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Interaction Between Pig Density and Dietary Energy on Performance and Returns

07 May 2015

There were no interactions between dietary energy concentration and the stocking density of pigs from 75 to 118kg. That is one of the main conclusions of this work by G. Rozeboom, D.A. Gillis, M. Young and A.D. Beaulieu reported in the Prairie Swine Research Centre Annual Report 2013-14.

Summary

Prairie Swine Centre Canada
Dr Denise Beaulieu

Dietary net energy and stocking density independently affect performance, feed utilisation and profits in the finisher barn.

The objective of this experiment was to assess the interactions of stocking density and dietary energy, and determine how these interactions affect net income.

When stocking density was increased, the performance of finishing pigs was reduced; however the income over feed cost (IOFC) was maximised when pigs were stocked at higher densities.

Furthermore, finishing pigs responded to increasing dietary energy by decreasing feed intake and improving growth rate, feed efficiency, caloric intake, caloric efficiency and IOFC.

However, the dietary energy which maximised performance and economics did not vary with stocking density.

Thus, producers should optimise both of these factors separately when determining optimal production.

Prairie Swine Centre
Garrett Rozeboom

Introduction

Stocking density and dietary net energy concentration independently affect performance and feed utilisation of growing finishing pigs. There is limited information however, on whether the interaction of these two factors is important for optimising performance and income.

This information is vital to producers facing new requirements for the Canadian Code of Practice on stocking density.

Reduced space allowance has negative effects on growth, and is usually a consequence of reduced nutrient intake. The authors hypothesised that the negative effects of crowding can be reduced by increasing dietary energy concentration, and that the optimal dietary energy concentration which maximises net income will depend on stocking density.

Pork producers will be able to improve their return on investment by better understanding the relationship between dietary energy and stocking density.

Experimental Procedure

There was a total of 18 treatments arranged as a 2×3×3 factorial, which included gender (barrows and gilts), dietary energy (2.15, 2.30 and 2.45Mcal NE per kg) and stocking density (14, 17 or 20 pigs per pen providing 0.92, 0.76 and 0.65 square metres per pig, respectively).

Each of the 18 treatments had three replications, using a total of 918 pigs (Camborough Plus dam × line 337 sire PIC Canada Ltd.; Winnipeg, MB).

Rooms were fully slatted, and consisted of 10 rectangular pens measuring 4.8 metres × 2.7 metres. Each pen contained two single space wet-dry feeders providing 0.22 square metres of feeder space per pen, and the feeders were the only source of water.

Pigs were selected to ensure typical barn variation and were started on test at an average of 75kg bodyweight (range of 60 to 90kg bodyweight). They were marketed weekly when they reached a bodyweight of 115kg.

The diets used for this experiment are presented in Table 1. Four sets of diets, with three dietary energy levels within each diet, were used. Diet sets 1 through 3 were fed as the three phases for gilt and diets 2 through 4 were used as the three phases for barrows. All diets were formulated to meet or exceed nutrient requirements (NRC, 2012). Feed was available ad libitum but weighed daily when added to the feeder.

Table 1. Ingredient and nutrient composition of the diets formulated to contain 2.15 and 2.45Mcal of NE per kg fed to both genders in this experiment.
The 2.30 concentration was the intermediate (as-fed basis)1,2
Diet phase:1234
Gilts:75-90kg90-105kg105-118kg 
Barrows: 75-90kg90-105kg105-118kg
Dietary Net Energy (Mcal/kg):2.152.452.152.452.152.452.152.45
Barley 48.83 5.79 54.84 30.36 66.55 50.27 68.80 61.81
Wheat - 50.06 - 28.66 - 18.64 2.94 15.00
Millrun wheat 20.00 20.00 20.00 20.00 14.41 15.00 5.00 10.00
Peas 18.97 18.66 14.47 15.00 7.70 10.00 6.65 7.33
Oat hulls 7.37 - 7.89 - 8.53 - 13.08 -
Canola meal 2.00 - - - - - - -
Limestone 0.91 1.08 0.86 0.99 0.83 0.95 0.70 0.88
Tallow 0.50 2.80 0.50 3.41 0.50 3.57 1.37 3.45
L-tryptophan 98% 0.01 - - - - - - -
Lysine HCl 78% 0.19 0.32 0.21 0.30 0.26 0.31 0.25 0.30
L-threonine 98% 0.08 0.12 0.09 0.12 0.10 0.12 0.10 0.11
DL-methionine 98% 0.03 0.05 0.02 0.04 0.01 0.03 - 0.01
Calculated composition:
ME, Mcal/kg 2.95 3.24 2.93 3.24 2.91 3.22 2.90 3.21
SID lysine g/Mcal of NE 3.23 3.23 2.97 2.97 2.73 2.73 2.52 2.52
Ca, % 0.50 0.60 0.56 0.56 0.53 0.53 0.50 0.50
P, % 0.25 0.25 0.24 0.24 0.23 0.23 0.23 0.23
1 All diets were formulated to meet requirements for pigs of each phase (NRC 2012)
2 Contain the same amount of vitamin, mineral, choline, salt and Ronozyme (phytase)

Space allowance was calculated by using an allometric equation:

k = A ÷ BW0.667

where 'A' represents area (square metres), k is a space allowance coefficient and BW0.667 is the metabolic bodyweight.

The k-value of 0.0336 was used to define crowding (Table 2), which occurred at about 85 and 108kg bodyweight with 20 and 17 pigs per pen, respectively.

Table 2. Space allowance and k-value for each stocking density at various weights
throughout the finishing period (75-118kg bodyweight; crowding defined as a k-value<0.0336)
Stocking density (pigs/pen):141720
Area per pig (m2):0.930.760.65
75kg bodyweight 0.0520 0.0428 0.0364
85kg 0.0478 0.0394 0.0335
108kg 0.0405 0.0334 0.0284
118kg 0.0384 0.0316 0.0269

Results and Discussion

As dietary energy increased feed intake was reduced, caloric intake increased, growth rate was increased, and feed efficiency improved (Table 3).

Stocking 14 pigs per pen did not improve pig performance when compared to the pen of 17, presumably due to minimal crowding in the pen of 17. However, feed intake and average daily gain were reduced when stocking density was increased to 20 pigs per pen.

Table 3. Main effects of stocking density and dietary energy concentration on ADG, ADFI, G:F, caloric intake and caloric efficiency from 75 to 118kg bodyweight1,2,3
 Stocking density (pigs/pen; NP)Diet regimes: dietary NE (Mcal/kg) P-value4
 141720LowMediumHighSEMSDNE
Average daily feed intake (ADFI), kg5 4.00 a 3.97 a 3.82 b 4.09 a 3.92 b 3.77 c 0.08 <0.001 <0.001
Average daily gain (ADG), kg6 1.21 a 1.21 a 1.17 b 1.17 a 1.21 b 1.23 b 0.03 0.05 0.005
Gain:feed ratio (G:F)7 0.30 0.31 0.31 0.29 a 0.31 b 0.33 c 0.004 0.61 <0.001
Caloric intake Mcal/day5 9.19 a 9.12 a 8.12 b 8.81 a 9.02 b 9.29 c 0.17 <0.001 <0.001
Caloric efficiency, Mcal:Gain 7.59 7.52 7.52 7.54 7.49 7.59 0.09 0.69 0.63
abc Within a row and treatment, means without a common letter differ (P<0.05)
1 Data presented on an as-fed basis
2 Quadratic contrasts were not significant
3 Dietary energy × stocking density (P>0.10)
4 P-values: SD = stocking density; NE = dietary net energy
5 Gender × stocking density (P<0.10)
6 Gender × dietary energy (P<0.05)
7 Gender × dietary energy (P<0.10)

Feeding the high-energy diet reduced days to market (75 to 118kg bodyweight) and increased barn throughput by 1.6 per cent (Table 4).

Despite the improvement in feed efficiency, feed costs were 11 per cent higher with the high-energy diet. There was no effect of dietary energy on carcass margin per pig. The improvement in barn throughput resulted in a tendency for increased income over feed cost (IOFC) with the high-energy diets.

Table 4. Main effects dietary energy concentration and pen density on barn throughput, carcass revenue, feed cost and IOFC1,2,3
 Stocking density (pigs/pen; NP)Diet regimes: dietary NE (Mcal/kg) P-value3
 141720LowMediumHighSEMSDNE
Days to market4 35.4 a 36.0 ab 37.0 b 36.9 a 36.0 ab 35.5 b 1.3 0.03 0.06
Finisher rotations5 3.47 a 3.45 ab 3.41 b 3.42 a 3.45 ab 3.47 b 0.41 0.03 0.05
Barn throughput6,7 48.5 a 58.6 b 68.3 c 58.0 a 58.5 ab 58.9 b 0.7 <0.001 0.02
Carcass revenue per pig8 134.33 135.36 133.08 133.08 a 134.35 ab 136.10 b 1.39 0.50 0.08
Feed cost per pig, C$7 30.66 30.91 30.71 29.85 a 30.57 a 31.86 b 1.04 0.86 <0.001
Feed cost per kg gained, C$9,12 0.73 0.72 0.72 0.70 a 0.72 a 0.75 b 0.01 0.82 <0.001
Feed cost per pig and day, C$10,13 0.87a 0.86 a 0.83 b 0.81 a 0.85 b 0.90 c 0.02 0.002 <0.001
Feed cost per pen, C$4 429.48a 525.49 b 614.14 b 508.70 a 520.31 a 540.11 b 16.76 <0.001 <0.001
Carcass margin per pig, C$ 103.40 104.19 102.89 102.98 103.50 104.01 1.58 0.67 0.78
IOFC, C$11,12 5,012.50 a 6,102.50 b 7,015.90 c 5,950.83 6,052.26 6,127.81 141.37 <0.001 0.22
abc Within a row and treatment, means without a common letter differ (p<0.05)
1 Dietary energy × stocking density (P>0.10)
2 Feed prices based on Saskatoon, SK 5-year average grain prices (2009-2013)
3 P-values: SD = stocking density; NE = dietary net energy
4 Days to market from 75 to 118kg bodyweight
5 Finisher rotations = 365/(days to market +(70 day constant for all treatments 20-75kg bodyweight)
6 Barn throughput = finisher rotations &times pigs per pen
7 Value calculated from 75kg to market wt.
8 Carcass revenue based on a 5-year average Saskatchewan carcass price (2009-2013)
9 Feed cost per kg gained = F:G × cost per tonne
10 Feed cost per pig per day = ADFI × cost per tonne
11 IOFC = annual income over feed cost based on carcass value and barn throughput (75-118kg bodyweight)
12 Gender × Energy (P<0.10)
13 Gender × Energy (P<0.05)

On a per-pig basis, the pen of 20 had the lowest feed cost per day but required 1.6 more days to reach market weight (118kg bodyweight) and there was no difference in total feed cost to reach market weight. Barn throughput increased by 40 per cent when stocking density increased from 14 to 20 pigs per pen. There was no effect of stocking density on carcass value. The increase in barn throughput and no difference in feed cost to reach market weight, resulted in stocking density being the most important factor in determining IOFC.

As stocking density increased, there was a linear improvement in IOFC (Table 4). There was no statistically significant interaction effect on IOFC because the response to dietary energy was similar across all stocking densities. However, there were numerical differences in the IOFC within stocking densities.

Prairie Swine Centre
Figure 1. The interaction effect of dietary energy and stocking density effects on IOFC (C$) in pigs weighing 75 to 118kg. (Interaction was not significant; P>0.10)

Figure 1 shows the interaction effects on IOFC. Stocking density of 20 pigs per pen and feeding the 2.30Mcal NE per kg resulted in the highest IOFC. However, this increase in IOFC was only C$70 higher per pen than the pigs fed the high-energy diet. Pigs housed 20 per pen and fed the low-energy diet had an IOFC that was $700 lower per pen than the pigs fed the high-energy diet. In the pens that housed 17 pigs, IOFC of the high-energy diet was C$472 and C$319 more than the pens fed the low- and medium-energy diets, respectively. Increasing dietary energy for pigs housed 14 per pen resulted in no IOFC improvement; all pens had an IOFC within C$40 of each other.

Conclusions

As space allowance decreased, a linear reduction in caloric intake and growth was observed. The restriction in nutrient intake resulted in the growth reduction, suggesting that if pigs were able to maintain a comparable caloric intake at higher stocking densities effects on growth would be reduced.

Overall, there were no interactions between dietary energy concentration and stocking density.

A similar response to dietary energy at all stocking densities was observed.

The negative effects of a high stocking density on performance were not mitigated by dietary energy. Increasing the stocking density linearly increased the IOFC per pen but there was not an interaction between dietary energy and stocking density. Therefore the dietary energy which maximised the IOFC did not differ with stocking density.

Acknowledgements: Funding for this project was provided by Gowans Feed Consulting and Agriculture and Agri-Food Canada through the Canadian Agriculture Adaptation Program administered by the Agriculture and Food Council of Alberta. Program funding provided by Saskatchewan Pork, Saskatchewan Ministry of Agriculture, Manitoba Pork Council, Alberta Pork, and Ontario Pork.

May 2015

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