Introduction

The addition of fat to the diet of weanling pigs has been reported to improve daily gain and feed efficiency, primarily during the later stages of the nursery period. The lack of response to fat supplementation in the early nursery phase may be explained by the low digestibility of fat, particularly when fats of animal origin are used. However, sow milk contains high levels of fat (40% of the dry matter is fat) and the nursing piglet appears to be capable to digest these large amounts of fat. A digestibility coefficient for sow milk fat of 95% has been reported. The fat in sow milk is already in an emulsified form ready for digestion, and therefore we hypothesized that the inability of the weaned pig to digest fat may be related to inefficient emulsification of dietary fat. Studies evaluating the effect of emulsifiers on nursery pig growth performance and nutrient digestibility have reported inconsistent results. Therefore, the objectives of this research were to: 1) determine the digestibility of fat (lard) in diets supplemented with lysolecithin compared to control diets; 2) determine differences in the digestibility of fat early in the nursery phase compared to the late nursery phase; and 3) evaluate the effect of lysolecithin supplementation on performance of nursery pigs.

Material and Methods

A total of one-hundred and eight pigs were weaned at three weeks of age and allotted to one of 4 dietary treatments based on body weight and litter origin. Treatments were: 1) control with no added fat; 2) control diet with 5% added fat; 3) treatment 2 with 0.02% lysolecithin; and 4) treatment 2 with 0.1% lysolecithin. The lysolecithin added in treatments 3 and 4 replaced an equal amount of the added lard. The basal prestarter and starter diets were formulated using highly digestible ingredients (corn-soybean meal based diets with 20% whey, 4% plasma protein, and 5% fishmeal in the prestarter diets, and 5% whey and 1% fishmeal in the starter diets) and contained 4.7 and 3.8 g of total lysine/Mcal ME for the prestarter and starter diet, respectively. Levels of other amino acids, vitamins and minerals were kept at levels that met or exceeded the requirements for weanling pigs. Prestarter diets were fed immediately after weaning for 2 weeks, followed by the starter diet for 3 weeks. All diets were fed in meal form. Pigs were housed 4 to 5 pigs per pen, using 24 pens (6 replicates per treatment). Pig body weights and feed consumption were measured weekly for the 5 week experimental period.

On day 10 and day 28 of the experiment, fecal grab samples were taken to determine the digestibility of DM, fat, crude protein, P, and gross energy (GE). Samples were taken randomly from at least 2 pigs per pen and pooled by pen. Chromic oxide (0.2%) was used as an indigestible marker in both the prestarter and starter diets to calculate digestibility coefficients.

Data were analyzed as a randomized complete block design using the GLM procedure of SAS (1988). The model included block, sex and treatment. Contrast comparisons were made to determine the effect of fat supplementation versus control and to evaluate linear and quadratic effects of lysolecithin supplementation.

Results and Discussion

During the prestarter phase, digestibility of dry matter (DM; P < 0.10) and crude protein (P < 0.05) appeared to be reduced when fat was added to the diet (Table 1). Digestibility of fat tended to be improved with the addition of 0.02% of lysolecithin, but not with the addition of 0.1% (quadratic effect; P < 0.10). During the starter phase, digestibilities of DM (P < 0.001), fat (P < 0.001), gross energy (GE; P < 0.04), CP (P < 0.001) and phosphorus (P; P < 0.001) were improved with the addition of fat to the diet. Supplementation of lysolecithin linearly decreased the digestibilities of DM (P < 0.003), GE (P < 0.001), CP (P < 0.001), and P (P < 0.001) during the starter phase.

Daily gain (ADG) during the prestarter phase was not affected by dietary treatments (Table 2). However, during the starter period and overall, ADG was reduced (P < 0.05) when fat was included in the diet. The effect of fat supplementation on ADG appeared to be directly related to a reduction (P < 0.10) in feed intake during these periods. The intake of lysine or ME, on the other hand, was not different among treatments (data not shown). Supplementation of lysolecithin resulted in a linear (P < 0.05) improvement in ADG. Feed intake and feed efficiency were not affected by lysolecithin supplementation.

Conclusion