|
Descripción
|
|
|---|---|
| Some major conclusions may be drawn starting from the general objectives of the present thesis, that is defining rabbit nutritional needs during post-weaning and fattening with special regards to the different fibrous fractions, mostly the more digestible ones (pectins, hemicelluloses), the starch content in relation to fibre, as well as the dietary protein supply with different aims: 1) improving rabbits intestinal conditions. Changes in main nutrients (digestible fibre, ADF, starch and protein) within the tested intervals may affect the intestinal condition of rabbits and caecum equilibrium: increasing DF at the expenses of starch or increasing protein in diets with appreciable DF supply stimulate caecal fermentation, limit ammonia production and influence caecal pH to a favourable extent for caecal bacterial population. Starch, DF and ADF level, did not affect the morphology and integrity of rabbits intestinal mucosa. 2) reducing the incidence and severity of digestive disorders. The trials were performed under optimal health status. Thus, despite the wide variations in the chemical composition of experimental diets, no effects on animal health were noticed. Therefore, we are not able to adequately evaluate the effect of the tested dietary treatments in a farm stroked by ERE. However, there is evidence that low DF/starch ratio increases mortality and affected animals recover faster. This trend is enhanced if a low DF/starch ratio (<1) in the diet is associated with high dietary protein (>16%), so diets with high DF/starch ratio (1-1.5) and moderate protein level (about 15%) are recommended. By substituting starch with DF, high dietary energy level is maintained and combined with a low flux of undigested protein at caecal level; it may reduce the sanitary risk. 3) increasing feed efficiency and N retention. The increase of dietary DF at the expenses of less digestible fibre fractions or starch (at constant ADF level) improves feed conversion, by reducing feed intake, and allows an appreciable reduction of nitrogen excretion. Starch and digestible fibre may be considered alternative in rabbit feeding and, potentially, additive: the association of high starch and DF level could results in even better results on feed conversion and profitability. 4) guaranteeing high performance and final product quality. Increasing DF/ADF ratio improves diet nutritive value and their efficiency of utilization for growth. Increasing DF/starch does not modify the nutritive value of diets and, in most cases, nor growth performance or slaughter results. Sometimes, growth may be rather stimulated, especially during the first weeks of growth when young rabbits are still developing their digestive capacity. To maximize growth performance, dietary crude protein should not be reduced below 15.5% in the first weeks of growth since the subsequent compensatory growth that rabbits show in fattening period before slaughter does not permit to recover the weight loss. Dietary protein has to be controlled both in the first and especially in the second period of growth, during which protein requirements are lower, to increase N efficiency and limit its excretion. Changes in DF, starch or protein produce significant differences in slaughter results only when capable of modifying slaughter live weight and, therefore, carcass traits directly correlated to live weight. Meat traits, pH and colour, of main muscles never change with the dietary treatment to an extent appreciable form a commercial point of view | |
|
Internacional
|
Si |
|
ISBN
|
|
|
Tipo de Tesis
|
Doctoral |
|
Calificación
|
Sobresaliente cum laude |
|
Fecha
|
|