Effects Of Protein And Amino Acid Nutrition On Indexes Related To Immune Response Of Early Weaned Dairy Calves

The neonatal calf has heightened susceptibility to infectious disease. Traditional calf-rearing programs limited nutrient intake from milk to promote dry-feed intake and early weaning. Dramatic improvements in growth performance achieved by feeding milk replacer with plant protein is hypothesized to be associated with enhanced immune function and increased resistance of the calf to infectious disease. Objectives of this dissertation were to determine the influence of protein nutrition on the immune response of the calf, and to improve the balance of amino acid and the performance of the calf.1. The influence of protein level on the related indexes of immune response of the calf.Fifteen male Chinese Holstein calves were selected to determine the influence of protein level of milk replacer on the immune response and other serum index of the calf. The results indicated that the highest IgG and AKP in serum (P>0.05), the live body weight and the index of spleen were observed when the protein level is 22% of milk replacer. And the concentrations of IL-1, the population of mast cells (P<0.05) were significantly improved with the increase of protein level of milk replacer. The GH, IGF-1, TAOC in serum had a trend of increase with higher of protein level of milk replacer, but the concentration of NO in serum decreased with highest protein level of milk replacer. The results suggest that it was beneficial to the anabolic metabolism of protein and the immune enhancement when the protein level is 22%.2. The influence of plant protein content on the related indexes of immune response of the calf.Twelve male Chinese Holstein calves were selected to determine the influence of plant protein content of milk replacer on the related indexes of immune response of the calf between 6～11days . The results indicated that the highest total protein (P>0.05), GH (P>0.05), IgG (P>0.05) and TAOC (P<0.05), NO (P<0.05), AKP (P<0.05), the lowest urea nitrogen (P>0.05) in serum of calves between 6～9 days were observed when the plant protein content is 50% in milk replacer. And the diarrhea was serious when the plant protein content is 80% of total protein of milk replacer, especially between 6～8 days.3. The influence of plant protein content on the related indexes of immune response of the calf.Twelve male Chinese Holstein calves were selected to determine the influence of plant protein content of milk replacer on the related indexes of immune response of the calf between 2～8 weeks . The results indicated that the concentration of IgG (P>0.05), IL-1 (P>0.05), TNF-α(P>0.05), AKP (P<0.05)were highest when the plant protein content is 50% of total protein in milk replacer And the concentration of IgG,IL-1 and TNF-αhad a trend of decrease between 2～4 weeks, but had a trend of increase between 4～8 weeks. The concentration of SIgA and the population of mast cells (P<0.05) in mucosal became lower and the population of goblet cells (P<0.05) in mucosal became higher with the increase of plant protein content in milk replacer. But there no influence of plant protein content of milk replacer on the concentration of lysozyme, GH and IGF-1 in serum. The morbidity of calves significantly enhanced when the plant protein content is 80% of total protein of milk replacer. The results suggest that the calf can adapt to massive plant protein after 4 weeks.4. The influence of main limited amino acid on the immune response and the performance of calvesTwenty male Chinese Holstein calves were selected determine the influence of main limited amino acid (LAA) on the immune response and the performance of calves. The results indicated that the deficiency of LAA decreased the intake, BW, ADG and the nitrogen retention, digestibility and biological value of nitrogen. And the lysine had most distinct effect on the performance and the nitrogen balance, and then was the methionine and the threonine. The lysine deficiency increased the innate immunity response; however, the threonine had little influence. The lysine and methionine deficiency respectively made the immune system migration from Th1 type to Th2 type, the humeral immune response enhanced. The morbidity and the mortality of calves also improved significantly with the deficiency of lysine and methionine respectively. The threonine deficiency decreased the organ index of thymus, spleen and hepar.5. The influence of immunological stress on the optimum amino acid pattern of LAA of calves Forty male Chinese Holstein calves were selected to determine the influence of immunological stress on the optimum amino acid pattern of LAA of calves by the method amino acid deletion. The body temperature enhanced significantly with the challenge of lipopolysaccharide. The results indicated that the immunological stress enhanced the innate and adapt immune response, and the migration of immune response from Th2 type to Th1 type happened. But the intestinal mucosal immune response decreased. The performance and nitrogen balance also were suppressed by the immunological stress. More importantly, the limit sequence of LAA were changed from lysine > methionine > threonine to lysine > threonine > methionine, and the optimum amino acid pattern of Lys/Met/Thr for calves between 25～27 days changed from 100/29/58 to 100/27/61, the Pattern for calves between 55～57 days changed from 100/30/62 to 100/27/60 with the challenge of LPS.