Effects of Emulsification on Amino Acid and Lipid Digestibility in Finishing Pigs

L.A. Averette, M.T. See, and J. Odle


North Carolina State University Swine Nutrition Research from 2001. The reduction of lysine in the diet of the growing pig by 8-10% could have significant impacts on total feed costs in the swine industry. Dietary lysine could potentially be reduced through the addition of lysolecithin. It was hypothesized that the emulsifier would improve homogenization of the ingesta resulting in enhanced digestibility of water-soluble nutrients and improve pig growth performance.




Diets high in unsaturated fat result in soft carcass fat depots, which may be sub-optimal for subsequent pork processing, especially in lean genotype pigs. Increasing the saturated fatty acid content of added dietary fat can improve pork quality, provided the fat is adequately digestible. In North Carolina, saturated fats are not currently available in large volumes or at competitive prices. Rendered lard (iodine value » 80) tends to be recycled in the North Carolina swine industry by inclusion in the diets of finishing pigs. This does benefit the state by reducing costs related to grain importation by providing an alternate energy source. However, it has a negative impact on pork quality. Lean genotype pigs fed diets high in unsaturated fat may result in thinner lower quality bellies with a soft fat composition.


Since the fatty acid content of pork carcasses is reflective of the relative contribution of each dietary fat source, increasing the saturated fatty acid content of the diet can improve the saturated fatty acid content of the carcass. We have shown that chemically hydrogenated fat can improve belly thickness (Averette et al., 1999a). Hydrogenated fat has also been shown to be a similarly digestible fat source when compared to choice white grease (Averette et al., 1999b). If the digestibility of that supplemented fat source was improved by emulsifier addition, further improvements in pork quality may lead to reduced loss during the slaughter and processing procedures.


Materials and Methods


Effects of emulsifier addition (Lysoforte PC, Kemin Industries, Inc.) to diets formulated with 8% supplemental partially hydrogenated fat (IV 50) on growth performance, feed intake and lipid digestibility were evaluated. Thirty-two gilts (avg. wt. 70 kg) were randomly allotted to one of four dietary treatments (Table 1). Diets were formulated to contain either 100 or 80% of the amino acid requirements and 3265 kcal/kg ME. Table 2 shows the results of Kjeldahl Nitrogen analysis of the diets. Emulsifier treatments consisted of 0.1% lysolecithin (Lysoforte, PC) and no emulsifier addition. After a oneweek acclimation period, chromic oxide was added to the diets at 0.1%. The diet containing the marker was provided for 6 days and then feed and fecal samples were collected over a 3d period. Pig weight and feed intake were measured at the end of the 21d study to determine ADFI, ADG, and G/F.


Table 1. Diet Composition

Ingredient, % 100% A.A. + lysoforte 100% A.A. – lysoforte 80% A.A. + lysoforte 80% A.A. – lysoforte
Corn 78.975 79.075 84.575 84.675
SBM 48% 13.3 13.3 7.7 7.7
Hydrogenated Fat (IV50) 5.0 5.0 5.0 5.0
Dicalcium Phosphate 1.0 1.0 1.1 1.1
Limestone .7 .7 .6 .6
Salt .5 .5 .5 .5
Vitamin/TM Premix .3 .3 .3 .3
Antibiotic .025 .025 .025 .025
Chromic Oxide .1 .1 .1 .1
Emulsifier .1 0 .1 0
Calculated Content
ME, kcal/kg 3564 3564 3562 3562
Lysine, % .7 .7 .56 .56
Calcium, % .55 .55 .55 .55
Phosphorus, total % .50 .50 .50 .50


Table 2. Dietary CP Content*

Protein Level Emulsifier % CP
100% + 14.19
100% 13.65
80% + 11.24
80% 11.77

*N x 6.25


Results and Discussion


Research considering the effects of dietary fat supplementation on protein or amino acid digestibility has yielded varied results. Asplund et al. (1960) showed an increase in CP digestibility with increased dietary fat in pigs weaned at 21d. Other studies suggest that ileal amino acid digestibility in growing-finishing pigs was improved with dietary fat supplementation (Imbeah and Sauer, 1991). We have indirectly considered the effects of supplemental fat on protein digestibility by measuring feed intake and growth over a three-week period. Results are summarized in Table 3. As the amount of dietary protein relative to the requirement was reduced to 80%, there were significant reductions in final weight, total gain, average daily gain, total feed intake and gain to feed ratio (P < .05). Emulsifier addition did not affect feed intake, gain or digestibility (P > .10). A 20% decrease in average daily gain was measured in animals consuming the low protein diet, regardless of level of emulsifier addition. The reduced weight gain was related to the feed consumption. Total feed consumed over the 21d period was reduced by 14.5% in pigs consuming the lower protein diet.


Table 3. Effects of emulsifier addition on pigs receiving either 80 or 100% of their protein requirement

Item + Lysoforte, PC – Lysoforte, PC P-values
80% Protein Requirement 100% Protein Requirement 80% Protein Requirement 100% Protein Requirement Emulsifier Protein Interaction
Final Wt., kg 104.4 ± 2.5 111.6 ± 2.5 106.5 ± 2.4 111.4 ± 2.5 .70 .02 .64
Gain, kg 27.5 ± 2.5 34.6 ± 2.5 29.6 ± 2.4 34.5 ± 2.5 .70 .02 .64
ADG, kg .65 ± .06 .82 ± .06 .70 ± .06 .82 ± .06 .70 .02 .64
FI, kg 88.9 ± 5.4 104.0 ± 5.3 93.5 ± 5.3 100.7 ± 5.4 .91 .05 .46
Gain:Feed .30 ± .01 .33 ± .01 .32 ± .01 .34 ± .01 .28 .01 .94
Fat Dig., % 71.8 ± 2.3 72.4 ± 2.3 73.6 ± 2.3 71.5 ± 2.3 .87 .75 .56


There are no conclusive reports published on the effects of emulsifier addition on amino acid digestibility. Emulsifiers, such as lysolecithin, increase micelle formation in the digestive tract. Lysolecithin has been reported to significantly improve solubilization of long-chain saturated fatty acids in sheep (Andrews, 1966). However, it appears that lysolecithin has a minor role in formation of micelles in the pig (Freeman, et al. 1967). With no impacts of lysolecithin addition on growth or fat digestibility, our research supports this conclusion.


The presence of dietary fat may improve amino acid digestibility through a reduced rate of gastric emptying. This would result in a reduced passage rate in the small intestine, allowing for more time for amino acid absorption, if that were a limiting factor. From our research, we can not conclude that amino acid digestibility was improved due to dietary fat. Control diets containing no supplemental fat are needed to make this comparison.


In conclusion, the 0.1% addition of emulsifier did not increase lipid or amino acid digestibility. However, effects of protein reduction on performance were measured in this study.


Literature Cited

Andrews, R. J. 1966. The utilization of dietary fat in ruminants. PhD. Thesis. University of Nottingham.
Asplund, J. M., R. H. Grummer and P. H. Phillips. 1960. Stabilized white grease and corn oil in the diet of baby pigs. J. Anim. Sci. 19:709.
Averette, L.A., M.T. See and J. Odle. 1999a. Hydrogenated dietary fat improves pork quality of pigs from two lean genotypes. J. Anim. Sci. 77 S(1):52.
Averette, L.A., M.T. See and J. Odle. 1999b. Effects of chemical hydrogenation of dietary fat on apparent lipid digestibility by finishing swine. J. Anim. Sci. 77 S(1):183.
Freeman, C. P., E. F. Annison, D. E. Noakes, and K. J. Hill. 1967. The absorption of micellar fat in pigs. Proc. Nutr. Soc. 26:vii (abstr.).
Imbeah, M. and W. C. Sauer. 1991. The effect of dietary level of fat on amino acid digestibilities in soybean meal and canola meal and on rate of passage in growing pigs. Livest. Prod. Sci. 29:227