Research Progress on Protein Nutrition of Early Weaned Piglets

When choosing the protein source of the diet of early weaned piglets, we should consider the digestibility of protein, the balance of amino acids, palatability and whether it can provide immunity for piglets. The main amino acid limiting the performance of early weaned piglets is lysine, and most studies have shown that the growth rate and feed conversion rate of piglets increase with the increase of lysine content.Owenetc (1995c) Reported that isolated early weaned piglets require lysine as a percentage of the diet.1.65％～1.80%. For maximum production performance, the other amino acids must be maintained in appropriate proportions with lysine. However, there is also evidence that the ideal protein balance for early weaned piglets is not the same as for heavier piglets.Owenetc (1995a) Report includes1.6% lysine of the diet containing spray-dried plasma powder should contain0.41％～0.42% methionine (0.36％～0.37% obviously digestible). Moreover, dietary methionine content accounted for dietary lysine content.27.5%, the growth rate of piglets (post-weaning0d~21d) to max.Mountain stronetc (1997a) reported that the digestible isoleucine requirement for weaned piglets is no greater than that of lysine.60%, and the requirement of isoleucine decreased rapidly. Right.10kg~20kgof pigs, this digestible isoleucine requirement is not greater than that of lysine50％（Mountain stronWait,1997b). Glutamine is not generally considered an essential amino acid for pigs, but has attracted much attention in recent studies. Intestinal atrophy is common in weaned piglets, which is related to the lack of intestinal contents or alienation stress. This atrophy may be caused by the lack of glutamine. Because this amino acid is not only the basic respiratory fuel of intestinal cells, but also provides ammoniated nitrogen required for the biosynthesis of nucleotides (Windmueller,1984). After weaning, the main source of glutamine provided by breast milk is cut off, and because piglets feed intake is small, exogenous supplementation of glutamine is usually small.Ayonrindeetc (1995a,b) report: compared with suckling piglets, the plasma glutamine and glutamic acid concentrations of weaned piglets were significantly reduced, and the decrease of plasma glutamine after weaning indicated that the endogenous glutamine source could not meet the plasma content of this period. Therefore, the piglets should be supplemented with glutamine after weaning. Moreover, if glutamine is necessary to maintain intestinal concentrations, its reduced availability may be associated with intestinal atrophy in weaned piglets.Pluskeetc (1991) suggested that glutamine supplementation in the diet of weaned piglets increased the length of the villi and decreased the depth of the sac. Glutamine has been proposed as a conditionally essential amino acid for weaned piglets.

The high amino acid requirements of early-weaned piglets require a variety of protein feeds, and most diets fed to early-weaned piglets include skim milk, spray-dried porcine plasma protein powder, whey protein concentrate, fish meal, spray-dried porcine blood meal, soybean meal, and further processed soybean products. Among them, spray-dried porcine plasma protein powder is considered to be the only essential protein feed in the diet of early-weaned piglets.Weaveretc (1995a) by adding spray-dried pig plasma protein powder to the diet of weaned piglets.25The average daily gain of piglets increased in the test.39%, the average daily food intake increased32%, feed conversion efficiency is improved5.4%. At present, the mechanism of the role of spray-dried porcine plasma protein powder in production performance is not completely determined, but there are two hypotheses: First, spray-dried porcine plasma protein powder serves as a source of immunoglobulins. When the piglets3At weaning, maternal immunoglobulins are removed from the diet, while spray-dried pig plasma protein powder contains approximately22% immunoglobulin, so it is believed that spray-dried pig plasma protein powder improves the production performance of weaned piglets by providing these immunoglobulins. In order to prove the hypothesis that immunoglobulin is the active component of spray-dried porcine plasma protein powder, many researchers have decomposed porcine plasma protein powder into low-molecular-grade part, intermediate-grade part and high-molecular-grade part, and found that only the high-molecular-grade part produces beneficial effects (PierceWait,1995). If the plasma immunoglobulins can produce beneficial effects, then other sources of immunoglobulins may be found and may be used in diets fed to early weaned piglets. Currently, several research groups are investigating the potential of immune laying hens to resist specific pathogens affecting piglets. The hen builds up immunity to the pathogen and then deposits antibodies in the egg.Imbe on the rightetc (1997) It has been proved that feeding egg yolk antibody to piglets can provide immune protection for piglets.

Another explanation for the effective action of spray-dried porcine plasma protein powder is its role as a flavoring agent. One of the most consistent reports of feeding spray-dried pig plasma protein meal is the rapid increase in feed intake of weaned piglets after feeding compared to other protein feeds.Ermeretc (1994) investigated the pig pair containing20% of skimmed milk powder or8.5degree of preference of% pig plasma protein powder diets, the results found35There are pigs.28Pigs prefer diets containing porcine plasma protein powder. Some researchers have also investigated the optimal content of spray-dried pig plasma protein powder in the diet.Gatnauetc (1993) It is concluded that the piglets have just been weaned6% of spray-dried porcine plasma protein powder produced maximum performance in piglets. Less28Day-old piglets usually recommend the amount of spray-dried pig plasma protein powder in the diet.7.5％～10％（ShursonWait,1995）。

The content of essential amino acids, methionine and isoleucine in pig plasma protein powder is relatively low, so the content of these two amino acids must reach the normal level when using pig plasma protein powder in the diet.Owenetc (1995a,b) demonstrated that an effective effect can be obtained when supplementing synthetic methionine in diets containing pig plasma protein powder. Pig plasma protein powder contains highNaandCl(respectively2.23% and0.4%), therefore, the addition5％～10% pig plasma protein powder, usually can meet the requirements of these two minerals. however,Mahanetc (1996a) proved in diets containing porcine plasma protein powderNaClThe content of at least0.36%Naand0.34%ClTime is useful. Therefore, in the diet containing spray dried porcine plasma protein powder to add at least0.2%NaCl.

Recently, dried skim milk has also been recognized as an essential protein in the diet of early-weaned piglets, providing both high-quality protein and lactose for early-weaned piglets. However, recent studies have shown that skim milk can be replaced by lower-cost protein feeds without reducing production performance (HansenWait,1993a). Fish meal is also a widely used high-quality protein (KimWait,1997); Processed soy products can also be used in the diet of weaned piglets (SonWait,1994); In addition, many other protein feed products have also been confirmed.