Some noticeable problems in pig feed production at present

Introduction: pig feed accounts for more than 30% of the world's total feed Therefore, animal scientists in many countries have invested a lot of energy and material resources to study the nutrition and behavior of pigs, in order to further develop economic, reasonable and effective pig feed In this paper, combined with some practical application value of nutrition research in pig industry, several noticeable problems in pig feed production are summarized 1 The problem of excessive protein in feed The concentration and quality of crude protein in diet is the most commonly used index to evaluate the quality of commercial pig feed When the protein (amino acid) in the diet is insufficient, it is difficult for the growing finishing pigs to develop the best growth potential However, if the protein in the diet is too high, the production performance and economic benefit of the pigs will also be reduced American scientists (Chen, H.Y., AJ Lewis, P.S Miller, etc., 1999) recently studied the effect of protein excess on the performance and protein metabolism of growing pigs The crude protein was divided into 5 levels (3-25%), and the body weight of growing pigs was 51-1kg The protein content in the typical diet of pigs in this weight stage was 13-15% The results showed that with the increase of dietary protein concentration, the feed intake decreased linearly, and the body weight gain and protein deposition also decreased High concentration of protein decreased the amount of body fat deposition, and the weight of visceral organs (liver, kidney, pancreas, etc.) increased with the increase of protein level The study also showed that the toxic side effects caused by excessive protein had more effects on the reserve sows than on the reserve boars Obviously, when the protein concentration of pig diet is too high, part of the energy in the diet should be used to eliminate the excessive nitrogen produced by protein metabolism in the body, so as to prevent the toxic effect caused by it As a result, the energy used for body protein synthesis and body fat deposition is reduced Therefore, if the protein in the diet exceeds the actual needs of pigs, it will not only increase the feeding cost, but also cause the decline of production performance and carcass quality Therefore, the daily formula design of pigs must meet the genotype and environmental constraints of pigs 2 The problem of toxin in feed There are many toxins produced by mould in feed, especially aflatoxin When pigs eat the feed contaminated by aflatoxin, the growth, health and growth of pigs will be adversely affected The main way for feed producers to deal with this problem is to mix the contaminated feed ingredients with the non polluted ones, so as to reduce the concentration of toxins Other methods include ammoniation of feed ingredients, removal of active molds by ultraviolet radiation, enzyme-related immunosorbent assays or "fast card" tests to detect toxins at risk The chemical structure of aflatoxin molecules makes it easy to adsorb on other substances, such as clay When it adheres to these substances, it will not be absorbed by animals and discharged with feces T C Scheil and colleagues at the University of technology of Virginia studied the effects of different clays on pig behavior in aflatoxin contaminated maize (reports on stocks, 1990-1992) The researchers used a diet consisting of unpolluted corn (control diet), a diet containing aflatoxin at a concentration of 500 ppb, and seven diets containing aflatoxin at a concentration of 5-ooppb plus 0.5% of various clays The feeding experiment of hybrid pigs was carried out The effective concentration of clay is determined by titration test in advance Pigs were fed these experimental diets from the 7th day after weaning for a total of 4 weeks Compared with pigs fed normal diets, pigs fed contaminated diets grew slower The daily average weight loss was 27.5% and the food intake was 31% However, the feed efficiency did not decrease significantly When aflatoxin was added to the food store alone, the concentration of serum urea nitrogen and serum albumin, two substances indicating liver function, decreased significantly After adding the clay, the growth and eating of the pigs who had eaten the feed containing aflatoxin were improved It was found that the feed containing fibrous active clay had the least effect on pig weight gain and feed intake, while the feed containing sodium bentonite and hydrated sodium calcium silicate aluminate had the most effect The concentrations of serum urea nitrogen and serum albumin were higher in pigs fed with clay In order to study whether the clay adsorbed aflatoxin can also adsorb other nutrients, the researchers fed pigs with 1% sodium bentonite and 1% sodium bentonite free feed contaminated with aflatoxin and aflatoxin free feed, respectively In two kinds of polluted diets, sodium soap can significantly reduce the absorption of calcium, magnesium and iron (P In another experiment, the researchers tested 125 crossbred pigs with feed containing 0.5% sodium soap, boiling soil, calcium soap soil and fiber active clay Clay did not slow down the growth of pigs, nor did it reduce feed intake and feed efficiency Interestingly, the boiling soil and fibrous clay had an obvious promoting effect on the average daily increase (P < 0.05) and feed intake (P < 0.01) 3 The variability of feed nutrient analysis is undeniable The nutritional components of different batches of corn and soybean meal are very different The nutritional content of corn is related to the genotype and growing area of corn, and the nutritional content of soybean meal is also affected by the processing technology of soybean meal and the amount of shell added back to soybean meal A recent report (nrc-42) Swine Nutrition Committee, 1999) pointed out that even for the same batch of samples, the analysis results of different chemical laboratories are quite different In this investigation, researchers analyzed the dry matter, crude protein, calcium, phosphorus, amino acid and selenium content of 16 kinds of corn and soybean meal from different sources in 22 different analysis laboratories Except for some exceptions (such as crude protein), the nutritional components of corn and soybean meal from different sources vary greatly, and the analysis results of samples from the same source and different laboratories also vary greatly Among the indexes, the variation of selenium content in corn was 0.02-0.29% (range of variation was 350%), and in soybean meal was 0.08-0.95% (range of variation was 1088%) The concentration of calcium in corn and soybean meal is also different, but it is mainly affected by the source of samples, but not by the location of analysis Therefore, feed and raw materials must not only be analyzed frequently, but also be carefully selected for reliable chemical analysis laboratory Some laboratories analyze carefully, with high repetition rate and reliable results, while others are perfunctory 4 The problem of adding B vitamins to Weaned Piglets' feed Thiamine (B1) and pyridoxine (B6) are not necessary or should not be added to most of the diets of piglets Piglet feed itself contains enough of these vitamins to meet the needs of nutritionists The recommended requirement of thiamine and pyridoxine in 5-20kg pig diet is 1.0mg/kg and 1.5mg/kg respectively The contents of thiamine and pyridoxine in typical corn soybean meal diet were more than 3.0mg/kg and 5.0mg/kg respectively Recent data from the United States and Canada show that high concentrations of pyridoxine have a positive effect on piglet growth, while thiamine does not In order to prove this point, many experiments have been done, but most of the studies are not successful, because either the influence of pyridoxine is weak and difficult to determine, or the influence of pyridoxine is covered by other vitamins In a recent titration study, researchers at Kansas State University (wood worth, J.C., r.d.coodband et al., 2000) found that when 3.3mg/kg pyridoxine was added to weaned piglets, the growth performance of the first two weeks after weaning was improved, but there was no effect on the subsequent feeding stage The growth performance of pigs in the final test group (3.3mg / kg) was not significantly different from that of the control group (without pyridoxine) However, we can not draw a certain conclusion from here Because we are not sure whether such a result is accidental In theory, a dose less than 50 times the need for pyridoxine (75mg / kg) should not cause toxic side effects (growth reduction) Therefore, in this stage, it is necessary to reevaluate the pyridoxine requirement of piglets However, we should be alert to those who encourage the addition of pyridoxine to 100mg / kg before the exact results of the required amount are given 5 The problem of adding emulsifier in Weaned Piglets' feed The feed intake of newly weaned piglets is less, so piglets often can't get the nutrition necessary for the optimal development, especially the energy Feed producers sometimes add fat to weaned piglet feed to increase energy concentration But in the weaning period, the digestive system of pigs often lacks the ability to use these fats Some emulsifiers released by the digestive system of adult pigs can improve the digestion and absorption of fat Researchers at Kansas State University, led by Mr D bjones (1992), conducted a series of experiments to see if commercial emulsifiers could improve the behavior of newly weaned pigs In three trials, pigs were weaned on the 17th or 21st day after birth and fed with piglet feed The basic feed for piglets includes corn, soybean powder, dry whey, dry skimmed milk, antibiotics, fats and other nutrients Fat substances include soybean oil, coconut oil, animal fat and lard, which account for 10% of the feed Because the digestibility of vegetable fat is higher than that of animal fat, the quality of fat from different sources was tested respectively The added commercial emulsifiers (lecithin and solution lecithin) accounted for 10% and 30% of the fat substances respectively The digestibility of dry matter, fat and total energy in feed containing soybean oil and coconut oil is higher than that of animal fat and lard The reason for this difference may be that the length of carbon chain and the degree of unsaturation of fatty acids in different fat sources are different Increasing fat means increasing nitrogen, but this increase is similar to the original fat source The fat digestibility of animal fat feed was 80.9% When the added lecithin or blood-soluble lecithin reaches to 10% of animal fat, the fat digestibility can be increased to 88.4% and 83.9% respectively The addition of emulsifier reduced the digestibility of fat in lard feed When the emulsifier was increased from 5% to 30%, the digestibility of nutrients was not affected During the lactation period of 35 days, adding soybean oil and animal fat did not affect the average daily weight gain However, the feed efficiency was significantly improved (P < 0.002) Grinding degree of feed: grinding grains and other ingredients can increase the surface area of feed particles during digestion However, the cost of grinding feed into very small particles is very high, which consumes a lot of mechanical energy and increases the wear of the grinding machine In addition, eating very small milled feed will cause a certain degree of damage to the pig stomach Feed producers are interested in the size of feed particles with the highest feed efficiency under the optimal state of animal digestion behavior without harming pig health According to a survey by researchers from Kansas State University (daily report on swine, 1992)