Effects Of Diet Composition On Growth Performance, Nutrient Digestibilities And Metabolism, And Meat Quality Of Dairy Bull Calves

Newborn Holstein bull calves were used in a series of trails to study the effect of replacing partmilk replacer with pellet diet and supplying ferrous sulfate preparation for the front120days in the dieton growth performance, nutrients digestibility and metabolism, slaughter traits, gastrointestinaldevelopment and meat quality of dairy bull calves from0-180days for veal production, for the purposeof supplying some scientific basis on the rational utilization of the diary bull calves.Experiment1was designed to investigate the effects of replacing part milk replacer with pellet dieton growth performance, development of tissues and organs, and meat quality of dairy bull calves forveal production. Twenty-four newborn Holstein bull calves with the initial weight of (41.00±1.55) kgwere randomly allocated to two dietary treatments: calvesin group MR were fed milk replacer andChinese wildrye, and those in group MR+PD were fed milk replacer, pellet diet and Chinese wildrye.The trial lasted for180days. Growth performance, nutrients digestibility and metabolism,and bloodindicesof calves were measured.Five calves from each treatment were slaughtered to determineslaughter traits, wet weights of each tissue and organ, rumen and intestinal morphological criteria,rumen fermentation, common decomposition bacteria in rumenand the quality of the dorsal and glutealmuscles. The results showed that there were no significant differences (P>0.05) in average daily gain(0.73vs0.74kg), feed conversion ratio(2.39vs2.36) during the whole experimental period, thedifferences in wither heights, body lengths, heart girths, cannon circumferences and hip widths were notsignificant either(P>0.05); The diarrheaincidence and the diarrheic rate of calves in group MR+PD were4.87and1.31percent lower than those in group MR, respectively(P<0.05). The GE apparentdigestibility, DE metabolic rate, DM apparent digestibility, N apparent digestibility, N apparentmetabolic rate and EE apparent digestibility between the two groups did not have significanteither(P>0.05);There were no significant differences in red blood cell count, hemoglobin, BUN, TP, Alb,Glo, A/G, IgG and IGF-Ⅰ between group MR and MR+PD(P>0.05).No significant differences indressing percentage, meat percentage, dressing percentage of carcass, and ratio of meat to bone werefound between two groups(P>0.05). The fresh weight of liver and reproductive organ of group MR+PDwere significant lower than groupMR, the wet weight and percentagein empty body weight of head&skin, hearet, spleen, lung, kidney, esophagus, intestine and gastrointestinal appendage between the twogroups had no significant differences (P>0.05); Additionally, the wet weight of stomachus compositusand percentage of each stomach compartment in empty body weight of calves in group MR+PD werehigher than those in group MR(P <0.01), the teat length of rumen ventral sacs and the content ofbutyrate and valerate of total VFA of group MR+PD were significant higher thangroup MR(P<0.05),the amount of Ruminococcusflavefaciens of group MR+PD were significant lower thangroup MR(P<0.01) and the amount of Ruminococcus albus and Streptococcus bovisof group MR+PD were significantlower thangroup MR(P<0.05). For the pH, color, share force, cooking rate and driping loss of the meatfrom the veal calves after slaughter, there were no significant differences between two groups (P>0.05), the same to the DM, GE, CP, EE, and some mineral elements like Ca, Fe and so on to the fresh meat,respectively.It was concluded that replacementof40%milk replacer withpellet dietcan maintain thesame growth performance and slaughter traits, reduce the diarrhea incidence and diarrheic rates,improve the development of stomachus compositus and the function of rumen fermentation, but notimprove thecommon decomposition bacteria in rumen, and not affectnutrients digestibility andmetabolism and some relatedblood indices,and can get the veal with the similar quality of Holstein bullcalves from0to180days old for veal production.Experiment2was designed to investigate the effects of supplementation of ferrous sulfatepreparation at early feeding prophase on growth performance and meat quality of dairy bullcalves.Twenty-four newborn Holstein bull calves with an average weight of (41.00±1.62) kg wererandomly allocated to two dietary treatments: group FeSO4·7H2O-0was feed the milk replacer andpellet diet without iron preparation from0to180days, group FeSO4·7H2O-280was feed the milkreplacer and the pellet diet with supplying ferrous sulfate preparation for the front120days, and thenchanged the same feeds used in group FeSO4·7H2O-0. The trial lasted for180d. Growth performance,blood indices and nutrients digestibility and metabolism of calves were measured. Five calves fromeach treatment were slaughtered to determine slaughter traits and meat quality. The results showed thatthere was no significant difference in average daily gain (0.70vs0.73kg) and feed conversion ratio(2.58vs2.39) during the whole experimental period (P>0.05), different in wither height, body length,heart girth, cannon circumference and hip widths was not significant either (P>0.05), no effect innutrients digestibility and metabolism with the supplementation of ferrous sulfate preparation was found(P>0.05), and the incidence of diarrhea of calves in group FeSO4·7H2O-280was0.16percentage pointhigher (P<0.05) than that in group FeSO4·7H2O-0, respectively; there was no significant difference inred blood cell count, BUN, TP, Alb, Glo, A/G, IgG and IGF-Ⅰ between group FeSO4·7H2O-280andFeSO4·7H2O-0(P>0.05), and the hemoglobin of group FeSO4·7H2O-280was significant higher thangroup FeSO4·7H2O-0(P<0.05). No significant difference in dressing percentage, dressing percentageof carcass and ratio of meat to bone was found between the two groups (P>0.05), but the meatpercentage of group FeSO4·7H2O-280was significant higher than group FeSO4·7H2O-0(P<0.05), Forthe pH, color, share force, cooking rate and drip loss of the meat from the veal calves after slaughter,there was no significant difference between the two groups (P>0.05), the same to the DM, GE, CP, EE,and some mineral elements like Ca, Fe and so on to the fresh meat, respectively. It was concluded thatSupplementing ferrous sulfate preparation at the front120d can’t influence the nutrients digestibilityand metabolism, red blood cell count and relative blood indices and meat quality, but can improve thehemoglobin significantly, and can get the higher meat percentage, but have no effect on the meatquality.In conclusion, it can reduce the diarrhea incidence and diarrheic rates, and can improve thedevelopment of stomachus compositus and the function of rumen fermentation when substituting40percent milk replacer using pellet diet; it can improve the hemoglobin significantly and have no effecton meat quality when Supplementing ferrous sulfate preparation at the front120d (iron content120 mg/kg DM) but do not add iron preparation for the last60days(iron content50mg/kg DM).