Skip to main content
PMC home page
Translational Animal Science logoLink to Translational Animal Science
. 2018 Jun 22;2(4):358–364. doi: 10.1093/tas/txy073

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

Marvin E Wastell 1,✉, Cesar A P Garbossa 2, Allan P Schinckel 3
PMCID: PMC7200493  PMID: 32704718

Abstract

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 (m2)=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.

Keywords: feeder space, floor space, k value, space allocation, swine

INTRODUCTION

The economic return of a pig production system is related to the housing capacity of the production sites as well as the technologies employed to increase pig growth performance and gain efficiency, considering it is important to diminish facility cost per pig (Thomas et al., 2017). Gain efficiency is very important, as approximately 60%–75% of the total postweaning pig production costs are associated with feed costs (Honeyman, 1991; Wade and Barkley, 1992). In modern swine production, the pork processing plants have targeted heavier market weights (Wu et al., 2017). With increased market weights, the pen space required for modern pigs and the feeder space per pig should be evaluated to balance building utilization and production efficiency.

A number of researchers have found that increased group sizes do not affect the pig performance when the pigs are given equal pen space and ad libitum access to feed (McConnell et al., 1987; Walker, 1991; Turner et al., 2003; Turner and Edwards, 2004). The majority of the production systems for pigs use fully or partially slatted floors, a liquid effluent system, with group sizes from 5 to 50 pigs and approximately 0.7 m2 of floor space allowance per pig (Morrison et al., 2007).

However, when less pen floor space allowance is provided per pig, pig growth rate is reduced, more markedly with pens for smaller groups as demonstrated by Thomas et al. (2017), which had nine pigs per pen. Besides the reduced growth performance, restricted pen floor space allowance can cause behavioral problems, increase plasma glucocorticoid levels, and reduce animal welfare (Randolph et al., 1981; Kornegay, 1986; Meunier-Salaun et al., 1987).

Feeder design and management can affect pig growth and the pigs’ capacity to eat, so it is extremely important to evaluate the impact of the number of pigs per feeder space with each model of the commercial feeder. Past research has been done with dry feeders on the impact of the number of pigs per feeder space and has produced variable results, possibly due to different models of feeders and different levels of feeder adjustment.

Considering that feeder space per pig and pen floor space allowance per pig can affect pig growth performance, the objective of the trial was to evaluate the effects of different feeder stocking density and pen stocking density on the growth performance of grow-finish pigs fed with wet/dry feeders.

MATERIALS AND METHODS

Animal procedures were consistent with the Guide for the Care and Use of Animals in Agricultural Research and Teaching (FASS, 2010).

General

The trial was conducted at a commercial research finishing barn located in Southwest Minnesota from October 2015 to September 2016. The facility was double curtain sided with totally slatted floors and environmentally controlled with sprinklers to reduce summertime heat stress and heaters for winter time temperature control. Each building contained 44 pens. The pens had adjustable gating to provide the different floor space allowances, so each floor space allowance was arranged by moving the gates after measurement of the floor space. The experimental treatments were designed as a two by three factorial arrangement (pen space of 0.65 or 0.78 m2/pig × 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 Crystal Spring Wet/Dry single-space double-sided feeder model F1-115 (Ste. Agathe, MB), space of 37.5 cm of length, with one nipple drinker. The drinker of the feeder was the only provided in each pen. The feed was delivered by a robotic feeding system (FeedPro; Feedlogic Corp., Wilmar, MN), which recorded the daily individual pen feed additions.

Animals and Performance

Three thousand one hundred and eighty-two terminal cross pigs (PIC line 359 sires × 1,050 dams, barrows, and gilts) from three consecutive grow-finish groups (initial BW of 21.5 ± 0.42, 31.6 ± 1.18, and 29.4 ± 0.28 kg for replicate 1, 2, and 3, respectively) were used. Pigs were randomly assigned to each pen at the start of the trial, and the trial continued for 106, 94, and 100 d for the first, second, and third replicates, respectively, for each replicate pen group remained intact until the end of the experiment. No pigs were removed for marketing until after the experiment ended.

Initial BW was equalized for each pen, and the pens were randomly distributed to one of the six treatments with seven pens per treatment for each trial group. 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 feeding program with a seven-phase corn-soybean meal base feed in mash form (Table 1). The diets were formulated to achieve or exceed NRC (2012) requirements for grow-finish pigs.

Table 1.

Composition of the trial feeds (as-fed basis)

Ingredient, % Phase1
1 2 3 4 5 6 7
Corn 42.62 42.55 45.02 48.06 52.77 61.12 66.76
Soybean meal, 46.5% CP 10.44 5.63 3.15 0.12 0.49 2.28 1.72
DDGS2 40.00 45.00 45.00 45.00 40.00 30.00 25.00
Tallow 4.00 4.00 4.00 4.00 4.00 4.00 4.00
Salt 0.45 0.45 0.45 0.45 0.45 0.45 0.45
Calcium carbonate, 38% Ca 1.27 1.30 1.28 1.27 1.19 1.05 0.97
Mono dicalcium P, 21% P 0.22 0.07 0.00 0.00 0.00 0.00 0.00
Potassium chloride 0.00 0.00 0.10 0.10 0.10 0.10 0.10
Premix3 1.00 1.00 1.00 1.00 1.00 1.00 1.00
Total 100.0 100.0 100.0 100.0 100.0 100.0 100.0
Calculated analysis
 Crude protein, % 19.4 18.5 17.5 16.3 15.4 14 12.7
 ME, kcal/kg 2970 2964 2953 2968 2984 2991 3003
 Fat, % 8.11 8.11 7.98 8.15 8.09 7.49 7.29
 Crude fiber, % 3.55 3.69 3.65 3.60 3.39 2.99 2.76
 Calcium, % 0.58 0.55 0.53 0.51 0.48 0.43 0.4
 Phosphorus, % 0.52 0.5 0.48 0.47 0.44 0.4 0.37
 Lys (total), % 1.31 1.22 1.12 1.02 0.95 0.87 0.79
 Met (total), % 0.37 0.35 0.34 0.32 0.30 0.27 0.25
 Thr (total), % 0.82 0.77 0.73 0.67 0.64 0.58 0.53
 Trp (total), % 0.24 0.23 0.21 0.19 0.18 0.16 0.15
Open in a new tab

1Phase 1–7 diets were fed from 25 to 34 kg, 34 to 43 kg, 43 to 61 kg, 61 to 75 kg, 75 to 86 kg, 86 to 98 kg, and 98 to slaughter, respectively.

2DDGS = dried distillers grains with solubles.

3Mineral and vitamin premix provided per kilogram of diet: 4,412,200 IU vitamin A, 551,200 IU vitamin D, 17,700 IU vitamin E, 1,782 mg vitamin K, 15.5 mg vitamin B12, 19,876 mg niacin, 11,065 mg pantothenic acid, 3,318 mg riboflavin, 1,106 mg Zn, 1,100 mg Fe, 313 mg Mn, 107 mg Cu, 2 mg I, and 2 mg Se. Amino acid premix provided per kilogram of diet: Phase 1: 11.74 g lysine, 0.43 g methionine, 2.83 g threonine, and 1.29 g tryptophan; Phase 2: 11.91 g lysine, 2.47 g threonine, and 1.39 g tryptophan; Phase 3: 11.23 g lysine, 2.42 g threonine, and 1.34 g tryptophan; Phase 4: 10.86 g lysine, 2.08 g threonine, and 1.33 g tryptophan; Phase 5: 9.84 g lysine, 2.12 g threonine, and 1.19 g tryptophan; Phase 6: 8.57 g lysine, 1.98 g threonine, and 1.01 g tryptophan; Phase 7: 7.77 g lysine, 1.88 g threonine, and 0.92 g tryptophan.

Pigs were weighed by pen at the start of trial, at approximately every 21 d of the trial, and at the end of the trial to calculate ADG, all the feed placed in the feeders was weighed and at the end of the trial the remaining feed in the feeders was weighed to determine ADFI and G:F.

Evaluation of k Value

To express floor space allowance, k value was used, as it describes pen space as a function of effective pig space requirements (BW0.67). The k values were calculated using a formula reported by Whittemore (1998): space per pig (m2)=k×BW (kg)0.67. According to Gonyou et al. (2006), a k value of 0.0336 is required for maximal feed intake and ADG for grow-finish pigs with fully slatted flooring, as k value lower than 0.0336 reduces feed intake and consequently ADG.

Statistical Analysis

All variables measured were tested for normality by the Shapiro–Wilk test before analysis with P < 0.05, and any variable that failed to follow a normal distribution was transformed through the RANK procedure of SAS (SAS Inst. Inc., Cary, NC). The PROC RANK statement with the NORMAL option was used to produce a normalized transformed variable. All data were analyzed using the MIXED procedure of SAS (SAS Institute Inc., Cary, NC) as a randomized complete block design (replicate) in a factorial scheme with floor space allowance (0.65 or 0.78 m2/pig) and pigs per feeder space (10, 13, or 16 pigs per feeder space). Pen was considered as the experimental unit. Initial analyses found no significant interactions and thus were deleted from the model. The pigs per feeder space treatments were analyzed as linear and quadratic orthogonal contrasts. The effects of floor space allowance per pig were compared by F test. All data are reported as least squares means, and the greatest standard errors (SEM) were reported. Results are considered significant if P < 0.05.

RESULTS

No interactions (P > 0.05) of floor space allowance with pigs per feeder space were observed. Pigs allocated in pens with 0.65 m2/pig had reduced ADG during the growing phase (Table 2, 1.00 vs. 1.02 kg/d, P < 0.001), finishing phase (1.03 vs. 1.05 kg/d, P = 0.033), and the overall period (1.00 vs. 1.02 kg/d, P = 0.002).

Table 2.

Effects of floor space allocation on growing-finishing pig performance

Item Space allocation per pig, m2 SEM P value
0.65 0.78
Growing phase
 Day 0 weight, kg 27.5 27.5 3.060 0.566
 ADG, kg 1.00 1.02 0.016 <0.001
 Dead/removed, % 1.7 1.7 0.943 0.704
Finishing phase
 Day 70 weight, kg 97.7 99.4 2.154 <0.001
 ADG, kg 1.03 1.05 0.035 0.033
 Day 100 final weight, kg 128.8 129.5 0.242 0.026
 Dead/removed, % 1.2 1.2 0.921 0.758
Overall
 ADG, kg 1.01 1.03 0.009 0.002
 ADFI, kg 2.52 2.61 0.155 <0.001
 G:F 0.402 0.397 0.029 0.039
 Dead/removed, % 2.9 2.9 0.913 0.743
Open in a new tab

Sixty-three replicates per treatment with 1,591 pigs per treatment was used.

As suggested by previous studies with dry feeders, these pigs had lower BW at 70 d (97.7 vs. 99.4 kg, P < 0.001) and final BW (128.8 vs. 129.5 kg, P = 0.026) and reduced ADFI (2.52 vs. 2.61 kg/d, P < 0.001) than pigs with 0.78 m2/pig floor space allowance. However, the overall G:F was improved (0.402 vs. 0.397, P = 0.039) for pigs with less pen space. Floor space allowance had no effect for the percentage of dead or removed pigs.

It was estimated that the BW in which pen space became limiting (k = 0.0336) for the floor space allowance of 0.65 m2/pig was 85.0 kg and at 111.7 kg BW for the floor space allowance of 0.78 m2/pig (Table 3). At 70 d, the BWs for pigs allocated in pens with 0.65 and 0.78 m2/pig were 97.7 and 99.4 with estimated k values of 0.0306 and 0.0363, respectively. The final BWs were 128.8 and 129.5 kg with estimated k values of 0.0255 and 0.0304 for pigs assigned to 0.65 and 0.78 m2/pig.

Table 3.

Determination of k values for different space allocations and pig weights1

Item Space allocation per pig, m2 k value2,3
0.65 0.78 0.65 m2 0.78 m2
Day 0 weight, kg 27.5 27.5 0.0724 0.0869
Day 70 weight, kg 97.7 99.4 0.0306 0.0363
Day 100 final weight, kg 128.8 129.5 0.0255 0.0304
BW when k = 0.0336, kg4 85.0 111.7
Open in a new tab

1Average pig weight reported for each space allocation and weigh day.

2 k values were calculated using a formula reported by Whittemore (1998): space per pig (m2)=k×BW (kg)0.67.

3Shaded background indicates k values below 0.0336, critical k value for adequate feed intake as defined by Gonyou et al. (2006).

4Estimated body weight for space allocation when k = 0.0336, the critical k value for adequate feed intake for grow-finish, fully slatted flooring and equal group sizes (Gonyou et al., 2006).

The number of pigs per feeder space did not affect ADG (Table 4, P > 0.14) during the growing phase. Average daily gain during the finishing phase had a quadratic (P = 0.010) relationship with the number of the pigs per feeder. In the same way, the overall ADG had a quadratic relationship (P = 0.005) with the number of pigs per feeder space with the maximal ADG at 10 pigs per feeder space. Final BW was reduced with increased number of pigs per feeder space (linear P = 0.001).

Table 4.

Effects of pigs per feeder space on growing-finishing pig performance

Item Pigs per feeder space SEM P value
10 13 16 Linear Quadratic
Growing phase
 Day 0 weight, kg 27.5 27.5 27.5 3.061 0.877 0.829
 ADG, kg 1.02 1.01 1.01 0.016 0.156 0.142
 Dead/removed, % 1.6 1.9 1.6 0.987 0.848 0.793
Finishing phase
 Day 70 weight, kg 99.0 98.5 98.1 2.041 0.244 0.158
 ADG, kg 1.07 1.02 1.03 0.035 0.488 0.010
 Day 100 final weight, kg 129.7 129.4 128.4 0.326 0.001 0.028
 Dead/removed, % 1.1 1.3 1.3 0.865 0.799 0.575
Overall
 ADG, kg/d 1.03 1.01 1.01 0.010 0.152 0.005
 ADFI, kg/d 2.62 2.52 2.55 0.156 0.385 <0.0001
 G:F 0.395 0.404 0.400 0.029 0.877 0.005
 Dead/removed, % 2.6 3.2 2.9 1.000 0.950 0.568
Open in a new tab

Forty-two replicates per treatment with 816, 1,062, and 1,304 pigs, respectively, for the treatments with 10, 13, or 16 pigs per feeder space was used.

Daily feed intake had a quadratic relationship (P < 0.001) with the number of pigs per feeder space. Gain efficiency had a quadratic relationship (P = 0.005) with the number of pigs per feeder space. The number of pigs per feeder space had no effect for the percentage of dead or removed pigs.

DISCUSSION

Reduction of the floor space allowance by increasing the number of pigs per space unit reduces the housing cost per pig (Brumm and Gonyou, 2001); however, with reduction of floor space allowance, pigs have reduced ADFI, ADG, and consequently reduced BW (Brumm and Miller, 1996; Gonyou and Stricklin, 1998; Jensen et al., 2012; Thomas et al., 2017). It is common for crowded pigs to eat fewer meals; however, pigs spend more time eating each meal (Meunier-Salaun et al., 1987; Hyun et al., 1998).

Johnston et al. (2017) conducted a series of trials and established the ideal floor space allowance for pigs weighing 130 kg is 0.89 m2/pig as they did not observe any improvement in final BW and ADG beyond this floor space allowance, the group size was constant across treatments however varied across trials, varying from 6 to 19 pigs per pen.

Increased pen density could cause welfare problems because crowded pigs tend to have more aggressive behavior and higher lesion scores (Fu et al., 2016). Also, increased stocking density reduces the area available for lying so pigs tend to disturb each other more often (Bulens et al., 2017).

However, the results of this trial contradict some past research that found G:F was unchanged (Brumm and Miller, 1996; Gonyou and Stricklin, 1998; Jensen et al., 2012; Thomas et al., 2017) or decreased (Street and Gonyou, 2008; Flohr et al., 2016) with decreased floor space allowance per pig. In this trial, G:F was greater for pigs with less floor space allowance. This observation is in agreement with a meta-analysis (Averós et al., 2012) that suggested that the pig floor space required for maximal G:F is reduced if the pigs are housed on fully slatted floors compared with pens with nonslatted floor. Despite the small lower ADG (20 g/d) and ADFI (90 g/d) of pigs with the floor space allowance of 0.65 m2, the pigs had a small improvement of G:F for overall grow-finish period.

These findings are important considering the final BW difference of 0.7 kg represents less than 1 d of ADG for the overall period; however, the difference on ADFI represents 9.00 kg of feed for the overall period of 100 d, being economically more representative.

The percentage of dead or removed pigs were the same for the both floor space allowances treatments during the grower, finishing phase and consequently the overall period and it was lower than 4.44% (Metafarms Analytics Team, 2017) observed in commercial US pig farms. This suggests suggested that problems associated with welfare were not present in this trial.

Floor space allowance was expressed using the allometric approach suggested by Gonyou et al. (2006); the minimum k value of 0.0336 represents the best value for pigs to have an ideal ADFI and ADG, associated with floor space allowance. For this study, both floor space allowance treatments exceeded the minimum value of 0.0336 for k value for maximal ADFI and ADG for most of the finish period. Most likely, pigs that were allocated with 0.65 m2/pig had restricted ADFI after they reached 85.0 kg BW and resulted in the lower DFI for this group of pigs.

It has been suggested that values proposed by Gonyou et al. (2006) may underestimate the requirement of floor space allowance for heavy pigs (over 120 kg of BW), and it should be revaluated for heavy pigs (Potter et al., 2010; Flohr et al., 2016; Johnston et al., 2017). If the density increases in a reasonable manner, the total BW produced per unit of fixed building assets increase, generating a greater net revenue over facility costs (Powell and Brumm, 1993; Flohr et al., 2016).

According to NRC (2012), when the pigs are crowded with k values lower than 0.0336, the ADFI is reduced and consequently growth rate is worsened. If adequate floor space allowance is not provided, the impact of reduce floor space allowance on pig performance depends on the magnitude of the restriction. Flohr et al. (2015) conducted a meta-analysis and established equations to predict ADG, ADFI, and G:F based on the BW of pigs. From this meta-analysis, for each 0.001 below, the critical value of k (0.0336), ADG, ADFI, and G:F should decrease by 0.88%, 0.58%, and 0.31%, respectively, for pigs with more than 125 kg of BW, contradictory for the present trial G:F was improved with lower floor space allocation.

Another factor that could impair the real evaluation of the ideal value proposed by Gonyou et al. (2006) is that his trials were made with dry feeders and it can impact the speed of which the animals eat, so these values must be re-established to ensure which would be the ideal k value that does not harm the ADFI.

The group size of the pigs was adjusted with 20, 26, and 32 pigs per pen to achieve the 10, 13, and 16 pigs per feeder space. When pigs were housed in groups of 18 or 108 pigs, the size of the group did not affect ADG (Street and Gonyou, 2008). Schmolke et al. (2003) evaluated groups of 10, 20, 40, and 80 pigs and verified that housing growing-finishing pigs in groups of up to 80 pigs was not detrimental to productivity and health. These findings are important to ensure that the group size did not have effect over the performance variables of the present trial.

Restricted feeder space in grow-finish pigs increases ingestion rate, reduces the duration of visits to the feeder as well as the time spent eating (Hsia and Wood-Gush, 1984; Brumm and Gonyou, 2001). In this trial, pigs with the greatest feeder space had a greater ADFI, in agreement with Averós et al. (2012) that reported when the feeder places per pig are increased, the pigs spend more time eating.

However, with more feeder places per pig, ADFI can be associated with an increase in feed wastage. With more restricted feeder space pigs tend to reduce feed wastage, something that may have occurred in this trial, as the pigs with the least number of pigs per feeder space had a poorer G:F, in disagreement with previous research (Spoolder et al., 1999; Gonyou and Lou, 2000) both treatments 13 and 16 pigs per feeder space had a better feed conversion than 10 pigs per feeder space in the present trial.

Gonyou and Lou (2000) demonstrated that pigs fed with wet/dry feeders usually have greater ADFI and ADG than dry feeders; similarly, Walker (1990) verified pigs fed from wet/dry feeders tend to have a greater feed intake. The increase in weight gain would be a consequence of greater feed intake (Maton and Daelemans, 1992). Pigs fed from wet/dry feeders have shorter feeder visits and have higher ingestion rates compared with dry feeders (Averós et al., 2012), although pigs fed wet/dry feeders eat more feed and gain more weight than those fed conventional feeders, feed conversion does not change (Gonyou and Lou, 2000). Wet/dry feeders have the ability to accommodate more pigs per feeder space, without harming the performance of the pigs, as wet feed is eaten faster than dry feed (Gonyou and Lou, 2000).

According to Bates et al. (1995), the traditional recommendation of pigs per feeder space with dry feeders was five; however, the same researcher conducted a trial and found that 10 pigs per feeder space do not have any detrimental effect on pig performance. The results in our study showed that there was not a detrimental effect on pig performance with 13 pigs per wet/dry feeder space. In conclusion, a floor space allowance of 0.65 m2/pig marginally reduced the ADFI and ADG during the finisher phase and overall. 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.

LITERATURE CITED

  1. Averós X., Brossard L., Dourmad J. Y., de Greef K. H., Edwards S. A., and Meunier-Salaün M. C.. 2012. Meta-analysis on the effects of the physical environment, animal traits, feeder and feed characteristics on the feeding behavior and performance of growing-finishing pigs. Animal 8:275–1289. doi: 10.1017/S1751731112000328 [DOI] [PubMed] [Google Scholar]
  2. Bates R. O., Morrow-Tesch J. L., and Neal S. M.. 1995. The effect of feeder space allocation on pig performance. Prof. Anim. Sci. 11:135–138. doi: 10.15232/S1080-7446(15)32577-8 [DOI] [Google Scholar]
  3. Brumm M. C., and Gonyou H. W.. 2001. Effects of facility design on behavior and feed and water intake. In: Lewis A. J. and Southern L. L., editors. Swine nutrition. 2nd ed. Boca Raton (FL): CRC Press LLC; p. 499–517. [Google Scholar]
  4. Brumm M. C., and Miller P. S.. 1996. Response of pigs to space allocation and diets varying in nutrient density. J. Anim. Sci. 74:2730–2737. doi: 10.2527/1996.74112730x [DOI] [PubMed] [Google Scholar]
  5. Bulens A., Van Beirendonck S., Van Thielen J., Buys N., and Driessen B.. 2017. A two-level pen for fattening pigs: effects on behavior, performance, and postslaughter measurements. J. Anim. Sci. 95:616–625. doi: 10.2527/jas.2016.0831 [DOI] [PubMed] [Google Scholar]
  6. Federation of Animal Science Societies (FASS) 2010. Guide for the care and use of agricultural animals in research and teaching. 3rd ed. Champaign (IL): FASS; [accessed January 15, 2018]. http://www.fass.org. [Google Scholar]
  7. Flohr J. R., Tokach M. D., DeRouchey J. M., Woodworth J. C., Goodband R. D., and Dritz S. S.. 2016. Evaluating the removal of pigs from a group and subsequent floor space allowance on the growth performance of heavy-weight finishing pigs. J. Anim. Sci. 94:4388–4400. doi: 10.2527/jas2016-0407 [DOI] [PubMed] [Google Scholar]
  8. Flohr J. R., Tokach M. D., Dritz S. S., Woodworth J. C., DeRouchey J. M., and Goodband R. D.. 2015. Using meta-analyses to generate alternative prediction equations for the space requirements of finishing pigs. Kansas Agric. Exp. Station Res. Rep. 1:1–20. doi: 10.4148/2378-5977.1144 [DOI] [Google Scholar]
  9. Fu L., Li H., Liang T., Zhou B., Chou Q., Schinckel A. P., Yang X., Zhao R., Li P., and Huang R.. 2016. Stocking density affects welfare indicators of growing pigs of different group sizes after regrouping. Appl. Anim. Behav. Sci. 174:42–50. doi: 10.1016/j.applanim.2015.10.002 [DOI] [Google Scholar]
  10. Gonyou H. W., Brumm M. C., Bush E., Deen J., Edwards S. A., Fangman T., McGlone J. J., Meunier-Salaun M., Morrison R. B., Spoolder H., et al. . 2006. Application of broken-line analysis to assess floor space requirements of nursery and grower-finisher pigs expressed on an allometric basis. J. Anim. Sci. 84:229–235. doi: 10.2527/2006.841229x [DOI] [PubMed] [Google Scholar]
  11. Gonyou H. W., and Lou Z.. 2000. Effects of eating space and availability of water in feeders on productivity and eating behavior of grower/finisher pigs. J. Anim. Sci. 78:865–870. doi: 10.2527/2000.784865x [DOI] [PubMed] [Google Scholar]
  12. Gonyou H. W., and Stricklin W. R.. 1998. Effects of floor area allowance and group size on the productivity of growing/finishing pigs. J. Anim. Sci. 76:1326–1330. doi: 10.2527/1998.7651326x [DOI] [PubMed] [Google Scholar]
  13. Honeyman M. S. 1991. Sustainable swine production in the U.S. Corn Beit. Am. J. Alternative Agr. 6:63–70. doi: 10.1017/S0889189300003878 [DOI] [Google Scholar]
  14. Hsia L. C., and Wood-Gush D. G. M.. 1984. Social facilitation in the feeding behaviour of pigs and the effect of rank. Appl. Anim. Ethol. 11:265–270. doi: 10.1016/0304-3762(84)90033-6 [DOI] [Google Scholar]
  15. Hyun Y., Ellis M., and Johnson R. W.. 1998. Effects of feeder type, space allowance, and mixing on the growth performance and feed intake pattern of growing pigs. J. Anim. Sci. 76:2771–2778. doi: 10.2527/1998.76112771x [DOI] [PubMed] [Google Scholar]
  16. Jensen T., Nielsen C. K., Vinther J., and D’Eath R. B.. 2012. The effect of space allowance for finishing pigs on productivity and pen hygiene. Livest. Sci. 149:33–40. doi: 10.1016/j.livsci.2012.06.018 [DOI] [Google Scholar]
  17. Johnston L. J., Rozeboom D. W., Goodband R. D., Moeller S. J., Shannon M. C., and Schieck S. J.. 2017. Effect of floor space allowances on growth performance of finishing pigs marketed at 138 kilograms. J. Anim. Sci. 11:4917–4925. doi: 10.2527/jas2017.1870 [DOI] [PMC free article] [PubMed] [Google Scholar]
  18. Kornegay E. T. 1986. Stocking density for growing-finishing swine. Proc. Ann. Meet. Am. Assoc. Swine Pract. 1:16–18. [Google Scholar]
  19. Maton A., and Daelemans J.. 1992. Third comparative study viz. the circular wet-feeder versus the dry-feed hopper for ad libitum feeding and general conclusions concerning wet feeding versus dry feeding of finishing pigs. Rev. Agr. (Brussels) 45:531–539. [Google Scholar]
  20. McConnell J. C., Eargle J. C., and Waldorf R. C.. 1987. Effects of weaning weight, co-mingling, group size and room temperature on pig performance. J. Anim. Sci. 65:1201–1206. doi: 10.2527/jas1987.6551201x [DOI] [PubMed] [Google Scholar]
  21. Metafarms Analytics Team 2017. Pork production mortality higher across board in Q2. Feedstuffs 89 [accessed November 26, 2016] http://www.metafarms.com/uploads/2/4/0/4/24044637/feedstuffsreprint_november_2017_pg_22.indd.pdf. [Google Scholar]
  22. Meunier-Salaun M. C., Vantrimponte M. N., Raab A., and Dantzer R.. 1987. Effect of floor area restriction upon performance, behavior and physiology of growing-finishing pigs. J. Anim. Sci. 64:1371–1377. doi: 10.2527/jas1987.6451371x [DOI] [PubMed] [Google Scholar]
  23. Morrison R. S., Johnston L. J., and Hilbrands A. M.. 2007. A note on the effects of two versus one feeder locations on the feeding behaviour and growth performance of pigs in a deep-litter, large group housing system. Appl. Anim. Behav. Sci. 107:157–161. doi: 10.1016/j.applanim.2006.09.009 [DOI] [Google Scholar]
  24. NRC 2012. Nutrient requirements of swine. 11th rev. ed. Washington (DC): The National Academies Press. [Google Scholar]
  25. Potter M. L., Dritz S. S., Tokach M. D., DeRouchey J. M., Goodband R. D., and Nelssen J. L.. 2010. Effects of increasing stocking density on finishing pig performance. Kansas Swine Ind. Day Rep. Prog. No. 1038. Manhattan (KS): Kansas State University Agricultural Experiment Station; p. 216–222. [Google Scholar]
  26. Powell T. A., Brumm M. C., and Massey R. E.. 1993. Economics of space allocation for grower-finisher hogs: a simulation approach. Rev. Agric. Econ. 15:133–141. doi: 10.2307/1349717 [DOI] [Google Scholar]
  27. Randolph J. H., Cromwell G. L., Stahly T. S., and Kratzer D. D.. 1981. Effects of group size and space allowance on performance and behaviour of swine. J. Anim. Sci. 53:922–927. doi: 10.2527/jas1981.534922x [DOI] [Google Scholar]
  28. Schmolke S. A., Li Y. Z., and Gonyou H. W.. 2003. Effect of group size on performance of growing-finishing pigs. J. Anim. Sci. 81:874–878. doi: 10.2527/2003.814874x [DOI] [PubMed] [Google Scholar]
  29. Spoolder H. A. M., Edwards S. A., and Corning S.. 1999. Effects of group size and feeder space allowance on welfare in finishing pigs. Anim. Sci. 69:481–489. doi: 10.1017/S135772980005133X [DOI] [Google Scholar]
  30. Street B. R., and Gonyou H. W.. 2008. Effects of housing finishing pigs in two group sizes and at two floor space allocations on production, health, behavior, and physiological variables. J. Anim. Sci. 86:982–991. doi: 10.2527/jas.2007-0449 [DOI] [PubMed] [Google Scholar]
  31. Thomas L. L., Goodband R. D., Woodworth J. C., Tokach M. D., DeRouchey J. M., and Dritz S. S.. 2017. Effects of space allocation on finishing pig growth performance and carcass characteristics. Transl. Anim. Sci. 1:351–357. doi: 10.2527/tas2017.0042 [DOI] [PMC free article] [PubMed] [Google Scholar]
  32. Turner S. P., Allcroft D. J., and Edwards S. A.. 2003. Housing pigs in large social groups: a review of implications for performance and other economic traits. Liv. Prod. Sci. 82:39–51. doi: 10.1016/S0301-6226(03)00008-3 [DOI] [Google Scholar]
  33. Turner S. P., and Edwards S. A.. 2004. Housing immature domestic pigs in large social groups: implications for social organisation in a hierarchical society. Appl. Anim. Behav. Sci. 87:239–253. doi: 10.1016/j.applanim.2004.01.010 [DOI] [Google Scholar]
  34. Wade M. A., and Barkley A. P.. 1992. The economic impacts of a ban on subtherapeutic antibiotics in swine production. Agribusiness 8:93–107. doi: [DOI] [Google Scholar]
  35. Walker N. 1990. The influence of hopper-type feeders on performance of pigs. Pig News Inf. 11:31–33. [Google Scholar]
  36. Walker N. 1991. The effects on performance and behaviour of number of growing pigs per mono-place feeder. Anim. Feed Sci. Technol. 35:3–13. doi: 10.1016/0377-8401(91)90094-9 [DOI] [Google Scholar]
  37. Whittemore C. T. 1998. The science and practice of pig production. 2nd ed. Malden (MA): Blackwell Science Ltd. [Google Scholar]
  38. Wu F., Vierck K. R., DeRouchey J. M., O’Quinn T. G., Tokach M. D., Goodband R. D., Dritz S. S., and Woodworth J. C.. 2017. A review of heavy weight market pigs: status of knowledge and future needs assessment. Transl. Anim. Sci. 1:1–15. doi: 10.2527/tas2016.0004 [DOI] [PMC free article] [PubMed] [Google Scholar]

Articles from Translational Animal Science are provided here courtesy of Oxford University Press

RESOURCES