Technical Review
Use of egg products in pet food
A technical review of the benefits of egg proteins in pet food
by dr prof Isabelle Kalmar, DVM, Phd
Part 1:
Introduction to feed-grade egg products
Author Dr. ISABELLE KALMAR, DVM, PhD
Egg products comprise a group of high quality ingredients that are widely used in pet food as a source of highly bio-available dietary essential nutrients. A high content of biologically active components in egg products offer extra health benefits in addition to their nutritional value. Their functional properties are furthermore used as a natural processing aid in the manufacture of wet and dry pet food.
The raw material for the production of feed-grade egg products is sourced from by-products of various actors within the egg and poultry production industry. Hens are thus not purpose-bred for the production of such egg products, increasing sustainability of pet food. In order to produce high-quality egg powders, liquid egg fractions are pasteurized and spray-dried to guarantee microbiological safety and to inactivate anti-nutritional factors present in raw eggs. Indeed, eggs are not suitable for raw feeding as this may cause foodborne diseases like salmonellosis (Keerthirathne, 2017). Moreover, consumption of raw eggs can cause egg white injury or biotin deficiency due to the anti-nutritional effect of active avidin, which is a biotin-binding protein present in raw egg white (Bolnave, 1977). An adequate pasteurization or equivalent
alternative processing step is thus of essential importance when using egg-based ingredients in pet food. Thanks to the gentle drying process during spray drying of pasteurized liquid egg, the amino acids do not become heat-damaged through which their bio-availability remains very high. To this respect, Donadelli et al. (2019) showed a much higher lysine availability in spray dried (96-97%) compared to severely heat-treated animal by-products (78-84%). These authors used a broiler chicken growth assay as a model to evaluate nutritional value of novel and traditional pet food ingredients. Lysine availability of spray-dried egg white was 96%. In rainbow trout, protein digestibility of spray-dried versus contact-dried porcine hemoglobin was shown to be 94% and 49.5%, respectively (Kalmar et al., 2020). These studies demonstrate that processing method is of crucial importance to the nutritional value of ingredients.
The composition of eggs depends on the bird species, but can roughly be divided into 60-65% egg white, 25-30% egg yolk and 10% egg shell (Joseph et al., 2002; Faruk et al, 2010).
The major nutritional components in the liquid part of eggs are proteins and fats, while the egg shell largely consists of calcium carbonate. As the fat content of eggs is entirely located within the yolk fraction, different types of egg products can be produced to offer more formulation flexibility to nutritionists. For instance, whole eggs without shell contain 47% protein and 40% fat (Actipro® EP 44). However, egg yolks can be separated from egg whites after which both fractions can be pasteurized and dried separately to produce egg yolk powder (Actipro® EP 30) with 53% fat (36% protein) and egg white powder (Actipro® EP 80) with only 3% fat and 81% protein. Egg powder with increased protein content (eg Actipro® EP 60) contains more albumin proteins. Besides varying proportions of protein and fat, these ingredients are all low-ash animal by-products (Figure 1).
Conclusion
Egg products are sustainable and safe ingredients full of bioavailable nutrients and biologically active components. In addition, they offer interesting functional properties in pet food manufacturing.
Want to read more?
Download the full PDF now
