Spray-dried egg shows potential as an alternative protein source for weaned pigs

Wednesday, August 1, 2012

U.S research suggests that SDE is a valuable nutrient source in nursery pig diets which may provide additional physiological benefits that specifically improve the health of pigs

by JANICE MURPHY

Historically, the post-weaning period has been a focal point for nutrition research since pigs at this stage of production are especially susceptible to disease. This susceptibility is due, in part, to the stress of weaning, an immature immune system and the delicate dietary balance that must be struck to provide nutrients to young pigs with exacting requirements and immature digestive systems.

Despite the price tag, high quality protein sources such as spray-dried plasma, milk powder and fishmeal are typically included in nursery diets to address these issues and maximize growth performance. In particular, spray-dried plasma has proven to be effective at stimulating growth while protecting against disease. However, the price of these protein sources has dramatically increased recently, creating challenges in formulating nursery diets with an eye to the bottom line.

To assess an alternative high quality protein source, researchers at the University of Illinois recently conducted four experiments incorporating spray-dried egg (SDE). The SDE product was sourced from eggs without shells from below the U.S. Department of Agriculture's Grade B standards.

Spray-dried egg contains a large proportion of egg white, which in itself has an excellent amino acid profile with a significant level of methionine, tryptophan and valine compared to other protein sources like soybean meal, fishmeal, dried whey and spray-dried plasma (SDP). The nutrient characteristics of the product suggest it is highly digestible. In addition, SDE contains a high fat content (about 30 per cent) and therefore higher energy content than other protein sources used in nursery diets. (See Table 1.)

Beyond its ability to provide the necessary nutrients, SDE boasts physiologically active compounds such as immunoglobulins and lysozyme, an enzyme with antimicrobial properties (the topic of a recent Better Pork article), which could translate into specific physiological health benefits. With little past evidence in the literature to rely on, the researchers set out to evaluate the nutrient contributions to growth and health benefits of SDE in nursery diets.

In all four experiments, the diets were formulated to the same level of metabolizable energy and lysine, and included antibiotics and zinc oxide. Experiments 1 and 2 (using respectively 168 and 140 16-day-old pigs starting at five kilograms) were conducted at a university farm. Pigs were fed a nursery diet with or without five per cent SDE for 10 days after weaning to measure performance – specifically average daily gain (ADG), average daily feed intake (ADFI) and feed efficiency (G:F).

Experiment 3 (using 1,008 20-day-old pigs starting at 5.2 kilograms) was conducted at a commercial farm. Pigs were fed nursery diets with or without SDE and high or low levels of SDP. Pigs were on trial for six weeks using a four-phase feeding program (phases lasted one, one, two and two weeks, respectively) where the complexity of the diet diminished with each phase. Performance, removal rate (mortality plus morbidity) and frequency of medical treatments were measured during each phase.

Experiment 4 (using 160 21-day-old pigs starting at 6.7 kilograms) was conducted at a university farm to determine whether SDE can replace SDP. Pigs were fed nursery diets with or without SDP or SDE in nursery diets. As in experiment 3, pigs were on trial for six weeks using the same schedule and performance was measured.

In experiments 1 and 2, the SDE significantly increased ADG (Exp. 1: 243 versus 204 g/d; Exp. 2: 204 versus 181 g/d) and ADFI (Exp. 1: 236 versus 204 g/d; Exp. 2: 263 versus 253 g/d) compared with the control diet, but did not have any effect on feed efficiency.

In experiment 3, ADFI increased significantly in pigs fed diets with SDE during Phase 1 only (180 versus 164 g/d) compared with the diets without SDE, but there was no effect on growth performance for the duration of the trial. (See Table 2, page 29.)

The diets with SDE also significantly reduced the frequency of medical treatments during Phase 1 (0.75 versus 1.35 per cent) and tended to reduce treatments overall compared with diets without SDE, but did not affect removal rate. The researchers did note a significant carry-over effect in Phase 4 on ADG and G:F in pigs previously fed diets with SDE.

The observations surrounding medical treatments imply that the presence of specific compounds in SDE may contribute some disease protection. The researchers point out that SDE contains IgY, which is likely to be in the range of 12,000-30,000 mg/kg in egg yolk. A batch of SDE from the supplier for these trials underwent analysis and was reported to contain 11,800 mg IgY/kg. SDE is also known to contain lysozyme, an antimicrobial enzyme that can damage bacterial cell walls and result in cell death. Based on a review of the literature, this is the first experiment to report a practical benefit of SDE on pig health.

In experiment 4, the diets with SDE significantly increased ADFI during only Phase 1 compared with the diets without SDE, but did not affect growth performance at any other phase of the experiment. (See Table 3, page 29.) SDE had a significant negative impact on G:F during Phases 2 and 3, and the overall period compared with diets without the SDE. In Phase 3, this impact tended to be stronger in the presence of SDP than in its absence.

There is a need for further research on this feed ingredient. According to the researchers, it is possible that the benefit from feeding SDE is more likely in the absence of other dietary factors that promote health, like SDP, antibiotics or zinc oxide. However, this is not clearly revealed in this set of experiments, nor in the results of previous research. The resulting decrease in G:F when SDE was fed is consistent with energy or nutrient composition of this product being overestimated, so there is a need to refine the values used in formulating diets.

Based on these results, the researchers concluded that SDE is a valuable nutrient source in nursery pig diets which may provide additional physiological benefits that specifically improve the health of pigs. Spray-dried eggs certainly warrant further investigation. BP

Janice Murphy is a former Ontario agriculture ministry swine nutritionist who now lives and works in Prince Edward Island.

Source: M. Song, T. M. Che, Y. Liu, J. A. Soares, B. G. Harmon and J. E. Pettigrew. 2012. Effects of dietary spray-dried egg on growth performance and health of weaned pigs. J ANIM SCI published online May 14, 2012. http://jas.fass.org/content/early/2012/05/02/jas.2011-4305