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Excess Dietary Crude Protein from Soybean or DDGS in Diets for Finishing Pigs

by 5m Editor
9 June 2009, at 12:00am

Finisher diets with 40 per cent dried distillers grains with solubles (DDGS) decreased growth performance and economically important carcass measurements but the effects were not caused by the high level of crude protein in the diet. These were the conclusions drawn from an experiment by S.M. Williams and co-authors and reported at the Kansas Swine Day 2008.

Summary

A total of 180 pigs (90 barrows and 90 gilts, average initial weight of 148 lb) were used in a 67-day experiment to determine the effects of excess dietary crude protein (CP) on growth performance and carcass measurements in finishing pigs. The pigs were sorted by ancestry and blocked by weight with 12 pigs per pen and five pens per treatment. Treatments were corn-soybean meal-based diets formulated to 15.3 and 18.3 per cent CP and a corn-soybean-DDGS-based diet formulated to 18.3 per cent CP. Feed and water were consumed on an ad libitum basis until the pigs were slaughtered (average final weight of 282 lb) at a commercial abattoir.

Pigs fed diets with high CP had lower (P<0.001) final weight, ADG, ADFI, and HCW but these results were caused entirely by the diet with 40 per cent DDGS.

The results indicated that diets with 40 per cent DDGS decreased growth performance and economically important carcass measurements. However, the excess CP in those diets does not seem to be the culprit.

Introduction

Many scientists (particularly in Europe) suggest that excess crude protein (CP) in diets reduces energetic efficiency in pigs. This lost efficiency should be reflected in poor growth performance measurements. Additionally, excess CP in diets has been blamed for increased organ weights leading to lower carcass yields. These arguments are of particular interest to us because diets with high inclusion of dried distillers grains with solubles (DDGS) have an abundance of CP.

The authors designed an experiment to determine the effects of excess dietary CP from soybean meal versus DDGS on growth performance and carcass measurements of finishing pigs.

Procedures

A total of 180 pigs (90 barrows and 90 gilts, average initial weight of 148 lb) were used in a 67-day growth assay. The pigs were sorted by sex and ancestry, blocked by weight, and assigned to pens. There were 12 pigs per pen and five pens per treatment. The pigs were housed in a finishing facility with 6-foot × 16-foot pens having half solid and half slatted concrete flooring. Each pen had a self-feeder and nipple waterer to allow ad libitum consumption of feed and water until the pigs were slaughtered at an average weight of 282 lb.

The first treatment was a corn-soybean meal-based diet formulated to 15.3 per cent CP with added lysine and threonine (Table 1). For the second treatment, a simple corn-soybean meal-based diet was formulated to 18.5 per cent CP. Finally, a diet with 40 per cent DDGS (Sioux River Ethanol, Hudson, SD) was formulated; that diet also had 18.5 per cent CP.


Table 1. Composition of diets

Pigs and feeders were weighed on days 0, 34 and 67 to allow calculation of average daily gian (ADG), average daily feed intake (ADFI), and feed conversion ratio (F/G). The pigs were killed on day 67 (average weight of 282 lb), and carcass data were collected. Because differences in slaughter weight and, thus, hot carcass weight (HCW) are known to affect carcass measurements, carcass data were analysed without and with HCW used as covariate to remove the effects of slaughtering pigs at a constant age rather than constant weight.

All data were analysed as a randomised complete block design by using the MIXED procedure of SAS. Orthogonal contrasts were used to separate treatment means with comparisons between the control versus high protein treatments and high protein from soybean meal vs. high protein from DDGS.

Results and Discussion


Table 2. Effects of excess dietary CP from soybean mean and dried distillers grains with solubles in diets for finishing pigs1

Pigs fed the 15.3 per cent CP corn-soybean meal-based diet had greater (P<0.03) ADG, ADFI, HCW and dressing percentage than pigs fed the 18.3 per cent CP treatments. The negative effects of the high protein treatments were caused entirely by the low (P<0.001) ADG, ADFI and HCW for pigs fed the DDGS diet compared with pigs fed the high protein corn-soybean meal-based diet.

For further analysis of the results, HCW was used as a covariate to adjust the pigs to the same carcass weight. When this was done, there were no treatment effects (P>0.1) for dressing percentage and percentage carcass lean. However, pigs fed the control diet had greater (P<0.09) fat thickness than pigs fed the high protein treatments. Also, pigs fed the soybean meal treatment had less (P<0.04) backfat than those fed the DDGS diet.

In conclusion, the data demonstrate that pigs fed 15.3 per cent protein had greater ADG, ADFI and HCW than pigs fed the 18.5 per cent protein treatments. However, those negative effects resulted only from addition of 40 per cent DDGS, suggesting that it is not the excess CP causing the negative effects.

Further Reading

- You can view other papers presented at the 2008 Kansas Swine Day by clicking here.


June 2009