Worm Meal as an Alternative Protein Source in Laying Hen Diets

The nutritional composition of the feed given to laying hens has a direct impact on the quality of the eggs they produce. Chicken eggs are a highly nutritious and economically accessible food source, available in both fresh and processed forms, and widely employed across the food industry. Their affordability and nutritional value, when compared to other animal-derived proteins, position them as a nutritious and cost-effective food choice, playing a pivotal role in addressing issues related to hunger and malnutrition.

The study was carried out over a 69-day period, which was divided into three phases of 23 days each. Thirty-six birds of commercial lineage, all at 50 weeks of age, were employed.Before the study commenced, the animals underwent a 10-day adaptation period. Subsequently, they were divided into groups of 12 birds per treatment. Feed and water were available ad libitum.

To make these measurements, the Eggtester® equipment was utilized in the egg analysis laboratory at the Faculty of Animal Science and Food Engineering (FZEA/USP) located at the Fernando Costa Campus in Pirassununga, USP. Yolk and albumen weights were measured separately using a standard scale, while digital calipers (Mitutoyo®) were employed for determining shell thickness, with an average taken from three equatorial points per egg. The experimental design followed a completely randomized (CRD) approach, with two repetitions for each of the three levels of worm meal in the feed (0%, 2%, and 4%) as partial replacements for soybean meal as a protein source.

The diets were administered daily, specifically formulated to meet the nutritional requirements of the animals in an isoenergetic and isonutritive manner. These diets contained worm meal in proportions of 0%, 2%, and 4%, corresponding to treatments 1, 2, and 3, respectively.

Egg quality data underwent analysis of variance. In cases of significant differences, means were compared using the Tukey test at a significance level of 0.05. Prior to this analysis, normality of residuals was confirmed using the Shapiro-Wilk test, and homogeneity of variances was checked with the Levene test.

When it comes to average egg weight, it was observed that treatment 3 showed a higher weight in comparison to the others. This outcome is attributed to the higher tryptophan content in the diet with 4% inclusion of worm meal, corroborating findings by Harms and Russel (2000).

Concerning egg yolk color, treatment 3 also exhibited a more satisfactory result, explained by the increased corn content in the diet and the higher concentration of tryptophan, which influences this quality parameter, as indicated by Santos et al. (2018). In terms of the Haugh unit (HU), the Quality Control Program, following recommendations by the United States Department of Agriculture (USDA), classifies eggs as:

• Excellent quality (AA): UH values over 72.
• High Quality: UH values between 55 and 72.
• Medium quality: UH values between 30 and 55.
• Low quality:Uh values below 30.

Given this classification, it can be affirmed that despite significant differences between treatments, all levels resulted in eggs with HU values exceeding 88, categorizing them as excellent for consumption.  Analyzing data regarding albumen height and weight across treatments, it can be concluded that the inclusion of worm meal in the diet did not yield significant advantages in these parameters. This is in contrast to yolk weight, which increased in the treatments with worm meal. This increase can be attributed to the enhanced availability of amino acids that phosphorylate with phosvitin, which constitutes the granular portion of the yolk, as explained by Macari et al. (2013). Regarding external egg quality, the inclusion of worm meal in the diets did not affect shell strength. However, assessment of shell weight and thickness revealed values higher than those obtained with the control diet when worm meal was added. This observation can be attributed to the solubility of calcium (Ca) present in worm meal, which, being of organic origin, boasts higher bioavailability and intestinal absorption, as it has a strong correlation with mineral solubility, as noted by Melo et al. (2006).

The partial substitution of soybean meal with worm meal resulted in improved indices related to egg weight, yolk color, yolk weight, shell thickness, and shell strength.

Source: This article was originally published as  a content in portuguese on nutriNews Brasil