Chromium is an important mineral required by the animal body. However, when chromium is added to the feed, overdose or the form of supplementation can easily lead to poisoning. Therefore, changing the form of chromium supplementation, which can increase availability and reduce chromium poisoning, has become a key issue. So far, as the latest addition form of organic chromium,chromium methionine can improve the utilization rate of chromium and reduce the risk of poisoning. Chromium methionine is listed as a permitted additive in the “Catalogue of Feed Additives (2013)”. Reports at home and abroad show that chromium methionine can improve meat quality, reduce self-fat, and increase the lean meat rate of fattening pigs. However, there are few reports of its application in sow feed. This article will briefly introduce the application of chromium methionine as the third-generation additive in sow feed.
1 Physical and chemical properties and mechanism of action
of chromium methionine 1.1 Physical and chemical properties of
chromium methionine Chromium methionine is a chelate complex formed by -NH3+ and -COO- in methionine and chromium (Ⅲ). The ligand molar ratio was methionine:chromium 3:1. Different chemical forms of chromium sources have different bioavailability, and the bioavailability of chromium methionine is higher than that of inorganic chromium. Chromium methionine has stable physical and chemical properties and does not oxidize fat-soluble vitamins and related oils and fats in the full-price feed. The main function of chromium methionine is to reduce morbidity and mortality under stress conditions; at the same time, it can improve carcass quality and increase lean meat rate. Under reproductive conditions, the estrus period of sows is shortened, and the conception rate and the number and survival rate of litters are increased.
1.2 Mechanism of action of chromium methionine
Chromium is an important mineral. Chromium methionine is stable in both acidic and alkaline conditions; it can be absorbed through the absorption pathway of amino acids, and the absorption and utilization rate is high. Essential for glucose, protein and fat metabolism in animal tissues. Chromium is known to be involved in regulating blood lipids. Chromium acts as a glucose tolerance factor (GTF) to regulate blood sugar levels. Blood glucose levels and their homeostasis are related to protein or fat synthesis in the body. Chromium can regulate the affinity of tissues to insulin, transmit information through the hypothalamus-pituitary-ovarian endocrine axis and improve the reproductive performance of sows. During follicular development, when chromium is relatively sufficient in sows, the number of ovulations can be increased, the quality of eggs can be improved, and thus the growth and development of embryos can be improved. Cr3+ assists insulin to act on the hypothalamus, hypothalamic gonadotropin stimulates the release of luteinizing hormone from the pituitary gland, and luteinizing hormone acts on the ovary to promote follicle maturation and ovulation, thereby ensuring the good development of the embryo to a certain extent and improving the sow. Litter size. Chromium affects the ovulation rate and embryonic growth and development of sows by altering the secretion levels of insulin, follicle-stimulating hormone and luteinizing hormone, thereby affecting the reproductive performance of sows. Lindemann (1995a) showed that chromium can affect glucose and lipid metabolism by enhancing insulin function. Cox et al. (1987) demonstrated that gilts entered estrus after insulin injection and increased ovulation rate. Whitley (1998) showed that injection of insulin 5 days after lactation in producing sows can increase follicular estradiol and progesterone levels. Therefore, it can be concluded that chromium feeding in sows affects insulin and blood glucose metabolism, thereby affecting the reproductive performance of sows.
Chromium in chromium methionine exists in the form of trivalent. After chromium enters the blood, it can increase the insulin level in the blood to improve the utilization efficiency of glucose and energy in the feed, promote the absorption of amino acids and the synthesis of protein, inhibit the decomposition of fat tissue and reduce blood lipids. level, so as to meet the nutritional needs of the fetus of pregnant sows and the nutritional needs of milk during lactation.
2 The application of chromium methionine in sow feed
The application test of chromium methionine in sow feed is few, and other organic chromium such as chromium picolinate, chromium yeast, chromium nicotinate have been widely used in sow feed. Huang Zhijian et al. (2001) tested the effect of two organic chromium (chromium nicotinate and chromium yeast) on sow reproduction, and showed that adding 200 μg/kg chromium nicotinate and chromium yeast to the diet of lactating sows, Piglet mortality decreased by 3.7% and 1.8%, respectively, and the weaning weight increased to varying degrees. The results of Mo Jingchuan et al. (1999)  showed that adding 200 μg/kg of yeast chromium to the diet can shorten the reproductive cycle of sows by 7 days, increase the number of live piglets by 2 on average, and reduce the number of litter deaths by 1. , can significantly improve the comprehensive reproductive performance of sows. Du Liyin et al. (2006)  used large white sows during lactation as experimental animals. Adding 1.65 mg/kg chromium picolinate to the diet could significantly shorten the interval between sows returning to estrus after weaning, increase litter size and increase litter size. Birth weight. The experimental results of Liang Xianwei et al. (2002) also showed that adding organic chromium (protein and polypeptide complexed chromium) 200 μg/kg to the sow reproductive and gestation diets can improve the reproductive performance of sows and reduce piglet mortality by 5. 5%, significantly increased the litter weight of 21-day-old piglets and the average piglet weight of 21-day-old piglets. However, since yeast chromium is obtained by fermentation and separation of brewer’s yeast in a medium rich in inorganic chromium, its production method determines that its product quality must have great fluctuation, and even a certain amount of inorganic chromium may be mixed. Chromium nicotinate is usually composed of chromium chloride and nicotinic acid, and the chemical structure of nicotinic acid determines the poor organic chelation degree between nicotinic acid and chromium. In addition, chromium nicotinate is more unstable in an acidic environment, resulting in a large loss of chromium nicotinate in the process of digestion and absorption. Chromium picolinate enters the organism and maintains the original form for a long time, and the chromium element is closely combined with the pyridine ring, so that chromium not only cannot be used, but also can cause DNA breakage and DNA mutation. When the chromium ion is separated from the pyridine ring, it will also generate some hydroxyl ions, which will have a certain damage to the body, and the pyridine ring will also poison the liver. Chromium methionine, as an amino acid chelated chromium, is stable under acidic conditions or under alkaline conditions, and can be absorbed through the absorption pathway of amino acids, with high absorption and utilization rate, avoiding the defects of other organic chromium. Jia Ruilian et al. (2012) studied the effect of chromium methionine on the reproductive performance of sows. By adding 200 μg/kg of chromium methionine to the diet of sows, the litter size of sows in the next litter was increased by 1.3-1.4, and the lactation rate was reduced. weight loss of sows and shortened estrus intervals in sows. Perez-Mendoza et al. (2003) also suggested that adding 400 μg/kg of chromium methionine to sow diets significantly increased litter size compared with controls.
In conclusion, it can be concluded that the addition of chromium methionine in the diet can effectively improve the reproductive performance of sows. Supplementation of chromium methionine in sow diets can shorten the sow estrus interval, improve piglet survival and litter weight, and increase weaned piglet weight. Chromium methionine is listed as a permitted additive in the “Catalogue of Feed Additives (2013)”, and its application in sow feed in the future can bring considerable economic benefits.