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Four 28-d trials were conducted using a total of 432 pigs, with average initial weight across trials ranging from 6.3 to 9.7 kg, to estimate the tryptophan (trials 1 and 2) and threonine (trials 3 and 4) requirements of pigs fed low protein, corn-sunflower meal diets. The effect of tryptophan, threonine and protein level on serum calcium, phosphorus and zinc also was studied. The diets contained either 12 or 13% protein and were calculated to be adequate in all nutrients except crude protein and the amino acid being investigated. A lysine supplemented, 18% protein, corn-sunflower meal diet was included in all trials as a positive control. In trial 1, weight gains of pigs increased linearly (P<.005) while feed conversion improved cubically (P<.05) as dietary tryptophan increased from .14 to .22%. Pigs fed the 18% protein diet gained faster (P<.05) and required less feed/gain than pigs fed low protein diets. In trial 2, weight gains improved quadratically (P<.005) and feed conversion improved linearly (P<.05) as dietary tryptophan increased from .104 to .204%. Serum phosphorus and zinc concentrations were lower (P<.05) in pigs fed the 18% protein diet. In both trials, serum urea N responded quadratically (P<.05) to increasing dietary tryptophan, and was lower (P<.05) in pigs that were fed diets supplemented with L-tryptophan than in those fed the low protein basal or 18% protein diets. Weight gains increased linearly (P<.05) and feed conversion improved linearly (P<.005) in trial 3 while serum urea N, daily gains and feed conversion improved cubically (P<.005) in trial 4 with increasing levels of dietary threonine. Serum urea N was lower (P<.05) in pigs fed diets containing supplmental L-threonine. Serum phosphorus and zinc were lower (P<.05) in pigs fed the 18% protein diet than in pigs that were fed all 12% protein diets. The results indicate that the minimum dietary threonine requirement of the young weaned pig (8 to 21 kg) is approximately .63%, while the minimum dietary tryptophan requirement of the 6- to 22-kg pig is approximately .16%.

Two experiments were conducted with weaned pigs to evaluate the efficacy of supplemental tryptophan, threonine, isoleucine and methionine in a lysine-fortified, 12% protein, corn-sunflower meal diet. A 16% protein, cornsunflower meal diet was included as a positive control. Both diets were supplemented to be isolysinic and to provide a level of lysine approximately 10% above National Research Council recommendations. Average initial weight of the pigs was 24 and 9 kg and the diets were fed for 28 and 35 d in Exp. 1 and 2, respectively. The addition of either tryptophan or threonine alone to the lysine-fortified, low-protein diet did not affect rate of gain or feed efficiency. However, the simultaneous addition of tryptophan and threonine resulted in improved (P<.05) weight gain and feed efficiency with performance equal to that of pigs fed the 16% protein diet. Further supplementation of this diet with isoleucine and methionine, in that order, had no effect on pig performance. The results suggest that the most limiting amino acids for growing swine in a lysine-supplemented, 12% protein, corn-sunflower meal diet are tryptophan and threonine. Blood urea N data supported this finding.

One hundred seventy-six crossbred weaned pigs (4 to 5 wk old) were used in two growth trials to determine the effect of excess arginine on pig growth and plasma amino acid levels. In the first 28-d growth trial, two lysine levels (1.03 and 1.26%) and three arginine levels (.94, 1.29 and 1.63%) were used in a nested treatment arrangement. Lysine supplementation improved daily gains (P<.05), tended to improve feed efficiency (P<.12) and caused a general reduction in plasma essential amino acid levels. Arginine had no effect on daily gain or feed intake, but pigs fed 1.03% lysine and 1.63% arginine had reduced gain/feed (P<.05). Arginine did not affect gain/feed of pigs fed 1.26% lysine. Plasma lysine levels were reduced (P<.06) by excess arginine in pigs fed 1.26% lysine, but not in pigs fed 1.03% lysine. The four treatments for the second 26-d growth trial consisted of three diets containing .92% lysine and either .72, 1.10 or 1.61% arginine and a positive lysine control (1.10% lysine, .72% arginine). Lysine was the limiting amino acid in the basal diet, but arginine had no effect on daily gain, daily feed intake, gain/feed or plasma lysine levels. Plasma threonine and methionine levels were reduced by excess arginine in both experiments, while the other plasma essential amino acid levels were not affected by dietary arginine. Conclusions are that large excesses of added arginine may affect lysine utilization, but pig performance was affected only when excess arginine was combined with a lysine deficiency. The arginine levels similar to those found in grain-soybean meal swine diets had no effect on pig performance in these experiments.

Thirty-one sows and 27 gilts were each allotted to three treatments to study the effect of water quality during gestation and lactation. Sodium sulfate was added to the water to give sulfate and total dissolved solids in ppm as follows: (1) 320, 620, (2) 1,820, 2,840 and (3) 3,320, 5,060. Water was offered ad libitumfrom about 30 days postbreeding through 28 days lactation. There were no significant differences in gestation or lactation gains and number or weight of pigs at birth or at weaning. Fecal consistency was normal in all treatments. Water consumption did not differ during gestation but increased during lactation as salt level increased. These results suggest that sulfates up to and including 3,320 ppm in water have no significant effect on reproduction in the gilt or sow.Fifty-four weaned pigs representing the above three sow treatments equally were given water with 0, 3,000 ppm added sulfate from sodium sulfate or 3,000 ppm added sulfate from magnesium and sodium sulfate in a 1:1 ratio for a 28-day period. No significant treatment differences (P<.05) occurred in average daily gain or feed to gain ratio. Scouring was more common with fecal condition less firm (P<.01) and water consumption greater (P<.05) among pigs that received water with added sulfates. No differences were observed in pigs that received water containing sodium sulfate or equal parts of sulfate from sodium and magnesium sulfate.

Three experiments were conducted with young weaned pigs to evaluate opaque-2, double mutant (opaque-2, floury-2), waxy and normal corn in pig starter diets. Rate of gain and feed/gain were similar for pigs fed the various com types in diets adequate in protein content. Opaque-2and double mutant corn contained higher lysine levels than waxy and normal corn. Feed/gain of pigs fed waxy corn in 16% protein diets Was significantly less than that of pigs fed normal or opaque-2corn in 18% protein diets. However, pigs fed 16% protein diets containing double mutant com did not differ in feed/gain from those fed the above 18% protein diets. Successive additions of lysine, methionine, tryptophan, threonine and isoleucine to opaque-2corn resulted in a significant improvement of feed/gain with lysine supplementation and a further significant improvement with threonine supplementation. Threonine also increased rate of gain significantly. No significant responses in rate of gain or feed/gain occurred with supplementary methionine, tryptophan or isoleucine additions to opaque-2corn.

Three trials were conducted to study the effect of various levels of metabolizable energy (ME) on reproductive performance of crossbred gravid sows from breeding through gestation. One-hundred-one litters resulted from 124 sow matings during two summer and one winter trials over a 1 1/2-year period. Sows were fed 1.3 kg of a basal diet with additions of corn starch to provide 4,000, 5,000, 6,000 or 7,000 kcal of ME daily.A significant linear response due to treatment was shown for 110-day gestation weight gain with gains increasing with increasing ME intake. Sow 110-day gestation weight gain was negatively correlated with 21-day lactation gain (r = −.46), indicating the tendency for sows which gain more during gestation to gain less or lose more weight during lactation.There was a significant decrease in number of live pigs born as energy levels increased from 4,000 to 7,000 kcal of ME. Number of stillborn pigs was significantly correlated with 110-day gestation gain of the sow (r = .76), indicating that increased gestation gain resulted in more stillbirths.Quadratic and cubic treatment effects for litter birth weight and a linear treatment effect for average pig weight were found. The heaviest litters were produced by sows fed 6,000 kcal, and the heaviest average pig weights were produced by sows receiving 6,000 or 7,000 kcal of ME.No differences in number of pigs weaned were observed among treatments. There was a significant quadratic effect on litter weaning weight and average pig weaning weight due to treatment. Sows fed 6,000 kcal ME daily weaned the heaviest pigs and litters.

Two trials were conducted involving 76 crossbred gilts from an initial weight of 46 kg through gestation to evaluate the effect of dietary protein on growth, development and reproduction. Isocaloric diets containing 10 and 14% protein and supplemented with equal levels of minerals and vitamins were fed at a level of 2 kg daily during growth and gestation. All gilts were bred at the third estrus with one-half of them being slaughtered approximately 25 days postbreeding and the remainder allowed to farrow.Gilts fed the 14% protein diet gained faster (P<.01) during both the development and gestation periods and were heavier and younger at breeding. There were no significant differences in number of corpora lutea or live embryos at 25 days or number and weight of pigs at birth. Total serum protein was lower (P<.05) at the end of the growing period in gilts fed the 10% protein diet but not after 25 days gestation or at farrowing.

Experiments were conducted to estimate the lysine requirement of pigs weighing 8 to 20 kg and to determine the effect of dietary lysine level during this early growth period on subsequent performance and carcass characteristics. Lysine levels in corn-soybean meal based diets ranged from .75 to 1.05% (Exp. 1) and .80 to 1.10% (Exp. 2) in .10% increments and from .80 to 1.25% (Exp. 3) in .15% increments. Diets fed to all pigs from 20 kg to termination contained National Research Council-recommended levels of lysine. The addition of lysine significantly improved feed efficiency in all experiments and weight gain in Exp. 1 and 2 during the 8- to 20-kg period. Performance during the periods following 20 kg was similar and not affected by dietary lysine levels fed from 8 to 20 kg. Carcass characteristics were unaffected by starter lysine level. The data indicate that pig performance from weaning (8 kg) to market weight was not influenced by starter diets minimally deficient in lysine.

A total of 96 crossbred pigs received various levels of sodium selenite to determine the effect of dietary selenium (Se) on growing swine fed corn-soybean meal diets. Levels of supplemental Se were 0, 4, 8, 12, 16 and 20 µg/g. There were linear decreases (P<.01) in both gain and feed intake with increasing levels of dietary Se. Feed/gain increased numerically as dietary Se increased. Hair Se increased quadratically (P<.01) and blood Se increased linearly (P<.01) with increasing level of dietary Se. Cell volume and hemoglobin were not affected by dietary treatment. Increasing dietary Se significantly increased glutathione peroxidase (GSH-Px), glutamic-oxalacetic transaminase (GOT) and glutamic-pyruvic transaminase (GPT). External signs of selenosis were noted in some pigs fed 12 or 20 µg/g of Se. The toxic level of Se in a corn-soybean meal diet for crossbred pigs appears to be between 4 and 8 µg/g. Of variables studied, growth rate was the most sensitive indicator of chronic selenosis in swine.

Two experiments were conducted to determine the effect of varying dietary selenium (Se) levels and Se source on growing swine. In Exp. 1, seleniferous wheat and oats were used to formulate diets containing .47, 2.58, 5.60 or 8.40 µg/g organic Se. Dietary Se level had no effect on pig performance during the 6-wk experiment as measured by daily gain, daily feed intake or feed/gain. Blood composition and enzyme activity were not affected by dietary treatment. Selenium concentrations of blood, hair, liver, kidney, heart, spleen and diaphragm muscle were increased linearly (P<.01) as dietary. Se increased. In addition, liver weight as a percentage of body weight was increased linearly (P<.01) as dietary Se level increased. No signs of chronic Se poisoning were observed. Dietary treatments in Exp. 2 were similar to Exp. 1 with the exception that sodium selenite was utilized as the Se source and the diets were fed for 17 wk. Inorganic Se levels of .54, 2.63, 5.69 or 8.3 3 µg/g had no effect on pig performance as measured by daily gain, daily feed intake or feed/gain. Selenium concentrations of blood, hair, liver, kidney, spleen and diaphragm muscle were significantly increased as dietary Se level increased. Liver weight as a percentage of body weight was increased at the two highest dietary Se levels. Blood glutathione peroxidase activity was significantly increased by dietary treatment, while other blood variables were not affected. No signs of chronic Se poisoning were observed. These results suggest that the toxic level of Se for growing pigs fed diets of this type is greater than 8.33 µg/g regardless of the Se source.The data for rats, while generally indicating the same degree of effects as the data for swine, suggest that rats are more susceptible to chronic poisoning by selenium.

Sixty-four Large White × Landrace primiparous sows were utilized to evaluate the influence of feeding 6 vs 9 Meal ME/d during gestation on reproductive performance. The sows remained on their respective gestation diets for four parities if they successfully farrowed, rebred and conceived. Sows fed 9 Mcal ME/d gained more weight (P< .05) through the gestation period during parities 1 and 2 and were heavier (P< .01) on d 110 of gestation for combined parities. Lactation weight loss was greater (P< .05) for the sows fed 9 Meal ME/d, resulting in similar weights at weaning. Ultrasonic backfat measurements were greater (P< .01) on d 110 of gestation for sows fed 9 Mcal ME/d during parity 1 and remained higher (P< .01) through the fourth-parity gestation. Although sow weaning weights were similar, sows receiving 6 Mcal ME/d scanned less backfat thickness. Gestation treatment significantly affected consumption of a common lactation diet provided ad libitum. Sows fed 6 Meal ME/d during gestation consumed an average of 22 kg more feed (P< .01) during lactation than those sows receiving 9 Mcal ME/d. Litter performance as measured by number and weights of pigs born alive and weaned was not altered (P> .10) by gestation energy intake. Days to return to estrus and the number of sows remaining in the study for four parities were similar (P> .10) between the two treatment groups. The number of farrowings for the four parities totaled 164, with 83 and 81 farrowings for the sows fed 6 and 9 Mcal ME/d, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Three trials utilizing 240 crossbred pigs, averaging approximately 5 weeks of age (8 to 11 kg), were conducted to determine the efficacy of oats, rolled oats, dehulled high protein oats and hulless barley as ingredients in pig starter diets. Pigs fed simple corn-soy diets had a greater average daily gain and required less feed/gain than pigs fed oats, with or without animal fat, to replace half or all of the corn in the diet. Addition of .3% lysine to a rolled oats diet improved (P<.05) both rate and efficiency of gain and equaled gain and feed/ gain of pigs fed a rolled oats-soy diet. Pigs fed an 18% protein, hulless barley-soy diet gained less (P<.01) and required more feed/gain (P<.01) than pigs fed an 18% protein, corn-soy, corn-oats-soy or dehulled high protein oats diet supplemented with lysine.

Three experiments were conducted with a total of 190 Yorkshire × Hampshire crossbred pigs (initial weight 35.0, 27.4 and 22.4 kg. for Experiments 1, 2 and 3 respectively) to determine the effect of dietary levels and ratios of calcium and phosphorus on gain, feed intake, feed conversion, bone weight, bone breaking strength (BKS), percent bone ash and incidence of atrophic rhinitis (AR) in growing-finishing swine.There were no significant differences in average daily gain, feed intake or feed conversion due to variation in dietary calcium or phosphorus levels in Experiment 1. BKS was significantly (P<.005) higher for the high level of phosphorus and interrelated level of calcium (Diet D). Experiment 2 showed an over-all significant (P<.005) difference in BKS and bone weight due to experimental treatment. BKS and bone weight were also significantly (P<.005) higher in pigs fed diets with 0.65% calcium than for those fed 0.35%. BKS and bone weight had a correlation of 0.82% for Experiment 2.In a third experiment, pigs were fed diets varying in levels of phosphorus and amounts of inorganic phosphorus. Increasing phosphorus in equal increments from 0.30% to 0.70% of the diet improved average daily gain in a linear manner. Also, the linear effect of levels of dietary phosphorus on feed intake was significant (P<.005) with the highest intake at the 0.60% level.BKS was significantly affected by dietary treatment (P<.05). The linear component of the effect of phosphorus levels on BKS approached significance. Bone weight followed the same trend as BKS with a correlation of 0.66.The results of these experiments show that calcium and phosphorus levels and ratios can vary considerably without significantly affecting daily gain and feed conversion of pigs. Levels and ratios of the two elements do affect bone formation as shown by BKS and bone weight data. In these experiments, bone weight seemed to be nearly as good a measurement of bone formation as BKS.Within the levels and ratios of calcium and phosphorus studied, there was no relationship between dietary calicum and phosphorus and atrophic rhinitis in growing-finishing swine.