The effect of feeding systems on the characteristics of products from small ruminants. (Special Issue: Products from small ruminants.)

摘要

Small ruminants are the most efficient transformers of low quality forage into high quality animal products with distinguished chemical composition and organoleptic characteristics. There is a wide range of sheep and goat farming systems from highly extensive, based on natural grasslands or rangelands, to very intensive ones, based on natural grazing and supplementary feeding. Usually, the systems which are under comparison are those based mainly on pasture vs. the indoor ones. The aim of this paper is to provide an integrated analysis of the major aspects of the nature and composition of small ruminants products, such as milk and meat, and then the effect of feeding systems on chemical composition and quality characteristics of those products (i.e. fatty acid profile, antioxidants, vitamins, muscle:fat ratio, flavour, taste, etc.), since milk and meat quality is constantly evolving, partly in response to the rising concerns of consumers in terms of safety, health, ethical aspects, origin etc. As small ruminants milk is mostly transformed into cheese and its yield depends on milk composition, the main objectives of the dairy sheep and goat breeders are to improve milk quality by increasing the total milk solids output and stabilizing the milk composition (fat and protein) through the appropriate level of nutrition. Factors such as forage:concentrate ratio, dietary fat supplements, pasture, etc. have essential effect on small ruminants milk yield, milk composition and fatty acid (FA) profile. A number of studies have shown that milk from sheep and goats in pasture is enriched in substances of natural origin like phenolic compounds, fat soluble vitamins, flavours terpenes, bioactive lipid components, unsaturated FA and CLA, in addition to being naturally high in medium-chain FA in comparison to those fed conventional concentrate-forage diets. However, there are species differences between sheep and goats as the dietary effects on those parameters concerns, which could be explained by the differences found in mRNA of stearoyl-CoA desaturase of their mammary adipocytes. The feeding system effects on meat quality is more difficult to be identified because lambs and kids of different breed, weaned at different age and live weight or raised on different types of pastures have different growth rate and carcass characteristics like level of fatness, FA profile, flavour, tenderness, taste, etc. It has been demonstrated that lambs and kids raised under a grazing system without any supplementation, present an inferior fatness degree and a higher meat fat concentration of n-3 PUFA and CLA. Lamb meat has higher fat content, higher proportions of SFA and lower MUFA compared to goats, under similar dietary treatment, which make goat meat especially valuable nutritionally and for consumer health. In conclusion, the existing unfavourable properties of small ruminant products can be improved by nutritional intervention to modify their FA profile for the consumer's health benefit.Digital Object Identifier http://dx.doi.org/10.1016/j.smallrumres.2011.09.034