Effect of swine weaning age on body fat and lipogenic activity in liver and adipose tissue

Two experiments were conducted to evaluate the effects of weaning swine at 2 or 5 wk of age on postweaning performance and fat metabolism. In the first experiment, 52 pigs were weaned at 2 or 5 wk of age with body weights determined from birth to 8 wk. The early weaned group was fed a 20% protein corn-soybean meal-oat diet containing 25% dried whey from 2 to 5 wk while both groups were fed a 20% protein cereal grain-based diet from 5 to 8 wk of age. In a second experiment, a total of 90 pigs weaned at similar ages and fed the same diet sequences were killed at weekly intervals from 2 to 8 wk of age to evaluate body fat content and lipogenesis in liver and adipose tissue. Lipogenic capacity was measured by incorporation of acetate-1 14C into the total lipid fraction in liver slices and adipose tissue minces or by monitoring liver ATP citrate lyase activity. The results demonstrate that pigs weaned at 2 wk experience a slower postweaning growth rate with lower empty body weights than those either concurrently nursing the dam or weaned at 5 wk of age. Both groups had similar body weights from 6 to 8 wk of age. The body fat content of nursing pigs increased from 2 to 5 wk of age. Pigs weaned at 2 wk lost approximately 25% of their body fat the first week postweaning while later-weaned pigs did not lose body fat postweaning. Body fat composition of both groups was similar by 8 wk of age. Lipogenic activity was higher in liver than in adipose tissue from 2 to 5 wk of age and remained relatively constant throughout the trial. Adipose tissue lipogenic activity was lower in the nursing pig but increased dramatically at 5 wk in the early-weaned group and 7 wk of age in the late weaned group. These results suggest that weaning age can affect postweaning body fat composition and that adipose contributes a greater lipogenic capacity than liver tissue as the pig matures.     

Weaning weight response of pigs to simple and complex diets

Five experiments were conducted to determine (1) the value of simple vs complex diets on gains and feed conversion of pigs weaned at a constant age but varying in weight, (2) the optimum postweaning time to change from a complex to a simple diet and (3) the effect of previous treatment on subsequent performance. In the first experiment, pigs were weaned at 3 wk +/- 3 d and assigned within four weight groups (4.1, 5.0, 5.6 and 6.7 kg) to a simple or complex diet that was fed for 28 d. The complex diet improved (P less than .01) pig performance in all weight groups. As anticipated, the heavier pigs (5.6 and 6.7 kg) ate more (P less than .02) and grew faster (P less than .03) than did their lighter weight littermates (4.1 and 5.0 kg). The second experiment involved pigs weaned at 3 wk +/- 3 d that were assigned within two weight groups (4.4 and 6.6 kg) and fed a complex diet for 10 d, after which one-half of each weight group was switched to a simple diet. Pigs fed the complex diet for the entire 24-d period gained faster (P less than .05) and were more efficient (P less than .05) than those changed to the simple diet after 10 d. The heavier weight (6.6 kg) pigs ate more (P less than .02) and gained faster (P less than .02) than did the lighter weight (4.4 kg) pigs.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of weaning, week postweaning and diet composition on pancreatic and small intestinal luminal lipase response in young swine

The effects of weaning, week postweaning and diet composition on concentration of lipase in the pancreas and small intestinal lumen were investigated in weanling swine. In Exp. 1, lipase levels were evaluated in suckling pigs from 2 to 35 d of age and in pigs weaned at 21 or 35 d of age. Pigs weaned at 21 d of age were fed a corn-soybean meal diet with lipase levels measured from 3 to 28 d postweaning. Pancreas weights increased during the suckling period; they were lowered at 3 d postweaning and were lower at 7 d postweaning than in suckling pigs but increased linearly from 3 to 28 d postweaning. Lipase level per unit wet tissue and total pancreatic levels increased from 2 to 35 d of age in suckling pigs (P less than .01). Weaning at 21 d of age resulted in a decline (P less than .05) in lipase levels in the pancreas at 3 and 7 d postweaning, but the levels subsequently tended to increase between 7 and 28 d postweaning. Whereas relative lipase levels in the intestinal lumen increased from 2 to 35 d of age in suckling pigs, total luminal enzyme did not decline upon weaning when pigs were weaned at either 21 or 35 d of age. Total luminal lipase per unit empty body increased linearly (P less than .01) each week postweaning. In Exp. 2, a 2 X 2 factorial arrangement of corn oil (0 or 6%) and dried whey (0 or 25%) was used to evaluate digestive lipase levels in pigs weaned at 21 d of age.(ABSTRACT TRUNCATED AT 250 WORDS)     

Early- and traditionally weaned nursery pigs benefit from phase-feeding pharmacological concentrations of zinc oxide: effect on metallothionein and mineral concentrations.

Benefits of feeding pharmacological concentrations of zinc (Zn) provided by Zn oxide (ZnO) to 21-d conventionally weaned pigs in the nursery have been documented; however, several management questions remain. We conducted two experiments to evaluate the effect on growth from feeding 3,000 ppm Zn as ZnO during different weeks of the nursery period. In Exp. 1 (n = 138, 11.5 d of age, 3.8 kg BW) and Exp. 2 (n = 246, 24.5 d of age, 7.2 kg BW), pigs were fed either basal diets containing 100 ppm supplemental Zn (adequate) or the same diet with an additional 3,000 ppm Zn (high) supplied as ZnO. Pigs were fed four or two dietary phases in Exp. 1 and 2, respectively, that changed in dietary ingredients and nutrient content (lysine and crude protein) to meet the changing physiological needs of the pigs for the 28-d nursery period. Dietary Zn treatments were 1) adequate Zn fed wk 1 to 4, 2) high Zn fed wk 1, 3) high Zn fed wk 2, 4) high Zn fed wk 1 and 2, 5) high Zn fed wk 2 and 3, and 6) high Zn fed wk 1 to 4. In Exp. 1 and 2, pigs fed high Zn for wk 1 and 2 or the entire 28-d nursery period had the greatest (P < .05) ADG. During any week, pigs fed high Zn had greater concentrations of hepatic metallothionein and Zn in plasma, liver, and kidney than those pigs fed adequate Zn (P < .05). In summary, both early- and traditionally weaned pigs need to be fed pharmacological concentrations of Zn provided as ZnO for a minimum of 2 wk immediately after weaning to enhance growth.     

Effect of lactation and rebreeding phase energy intake on primiparous and multiparous sow performance

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.     

Effects of prepartum administration of 1,3-butanediol to sows on growth and survival of neonatal pigs

In six trials, 158 late-term gravid sows were fed isocaloric amounts (8,500 kcal metabolizable energy/d) of a corn-soybean meal-based diet in which 20% of their daily metabolizable energy (ME) intake was supplied by either cornstarch or 1,3-butanediol (butanediol) from about d 105 of gestation to parturition. After parturition, all sows were allowed to consume a standard, corn-soybean meal-based lactation diet, ad libitum, during a 28-d lactation. Prepartum administration of butanediol, a stable, nonvolatile liquid that possesses anesthetic, antimicrobial and ketogenic properties, did not alter the voluntary feed intake or body weight changes of sows pre- or post-partum. Number of pigs born per litter, average pig birth weight and incidence of stillbirths were not influenced by the prepartum diet of the sows. However, the addition of butanediol to the prepartum diet increased (P less than .10) the number of pigs weaned per litter at 28 d by .51 pigs (8.17 vs 7.66) and improved (P less than .10) the survival rate of pigs from birth to weaning by 5.7 percentage units (84.1 vs 78.4%) compared with those of sows fed isocaloric additions of starch. Average pig weights at 28 d of age were similar for the two treatment groups (6.18 vs 6.08 kg) even though greater numbers of pigs were nursing sows fed the butanediol diet prepartum. The rate and efficiency of gain and survivability of weanling pigs during a 28-d postweaning period were not influenced by the prepartum diet of their dam.     

Characterization of microbial populations and volatile fatty acid concentrations in the jejunum,ileum, and cecum of pigs weaned at 17 vs 24 days of age

In a series of five 17-d replicate trials, a total of 54 cannulated and 12 noncannulated pigs were used to determine the effects of weaning age (17 d or 24 d) on pH, dry matter percentage, aerobic and anaerobic microflora, lactate, and volatile fatty acid (VFA) concentrations in the jejunum, ileum, and cecum of weanling pigs. At -14 d of age, cannulated pigs were surgically fitted with T-cannulas in the jejunum (n = 20), ileum (n = 18), or cecum (n = 16). Upon weaning, cannulated pigs were individually caged in an environmentally controlled room with ad libitum access to a phase starter diet and water. Noncannulated pigs were killed at weaning and samples were collected from the jejunum, ileum, and cecum. Digesta and fecal swabs from cannulated pigs were collected twice weekly. The pH of cecal contents was lower (P < 0.05) and dry matter percentage was greater (P < 0.05) than those ofjejunal or ileal contents. Pigs weaned at 24 d of age had increased (P < 0.05) E. coli populations 3 d postweaning compared to preweaning populations, regardless of site of collection, whereas this increase was not observed in pigs weaned at 17 d of age. Unweaned pigs maintained higher (P < 0.05) lactobacilli populations compared to weaned pigs; however, populations declined (P < 0.05) in both groups by 3 d postweaning, with pigs weaned at 24 d of age having lactobacilli populations greater than pigs weaned at 17 d of age. Fecal populations of E. coli and lactobacilli declined (P < 0.05), whereas fecal bifidobacteria populations increased (P < 0.05) postweaning, regardless of weaning age. Concentrations of total fecal anaerobes declined (P < 0.05) in pigs weaned at 17 d of age but were maintained in pigs weaned at 24 d of age. Volatile fatty acid concentrations were greater (P < 0.05) in the cecum than in the jejunum or ileum, and acetic acid concentrations decreased (P < 0.05) postweaning regardless of weaning age. A tendency for L+ lactate concentrations to be greater (P < 0.07) in the ileum and jejunum vs the cecum was observed. Results indicate that weaning and weaning age have significant effects on microbial populations and VFA concentrations.     

The effect of meal intervals and weaning on feed intake of early weaned pigs

Feed intake was investigated in early weaned pigs housed in two environments. In the first experiment, pigs in an unfamiliar environment (removed from the sow and placed in nursery pens) were offered a dry diet either ad libitum or at different meal intervals (2, 4 and 6 h). Regardless of meal interval (ad libitum or hourly intervals), early weaned (21 d) pigs failed to consume sufficient feed for maintenance during the first 3 d postweaning. Pigs provided feed ad libitum consumed more (P less than .001) feed (142 vs 84 g/d) and gained more (P less than .05) weight (57 vs 3 g/d) than meal-fed pigs over the 7-d period. Pigs fed at 2-h intervals consumed more (P less than .001) feed than pigs fed at 4-h or 6-h intervals. Compared with preweaning levels (307 mu eq/liter), plasma free fatty acid (FFA) levels increased approximately fourfold by d 1 postweaning (1,372 mu eq/liter), then decreased through d 7 to levels below preweaning (142 mu eq/liter). The FFA levels were not affected (P greater than .1) by meal interval. In a second experiment, feed intake was investigated in weaned pigs that were allowed to consume food by a familiar method and in a familiar environment (suckling the sow). When allowed to nurse following a 24-h weaning period, weaned pigs consumed (24.3 +/- 2.8 g/suckling) the same amount (P greater than .1) as non-weaned littermates (28.7 +/- 1.8 g/suckling).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of evening or morning weaning and immediate or delayed feeding on postweaning performance of pigs.

Weanling pigs (n = 176), 21 to 26 d of age (average initial weight, 7.1 kg), were used to evaluate the effects of weaning time (evening vs morning) and feeding time (immediate vs delayed) on postweaning performance. Pigs were randomly allotted within litters to four treatments in a 2 x 2 factorial arrangement as follows: 1) weaning at 2000 with immediate feeding, 2) weaning at 2000 with 12-h delayed feeding, 3) weaning at 0800 with immediate feeding, and 4) weaning at 0800 with 12-h delayed feeding. A 12:12 light:dark photoperiod was maintained. Four pigs were held per pen, and all pigs were given ad libitum access to a 20% CP corn-soybean meal diet with 15% dried whey throughout the 28-d study. The interactions between weaning and feeding times were not significant. During the 28-d period, pigs weaned at 2000 consumed 5% more feed (P less than .10) and grew 6% faster (P less than .05) than pigs weaned at 0800. Feed to gain ratios were similar for both time treatments. Variance of ADG within pens as measured by range, logarithm of variance, and CV were generally smaller for pigs weaned at 2000 than for pigs weaned at 0800 with no effect of feeding time. Pigs fed immediately after weaning and those delayed for 12 h had similar overall feed consumption, ADG, and feed to gain ratios. Weaning pigs in the evening enhanced performance, perhaps by better matching the normal diurnal eating and activity patterns and weaning time.     

Effects of diet complexity and dietary lactose levels during three starter phases on postweaning pig performance

Four experiments involving 1,005 crossbred pigs weaned at 19 +/- 2 d of age evaluated the effect of diet complexity and lactose level on starter pig performances. Experiment 1 was a randomized complete block (RCB) conducted in nine replicates with 135 pigs. A complex diet using several protein sources, a semicomplex diet with fewer protein sources, and a simple diet of corn and soybean meal comprised the three treatment groups. All diets contained 25% lactose (as-fed basis) with lysine (total) constant from d 0 to 14 (1.55%) and d 14 to 28 (1.45%), respectively. Gain, feed intake, and feed efficiency (P < 0.05) improved as diet complexity increased during both periods. In Exp. 2, 240 pigs in eight replicates in a RCB design were fed complex diets, but dietary lactose (total; as-fed basis) levels ranged from 10 to 35% in 5% increments from 0 to 14 d after weaning. From 14 to 30 d, a common 17% lactose diet was fed to evaluate the effects of early lactose level on subsequent responses. Gains (P < 0.05) increased for the 0- to 7- and 0- to 14-d periods as lactose increased to 30%. Similar gains resulted for all treatment groups from 14 to 30 d after weaning, with no evidence of compensatory responses to early lactose levels. In Exp. 3, 330 pigs were fed complex diets. From 0 to 7 d after weaning, the diets contained 25% lactose (as-fed basis), and from 7 to 21 d postweaning, the lactose levels ranged from 7 to 31% in 5% increments. Gain (P < 0.01) and feed efficiency (P < 0.05) increased from 7 to 21 d to the 17% lactose level. In Exp. 4, 300 pigs were fed 25 and 17% (as-fed basis) lactose diets from 0 to 7 and 7 to 21 d postweaning, respectively. From 21 to 35 d postweaning, lactose levels of 0 to 20% in 5% increments were added to a corn-soybean meal diet. The experiment was conducted as a RCB design in 12 replicates. Gain (P < 0.05) and feed intake (P < 0.05) increased to 10 to 15% lactose. When the data from Exp. 4 were partitioned into lighter (15.0 kg) and heavier (17.7 kg) pig weight replicates, only the lighter replicates had significant improvements in gain, feed intake, and feed efficiency (P < 0.05) in response to dietary lactose. These results demonstrated that starter pigs performed better when fed complex diets, that dietary lactose levels of 25 to 30% (to 7 kg BW) during the initial week postweaning, 15 to 20% lactose during d 7 to 21 (to 12.5 kg BW), and 10 to 15% lactose during d 21 to 35 postweaning (to 25 kg BW) resulted in maximum performance.     

Efficacy of initial postweaning diet and supplemental coconut oil or soybean oil for weanling swine

Two experiments involving a total of 581 crossbred pigs weaned at 23 +/- 2 d of age evaluated 1) the efficacy of two diets that contained milk products during the initial 14 d postweaning and 2) the effect of coconut oil or soybean oil additions to swine starter diets. In Exp. 1, postweaning performance responses of pigs fed a control corn-soybean meal-dried whey (C-SBM-DW) diet without added fat were compared with those of pigs consuming diets that contained 3, 6, or 9% levels of coconut oil or degummed soybean oil. The results demonstrated no beneficial weight gain, feed intake, or gain-to-feed ratio response during the initial 14 d postweaning to either dietary oil source. From 15 to 35 d, gains increased to the 6% added fat level, but there was no effect on feed intake when the gain-to-feed ratio was improved to the 9% fat level. In Exp. 2, two diets containing milk products were fed during the initial 14-d postweaning period. The first diet contained corn, soybean meal, dried whey, dried skim milk, and fishmeal (high nutrient dense diet, HNDD), and the second was a C-SBM diet with 25% dried whey. During the period from 15 to 35 d, diets contained no added fat or a 6% level of coconut oil, soybean oil, or the 1:1 combination of each at 3%. The results demonstrated that for the postweaning period from 0 to 14 d pigs fed the HNDD had higher gains (P less than .01), feed intakes (P less than .01), and gain-to-feed ratios (P less than .01) than pigs fed the C-SBM-DW diet.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of dietary calcium on selenium retention in postweaning swine

Two experiments were conducted to evaluate the effect of dietary Se and Ca on Se utilization in postweaning swine. Two levels of dietary Se (.3 or 5.0 ppm) supplemented as sodium selenite and four levels of total dietary Ca (.50, .80, 1.10 or 1.40%) in a 20% protein, corn-soybean meal diet were evaluated. Inorganic Ca was supplied from dicalcium phosphate and limestone. In Exp. I, 135 pigs weaned at 4 wk of age were allotted by sex, litter and weight and fed a basal diet for 7 d and then their treatment diets for a 28-d period. Plasma and tissue were collected at the end of the trial for Se concentration and glutathione peroxidase (GSH-Px) activity. Dietary Ca had no effect on gain or feed measurements but 5.0 ppm Se depressed daily gain slightly. When 5.0 ppm dietary Se was fed, there resulted higher liver, kidney, heart and longissimus muscle Se concentrations than when .3 ppm was provided, but dietary Ca had no effect on tissue Se values within each dietary Se level. Plasma GSH-Px increased when higher dietary Se was provided, whereas neither heart nor liver GSH-Px activity was affected by dietary Se or Ca level. In Exp. II, a 5-d balance trial was conducted with 32 barrows after adjustment to their treatment diet for a 28-d period. Selenium retention increased quadratically as dietary Ca increased, whereas Ca retention was not affected by dietary Se. These results suggest that low dietary Ca levels may reduce total Se retention but not Se metabolism within body tissue.     

Characterization of creep feed consumption and its subsequent effects on immune response, scouring index and performance of weanling pigs

Four trials were conducted to characterize the consumption of creep feed by nursing pigs and the effects of creep feeding (from 10 d to weaning at 28 d) on the immune response, scouring index and subsequent performance of weanling pigs. Pigs were fed a ground 20% CP corn-soybean meal-whey diet with 1.0% chromic oxide (control, 9 litters), this diet with 2.7% ovalbumin added as a dietary antigen (ovalbumin, 14 litters), or no creep feed (unexposed, 11 litters). At weaning, pigs within a litter were fed a 20% CP corn-soybean meal diet either with or without 2.7% ovalbumin. Creep-fed litters began eating at 11 d of age and disappearance of creep feed increased linearly until weaning (P less than .01). However, based on the chronic oxide coloring of the feces, total creep feed consumption was quite variable from pig to pig (13 to 194 g) and from litter to litter (107 to 1,550 g). Preweaning daily gain was similar between creep-fed and noncreep-fed litters; larger litters generally had lower daily gains (P less than .09) and less feed disappearance per pig (P less than .02). Weekly blood sampling showed that pigs fed the antigen diet had a higher (P less than .001) antibody titer to ovalbumin at 14, 21 and 28 d of age than did pigs fed the control diet or pigs unexposed to creep feed. At 56 and 63 d of age, all pigs given an ovalbumin injection at 49 d (1 ml containing 3 mg of ovalbumin) had responded (P less than .001) to injection, with the lowest titers for pigs fed the control creep diet and the highest titers for pigs fed the ovalbumin creep diet; titers were intermediate for pigs not fed creep. Regardless of preweaning or postweaning treatment, most pigs began scouring 4 to 5 d postweaning; scouring peaked at d 10 and returned to normal after d 15. Although the magnitude of difference was small, creep-fed pigs tended to scour more than pigs not fed creep (P less than .01). Postweaning performance was not influenced by preweaning treatments.     

Effect of spray-dried plasma and lipopolysaccharide exposure on weaned pigs: I. Effects on the immune axis of weaned pigs

A study was conducted with 20 weaned barrows (14 d, 4.98 +/- .21 kg) to determine the effect of spray-dried plasma (SDP) on the pig's immune response to a lipopolysaccharide (LPS) challenge. After weaning, pigs were fed a diet containing 0 or 7% SDP for 7 d. On d 6 postweaning, all pigs were fitted with a jugular catheter. On d 7 postweaning, the pigs were given an i.p. injection of either saline or LPS (150 microg/kg BW) followed by a 3-h blood collection every 15 min. Following blood collection, all pigs were killed and tissue was collected for mRNA analysis. Additionally, the small intestine was collected for measurement of villus height, crypt depth, and villus height:crypt depth ratio (VCR) at three sites (25, 50, and 75% of the total length). Feeding SDP resulted in reduced (P < 0.05) mRNA expression of tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta) mRNA in the adrenal gland, spleen, hypothalamus, pituitary gland, and liver. Additionally, expression of IL-6 mRNA was reduced (P < 0.05) in the spleen and pituitary gland for pigs fed SDP. For pigs fed the diet with SDP, LPS administration did not affect (P > 0.10) cytokine mRNA expression, whereas LPS reduced expression of TNF-alpha mRNA in the spleen and IL-1beta mRNA in the adrenal gland, spleen, and thymus for pigs fed the diet without SDP. For pigs fed the diet with SDP, LPS caused serum TNF-alpha to increase 150-fold compared to a 60-fold increase for pigs fed the diet without SDP. Similarly, interferon-gamma (IFN-gamma) increased 110-fold for pigs fed the diet with SDP compared to a 16-fold increase for pigs fed the diet without SDP. For pigs fed the diet with SDP, LPS caused major villus atrophy, whereas for pigs fed the diet without SDP, LPS had no effect on intestinal morphology. These results demonstrate that the basal activation of the immune system appears to be less for pigs fed the diet with SDP compared to pigs fed the diet without SDP after weaning. Additionally, for pigs fed the diet with SDP, there appeared to be an overresponse of the immune system following LPS administration, which resulted in major damage to the mucosa of the gastrointestinal tract.     

Effect of dietary organic microminerals on starter pig performance, tissue mineral concentrations, and liver and plasma enzyme activities

Weanling pigs (n = 160) were used to evaluate dietary essential microminerals (Cu, Fe, Mn, Se, and Zn) on performance, tissue minerals, and liver and plasma enzymatic activities during a 35-d postweaning period. A randomized complete block design with 5 treatments and 8 replicates was used in this study. Organic microminerals were added to complex nursery diets at 0 (basal), 50, 100, or 150% of the requirements of microminerals listed by the 1998 NRC. A fifth treatment contained inorganic microminerals at 100% NRC and served as the positive control. Pigs were bled at intervals with hemoglobin (Hb), hematocrit (Hct), glutathione peroxidase, and ceruloplasmin activities determined. Six pigs at weaning and 1 pig per pen at d 35 were killed, and the liver, heart, loin, kidney, pancreas, and the frontal lobe of the brain were collected for micromineral analysis. The liver was frozen in liquid N for determination of enzymatic activities. The analyzed innate microminerals in the basal diet met the NRC requirement for Cu and Mn but not Fe, Se, and Zn. Performance was not affected from 0 to 10 d postweaning, but when microminerals were added to diets, ADG, ADFI, and G:F improved (P < 0.01) from 10 to 35 d and for the overall 35-d period. Pigs fed the basal diet exhibited parakeratosis-like skin lesions, whereas those fed the supplemental microminerals did not. This skin condition was corrected after a diet with the added microminerals was fed. When the basal diet was fed, Hb and Hct declined, but supplemental microminerals increased Hb and Hct values. Liver catalase activity increased (P < 0.01) when microminerals were fed. The Mn superoxide dismutase activity tended to decline quadratically (P = 0.06) when supplemental microminerals were fed above that of the basal diet. Liver plasma glutathione peroxidase activities were greater (P < 0.01) when dietary organic and inorganic micromineral were fed. Liver concentrations of microminerals increased linearly (P < 0.01) as dietary microminerals increased, indicating that the liver was the primary storage organ. Micromineral tissue concentrations were least in pigs fed the basal diet and increased (quadratic, P < 0.01) to the 50% level of organic microminerals in the various tissues collected. The results indicated that innate microminerals, Cu and Mn, from a complex nursery diet may meet the micromineral needs of the weaned pig, but the need for Fe, Se, or Zn was not met by the basal diet.     

Immune responses of piglets to weaning stress: impacts of photoperiod

An acute stress response can be provoked by abrupt social, nutritional, and environmental changes associated with weaning, and this may disrupt homeostasis and thus compromise well-being. Manipulating environmental factors, such as photoperiod, might provide a simple way to reduce the physiological consequences that piglets experience due to weaning stress. The objective of this study was to evaluate the impacts of photoperiod manipulation across various weaning ages on leukocyte populations, lymphocyte proliferation, natural killer cytotoxicity (NK), chemotaxis, phagocytosis, and immunoglobulin G, cortisol, and BW of piglets during the nursery phase. Sixty-eight crossbred piglets were obtained from sows kept on a short-day (8 h of light/d) photoperiod from d 90 of gestation until weaning. Piglets were weaned at 14, 21, or 28 d of age and kept on a short or long (16 h of light/d) photoperiod until 10 wk of age. Piglet BW and blood samples were collected at weaning and at 6, 8, and 10 wk of age. Pigs weaned at 28 d had reduced neutrophil counts (P < 0.001), phagocytosis (P < 0.001), and lymphocyte proliferation (P < 0.05) at weaning compared with those weaned at 14 and 21 d. Pigs weaned at 21 d tended to have lower (P = 0.08) lymphocyte counts than did pigs weaned at 14 or 28 d. Pigs weaned at 14 d had reduced (P < 0.01) NK relative to those weaned at 21 or 28 d. Photoperiod also influenced pig BW and immune status. Generally, those pigs on the long-day photoperiod and weaned at 28 d were heavier (P < 0.001) than their counterparts weaned at 14 or 21 d. At 6 wk of age, NK was greater (P = 0.002) in pigs kept on a long day and weaned at 14 or 21 d than in pigs weaned at 28 d. Phagocytosis was less (P = 0.005) at 6 wk of age, but was greater at 8 wk, in piglets kept on the long day and weaned at 28 d than in long-day pigs weaned at 14 or 21 d. These results suggest that photoperiod differentially influences immune responses in piglets weaned at different ages and indicate an inverse relationship between growth and immune status. Here, weaning at 28 d and a long-day photoperiod was the treatment combination that was most physiologically beneficial to piglets, whereas a 14-d weaning and short-day photoperiod was least physiologically beneficial.     

The effects of postweaning stressors on pig weight change, blood, liver and digestive tract characteristics

Postweaning growth lag in baby pigs weaned at 28 d was studied by using three weaning stress treatments. Treatments consisted of a control in which pigs continued to nurse the dam, had access to a dry feed at 14 d of age and were not weaned until after the study. Pigs were adjusted to liquid and dry feeds at 14 d of age in Treatments 2 and 3, but sows were removed from the pens at 28 d of age in Treatment 2, whereas sows were removed and room temperature lowered to 13 degrees C in Treatment 3. In Treatment 4, sows were removed but pigs were fed the dry diet only from 28 d of age. Blood and tissue were collected and evaluated every 12 h for 48 h on slaughtered pigs and blood was sampled every 12 h for 132 h from pigs catheterized in the vena cava. Pigs weaned with a dry diet in Treatment 4 were the only pigs to lose weight (P less than .01) and have typical symptoms of postweaning growth lag. These pigs had the lowest (P less than .01) mean plasma glucose, highest (P less than .01) free fatty acids and the highest (P less than .05) cortisol concentrations. Their mean duodenal pH also was higher (P less than .01), whereas pigs given both milk and dry diets and stressed by weaning in a warm or cool room (Treatments 2 and 3) had lower (P less than .01) duodenal pH values than pigs continuing to nurse the sow. In this study, pigs having access to milk and dry diets prior to weaning had no adverse symptoms when the sow was removed regardless of whether or not they were exposed to cold after weaning. However, pigs that were abruptly weaned with a dry diet had slow growth, low plasma glucose, high free fatty acids and low liver glycogen.     

Assessment of lactose level in the mid- to late-nursery phase on performance of weanling pigs

An experiment involving a total of 1,320 crossbred pigs was conducted at 3 universities to assess the effects of various levels of lactose in diets during phase 3 (wk 3 and 4 postweaning) of a 4-phase starter program. Pigs were weaned at 15 to 20 d (6.2-kg initial BW) and allotted to 5 treatments. All pigs were fed a complex phase 1 diet (20% lactose) the first week postweaning followed by a complex phase 2 diet (15% lactose) the second week postweaning. Phase 3 diets containing 0, 2.5, 5.0, 7.5, or 10.0% lactose were fed for wk 3 and 4, and then a common, corn-soybean meal diet was fed for an additional 1 to 2 wk (phase 4). The source of lactose was Dairylac 80, which contains 80% lactose. The phase 1, 2, and 3 diets were prepared at one site. Pigs were weighed, and feed intake was determined at weekly intervals. There were 8 replications at each station for a total of 24 replications per treatment with 5 or 23 pigs per pen. As expected, ADG, DFI, and G:F were not affected (P = 0.10) during the initial 2-wk period when all pigs received the same diet. During wk 3 and 4 (phase 3) when the 5 levels of lactose were fed, ADG and ADFI increased linearly (P < 0.01) with increasing levels of lactose, but G:F was not affected (P = 0.10). Although the quadratic component was not significant, ADG and ADFI reached a numerical plateau at the 7.5% inclusion level of lactose during phase 3. Compared with pigs fed the diet without lactose, the 7.5% level of lactose resulted in 350 g of additional BW gain coupled with 420 g of additional feed consumed per pig during phase 3, and most of the additional BW gain (294 g) was maintained through the end of the 5- to 6-wk study. These results suggest that pigs respond to dietary lactose during the mid to latter phase of the nursery period and that the response was obtained under different management and facility conditions.     

Effect of chito-oligosaccharide on growth performance, intestinal barrier function, intestinal morphology and cecal microflora in weaned pigs

A total of 180 weanling pigs (21 ± 3 d of age; 5.98 ± 0.04 kg) were used to investigate the effect of chito-oligosaccharide (COS) on growth performance, intestinal barrier function, intestinal morphology, and cecal microflora. Based on initial BW, gender and litter, the pigs were given 5 treatments during a 14-d feeding experiment, including a basal diet (control), 3 diets with COS supplementation (200, 400, or 600 mg/kg), and a diet with colistin sulfate (CSE) supplementation (20 mg/kg). Six randomly selected pigs from each treatment were used to collect serum, duodenal, jejunal, ileal, and cecal samples on d 7 and 14 postweaning. From d 1 to 7 postweaning, pigs fed COS or CSE had greater ADG and ADFI compared with the control pigs. From d 1 to 14, diets with either 400 or 600 mg/kg COS, or 20 mg/kg CSE increased (P < 0.05) ADG and G:F compared with the control diet. No significant differences were observed in ADG, ADFI, and G:F between the pigs fed COS and CSE. Pigs fed either 400 or 600 mg/kg COS, or 20 mg/kg CSE had less (P < 0.05) diamine oxidase (DAO) in the serum, but greater concentration of (P < 0.05) DAO in jejunal mucosa, than the control pigs on d 7 postweaning. Treatments did not affect villous height and crypt depth of the duodenum, jejunum, or ileum. Pigs fed COS at 400 mg/kg had greater (P < 0.05) concentration of Bifidobacteria and Lactobacilli in the cecum than pigs fed the control diet and CSE diet on d 7 postweaning. Supplementation of COS or CSE decreased (P < 0.05) the population of cecal Staphylococcus aureus compared with the control diet on d 7 postweaning. The number of cecal Bifidobacteria in pigs fed 600 mg/kg COS was greater (P < 0.05) than that of pigs fed the control diet or CSE diet on d 14 postweaning. No significant differences were observed in Escherichia coli counts in the cecum among treatments. The present results indicate that dietary supplementation of COS at 400 or 600 mg/kg promotes growth performance and improves gut barrier function, increases the population of Bifidobacteria and Lactobacilli, and decreases S. aureus in the cecum of weanling pigs.     

Effects of adding fat to the sow lactation diet on lactation and rebreeding performance

One-hundred-three multiparous sows were randomly assigned to one of two lactation diets containing either no supplemental animal fat (C) or 10% added fat (F) during two seasons, summer (S) and winter (W), in a 2 X 2 factorial arrangement of treatments. Sows were placed on their respective dietary treatments 1 wk prior to farrowing and were fed these diets ad libitum throughout the 28-d lactation period. Weekly feed intake and total feed intake were not affected by diet or season, while weekly metabolizable energy (ME) intake tended to be higher during week 1 and 3, and was higher (P less than .04) during wk 2 for sows fed diet F. Sow weight loss from farrowing to 21 d of lactation and to weaning (28 d) were unaffected by diet or season. Average pig birth weight was .15 kg higher (P less than .01) for pigs born during S compared with those born in W. Sows receiving diet F had heavier litters at 21 d (P less than .01) and heavier average pig 21-d weights (P less than .01). This was primarily due to the 13.1% increase (P less than .04) in estimated milk yield and the higher fat concentration (P less than .001) of milk consumed by the pigs nursing sows fed diet F. Interval between weaning and rebreeding was shortened by 5.9 d (P less than .01) for sows during W than during S, and tended to be lower for sows fed diet F (7.3 d) compared with that of sows fed diet C (9.7 d).(ABSTRACT TRUNCATED AT 250 WORDS)