Effect of body composition on diet selection in finishing pigs

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The objective of this work was to determine if pigs of similar BW, but differing in 10th-rib backfat thickness, would differ in their selection of dietary protein. The first experiment was conducted with gilts and was designed in a 2 × 2 factorial arrangement with the main effects of body fat (lean vs. fat) and feeding program (single vs. choice). Crossbred gilts (n = 32) with an initial BW of 79 kg were sorted into high (2.24 cm, fat) and low backfat (1.51 cm, lean; groups based on real-time ultrasound scans at the 10^th rib. Diets were 1) a low-protein corn-based diet supplemented with crystalline AA (8.5% CP, 0.58% Lys) and 2) a high-protein corn- and soybean meal-based diet (22.7% CP, 1.275% Lys). During wk 1, all pigs were fed a 50:50 mix of the low-protein and high-protein diets. From d 7 to 28, one-half the pigs in the lean and fat groups were given a choice of low- and high-protein diets in separate feeders, whereas the others remained on the 50:50 mix. Initial differences in 10th-rib backfat thickness were maintained through d 28 (fat, 3.02 cm; lean, 2.42 cm). Circulating leptin concentrations were greater in the fat pigs than in the lean pigs (3.84 vs. 3.35 ng/mL; P < 0.05). Average daily gain (1.06 kg/d) and ADFI (2.64 kg/d) were not different between treatment groups. However, the pattern of selection was different in the choice groups such that lean pigs consumed more (64.4%) of the high-protein diet than did fat pigs (35.6%), resulting in a difference in the percentage of protein consumed (lean = 16.9% CP; fat = 12.8% CP). A second experiment of similar design, but with barrows (n = 32; initial BW 69 kg), was conducted. Barrows classified as fat had 2.33 cm of 10th-rib backfat as compared with 1.75 cm in the lean group. The percentage of protein in the diet selected by the fat barrows was not different from that selected by the lean barrows (15.9 vs. 17.4%). The lack of difference in selection pattern in barrows may be accounted for by the relatively smaller difference in body composition between the fat and lean classifications in the barrows in the choice feeding program as compared with body composition of the gilts. These results demonstrate that gilts of similar BW, but differing in composition, likely have different nutrient requirements and diet selection patterns. Although allowing pigs to self-select did not alter growth rate, the results indicated that diet selection can be used to allow pigs to meet their individual nutrient requirements more closely.

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Effect of gonadotropin treatment on estrus, ovulation, and litter size in weaned and anestrous sows

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In the first of 2 experiments, we evaluated the effects on anestrous sows of pretreatment with FSH to stimulate the growth of small follicles, followed by eCG to stimulate the growth of medium follicles, estrus, and ovulation. In Exp. 2, we examined the effect of sows receiving 400 IU of eCG plus 200 IU of hCG (PG 600, Intervet/Schering Plough Animal Health, Boxmeer, the Netherlands) at weaning and then different dose and timing of supplemental hCG. In Exp. 1, a total of 87 multiparous Hypor sows deemed anestrus 7 d after weaning were assigned to intramuscular (i.m.) injection of 1) PG 600, 2) eCG (600 IU), 3) pretreatment with 87.5 IU of FSH on d 7 and 8 plus eCG on d 9, or were 4) noninjected controls. Sows had daily boar contact for 15 d after weaning for estrus detection. Blood samples were obtained on d 9 and 19 and assayed for progesterone to determine ovulation status. The weaning-to-estrus interval, number of sows in estrus and ovulating, farrowing rate, and litter size were not different in treated groups compared with controls. In Exp. 2, a total of 247 Hypor sows were assigned at weaning by parity (1 and 2 or ≥3) to receive 1) an i.m. injection of PG 600, 2) PG 600 supplemented with 100 IU of hCG injected either concurrently or after 24 h, 3) 200 IU of hCG after 24 h, or 4) no injection (controls). Sows were exposed to boars daily for 7 d. After treatment of parity 1 and 2 sows, all gonadotropin-treated groups had an increased number of sows in estrus compared with the control group; weaning-to estrus interval, farrowing rates, and litter size were unaffected. After treatment of parity ≥3 sows, there was no treatment effect on the estrous response and weaning-to-estrus interval; compared with control and PG 600-treated sows, farrowing rate was decreased for sows receiving 200 IU of hCG after 24 h. There was no effect of treatment on litter size. We conclude that gonadotropins can be used to increase estrus response in weaned sows, but that hCG treatment subsequent to PG 600 may be detrimental to sow fertility in parity ≥3 sows. 

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Evaluation of antibiotic effects on phosphorus digestibility and utilization by growing-finishing pigs fed a phosphorus-deficient, corn-soybean meal diet

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Evaluations of the nutritional impact of antibiotics have largely centered on effects related to the digestibility and utilization of protein and energy. Recent research has demonstrated that virginiamycin increases P digestibility. Because of the importance of P in diet cost and in waste management plans, the present study evaluated the potential impact of 2 additional antibiotics, bacitracin methylene disalicylate (bacitracin) and tylosin, on P digestibility in swine. A total of 48 barrows (mean initial BW, 63.0 to 82.9 kg) were used in 2 nutrient balance experiments. A basal cornsoybean meal diet that was not supplemented with any inorganic source of P was used in each experiment. In Exp. 1, two diets were tested: basal vs. basal plus 33.1mg of bacitracin/kg of diet. In Exp. 2, two diets were also tested: basal vs. basal plus 44.1 mg of tylosin/kg of diet. In both experiments, the pigs were fed their diets for a minimum of 12 d before fecal and urine collection, and pigs were fed the diet at 2.7% of BW during the adaptation and collection period. In Exp. 1, the apparent DM, Ca, and P digestibility values for the basal and bacitracin diets were 91.69, 65.96, and 43.03 vs. 91.47, 65.46, and 41.79%, respectively, and did not differ by diet. In Exp. 2, the DM, Ca, and P digestibility values for the basal and tylosin diets were 91.03, 62.17, and 38.80 vs. 91.11, 63.20, and 40.10%, respectively, and did not differ by diet. The effect of the antibiotics on gut microflora was also appraised but the evaluations failed to demonstrate an effect on the microflora measured, with the exception that tylosin decreased the number of phytate-utilizing bacteria . Therefore, because these 2 antibiotics did not demonstrate an improvement in P digestibility, improvements in P digestibility seem to be an antibiotic-specific response rather than a generalized antibiotic response.

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Quantitative trait loci analysis of swine meat quality traits

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A QTL study was performed in large half-sib families to characterize the genetic background of variation in pork quality traits as well as to examine the possibilities of including QTL in a marker-assisted selection scheme. The quality traits included ultimate pH in LM and the semimembranosus, drip loss, and the Minolta color measurements L*, a*, and b* representing meat lightness, redness, and yellowness, respectively. The families consist of 3,883 progenies of 12 Duroc boars that were evaluated to identify the QTL. The linkage map consists of 462 SNP markers on 18 porcine autosomes. Quantitative trait loci were mapped using a linear mixed model with fixed factors (sire, sex, herd, month, sow age) and random factors (polygenic effect, QTL effects, and litter). Chromosome-wide and genome-wide significance thresholds were determined by Peipho’s approach, and 95% Bayes credibility intervals were estimated from a posterior distribution of the QTL position. In total, 31 QTL for the 6 meat quality traits were found to be significant at the 5% chromosome- wide level, among which 11 QTL were significant at the 5% genome-wide level and 5 of these were significant at the 0.1% genome-wide level. Segregation of the identified QTL in different families was also investigated. Most of the identified QTL segregated in 1 or 2 families. For the QTL affecting ultimate pH in LM and semimembranosus and L* and b* value on SSC6, the positions of the QTL and the shapes of the likelihood curves were almost the same. In addition, a strong correlation of the estimated effects of these QTL was found between the 4 traits, indicating that the same genes control these traits. A similar pattern was seen on SSC15 for the QTL affecting ultimate pH in the 2 muscles and drip loss. The results from this study will be helpful for fine mapping and identifying genes affecting meat quality traits, and tightly linked markers may be incorporated into marker-assisted selection programs.

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Phosphorus utilization and characterization of excreta from swine fed diets containing a variety of cereal grains balanced for total phosphorus

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Intrinsic phytase in swine feeds may increase phytate utilization and alter the solubility of the excreted P. The objective of this experiment was to quantify changes in fecal P composition from swine fed a variety of cereal grains containing a range of phytate concentrations and endogenous phytase activities. Twenty-five crossbred barrows (89.3kg) were fed 1 of 5 dietary treatments that were based on wheat, corn, barley, low-phytate barley, or high-fat–low-lignin oats. Experimental diets were formulated to contain 75% of the test grain and were fed for a 7-d acclimation period followed by a 3-d fecal collection period. Total-tract apparent digestibility coefficients were determined for DM, P, and phytate using an indicator method. Fecal P was characterized using solution-state 31P nuclear magnetic resonance spectroscopy. Watersoluble P (WSP) and WSP-to-total P (TP) ratio were determined in the feces. Apparent total-tract digestibility coefficients for P and phytate ranged from 0.33 (barley) to 0.45 (low-phytate barley) and from 0.20 (corn) to 0.79 (oats), respectively. The majority of P excreted in the feces was in the form of phosphate (>47% of TP), and phytate degradation was not related to the endogenous phytase activity in the diet. There was a positive linear relationship between dietary NDF and apparent total-tract phytate digestibility (r2 = 0.82), indicating that greater dietary fiber content may enhance microbial breakdown of phytate in the hindgut. There was a negative relationship between the fecal WSP-to-TP ratio and the percentage of TP that was in the form of phytate in the feces. In summary, our results indicate that the majority of P in the feces of pigs fed diets based on cereal grains is present in the form of phosphate and relatively small amounts of phytate were contained in the excreta. The exception to this was the corn diet, for which 45% of the total fecal P was in the form of phytate. Hydrolysis of phytate in the gut did not appear to be related to the content of either phytate or phytase in the grain, but was related to dietary fiber concentration.

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Effect of reduced dietary calcium concentration and phytase supplementation on calcium and phosphorus utilization in weanling pigs with modified mineral status

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The present study was conducted to assess the effect of 2 dietary Ca concentrations on P and Ca digestive and metabolic utilization in weanling pigs fed diets providing practical concentrations of P, with or without phytase. The responses of pigs fed diets adequate or moderately deficient in Ca and P postweaning were compared. A total of 60 pigs weaned at 28 d of age were used. Two groups of 30 pigs with differing mineral status resulted from a 10-d depletion period, during which the animals received depletion diets (DD) that consisted of corn-soybean meal with either 1.42% Ca and 0.80% P (DD+) or 0.67% Ca and 0.43% P (DD−), designed to achieve the same Ca:digestible P ratio. At the end of the depletion period, a plasma sample was taken from each pig and 12 pigs (6 from each group) were slaughtered for bone assessment to establish the baseline mineral status. The animals fed the DD− diet had signs of P deficiency with reduced plasma P (13%) and femur ash concentration (8%), and increased plasma Ca (9%) and alkaline phosphatase activity (31%). For the subsequent 25-d period, the remaining 24 pigs from each group were fed 1 of 4 repletion diets: 1) 0.56% P, 1.06% Ca; 2) 0.56% P, 0.67% Ca; 3) diet 1 + 1,000 phytase units (FTU) of Natuphos phytase/kg; and 4) diet 2 + 1,000 FTU of Natuphos phytase/kg. Total feces and urine were collected from d 5 to 11, and a blood sample was taken from each pig at d 11 and 25. The initial moderate P deficiency (DD−) stimulated Ca absorption (5%), irrespective of the repletion diet, and stimulated P absorption (5%; DD × phytase) , only when the diets contained phytase. At the end of the repletion period, because of these compensatory phenomena, the depleted pigs achieved full recovery of femur DM and ash weight when they received phytase, whereas ash concentration tended to remain reduced by 3%. Phosphorus digestibility was improved in the diets supplemented with phytase (73.0 vs. 56.0%), whereas an increase in dietary Ca decreased P digestibility (65.6 vs. 63.4%). Those 2 effects were independent, indicating that dietary Ca reduced equally P digestibility with and without phytase and did not influence the efficiency of phytase in releasing P in the digestive tract. In pigs fed diets with phytase, however, the reduction of Ca (Ca:P from 1.9 to 1.3) increased urinary P losses 5-fold. Those extra losses were due to a lack of Ca for skeleton ash deposition, resulting in a 4% reduction in femur ash concentration. In the end, reducing the dietary Ca:P from 1.9 to 1.3 in a practical diet containing 0.56% P did not improve the efficiency of phytase in releasing P. Moreover, the reduction in dietary Ca (Ca:P) caused an imbalance between Ca and P that impaired bone mineralization.

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Effect of maternal fish oil and seaweed extract supplementation on colostrum and milk composition, humoral immune response, and performance of suckled piglets

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An experiment with a 2 × 2 factorial arrangement of treatments (n = 10 sows/treatment) was conducted to investigate the effect of maternal dietary supplementation with seaweed extract (SWE: 0 vs. 10.0 g/d) and fish oil (FO) inclusion (0 vs. 100 g/d) from d 109 of gestation until weaning (d 26) on sow colostrum and milk composition, humoral immune response on d 5 and 12 of lactation, and suckling piglet performance. Furthermore, the influence of dietary treatment on the phagocytic activity of whole blood white cells at weaning was examined. The SWE (10 g) contained laminarin (1 g), fucoidan (0.8 g), and ash (8.2 g) and was extracted from a Laminaria spp. The FO contained approximately 40% eicosapentaenoic acid and 25% docosahexaenoic acid. The SWE-supplemented sows had greater colostrum IgG and milk protein concentrations on d 12 of lactation compared with non-SWE-supplemented sows. Piglets suckling SWE-supplemented sows had greater serum IgG and IgA concentrations on d 5 and IgG concentrations on d 12 of lactation compared with those suckling non SWE-supplemented sows. In contrast, FO supplementation exerted a suppressive effect on piglet serum IgA concentrations on d 5 of lactation compared with non- FO-supplemented diets. Dietary FO supplementation enhanced the n-3 PUFA proportion of sow milk and piglet serum at weaning. Piglets suckling SWE-supplemented sows had a greater percentage of Escherichia coli phagocytizing leukocytes and a reduced percentage of E. coli phagocytizing lymphocytes compared with non-SWEsupplemented sows. Piglets suckling FO-supplemented sows had a greater percentage of leukocytes and lymphocytes phagocytizing E. coli compared with non-FO-supplemented sows. However, total leukocyte, lymphocyte, monocyte, and neutrophil numbers were not influenced by sow dietary treatment. Average piglet weaning weight and ADG between birth and weaning were not influenced by sow dietary treatment. In conclusion, the current study demonstrates that SWE supplementation from d 109 of gestation until weaning enhanced colostral IgG concentrations and circulatory IgG concentrations in suckled piglets on d 5 and 12 of lactation. Furthermore, the percentage of leukocytes and lymphocytes phagocytizing E. coli at weaning increased in piglets suckling FO-supplemented sows, indicating an enhancement of immune function against presenting pathogens. However, the combination of SWE and FO bestowed no positive effect on immune responses investigated in the current study.

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Effect of distillers dried grains with solubles and ractopamine (Paylean) on quality and shelf-life of fresh pork and bacon

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Pigs (n = 240) were allotted in a 5 × 2 factorial arrangement with 5 levels of distillers dried grains with solubles (DDGS): 0, 15, 30, 45, and 60%, and 2 ractopamine (RAC) levels: 0 and 5 mg/kg. Four pigs per pen (2 barrows, 2 gilts) closest to pen mean BW were used for meat quality evaluation. Loins (n = 119) were evaluated for objective color; moisture and fat; subjective color, marbling, and firmness; and drip loss. Bellies (n = 119) were evaluated for weight, length, width, thickness, objective fat color, and firmness. Cured bellies were evaluated for pump yield, cook loss, and sliced bacon cook loss. Loin thiobarbituric acid reactive substances (TBARS) were evaluated on enhanced (salt and phosphate) boneless chops held in modified atmosphere (80% O2/20% CO2) packages for 0, 7, 14, and 21 d. Bacon TBARS were evaluated on sliced bacon held in vacuum packages for 0, 28, 56, and 84 d. Fat samples were collected from each jowl and belly and evaluated for fatty acid profile and iodine value (IV). Increasing DDGS decreased subjective marbling and firmness, and increased drip loss. Distillers dried grains with solubles did not affect loin pH, subjective or objective color, percent moisture, or percent fat. The RAC decreased subjective color, marbling, and a*. Increasing DDGS decreased belly weight, length, thickness, and firmness; decreased belly fat L*; and increased belly cook loss. Ractopamine did not affect any belly measurements, and there were no DDGS × RAC interactions. Distillers dried grains with solubles did not affect loin TBARS at 0, 7, or 14 d. At 21 d, loin TBARS from 30, 45, and 60% DDGS groups were increased compared with 0 and 15% groups. Ractopamine did not affect loin TBARS, and there were no DDGS × RAC interactions. Distillers dried grains with solubles and RAC did not affect bacon TBARS. Increasing DDGS increased belly and jowl IV, and decreased MUFA:PUFA in belly and jowl fat. Ratio of SFA:unsaturated fatty acids decreased in jowl and belly fat. Ractopamine did not affect fatty acid profiles or IV, and there were no DDGS × RAC interactions. Results indicate that increased DDGS have minimal effects on loin quality, but decrease belly quality, bacon processing characteristics, and fat stability. Ractopamine does not negatively affect these characteristics and does not interact with DDGS.

Nonsolar energy use and one-hundred-year global warming potential of Iowa swine feedstuffs and feeding strategies

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Demand for nonsolar energy and concern about the implications of fossil fuel combustion have encouraged examination of energy use associated with agriculture. The United States is a global leader in pig production, and the United States swine industry is centered in Iowa. Feed is the largest individual input in pig production, but the energy consumption of the Iowa swine feed production chain has yet to be critically examined. This analysis examines nonsolar energy use and resulting 100-yr global warming potential (GWP) associated with the swine feed production chain, beginning with cultivation of crops and concluding with diet formulation. The nonsolar energy use and accompanying 100-yr GWP associated with production of 13 common swine feed ingredients are estimated. Two diet formulation strategies are considered for 4 crop sequence × ingredient choice combinations to generate 8 crop sequence × diet formulation scenarios. The first formulation strategy (simple) does not include synthetic AA or phytase. The second strategy (complex) reduces CP content of the diet by using l-lysine to meet standardized ileal digestibility lysine requirements of pigs and includes the exogenous enzyme phytase. Regardless of crop sequence × diet formulation scenario, including the enzyme phytase is energetically favorable and reduces the potential excretion of P by reducing or removing inorganic P from the complete diet. Including l-lysine reduces the CP content of the diet and requires less nonsolar energy to deliver adequate standardized ileal digestible lysine than simply feeding soybean meal. Replacing soybean meal with full-fat soybeans is not energetically beneficial under Iowa conditions. Swine diets including dried distillers grains with solubles and crude glycerol require approximately 50% more nonsolar energy inputs than corn-soybean meal diets or cornsoybean meal diets including oats. This study provides essential information on cultivation, processing, and manufacture of swine feed ingredients in Iowa that can be coupled with other models to estimate the nonsolar energy use and 100-yr GWP of pig production.

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Fermented soybean meal as a vegetable protein source for nursery pigs: I. Effects on growth performance of nursery pigs

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Four experiments were conducted using 671 nursery pigs to evaluate fermented soybean meal (FSBM) as a new vegetable protein source for nursery pigs. In Exp. 1, a total of 192 pigs weaned at 19.2 d of age were fed 3 diets (8 pens per treatment) for 2 wk: a control diet (without FSBM) and 2 diets with 3 and 6% FSBM replacing soybean meal, followed by a common diet for the next 2 wk. In Exp. 2, a total of 160 pigs weaned at 21.6d of age were fed 4 diets (5 pens per treatment) for 2 wk: a control diet (without FSBM but with 25% dried skim milk; DSM) and 3 diets with 3, 6, and 9% FSBM replacing DSM based on CP. Concentrations of CP, Lys, Met, Thr, and Trp were kept consistent among diets in Exp. 1 and 2. In Exp. 3, a total of 144 pigs weaned at 22.1d of age were fed 3 diets (6 pens per treatment) for 2 wk: a control diet (without FSBM but with 40% DSM) and 2 diets with 5 and 10% FSBM replacing DSM based on CP. Concentrations of CP, Lys, Met, Thr, Trp, and lactose were kept consistent among diets. In Exp. 4, a total of 175 pigs weaned at 20.7d of age were fed 5 diets (5 pens per treatment) for 3 wk: a basal diet [15.5% CP without plasma protein (PP) and FSBM], 2 diets (18.4% CP) with 3.7% PP or 4.9% FSBM, and 2 diets (21.2% CP) with 7.3% PP or 9.8% FSBM. Concentrations of Lys, Met, Thr, and Trp were kept consistent among diets with the same CP concentrations. Pigs had access to feed and water ad libitum and their BW and feed intake were measured weekly for all experiments. Use of up to 6% FSBM replacing soybean meal improved G:F and diarrhea scores of nursery pigs (Exp. 1). Use of up to 9% FSBM replacing DSM reduced ADG and G:F (Exp. 2). When lactose concentrations were equal, FSBM could replace up to 10% DSM without adverse effects on ADG and G:F (Exp. 3). Relative bioavailability of protein in FSBM to PP was 99.1% (Exp. 4). Collectively, FSBM can serve as an alternative protein source for nursery pigs at 3 to 7 wk of age, possibly replacing the use of DSM and PP but excluding the first week postweaning for PP when balancing for AA and lactose.

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