Effects of fat encapsulation and pelleting

on weanling pig performance and fat digestibility

 

J.J. Xing, D.F. Li

China Agriculture University, Beijing, China

E. van Heugten, J. Odle

North Carolina State University, Department of Animal Science

K.J. Touchette, and J.A. Coalson

Merrick’s, Inc., Middleton, WI.

 

Summary

The objective of this study was to evaluate the effects of encapsulated fat (EF) processed by spray drying on growth and nutrient digestibility in weanling pigs.  Animals (n=144; 6.04±1.12 kg, weaned at 21 d) were allotted to 1 of 6 treatments in a 3 x 2 factorial arrangement with 3 levels/sources of fat (1 or 6% fat from unprocessed lard, or 6% fat from EF) and 2 diet forms (mash vs pellet).  Pigs were fed a 2-phase diet program, with phase 1 diets from d 0-14 and phase 2 diets from d 14-35.  Total-tract digestibilities were computed using Cr₂O₃ as marker.  Fat addition to the diet reduced (P < .05) ADFI from d 0 to 14, with no effect on ADG or G/F.  From d 14 to 28, EF improved ADG ( P < .05) and G/F (P < .01) each by greater than 10%, with no effect on ADFI.  For the entire 35 d trial, fat supplementation decreased ADFI by 6% (P < .05), with no effects on ADG or G/F, while EF did not effect pig performance.  Pelleting improved ADG (P < .01) and G/F (P < .05) during phase 1, with no effect on ADFI.  During phase 2, and overall (d 0-35), pelleting decreased ADFI (P < .06) and improved G/F (P < .01) by 5-8%, with no effect on ADG.  Fat level/source did not affect (P > 0.05) DM or organic matter (OM) digestibility estimates; however, pelleting improved (P<0.001) DM, OM and fat digestibility of all diets.  Fat addition improved fat digestibility compared to 1% lard (P<0.001). Pellet durability index (PDI) was numerically higher (96.2% vs 85.6%) in the EF phase 2 diet compared to the lard diet. In conclusion, the EF improved growth and feed efficiency in weaned pigs, with d 14 to 28 being most beneficial.   EF may improve pellet quality of phase 2 diets containing high levels of fat and low levels of whey.  Additionally, pelleting improved digestibility and feed efficiency during the post-weaning period.

 

Introduction

A number of factors may affect utilization of dietary fat by weaning piglets (Reis de Souza et al., 1995). Among them are physical factors such as size of fat globules, methods of fat incorporation into the diet and other fat processing technologies such as spray-drying, prilling, etc. There are several types of fat products commercially available for supplementation into diets for young animals.  Merrick’s dry fat 7-60 is a spray-dried fat product. Choice-grade lard is combined with milk products in a special spray-drying process causing the milk proteins to encapsulate the fat particles as they dry. The objectives of this experiment were to investigate the effect of spray-dried fat (Merrick’s dry fat 7-60) on the performance of weaning pigs fed diets in pellet or mash form.  We hypothesized that the spray-dried fat would have improved digestibility such that pigs fed this fat would show improved feed efficiency compared with animals fed control (unprocessed) fat.  The reason for examining the effect of pelleting was the concern that heat exposure during preconditioning and pelleting might “melt” the spray-dried fat globules and thus abrogate potential beneficial effects.

 

Materials and Methods

Weaning pigs (n=144; average 21 days old; 6.04±1.12 kg) were used in this trial. The pigs were housed in a nursery facility at the North Carolina State University Swine Educational Unit. A total of 48 pens (3 pigs per pen) were used, giving 8 replications of 6 treatments. Piglets were blocked by weight, sex and litter of origin and were allotted within to one of six dietary treatments based on a 3 x 2 factorial, randomized complete block experimental design:

 

Fat effect (3 levels/sources): 1% lard,

6% unprocessed lard,

6% spray-dried lard

Diet form (2 levels):                 mash form

                                                 pelleted form

 

The feed was pelleted at 60C of conditioning temperature. The pellet size was 1/8”. Pellet durability index is tabulated in table 1.  Pigs were given ad libitum access to feed and water. Dietary treatments were fed in two phases. Pre-starter diets were offered from day 0-14 (Table 2). The starter diets were fed from day 15-35 (Table 3). Diets were formulated with a constant lysine/ME ratio.  Note that the spray-dried fat (80% fat) was included at 8.4% to yield the desired 6% level of fat supplementation.  Pig weight and feed consumption were measured on a weekly basis for 5 weeks. Subsequently, ADG, ADFI, and G/F were determined. Data were analyzed using the GLM procedure of SAS with pen as the experimental unit. Data were analyzed using a 3 X 2 factorial ANOVA model.  Dietary fat effects were further portioned into orthogonal contrasts comparing fat level (1 vs 6%) and fat form (unprocessed vs spray-dried lard).

Table 1. Pellet durability index (PDI) of pelleted feed.

 

Diets	Pre-starter	Starter
1% Lard	97.6%	89.5%
6% Lard	95.2%	85.6%
6% Spray-Dried Fat	95.9%	96.2%

 

Table 2. Prestarter diet composition (fed days 0-14 postweaning).

 

 

Table 3. Starter diet composition (fed days 15-35 post-weaning).

 

 

Results and Discussion

Animal growth performance is summarized in Figures 1-3 and Table 4.

 

pelleting effects

No significant interactions (P > 0.1) between dietary fat and diet form (pellet vs mash) were observed ( 0-14; 14-35 and 0-35 days), although some tendencies were noted. From 0 to 7 days; 7 to 14 days and over the entire pre-starter phase (0-14 days), pelleting significantly and consistently improved the ADG and feed efficiency (P<0.05). However, ADFI was not affected by pelleting. Many researchers attribute the improved performance of pigs fed pelleted diets to decreased feed wastage (Hancock et al, 2001). This hypothesis would be valid in this trial. During each week of the starter phase, no effect of pelleting on ADG was observed, but ADFI and feed efficiency were affected by pelleting. Summarized over the entire experimental data, pelleting did not affect the ADG but did improve feed efficiency (P=0.0047), and tended to decrease ADFI (P=0.1071).

 

In feed processing practice, it is common to add 3-6% fat to diets containing high amounts of milk-based ingredients to enhance pelleting of diets (Maxwell et al, 2001). The pellet durability index (PDI) of the pelleted diets is shown in Table 1.  Notably, the starter-phase diet containing spray-dried fat had up to a 10% higher PDI (96.2%) compared with other diets.  Inclusion of 6% lard in starter diet tended to deteriorate the pellet quality.  From a feed manufacturing perspective, use of the spray-dried fat could help to improve pellet quality -- this might be another advantage of spray-dried fat.

 

Figure 1. Effect of pelleting on piglet starter feed intake during 2-4 wk postweaning (weaned @ 21 d); pellet effect, P<0.05.

 

dietary fat effects

From days 0 to 7, 7 to 14, and 0 to 14 days after weaning (pre-starter feeding phase), dietary inclusion of spray-dried fat had no effect on ADG relative to that of pigs fed 1% lard and 6% lard diets. However, pigs fed spray-dried fat had significant lower ADFI (P=0.0395) compared to pigs fed 1% lard and 6% lard diets. Congruent with our hypothesis, during the pre-starter feeding phase, dietary inclusion of spray-dried fat tended to improve feed efficiency (P=0.0850).  From 14 to 21 day, ADG tended to be greater (P=0.0958) for pigs fed spray-dried fat diet. Similarly, from 21 to 28 day, feed efficiency was improved by the inclusion of spray-dried fat. During the last week of experiment (28 to 35 day), neither ADG nor ADFI, G/F were affected by dietary treatment. However, from 14 to 28 day, both ADG (P=0.0410) and G/F were increased in pigs fed spray-dried diet. This suggests that the response to spray-dried fat is most prominent during 14 to 28 day after weaning at 21 days.  For the entire experimental period (days 0-35 after weaning), no significant effect of diets in ADG was observed. A tendency for lowering feed intake (P=0.1058) and improvement of feed efficiency (P=0.1255) was observed in pigs fed the spray-dried fat diet compared to other diets.

 

Figure 2. Effect of fat source on piglet gain during 2 to 4 weeks postweaning (weaned @ 21 d); lard vs. sd lard, P<0.01.

 

Figure 3. Effect of fat source on growth efficiency during 2 to 4 weeks postweaning (weaned @ 21 d); lard vs. sd lard, P<0.01.

 

Table 4. Performance of weaning pigs fed various fats in pellet or mash diets.¹