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Nutrients, such as dietary lipids, can influence development of the central nervous system [1, 2]. Particularly, an increase in plasma concentrations of cholesterol, which is an essential constituent of all animal cells (especially of brain) and abundant in milk, is positively associated with enhancement of cerebrum weight gain and behavioral development [2–4]. Additionally, docosahexaenoic acid (DHA) is a component of complex lipid in membranes, nerve insulation, as well as a precursor for signaling molecules (including prostaglandins). The availability of long-chain polyunsaturated fatty acids, including DHA, also modulates eicosanoid metabolism and myelination during growth spurt of the brain [5,6]. Interestingly, dietary DHA supply enhances visual and neurological development both in prematurely born infants [7] and in term infants [8,9], while promoting problem-solving and childhood intelligence [10]. The beneficial influences of dietary cholesterol and DHA on brain development are currently interpreted as modification of the membrane structure and functions of membrane-associated proteins [11]. Nitric oxide (NO), synthesized from L-arginine by NO synthase (NOS), plays an important role in development and function of the brain [12]. All isoforms of the NOS [neuronal NOS (nNOS), endothelial NOS (eNOS), and inducible NOS (iNOS)] are present in neurological tissue. Of particular interest, nNOS activity is decreased when the protein is phosphorylated at the inhibition site of Ser 852, whereas eNOS activity is increased when the enzyme is phosphorylated at the activation site of Ser 1177 [12]. GTP-CH activity, Tetrahydrobiopterin (BH4), which is synthesized from GTP via the GTP cyclohydrolase I (GTP-CH) pathway [13], is an essential cofactor of NOS [14]. NO is a potent signal that regulates many physiological processes affecting behavior and cognitive function, including synaptic plasticity during long term potentiation and depression [15]. NO also acts as a retrograde messenger to stabilize or refine synapse during development, as a regulatory second messenger involved in the control of brain blood flow, and as an agent that contributes to both brain degeneration and neuropotection [16]. Additionally, NO promotes angiogenesis, redox state, cell immunity, and neuronal survival [14,17]. Cholesterol and DHA are known to regulate NO synthesis in vascular endothelial cells [17]. We hypothesized that dietary supplementation with cholesterol and DHA can influence the arginine-NO pathway in the brain of neonatal animals. This hypothesis was tested with piglets by measuring NOS activity, total and phosphorylated levels for the three NOS isoforms, as well as concentrations of arginine, BH4 and NADPH in brain. To determine whether the effects of DHA and cholesterol are specific to the neuronal tissue, we also analyzed the above parameters in skeletal muscle and liver.

Cholesterol and docosahexaenoic acid (DHA) are important nutrients for neural development of infants. However, little is known about the effect of cholesterol or DHA on concentrations of amino acids (AA) in neonatal tissues. This study was conducted with the piglet (an established model for studying human infant nutrition) to test the hypothesis that dietary supplementation with the lipids may modulate AA availability in tissues. Sixteen newborn pigs were nursed by sows for 24 h and then assigned to one of four treatment groups, representing supplementation with 0.0% (control), 0.2% cholesterol, 0.2% DHA, or cholesterol plus DHA to the basal milk-formula. All piglets were euthanized at 49 days of age. In brain, cholesterol supplementation reduced (P < 0.05) concentrations of glutamate, serine, glutamine, threonine, β-alanine, alanine, methionine, isoleucine, leucine, and γ-aminobutyrate but increased (P < 0.05) concentrations of glycine and lysine, whereas DHA supplementation similarly affected (P < 0.05) concentrations of the same AA (except for isoleucine and lysine) and taurine. In addition, concentrations of most AA in liver, muscle and plasma were substantially altered by dietary supplementation of cholesterol and DHA in a tissue-dependent manner. Further, DHA reduced concentrations of carnosine in skeletal muscle, as well as ammonia in both plasma and brain. The results reveal that cholesterol and DHA can regulate AA metabolism and availability in various tissues of piglets. These novel findings have important implications for designing the next generation of infant formula to optimize neonatal growth and development.

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.

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.

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.

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.

Sixty-eight neonatal female pigs from populations selected for high (HG) or low (LG) plasma total cholesterol were used in two experiments to test the hypothesis that dietary cholesterol deprivation during the first 4 or 8 weeks of postnatal life increases plasma total cholesterol and exacerbates early aortic atherogenic lesions following free access to a high fat (15 g/100g)-high cholesterol (0.5 g/100g) diet from 4 or 8 weeks to 5 or 6 mo of age. Pigs were removed from their dam at one d of age and given free access to a modified sow-milk replacer diet containing 0 or 0.5% crystalline cholesterol. In each experiment, half of the HG and LG pigs were fed a sow-milk replacer diet containing 0 cholesterol and half were fed the same diet containing 0.5% added cholesterol. All pigs (except HG and Lg pigs in experiment 2 deprived of cholesterol throughout) were fed a 15% fat-0.5% cholesterol diet from 57 d to 6 mo (experiment 1) or 5 mo (experiment 2) of age. Overall total cholesterol and high density lipoprotein cholesterol were greater in HG than in LG pigs (P

Twenty-eight young adult boars (age 7 to 8 mol genetically selected for four generations for high (HG) or low (LG) plasma cholesterol were studied to assess dietary and genetic effects and their interactions on cholesterol metabolism. Boars within a genetic group were paired according to their plasma cholesterol concentration at 8 wk of age and were fed for 15 wk (2.7 kg/d) one of two diets (16.5% fat and 1,156 mg of cholesterolkg diet, HD; or 3.1% fat and 0 cholesterol diet, LD) in a 2 x 2 factorial arrangement. Plasma total cholesterol ( P < .O 1) and HDL- cholesterol ( P < .O 1) concentrations were higher in boars fed HS (P < .01) and in HG boars (P < .01). There was a trend toward a diet x genotype interac- tion for plasma HDL-cholesterol ( P < .06). Plasma insulin concentration tended to be lower in boars fed HD (P < .09) or HG boars (P < .lo). There was a diet x genotype interaction for plasma glucagon ( P < .04) concentration and a trend toward an interaction for insulin (P < .07). After 15 wk, all boars were killed by electrocution and exsanguination and measurements were taken. Backfat thickness was greater ( P < .01) and carcass length ( P < .Ol) and weights of the four lean cuts (P < .02) were lower in LG than in HG boars. No microscopic atherosclerotic plaques were observed in aorta or coronary arteries. Cholesterol concentration in subcutaneous fat was lower (P < .04) in LG boars, suggesting that cholesterol content of depot fat can be reduced by genetic selection in swine.

People who supplement their diets with extra zinc usually have potentially harmful changes in lipoprotein metabolism. Because zinc can interfere with copper metabolism and copper deficiency has produced similar changes in lipid metabolism in animals and people, the hypothesis that lipid alterations from high zinc intakes are accompanied by changes in copper metabolism was tested. Progenies of swine fed a high zinc (5000 mg/kg diet) or normal zinc (150 mg/kg diet) diet during pregnancy and lactation were weaned to practical diets of natural products containing similar amounts of zinc. Concentrations of apoprotein A-I (p

Comprehensive information on the composition of the whole spectrum of essential inorganic elements in sow milk is very limited. The objectives of this study were to measure concentrations of major and trace mineral elements in milk of third-generation sows selected for high (H) or low (L) serum cholesterol concentrations at 8 wk of age and to determine correlations between concentrations of milk cholesterol and major and trace mineral elements in sow milk. Twenty-one H and 21 L and 8 contemporary unselected control (U) Chester White x Landrace x Large White x Yorkshire crossbred sows were milked on d 20 or 21 of their first lactation. A standard corn and soybean meal-based diet was fed to all sows during pregnancy and lactation. There were no differences among the sow groups in milk concentrations of Ca, K, Mg, Na, and P, indicating that the genetic selection for serum cholesterol did not affect major mineral contents of the milk. Concentration of S in milk of the H sows was significantly (P < .05) higher than that of the U sows. Effects of genetic group were significant for concentrations of B, Al, Cu, and Mn in the milk, but not for Mo and Zn concentrations. Milk cholesterol concentration was negatively correlated with milk Al (P < .05), B (P < .01), and Mn (P < .05) for pooled data; there was no relationship between milk cholesterol concentration and that of other mineral elements.

Three generations of selection for 56-d blood cholesterol concentrations were used to establish low and high cholesterol lines of pigs in which cholesterol concentrations differed by 39% in the last generation. Litter size (number of fully formed pigs born per litter) diverged with each successive generation of selection and, at the third generation, litter size differed between the low and high line by two pigs (high line = 8.5 +/- .6; low line = 10.5 +/- .5; P < .05). A random selection of offspring (gilts, n = 109; boars, n = 46; barrows, n = 94) from the third generation and a control line maintained throughout the experiment were monitored for hormonal and anatomical relationships that might provide insight into the mechanisms that altered fecundity. Ovulation rate (number of corpora lutea) as determined on d 60 of pregnancy was increased in the low (n = 29) compared with the high cholesterol line (n = 38; 11.8 +/- .3 vs 9.8 +/- .3, respectively; P < .05), and litter size continued to be increased in the low cholesterol line (P < .05). No differences were noted between lines in kidney, ovarian, or total corpora lutea weight. Empty uterine weight and adrenal weight were increased in the high cholesterol line (P < .05) in randomly selected offspring of the third generation, and liver weight increased in the low line (P < .05). Associated with increased concentrations of cholesterol were increased serum concentrations of progesterone (gilts) and testosterone (boars) in the high cholesterol line (P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)

We determined the relationship of BW at birth, weaning (4 wk of age), and 8 wk of age to serum total cholesterol (C), high-density lipoprotein-cholesterol (HDL-C), and triglycerides (TG) at 8 wk of age in pigs, from the fourth generation that had been selected for low (10 litters, 75 pigs, LC) or high (10 litters, 63 pigs, HC) C at 8 wk of age. Mean C concentration at 8 wk of age was 81 +/- 30 mg/dL for LC groups and 136 +/- 19 mg/dL for HC groups. Serum C, HDL-C, and TG concentrations were not correlated with birth weight, suggesting that the physiological factors that may cause reduced weight gain in older animals are not operative in newborn pigs. All three constituents were correlated (P < .05) with BW at weaning and at 8 wk. However, only 4% of the variation in weight at weaning and 7% at 8 wk could be explained by a relationship with serum TG. There was a positive correlation between C and BW at 8 wk (r = .46, P < .05), which was apparent within the subgroups of LC and HC females and LC males (r = .46, .48, .68, respectively); the correlation was low (r = .26) in HC males.

Two identical trials, each with 128 crossbred weanling barrows (6.8 +/- .2 and 7.6 +/- .2 kg for Trials 1 and 2, respectively), were conducted. In each trial, pigs were allowed to consume ad libitum a 16% CP corn-soybean meal basal diet (B), B + 55 ppm of carbadox, B + 250 ppm of copper (Cu), or B + 125 ppm of Yucca shidigera extract for 56 d (four pens/diet; eight pigs/pen). At d 56 of the test, eight pigs/diet (two pigs/pen) were slaughtered for carcass and viscera measurements. Data of carbadox treatment in Trial 1 are excluded from this paper because of an error in mixing of the diet. In Trial 1, during the test period from d 0 to 28, pigs fed Cu had greater (P .05) compared with those fed B. During the period from 29 to 56 d, ADG was similar among pigs fed different diets (P > .05) but ADFI was affected (P Cu > B). No differences (P > .05) among diets were detected for gain/feed (G/F) and visceral weights expressed as a percentage of slaughter BW. In Trial 2, during the first 28 d, the ADG, ADFI, and G/F responses of pigs to Cu, yucca extract, and B were similar to those observed in Trial 1.(ABSTRACT TRUNCATED AT 250 WORDS)

Chronic cannulas were placed in the hepatic portal vein, ileal vein, and carotid artery in seven crossbred growing gilts trained to consume once daily 1.2 kg of a 16% CP corn-soybean meal diet. Eleven days after surgery, each pig (37.4 kg BW) was placed in an open-circuit calorimeter and its cannulas were connected to a system for determining portal absorption of nutrients. The whole-animal heat production and net portal absorption of gut VFA were measured simultaneously for 12 h after the pig was fed 1.2 kg of feed. Plasma concentrations of VFA, including acetic, propionic, isobutyric, butyric, isovaleric, and valeric acids, in portal and arterial samples were determined by gas chromatography after a cleanup by ion-exchange chromatography. The net portal absorption of VFA was calculated by multiplying the porto-arterial plasma concentration difference of the VFA by portal vein plasma flow. Plasma flow was estimated by the indicator-dilution technique using p-aminohippuric acid as the indicator. The energy value of absorbed VFA was the sum of products of each individual VFA multiplied by its corresponding value of the heat of combustion. The mean hourly energy value of absorbed VFA during the 12-h postprandial period was .65 +/- .03 kcal.h-1.kg BW-1. The mean hourly whole-animal heat production was 2.70 +/- .04 kcal.h-1.kg BW-1. Thus, in our 37.4-kg pigs, which were trained to consume 1.2 kg of a 16% CP corn-soybean meal diet once daily, the gut VFA absorbed into the portal vein could contribute 23.8 +/- 1.1% to whole-animal heat production if all of the absorbed VFA were combusted to CO2.

Three four-way cross (Chester White × Landrace × Large White × Yorkshire) female pigs from each of twelve litters were used. One pig from each trio remained with its primiparous dam and its other littermates to age 28 d. Two pigs from each trio were removed to individual boxes at age 24 to 36 h and fed liquid sow-milk substitute containing low cholesterol (14 mg/100 g) or high cholesterol (151 mg/100 g) to age 28 d. All pigs were weaned to a dry diet containing 182 mg cholesterol/100 g to age 12 wk and 115 mg cholesterol/100 g from age 12 wk to 20 wk. Carcass measurements and organ weights were recorded at slaughter (20 wk) and liver was analyzed for cholesterol. Body weights were recorded weekly to 28 d and bi-weekly thereafter; serum total cholesterol was determined on d 1, 28, 56, 84, 112 and 136. Sow-reared (SR) pigs were heavier (P

To test the hypothesis that maternal protein deprivation in early pregnancy retards body and organ growth of 63-d (midterm) pig fetuses, 16 primiparous domestic four-way crossbred swine were fed a diet adequate in protein (13% protein) (A) or a protein-restricted (0.7% protein) diet (PR) from d 1 to 63 of pregnancy or to parturition. Maternal body weight, plasma protein, hematocrit, and heart and spleen weights were reduced, and indices of body fatness were increased by the PR diet. Fetal body weights were reduced and fetal placental weights were increased at d 63 by protein restriction. Length from crown to rump and weights of liver, kidney, gastrointestinal tract, and cerebrum were lower in PR than in A fetuses. Concentrations of protein, RNA and DNA in liver, cerebrum and longissimus muscle were unaffected by maternal diet, but total amounts of all three constituents in liver and cerebrum were lower in PR than in A. Relative organ weights were similar in A and PR fetuses except that kidneys and gastrointestinal tract were greater in A fetuses. Newborn body weights and absolute organ weights were generally lower in PR than in A, but relative weights were similar. The observed reduction in body and organ weights and amounts of protein, RNA and DNA in 63-d fetuses and newborn progeny of PR swine establishes that the stunting effect of maternal protein restriction can be initiated by midterm, preceding the period of most rapid accretion of body tissues during prenatal life in the pig.

Chronic cannulas were placed into the hepatic portal vein, ileal vein and carotid artery of growing pigs trained to consume their daily allowance of 1.2 kg of feed (16% protein corn-soybean meal basal diet) in a single meal. The average preoperative BW of pigs was 44.7 kg for Trial 1 (three pigs) and 35.3 kg for Trial 2 (seven pigs). In Trial 1, net absorption of ammonia (NH3) and glucose into the portal vein was determined three times at weekly intervals. The net portal absorptions were derived by multiplying the porto-arterial plasma concentration difference of NH3 and glucose by portal vein plasma flow rate estimated with the p-aminohippuric acid indicator-dilution technique. Differences in the net portal absorptions of NH3 and glucose among the three weekly measurements were small (P greater than .05). In Trial 2, the first sequence of net portal absorption measurements was conducted when pigs were fed the basal diet, and the second sequence of measurements was conducted after the pigs had been fed the diet supplemented with 55 ppm of carbadox for 7 d. Carbadox supplementation reduced (P less than .05) plasma NH3 concentration in portal plasma during the 2.5-h to 5-h postprandial period and decreased (P less than .05) net portal absorption of NH3 during the 2.5-h to 4-h postprandial period. Carbadox, however, did not affect (P greater than .05) net portal absorption of glucose. We suggest that carbadox suppresses the production of cell-toxic NH3 by intestinal microorganisms and, thus, reduces the injury and turnover of intestinal cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Thirty-two castrated male crossbred growing pigs (average initial wt 26.9 kg) were used to determine the effect of a high level of dietary protein (37%) compared with a normal level of protein (15%) on enterobacteria and Campylobacter sp. inhabitation in the large intestine and on visceral organ hypertrophy and the interrelationships between these two factors. Pigs were kept in pairs (eight pens of two pigs/diet) and fed their respective diets and libitum. Eight pigs (two pens of two pigs fed each diet) were killed at wk 4, 8, 12 and 16 without fasting. Fecal samples were obtained every 2 wk from animals scheduled for necropsy at 16 wk, and colon contents were obtained from all pigs at necropsy; samples were enumerated individually for enterobacteria and Campylobacter sp. Weights of heart, lungs, liver, kidneys, perirenal fat and empty stomach, small intestine and large intestine were recorded at necropsy. Stomach, cecum and proximal colon were sectioned for histopathologic examination. Daily body weight gain was depressed by high dietary protein, but liver and kidneys were heavier in the high protein group than in controls at each time interval. Mild lymphoid hyperplasia of Peyer's patches in the small intestine in some pigs in both groups was indicative of antigenic stimulation but not of pathologic significance. There was no effect of diet on counts of enterobacteria or Campylobacter sp. in feces or colon contents during the 16-wk experiment. We conclude that the hypertrophic response of the tissues of growing pigs to high dietary protein is not the result of the presence of Campylobacter sp. or enterobacteria in the colon contents.

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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.

In Chapter 3, it was stated that the genetic aspects of the production system set both the limits and potential for performance of the system. The breeding stock input into the system introduces potentials for animal performance but these are not usually exceeded (experimental lean growth promotants such as ractopamine and somatotropins do increase lean growth potential above that expressed without their use). In this chapter, we will examine alternative breeding systems to provide that input, tools available to the breeder and producer to improve the potential for that input, and the evolution of genetic improvement tools from the traditional showring-based visual appraisal approach to modern computer-based performance testing and genetic evaluation procedures.

Various aspects of growth are covered in other chapters, but because it is such an important topic, it is discussed more directly here. The characteristic S-shaped growth curve of all biological systems, whether it be an increase in weight gain of a plant or animal or increase in number of yeast cells in a population (Brody 1945) is shown in Fig. 5.1. The term growth, as applied to animal production, is often considered to be synonymous with increase in body weight of the animal from conception to maturity. Brody (1945) has defined growth as “the constructive or assimilatory synthesis of one substance at the expense of another (nutrient) which undergoes dissimilation.” The energetic efficiency of growth as just defined is, therefore, the energy stored in the animal per unit of energy consumed. The pig is especially efficient in growth, in comparison with other farm animals. Detailed discussion of the energetic efficiency of growth in meat-producing animals has been provided by Webster (1980). The complex metabolic and endocrine aspects of tissue and animal growth are exciting areas of animal biology and have been reviewed by Trenkle and Marple (1983>) and in a symposium, Concepts of Animal Growth (American Society of Animal Science, 1988).

A high reproductive rate is essential in a successful purebred or commercial swine enterprise. A knowledge of the normal anatomy and physiology of the female and male reproductive tract is fundamental to the achievement of a high reproductive rate of swine. In this chapter, the following topics are discussed: anatomy of the female and male reproductive tracts, puberty, the estrous cycle, ovulation, factors affecting ovulation rate and time of estrus, movement and survival of sperm in the female reproductive tract, conception rate, duration of gestation, uterine capacity, parturition, male puberty and sexual behavior, composition of semen, sperm survival and storage, artificial insemination, and potentially important techniques, though presently in limited use, such as embryo transfer, artificial control of the estrous cycle, superovulation, and storage of sperm by freezing. Each of the above subjects is of significance in the total picture of reproduction. Overviews of current knowledge of male and female reproduction in swine are recommended (Dziuk 1977; Dziuk and Bellows 1983; Bazer and First 1983; Amann and Schanbacher 1983; Kirkwood and Aherne 1985; Christenson 1986).

Seventy-two castrated male four-way composite (Chester White x Landrace x Large White x Yorkshire) weanling pigs (17 kg initial BW) were used to determine the compensatory response of specific organs and whole body following a 3-wk period of restricted energy intake imposed by ad libitum-feeding an 80% alfalfa meal diet or pair-feeding an adequate corn-soybean meal diet to attain equal weight loss. Six pigs were killed at d 0 to provide baseline data. Six pigs from each diet group (control, C; alfalfa, A, restricted, R) were killed at d 21, after which all remaining pigs were fed C ad libitum to 35 d, 105 d or 126 d. Six pigs per group were killed at 35 and 105 d and four per group were killed at 126 d. Organ weight and carcass data were recorded for all pigs at all time intervals. Regression of organ and trimmed lean tissue weights on time was tested for linearity (d 1 to 126 for C and d 21 to 126 for A and R except d 35 to 126 for gastrointestinal tract traits for A and R); differences in organ weights between C, A and R at d 21 and d 35 were tested by a two-way analysis of variance. There was no evidence of a compensatory growth response to dietary energy restriction for 21 d except for rate of change in weights of liver and kidneys and backfat depth from 21 to 126 d and of gastrointestinal tract components from 21 to 35 d. Specific organs may exhibit compensatory growth over different time spans in young pigs in the absence of observable weight compensation at the whole-animal level.

Thirty-six four-way cross (Chester White X Landrace X Large White X Yorkshire) growing barrows and gilts were used to investigate the effects of replacing graded levels of protein from soybean meal with equivalent levels of protein from rubber seed meal in 16% CP semipurified diets on the performance characteristics, hematocrit, plasma metabolites and N utilization of pigs. The first diet (control) was largely cornstarch-soybean meal in which the soybean meal supplied all of the CP. In other diets, rubber seed meal replaced 10%, 20% and 30%, respectively, of the protein of soybean meal in the control diet. Twenty gilts were used in a 28-d growth trial and 16 barrows were used in an 8-d digestion trial (4-d collection). There were no differences (P greater than .05) in ADG, ADF intake and in the feed:gain ratios, even though there was a trend for lower ADG and gain:feed ratio as the level of rubber seed meal increased in the diet. There were no differences in hematocrit, but plasma protein and albumin tended to be depressed when rubber seed meal provided more than 10% of the dietary protein. Apparent digestibilities of GE, DM and N were lower with rubber seed meal at 20% of the protein than with any other diet, but apparent N retained and the percent of digested N retained were not depressed significantly (P greater than .05). Although rubber seed meal protein is of poorer quality than soybean meal protein for growing pigs, at least 10% of dietary protein can be provided by rubber seed meal without adversely affecting growth and N utilization.

Three experiments were conducted with 96 growing Landrace × Yorkshire × 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 (P i ) 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% P i ). 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

Twenty-four genetically obese and 24 lean barrows were allotted within genotype to either a 16% CP corn-soybean meal basal diet, the basal + .69 ppm cimaterol or the basal + 1.38 ppm cimaterol. Pigs had ad libitum access to their diets from 59.3 kg to 104.5 kg body weight. No genotype x cimaterol interactions were detected (P greater than .05). Neither genotype nor cimaterol supplementation had any effect (P greater than .05) on average daily weight gain or gain-to-feed ratio. Compared with lean pigs, obese pigs had higher fasting plasma urea nitrogen (BUN), a smaller gastrointestinal tract and a greater dressing percentage with a shorter and fatter carcass (P less than .05). Cimaterol produced a higher fasting plasma BUN, a greater dressing percentage with a leaner carcass and a higher shear force value for loin chops (P less than .05). Cimaterol also tended (P less than .10) to increase heart weight. However, no difference was observed in these measurements between pigs fed .69 or 1.38 ppm cimaterol. In lean pigs fed the basal or .69 ppm cimaterol diet, there was no difference (P greater than .05) in the 8 to 24 h postprandial whole-animal heat production. Cimaterol effectively decreased fat deposition and increased lean accretion both in genetically obese and in lean pigs; there were no differential responses to cimaterol in pigs with different propensities to deposit body fat.

Crossbred (Chester White X Landrace X Large White X Yorkshire) primiparous gilts were fed a standard gestation diet at 6,000 or 2,000 kcal calculated digestible energy (DE; 1.8 or .6 kg feed) daily for 84 or 108 (106 to 112) d after mating. Nonpregnant littermates were matched by body weight and assigned to the same diet treatments. Body weight and ultrasonic backfat measurements were made at 3-wk intervals. At 77 and 100 d, eight pregnant gilts (four control and four restricted) were fitted with indwelling jugular cannulas for frequent blood sampling (33 times over an 8-h period) to determine plasma glucose and growth hormone concentrations. At 84 and 108 d all gilts (eight pregnant and eight nonpregnant at d 84 and nine pregnant and nine nonpregnant at d 108 for each diet) were slaughtered and internal organs and reproductive tracts were removed and weighed. Fetal body and organ weights were recorded and an umbilical artery blood sample was removed from fetuses for plasma glucose, growth hormone, total protein and albumin measurements. The results demonstrated the ability of the primiparous gilt to maintain pregnancy through 106 to 112 d of gestation while consuming one-third (2,000 kcal DE daily) of recommended daily feed. Fetal weight at 84 and 108 d was reduced by about 13% without affecting litter size in gilts fed severely restricted intakes. Absolute and relative weights of maternal organs were affected by severe feed restriction, and backfat was reduced but there was no evidence of "pregnancy anabolism" in either adequately fed or restricted gilts. Fetal liver, kidney and gastrointestinal tract weights were reduced by maternal feed restriction; relative kidney weights were reduced while relative brain cortex weight was increased by maternal restriction. Maternal plasma glucose was unchanged by pregnancy or feed intake while plasma growth hormone peak amplitude, but not mean concentration or number of peaks, was increased by feed restriction. Fetal plasma glucose increased with time and in response to severe maternal feed restriction while plasma total protein and albumin decreased. Plasma growth hormone declined with time and was negatively correlated with fetal body weight.

Aquatic weeds from Cayuga Lake in New York were included as 10% or 20% dry weight of rations which were fed to growing pigs for 69 days. The animals gained weight at a rate comparable to those on a basal diet or a diet in which an equivalent weight of alfalfa replaced the aquatic plants. The feed efficiency (kg ration consumed/kg wt gained) of the aquatic rations was significantly lower, probably because of the lower nutritive value of the aquatic plants. Polychlorinated biphenyls (PCBs) were found in the aquatic plants (0.59 ppm, dry weight) and in the pig fat of those fed the aquatic ration. Hepatic microsomal mixed function oxidase activity was not significantly different in the animals fed the various treatment rations. Histopathologic examination of animal tissues revealed no lesions or abnormalities which could be attributed to the diets.

The effects of feeding restricted energy or restricted protein on blood constituents were studied in pregnant gilts. Gilts fed the protein-restricted diet through out gestation had lower hemoglobin, serum protein and serum albumin levels from week 10 to parturition, indicating depletion of labile protein reserves of the protein-restricted gilts to satisfy fetal requirements. The protein-restricted gilts (PR) developed edema between the hindlegs and around the vulva probably due to the low serum protein and albumin concentrations. There were no significant differences among groups in blood glucose and plasma FFA and all groups showed a significant rise in blood glucose after week 10. A reduced sensitivity to insulin occurring during pregnancy could account for this significant increase in glucose. Birth weight was significantly lower in PR group compared to control (C) and energy-restricted (ER) groups. It appears that changes in blood glucose and plasma FFA are not sensitive indices of energy needs in energy- or protein-restricted pregnant gilts and that only dietary protein deprivation affects blood hemoglobin, urea nitrogen, serum protein and albumin concentrations. J. Nutr. 104: 1033-1040, 1974.

Growing Sprague-Dawley female rats were used to compare the effects of feeding corn diets containing rubber-seed meal (RSM), soya bean meal (SBM) or casein (CA) on their performance characteristics, relative organ weights, hematocrit and some plasma metabolites in a 21-day experiment. The 30 rats used were randomly divided into 5 equal treatment groups of 6 rats, kept in individual cages and fed 5 different 12% protein isocaloric diets consisting of corn plus (1) RSM, (2) RSM + lysine + methionine, (3) SBM 1, (4) SBM 2, and (5) casein + methionine. All diets supplied equal proportions of protein from corn and protein sources (6.7:5.3, corn:protein source) except Diet 4 which had a ratio of 7.5:4.5. Rats fed RSM Diet 1 had significantly lower daily gains (ADG), higher feed:gain ratios, and lower relative liver weights, total plasma protein, plasma albumin, and protein efficiency ratios (PER) than the rats fed all the other diets ( P P > 0.05) for HCT, plasma urea N or cholesterol. The diet which contained casein plus 0.2% DL methionine did not significantly improve any of the traits measured as compared with SBM diets, but it did significantly improve the total plasma protein and reduced liver weight relative to Diet 1. It is concluded that growth performance of rats fed a corn-RSM diet is inferior to that of rats fed a corn-SBM diet and that supplemental methionine and lysine in RSM diets promoted performance similar to that obtained with SBM.

Genetically obese (O) or lean (L) primiparous gilts were assigned on the day of mating to an adequate [control (C) or restricted (R)] intake of feed. Body weight and ultrasonically estimated backfat depth were recorded at wk 0 (mating), 4, 8, 12 and 16 of pregnancy, and at d 2-3, 21 and 28 of lactation. Number of pigs born, survival rate to 28 d of age and piglet body weight at 0, 14, 21 and 28 d of age were recorded. Four male and four female progeny from each diet group of each genetic strain were slaughtered at 6 mo of age for carcass and organ weight measurements. OR and LR gilts responded similarly to feed restriction in body weight change, backfat depth and plasma traits. Body weight increased throughout gestation in OC and LC gilts but decreased about 6 kg in OR and LR gilts. Backfat remained relatively constant throughout gestation in OC and LC gilts but declined steadily in LR and OR gilts. There were no genetic group x diet interactions for any trait measured. Litter size and piglet survival were not affected by diet or genetic group, but piglet birth weight and daily gain to d 28 and to wk 25 were lower in both R groups. Backfat accretion and other indices of carcass fatness were reduced in progeny of R dams.(ABSTRACT TRUNCATED AT 250 WORDS)

Thirty-two genetically lean and obese Yorkshire X Duroc crossbred castrated male pigs were divided within genetic line into two groups at 7 weeks of age. Eight pigs within each line were fed a diet low in fat and cholesterol (maize-soybean meal diet fortified with minerals and vitamins). The other group was fed a similar diet containing added beef tallow (11%) and dried egg yolk (1%). All pigs were fed ad libitum for 4 months when one-half of each group was slaughtered. All other pigs were continued on their respective diets at a restricted level of intake for an additional 5 months at which time the protein source of two pigs in each diet group within each genetic line was changed from soybean meal to casein. After an additional 6 months on their respective diets (16 months total duration of experiment) these pigs were slaughtered. Blood samples were taken monthly or bimonthly for total plasma cholesterol and triglycerides. At slaughter, the aorta was opened, stained with Sudan IV, and the stained area traced and measured planimetrically. Only a moderate rise occurred in plasma cholesterol and triglycerides of pigs fed high fat-high cholesterol diets. Genetically obese pigs were no more susceptible to diet-induced hypercholesterolemia and to the percentage of the surface area of the aorta stained with Sudan IV than were lean pigs. It is concluded that obesity per se is not necessarily associated with development of atherosclerosis in pigs and that innate ability to metabolize high dietary cholesterol is of greater importance than body fatness in determining the response to diet.

Thirty-two genetically lean and 32 genetically obese weanling (4 to 5 wk old) pigs from inter se matings of crossbreds produced by within-line matings of Duroc and Yorkshire breeds, selected for low or high backfat, were fed the following four diets for 8 wk (eight lean and eight obese pigs/diet): 10% protein -- 100 ppm Zn, 10% protein -- 200 ppm Zn, 18% protein -- 100 ppm Zn, 18% protein -- 200 ppm Zn. After 8 wk, all pigs were fed a standard 16% protein corn-soybean meal-type growing diet to a slaughter weight of about 87 kg. Lean pigs were more severely affected than obese pigs by low protein diets as measured by weight gain, plasma total protein and plasma albumin. Plasma Zn concentration was reduced in lean and obese pigs fed low protein diets. Supplemental Zn failed to increase plasma Zn in protein-deficient pigs. During repletion, weight gain of lean and obese pigs previously fed the 10% protein -- 100 ppm Zn diet was less than that of pigs previously fed other diets. The lower level (100 ppm) of Zn fed during protein depletion appeared to be associated with a negative effect on repletion weight gain of lean and obese pigs. Lean and obese pigs responded similarly during the repletion phase to earlier protein restriction. We conclude that supplementary dietary Zn does not maintain plasma Zn concentration in growing pigs fed protein-deficient diets and that repletion from dietary protein restriction is not associated with compensatory growth in genetically lean pigs.

Genetically obese and lean pigs were fed isonitrogenous-isoenergetic (digestible energy) amounts of a high or low fat diet from 25 kg body weight. Obese pigs gained less and required more feed per unit gain than lean pigs. Lean pigs were more muscular with less fat than obese pigs. Obese pigs utilized more dietary amino acids for energy (greater plasma urea N) than did lean pigs. Weight gain was similar at all intermediate periods in obese pigs fed the two diets. However, gain tended (P less than or equal to .10) to be greater and the ratio of dietary energy intake to gain tended (P less than or equal to .10) to be less in obese pigs fed high compared with low fat diets. Similar results were observed in lean pigs fed the two diets. The high fat diet produced more carcass adipose tissue deposition in both strains after 20 wk of feeding (detectable by ultrasound at 14, but not at 7 wk). Adipose tissue lipogenic rate (glucose incorporation) was similarly depressed by fat feeding in both obese and lean pigs. Obese and lean pigs both utilized dietary carbohydrate and fat differentially but there was no indication of genetic divergence regarding this utilization. In both strains of pigs, energy from the fat-enriched diet was preferentially partitioned into carcass adipose tissue.

Five experiments were done with 34 weanling and 24 growing crossbred gilts. Individually penned pigs were fed ad libitum (expt 1) or pair-fed (expt 2 through expt 5) for either 2 (expt 1 through expt 4) or 3 (expt 5) wk. Mean body weight gain and gain/feed values were significantly (P less than 0.05) greater in pigs fed carbadox (a synthetic antimicrobial). Fasting O2 consumption and CO2 production of pigs were measured during the 32- to 48-h (expt 1, 4 and 5) or during the 24- to 40-h (expt 2 and 3) postprandial periods with indirect open circuit calorimeters. Carbadox reduced O2 consumption significantly (P less than 0.05) in expt 2, but had no significant effect on CO2 production in any of the five experiments. The weight of thyroid gland and the plasma concentrations of L-3,3',5-triiodothyronine (T3) and thyroxine (T4) of pigs were not altered by carbadox. The mean weight, but not the length, of small intestine tended to be less in pigs fed carbadox. It is suggested that the growth-promoting effect of carbadox on young pigs may be associated with the weight of small intestine and its physiological processes such as metabolic rate. However, no definite effects of carbadox on whole-animal fasting metabolic rate and thyroid function could be demonstrated by the methods used in the present study.

Crossbred (Chester White x Landrace x Large White x Yorkshire) primiparous gilts were fed daily a corn-soybean meal-based gestation diet at 1.8 kg (C) or 0.6 kg (R) (6000 or 2000 kcal calculated digestible energy, DE) or a high-protein diet (RCal) at 0.6 kg (2000 kcal calculated DE) from day of mating to slaughter at 100 to 106 days of gestation. The RCal diet contained three times the concentrations of protein and of mineral and vitamin supplement present in the C diet. Body weight and ultrasonically estimated backfat depth were recorded at 0, 4, 8, and 12 weeks postcoitum. The results showed differential effects of form of diet restriction (R vs RCal) on body weight, backfat depth, relative and absolute uterine weight, and on relative kidney, stomach, and trimmed wholesale cut weights of the dam. Maternal and fetal plasma glucose and urea-N concentrations were higher in RCal than in R groups. Total uterus plus gastrointestinal tract relative weight, with or without fetuses, was lower in RCal than in R and C gilts. The ratio of uterus (with or without fetuses) weight to gastrointestinal tract weight was greater in R than in C or RCal gilts. The data are interpreted to indicate that restriction of carbohydrate-fat calories only compared with restriction of a standard diet throughout gestation in swine had a negative effect on uterine growth associated with repartitioning of nutrients to visceral organ and lean tissue growth at the expense of maternal uterine tissue and body fat conservation.

Number of cellulolytic bacteria and their cellulase activity were determined from fecal samples of eight pairs of littermate pigs representing four litters (26 to 32 kg) fed a low or high fiber diet ad libitum (0 or 35% alfalfa meal, respectively) over a 70-d period. Fecal samples were obtained from all pigs on d 0, 5, 11, 18, 32, 53 and a final sample between d 67 to 70. Cecum and colon samples were obtained at slaughter. Growth and carcass data were also obtained during the study. Pigs fed the high fiber diet gained 17.3% less, had increased feed to gain ratio and less carcass weight at slaughter than those fed the low fiber diet (P less than .05). Overall, a larger number of cellulolytic bacteria (P less than .05) were found in the fecal samples from pigs fed the high fiber diet. The overall mean cellulolytic activity (mg glucose released X g dry weight fecal sample-1 X 30 min-1) was 27.7 compared with 33.8 (P less than .05) for the pigs fed the low and high fiber diet, respectively. A lower concentration of organic acids (P less than .05) was present in the fecal samples of the high fiber pigs. The overall mean acetate to propionate ratio was 1.92 and 2.48 (P less than .01), and ammonia-N was 2.27 and .98 mg/g dry weight (P less than .01) for the low and high fiber diet pigs, respectively. These data indicated that a 35% alfalfa meal diet significantly affects intestinal bacterial metabolism and number and activity of the cellulolytic population, along with performance and carcass characteristics.

Five sets of littermate gilts (8.2 +/- .19 kg average initial weight) were randomly assigned within litter to a 16% protein corn-soybean meal basal diet (B), B + .308% neomycin, or B + 55 ppm carbadox. Each set was equally-fed individually once daily for 16 d in metabolism cages and 5 d in calorimeters. The average daily feed intake for 21 d was 276 g. Oxygen consumption and CO2 production were measured during an 8- to 24-h postprandial period on d 16, 19, 20 and 21, and during a 32- to 48-h postprandial period after the d 21 feeding. Pigs were killed 50 h postprandially for gastrointestinal tract measurements. Dietary supplementation of antimicrobial agents (neomycin and carbadox) resulted in improvements (P less than .01) in daily gain and efficiency of feed utilization and lower (P less than .05) small intestinal mass in pigs. There was no difference (P greater than .05) in daily gain, feed efficiency or small intestinal mass between pigs fed neomycin- or carbadox-supplemented diets. Whole-animal fasting O2 consumption and CO2 production measured during the 8- to 24-h or 32- to 48-h postprandial period were not affected (P greater than .05) by the supplementation or the source of dietary antimicrobial agents. There were no differences (P greater than .05) in 8- to 24-h fasting O2 and CO2 measurements determined on d 16, 19, 20 and 21, indicating that adaptation to calorimeters was not needed by the pigs.(ABSTRACT TRUNCATED AT 250 WORDS)

The nutrient compositions of various fermented manures were compared. Large differences in the mineral concentration were observed. There were no important differences among the amino acid composition of S. spirulina grown on the different nutrient media. All were low in methionine, but were rich in glutamic acid, aspartic acid, arginine, and leucine. The crude protein content was 71.8-60.1%. Considerable contamination of the waste-grown algae with yeast, fungi, and sporogenous bacteria was experienced.

Developmental changes in growth hormone levels during protein or energy malnutrition was studied in weaned pigs. Three or 4 week old pigs from control dams were fed a control diet (18% protein), an energy-restricted diet (18% protein) or a low protein diet (6% protein) for 8 weeks. Energy restriction was achieved by feeding the control diet in amounts that allowed very little growth. After the restriction period, all pigs were fed the control diet ad libitum for another 8 weeks. Blood samples were collected at intervals throughout the experiment and the plasma was analyzed for growth hormone by radioimmunoassay. Post weaning protein deprivation resulted in higher growth hormone levels during the restriction period as compared to control pigs or pigs with a restricted energy intake. J. Nutr. 106: 947-951,1976.