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A cooperative research study involving members of a regional committee (North Central Regional Committee on Swine Nutrition [NCR-42]) was conducted to assess the variability in nutrient composition (DM, CP, Ca, P, Se, and amino acids) of corn and soybean meal from 16 sources (15 states, mostly in the Midwest) and to assess the analytical variability in nutrient assays among 22 laboratories (labs; 16 experiment station labs and six commercial labs). Corn samples were obtained from each participating station's feed mill during a 3-yr period (1989, 1990, and 1992), as were soybean meal samples during a 2-yr period (1989 and 1990). Both regular soybean meal (with hulls) and dehulled soybean meal were represented in the study. Samples were analyzed for DM and CP by all 22 labs, for Ca and P by 15 labs, for amino acids by 10 labs, and for Se by 6 labs. Each lab used its own analytical procedures. Samples of corn and soybean meal varied in their nutrient composition depending on the area of origin. The greatest variation among sources was in Se concentration, ranging from .02 to .29 mg/kg in corn and .08 to .95 mg/kg in soybean meal. Crude protein and lysine in corn were positively correlated, but the regression coefficient was low (r2 = .49). The relationship between CP and lysine for the two soybean meals combined was considerably stronger (r2 = .81). Lysine in corn increased by .018 percentage point and lysine in soybean meal (regular and dehulled combined) increased by .063 percentage point for each 1 percentage point increase in CP. Except for CP and Se, the analytical variability among labs was as great as, and in some cases greater than, the variability in nutrient composition among sources of corn and soybean meal. Within-lab analytical variability tended to be less than among-lab variability. Some labs performed certain analyses with considerably less variability and more accuracy than others.

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Four experiments were conducted to determine the effect of Cu source and level and an antimicrobial agent on performance of nursery (6 to 25 kg) and growing (20 to 65 kg) pigs. Copper was fed either as CuSO4.5H2O (CS), inorganic chelated Cu (ICC) or organic chelated Cu (OCC) to provide 31.25 to 250 ppm supplemental Cu. In Exp. 1, 224 pigs were used to study Cu source and level added to nursery diets. No difference (P less than .05) among treatments was observed during the nursery period. Treatments were continued the first 56 d of the growing-finishing period. Regardless of the Cu source, pigs receiving 125 ppm added Cu gained faster (P less than .05) than pigs in other treatments. In Exp. 2, 216 pigs were used to determine the optimum level of CS and ICC in nursery diets. Pigs were less efficient (P less than .01) when Cu was added at 62.5 and 125 ppm than at 250 ppm (1.69, 1.72 and 1.59, feed/gain respectively). In Exp. 3, no differences (P greater than .05) in performance between sources or among levels of Cu were found. In Exp. 4, 216 pigs were utilized to determine the combined effects of Cu source and an antimicrobial on performance. Pigs fed ICC were less efficient (P less than .01) than pigs fed either OCC or CS (1.99, 1.85 and 1.90, respectively). The inorganic and organic chelated Cu compounds used in these studies were not more efficacious than CS for nursery or growing pigs.

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Three experiments were conducted to evaluate sow and piglet productivity under extended photoperiod. In Exp. 1, 98 crossbred, lactating sows were housed in one of four treatments: thermoneutral air temperature (23.6 degrees C) in either (h of light:dark) 1:23 or 16:8 photoperiods, or heat stress (30.4 degrees C) in either 1:23 or 16:8 photoperiods. Heat stress reduced (P less than .05) sow feed intake, piglet mortality and piglet weaning weight and increased (P less than .01) sow lactation weight loss. Number of pigs weaned per litter was increased (P less than .01) when sows were heat-stressed. Extended photoperiod reduced (P greater than .05) time for sows to rebreed postweaning by .4 d. The interaction between air temperature and photoperiod was significant only for sow lactation weight loss. Heat stress increased sow lactation weight loss, but this effect was more severe in the 1:23 than in the 16:8 photoperiod. Experiments 2 and 3 examined the effects of 1:23 or 16:8 photoperiods on nursery pig performance when pigs were weaned from sows experiencing 1:23 (Exp. 3) or 16:8 (Exp. 2) photoperiods. In both nursery studies, photoperiod did not influence (P greater than .10) postweaning pig mortality, feed intake, weight gain or gain:feed ratio. In conclusion, extended photoperiod reduced days to return to estrus and reduced sow lactation weight loss, especially during heat stress. No benefits in preweaning or postweaning piglet weight or survival were observed by use of extended photoperiod.

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Two experiments using 120 sows were conducted to determine the effects during heat stress of two floor types, snout coolers or a water drip system, and a high energy-density diet. During both studies, air temperature was maintained at or above 29 degrees C. Floor types included partially slotted concrete and plastic-coated, expanded metal. In Exp. 1, in addition to floor-type treatments, snout coolers were on or off and the water drip was on for 3 min each 10 min or off. Snout coolers increased (P less than .05) sow feed intake and decreased (P less than .05) sow lactation weight loss. Water drip increased (P less than .002) sow feed intake and reduced lactation weight loss. The drip X floor-type interaction was significant for most measures of piglet performance. Drip was beneficial for piglet weights when piglets were on plastic, whereas drip was detrimental to piglet performance while they were housed on concrete. In Exp. 2, two floor types, drip or no-drip and a high energy-density diet or control diet were examined during heat stress. The high energy-density diet reduced (P less than .01) sow feed intake but provided no measurable increase in piglet performance during heat stress. We conclude that water drip is an effective cooling technique for heat-stressed sows, especially when floors are plastic. Snout coolers, partial concrete slots and high energy-density diets provided only minor benefits to heat-stressed sows and were not of benefit to piglets nursing heat-stressed sows.

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A total of 486 crossbred weanling pigs was used in a series of experiments to determine first the effects of heat and social stress and their interaction on pig performance and, second, to determine a possible cause for the observed effects. Pigs were held six/nursery pen and fed and watered ad libitum. In Exp. 1, pigs were held at either thermal neutral 26.6 C for the 21 d and 23.8 C for the final 7 d, or at the heat-stress temperature (32.2 C) for the entire 28-d period. Within each temperature treatment, one-half of the pigs were left as single-litter controls and one-half were randomly regrouped (social stress). Pig feed intake and weight gain were reduced (P less than .05) among heat-stress pigs during the 7- to 28-d and 0- to 28-d periods. The interaction between social and thermal stress was significant for gain:feed ratio for the 7- to 28- and 0- to 28-d periods. Regrouping depressed gain:feed ratio only among heat-stressed pigs. In Exp. 2, a two-pig behavioral bioassay was used to determine if agonistic behaviors were influenced by heat stress. Pigs that were regrouped into 32.2 C rooms exhibited reduced mean level (P less than .05) and variation (P less than .001) of submissive behavior. Duration of aggressive behavior and latency to attack were unaffected by thermal treatments. Increased social stress at the time of regrouping could not account for poor performance of heat-stressed, regrouped pigs.(ABSTRACT TRUNCATED AT 250 WORDS)

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An experiment was conducted to determine when, during a 24-h period, gilts show the onset of behavioral estrus. Beginning on Day 16 of their first estrous cycle, 42 crossbred gilts were observed at 0600, 1200, 1800, and 2400 h for the onset of their second estrus. Fifty-five percent of the gilts had shown onset of estrus by 0600 h. None of the gilts showed the onset of estrus from 0600 to 1200 h, whereas 24% and 21% of the gilts had shown onset of estrus by 1800 and 2400 h, respectively. Chi-square analysis demonstrated that more (P < 0.025) gilts had shown onset of estrus by 0600 than by 1200, 1800, and 2400 h. When the data were combined for estrous checks by 0600 and 1800 h, 76% of the gilts had their onset of estrus by 0600 h as compared to 24% of the gilts by 1800 h (P < 0.005). In conclusion, more gilts had shown onset of estrus by 0600 h than at any other 6-h period.

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Two experiments were conducted to determine the effects of a) parity and season of the year on the interval from weaning to rebreeding in sows and b) altered suckling intensity (ASI) and gonadotropin releasing hormone (GnRH) on the postpartum interval in primiparous and multiparous sows. Experiment I included 406 weaning-to-rebreeding intervals in 172 primiparous and multiparous sows. Primiparous sows returning to estrus during the spring and summer months had a longer (P<0.001) rebreeding interval (11.0 d) than the other groups (5.7 d). In Experiment II, 32 sows were assigned to a factorially designed experiment. The factors were ASI, GnRH and parity. Treatments were begun 7 d before weaning (about 4 wk of age). The ASI was accomplished by separating the sow from her litter for 12 h each day. The average interval from the beginning of treatment to the onset of estrus was 13.4 d and was not affected (P>0.33) by ASI, GnRH, parity or their interactions. None of the factors was found to affect the average weaning weight of the piglets (P>0.05); however, piglets in the ASI group were heavier (P<0.03) at 1-wk postweaning than those in the no-ASI group. The results showed that primiparous sows returning to estrus during the spring and summer months had the longest rebreeding interval. Additionally, neither GnRH nor ASI, separately or in conjunction, decreased the postpartum interval in sows.

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Two experiments were conducted to determine the effect of aerosolized 5 alpha-androst-16-en-3-one (androstenone) on pig aggressive and submissive behaviors and on pig performance. In Exp. 1, twenty-four 5-wk-old pigs were randomly regrouped in a two-pig bioassay. A solution of either isopropyl alcohol or .5 mg androstenone in isopropyl alcohol per pig was aerosolized on both pigs in the observation pens. Summarization of video records from the 90-min bioassay showed that pens of pigs aerosolized with androstenone spent 58% less time engaged in aggressive behavior (P less than .05) and 96% less time engaged in submissive behavior (P less than .01). In Exp. 2, a performance trial was conducted with finishing pigs from 57 to 91 kg body weight. Factorially arranged treatments included aerosolized androstenone (.5 mg/pig) or the vehicle isopropyl alcohol and regrouping into uniform body weight blocks or no regrouping. Regrouping depressed average daily feed consumption (P less than .05) and average daily gain (P less than .05) for the first 7 d of the trial. Pigs reveiving the androstenone aerosol had improved average daily gain (P = .01) and gain:feed ratio (P less than .01) for the first 28 d of the trial. Performance of all treated pigs was similar for the entire finishing period. This olfactory stimulant reduced pig agonistic behavior and transiently improved performance of regrouped and non-regrouped finishing pigs.

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Fifty-three primiparous sows were used to study the effects of a high-energy, fat-supplemented diet on sow lactation and rebreeding performance. Sows received either a low [Lo, 12.5 Mcal metabolizable energy (ME)/d] or high (Hi, 16.0 Mcal ME/d) energy sorghum-soybean diet during a 28-d lactation. At weaning, sows were randomly allotted, within lactation treatment, to a low (lo, 5.54 Mcal ME/d) or high (hi, 9.61 Mcal ME/d) energy sorghum-soybean diet until the day of first postweaning estrus. Primiparous sows fed Lo weaned larger (P less than .05) litters than sows fed Hi; however, average pig weight was not affected by lactation treatments. Primiparous sows fed Hi had more backfat at weaning (P less than .01) than Lo sows. In contrast, sow weight was not affected by dietary treatments. Neither lactation nor rebreeding treatments influenced days to rebreeding; however, an interaction (P less than .01) was observed. Mean days from weaning to rebreeding for Lolo, Lohi, Hilo and Hihi sows were 10.0, 7.6, 6.9 and 17.1, respectively. Forty sows were maintained on the same dietary treatments during their second parity. Sows receiving Lo during their second parity farrowed and weaned more (P less than .05) pigs than Hi sows. Multiparous sows fed Hi nursed heavier (P less than .05) pigs on d 21 of lactation and at weaning compared with Lo sows. Sows fed Hi were heavier (P less than .05) and had more (P less than .01) backfat at weaning of their second litter compared to Lo sows. Days to postweaning estrus were not affected by lactation or rebreeding diets. Mean length of the second parity rebreeding interval for Lolo, Lohi, Hilo and Hihi sows was 6.2, 10.2, 7.0 and 10.5 d, respectively. These results suggest that feeding levels during lactation of 12.5 Mcal ME/d or higher supported adequate rebreeding performance. Postweaning feeding levels did not influence days to first estrus. Feeding a high energy diet continuously throughout the lactation and rebreeding phases in primiparous sows may lengthen the postweaning interval to estrus.

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Effects of age and diet composition on amylase, trypsin and chymotrypsin activities in the pancreas and intestinal contents, pancreas weights and body weights were determined from birth to 56 d. A total of 120 pigs, five to seven pigs/litter from 18 litters, were slaughtered at birth, 14, 27, 29, 31, 42 and 56 d. Litters were allotted to dietary treatments (corn-soy, A; corn-soy + 20% dried whey, B; corn-soy + 5% lard, C) and offered these diets as creep feed at 14 d. All pigs were weaned at 28 d, placed in elevated nursery pens and fed their respective diets. Total activities of amylase, trypsin and chymotrypsin in the pancreas and small intestine increased (P less than .05) with age. Both trypsin and amylase activities, measured per kilogram body weight or gram pancreas weight, were low at 29 d in the intestine and increased to 56 d. Pigs on diet B had the highest level of trypsin and chymotrypsin in the intestinal contents (P less than .05). Trypsin activity in the pancreas (units/kg body weight) was lowest (P less than .05) for pigs on diet B and highest (P less than .05) for those on diet C (units/g pancreas and units/kg body weight). Amylase activity (units/kg body weight) was lower (P less than .05) in the pancreas for pigs on diet B than for those on diets A and C. Pigs on diet A had lower (P less than .01) intestinal amylase activities than those on diets B and C. Enzyme activities in the intestinal contents and pancreas were low following weaning. In the pancreas, activities decreased at 31 d.(ABSTRACT TRUNCATED AT 250 WORDS)

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Dried whole whey, lard or dried skim milk was added to a corn-soybean meal basal diet to determine the effect on apparent nitrogen (ND), energy (ED) and dry matter digestibility (DMD) in pigs weaned at 28 d. Four groups of four littermate barrows were allotted to the experimental diets and placed in individual metabolism pens for 12 d (3 d adjustment and three collection periods of 3 d each) after weaning. The study was a 4 X 3 factorial with diet and period as main effects. Addition of dried skim milk or dried whey to the diet resulted in higher values (P less than .05) for DMD and ED as compared with the basal or corn-soy and lard diet. Pigs fed added dried skim milk had improved (P less than .05) ND over pigs on other dietary treatments. All nutrient digestibility coefficients increased (P less than .05) from period 1 to period 2, and ND increased (P less than .05) from period 2 to 3. It was concluded that the young pig requires at least 6 to 9 d after weaning at 28 d to adjust to typical corn-soybean meal starter diets.

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Broiler chickens and swine fed furazolidone in their diet were sacrificed, and samples of liver, kidney, skin/fat and muscle were harvested and analyzed for furazolidone residue. Chickens fed 200 g of furazolidone/ton of feed were withdrawn from treatment 21, 14, 7, 5, 3, or 0 days before slaughter. Birds withdrawn from medication more than 5 days prior to slaughter had no residues in any of the tissues sampled. One of the 12 birds in each of the 5 day and 3 day withdrawal groups had detectable residues in the skin/fat. Seven of the 12 birds in the 0 day withdrawal group had residues of less than 2 ppb in skin/fat samples. Chickens fed 400 g furazolidone/ton of feed were withdrawn from treatment 0 days before slaughter. Residues of 0.7 to 3.5 ppb were found in the skin of these birds; residues were not found in other tissues. Swine were fed 300 g furazolidone/ton of feed for 2 weeks or 150 g/ton for 5 weeks. They were withdrawn from treatment 10, 7, 5, 3, or 0 days before slaughter. Tissue samples taken from these swine did not contain detectable furazolidone residues.

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A totaL of 160 crossbred pigs were fed a sorghum-soybean meal diet with ammonium polyphosphate (APP) or dicalcium phosphate (DiCa) as supplemental phosphorus (P) sources for growing-finishing swine. The diets contained P levels of .5 and .4% for the grower phase and .4 and .33% for the finisher phase. Ammonium polyphosphate was evaluated on the basis of pig performance and bone development and compared with DiCa as a standard. The first rib and third and fourth metacarpals were removed from eight barrows from each of the four treatments. Replacement of DiCa with APP as the P supplement did not affect (P greater than .05) average daily gain, average daily feed and feed:gain ratio of growing-finishing pigs. No effect on bone variables examined on the first rib and third and fourth metacarpals was obtained between pigs fed APP or DiCa. Pigs on the lower supplemental P levels had lower (P less than .05) dry fat-free weight and percentage ash for all three bones. The breaking force of the first rib was less (P less than .05) for the pigs fed the lower P supplements of APP and DiCa than for pigs fed the higher level of DiCa. A trend was observed for an apparent decreased P availability from APP than DiCa when fed at the lower level of supplementation, but this trend was not observed when APP was added to provide a P level to meet National Research Council requirements. Ammonium polyphosphate as a P supplement for growing-finishing swine was satisfactory for performance and bone mineralization as compared with DiCa.

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Three experiments were conducted that involved a total of 415 sows. Feeding levels of 3.6 vs 1.8 kg.head-1.d-1 for sows at weaning were compared in two experiments. In the third experiment, no feed was given for 2 d, then 2.7 kg was fed until sows were bred and 1.8 kg fed thereafter, as compared with 1.8 kg.head-1.d-1 fed throughout the period from weaning to farrowing. Modifying the feeding level from 1.8 kg daily did not shorten the time interval from weaning to breeding or improve other reproductive traits of sows. A trend for fewer sows to be bred was obtained by feeding either 3.6 kg or the zero feed for 2 d then 2.7 kg feeding levels, as compared with those fed 1.8 kg in the first two experiments. In the third experiment, fewer sows were bred (P less than .05) that were fed 3.6 kg than sows fed 1.8 kg daily. First litter sows tended to consume more feed from weaning to breeding than second and third litter' sows when offered 3.6 kg daily, which may indicate a higher energy need for these younger sows.

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