Effect of chronic cyclic heat stress and supplemented inorganic and organic zinc source levels on grow-finish pig growth performance and estimated body composition.

Zinc (Zn) supplementation has proved to mitigate the effects of heat stress with varying effects evident with Zn source during acute heat events. However, the effects of Zn supplementation during long-term summer weather patterns have yet to be explored. Therefore, the objective of this study was to identify the effects of supplementation source and level of Zn to mitigate the negative effects of long-term, cyclic heat stress in finishing swine. Six hundred cross-bred pigs were housed under thermoneutral (TN) or cyclic heat (HS) conditions simulating summer heat with acute 3-d heat waves for a 70-d study. Thermoneutral conditions were 16.7 to 18.9 °C throughout the study. HS pigs were housed at the same temperature as TN from days 0 to 18, then 28 °C/24 °C for 12 h/12 h on days 18 to 21, followed by 30 °C/26.7 °C for 12 h/12 h on days 24 to 70, except during acute heat (32 to 33 °C/29 to 30 °C, 12 h/12 h) on days 21 to 24, 42 to 45, and 63 to 66. Treatments were arranged in a 2 × 6 factorial with main effects of environment (HS vs. TN) and dietary available Zn supplementation: (1) 50 mg/kg zinc oxide (ZnO), (2) 130 mg/kg ZnO, (3) 50 mg/kg of organic Zn (Availa Zn), (4) 50 mg/kg ZnO + 40 mg/kg organic Zn, (5) 50 mg/kg ZnO + 60 mg/kg organic Zn, and (6) 50 mg/kg ZnO + 80 mg/kg organic Zn. Pigs (5 pigs/pen) were blocked by initial body weight (72.2 kg) and randomly allotted to 1 of 12 temperature and diet treatment combinations across 10 replicates. Body weight and feed intake were determined at the beginning and end of each acute heat event. All pigs were ultrasonically scanned at the 10th rib (TR) to predict loin muscle area (LMA), backfat (BF), and percent lean. Data were analyzed by the MIXED procedure in SAS with pen as the experimental unit. At day 63, HS pigs were lighter (P < 0.05), had lower overall average daily gain (ADG; P < 0.05) and average daily feed intake (P < 0.05). A diet-by-environment interaction was observed for overall ADG (P < 0.05) with diet 5 HS pigs having a 3.9% reduction in ADG whereas diet 6 had 14.4% reduction in ADG, while under TN temperatures diet 6 had the greatest overall ADG of all treatments. Other diets were intermediate in their ADG under both HS and TN conditions. Pigs under HS had less BF at the TR (P < 0.05) and a smaller LMA (P < 0.05), and a greater calculated percent lean (P < 0.05). Our results indicate that a blend of supplemental Zn sources at 50/60 mg/kg may mitigate the reduction in growth performance due to HS. While not directly contrasted, the NRC requirement of 50 mg/kg Zn may be too low to optimize finishing pig growth performance under both TN and HS conditions.

The effect of reduced CP, synthetic amino acid supplemented diets on growth performance and nutrient excretion in wean to Finish swine.

Mixed sex pigs (n = 720) were placed in 12 rooms (Purdue Swine Environmental Research Building) to measure the effect of reduced crude protein (CP), amino acid (AA)-supplemented diets on growth and the carcass. Pigs were blocked by body weight (BW) and gender and allotted to room and pen (10 mixed-sex pigs/pen). Pigs were fed a nine-phase, wean-finish program. Control pigs consumed corn-soybean meal-distiller's dried grains with solubles (DDGS) diets containing no to minimal (Met) synthetic AA. The 2X diet was formulated to meet the seventh most-limiting AA, and balanced using synthetic AAs to meet all AA needs. The 1X diet was formulated to meet a CP value halfway between the control and 2X diet, and also balanced using synthetic AAs to meet all AA needs. Diets were formulated to identical net energy concentrations and balanced to meet standard ileal digestible NRC 2012 AA requirements. Pit vacuum samples were collected at the end of each growth phase for analyses of nitrogen, C and dry matter (DM). Pigs fed the Control and 1X diet grew faster (P < 0.005), had greater gain:feed (P < 0.001), and were heavier at market (P < 0.001) than animals fed the 2X diet. No consistent effects of diet were observed on average daily feed intake. Carcass data were analyzed for sex, diet and sex*diet effects. Reductions in dietary CP resulted in a linear reduction in ammonium nitrogen excretion per kg of BW gain in Nursery (P < 0.001) and Grow-Finish (P < 0.001) phases. Reductions in dietary CP, with synthetic AA supplementation resulted in a linear reduction in total nitrogen excreted per kg BW gain in the Grow-Finish phase (P < 0.001) and overall (P < 0.001). Total mineral excretion per kg gain was reduced in pigs fed 1X and 2X diets compared with control-fed pigs (P < 0.005). Reductions in dietary CP of ~3 and 5%-units from wean-finish result in reductions of total N excretion of 11.7 and 24.4%, respectively. Reduced performance and carcass characteristics observed in pigs fed the 2X diets indicates an inaccurate estimate of NRC 2012 AA requirements or ratios to lysine in a low CP diet.

Characterizing the postnatal hypothalamic-pituitary-adrenal axis response of in utero heat stressed pigs at 10 and 15 weeks of age.

In utero heat stress alters postnatal physiological and behavioral stress responses in pigs. However, the mechanisms underlying these alterations have not been determined. The study objective was to characterize the postnatal hypothalamic-pituitary-adrenal axis response of in utero heat-stressed pigs. Pigs were subjected to a dexamethasone suppression test followed by a corticotrophin releasing hormone challenge at 10 and 15 weeks of age. Following the challenge, hypothalamic, pituitary, and adrenal tissues were collected from all pigs for mRNA abundance analyses. At 10 weeks of age, in utero heat-stressed pigs had a reduced (P < 0.05) cortisol response to the corticotrophin releasing hormone challenge versus controls. Additionally, the cortisol response tended to be greater overall (P < 0.10) in 15 versus 10-week-old pigs in response to the dexamethasone suppression test. The cortisol response tended to be reduced overall (P < 0.10) in 15 versus 10-week-old pigs in response to the corticotrophin releasing hormone challenge. Hypothalamic corticotropin releasing hormone mRNA abundance tended to be greater (P < 0.10) in in utero heat-stressed versus control pigs at 15-weeks of age. In summary, in utero heat stress altered some aspects of the hypothalamic-pituitary-adrenal axis related to corticotropin releasing hormone signaling, and age influenced this response.

Replacing dietary antibiotics with 0.20% l-glutamine in swine nursery diets: impact on intestinal physiology and the microbiome following weaning and transport.

Previous research demonstrates that supplementing 0.20% l-glutamine (GLN) in the diets of newly weaned and transported pigs improves growth rate to a similar extent as providing dietary antibiotics (AB). However, research comparing the effects of GLN vs. AB on intestinal physiology and the microbiome is limited. Therefore, the study objective was to compare the effects of supplementing nursery diets with GLN, AB, or no dietary antibiotics (NA) on intestinal physiology and the microbiome of pigs in a production environment following weaning and transport. Mixed-sex piglets (N = 480; 5.62 ± 0.06 kg body weight [BW]) were weaned (18.4 ± 0.2 d of age) and transported for 12 h in central Indiana, for two replicates, during the summer of 2016 and the spring of 2017. Pens were blocked by BW and allotted to one of the three dietary treatments (n = 10 pens/dietary treatment/replicate [8 pigs/pen]): AB (chlortetracycline [441 ppm] + tiamulin [38.6 ppm]), GLN (0.20% as-fed), or NA fed for 14 d. From day 14 to 34, pigs were fed common AB-free diets in two phases. On day 33, villus height:crypt depth tended to be increased (P = 0.07; 7.0%) in GLN and AB pigs vs. NA pigs. On day 33, glucagon-like peptide 2 (GLP-2) mRNA abundance was decreased (P = 0.01; 50.3%) in GLN and NA pigs vs. AB pigs. Crypt depth was increased overall on day 33 (P = 0.01; 16.2%) during the spring replicate compared with the summer replicate. Villus height:crypt depth was reduced (P = 0.01; 9.6%) during the spring replicate compared with the summer replicate on day 33. On day 13, tumor necrosis factor-alpha and occludin mRNA abundance was increased (P ≤ 0.04; 45.9% and 106.5%, respectively) and zonula occludens-1 mRNA abundance tended to be greater (P = 0.10; 19.2%) in the spring replicate compared with the summer replicate. In addition, AB pigs had increased (P = 0.01; 101.3%) GLP-2 mRNA abundance compared with GLN and NA pigs. Microbiome analysis indicated that on day 13, dietary treatment altered the microbiota community structure (P = 0.03). Specifically, the AB pigs tended to be distinct from both the NA and GLN pigs (P = 0.08), and Lactobacillus was increased nearly 2-fold in AB compared with NA pigs (q = 0.04) and GLN pigs (q = 0.22). In conclusion, GLN supplementation tended to improve some morphological markers of intestinal health similarly to AB pigs, while the microbiome composition in GLN pigs was more similar to NA pigs than AB pigs.

Effects of increasing dietary L-glutamine to replace antibiotics on pig health and performance following weaning and transport.

Supplementing nursery diets with 0.20% L-glutamine (GLN) may provide similar growth and health benefits as dietary antibiotics, but it was unknown if greater inclusion levels may provide additional benefits. Therefore, the study objective was to evaluate the impact of replacing dietary antibiotics with increasing GLN levels on growth performance, therapeutic antibiotic treatment rates, welfare measures, and production costs in pigs after weaning and transport. We hypothesized that withholding dietary antibiotics may negatively impact performance and increase therapeutic treatment rate, and that diet supplementation with 0.20% to 1.00% GLN may incrementally improve productivity and reduce therapeutic antibiotic treatment rates compared with dietary antibiotics. Mixed sex pigs (N = 308; 5.64 ± 0.06 kg body weight [BW]) were weaned (19.1 ± 0.2 d of age) and transported in central Indiana in 2017. Pigs were blocked by BW and allotted to one of seven dietary treatments (n = 8 pens/dietary treatment): dietary antibiotics (positive control [PC]; chlortetracycline [441 mg/kg] + tiamulin [38.6 mg/kg]), no antibiotics or added GLN (negative control [NC]), 0.20% GLN, 0.40% GLN, 0.60% GLN, 0.80% GLN, or 1.00% GLN fed for 14 d. From d 14 to 35, pigs were provided nonantibiotic common diets in two phases. Overall, average daily gain (ADG) was reduced (P = 0.01; 17.7%) from d 0 to 14 in NC, 0.20% GLN, 0.60% GLN, 0.80% GLN, and 1.00% GLN pigs compared with PC pigs, but no ADG differences were detected between 0.40% GLN pigs and PC pigs. Increasing GLN in the diet tended to increase ADG (linear; P = 0.10). Overall, d 35 BW was greater (P = 0.01) in 0.80% GLN and PC pigs compared with NC, 0.20% GLN, and 0.60% GLN pigs, and was greater for 0.40% GLN and 1.00% GLN pigs vs. 0.20% GLN pigs. However, no d 35 BW differences were detected (P > 0.05) between PC, 0.40% GLN, 0.80% GLN, and 1.00% GLN pigs. Increasing GLN in the diet tended to increase (linear; P = 0.08) d 35 BW. Overall, income over feed and therapeutic injectable antibiotics cost (IOFAC) for enteric and unthrifty challenges were greater (P = 0.02) in 0.80% GLN pigs compared with NC, 0.20% GLN, and 0.60% GLN pigs, but no IOFACs for enteric and unthrifty challenges differences were detected between 0.80% GLN pigs and 0.40% GLN, 1.00% GLN, and PC pigs. In conclusion, GLN supplemented pigs had improved performance after weaning and transport compared with the NC pigs with 0.40% GLN being the most effective level.

Replacing dietary antibiotics with 0.20% l-glutamine and synbiotics following weaning and transport in pigs.

Dietary antibiotic use has been limited in swine production due to concerns regarding antibiotic resistance. However, this may negatively impact the health, productivity, and welfare of pigs. Therefore, the study objective was to determine if combining dietary synbiotics and 0.20% l-glutamine would improve pig growth performance and intestinal health following weaning and transport when compared with traditionally used dietary antibiotics. Because previous research indicates that l-glutamine improves swine growth performance and synbiotics reduce enterogenic bacteria, it was hypothesized that supplementing diets with 0.20% l-glutamine (GLN) and synbiotics (SYN; 3 strains of Lactobacillus [1.2 × 10^9 cfu/g of strain/pig/d] + ß-glucan [0.01 g/pig/d] + fructooligosaccharide [0.01 g/pig/d]) would have an additive effect and improve pig performance and intestinal health over that of dietary antibiotics. Mixed-sex pigs (N = 226; 5.86 ± 0.11 kg body weight [BW]) were weaned (19.4 ± 0.2 d of age) and transported for 12 h in central Indiana. Pigs were blocked by BW and allotted to one of two dietary treatments (5 to 6 pigs per pen): antibiotics (positive control [PC]; chlortetracycline [441 ppm] + tiamulin [38.5 ppm]), no antibiotics (negative control [NC]), GLN, SYN, or the NC diet with both the GLN and SYN additives (GLN + SYN) fed for 14 d. From day 14 post-weaning to the end of the grow-finish period, all pigs were provided common antibiotic-free diets. Data were analyzed using PROC GLIMMIX and PROC MIXED in SAS 9.4. Overall, haptoglobin was greater (P = 0.03; 216%) in NC pigs compared with PC pigs. On day 13, GLN and PC pigs tended to have reduced (P = 0.07; 75.2% and 67.3%, respectively) haptoglobin compared with NC pigs. On day 34, the jejunal goblet cell count per villi and per millimeter tended to be greater (P < 0.08; 71.4% and 62.9%, respectively) in SYN pigs compared with all other dietary treatments. Overall, jejunal mucosa tumor necrosis factor-alpha (TNFα) gene expression tended to be greater (P = 0.09; 40.0%) in NC pigs compared with PC pigs on day 34. On day 34, jejunal mucosa TNFα gene expression tended to be greater (P = 0.09; 33.3%, 41.2%, and 60.0%, respectively) in GLN pigs compared with SYN, GLN + SYN, and PC pigs. Although it was determined that some metrics of pig health were improved by the addition of GLN and SYN (i.e., haptoglobin and goblet cell count), overall, there were very few differences detected between dietary treatments and this may be related to the stress load incurred by the pigs.

Replacing dietary antibiotics with 0.20% l-glutamine in swine nursery diets: impact on health and productivity of pigs following weaning and transport1,2,3.

Antibiotic use has been limited in U.S. swine production. Therefore, the objective was to determine whether supplementing l-glutamine at cost-effective levels can replace dietary antibiotics to improve piglet welfare and productivity following weaning and transport. Based on previous research, we hypothesized that withholding dietary antibiotics would negatively affect pigs while diet supplementation with 0.20% l-glutamine (GLN) would have similar effects on pig performance and health as antibiotics. Mixed sex piglets (N = 480; 5.62 ± 0.06 kg BW) were weaned (18.4 ± 0.2 d of age) and transported for 12 h in central Indiana, for 2 replicates, during the summer of 2016 and the spring of 2017. Pigs were blocked by BW and allotted to 1 of 3 dietary treatments (n = 10 pens/dietary treatment/replicate [8 pigs/pen]); antibiotics (A; chlortetracycline [441 ppm] + tiamulin [38.6 ppm]), no antibiotics (NA), or GLN fed for 14 d. On days 15 to 34, pigs were provided common antibiotic-free diets in 2 phases. Data were analyzed using PROC MIXED in SAS 9.4. Day 14 BW and days 0 to 14 ADG were greater (P = 0.01) for A (5.6% and 18.5%, respectively) and GLN pigs (3.8% and 11.4%, respectively) compared with NA pigs, with no differences between A and GLN pigs. Days 0 to 14 ADFI increased for A (P < 0.04; 9.3%) compared with NA pigs; however, no differences were detected when comparing GLN with A and NA pigs. Once dietary treatments ceased, no differences (P > 0.05) in productivity between dietary treatments were detected. On day 13, plasma tumor necrosis factor alpha (TNF-α) was reduced (P = 0.02) in A (36.7 ± 6.9 pg/mL) and GLN pigs (40.9 ± 6.9 pg/mL) vs. NA pigs (63.2 ± 6.9 pg/mL). Aggressive behavior tended to be reduced overall (P = 0.09; 26.4%) in GLN compared with A pigs, but no differences were observed between A and GLN vs. NA pigs. Huddling, active, and eating/drinking behaviors were increased overall (P < 0.02; 179%, 37%, and 29%, respectively) in the spring replicate compared with the summer replicate. When hot carcass weight (HCW) was used as a covariate, loin depth and lean percentage were increased (P = 0.01; 4.0% and 1.1%, respectively) during the spring replicate compared with the summer replicate. In conclusion, GLN supplementation improved pig performance and health after weaning and transport similarly to A across replicates; however, the positive effects of A and GLN were diminished when dietary treatments ceased.