Effects Of Feed Combination On Ruminal Fermentation, Nutrients Digestibility, And Growth Performance, Of Weaned Calves

This study was conducted to investigate the effects of feed combination on rumianl fermentation, nutrients digestibility and growth performance of weaned calves. The trial in vitro determined the ruminal fermentation parameters and microbial protein yield of calves to choose three more optimal dietary groups for animal trial. The animal trial comparied and analyzed the effects of feed intake, average daily gain, incidence of diarrhea, body measurement indexes, blood biochemical indexes, ruminal fermentation parameters, microbial protein and nutrient digestibility of calves, and finally recommended more reasonable diet and feeding management scheduling for weaned calves.The first part was to determine effects of forage combinations and concentrate-forage ratios on ruminal fermentation in vitro and microbial protein yields of weaned calves. Different forage combinations (100% alfalfa hay, 66.7% alfalfa hay+33.3% oat hay, 50% alfalfa hay+50% oat hay, 66.7% alfalfa hay+33.3% whole corn silage, 50% alfalfa hay+50% whole corn silage and 33.4% alfalfa hay+33.3% oat hay+33.3% whole corn silage) and concentrate-forage ratios (60:40 and 50:50) of diets were used as fermentation substrate treatments and fermented by artificial rumen in vitro with rumen fluid taken from 10 three-month weaned female dairy calves. The rumen total volatile acid concentration, ammonia nitrogen concentration,48h gas production, pH value, microbial protein yield, and in vitro dry matter disappearance rate were detected in the above 12 treatment groups.The results showed that the rumen pH value was affected significantly by both concentrate-forage ratio and forage combination (P<0.05); however, microbial protein yield, total volatile acid concentration and 48h cumulative gas production were not affected (P> 0.05). The ammonia nitrogen concentration in the artificial rumen was significantly improved by concentrate-forage ratio of 60:40 when compared with concentrate-forage ratio of 50:50 (P<0.05). Meanwhile, the dry matter disappearance rate was significantly higher as the concentrate-forage ratio of 60:40 compared with 50:50 groups (P<0.01). According to the results, three treatment groups of forage combination of 100% alfalfa hay,66.7% alfalfa hay +33.3% oats hay and 66.7% alfalfa hay+33.3% whole corn silage with concentrate-forage ratio of 60:40 were the better combinations for fermentation.The second part was to assess effects of diets combination on growth performance and digestibility of weaned calves. Forty-five weaned calves are assigned into 1 of 3 treatments using randomized block design in this trial. There were 15 animals in each treatment. Three treatments were fed alfalfa (AH,100%Alfalfa hay), oat (OH,33.3% Oat hay+66.7% alfalfa hay) and silage(WS,33.3% whole corn silage+66.7% alfalfa hay) with same pellet feed, respectively. The trial was last 35 days in total from 1 week after weaning to 102 days of age. Growth performance was determined and rumen fluid, blood samples were collected at 1,7,14,21,28 and 35 days of experiment period prior to morning feeding. Five calves aged 97～102 days were randomly selected from each group to collect samples and measure the apparent digestibility. The rumen fermentation, blood biochemical parameters, dry matter intake, feed composition were detected in the above 3 treatment groups. The results showed that the average daily gain of calves fed WS group was significantly lower than the AH and OH calves in the experiment period. Dry matter intake of OH calves aged of 97～102 days was significantly higher than the AH and WS calves. The feed conversion ratio of the group OH was 36.36% and higher than AH and WS groups (P>0.05).The diarrhea frequency, diarrhea rate and feces index of OH calves was significantly lower than the AH and WS calves (P<0.05). In the experiment period, the change of chest girth in OH group significantly higher than both AH and WS groups, the change of body slanting length in AH group was significantly higher than other groups, the change of the cannon bone circumference in WS group was significantly lower than both AH and WS groups.For the ruminal fermentation, the ammonia nitrogen concentration in AH group was significantly higher than other groups, proportion of propionate had significantly differences in each group, proportion of butyric acid in OH group was significantly higher than other groups. Ratio of acetate to propionate and total volatile fatty acid concentration had extremely significant difference in each groups (P<0.01). Protozoal protein content had extremely significant difference in each groups. Bacterial protein and microbial protein had significant difference in each groups.For the apparent digestibility of dietary nutrients, apparent digestibility of NDF, ADF and EE in WS group were significantly lower than that of other experimental groups. Apparent digestibility of CP in OH group was significantly higher than other groups (P＜0.05).For serum indexes, growth hormone of OH group was extremely significantly higher than other groups, and the serum urea nitrogen content of AH was significantly higher than other groups (P=0.012). Through comprehensive comparison, the recommend orders of diets of 3-month-calves were OH group, AH group, WS group.In conclusion, calves fed OH group had certain advantages to reduce incidence of diarrhea to keep health; improve feed intake, feed conversion ratio and average daily gain; reduce feed cost and environmental pollution. Therefore, it is the main 3-month-calves feeding pattern existed in domestic farms, which is’alfalfa hay+starter feed’, would be changed to ’26.67% alfalfa hay+12.33% oat hay+60% palatable starter feed’.