Performance and Egg Quality of Laying Hens Fed Diets Containing Raw, Hydrobarothermally-Treated and Fermented Rapeseed Cake

SIMPLE SUMMARY: Rapeseed cake (RC) has recently gained increasing interest as a dietary protein source alternative to soybean meal (SBM). However, its wider use in poultry diets (including laying hen diets) is limited due to the high concentrations of antinutritional compounds. Technological processes such as thermal treatment and fermentation may improve the nutritional value of RC by reducing the content of non-starch polysaccharides (NSPs), glucosinolates (GLS) and phytate phosphorus (PP). The present study revealed that the inclusion of 20% RC in layer diets improves the fatty acid (FA) profile of egg yolks while maintaining a desirable redox status. Hydrobarothermally-treated RC (HRC) and fermented RC (FRC) exerted a greater beneficial influence on the laying performance of hens than raw RC (RRC). FCR appears to be the optimal substitute for SBM because it contributed to the highest albumen quality and the highest sensory quality of eggs. ABSTRACT: The present study was conducted to investigate how raw rapeseed cake (RRC), hydrobarothermally-treated rapeseed cake (HRC) and fermented rapeseed cake (FRC) fed to laying hens over a period of 12 weeks affected their performance, and the quality, fatty acid (FA) profile and oxidative stability of eggs. A total of 304 Hy-Line Brown laying hens at 36 weeks of age were distributed in a completely randomized design to four treatment groups with 38 replicates per treatment and two hens per replicate. The birds had ad libitum access to feed and water throughout the study. During the experiment, the birds were fed isonitrogenous and isocaloric diets in mash form, with various protein sources. In the control group (C), soybean meal (SBM) was the main source of dietary protein, whereas the experimental groups were fed diets containing 20% of RRC, HRC or FRC. Hydrobarothermal treatment and fermentation decreased the glucosinolate (GLS) content of RC, and fermentation reduced the concentration of phytate phosphorus (PP). In comparison with the RRC group, layers from the HRC and FRC groups were characterized by higher laying performance, comparable with that in group C. Irrespective of its physical form, RC added to layer diets adversely affected eggshell quality in all experimental groups, whereas albumen quality was highest in the FRC group. In comparison with group C, diets containing RRC, HRC and HRC led to a significant decrease in the content of saturated fatty acids (SFAs), an increase in the proportion of n-3 and n-6 polyunsaturated fatty acids (PUFAs) in the total FA pool in egg yolks, and a decrease in the n-6/n-3 PUFA ratio. The inclusion of RRC, HRC and FRC in layer diets decreased the activity of superoxide dismutase (SOD) in egg yolks, relative to group C. Group FCR eggs were characterized by the highest activity of catalase (CAT) and the lowest lipid peroxides LOOH concentration, compared with the remaining groups. The addition of RC to layer diets did not compromise the sensory quality of eggs, and eggs produced in group FRC received the highest overall score. It can be concluded that the inclusion of 20% RRC, HRC and FRC in layer diets does not compromise the sensory quality of eggs and has a beneficial influence on the FA profile and antioxidant potential of egg yolks. The use of FRC is recommended because it contributes to the highest laying performance, superior albumen quality and the highest sensory quality of eggs, relative to RRC and HRC.