What nutrients should be paid attention to in mink feeding?

With the rapid development of mink breeding industry, mink feed resources, especially fishery resources are increasingly scarce, and mink full-price compound feed accounts for more and more proportion in mink breeding. To prepare a good mink feed, mastering the main nutritional requirements of minks is the premise. Now the main nutritional needs of minks are briefly introduced. At present, there are two main feeding standards used in fur animal production: NRC's fur animal feeding standard, which is the minimum requirement for normal growth, reproduction, production and health of animals, excluding safety factor. When formulating the needs of energy and various nutrients, the differences in feed chemical composition, genetic differences of different breeds and the effects of climate and livestock house on the requirements are taken into account. In the study of fur animal nutrition, total energy, digestible energy and metabolic energy were used to express the energy value of feed, but now ME is often used as an index to evaluate the effective energy value of feed. The ME value of feed was estimated according to digestible protein, digestible fat and digestible carbohydrate of feed. NRC and Enggarrd-Hansen adopted the same formula: ME (kJ/g) = 18.8DCP + 39.8DEE + 17.6DCAB. The energy requirement (MEM) for maintenance of fur animals depends on factors such as body weight, activity and ambient temperature. The study found that fur animals need much more energy to maintain than other livestock. The energy needed to regulate the body temperature of fur animals is important because fur animals are in an environment with a wide range of temperature changes. Yang Jiashi and Jin Shihou reported that the fasting metabolic heat production and maintenance energy of minks in the early growth stage were 507.9kJ/ kg W 0.75 d and 551.0kJ/ W 0.75 d, respectively, and those in the late growth stage (long hair stage) were 559.0kJW0.75 day and 579.5kJ/ kg W 0.75 d, respectively. On the other hand, the Kp of metabolic energy in the growing period was 0.783, KF was 0.749, KPF was 0.766. The recommended values of dietary energy (GE) concentration for mink during growing period, hair growing period, pregnancy period and lactation period were 20.92MJ / kg, 20.50MJ / kg, 20.50MJ / kg and 20.92MJ / kg respectively, and the dietary metabolic energy levels were 16.74MJ / kg and 16.32MJ / kg during pre-development and long-hair period, respectively. Protein and amino acid needs European and American scholars have made extensive studies on the protein and amino acid needs of minks, which have been reviewed in detail by Glem-Hansen. Mink protein needs to be expressed as a percentage of dietary ME. Glem-Hansen studied the protein requirements of different stages of mink growth period by nitrogen deposition method. It was found that in order to obtain the highest nitrogen deposition, the appropriate protein levels in each stage of mink growth period were (DCP accounted for% of ME); 10 weeks of age to 15 weeks, 41% of 16 weeks to 17 weeks of age, 42% of 19 weeks of age to 21 weeks of age, 32% of 22 weeks of age to 24 weeks of age, 31%. However, further studies have confirmed that the appropriate protein level to meet the highest nitrogen deposition can not fully meet the needs of the protein to produce the best fur quality. Recent studies by Danish, Norwegian and Finnish scholars have shown that when 25%ME is provided by DCP in the later growth stage of minks, the fur quality of minks is not significantly affected, and 30%ME provided by DCP can meet the needs of body weight gain and fur development of minks. However, attention must be paid to the composition of dietary amino acids, especially at the age of about 20 weeks during the peak hair growth period, and the content of sulfur-containing amino acids should account for 3.5%-4.0% of dietary protein. Skrede studied the effects of different protein resources on protein requirements during the growing period. The results show that when using poor protein resources, it is necessary to increase the amount of protein to compensate. When the dietary protein level of adult female foxes is lower than 19%-22%, it is harmful to the health and fur quality of foxes, while the dietary protein level of 23%-26% before mating is enough to maintain body weight; the dietary protein level of female foxes during lactation should not be less than 25%, otherwise it is harmful to the growth of foxes. When the protein level accounts for 28% of the dietary dry matter in the early growth stage (50 days old ~ 160 days old), it can meet the normal growth of the foxes, and 19% to 25% in the later growth stage can meet the protein needs of growth and fur development. The remarkable characteristic of amino acid requirement of fur animals is that the requirement of sulfur amino acid is much higher than that of other livestock. Studies have confirmed that mink hair contains 7%-12% of the total stored protein, of which 60% is cystine. According to Glem-Hansen 's study, the lowest levels of sulfur amino acids in different stages of minks were as follows: 10 weeks old ~ 13 weeks old 3.3 ~ 19 weeks old 3.1 ~ 20 weeks old 24 weeks 4.6 ~ 5.1 ~ 26 weeks ~ 30 weeks 3.7 ~ 3.8. The results of studies on the utilization rate of L-cystine, L-methionine and D-methionine showed that D-methionine could not be used in mink hair growth, and L-cystine and L-methionine could be used effectively, and the utilization rate was slightly higher than that of sulfur-containing amino acids in feed. There are few studies on the need for other essential amino acids, and most of the supply standards are based on dietary amino acid content estimates, and most of them are based on wet feed estimates. Therefore, attention should be paid to the possible damage of feed drying and heating to feed amino acids, especially cysteine, lysine and arginine. Table 1-2 is the latest information on the essential amino acid requirements of minks. Due to the different test methods, the results of methionine, cystine, lysine, tryptophan and threonine requirements are more accurate. However, due to the small number of experimental animals, the requirement of other amino acids can not be determined accurately. The results of nitrogen metabolism and different nutrient gradients showed that the protein requirements of minks in early growth stage and long hair stage were 2.13 g / kg W 0.75.d and 2.17 g / kg W 0.75 days, respectively. For the protein requirements for growth and development during the growing period, according to the sum of the net protein deposition, maintenance and maintenance protein requirements for daily gain of minks of different weeks, the protein requirements at the corresponding age can be obtained. In order to determine the balanced amino acid model and the appropriate proportion in the diet, Jin Shihou et al used the method of analyzing the body composition of minks at different body weight stages during the growing period. the results of the distribution proportion and amino acid pattern of energy substances such as protein, amino acid and fat in the body were clarified, and the suitable proportion pattern and requirement of main essential amino acids in diet were obtained. The proportion of nitrogen maintenance to total nitrogen requirement is very small (0.35~0.41gN/ kg W 0.75 days). Gao Xiuhua and others used growing male minks to carry out digestion and metabolism experiments and feeding experiments. Five diets containing 26%, 32%, 38%, 44% and 50% protein levels were set in the early growth stage, and it was concluded that the optimum protein level in the early growth stage was 38%. The long hair period is 32%. Su Zhenyu and others set 34%, 36%, 38% and 40% protein level diets for minks in the early growth stage, and carried out a comparative feeding experiment. The results showed that the optimum protein level was more than 36%. Jin Shihou et al designed tryptophan, valine, threonine, phenylalanine + tyrosine, lysine, egg + cystine, leucine, isoleucine, histidine and arginine respectively in the early growth stage and long hair stage. accounted for 1.0%, 4.5%, 4.0%, 6.4%, 6.5%, 3.5%, 7.0%, 4.0%, 2.0%, 5.0% of the dietary crude protein content, respectively. The results of feeding experiment showed that it could ensure the normal growth and development of mink and the growth of plush. Liu Qingren and others have comprehensively expounded the law of protein nutrition metabolism and protein requirements of minks, and suggested that the addition amounts of Cu, Fe, Zn, Mn, Co and I in mink diets are 6mg ~ 8mg / kg, 5mg ~ 7mg / kg, 45mg / kg, 45mg / kg, 0.15mg / kg and 0.9mg / kg respectively. Fat and fatty acids require that the fat content of fur animal diet has been very high. In recent years, digestible fat in Danish mink diet accounts for more than 50% of dietary ME, so the fat composition of fur animal diet and the quality problems related to oxidative stability are very prominent. It has been found that when fat fish is used instead of slaughtering scraps, the health status and fur quality of minks decline, and excessive marine fish fat will lead to an increase in the incidence of yellow lipidemia (yellowfatdisease), but the use of good quality fish and antioxidants can overcome most of the problems. Yellow fat disease is considered to be the result of the interaction between dietary polyunsaturated fatty acids and their oxidative degradation products and the body's defense mechanism. Since the 1980s, the use of antioxidants, the addition of vitamin E and the standardization of feed production have significantly reduced the incidence of yellow fat disease. However, the incidence of sudden death and related pectoral muscle necrosis of fast-growing minks increased during the same period. Further studies found that vitamin E, selenium and polyunsaturated fatty acids were not associated with sudden death. The negative effects of polyunsaturated fatty acids (decreased growth rate, increased bleeding, and stress erythema) could be avoided by the addition of vitamin E, but the effect of selenium was minimal. Among the essential fatty acid requirements of minks and foxes recommended by NRC, the lowest dietary linoleic acid level for adult minks is 0.5 per cent of dietary dry matter, compared with 1.5 per cent for lactation, pregnancy and growth. The minimum requirement of essential fatty acids (including oleic acid, linoleic acid and arachidonic acid) for silver foxes is 2 ~ 3 grams per head per day. The dietary fat content of fur animals has always been high. Dietary fat is not only the source of essential fatty acids (EFA) and fat-soluble vitamin A, but also can promote the accumulation of protein. Only sufficient supply of fat can reduce the energy consumption of protein and improve the economic benefit of diet. The energy value of fats and carbohydrates depends on whether the energy they provide is used for tissue synthesis or to sustain growth. In growing animals, fat energy is more effective for body fat deposition than carbohydrates, mainly because fat in food can directly synthesize body fat. While mastering the main nutritional indexes of minks, we should pay attention to the digestion and absorption rate of raw materials and processing techniques and methods when selecting feed raw materials, and set up a reasonable proportion and pay attention to nutrition according to the local climate characteristics and feed raw material resources. formulate a good formula to reduce breeding costs and maximize comprehensive benefits.