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Issue Date: 13-Mar-2012
Authors: Valenti, Bernardo
Title: Genetic polymorphism of alpha s1-casein. Feeding strategies to optimize productive performances of dairy goat with different genotype.
Abstract: In literature, the effects of diet and alpha s1-casein genetic polymorphism on the productive performances of dairy goat are discussed separately. Besides to cover a lack of scientific knowledge on this topic, we think that to study the effect of interaction between dietary and genetic factors on milking performances can be of great utility for the development of new feeding strategies for dairy goat. Indeed, the design of specific diets based on the productive potential also for dairy goats can be an economical advantage for the farmers and can reduce the environmental impact of animal breeding. Therefore, the aim of this study was to investigate the impact of different feeding practices on the performances of dairy goats differing in genotype at alpha s1-casein locus. Specifically, we investigated: 1) whether a different genetic aptitude for producing casein can affect diet selection and milk composition in lactating goats, by making available to them feeds with differing chemical nutritive; 2) how goats, selected according to different alpha s1-casein genotype, could reply to diets with different energy levels at similar protein content; 3) the effect of the diet, genotype and diet x genotype interaction on milk fatty acid and casein composition. This research indicates that an interaction between genetic polymorphism of alpha s1-casein and dietary factors occurs, thus affecting the efficiency of nutrient transfer into milk. Our results suggest that in a free choice feeding system goats are able to select a diet according to their genetic aptitude to produce casein. In particular, besides the genotype, the energy requirements were over-satisfied, but goats carrying strong alleles voluntary selected a diet with a higher percentage of energy-rich feeds thus increasing their milk and casein production as compared to goats with weak alleles. For these reason a second trial has been carried out to investigate how goats selected according to different alpha s1-casein genotype could respond to diets with similar protein content and different energy levels. This second trial confirmed that high energy input improves the efficiency of transformation of the diet into milk and casein yield in goats carrying strong alleles, whereas it does not exert noticeable effects in goats carrying weak alleles. As regard fine milk composition, our results suggest that polymorphism at alpha s1-casein locus affect milk fatty acid composition. In particular, in similar feeding conditions, de novo synthesized fatty acids have been found to be higher in the fat of milk of goat with strong alleles. However, this difference tends to be lost when weak alleles goats receive a high energy diet because of an increase of these fatty acids also in the fat of FF goats. Lastly, the study on relative milk casein composition indicates that the higher casein yield and content of goats carrying strong alleles exclusively depends on the biosynthesis rate of alpha s1-casein. Moreover, the lower content of alpha s1-casein in goat with weak alleles seems to be partially compensated by the other caseins in FF goat milk.
Appears in Collections:Area 07 - Scienze agrarie e veterinarie

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