AN OVERVIEW OF PROTEIN AND AMINO ACID NUTRITION OF THE MINK - A TRUE CARNIVORE

摘要

The objective of this review is to examine the protein and amino acid requirements of the mink in light of the physiological role of the individual amino acids, and elucidate the effects of protein quantity and quality on productivity, fur quality andhealth status of the animals. The mink has a high requirement for dietary protein. Besides essential amino acids, there is a special requirement for the glucogenic amino acids to provide for maintenance of glucose homeostasis. The minimum requirement for dietary protein is 40% of ME during breeding, gestation and lactation, whereas 30% of ME is adequate during the growing-furring period. Methionine is the most limiting amino acid with a requirement of 1.60 g apparent digestible amino acid per Meal Metabolic Energy (ME). This high requirement is due to the need for sulphur groups for cysteine synthesis for the formation of cystine and keratin, the structural protein in hair. Methionine is also a methyl donor for anabolic processes. The mink's requirement for arginine, which is used for the elimination of nitrogen via the urea cycle, is 2.2% in the diet. Gluconeogenesis from amino acid precursors has been estimated to account for ~70% of the blood glucose requirement in the nursing female with a dietary carbohydrate level of 12% of ME. The oxidation rate of amino acids is shown to be higher post-prandially than in the fasted state. During the breeding, gestation and lactation periods the dietary protein supply may be reduced from 61% to 39% of ME witha simultaneous increase in the content of carbohydrates with no negative impact on the growth of kits or the health status of the nursing females. Low level of dietary protein during nursing has been shown to retard early growth of kits, while poor protein quality resulted in inferior growth performance after weaning. Mortality rates and liver lipidosis are increased by feeding of low protein diets as well as poor quality protein in comparison to feeding high levels of good quality protein. Severe protein malnutrition retards the development of the secondary derived hair follicles resulting in reduced winter fur density, whereas a low dietary protein level leads to a reduction in fur growth rate. In summary it appears that a low dietary protein levelis more likely to cause problems related to the productivity and health of the mink whereas reduced quality of the protein primarily hinders optimal fur development.