Effect Of Milk Replacer Acidity And Acidity Adjusting On Growth Performance, Blood Gas Parameters And Gastrointestinal Tract Development In Pre-ruminant Calves

Four trials were conducted with pre-ruminant calves as animal models to study the effect of acidity acidity regulators in a milk replacer on the calves'growth performance, digestibility of nutrients, blood biochemical parameters and gastrointestinal characteristics.Experiment 1: Effects of the acid-binding capacity and pH values of ingredients of a calf milk replacer on its relevant characteritics of acidityThis experiment was conducted to study the effect of the content and acid binding capacity (ABC) or pH value of ingredients of a calf milk replacer on its ABC or pH value. Ten feed ingredients indicated in a Chinese patent for a calf milk replacer were chosen to produce the calf milk replacer according to an L27(313) orthogonal design. The ABC and pH value of both the ingredients and the milk replacer were determined, and then a multiple regression method was used to analyze the data. The results showed that the proper content of each ingredient in the calf milk replacer was as follows: specially treated soybean, 35-60%; whey powder,≥30%; L-methionine hydrochlorate,≤0.5%; L-lysine hydrochlorate,≤0.5%; CaCO3, minimum; CaHPO4, about 1%; vitamin premix, 0-0.02%; NaCl, about 1.0%. There were significantly multiple linear correlations between the ABC or pH of the calf milk replacer and the content, ABC or pH of its ingredients.Experiment 2: Effects of the acidity of a milk replacer on growth performance, digestibility of nutrients, blood parameters and gastrointestinal characteristics in pre-ruminant calves The pH values of a milk replacer (6.2, 5.5, 5.0 or 4.5) and the ratio of vegetable protein to total protein in the milk replacer (50 or 80%) were used to form a 4×2 factorial design in this experiment. Forty eight neonatal healthy Holstein male calves were allotted to eight groups and each group was fed with one of the 8 milk replacers. The experiment lasted for 56 d. A digestion trial was conducted in 2 stages of 25-27 d and 53-55 d. Three calves of each group were slaughtered at the end of experiment. The results showed that the calves fed the milk replacer with an appropriate pH value had improved blood parameters and development of the gastrointestinal tract, enhanced nutrient digestibility and growth performance, decreased diarrhea incidence. The optimal pH value of the calf milk replacer was found to be 5.0.Experiment 3: Screening of the formula of compound acidity regulators for a calf milk replacerAn in vitro experiment was conducted with six candidate acidity regulators to measure their antibacterial activity in vitro (Y1), pH value of 1% solution (Y2), buffering capacity of 1% solution (Y3), the volume of acid solutions to reduce the pH value of a milk replacer to 5.0 (Y4), and the buffering capacity of the milk replacer solution with added acids (Y5). There were two parts in the experiment. One was to test the individual acid. The parameters Y1 to Y5 of formic acid,acetic acid, citric acid, fumaric acid, lactic acid and hydrochloric acid were determined respectively with five replicates each. The other part was to screen the formula of compound acidifying agents. Formic acid, acetic acid, citric acid, fumaric acid, lactic acid and hydrochloric acid were used as ingredients according to a formula uniform design table U20*(206). There were twenty treatments with five replicates each. A stepwise multiple regression method was used to analyze the data, and then the optimal compound solution was chosen. The results showed that formic acid and hydrochloric acid were the best acidity regulators, and the optimal formula of compound acidity regulator was 40.74% formic acid, 50.62% hydrochloric acid and 8.64% citric acid. A significantly quadratic relationship existed between five indices (Y1 to Y5) and tested acids.Experiment 4: Effects of acidity regulators in a milk replacer on growth performance, digestibility of nutrients and blood biochemical parameters in pre-ruminant calvesTwenty four neonatal healthy Holstein male calves were allotted to four groups, and one group was fed with a normal milk replacer with a pH value of 6.2 (Group F1), the others were fed with the milk replacer after reducing its pH value to 5.0 by adding formic acid (Group F3) and compound acidity regulator (Group F2 and F4), respectively. The ratios of vegetable protein to total protein in the milk replacer were 50% (Group F1, F2 and F3) or 80% (Group F4). The digestion trial was conducted twice during the trial. The results showed that acidity regulators played an important part in the milk replacer fed to the calves less than 28 d, as exhibited by improved blood biochemical parameters, lowered incidence of diarrhea, and enhanced growth performance of the calves. Adding formic acid in the milk replacer significantly lowered the count of bacteria in the calves'rectum feces when compared with the compound acidity regulator. The ADG of the calves fed with the milk replacer of pH 5.0 and containing 80% vegetable protein was similar to that of those fed with the milk replacer of pH 6.2 and containing 50% vegetable protein.In conclusion, pre-ruminant calves fed with a milk replacer with a properly lowered pH value showed improved blood parameter and development of the gastrointestinal tract, improved nutrient digestibility, lowered diarrhea incidence, and enhanced growth performance. The optimal pH value of the calf milk replacer containing vegetable protein was found to be 5.0. The in vitro method used in this study was capable of evaluating compound acidity regulators.