeks and similar plasma Pi concentrations at wk 4 and 6 were observed between pigs fed the two citric acid diets (Diets 3 and 4) and the CSB + .2% Pi (Diet 1). Pigs fed Diet 4 (10% wheat middlings) had even higher (P < .02) gain:feed ratio during wk 1 to 3 than those fed Diet 1. It seems feasible to completely replace calcium phosphate with 10 to 15% wheat middlings, 300 U microbial phytase/ kg, and 1.5% citric acid in the corn-soy diets for growing pigs.

Maternal dietary protein deficiency decreases amino acid concentrations in fetal plasma and allantoic fluid of pigs.

This study was conducted to test the hypothesis that maternal dietary protein deficiency decreases amino acid availability to the fetus, thereby contributing to retarded fetal growth. Primiparous gilts selected genetically for low or high plasma total cholesterol concentrations (low line and high line, respectively) were mated, and then fed 1.8 kg/d of isocaloric diets containing 13% or 0.5% crude protein. At d 40 or 60 of gestation, they were hysterectomized, and maternal and fetal blood samples as well as amniotic and allantoic fluids were obtained for analyses of amino acids, ammonia and urea. Dietary protein restriction decreased (P < 0.05) the following: 1) maternal plasma concentrations of urea at d 40 and 60 of gestation; 2) fetal plasma concentrations of alanine, arginine, branched-chain amino acids (BCAA), glutamine, glycine, lysine, ornithine, proline, taurine, threonine and urea at d 60 of gestation; 3) amniotic and allantoic fluid concentrations of urea at d 40 and 60 of gestation; and 4) allantoic fluid concentrations of alanine, arginine, BCAA, citrulline, cystine, glycine, histidine, methionine, proline, serine, taurine, threonine and tyrosine at d 40 of gestation, in gilts of both genetic lines. At d 60 of gestation, protein deficiency decreased (P < 0.05) allantoic fluid concentrations of arginine, cystine, glycine, taurine and tyrosine in low line gilts and of cystine, glutamine, ornithine, serine, taurine and tyrosine in high line gilts. Low line and high line gilts also differed remarkably in allantoic fluid concentrations of arginine, glutamine, ornithine and ammonia at d 40 and 60 of gestation. Our results suggest the following: 1) protein-deficient gilts maintain maternal plasma concentrations of amino acids by mobilizing maternal protein stores and decreasing oxidation of amino acids during the first half of gestation; 2) protein deficiency may impair placental transport of amino acids from the maternal to the fetal blood; and 3) low line and high line gilts differ in fetal amino acid metabolism. Decreases in concentrations of the essential and nonessential amino acids in the fetus may be a mechanism whereby maternal dietary protein restriction results in fetal growth retardation.

Alleles of the cholesterol 7 alpha-hydroxylase (CYP7) gene in pigs selected for high or low plasma total cholesterol.

Crossbred pigs were selected for high (HTC) or low (LTC) plasma total cholesterol (TC). Pigs from the seventh (n = 51) and eighth (n = 92) generations were used to determine restriction fragment length polymorphisms (RFLP). Using TaqI restriction enzyme digestion, the frequencies of two alleles (2.8- or 5.0-kb fragments) of the cholesterol 7 alpha-hydroxylase (CYP7) gene were determined in the two populations as a potential indicator of TC concentration at 8 weeks of age. Only the 2.8-kb fragment allele was present in the 26 HTC pigs tested in Generation 7. In the LTC pigs both the 2.8- and 5.0-kb alleles were present in 12 pigs, and only the 5.0-kb allele was present in 13 pigs. The allele frequencies of the 2.8 and 5.0 fragments, respectively, were .26 and .74 in LTC pigs and 1.00 and 0 in HTC pigs. There was an association (P < .001) between the 5.0- and 2.8-kb CYP7 alleles, respectively, and low and high TC concentrations. In Generation 8, all HTC pigs were homozygous for the 2.8-kb allele. The 5.0 kb allele was present in all LTC pigs tested and was homozygous in 57% of LTC pigs. Mean plasma TC was 105.0 mg/dl in 30 pigs homozygous for the 2.8-kb allele in Generation 8; means for LTC pigs were 53.5 and 60.4 mg/dl in 35 pigs homozygous for the 5.0-kb allele and in 27 heterozygous pigs, respectively. High TC was associated with the presence of the 2.8-kb allele, and low TC was associated with the presence of the 5.0-kb allele in both Generations 7 and 8. We conclude that TaqI RFLP analysis of the CYP7 gene is a reliable indicator for TC in these swine.

Exogenous insulin-like growth factor-I increases weight gain in intrauterine growth-retarded neonatal pigs.

Many cases of intrauterine growth retardation (IUGR) are the result of placental insufficiency, suggesting that potential therapies should focus on the neonate rather than the pregnant female. We wished to determine whether IGF-I could be used therapeutically to stimulate normal rates of growth in these neonates. Eight sows received 2.3 kg/d of either a control (13% protein) or protein-restricted (0.5% protein) diet from d 63 of pregnancy to parturition. Litters were reduced to 6 pigs at 3 d of age, and IUGR neonates were fostered onto a control sow. Three pigs/ litter received an osmotic minipump containing either saline or recombinant human IGF-I, delivered at 4 microg/h from d 3 to d 10 of age. Tissue protein synthesis was measured in all pigs using a flooding dose of [3H]phenylalanine. At birth, both body weight (10%) and circulating IGF-I concentration (30%) were significantly lower in IUGR than in control newborns. The infusion of IGF-I to IUGR neonates significantly increased the circulating concentration of IGF-I, growth rate, and protein and fat accretion to control levels. The infusion of IGF-I did not alter concentrations of insulin, glucose, IGF-II, or the thyroid hormones. Our results suggest that IGF-I may be a potential therapy to restore normal growth in IUGR infants.

Intrauterine growth restriction does not alter response of protein synthesis to feeding in newborn pigs.

This study aimed to determine the effect of intrauterine growth restriction (IUGR) on the acute response of tissue protein synthesis to feeding in newborn pigs. Newborn pigs of sows fed either control or protein-restricted diets throughout gestation were designated C or IUGR, respectively. Both groups were either fasted for 9 h after birth or fed hourly 30 ml colostrum/kg body wt for 2.75 h after a 6-h fast. Fractional rates of tissue protein synthesis (Ks) were measured in vivo with a flooding dose of L-[4-3H]phenylalanine. Birth weight was reduced by 33% in IUGR pigs. IUGR had no effect on Ks in skeletal muscles, heart, liver, jejunum, or pancreas. Feeding stimulated tissue Ks similarly in C and IUGR pigs. Fasting plasma insulin concentrations and their rise with feeding were unaffected by IUGR. Plasma insulin-like growth factor I (IGF-I) concentrations were reduced by 42% in IUGR pigs and were not altered by feeding in either IUGR or C pigs. There were positive nonlinear relationships between tissue Ks and circulating concentrations of insulin. The results indicate that, in newborn pigs, tissue Ks are unaffected by IUGR, despite reduced plasma IGF-I concentrations. The efficiency with which nutrients stimulate tissue Ks is also not altered by IUGR, perhaps because the rise in plasma insulin concentrations with feeding is unaffected by IUGR.

Divergent concentrations of plasma metabolites in swine selected for seven generations for high or low plasma total cholesterol.

It was reported previously that selection for high (HG) or low (LG) plasma total cholesterol (TC) at 8 wk of age in a composite four-breed swine population resulted after four generations in divergent mean concentrations in the selected lines. The data revealed a significant positive correlation between body weight (BW) and TC concentration at 8 wk of age and differential responses in litter size, backfat depth, and carcass length at 6 mo of age. We report here the relationship between plasma TC concentration and other plasma traits related to growth and metabolism in the seventh generation of selection in these two lines of pigs. We measured plasma concentrations of TC, HDL cholesterol (HDL-C), triglycerides (TG), alkaline phosphatase (ALP), total protein (TP), albumin (ALB), urea nitrogen (urea N), and three transaminases (alanine aminotransferase, ALT; aspartate aminotransferase, AST; gamma glutamyltransferase, GGT) in seventh-generation male and female pigs at 8 wk of age. Birth weight (1.48 vs 1.38 kg), 8 wk BW (14.85 vs 12.00 kg), TC (116.8 vs 63.6 mg/dL), HDL-C (43.9 vs 25.5 mg/dL), TG (50.5 vs 33.0 mg/dL), and ALP (78.3 vs 44.9 units/L) were higher (P < .01) in HG than in LG pigs, whereas ALB (3.2 vs 3.4 g/dL), ALT (43.0 vs 45.9 units/L), and AST (53.0 vs 62.2 units/L) were lower in HG than in LG pigs (P < .05). At 8 wk, overall plasma TC concentration was correlated with BW (r = .34, P < .01) and with ALP (r = .23, P < .05) but was not related to ALT, AST, or GGT. Plasma TP urea N, and GGT were unaffected by genetic line on sex. We conclude that the difference between HG and LG pigs in TC concentration in generation 4 at 8 wk of age has persisted but not broadened in pigs of generation 7, that changes in plasma ALP, ALT, and AST may have occurred in response to selection for high or low plasma TC, and that ALP is correlated with plasma TC concentration.

Ontogeny and dietary modulation of 3-hydroxy-3-methylglutaryl-CoA reductase activities in neonatal pigs.

The development of hepatic and ileal -hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase was studied in three types of young pigs crossbred, obese, and lean pigs). Pigs were fed one of two diets: a high-fat (coconut oil), high-cholesterol 1.0%; designated HC) diet or a high-fat, noncholesterol (designated NC) diet from postpartum d 3 to d 13, 25, and 42 (crossbred only). There were four pigs per age per diet group (except for obese pigs). Liver and ileal mucosal microsomal reductase activities were determined by the conversion of [14C]HMG-CoA to mevalonic acid followed by lactonization of the product. The samples were analyzed by thin layer chromatography and liquid scintillation spectrometry. Hepatic reductase activity (1 unit of specific activity = 1 pmol.min-1.mg protein-1) was < 20 units on d 3 in all groups. By d 13, the activity was 40 to 46 units in all groups of pigs fed HC and approximately 50 to 80 units in pigs fed NC. Reductase activity then decreased at d 25 to 18 to 40 units in pigs fed NC and to < 14 units in pigs fed HC. The d 42 reductase values (crossbred only) were approximately 14 units for pigs fed both HC and NC diets. Intestinal reductase activity was not affected (P > .1) by either age or diet. The data suggest that dietary cholesterol suppressed hepatic reductase activity in young pigs (d 13 and 25) from divergent genetic backgrounds. The data also suggest that the stage of development is a dominant factor in regulating porcine hepatic HMG-CoA reductase activity, which was considerably increased at d 13, even in pigs fed HC diets. The relatively modest increase in plasma cholesterol, even in pigs fed cholesterol during the suckling period, provides evidence that both dietary and endogenously synthesized cholesterol are probably used predominantly for tissue building in very young pigs (d 13).

Chronic low protein intake reduces tissue protein synthesis in a pig model of protein malnutrition.

To determine the effect of severe chronic protein deficiency on protein synthesis in different tissues and total protein in plasma, and on plasma biochemical constituents involved in amino acid metabolism, we fed diets containing either 20 or 3% protein to two groups of four age-matched piglets. After consuming the diets for 8 wk, the pigs received a primed-constant infusion of 2 H3-leucine for 8 h to measure the fractional synthesis rates (FSR) of tissue protein and total protein in plasma. Plasma urea and amino acid concentrations, particularly indispensable amino acids, were significantly lower in protein-deficient pigs. Fractional protein synthesis rates were lower in skin by 66% (P < 0.01), in jejunal mucosa by 50% (P < 0.05), in masseter muscle by 40% (P < 0.05), and in liver by 25% (P < 0.02); the fractional synthesis rate of the longissimus muscle was not different than controls. Although plasma protein concentration was significantly (P < 0.01) lower in protein-deficient pigs, the fractional synthesis rate of the total intravascular plasma protein pool was not different. We conclude that adaptation to a low protein diet involves a reduction in the rate of protein synthesis in most body tissues, with the most marked changes occurring in skin and intestine, two tissues which frequently exhibit severe functional impairment in protein malnutrition.

Obese pigs fed a high cholesterol diet from birth to 2 months are less susceptible than lean pigs to atherosclerosis.

Dietary cholesterol in infancy may alter cholesterol metabolism and the propensity to develop atherosclerosis. This study examined the effects of a 1% cholesterol diet (HC) vs. a no-cholesterol diet (NC) during the first 2 mo of life on pigs selectively bred for leanness or obesity. Three lean and three obese pigs received the no-cholesterol diet, and four lean and four obese pigs received the 1% cholesterol diet from d 1. Lean and obese pigs fed the no-cholesterol diet showed no increase in serum lipid concentrations, nor did they develop atherosclerosis. Obese pigs fed the 1% cholesterol diet developed significantly higher serum total cholesterol (TC) and high density lipoprotein cholesterol (HDL-C) at 35 d than lean pigs fed the 1% cholesterol diet. By d 55, only HDL-C remained significantly higher in the obese pigs, resulting in a higher (P < 0.1) TC/HDL-C ratio in the lean pigs. Atherosclerotic plaque formation in the aorta was more extensive in the lean pigs. Cholesterol synthesis measured in vivo and at termination was equally suppressed in lean and obese pigs fed the 1% cholesterol compared with pigs fed the no-cholesterol diet. We conclude that genetic differences in the response of these lean and obese pigs to a high cholesterol diet render obese pigs less susceptible to atherosclerosis despite higher serum TC concentrations. The persistent elevation of HDL-C in obese pigs is the most likely mechanism of protection.

Severe protein deficiency and repletion alter body and brain composition and organ weights in infant pigs.

Three-wk-old genetically lean or obese pigs were used in two experiments to determine the changes in body composition, visceral organs and brain in response to severe protein deficiency. In Experiment 1, 16 obese pigs were fed an adequate (A, 21% protein, 3% fat) or a protein-deficient (D, 5% protein, 23% fat) diet for 7 wk. One-half of each group was killed at 7 wk, and the remainder of each group was fed the A diet for an additional 8 wk. At 7 wk, pigs fed D contained a higher percentage of fat than those fed A (P < 0.01); after 8-wk of repletion, body composition of the two groups was similar. Duodenum, jejunum, and ileum of the protein-deficient pigs had severely atrophic villi, submucosal edema, and atrophic muscle layers; after 8 wk of repletion, however, microscopic architecture of the gastrointestinal tract was restored to normal. Absolute cerebrum weight at 7 wk, but not after 8 wk repletion, in the pigs fed D were significantly less than in pigs fed A, indicating reduced brain cellularity after 7 wk of protein restriction, but not after 8 wk repletion. In Experiment 2, genetically obese (O, n = 8) and lean (L, n = 8) pigs consumed the A or D diet ad libitum for 10 wk. L and O pigs responded similarly to protein deficiency; D pigs were fatter than A pigs and plasma constituents, bone mineral content, bone mineral density and most organ weights revealed no interactions between diet and genotype. The pig model system used in these experiments enabled the isolation of protein deficiency from infectious disease, parasites and social environmental stimulation that may confound interpretation of human infant malnutrition experiments. The data suggest that genetically controlled body fatness is not a major determinant in the response of the infant pig to severe protein deficiency.

Administration of porcine somatotropin by daily injection: growth and endocrine responses in genetically lean and obese barrows and gilts.

Influences of genotype and sex on responses to porcine somatotropin (pST) administered by daily injection were examined in genetically lean and obese gilts and barrows. Pigs (59 +/- 1.4 kg BW, eight per pST dose x line x sex) were injected daily with pST at doses of 0, 2, and 4 mg/d for 6 wk. Administration of pST induced dose-dependent decreases in feed intake and rate of backfat deposition, whereas rate and efficiency of gain were increased in a quadratic manner indicating that 4 mg of pST/d approached the optimal dose. These live measures of growth were also influenced (P < .05) by sex and line. Line, sex, and pST dose effects (P < .05) were noted for most offal components and carcass components. Quantity of lean and bone in the ham was increased (P < .01) and that of fat decreased (P < .01) with dose of pST. Throughout the trial pST induced increases (P < .05) in serum concentrations of IGF-I, IGF-II, insulin, and glucose and decreases in urea nitrogen. Concentrations of pST 24 h after injection were lower (P < .05) in pST-injected pigs than in buffer-injected pigs, indicating negative feedback on endogenous pST secretion. The pST-induced increases (P < .05) in insulin, IGF-I, and IGF-II and the decrease in urea nitrogen were evident at 24 h after the initial injection. Although pST administration improved the growth performance and composition of lean and obese barrows and gilts, the influences of line and sex were not expunged by administration of pST.