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The purpose of this experiment was to evaluate the effects of betaine and superdosed phytase on boar reproduction during mild heat stress. Twenty-seven mature (36 wk old), crossbred boars [Duroc × (Landrace × Yorkshire)] were randomly allocated to treatment and were fed 2.6 kg/d of 1 of 3 corn, soybean meal diets: control (CNT; 250 phytase units/kg Escherichia coli phytase; n = 9), betaine (BET; 250 phytase units/kg E. coli phytase and 0.6% betaine; n = 9), and betaine and superdosed phytase (BP; 2,500 phytase units/kg E. coli phytase and 0.6% betaine; n = 9). The experiment was split into 4 environmental phases (4 wk/phase) consisting of pre-heat stress (26°C), heat stress (30.2°C), post-heat stress 1 (16.7°C), and post-heat stress 2 (17.5°C). Semen was collected weekly from each boar and was evaluated for semen quantity and quality parameters. Total motility, progressive motility and percentage of morphologically normal sperm were reduced in the heat stress period (P

The objectives of this research were to use currently available models of nutrient requirements to estimate heat production of lactating sows and to characterize potential sources of variation. Heat production was estimated using NRC (2012) . Sow BW, mean daily litter weight gain ( Cabezon et al., 2016a ), and daily feed intake data ( Cabezon et al., 2016b ) from 317 sows of 2 genetic lines (164 and 153 sows) were used to predict the heat production (watts) for each day of lactation. Data were sorted in 4 parity groups: parity 1 (n = 80, P1), parity 2 (n = 57, P2), parities 3 to 5 (n = 142, P3–5), and parity 6 and greater sows (n = 38, P6+). No genetic line differences were observed for the predicted daily heat production (PDHP). The PDHP were 459, 507, 541, and 555 W for P1, P2, P3–5, and P6+ sows, respectively. Parity 1 sows had less PDHP than sows with greater parities (P

This study was conducted to evaluate the underlying physiological changes during heat stress and the effect of betaine supplementation in lactating sows. Twenty sows were housed in 2 rooms (each with 10 sows) to simulate heat stress (HS: 31°C from 0800 to 1600 h and 26°C for the rest of the day) or thermoneutral (TN: 22°C during the entire trial) conditions. Treatments were randomly allotted to each sow to receive 0.00% or 0.22% of a betaine supplement in their diets. Sows were blocked by parity as they entered the farrowing rooms at d 110 to 112 of gestation. Sows housed in the HS condition had ad libitum access to feed. Sows housed in the TN condition were pair fed with sows in the HS room. Follicle size was measured every 12 h with a real time ultrasound from weaning to ovulation. Betaine supplemented sows had 0.23°C lower rectal temperature than control sows (P = 0.048). Respiration rates and rectal and skin temperatures were 36 breaths/min and 0.44 and 3.55°C greater under HS than TN conditions, respectively (P 0.44) or environments (P > 0.25). The mean follicle diameter was smaller under HS than TN conditions (P = 0.003). Betaine supplemented sows had greater follicle diameter than control sows (P = 0.043). The time to ovulation from weaning was 2.1 d longer in HS sows than TN sows (P = 0.005).

The objective of this experiment was to evaluate the effects of betaine supplementation during lactation in hot summer months on piglet growth and sow subsequent reproductive performance. The betaine feeding portion of the experiment was conducted between December 2014 and March 2015 with subsequent litter data completed by July 2015 in Rancagua, Chile. Dietary treatments were allotted randomly to concurrent farrowing rooms of sows. Sows were fed diets supplemented with either 0% (n = 193) or 0.3% (n = 175 sows) of betaine-HCl (70.7% betaine) from 2 d before their farrowing due date until weaning (average lactation length = 21.0 d). Betaine supplemented sows had 3.90% greater ADFI during lactation than control sows (P = 0.005). Treatments by parity interactions were significant for ADFI and sow BW loss (P = 0.008 and P = 0.005, respectively). Parity 2 sows that received betaine supplementation had greater ADFI (6.89 versus 6.17 kg/d) and 6.70 kg less BW loss than parity 2 control sows (P

Daily feed intakes (DFI) of 565 lactation records were evaluated for sows of 2 genetic lines, PIC C-22 and L-42. Sows were fed ad libitum during the entire 21-d lactation period with a diet supplemented with either 0 or 0.3% betaine-HCl. Sows were fed corn–soybean based diets (3.32 Mcal of ME/kg). The DFI data were fitted to generalized Michaelis-Menten functions of day of lactation. The generalized Michaelis-Menten function {DFI i, t (kg/d) = DFI 0 + (DFI A − DFI 0 )( t / K ) C /[1 + ( t / K ) C ]} with 2 random effects for DFI (dfi A i ) and intercept (dfi 0 i ) with K as a linear function of dfi 0 i provided the best fit to the DFI data (R 2 = 0.474). The addition of a single covariate including daily degree-hours above 24°C (DGH24), daily maximum temperature (MaxT), or daily mean temperature (MeanT) of the current day were considerable ( P P 0 i and dfi A i . Betaine-supplemented sows had a 0.27 kg/d greater mean for dfi A i ( P = 0.004). Substantially greater DFI was found at the end of lactation in betaine-supplemented parity 1 and parity 2 sows ( P = 0.012 and 0.005, respectively). Parity was important for both random effects ( P A i ( P = 0.006 and 0.049, respectively).

Crossbred barrows were blocked by BW (28.4 kg) and allocated to 1 of 4 treatments (10 pens per treatment, 5 per pen) in a 2 × 2 factorial arrangement, with 2 NE levels [control vs. low (LE)] and with or without 7.5 mg/kg ractopamine hydrochloride (RAC) during the last 21 d of the 105-d feeding trial. The objectives were (1) to evaluate the BW growth, energy intakes, and energetic efficiency of high growth barrows fed high and low energy density diets during the grow-finisher phases, and (2) to evaluate the effect of feeding RAC when pigs were fed either high and low energy diets. Control diets were based on corn, soybean meal, corn DDGS, and LE diets were created by adjusting inclusion rates of soybean hulls and wheat middlings. Diets were formulated on an equal standardized ileal digestible Lys:NE basis within phase, and RAC diets had increased amino acid concentrations compared with non-RAC diets. From d 0 to 84, control pigs had greater ( P P P P P P P P P

A pure form of salbutamol has the potential to deliver positive production benefits to the swine industry. The aim of this experiment was to determine the effects of salbutamol on growth, carcass measures, and health of finishing pigs. The study used 192 pigs (89 ± 1 kg BW) housed in groups of 6 in 32 pens and assigned to 1 of 4 treatments: 1) control (CTL), 0 mg/kg salbutamol; 2) 2R, control diet with 2 mg/kg of the pure R-enantiomer of salbutamol; 3) 4R, control diet with 4 mg/kg of pure R-salbutamol; or 4) 8RS, control diet with 8 mg/kg of a 50:50 mixture of the R- and S-enantiomers. All diets were offered ad libitum for 4 wk. All pigs were weighed and pen feed intakes were recorded weekly. At slaughter, individual HCW and measurements of the 10th-rib loin muscle area (LMA), color, marbling, firmness, and back fat, last lumbar, and midline back fat depths were collected. Data were analyzed using Proc GLM of SAS, with pen as the experimental unit. Overall, 2R and 4R pigs had greater ADG than CTL pigs (P < 0.05) and, at slaughter, were heavier than CTL pigs (P < 0.01). Overall, 8RS pigs had decreased ADFI (P < 0.05), and CTL pigs had poorer G:F (P < 0.001) than the other 3 treatments. All salbutamol-fed pigs had 5 to 6 kg greater HCW (P < 0.001), 2% to 3% increased carcass yield (P < 0.001), 5.6 cm(2) larger LMA (P < 0.01), 3 to 4 mm less 10th-rib back fat (P < 0.01), and 2 mm less lumbar back fat (P < 0.05) than CTL pigs. However, control pigs had greater loin muscle color scores (P < 0.05) and marbling scores (P < 0.001) than all salbutamol-treated pigs. Taken together, these data indicate that as little as 2 mg/kg R-salbutamol has a positive effect on pig growth and carcass composition. However, the effects of salbutamol on meat quality require further research.

Long distance transportation of weaned piglets (Sus scrofa) is increasingly common in the united states and may result in delayed eating, drinking, or normal social behaviors. A potential solution is a mid-journey rest (lairage). The objective of this study was to determine if a lairage altered behavior after a 16-h transport. Pigs that weighed approximately 18 kg each (n = 894) were housed in 16 pens with 8 pens per treatment. Lairaged pigs were transported for 8 h and given an 8-h rest with food and water, whereas control pigs were transported continuously for 16 h. The heaviest, the lightest, and 2 average-BW pigs relative to the average weight of the pen were observed by video recording for 24 h immediately before and after transport, and during d 6 and 13 after transport. Postures (lying, sitting, and standing) were recorded using 10-min-interval scan sampling, and behavioral categories included inactivity, activities (eating, drinking, alert, manipulating pen, rooting, and walking) and social interactions (aggression, belly nosing, playing, tail biting, and positive social behaviors). In both treatments, sitting occurred most before transport (P < 0.01) than at other times, but did not differ between treatments. Standing increased (time effect; P < 0.01) for both treatments immediately after transport through d 6, but returned to pre-transport values by d 13. In contrast, lying decreased (time effect; P < 0.01) after transport, but returned to above pre-transport values by d 13. Time effects were evident for activity (P < 0.01), pen manipulation (P = 0.05), rooting (P < 0.01), initiation of belly-nosing (P = 0.01), and receiving belly-nosing (P = 0.03); however, initiation of aggression did not differ for day (P = 0.19) or treatment (P = 0.56). Lairaged pigs initiated more (P = 0.05) play than continuously transported pigs, but no differences (P = 0.84) were seen in receipt of play behavior. Pigs that were to be transported for 16 h continuously walked less pre-transport, walked more post-transport (treatment × time interaction; P = 0.02), and drank less pre-transport, but drank more on all days post-transport compared with the lairage group (treatment × time interaction; P = 0.001). This study indicated that extended transport without lairage alters some swine behaviors relevant to production (water consumption) and demonstrated that a long-duration transport, regardless of the mid-journey lairage treatment, affects a number of behaviors up to 13 d after transportation.

The objective of this study was to evaluate the effects of water-delivered, direct-fed microbials (DFM) or organic acids on intestinal morphology and active nutrient absorption in weanling pigs after deliberate Salmonella infection. Pigs (n = 88) were weaned at 19 ± 2 d of age and assigned to 1 of the following treatments, which were administered for 14 d: 1) control diet; 2) control diet + DFM (Enterococcus faecium, Bacillus subtilis, and Bacillus licheniformis) in drinking water at 10(9) cfu/L for each strain of bacteria; 3) control diet + organic acid-based blend (predominantly propionic, acetic, and benzoic acids) in drinking water at 2.58 mL/L; and 4) control diet + 55 mg/kg carbadox. Pigs were challenged with 10(10) cfu Salmonella enterica var Typhimurium 6 d after commencement of treatments. Pigs (n = 22/d) were harvested before Salmonella challenge and on d 2, 4, and 8 after challenge. Duodenal, jejunal, and ileal mucosal tissues were sampled for measurement of villus height and crypt depth. Jejunal tissue was sampled for determination of active nutrient absorption in modified Ussing chambers. Duodenal villus height was greater in pigs fed in-feed antibiotic before infection (P < 0.05). Jejunal crypts were deeper in DFM- and acid-treated pigs on d 4 after infection compared with all other treatments (P < 0.05). Salmonella infection resulted in a linear decrease in phosphorus (P < 0.001) and glucose (P < 0.05) active transport, and an increase (P < 0.001) in glutamine uptake immediately after challenge. Salmonella infection reduced basal short-circuit current (I(sc)); however, water-delivered DFM or organic acid treatments caused greater basal I(sc) on d 2 after challenge than did carbadox. Carbachol-induced chloride ion secretion was greatest in negative control pigs before infection (P < 0.01) and DFM-treated pigs (P < 0.05) after infection. In conclusion, both the DFM and acidification treatments induced increases in basal active ion movement and jejunal crypt depth, which could be interpreted as responses consistent with increased Salmonella pathology, but none of the additives markedly affected intestinal absorptive and secretory function in response to Salmonella challenge.

The BW growth of 1,385 barrows and gilts was evaluated from d-21 weaning to 130 kg BW. The pigs were assigned to a 2×2 factorial arrangement of treatments. The pigs were fed a series of either standard corn- and soybean meal-based control diets or low nutrient excretion nutrient-dense (LNE-ND) diets from 1 wk postweaning to 130 kg BW and assigned to rooms with either deep pit or pull plug-recharge manure storage treatments. The pigs were weighed at weaning, at 7 and 14 d postweaning, and at approximately 2-wk intervals from 28 d postweaning to a mean BW of 130 kg. Mixed model nonlinear equations including pig-specific random effects were evaluated for the generalized Michaelis-Menten function. The serial postweaning BW data were fitted to a mixed model generalized Michaelis-Menten equation. Relationships of weaning BW to late finishing BW and days to 125 kg BW were different for each dietary treatment. Late finishing BW and days to 125 kg BW had nonlinear relationships with weaning BW for pigs fed the LNE-ND diets and had linear relationships for pigs fed the control diets. The predicted changes in subsequent BW of the LNE-ND diets per kilogram of change in weaning BW were greater for pigs with the lightest weaning BW than for pigs with average to above-average weaning BW. Across both dietary treatments, pigs with greater weaning BW and greater early postweaning ADG required fewer days to achieve target market BW.

Two experiments were conducted to de- termine the effects of feeding a corn- and soybean meal- based diet (control) or a low nutrient excretion (LNE) diet, formulated with reduced dietary CP and addi- tional synthetic AA, low phytic acid corn, and phytase, on pig growth performance during the grower (BW = 32 to 77 kg) and finisher (BW = 78 to 126 kg) periods and on carcass and bone characteristics at slaughter. Pigs (32 ± 1.3 kg of BW, Exp. 1; 6.7 ± 0.27 kg of BW, Exp. 2) were blocked by sex and BW and randomly allotted to a control or LNE diet. Pigs were housed in 4 rooms during the nursery period and in 2 rooms during the grower and finisher periods, with individual and identical ventilation systems. Pigs were phase fed 3 nursery diets for 5 wk (Exp. 2) and phase fed 2 grower and 2 finisher diets for 16 wk (Exp. 1 and 2). Pigs were housed 4 or 5 pigs/pen with 9 pens·sex −1 ·treatment −1 during the nursery period and 4 or 5 pigs/pen with 5 pens·sex −1 ·treatment −1 in the grower phase and 2 or 3 pigs/pen in the finisher phase. Individual BW and pen feed disappearance were recorded weekly in the nursery period and every 2 wk in the grower-finisher period. Pigs were scanned ultrasonically at d 34 of the nursery period and wk 8 and 16 of the grower-finisher period to determine backfat depths and LM area. Ten pigs·sex −1 ·treatment −1 were slaughtered at wk 16 of each experiment to determine carcass characteristics. Overall growth performance was not different during each ex- periment. However, nursery G:F (control = 0.65; LNE = 0.60), grower ADG (Exp. 1 and 2), and grower G:F (Exp. 2) were reduced (P < 0.05) when the LNE diets were fed. Diet had no effect on 10th-rib carcass data in either experiment. Metatarsal bone ash percentage was reduced (P < 0.05) when the LNE diets were con- sumed in both experiments. Feeding LNE diets resulted in the maintenance of overall growth performance, bone variables, and carcass characteristics. However, further refinements are still required in the nursery and grower phases of pig production to optimize LNE diet use by the swine industry.

Increasing concern for animal well-being and food safety has stimulated the investigation of feed additives such as ractopamine (RAC), a beta-agonist widely used to improve production performance of finishing pigs. The objective of this study was to determine effects of RAC feeding, delivered as a "step-up" program (5 mg/kg for 2 wk followed by 10 mg/kg for 2 wk), on growth performance, Enterobacteriaceae shedding, including Salmonella, and hoof lesions, also taking into account sex and social rank of pigs. A total of 64 barrows and gilts (balanced by treatment and sex) were assigned to pens of 4 (by sex) as either control (CTL) or RAC treatment. Social ranks (dominant, intermediate, and subordinate) of pigs in each pen were determined by behavioral observation during 48 h post-mixing. Fecal samples were collected once per week for 5 wk. At slaughter, the 32 dominant and subordinate barrows and gilts (16/sex) were examined for hoof lesions, and luminal contents from ileum, cecum, and rectum were collected. Pigs fed RAC had increased growth performance (P 0.10). No significant effect of RAC feeding was found on backfat or loin eye area (P > 0.10). At slaughter, RAC-fed pigs had greater BW (P < 0.05). Despite the positive effects of RAC feeding on growth performance, pigs fed the compound had a greater frequency of front and rear hoof lesions as did barrows and dominant individuals (P < 0.05). Detectable concentrations of Salmonella shedding were not identified at any time during the experiment. Enterobacteriaceae shedding concentrations from RAC-fed pigs peaked at the first week of feeding and progressively decreased until slaughter. At slaughter, rectal and cecal Enterobacteriaceae concentrations were less in RAC-fed pigs than in CTL pigs (P < 0.05). Social rank tended to affect gut Enterobacteriaceae populations of barrows more than in gilts (P < 0.10). The effects of RAC feeding on hoof soundness and Enterobacteriaceae populations in the gastrointestinal tract of finishing pigs warrant further investigation. It is also proposed that the integration of the social rank status of the individual into future studies should be considered, because it may affect treatment responses.

Weanling pigs ( n = 188) were used in a 5-wk experiment to determine the effects of a bolus of direct fed microbials (DFM) at weaning and/or feeding DFM on growth performance and gastrointestinal histology. Dietary treatments were: 1) basal negative control (NC), 2) Trt. 1 + DFM in a bolus at weaning, 3) Trt. 1 + DFM in the feed for d 1–34, 4) Trt. 1 + DFM in a bolus at weaning, and in the feed for d 1–34, and 5) Trt. 1 + in-feed antibiotics (carbadox, 55 ppm). Dietary antibiotics (Trt. 5) improved ADG ( P P P P P P P

Two ractopamine (RAC) step-up programs were evaluated for their economic returns using a swine growth simulation program that incorporated growth responses to constant and to increased RAC concentrations. Dietary lysine concentrations were optimized to maximize daily returns above feed costs for 3 phases: (1) before RAC supplementation, (2) the first half of the RAC feeding period (14 or 18 d), and (3) the second half of the RAC feeding period. Diets were assumed to be corn-soybean meal based diets. Two durations of RAC feeding were evaluated, 28 and 35 d. The model compared constant RAC concentrations (0, 5, or 10 ppm) and two step-up programs in which 5 ppm RAC was fed the first half of RAC feeding period followed by either 7.5 or 10 ppm RAC. The initial BW of pigs at the start of the second phase diet was set at 78 and 72 kg for the 28- and 35-d feeding durations, respectively. Two payment schemes were used: one set the lean-to-fat price ratio at 4:1, close to true carcass cut-out value, and the other set the lean-to-fat price ratio to 2:1, approximating carcass merit pricing systems. The 5 to 10 ppm step-up had the greatest daily returns, followed by the 5 to 7.5 ppm step-up, the constant RAC feeding, and the control. Step-up programs were predicted to be more profitable than feeding constant dietary RAC concentrations.

One hundred eighty pigs were used in a 15-wk experiment to determine the effects of supplementing pantothenic acid (PA) to the diet for 49 or 105 d prior to slaughter on growth performance and carcass characteristics. Pigs were blocked by sex and BW (initial = 29 kg) and were randomly assigned to pens (30 pens; six pigs per pen). Treatments included 1) control (13.2 ppm of PA), 2) control + 30 ppm of PA for 105 d preslaughter, and 3) control + 30 ppm of PA for 49 d preslaughter. Pig BW and pen feed intake were recorded biweekly. Ultrasonic estimates of 10th rib longissimus area (LEA) and fat thickness were recorded at 4-wk intervals on 3 pigs per pen. After 105 d, pigs were slaughtered, and individual hot carcass weights, American Ultrasound Services (AUS) backfat, and loin muscle depths (LMD) were recorded. Supplementation of PA did not affect (P> 0.10) overall ADG, ADFI, or feed efficiency. Tenth and last rib ultrasound thickness and LEA were not different (P> 0.10) between control-fed pigs and PA-supplemented pigs. Tenth rib carcass fat depths were numerically less for pigs fed diets with supplemental PA, but differences were not significant (P>0.10). Similarly, there was no effect of PA supplementation on carcass 10th rib LMD (P> 0.10). However, carcass lean percentage tended (P 13.2 ppm alters carcass composition.

Odor, ammonia (NH3) and hydrogen sulfide (H2S) concentrations, and emission rates were measured in two small rooms of finishing pigs with various manure removal strategies. The strategies included daily flush, and static pits with 7, 14, and 42 d manure accumulation cycles, with and without pit recharge with some secondary lagoon effluent after emptying. In each room, tests were conducted with three successive groups of 25 pigs, which were fed standard corn-soybean diets. Ammonia and H2S concentrations were measured automatically 15 to 24 times daily at various locations with chemiluminescence and pulsed fluorescence analyzers, respectively. Odor concentration, intensity, and hedonic tone of air samples were evaluated by a panel of eight trained subjects. Flushing and static pit recharge with lagoon effluent resulted in significantly less NH3, H2S, and odor emissions (P < 0.05). Draining static pits more frequently also significantly reduced H2S and odor emissions. Geometric mean odor emission rates were 19, 33, and 29 OUE s-1 AU-1 (OUE = European odor unit equivalent to 123 .g n-butanol, AU = 500 kg live mass) for the 1 d (daily flush), 7 d, and 14 d cycles without pit recharge, respectively, and 2.6 and 25 OUE s-1 AU-1 for the 7 d and 42 d cycles with pit recharge, respectively. Mean NH3 emission rates were 15, 27, and 25 g d-1 AU-1 for the 1, 7, and 14 d cycles without pit recharge, and 10, 12 and 11 g d-1 AU-1 for the 7, 14, and 42 d cycles with pit recharge, respectively. Mean H2S emission rates were 0.11, 0.27, and 0.41 g d-1 AU-1 for the 1, 7, and 14 d cycles without pit recharge, and 0.16, 0.34, and 1.42 g d-1 AU-1 for the 7, 14, and 42 d cycles with pit recharge, respectively. The mean H2S emission rate during daily flushing was 0.40 g d-1 AU-1 when flushing-induced burst emissions were included in the means, as compared with 0.11 g d-1 AU-1 when flushing times were excluded. Sudden emissions during flushing events had a significant influence on mean emissions from these relatively small rooms; however, without valid data from week 1, the mean H2S emission rate of 0.40 g d-1 AU-1 was probably an overestimate. Daily flushing reduced odor emissions by 41% and 34% (P < 0.05) as compared with the 7 d and 14 d cycles, respectively. The 7 d cycle resulted in 35% and 53% lower H2S emissions as compared with the 14 d cycle with and without pit recharge, respectively. The 14 d cycle had 76% less (P < 0.05) H2S emission than the 42 d cycle, both cycles with pit recharge. Mean daily NH3 emissions from the rooms with static pits were 51% to 62% lower (P < 0.05) with recharge than without recharge. Similarly, mean daily H2S emissions were 18% to 40% lower with pit recharge. In summary, lower NH3 and H2S emissions occurred when pits were recharged after emptying, and when pits were emptied more frequently.

Two experiments were conducted to evaluate the effects of adding fiber sources to reduced-crude protein (CP), amino acid-supplemented diets on N excretion, growth performance, and carcass traits of growing-finishing pigs. In Exp. 1, six sets of four littermate barrows (initial weight = 36.3 kg) were allotted randomly to four dietary treatments to determine N balance and slurry composition. Dietary treatments were: 1) fortified corn-soybean meal, control, 2) as fortified corn-soybean meal with CP lowered by 4 percentage units and supplemented with lysine, threonine, methionine, tryptophan, isoleucine, and valine (LPAA), 3) same as Diet 2 plus 10% soybean hulls, and 4) same as Diet 2 with 10% dried beet pulp. Nitrogen intake, absorption, and retention (g/d) were reduced (P 0.10) by addition of fiber sources to the LPAA diet. However, N absorption, as a percentage of intake, was not affected (P > 0.10) by dietary treatment. Nitrogen retention, expressed as a percentage of N intake, was increased (P 0.10) by fiber addition. However, fiber addition to the LPAA diet tended to result in a greater proportion of N excreted in the feces than in the urine. Slurry pH, ammonium N content, and urinary urea N excretion were reduced (P 0.10) by dietary treatment. These data suggest that reducing CP with amino acid supplementation markedly decreased N excretion without influencing growth performance. Fiber addition to a LPAA diet had little effect on overall N balance or growth performance, but tended to further reduce slurry ammonium N concentration and increase volatile fatty acid concentrations.

Carcass and live measurements of 45 barrows were used to evaluate the magnitude of ractopamine (RAC) treatment prediction biases for measures of carcass composition. Barrows (body weight = 69.6 kg) were allotted by weight to three dietary treatments and fed to an average body weight of 114 kg. Treatments were: 1) 16% crude protein, 0.82% lysine control diet (CON); 2) control diet + 20 ppm RAC (RAC16); 3) a phase feeding sequence with 20 ppm RAC (RAC-P) consisting of 18% crude protein (1.08%. lysine) during wk 1 and 4, 20% crude protein (1.22% lysine) during wk 2 and 3, 16% crude protein (0.94% lysine) during wk 6, and 16% crude protein (0.82% lysine) during wk 6. The four lean cuts from the right side of the carcasses (n = 15/treatment) were dissected into lean and fat tissue. The other cut soft tissue was collected from the jowl, ribs, and belly. Proximate analyses were completed on these three tissue pools and a sample of fat tissue from the other cut soft tissue. Prediction equations were developed for each of five measures of carcass composition: fat-free lean, lipid-free soft tissue, dissected lean in the four lean cuts, total carcass fat tissue, and soft-tissue lipid mass. Ractopamine treatment biases were found for equations in which midline backfat, ribbed carcass, and live ultrasonic measures were used as single technology sets of measurements. Prediction equations from live or carcass measurements underpredicted the lean mass of the RAC-P pigs and underpredicted the lean mass of the CON pigs. Only 20 to 50% of the true difference in fat-free lean mass or lipid-free soft-tissue mass between the control pigs and pigs fed RAC was predicted from equations including standard carcass measurements. The soft-tissue lipid and total carcass fat mass of RAC-P pigs was overpredicted from the carcass and live ultrasound measurements. Prediction equations including standard carcass measurements with dissected ham lean alone or with dissected loin lean reduced the residual standard deviation and magnitude of biases for the three measures of carcass lean mass. Prediction equations including the percentage of lipid of the other cut soft tissue improved residual standard deviation and reduced the magnitude of biases for total carcass fat mass and soft-tissue lipid. Prediction equations for easily obtained carcass or live ultrasound measures will only partially predict the true effect of RAC to increase carcass leanness. Accurate prediction of the carcass composition of RAC-fed pigs requires some partial dissection, chemical analysis, or alternative technologies.

Several research trials have evaluated the impact of ractopamine on barrows and gilts of vari- ousgeneticpopulations. Overall,thedesirableresponse of ractopamine to increase daily carcass lean gain, im- prove feed efficiency, and increase carcass lean percent- age has been observed in genetic populations of sub- stantially different lean growth rates and carcass lean percentages. Six trials have evaluated the magnitude of genetic populations × ractopamine interactions. In one trial, carcass muscle accretion (g/d) increased with ractopamine to a greater extent in high-lean-gain (High-Lean) barrows than in low-lean-gain (Low-Lean) barrows (P < 0.02). Dissected fat accretion (g/d) was reduced by a greater magnitude in the High-Lean than in the Low-Lean barrows (P < 0.04). A second trial evaluated the ractopamine response in five genetic pop- ulations of barrows and found significant ractopamine × genetic populations interactions (P < 0.05) for daily carcass lean gain. Regression of the carcass lean gain of pigs fed ractopamine on the mean carcass lean gain

Daily feed intakes (DFI) of 565 lactation records were evaluated for sows of 2 genetic lines, PIC C-22 and L-42. Sows were fed ad libitum during the entire 21-d lactation period with a diet supplemented with either 0 or 0.3% betaine-HCl. Sows were fed corn–soybean based diets (3.32 Mcal of ME/kg).

Managing stressors is essential for optimizing pig growth performance. To determine the effects of temperature and space allocation on growth performance and carcass characteristics, pigs were housed within their thermoneutral zone, at 23.9 degrees C, or above their thermoneutral zone, at 32.2 degrees C, and were provided either 0.66 or 0.93 m(2)/pig for the final 35 d of the grow-finish period. Individual BW were recorded on d 1, 10, 20, and 30. At slaughter, carcass measurements and samples of backfat and belly fat were collected. Final BW was decreased (P < or = 0.05) from 113 to 103 kg for pigs housed at 32.2 degrees C. The ADG was reduced (P < 0.05) for pigs housed at 32.2 degrees C (0.89 vs. 0.54 kg/d), as was G:F (0.28 vs. 0.24). Housing at 0.66 m(2)/pig resulted in pigs that were lighter (P < or = 0.05), at 106 compared with 110 kg, as a result of decreased (P < or = 0.05) ADG (0.78 to 0.65 kg/d) and decreased (P < or = 0.05) G:F (0.275 to 0.255) compared with pigs housed at 0.93 m(2)/pig. Pigs housed at a greater spatial allocation had elevated (P < or = 0.05) ADFI. The interaction of housing at 32.2 degrees C and decreasing spatial allocation increased (P < or = 0.05) the adipose iodine value from 66.8 to 70.4, decreased (P < or = 0.05) the saturated:unsaturated fatty acids ratio from 0.59 to 0.56, and increased (P < or = 0.05) the n-6:n-3 from 23.56 to 25.27. Decreased spatial allocation resulted in decreased (P < or = 0.05) belly weights. Although increased temperature did not affect belly weight, the 32.2 degrees C pigs had decreased (P < or = 0.05) raw and cooked slice weights, increased (P < or = 0.05) percentage lean of bacon, increased (P < or = 0.05) lean:fat ratio of bacon slices, increased (P < or = 0.05) raw slice scores, and increased (P < or = 0.05) quantity of collagen in belly fat. Some of these changes may have resulted from changes in lipid metabolism. Increasing spatial allocation in the 32.2 degrees C pigs decreased fatty acid synthase (P = 0.03) and stearoyl-CoA desaturase- 1 (P = 0.08) mRNA expression in adipose tissue. The results from this study demonstrated decreased growth, carcass lipid quality, and bacon quality in pigs housed at temperatures above the thermoneutral zone; however, increasing the spatial allocation for housing may be a means to ameliorate the negative effects of temperature stress.