Search

The rapid development of aquaculture, in last decade, has made this sector one of the most important both at economic and social level gaining a main role in human nutrition, but this industry is severely limited by the lack of proteins intended for animal feed (as a competitor of human nutrition) (Wang et al. 2015). Fishery and aquaculture by-products can be considered as promising alternative feed ingredients in terms of nutritional quality and availability; however, these products are still underused resulting in economic and environmental issues (Gasco et al. 2020). At the same time, limiting the use of soy in fish diets has become necessary for the sustainability of aquaculture production. In past years, due to emerging health concern, gluten meal has become an even more significant cereal by-product of agriculture that is spreading thanks to its high protein content (Tapia-Hernández et al. 2019). The effects of total replacement of wild fish meal, (FM) fishoil (FO) and soy product (SP) by using fishery and aquaculture by-products and gluten were tested on the growth, gut health and fish quality parameters of European seabass.

The aim of the study was to quantify the effects of composite β- and κ-casein (CN) genotypes on genetic variation of milk coagulation properties (MCP); milk yield; fat, protein, and CN contents; somatic cell score; pH; and titratable acidity (TA) in 1,042 Italian HolsteinFriesian cows. Milk coagulation properties were defined as rennet coagulation time (RCT) and curd firmness (a30). Variance components were estimated using 2 animal models: model 1 included herd, days in milk, and parity as fixed effects and animal and residual as random effects, and model 2 was model 1 with the addition of composite β- and κ-CN genotype as a fixed effect. Genetic correlations between RCT and a30 and between these traits and milk production traits were obtained with bivariate analyses, based on the same models. The inclusion of casein genotypes led to a decrease of 47, 68, 18, and 23% in the genetic variance for RCT, a30, pH, and TA, respectively, and less than 6% for other traits. Heritability of RCT and a30 decreased from 0.248 to 0.143 and from 0.123 to 0.043, respectively. A moderate reduction was found for pH and TA, whereas negligible changes were detected for other milk traits. Estimates of genetic correlations were comparable between the 2 models. Results show that composite β- and κ-CN genotypes are important for RCT and a30 but cannot replace the recording of MCP themselves. The improvement of milk coagulation properties (MCP) is a hot topic in dairy cattle genetics, mainly because the amount of milk used for manufacturing cheese is growing worldwide (Schmit and Kaiser, 2006) and several studies have confirmed the role of MCP