Lysine nutrition of pork
Nutritionally, the content of lysine in pig feed not only reflects the quality of dietary protein, but also has a greater impact on improving pig weight gain, feed conversion efficiency and carcass composition. Moreover, in recent years, the widespread application of lysine-based ideal protein models has led to more in-depth research on lysine. This paper systematically expounds the research on lysine in pork nutrition at home and abroad in recent years, and provides a reference for the production practice of pig industry.
Lysine is usually the first limiting amino acid in pig feed. In common feeds, except soybean and its meal, lysine is the most easily deficient amino acid. The addition of lysine to corn-soybean meal-based diets can significantly improve feed conversion and performance. The results of Xu Xiliang (1991) showed that the daily weight gain of meat pigs was as high as 0.1%-0.3% lysine and 0.1%-0.2% methionine in the basic feed prepared with soybean cake and cotton kernel cake as the main protein source. 734-755 grams, the ratio of material to meat is 2.95-2.85:1, and the lean meat rate is 57.21%-58.05%, which are 6.5%, 7.6% and 1.2% higher than the control group without addition.
Coma et al. (1990) conducted an experiment in finishing pigs that added lysine from 0.15% to 0.45% in a 14% protein diet, resulting in an average daily gain of 14.49%-42.34%. Goihl (1993) also summarized many experiments and concluded that increasing lysine in pig diets can reduce backfat thickness, increase eye muscle area and lean meat percentage, and this effect is more pronounced in gilts, with a linear distribution. Coffey (1996) also summarized the reports of nine experimental stations in the United States and pointed out that when the lysine in the pig diet was increased from 0.58% to 0.8% by adding lysine, the backfat thickness of gilts decreased by 9%, and the lean Meat growth rate increased by 12%. Coffey also pointed out that when adding a high amount of lysine, attention should be paid to increasing the level of metabolizable energy, preferably adding oil at the same time. The ratio of lysine/metabolizable energy is usually 10.46g/MJ for growing pigs and 8.37 for finishing pigs. g/MJ is appropriate.
Gatel (1992) reduced protein levels in wheat-barley-soybean meal-type diets with the addition of lysine, which had no effect on performance in growing-finishing pigs, while reducing total nitrogen excretion. The total nitrogen discharge decreased by 13.85% in the growing period and 19.32% in the fattening period. Kerr (1995) reported that adding 0.35% lysine, 0.16% threonine and 0.07% tryptophan to pig diets reduced dietary protein by 4 percentage points without affecting growth rate, while nitrogen and energy excretion The amount decreased by 29.3% and 4.4% respectively. The experimental results of pork pigs conducted by Zhang Xingzhou et al. (2000) show that adding lysine can improve the utilization rate of crude protein in the whole diet, thereby reducing the consumption of soybean meal, a high-cost protein raw material, and ensuring the normal growth of pork pigs. In short, adding lysine and other limiting amino acids to low-protein diets can not only reduce environmental pollution, but also save protein resources and reduce feeding costs.
Kerr (1987) reported that feeding pigs with low-protein diets supplemented with lysine resulted in lower caloric production than normal protein levels under heat stress conditions because the liver weight of pigs was reduced when the low-protein diets were fed. decreased (about 8%), while the liver plays a large role in thermogenesis (Koong et al., 1982). Easter also believes that reducing protein and supplementing lysine and other limiting amino acids can improve production performance under heat stress conditions. In a word, adding lysine makes the amino acids of the diet more balanced, improves the utilization rate of the whole amino acid, reduces the nitrogen excretion in the form of urea, thus alleviates the impact of high temperature stress, and is more conducive to the growth and development of meat pigs.
In addition, lysine also has a certain relationship with immunity. Williams et al (1997) studied the effect of different immune levels on lysine requirements, and pointed out that there is a clear interaction between lysine requirements and immune system activity. Klasting et al. (1988) have also demonstrated that chickens fed diets with or without lysine have different responses to immune stimulation. In addition, experiments in mice or rats have shown that lysine deficiency atrophies the thymus and spleen of rats, and the addition of lysine and threonine to the diet can increase thymus weight and increase skin rejection of allografts (Sidranshs et al. , 1972). In conclusion, to improve the growth performance of hogs, it is necessary to reduce the activity of the immune system in hogs, and at the same time increase the level of lysine in hog diets accordingly.
2 Requirement of lysine for meat pigs
The recommended values for lysine requirements for meat pigs are similar in other countries, except for the UK, which is higher, at about 0.7% in the growing period and 0.6% in the finishing period.
2.1 Requirement of lysine in the growing period of meat pigs (20-50kg body weight)
Krick et al. used protein deposition rate, body weight gain and feed efficiency as evaluation indicators to study the optimal requirement of lysine for growing pigs. The results showed that when 22 g of lysine per day (equivalent to 1.02% of total dietary lysine or 0.78 g/MJ of digestible energy) were obtained, the test pigs achieved maximum protein deposition, maximum body weight gain and optimal feed efficiency. However, there are some gaps in the results of some studies. Peters (1995) studied the effect of adding lysine and tryptophan to the diet of growing pigs (20-35kg) and found that 0.6% lysine and 0.15% tryptophan were the best. Lin Yingcai et al. (1995) measured the digestible lysine requirement of growing pigs (30-60kg) by ileal anastomosis. When the result was 0.656% (equivalent to 0.754% total lysine), the experimental pigs obtained the best production. performance.
2.2 Requirement of lysine in the fattening period of meat pigs (50-110kg body weight)
For finishing pigs, gender is an important factor affecting lysine requirements. The Yen study showed that the optimal lysine level in the diets of finisher barrows was 0.72% (equivalent to 18.6g/d and 11.6% of dietary crude protein), while that of gilts was 0.85% (equivalent to 21.2g) /d, dietary crude protein 13.4%). Feed efficiency, body weight gain, and lean growth were best in barrows when dietary lysine levels were 0.6% (CP, 13%), compared with 0.90% (CP, 17.2%) ), gilts have the best performance. There are data that gilts in the 50-90kg range have higher lean meat deposition rates and nitrogen use efficiency than barrows in the same body weight range; Lysine, although gilts eat less daily than barrows, they gain the same daily lean gain. If both barrows and gilts can reach their full production potential, their appetite and weight gain (mainly the ratio of lean meat and fat) are determined by genetic performance, and gilts deposit protein faster than barrows. Faster boars, faster protein deposition, faster lean meat growth, and more lysine needs. Therefore, the lysine requirement of gilts is higher than that of barrows.
Lin Yingcai et al reported that the digestible lysine requirement of 60-90kg finishing pigs is 0.453% (equivalent to 0.548% total lysine). The lysine requirement of pigs in the range of 90-115kg body weight is 0.61%. According to the evaluation indicators of production performance and carcass lean meat rate, the appropriate dose of lysine for gilts of 90-113kg body weight is 0.60%. (1995) used finishing pigs to be divided into two stages (pre-finishing, 50-90kg body weight; late-finishing, 90-110kg body weight) to study the appropriate supply of lysine respectively. The results showed that not only between different sexes, but also The lysine requirements of pigs before and after the same sex were also very different. The results for barrows were: 0.58% in pre-finishing; 0.49% in post-finishing. The results for gilts were: 0.64% and 0.52%. It can be seen that although the weight ranges of pigs in the finishing period determined by different researchers are slightly different, and the research results are also different, their research results reach a consensus, that is, the lysine requirements in the pre-finishing period and the late-finishing period are different. In the early stage of growth and fattening, pigs need more lysine. During this period of time, pigs are depositing lean meat (for which lysine is especially needed), and the deposition rate is accelerating. Later, with the growth of lean meat. Gradually stable, you can reduce the supply of lysine.
In conclusion, the requirement of lysine (possibly including other nutrients) is different for pigs of different stages and sexes. Therefore, in order to save the cost of feed, it is necessary to keep them separately. In practice, in many farms, meat pigs have been raised in stages, and it has been proved that this can more economically and reasonably meet the needs of pigs for nutrients such as lysine. The new version of NRC will fatten pigs. Requirements are given in two stages (50-80kg and 80-120kg).
3 Factors Affecting the Requirement of Lysine in Pork
3.1 Dietary protein levels
Lin et al. (1985) studied the effect of different crude protein levels on lysine requirements. The requirement for lysine gradually increased when the protein level was 17.5% to 21.5%. There is a correlation between the two, that is, for every 1% increase in crude protein, the requirement of lysine increases by 0.04%. Yang Luliang (1994) also reported that the ratio between lysine and protein should reach 4.5%-5.0% in practice, and the ideal protein target should be 6.5%-6.8%.
3.2 Dietary Fiber Levels
Cellulose can combine with amino acids to inhibit the digestion of amino acids, so the amino acid level should be increased in diets with high dietary fiber content. Sauer's (1980) experiment showed that adding cellulose to diets of finishing pigs reduced lysine digestibility.
3.3 Dietary energy levels
O Grady (1978) proposed that the concentration of energy in the diet affects the requirement of lysine. In low-energy (13.6MJ/kg DE) diets, the addition of lysine increased feed intake and weight gain; high The addition of lysine to the energy (14.6MJ/kg DE) diet reduced feed intake but maintained daily gain. Sun Suling (1994) reported that as the ratio of lysine to digestible energy in the diet increased, the production performance of gilts increased linearly, and the optimal ratio was 1.65g/MJ DE. Lawrence (1994) also believed that under high energy conditions, lysine needs to be increased. The experimental results of Patience et al. (1995) showed that for growing pigs, since energy intake limits their growth, the ratio of daily available lysine to digestible energy should be used to formulate diets; for finishing pigs, because energy intake The intake does not limit the growth of its lean meat, and the dietary formula should be made according to the daily effective lysine intake. However, Smith et al. (1999) showed that carcass weight increased with increasing dietary energy content, and the effect of energy content on carcass weight was higher than that on body weight gain. Unlike the results for digestible energy intake and body weight gain, carcass weight gain did not level off as dietary energy levels exceeded a certain level.
3.4 Other amino acid levels in the diet
Dietary supplementation of threonine has been reported to eliminate weight loss caused by excess lysine. The experiment of Williams et al. (1993) pointed out that the ratio of threonine to lysine was 0.64 and 0.65 for the best benefit in growing and finishing pigs.
Williams (1995) also reported that the ratio of lysine to sulfur-containing amino acids has a significant effect on the immune system of pigs, and the recommended ratio is 0.57:1.2. Peter (1995) studies that, growing pigs (20-35kg) diet containing 0.15% tryptophan and 0.6% lysine can meet the needs of low protein levels (11%).
For some time, it was believed that there was a significant antagonism between lysine and arginine. However, Zhang Jinhui et al. (1999) found that there is no antagonistic effect between lysine and arginine, but an imbalance between amino acids.
Some data show that the ratio of pyrimidine to lysine in the diet can significantly affect the weight gain of pigs. In general, the levels of pyrimidine and lysine are 0.75% and 0.9% respectively, and pyrimidine is 0.75% and 0.9% respectively. 83% of lysine.
In a word, the requirement of lysine for hogs is affected by many factors. In actual production, the genotype of hogs, bioavailability of lysine in basic raw materials, feeding frequency, feed preparation and processing should be considered. The optimal amount of lysine is determined according to the loss of nutrients and other conditions.
4 existing problems
4.1 Harm of lysine excess
The study found that pigs fed diets with high lysine levels were more likely to develop rectal prolapse than (P=0.0006) pigs fed standard diets. In addition, high lysine diets tend to lead to lower feed intake in pigs.
4.2 Restrictions on the application of synthetic amino acids
Although the addition of synthetic amino acids to the feed can promote growth, improve carcass quality, and improve feed conversion ratio, it sometimes shows a decrease in utilization in actual diets. For example, when synthetic lysine is added to pig diets, the utilization rate of lysine when fed multiple times a day is 100%, while the utilization rate of lysine when fed once a day is only 45%. Batterham et al. (1974) proposed that increasing the number of feedings had little effect on natural amino acids in the diet. Patridge et al. (1985) also found that when synthetic lysine was added, nitrogen utilization was lower in a single feeding than in multiple feedings.
4.3 Limitations of Lysine Digestibility
Batterham et al. (1990a, b) found that for some heat-treated protein feed ingredients (such as cottonseed cake), changes in the peptide chain and molecular structure may have occurred. This change has little effect on the digestibility of amino acids, while the absorption of amino acids after absorption may occur. Utilization has decreased. Batterham et al. (1992) also found that the utilization rate of lysine in pigs determined by the slope method was significantly lower than its apparent ileal digestibility, that is, the apparent ileal digestibility may overestimate the nutritional value of cottonseed meal. However, for soybean meal, the utilization of lysine is very close to its apparent ileal digestibility. It can be seen that a large part of the lysine in this kind of protein feed may be absorbed into the body because it cannot be effectively used for growth and transformation.
In order to achieve the best effect of fattening of pigs, the reasonable addition of lysine is very important when formulating the diet, because it is directly related to the utilization rate and economic benefits of the diet. However, in our country, there is no reasonable quantitative and qualitative requirement. Therefore, we should conduct further quantitative and qualitative research based on the specific national conditions of our country and use the research results of related disciplines.