Effects of floor area allowance and group size on the productivity of growing/finishing pigs

The impact of floor space allowance and dietary energy level on finishing pigs, from 65 to 120 kg, on growth performance

The objective of this experiment was to evaluate the impact of lowering floor space allowance in finishing hogs from 65 to 120 kg when fed high- vs. low-energy diets on growth performance. Eighty-eight mixed-sex pens with 24 ± 1 pigs per pen were randomly assigned by weight in a complete block design to one of eight treatments in a 2 × 4 factorial arrangement with two energy levels: low (LE, 3267 ± 15 kcal/kg) vs. high (HE, 3389 ± 15 kcal/kg) accomplished through fat inclusion; and four floor space allowances: 0.6, 0.63, 0.65, and 0.67 m²/pig. Assigned floor space was accomplished by moveable gates in the rear of the pen which were adjusted at each pig removal until the marketing phase. Pen weight was measured at days 0, 29, and 48, with feed disappearance measured at days 29 and 48 to calculate average daily gain (ADG), average daily feed intake (ADFI), and gain-to-feed ratio (GF). Data were analyzed by pen (SAS 9.4, Cary, NC), as repeated measures, with the fixed effects of floor space allowance, dietary energy level, and the interaction between floor space allowance and energy level. For the overall experiment, decreased floor space had no effect (P > 0.1) on ADG, ADFI, or GF. Energy had a significant effect (P < 0.01) on ADFI (3.17 vs. 3.12 kg for LE and HE, respectively) and GF (0.35 and 0.36 for LE and HE, respectively), and tended to impact (P = 0.08) ADG (1.12 vs. 1.13 kg, for LE and HE, respectively). In conclusion, reducing space allowance from 0.67 m² down to 0.6 m² did not affect the growth performance of pigs from 65 to 120 kg. Pigs fed LE consumed more than the HE diets but had generally similar growth and no difference in body weight.

Dietary energy level, feeder space, and group size on growth performance and carcass characteristics of growing-finishing barrows and gilts

To benefit from feeding low net energy (NE) diets, growing-finishing pigs must be able to increase feed intake to compensate for lower caloric density, but this might be difficult in pens with a high stocking density. Access to the feeder, trough space, and(or) floor area may limit voluntary feed intake. The objective of this study was to clarify the relationships among dietary NE level, feeder space, group size, sex, and interactions in growing-finishing pigs. In a 2 × 2 × 2 × 2 factorial design, 1,920 pigs (33 kg) housed in 96 fully slatted floor pens (6.1 × 2.4 m) with 2 or 3 feeder spaces, and 18 or 22 barrows or gilts per pen, were fed either low (9.2 MJ/kg) or high (9.85 MJ/kg) NE diets over 5 growth phases (Grower 1: day [d] 0 to 20, Grower 2: d 21 to 41, Grower 3: d 42 to 62, Finisher 1: d 63 to 80, Finisher 2: d 81 to slaughter). Pen body weight (BW) and average daily feed disappearance (ADFD) were measured for each growth phase, biweekly from the start of shipping and at slaughter. Warm carcasses were weighed and graded (Destron). For the entire trial, pigs fed low versus (vs.) high NE diets had 0.119 kg/d greater (P < 0.001) ADFD, but 0.556 MJ/d lower (P < 0.050) average daily caloric disappearance (ADCD), and 0.017 kg/kg lower (P < 0.001) gain-to-feed (G:F). Pens with 18 vs. 22 pigs had 0.062 kg/d greater (P < 0.001) ADFD, 0.730 MJ/d greater (P < 0.010) ADCD, and 0.029 kg/d greater (P < 0.001) average daily weight gain (ADWG). Pigs in pens with 3 vs. 2 feeding spaces had 0.051 kg/d greater (P < 0.010) ADFD, 0.511 MJ/d greater (P = 0.050) ADCD but 0.004 kg/kg lower (P < 0.050) G:F. Pigs fed low vs. high NE diets had 0.6 kg lower (P < 0.050) carcass weight and 0.9 mm lower (P < 0.050) loin depth. Pens with 18 vs. 22 pigs took 2.8 days less (P < 0.001) to reach 130 kg slaughter BW. Pens with 18 vs. 22 pigs had a 0.4 %-point decrease (P < 0.050) in dressing percentage. Feeding low vs. high NE diets reduced (P < 0.001) feed cost by Can$21.87/tonne, $3.34/pig, $0.03/kg gain, and increased (P < 0.05) gross income subtracting feed cost by $1.82/pig. Housing 18 vs. 22 pigs per pen increased (P < 0.010) ISFC by $1.98 per pig. Lack of interactions between NE level, feeder space, and group size for ADFD indicate that low NE diets can be fed to pigs even if they have lower than recommended floor area allowance during part of the finishing phase.

Effects of stocking density on growth performance, blood parameters and immunity of growing pigs

This study was conducted to evaluate the effects of different stocking densities on growth performance, blood parameters, intestinal morphology and intestinal immunity of growing pigs. A total of 288 male pigs (44.35 ± 0.50 kg) were randomly assigned to groups with stocking densities of 2.46, 1.23 and 0.82 m²/pig for a month. The results showed that there was no significant difference on growth performance among groups. Pigs in the stocking density of 0.82 m²/pig had the lowest backfat thickness and spleen weight index among groups (P < 0.05). With increasing stocking density, the serum concentrations of blood urea nitrogen (BUN), transglutaminase (TGG), alkaline phosphatase (AKP) and immunoglobulin A (IgA) were increased, and albumin (ALB), albumin-to-globulin ratio (ALB:GLO), insulin-like growth factor-1 (IGF-1) and immunoglobulin (IgM) were decreased (P < 0.05), and cortisol tended to increase and glucose tended to decrease (0.05 < P < 0.1). Compared with the stocking density of 2.46 m²/pig, the ileal villus height and jejunal villus width decreased in stocking densities of 1.23 and 0.82 m²/pig (P < 0.05). The duodenal villus height and ileal villus width in the stocking density of 0.82 m²/pig were the lowest among 3 groups (P < 0.05). The content of immunoglobulin A in duodenum, jejunum and ileum mucosa increased along with increasing density (P < 0.05). The contents of interleukin (IL)-2 in the spleen or liver and IL-10 in the spleen were higher in the stocking density of 0.82 m²/pig than in other 2 groups. These results showed that stocking density could affect the metabolism, intestinal morphology, and immunity of growing pigs and 1.23 m²/pig may be the suitable stocking density for the growing pigs in the present study.

Effects of space allowance and marketing strategy on growth performance of pigs raised to 165 kg

A total of 976 pigs (PIC 327 × Camborough; PIC, Hendersonville, TN; initially 22.0 ± 1.53 kg body weight [BW]) were used in a 160-d growth study to evaluate the effects of increasing space allowance and varying marketing strategies on growth performance of pigs raised to market weights of ~165 kg. Pens of pigs were blocked by location within the barn and allotted to one of six treatments. Pen served as the experimental unit, and there were eight replicate pens per treatment. The first four treatments consisted of increased initial stocking density and did not utilize topping strategies: (1) 14 pigs/pen (1.17 m²/pig), (2) 17 pigs/pen (0.97 m²/pig), (3) 20 pigs/pen (0.82 m²/pig), and (4) 23 pigs/pen (0.71 m²/pig). The fifth treatment began with 25 pigs/pen (0.66 m²/pig) and had four marketing events with the heaviest 3 pigs/pen removed on day 93, and additional pigs removed to a common inventory of 20 pigs/pen on day 122 and 17 pigs/pen on day 147 with final marketing on day 160. The final treatment began the experiment with 23 pigs/pen (0.71 m²/pig) with three marketing events to achieve a common inventory of 20 pigs/pen on day 108 and 17 pigs/pen on day 147. Pens of pigs were weighed and feed disappearance measured on days 0, 55, 93, 108, 122, 135, 147, and 160. As space allowance decreased from 1.17 to 0.71 m²/pig via increased initial pen inventory (treatments 1 to 4), overall average daily gain (ADG) and average daily feed intake (ADFI) decreased (linear, P < 0.001), while gain:feed ratio (G:F) did not differ (P > 0.05). The treatments with multiple marketing events were compared with each other and with the treatment that began with 0.71 m²/pig and only marketed once at the end of the study. Overall ADG and ADFI were not different (P > 0.05) among these three treatments. Marketing pigs three or four times improved (P < 0.05) G:F compared with the treatment that began the study with 0.71 m²/pig and marketed only once. Reducing floor space allowance for heavy weight pigs decreased intake, which resulted in lower growth rate and final BW, with these reductions occurring before the critical k-value was reached. Total weight gain per pen was maximized with the lowest space allowance and the multiple marketing treatments. Thus, strategic use of pig removals prior to final marketing may allow producers to maximize both number of pigs and total weight marketed through a barn when feeding to heavy weights.

Effects of Farrowing Stall Layout and Number of Heat Lamps on Sow and Piglet Production Performance

Simple Summary

In the commercial swine industry, farrowing stalls are commonly used as a strategy to reduce piglet pre-weaning mortalities caused by sow over-lay. Farrowing stall dimensions have generally remained the same over the past 50 years in the United States, even though the sizes of both the sows and litters have increased considerably. This extensive field study investigated if sow and piglet productivity would be affected when housed in stalls of traditional layout, additional area for the piglets, or additional area for the sow. All three layouts were also tested with use of one or two supplementary heat lamps in the creep area. Results show that stall layout and number of heat lamps had no statistical impact on production outcomes. However, seasonal differences, sow parity, and number of litter mates did have significant effects. Providing larger stalls or an additional heat lamp costs more for the producer but did not yield production improvements.

Abstract

Most farrowing facilities in the United States use stalls and heat lamps to improve sow and piglet productivity. This study investigated these factors by comparing production outcomes for three different farrowing stall layouts (traditional, expanded creep area, expanded sow area) and use of one or two heat lamps. Data were collected on 427 sows and their litters over one year. Results showed no statistical differences due to experimental treatment for any of the production metrics recorded, excluding percent stillborn. Parity one sows had fewer piglets born alive (p < 0.001), lower percent mortality (p = 0.001) and over-lay (p = 0.003), and a greater number of piglets weaned (p < 0.001) with lower average daily weight gain (ADG) (p < 0.001) and more uniform litters (p = 0.001) as compared to higher parity sows. Farrowing turn, associated with group/seasonal changes, had a significant impact on most of the production metrics measured. Number of piglets born influenced the percent stillborn (p < 0.001). Adjusted litter size had a significant impact on percent mortality (p < 0.001), percent over-lay (p < 0.001), and number of piglets weaned (p < 0.001). As the number of piglets weaned per litter increased, both piglet ADG and litter uniformity decreased (p < 0.001). This information can be used to guide producers in farrowing facility design.

The effect of Piétrain sire on the performance of the progeny of two commercial dam breeds: a pig intervention study

Genetic evaluation of Piétrain sires in Flanders occurs under standardized conditions, on test stations with fixed dam breeds, standardized diets and uniform management practices. As environmental conditions vary on commercial farms and differ from the test stations, this study aimed at understanding to what extent the sire, the dam breed and the interaction between both affects the translation of breeding values to practice. Dams of two commercial breeds were inseminated with semen from one of five different sires selected for contrasting breeding values (daily gain, feed conversion ratio and carcass quality). For each sire by dam breed combination, six pen replicates (with three gilts and three barrows per pen) were evaluated for growth performance from 9 weeks of age (20 kg) to slaughter (110 kg), and for carcass and meat quality. In our experimental setup, both sire and dam breed affected growth, carcass and meat quality traits. No significant sire×dam breed interactions on performance could be detected. Though a tendency for interaction on average daily feed intake between 20 and 110 kg (P=0.087), and on pork colour (lightness) (P=0.093) was present. In general, offspring of all tested sires behaved similarly in both dam breeds, indicating that estimated breeding values for Piétrain sires determined in one dam breed are representative in other dam breeds as well.

Effects of increased space allowance on animal welfare, meat and ham quality of heavy pigs slaughtered at 160Kg

Sixty barrows (Body Weight–BW- range: 23.9–160 kg) were allotted to two experimental groups (6 pens of 5 pigs each): the control group was kept at a space allowance of 1m²/head; the second group was kept at 1.3m²/head. Behaviour, growth parameters, carcass and meat quality were assessed, as well as fat and cured ham quality. Results showed that pigs raised at 1.3m²/head spent more time laying (particularly in lateral recumbency, P<0.01 and P<0.001, respectively) compared to pigs kept at lower space allowance. They also reduced the aimless exploration of the slatted pen floor (P<0.001) and increased overall expression of other, mainly active, behaviors (e.g., drinking, walking and standing, P<0.01). Pigs raised at 1.3m^2/head showed higher final BW (P = 0.02), more favourable Average Daily Gain (ADG) and gain-to-Feed ratio (G:F) both during the last period of the trial (P<0.05 for both parameters) and over the entire trial (P = 0.01 for both parameters). No significant difference was observed between groups for carcass traits and the main meat quality attributes. Subcutaneous fat from green hams had higher α-linolenic acid content (P<0.01) in the group reared at greater space allowance. Green hams from this group lost less weight at trimming (P<0.01) and the resulting cured hams received better sensory evaluations (P<0.05). No difference was observed in fatty acid composition and unsaturation levels of the subcutaneous fat from cured hams. Our data suggest that heavy pigs intended for Parma ham would benefit from the adoption of higher individual floor space allowances, both in terms of animal welfare (increased possibility to rest) and of productive parameters, without having any detrimental effect on the suitability of the thighs for dry-curing or on the quality of the final product.

Effects of wet/dry feeder and pen stocking density on grow-finish pig performance

Three thousand one hundred and eighty-two terminal cross pigs (barrows and gilts) PIC line 359 sires × 1,050 dams were used from three consecutive grow-finish groups (initial BW of 21.51 ± 0.42 kg, 31.61 ± 1.18 kg, 29.41 ± 0.28 kg for replicates 1-3). Pigs were randomly assigned to each pen at the start of the trial and the research period continued for 106, 94, and 100 d for the first, second, and third replicates, respectively. The experimental treatments were designed as a two by three factorial (pen space of 0.65 or 0.78 m²/pig with 10, 13, or 16 pigs per feeder space), each pen had an equal number of barrows and gilts with 20, 26, and 32 pigs per pen for the 10, 13, and 16 pigs per feeder space pens. Each pen was equipped with one double-sided wet/dry feeder, 37.5 cm wide, with one nipple drinker. All pigs had ad libitum access to feed and water supply during the trial period. Pigs for all the three replicates were fed with the same series of diets. Pigs were weighed by pen at the start of trial and at the end of the trial to calculate ADG. Feed was removed from the feeders and weighed to determine ADFI and G:F. To express floor space allowance, the k value was estimated by the equation: space per pig   ( m 2 ) = k × BW  ( kg ) 0.67 . No interactions (P > 0.05) of floor space allowance with pigs per feeder were observed. Pigs with less floor space allowance had reduced BW (128.8 vs. 129.5 kg, P = 0.026), ADG (1.00 vs. 1.02 kg/d, P = 0.002), and ADFI (2.52 vs. 2.61 kg/d, P < 0.001). However, G:F was improved (0.402 vs. 0.397, P = 0.039) with less floor space allowance per pig. Increased pigs per feeder space reduced final BW (129.7, 129.4, 128.4 kg, linear; P = 0.001). However, ADG had a quadratic relationship (P = 0.005) with pigs per feeder space with means of 1.03, 1.01, and 1.01 kg/d for 10, 13, and 16 pigs per feeder space. Overall, ADFI had a quadratic relationship (P < 0.0001) with number of pigs per feeder space with means of 2.62, 2.52, and 2.55 kg/d for 10, 13, and 16 pigs per feeder space. Gain efficiency had a quadratic relationship (P = 0.005) with number of pigs per feeder space with means of 0.395, 0.404, and 0.400 for 10, 13, and 16 pigs per feeder space. In conclusion, a floor space allowance of 0.65 m²/pig in the grow-finish period reduced ADFI and ADG compared with 0.78 m²/pig. Overall, with the type of wet/dry feeder used in this study, 10 pigs per feeder had the greatest ADG and ADFI, compared with 13 or 16 pigs per feeder space. However, G:F improved as the number of pigs per feeder space increased.

Effect of floor space allowances on growth performance of finishing pigs marketed at 138 kilograms

Current floor space allowances were determined in research studies conducted 10 to 20 yr ago using pigs that were marketed at a BW of about 113 kg or less. Currently, pork producers are regularly marketing pigs that weigh over 128 kg. Given this precipitous increase in market weight, we conducted 2 experiments to determine if floor space allowances previously determined apply to pigs marketed at greater than 128 kg. Experiment 1 was conducted at 5 university research stations throughout the Upper Midwest region. In this experiment, we evaluated the growth performance, salivary cortisol concentrations, and lesion scores of pigs weighing between 27 and 138 kg provided 0.71, 0.80, 0.89, 0.98, or 1.07 m/pig of floor space. Within each station, group size (range = 6 to 19 pigs) remained constant across floor space treatments but pen size was altered to achieve the desired space allocations. There were 14 replicate pens for each treatment. Overall, increasing floor space allowance increased final BW (linear, = 0.04) and tended (linear, < 0.06) to increase ADG and ADFI. There were no improvements in final BW or ADG beyond 0.89 m/pig. The G:F was not influenced by increasing floor space allocation. Salivary cortisol concentrations and lesion scores were not affected by floor space allowances. Experiment 2 focused on floor space needs of pigs nearing market weight and was conducted at 4 research stations. Pigs weighing about 130 kg were assigned to pens that provided 0.71, 0.80, 0.89, 0.98, or 1.07 m/pig of floor space. Group size ranged from 4 to 11 pigs per pen but was constant across floor space treatments within station. The study lasted 2 wk and there were 8 replicate pens per treatment. As floor space allowance increased, ADG (0.86, 0.95, 0.95, 1.10, and 1.06 kg; linear, < 0.01), ADFI (3.03, 3.26, 3.22, 3.49, and 3.25 kg; quadratic, < 0.05), and final BW (145.6, 145.7, 146.4, 148.3, and 147.9 kg; linear, < 0.01) increased. Based on the results of these 2 experiments, pigs marketed at about 138 kg require at least 0.89 m/pig to support optimal growth performance. However, heavier pigs (about 148 kg) at the end of the finishing period require 0.98 m/pig.

Development of equations to predict the influence of floor space on average daily gain, average daily feed intake and gain : feed ratio of finishing pigs

Floor space allowance for pigs has substantial effects on pig growth and welfare. Data from 30 papers examining the influence of floor space allowance on the growth of finishing pigs was used in a meta-analysis to develop alternative prediction equations for average daily gain (ADG), average daily feed intake (ADFI) and gain : feed ratio (G : F). Treatment means were compiled in a database that contained 30 papers for ADG and 28 papers for ADFI and G : F. The predictor variables evaluated were floor space (m2/pig), k (floor space/final BW0.67), Initial BW, Final BW, feed space (pigs per feeder hole), water space (pigs per waterer), group size (pigs per pen), gender, floor type and study length (d). Multivariable general linear mixed model regression equations were used. Floor space treatments within each experiment were the observational and experimental unit. The optimum equations to predict ADG, ADFI and G : F were: ADG, g=337.57+(16 468×k)-(237 350×k 2)-(3.1209×initial BW (kg))+(2.569×final BW (kg))+(71.6918×k×initial BW (kg)); ADFI, g=833.41+(24 785×k)-(388 998×k 2)-(3.0027×initial BW (kg))+(11.246×final BW (kg))+(187.61×k×initial BW (kg)); G : F=predicted ADG/predicted ADFI. Overall, the meta-analysis indicates that BW is an important predictor of ADG and ADFI even after computing the constant coefficient k, which utilizes final BW in its calculation. This suggests including initial and final BW improves the prediction over using k as a predictor alone. In addition, the analysis also indicated that G : F of finishing pigs is influenced by floor space allowance, whereas individual studies have concluded variable results.

Effects of space allocation on finishing pig growth performance and carcass characteristics

A total of 405 pigs (PIC 327 × 1,050) were used in 2 experiments (Exp. 1, initially 66.1 ± 1.8 kg BW, Exp. 2 initially 60.8 ± 2.5 kg BW) to examine the effects of space allocation on finishing pig growth performance and carcass characteristics. Pigs were randomly allotted to pens on entry into the finishing facility. Pens of pigs were balanced by initial BW and randomly allotted to 1 of 3 treatments with either 7 or 8 replications per treatment (Exp.1 and 2, respectively). There were 9 pigs per pen and gates were adjusted to provide 0.84, 0.74, or 0.65 m² per pig. Each pen was equipped with a dry single-sided feeder with two 35.6 cm × 11.4 cm (length × width) feeder spaces and a cup waterer. In both experiments, as space allocation decreased, overall ADG and ADFI decreased (linear, P < 0.019) with no evidence for differences in G:F. In Exp. 2, there was marginal evidence for a linear improvement (P = 0.061) in G:F as space allocation decreased from d 42 to 56. Final BW was 3.8 and 5.3 kg greater (linear, P ≤ 0.005) in Exp. 1 and 2, respectively, when comparing the 0.65 to the 0.84 m² per pig space allocation treatments. Using a predicted k-value of 0.0336, ADFI and, subsequently, ADG should have begun to decrease when pigs reached 121.2, 101.7, and 83.3 kg at 0.84, 0.74, or 0.65 m² per pig, respectively. In Exp. 1, we found marginal evidence for a reduction in ADFI as space allocation decreased starting at a mean BW of 80.3 kg (d 14; linear, P = 0.072). In Exp. 2, ADFI and consequently ADG decreased linearly (P < 0.029) starting at a mean BW of 74 kg, as space allocation decreased, before pigs reached the k-value that should have influenced performance. It is unknown if growth performance was impacted for the 0.84 m² treatment group as this was the greatest space allocation treatment. Overall, these studies indicate that decreasing space allocation resulted in poorer ADG driven by a reduction in ADFI. The data suggests that the accepted k-value of 0.0336 might underestimate the impact of space restriction on finishing pig ADG and ADFI.

Effects of space allocations and energy levels on growth performance and nutrient digestibility in growing and finishing pigs

Two experiments were conducted to investigate effects of different space allocations and different dietary metabolizable energy (ME) levels on growth performance and nutrient digestibility in growing and finishing pigs. In experiment 1, a total of 84 growing pigs [(Yorkshire × Landrace) × Duroc] with an initial body weight (BW) of 27.10 ± 1.60 kg were used in a 5-week trial. Pigs were blocked based on initial BW into a 2 × 2 factorial design with the following factors: (i) 0.60 or 0.80 m² /pig space allocations; and (ii) 3,400 or 3,550 kcal/kg ME of diets. In experiment 2, a total of 84 finishing pigs with an initial BW of 67.43 ± 1.97 kg were used in a 10-week trial. Pigs were allotted based on initial BW into a 2 × 2 factorial design with the following factors: (i) 0.81 or 1.08 m² /pig space allocations; and (ii) 3,300 or 3,450 kcal/kg ME of diet. In experiment 1, high ME diet improved gain-to-feed ratio (G:F) in pigs with low space allocation but not in pigs in high space allocation (p < .05). Additionally, high ME diet increased apparent total tract digestibility (ATTD) of nitrogen in low space allocation but decreased ATTD of nitrogen in high space allocation (p < .05). In experiment 2, high ME diet improved average daily gain (ADG) and G:F in early-finishing pigs with low space allocation but not in pigs with high space allocation (p < .05). In conclusion, the provision of high ME diets was not enough to overcome the reduction in growth performance due to low space allocation but can improve feed efficiency in growing pigs and daily gain and feed efficiency early-finishing pigs.

The effect of stocking density and social regrouping stressors on growth performance, carcass characteristics, nutrient digestibility and physiological stress responses in pigs

A 2 ✕ 2 factorial arrangement of treatments used 280 growing pigs and 240 finishing pigs to examine the main effects and interactions between two levels of stocking density (0·75 m2 v. 0·45 m2 per growing pig and 0·88 m2 v. 0·53 m2 per finishing pig) and grouping (static groups v. regrouped) on pig growth performance, carcass characteristics, nutrient digestibility and measurements of physiological indicators of stress responses. Regrouping was achieved by moving four unfamiliar pigs between replicate groups every 14 days. Average daily gain (ADG) and average daily food intake (ADFI) were reduced by an additive interaction between high density and regrouping in growing pigs (P < 0·01). In finishing pigs, regrouping reduced ADG (P 0·05) and carcass weight (P 0·05). Regrouping reduced apparent dry matter and gross energy digestibility in finishing pigs (P 0·05). Rectal temperature increased 3 h after mixing finishing pigs (P 0·05), but not growing pigs. In growing pigs, the neutrophil: lymphocyte ratio tended to increase (P 0·1) after regrouping, although plasma cortisol concentration was unaffected. In finishing pigs, the response to a Newcastle disease virus antigen challenge tended to decrease at high stocking density (P 0·1), although total IgG concentration was unaffected. In conclusion, the growth performance of growing and finishing pigs was affected by social stressors. However, effects on the physiological measurements did not concur with effects on growth performance.

Why are most EU pigs tail docked? Economic and ethical analysis of four pig housing and management scenarios in the light of EU legislation and animal welfare outcomes

To limit tail biting incidence, most pig producers in Europe tail dock their piglets. This is despite EU Council Directive 2008/120/EC banning routine tail docking and allowing it only as a last resort. The paper aims to understand what it takes to fulfil the intentions of the Directive by examining economic results of four management and housing scenarios, and by discussing their consequences for animal welfare in the light of legal and ethical considerations. The four scenarios compared are: 'Standard Docked', a conventional housing scenario with tail docking meeting the recommendations for Danish production (0.7 m2/pig); 'Standard Undocked', which is the same as 'Standard Docked' but with no tail docking, 'Efficient Undocked' and 'Enhanced Undocked', which have increased solid floor area (0.9 and 1.0 m2/pig, respectively) provision of loose manipulable materials (100 and 200 g/straw per pig per day) and no tail docking. A decision tree model based on data from Danish and Finnish pig production suggests that Standard Docked provides the highest economic gross margin with the least tail biting. Given our assumptions, Enhanced Undocked is the least economic, although Efficient Undocked is better economically and both result in a lower incidence of tail biting than Standard Undocked but higher than Standard Docked. For a pig, being bitten is worse for welfare (repeated pain, risk of infections) than being docked, but to compare welfare consequences at a farm level means considering the number of affected pigs. Because of the high levels of biting in Standard Undocked, it has on average inferior welfare to Standard Docked, whereas the comparison of Standard Docked and Enhanced (or Efficient) Undocked is more difficult. In Enhanced (or Efficient) Undocked, more pigs than in Standard Docked suffer from being tail bitten, whereas all the pigs avoid the acute pain of docking endured by the pigs in Standard Docked. We illustrate and discuss this ethical balance using numbers derived from the above-mentioned data. We discuss our results in the light of the EU Directive and its adoption and enforcement by Member States. Widespread use of tail docking seems to be accepted, mainly because the alternative steps that producers are required to take before resorting to it are not specified in detail. By tail docking, producers are acting in their own best interests. We suggest that for the practice of tail docking to be terminated in a way that benefits animal welfare, changes in the way pigs are housed and managed may first be required.

Effect of Floor Space Allowance on Pig Productivity across Stages of Growth: A Field-scale Analysis

A total of 152 pig farms were randomly selected from the five provinces in South Korea. During the experiment, the average temperature and relative humidity was 24.7°C and 74% in summer and 2.4°C and 53% in winter, respectively. The correlation between floor space allowance (FSA) and productivity index was analyzed, including non-productive sow days (NPD), number of weaners (NOW), survival rate (SR), appearance rate of A-grade pork (ARA), and days at a slaughter weight of 110 kg (d-SW) at different growth stages. The objectives of the present study were i) to determine the effect of FSA on the pig productivity index and ii) to suggest the minimum FSA for pigs based on scientific baseline data. For the pregnant sow, NPD could be decreased if pregnant sows were raised with a medium level (M) of FSA (3.10 to 3.67 m²/head) while also keeping the pig house clean which improves hygiene, and operating the ventilation system properly. For the farrowing sows, the NOW tended to decrease as the FSA increased. Similarly, a high level of FSA (H) is significantly negative with weaner SR of farrowing sows (p-value = 0.017), indicating this FSA tends to depress SR. Therefore, a FSA of 2.30 to 6.40 m²/head (very low) could be appropriate for weaners because a limited space can provide a sense of security and protection from external interruptions. The opposite trend was observed that an increase in floor space (>1.12 m²/head) leads to increase the SR of growing pigs. For the fattening pigs, H level of FSA was negatively correlated with SR, but M level of FSA was positively correlated with SR, indicating that SR tended to increase with the FSA of 1.10 to 1.27 m²/head. In contrast, ARA of male fattening pigs showed opposite results. H level of FSA (1.27 to 1.47 m²/head) was suggested to increase productivity because ARA was most affected by H level of space allowance with positive correlation (R² = 0.523). The relationship between the FSA and d-SW of fattening pigs was hard to identify because of the low R² value. However, the farms that provided a relatively large floor space (1.27 to 1.54 m²/head) during the winter period showed d-SW was significantly and negatively affected by FSA.

The Outcomes of Selection in a Closed Herd on a Farm in Operation

A herd of Berkshire pigs was established in 2003 and subjected to selection without introduction of any genetic resources until 2007. The complete pedigree, including 410 boars and 916 sows, as well as the records from 5,845 pigs and 822 litters were used to investigate the results obtained from the selections. The index of selection for breeding values included days to 90 kg (D90kg), backfat thickness (BF) and number of piglets born alive (NBA). The average inbreeding coefficients of pigs were found to be 0.023, 0.008, 0.013, 0.025, 0.026, and 0.005 from 2003 to 2007, respectively. The genetic gains per year were 12.1 g, -0.04 mm, -3.13 days, and 0.181 head for average daily gain (ADG), BF, D90kg, and NBA, respectively. Breeding values of ADG, BF and D90kg were not significantly correlated with inbreeding coefficients of individuals, except for NBA (-0.21). The response per additional 1% of inbreeding was 0.0278 head reduction in NBA. The annual increase of inbreeding was 0.23% and the annual decrease in NBA due to inbreeding was 0.0064 head. This magnitude could be disregarded when compared with the annual gain in NBA (0.181 head). These results suggest that inbreeding and inbreeding depression on ordinary farms can be controlled with a proper breeding scheme and that breeding programs are economical and safe relative to the risks associated with importation of pigs.

Effect of vitamin levels and different stocking densities on performance, nutrient digestibility, and blood characteristics of growing pigs

This study was conducted to evaluate the effects of dietary vitamin levels and stocking densities on growth performance, nutrient digestibility, and blood characteristics in growing pigs. A 2×3 factorial (two vitamin levels, three regimens of stocking densities) arrangement was utilized with 96 pigs (23.10×0.95 kg initial body weight and 63 d of age) for 36 d. The pigs were allocated to pens with different stocking density (0.64, 0.48, and 0.38 m(2)/pig, respectively). The diets used in this study were a normal diet (based on NRC) and a high level of vitamin diet (2-fold higher than normal diet). The ADG and ADFI of pigs were decreased as the stocking density increased (p = 0.03 and p = 0.01, respectively). The G/F of pigs was 5% lower in the high vitamin treatment (p = 0.03) as compared with the control treatment. The apparent total tract digestibility (ATTD) of DM and N digestibility was negatively affected by the high level of vitamin in diets (p = 0.05 and p = 0.04, respectively). Moreover, a significant and negative effect on the ATTD of N was detected in the large groups (linear, p = 0.02). Blood cortisol concentration was increased with increasing stocking density (linear, p = 0.05), and was decreased by high level of vitamin (p = 0.04) at the end of this experiment. Stocking density also caused a linear reduction in WBC concentration (p = 0.05). Our data indicated that the principal effect of stocking density was not reliant on dietary vitamin levels. In conclusion, results indicated that doubling the vitamin supplementation did not improve the growth performance of pigs in high density. However, the blood cortisol concentration was decreased but the ATTD of N digestibility was impaired by high level of vitamin diet.

Effects of Stocking Density or Group Size on Intake, Growth, and Meat Quality of Hanwoo Steers (Bos taurus coreanae)

This study was conducted to investigate the effects of stocking density or group size on feed intake, daily gain, and carcass characteristics of Hanwoo (Korean indigenous breed) steers reared from 7 months to 31 months of age. Thirty Hanwoo steers were divided into four groups with three replicates each (a total of 12 pens). In each group, one (G1), two (G2), three (G3), and four steers (G4) per pen were allocated as treatments. Pen size was 32.0 m², and therefore Hanwoo steers in G1, G2, G3, and G4 were reared under different space allowances, i.e. 32.0, 16.0, 10.6, and 8.0 m²/steer, respectively. Steers were reared following a conventional beef cattle management method in Korea, and were offered a fixed amount of commercial concentrate with ad libitum forages. Results were subjected to analysis of variance with stocking density as the main effect, and significance was declared at p<0.05. Although total feed intake was not significantly altered, it numerically increased in animals of low stocking density (G1) compared to those subjected to high stocking density treatment (i.e. G4). Feed conversion ratio was higher (p<0.05) in G3 compared to G1 and G2. Animals in G1 (low stocking density) grew faster (p<0.05) than those of high stocking density (G3 and G4). Back fat thickness, meat yield index, and meat yield grade were similar among all levels of stocking density. However, longissimus muscle area was larger in G1 and G2 (p<0.01) compared to G3 and G4, and animals in G3 produced smaller carcasses (p<0.05). Carcass quality traits, including marbling score, meat color, fat color, texture, maturity and meat quality grade, as determined by a group of experts, were not significantly different among the treatments. In conclusion, lower stocking density resulted in increased feed efficiency, daily gain, and carcass weight in Hanwoo steers. However it remains unclear whether such differences are the results of stocking density or group size, or a combination of both. Nonetheless, these results confirm previous studies reporting a negative effect of increased stocking density on animal productivity. Further, animal welfare under an intensive farming system in relation to economical return is discussed.

Behavior and handling of physically and immunologically castrated market pigs on farm and going to market

Physical castration is a common management practice on commercial swine farms in the United States to reduce the incidence of boar taint and aggressive behavior. One alternative to physical castration (PC) is to immunologically castrate (IC) male pigs by blocking the gonadotropin-releasing factor (GnRF), thereby reducing levels of LH, FSH, testosterone, and androstenone. The objectives of this study were to evaluate the effects of IC on pig behavior, human-pig interactions, and handling during and after transport. Pigs were given the first immunization at wk 7 of the grower-finisher period, and second immunizations were given at wk 11, 13, or 14 of the grower-finisher period. Behaviors of PC and IC barrows were sampled at 3 time points after entering finishing at 9 wk of age: 7 wk before first injection, 16 wk (after immunization was complete) into finishing, and 1 d before marketing (16 to 19 wk into finishing). Handling during loading and unloading of trailers going to market was also quantified. Before the first injection, intact males showed increased aggression (P=0.014) and mounting (P=0.048), whereas PC barrows spent more (P=0.003) time feeding than intact males. There were treatment×time interactions for lying (P=0.018), aggression (P<0.001), and standing (P=0.009) behaviors. Few differences were observed in pig-human interactions between PC and IC barrows, with IC and PC approaching people in the same amount of time, but IC barrows were more (P<0.001) aggressive in chewing and rubbing on the test person's pant leg and boots. When handling and loading for processing in the home barn, PC barrows were more (P<0.05) vocal than IC barrows. Fewer dead and down pigs were observed among IC (0%) compared with PC barrows (1.17%). Immunological castration may result in similar or improved animal welfare compared to the stress of physical castration without pain relief.

Effects of grouping unfamiliar cohorts, high ambient temperature and stocking density on live performance of growing pigs

Ninety-six crossbred intact male pigs (34.5 +/- 3.5 kg BW) were allocated by weight and vocalization score to a 2 x 2 x 2 dynamic experimental design including two stocking densities (1 or 2 m(2)/pig), two temperatures (22 degrees C and 30 degrees C), and two short groupings of unfamiliar cohorts (six pigs as one pig per group, and six pigs per group). The study was conducted over 8 wk, and live weight gain (WTG) and feed intake (FI; as-fed basis) were measured weekly. During the first week, pigs were housed in individual pens from four independent rooms. To group pigs, pen partitions were removed. Pigs were grouped in Rooms 2 and 3 from wk 2 to 4, and in Rooms 1 and 4 during wk 7. Temperature was increased from 22 degrees C to 30 degrees C in Rooms 1 and 2 during wk 4 and 7. Pen partitions were replaced in Rooms 2 and 3 at the end of wk 4 and in Rooms 1 and 4 at the end of wk 7 to return pigs to their individual pens. Grouping pigs decreased FI during wk 3 (15.08 +/- 0.43 vs. 14.03 +/- 0.41 kg P < 0.10), and during wk 7 (17.42 +/- 0.46 vs. 14.24 +/- 0.41 kg; P < 0.01). In addition, grouping had a negative effect (P < 0.001) on WTG at wk 3 (7.38 +/- 0.28 vs. 5.71 +/- 0.28 kg) and at wk 7 (6.70 +/- 0.26 vs. 2.99 +/- 0.26 kg). For grouped pigs, raising the temperature decreased (P < 0.01) WTG (7.49 +/- 0.29 vs. 6.41 +/- 0.29 kg during wk 4, and 3.37 +/- 0.38 vs. 2.62 +/- 0.38 kg during wk 7). Mean FI was decreased (P < 0.01) with the 30 degrees C treatment during wk 7 only (15.49 +/- 0.33 kg at 22 degrees C compared with 12.99 +/- 0.33 kg at 30 degrees C). Compensatory feed intake was evident after the treatments had ceased at wk 6, whereby previously heat-treated grouped pigs had a higher FI (17.97 +/- 0.45 kg) than the animals individually housed at 22 degrees C (12.99 +/- 0.33 kg). Stocking density effects were noted after the grouping and high temperature treatments had ceased. For instance, during wk 5, low-density-housed pigs grew faster (P < 0.001) than their high-density counterparts (9.04 +/- 0.38 vs. 7.49 +/- 0.29 kg). In conclusion, under the conditions of this study, the grouping of unfamiliar cohorts and high ambient temperature treatments had a detrimental effect on pig performance, and these effects were reversible.

The heritability of the expression of two stress-regulated gene fragments in pigs

Pigs reared in commercial production units sometimes encounter stressors that significantly decrease growth performance. It is hypothesized that response to stress challenges could potentially be used as selection criteria. This study aimed to investigate, in a commercial setting, the heritability of two target genes previously shown to be induced in response to stress, and related to growth performance, in an experimental situation. Blood samples (n = 2,392) were collected from three separate breeding lines of pedigreed and performance-tested boars between 24 to 25 wk of age. The expression levels of a novel fragment, '29a,' and the calcitonin receptor gene (CTR) were quantified using quantitative real-time PCR (qRT-PCR) on a subset (n = 709) of the blood samples. Gene expression levels were corrected for the efficiency of PCR reactions and also computed directly from threshold cycle (Ct) values. Resulting data showed a skewed nonnormal distribution of expression levels for the target genes relative to the endogenous control, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and were highly variable. Analyses were subsequently performed using untransformed and log-transformed data, with outliers identified and deleted in edited data sets. Regardless of the transformation or editing procedures for outliers applied, there was negligible genetic variation for the expression of target genes relative to GAPDH. In contrast, repeatabilities of replicate samples were generally high (between 0.54 and 0.67). Absolute expression levels for GAPDH and 29a were lowly heritable (h2 of about 0.04), although estimates did not exceed their SE. Subsetting the data according to whether the target gene had a higher or lower level of expression than GAPDH was then performed using the relevant Ct values. In the subset where the target gene was more highly expressed than GAPDH, a moderate estimate of heritability (0.18 +/- 0.10) for the log-transformed absolute expression level of 29a was obtained, whereas the estimate for its expression relative to GAPDH was lower (0.09 +/- 0.07). Estimates of heritability did not increase in the subset of low expression data. The limitations of using gene expression measures as potential selection criteria in commercial situations are discussed.

Application of broken-line analysis to assess floor space requirements of nursery and grower-finisher pigs expressed on an allometric basis1

Few issues in swine production are as complex as floor space allowances. One method for pork producers to calculate floor space allowance (A) is to convert BW into a 2-dimensional concept yielding an expression of A = k * BW(0.667). Data on ADG, ADFI, and G:F were obtained from published peer-reviewed studies. Five data sets were created: A = grower-finisher pigs, fully slatted floors, and consistent group size; B = grower-finisher pigs and fully slatted floors (group size did not need to be consistent); C = grower-finisher pigs, partially slatted floors, and consistent group size; D = grower-finisher pigs, partially slatted floors (group size did not need to be consistent); and E = nursery pigs, fully slatted or woven wire floors (group size did not need to be consistent). Each data set was analyzed using a broken-line analysis and a linear regression. For the broken-line analyses, the critical k value, below which a decrease in ADG occurred, varied from 0.0317 to 0.0348. In all cases the effect of space allowance on ADG was significant (P < 0.05). Using the linear analyses based on data with k values of < 0.030, the critical k values for the 4 grower-finisher data sets did not differ from those obtained using the broken-line analysis (0.0358 vs. 0.0336, respectively; P > 0.10); however, none of the linear regressions explained a significant proportion of the variation in ADG. The slopes for the nonplateau portion of the broken-line analyses based on percent values varied among data sets. For every 0.001 decrease in k (approximately 3% of the critical k value), ADG decreased by 0.56 to 1.41%, with an average value of 0.98% for the 5%-based analyses. The use of an allometric approach to express space allowance and broken-line analysis to establish space requirements seem to be useful tools for pig production. The critical k value at which crowding becomes detrimental to the growth of the pig is similar in full- and partial-slat systems and in nursery and grower-finisher stages. The critical point for crowding determined in these analyses approximated current recommendations to ensure the welfare of pigs.

The effect of space allocation on barrow and gilt performance

Two experiments were conducted to determine the variation in response to space allocation between barrows and gilts and to examine an alternative allocation regimen for barrows and gilts. Experimental space allocations in both experiments were achieved by varying the number of pigs per pen in a fully slatted facility. In Exp. 1, barrows were given 0.58 and 0.65 m2/pig (nine and eight pigs per pen, respectively) and gilts were given 0.65 and 0.74 m2/pig (eight and seven pigs per pen, respectively). In addition, barrows at 0.58 m2/pig were fed diets formulated for barrows or diets formulated for gilts. Barrows grew 4.8% slower (P = 0.031) and ate 3.1% less feed daily (P = 0.062) at 0.58 vs. 0.65 m2/pig from 22 to 115 kg BW, with no difference in feed conversion, daily lean gain, carcass lean percent, or variation in weight within the pen at time of first pig removal to slaughter. There was no improvement in daily gain, feed intake, feed efficiency, lean gain, or carcass lean percent when gilts were given 0.74 vs. 0.65 m2/pig from 22 to 115 kg BW. There was no difference in performance between the population that consisted of barrows and gilts at 0.65 m2/pig vs. the population of barrows at 0.58 m2/pig and gilts at 0.74 m2/pig. There was no difference in performance by barrows at 0.58 m2/pig when fed either barrow or gilt diets, except for a slight increase (P = 0.078) in within-pen weight variation when the first pig was removed for slaughter for the barrows fed gilt diets. In Exp. 2, barrows and gilts were given 0.58 m2/pig or 0.74 m2/pig (18 vs. 14 pigs per pen) from weaning (mean age 17 d) to slaughter on d 168 postweaning. There were no interactions between space allocation and gender. Daily gain and feed intake were decreased by 2.8% (P = 0.037) and 2.9% (P = 0.084), respectively, with no effect on feed conversion or standardized fat-free lean daily gain for the 0.58 vs. the 0.74 m2/pig treatment, whereas total live weight gain per pen was increased 20.8% (P < 0.001). Results of Exp. 1 suggest that space allocation can be used to achieve similar growth rates between barrows and gilts, and results of Exp. 2 suggest that the response to space allocation is similar for barrows and gilts. The difference in magnitude of response to space allocation between experiments may be due in part to when the social group was formed, with a smaller difference in performance in Exp. 2 associated with a stable social group from weaning to slaughter.

Effects of combined Actinobacillus pleuropneumoniae challenge and change in environmental temperature on calcitonin receptor expression levels in growing pigs

We have identified through differential gene expression polymerase chain reaction that porcine calcitonin receptor expression levels could be altered in porcine leukocytes in response to Actinobacillus pleuropneumoniae (App) challenge. This study further investigates the effects of mild pleuropneumonia and changes in environmental temperature, singularly and in combination, on leukocyte expression levels of the calcitonin receptor in domestic pigs. Forty entire male pigs were allocated by weight and temperament at a starting liveweight of 33 0± 5 kg to 4 treatments: control (22°C room temperature); A. pleuropneumoniae challenge (Day 1); varied temperature (15°C for 8 h on Days 0, 1, and 2; 30°C for 24 h on Day 6); and the combined A. pleuropneumoniae challenge and varied temperature treatment. The analysis of the leukocyte expression levels of calcitonin receptor using semi-quantitative reverse transcription PCR revealed that calcitonin receptor was up-regulated in response to the A. pleuropneumoniae challenge (P < 0.001) and the temperature treatment (P < 0.001). In addition, up-regulation of the calcitonin receptor correlated with decreased weight gain, feed intake, and plasma IGF-I. Thus, expression levels of the calcitonin receptor reflect changes in growth performance associated with alteration in ambient temperature and App challenge. In addition, this study indicates that calcitonin receptor expression represents a mechanism through which endocrine and immune systems interact to affect growth.

Predicting the consequences of social stressors on pig food intake and performance1

The influence of social stressors on pig performance, although undeniable, is frequently underestimated, and in pig growth modeling is generally ignored. The aims here were to quantify the effects of the main social stressors (i.e., group size, space allowance, feeder space allowance, and mixing) on the performance of growing pigs and to incorporate these relationships into a general growth simulation model. Effects of the individual stressors were described by conceptual equations derived on biological grounds. Parameter values were estimated from experimental data, while taking steps to avoid the problems of using a strictly empirical approach. It was assumed that social stress decreases the capacity of the animal to attain its potential. This is equivalent to lowering the maximum rate of daily gain (ADGp, kg/d). Because it is generally assumed that animals eat to attain their potential, a decrease in ADGp necessarily leads to a decrease in intake. Genetic variation among genotypes in their ability to cope with social stressors was accounted for by introducing an extra genetic parameter (EX) into the model. The value of EX adjusts both the intensity of stressor at which the animal becomes effectively stressed and the extent to which stress decreases performance and increases energy expenditure at a given stressor intensity. Rather than using an empirical adjustment to predict values for the model output variables, such as intake and gain, the chosen functional forms were integrated into a general growth model as mechanistic equations. This allowed the effects of interactions that exist between social stressors and the other variables, such as the genotype, feed composition, and environment on pig intake and growth, to be explored and, at least in principle, predicted. The adapted model is able to predict the performance of pigs differing in both the potential and ability to cope with environmental stressors when raised under given dietary, physical, and social environmental conditions. The social stressor equations developed here can be incorporated into other pig growth simulation models.

Effect of group size on performance of growing-finishing pigs

Six hundred forty growing-finishing pigs (initial BW = 23.2 +/- 4.8 kg) were used in a 12-wk study (final BW = 95.5 +/- 10.2 kg) to quantify the effects of group size (10, 20, 40, and 80 pigs/pen) on performance, tail biting, and use of widely distributed feed resources. One single-space wet/dry feeder was provided for every 10 pigs, and floor allowance was 0.76 m2/pig in all treatment groups. Weight gain and feed intake were measured every 2 wk. At weighing, a tail-biting injury score was given to each pig. Blood samples were collected and analyzed for neutrophil:lymphocyte ratio before regrouping at the beginning of the experiment, 24 to 48 h after regrouping, and on the last day of each trial. The use of feeders by individual pigs was assessed by behavioral observations. Average daily gain for the entire 12-wk trial did not differ among group sizes (861, 873, 854, and 845 g/d for groups of 10, 20, 40, and 80, respectively; P > 0.10). During the first 2 wk, ADG was lower for pigs in groups of 40 (554 g/d) than pigs in groups of 10 (632 g/d; P < 0.05), but not pigs in groups of 20 or 80 (602 and 605 g/d, respectively). Average daily feed intake, feed efficiency, and variability in final BW within a pen also did not differ among group sizes. Tail-biting injury scores increased throughout the study, but did not differ among group sizes. Similar proportions of pigs were removed from the trial for health reasons, primarily due to tail biting, in all treatments. Individual pigs in each group size ate from most, if not all, of the feeders in the pen. There was no evidence of spatial subgrouping within the larger groups. The results suggest that housing growing-finishing pigs in groups of up to 80 pigs is not detrimental to productivity and health if space allowance is adequate and feed resources are evenly distributed.