Theme Nutrient requirements

Phospholipids (PLs), commonly referred to as lecithin, play an important role in improving fat digestion and nutrient utilisation in animals. Particularly young chickens and piglets that often have insufficient ability to digest and utilise (animal) fat in their diets may benefit with the addition of PLs in their ration.
In this article, we review some of the studies that have been done in pigs and poultry.

Improved fat digestibility in poultry

It is well documented that lecithin supplementation can improve nutrient digestibility, feed intake and performances in poultry (Hertrampf, 1995, 2001; Li and Peisker, 2005). Supplementation with 2% lecithin in the diet containing 4% tallow significantly improved tallow digestibility (70% versus 83%) and dry matter digestibility (Polin, 1980). Wang et al. (2006) found that supplementation of lecithin at 0.5% and 1.0% in broiler diets was beneficial in improving digestibility of dry matter, protein and fat, with more improvements evident in young chicks.

Supplementation of specific PL products to the broiler’s diets containing Metabolisable Energy (ME) levels at 5% less NRC level significantly improved gross energy digestibility by 8.6% and protein digestibility by 4.4%, respectively (Kijpapkorn et al., 2007).

Hetrampf (1995) reviewed the effects of different PL sources supplemented to broiler diets containing either 10% rendered fat or 10-15% tallow. Of 16 treatments, 14 PL treatments resulted in the improvement in fat digestibility by 0.9 to 18.5%, while two crude soy lecithin treatments caused negative responses. The variation could be attributed to the age of the animal, fat type and level, PL type and level, as well as the trial period.

Growth and FCR

Besides an improved dietary fat digestion, PLs have been shown to improve growth and feed conversion rate (FCR) of broilers in more than three-quarters of trials (Hertrampf, 2001). A study was conducted for six weeks where broilers’ diets containing 10% rendered fat was added with either 5% crude soy lecithin, modified lecithin or modified lecithin with 3.0% synthetic emulsifier. Versteegh and Scheele (1986) observed that birds increased body weight by 5.8, 3.7 and 3.7% at two weeks old, and by 2.0, 2.5 and 1.6% at six weeks old, improved FCR by 1.1, 1.1, 0.4% during 0-2 weeks and -0.3, 1.8 and 1.1% during 0-6 weeks, and increased daily ME intake by 3.1, 2.2, 5.0% during 0-2 weeks, and by 1.1, 0.8 and 2.2% during 0-6 weeks, respectively. Improvements owing to lecithin supplementation seem more pronounced in the young chicks than in older ones.

Sebree (2002) showed that lecithin is beneficial in improving growth performances of broilers when used as the fat replacement. Broilers throughout a 39-day grow-out were fed diets containing added tallow (2.5-3.5%) with 0, 25, 50 or 100% soybean lecithin as the replacement. Body weights at day 21 were 0.739, 0.752, 0.751 and 0.757 kg, and final weights at day 39 were 1.99, 2.01, 1.99 and 2.02 kg for 0, 25, 50 and 100% lecithin, respectively. There was a trend (P=0.08) toward higher weights with added lecithin. Birds fed soy lecithin significantly decreased feed consumption, resulting in significant improvements in FCR at day 21 and 39. FCR was 1.487, 1.447, 1.304 and 1.386 during the first 21 days, and 1.921, 1.885, 1.836 and 1.838 during the overall 39 days for 0, 25, 50 and 100% lecithin, respectively. With the addition of de-oiled lecithin at 5 or 10% of added fats, Shrinde (2005) observed that broilers from day 11 to 28 improved final body weight by 2.0 or 4.0%, and FCR by 1.2 or 2.5% when fed 2.5~3.5% palm oil diets, and improved final body weight by 5.9 and 8.3%, and FCR by 4.3 and 7.4% when fed 2.5~3.5% beef tallow diets, respectively. Recently, Kijpapkorn et al. (2007) reported effects of a specific PL product on growth performances and nutrient utilisation of broilers fed diets containing ME levels at 3 or 5% less than NRC level. Low ME diets adversely affected feed efficiency of broilers reared in tropical areas, but supplementation of the PL product helped to restore and spare the energy used to enhance feed intake and reduce FCR. The better feed efficiency resulted from higher digestibility of gross energy and crude protein and better nutrient utilisation.

Effects in laying hens

PLs are also beneficial in improving the performance and health of laying hens. Earlier reports indicated that hens fed either crude or de-oiled soy lecithin significantly improved FCR and tended to improve egg production and mass (Hertrampf, 1995). An et al. (1997) reported that liver triglyceride levels were 27.79, 9.31, 5.32 and 4.83 mg/g, when laying hens received diets containing 5% of either tallow, safflower oil and palm oil (8:2), safflower oil and crud safflower lecithin (5:5), or pure safflower lecithin for seven weeks, respectively. These results indicate that PLs are more effective in reducing the liver triglyceride level than unsaturated fatty acids. Soya PLs can reduce the activities of fatty acid synthesis related enzymes (Kabir and Ide, 1995), which means that PLs are a valued ingredient for laying hens to reduce triglyceride level and to prevent fatty liver syndrome.

Nutritional benefits in pigs

Jones et al. (1992) fed weanling piglets (17-21 days old, 5.3-5.8 kg) with diets containing either 10% soybean oil, coconut oil, tallow or lard as energy source with and without supplementation of lecithin or lysolecithin at 10% of added fats. They reported that supplementation of lecithin significantly improved fat digestibility in diets containing soybean oil by 3.5% and tallow by 9.3%, but had no effect in diets containing lard and coconut oil. Reis de Souza et al. (1995) applied 1.5% lecithin to replace 1.5% tallow in the diet containing 8% tallow and found 7.6% improvement in apparent faecal digestibility of total dietary fat. The addition of lecithin significantly improved apparent ileal digestibility of linoleic and linolenic acids. Similarly, lecithin exerted a beneficial effect on apparent digestibility of unsaturated fatty acids (Soares and Lopez-Bote, 2002) and total long chain saturated fatty acids, as well as total medium chain fatty acids (Jones et al.,1992) during the first two weeks after weaning.

The substance and level of supplemental PLs exert different effects on nutrient utilisation. Jones et al. (1992) reported that fat digestibility of tallowsupplemented diets were significantly improved (9.3%) owing to lecithin addition and lysolecithin addition (3.7%). As compared with lysolecithin, lecithin was more effective in improving digestibility of total fat, unsaturated and saturated fatty acids, medium-chain fatty acids, dry matter, nitrogen and gross energy in weaning piglets. The addition of more than 5% of the fat as lecithin and lysolecithin to diets containing tallow tended not to bring more benefits in nutrient digestibility. Similarly, Xing et al. (2004) observed that supplementation of 0.02% of lysolecithin (but not 0.10%) to nursery piglets fed diets containing 5% lard, tended to improve digestibility of dry matter, fat, gross energy and protein when measured on day 10 post-weaning. However, results regarding the effect of supplemental PLs on nutrient utilisation can be variable. Øverland et al. (1993) reported that, as compared with a diet without lecithin supplementation, the addition of 2% lecithin improved faecal fat digestibility and nitrogen retention, but did not improve digestibility of dry matter, gross energy and nitrogen. There was no clear effect of soy lecithin on the utilisation of added soybean oil in weanling piglets. Soy lecithin did not improve digestibility and utilisation of rendered fat containing mainly lard in cereal-soybean meal basal diets fed to weanling pigs (Øverland and Sundstøl, 1995) and to growing-finishing pigs (Øverland et al., 1994), and also did not significantly improve digestibility of dry matter, crude protein, fibre, calcium and phosphorus

in piglets fed diets containing lard, soybean oil or a blend of both (Soares and Lopez-Bote, 2002). The above inconsistent results are probably owing to various origins of added fats.

Improved ADG

Improved performances in pigs due to supplemental PLs are most likely attributable to better nutrient digestion and feed efficiency. However, animal age, fat type and level, and PL type and level also have an effect. By supplementing 5% lecithin of added fats to a diet containing 10% tallow, Jones et al. (1992) found significant improvements of average daily gain (ADG) by 6.9%, feed intake by 3.5%, and FCR by 3.1% in 21-day-old weaned piglets during the first two weeks post-weaning, but did not observe distinct effects on performances in the 3-5 weeks post- weaning. The addition of more than 5% of the fat as lecithin and lysolecithin tended to decreased growth performance of post-weaning piglets. Soy lecithin added to postweaning piglet diets as an emulsifier of 6% rendered fat significantly improved gain/feed and gain/ME during the first two weeks after weaning, and ADG and gain/feed during overall 35 days after weaning (Øverland and Sundstøl, 1995).

Gunther (1992) evaluated the effects of de-oiled lecithin to the diets containing 2.5% added fats and 1.1% lysine on performances of 21-day-old weanling piglets in a 42 day experiment. Supplementation at 0, 0.2, 0.4 or 0.6% de-oiled lecithin resulted in linear improvements in ADG (470, 515, 534 and 550 gramme), FCR (1.74, 1.61, 1.55 and 1.53) and nitrogen utilisation 39.65, 44.60, 47.20 and 47.80%). These results suggested that weanling piglets need at least 0.2% de-oiled lecithin for better growth and feed efficiency.

Supplementation of lysolecithin to diets containing 5% lard resulted in a linear improvement in ADG of nursery piglets during day 15-35 post-weaning, but did not affect average daily feed intake (ADFI) and FCR (Xing et al., 2004). Final body weight was significantly increased by 10.1% and 12.6% when lysolecithin was supplemented at 0.02% and 0.10%, respectively. However, a few reports indicate no benefits owing to lecithin supplementation. Øverland et al. (1993) reported that the addition of lecithin as an emulsifier or energy source did not improve ADG and ADFI, but may improve gain/feed. Soares and Lopez-Bot (2002) did not observe effects of dietary lecithin on ADG, ADFI and FCR of piglets fed diets containing lard, soybean oil or a blend of both during the first two weeks after weaning and the following two weeks.

Practical recommendation

The richest plant source of PLs is crude soy lecithin, which is obtained from lecithin gums after soybean oil extraction. De-oiled lecithin or specific lecithin can be produced by further refined or modified crude soy lecithin. PLs are recommended to be supplemented at 5-10% of supplemental fats (Russett, 2002). When feed fats are enriched with pure PLs (de-oiled soy lecithin), energy concentration can be enhanced, depending on fat types. Based on the current understanding and added fat dosage in typical feeds for pigs and poultry in Asian countries, it is recommended that supplementation of 1-4 kg/mt feed of poultry and pigs could be beneficial in improving nutrient utilisation and performances (Table 1). According to these recommendations, nutritionists can adjust the formula specification in order to save on feed costs while maintaining animal performance. The apparent metabolic energy and/or digestible energy concentration, crude protein and fat levels can be reduced, individually or in combination, by 2-3%, 2-3% or by 5-10%, respectively.

Conclusion

Dietary supplementation of PLs has proven to be effective in improving fat digestion and nutrient utilisation, and consequently in improving growth performance, particularly in broilers and weaning piglets. Discrepancy in the responses of animals to added PLs is most likely attributed to differences in ages of animals, dietary fat type and level, compositions and levels of added PLs, dietary compositions and nutrient levels. PLs are recommended to be supplemented into feeds for young piglets and chicks, containing a higher level of feed fats/oils, as well as a higher level of saturated fats.

References are available on request.

This information was taken from a presentation at the 15th Annual American Soybean Association International Marketing Southeast Asian Feed Technology and Nutritional Workshop in 2007.

About the Author:
Dr Yuyun Mu received his Masters qualification from Nanjing Agricultural University, China, in 1988, and a PhD from the National University of Singapore in 1999. He served as the academic staff and deputy department head in Anhui Agricultural University, China between 1988 and 1996. Mu has also participated in five research grants funded by the Chinese Government and Singapore Science and Technology Board. Today he is the key investigator of Application Research Project sponsored by Singapore Economic Development Board and has published 10 peer-reviewed journal papers and written more than 50 technical papers and conference proceedings in English and Chinese. He is currently senior technical manager of Berg + Schmidt Asia Pte Ltd., Singapore.