| In this research, pre- and post-weaning calves were used to investigate the effects of Candida tropicalis(CT) and Mulberry leaf flavonoids(MLF) on growth performance, serum indices, digestion and utilization of energy and nitrogen, and rumen fermentation. Furthermore, the effects of CT and MLF on gastrointestinal development, enzyme activity and antioxidant capacity of calves orally challenged with enteropathogenic Escherichia coli. were studied. The present research was consisted of three trails described below.Experiment 1: Effects of Candida tropicalis and Mulberry leaf flavonoids on growth performance and serum indices in calvesThis trial aimed to investigate the effects of supplementation CT and MLF on growth performance,fecal score, and serum indices in pre-weaning and post-weaning calves. Forty-eight Chinese Holstein bull calves were selected and assigned to four groups with 12 calves each. The trail was designed as a 2× 2 factorial design. The calves in the CT-/MLF- group were fed basis diet which including a milk replacer and a starter. Calves in CT+/MLF-, CT-/MLF+ and CT+/MLF+ groups were fed basis diet supplemented with CT(5×109 CFU/d), MLF(3 g/d), and the compound of CT(5×109 CFU/d) and MLF(3 g/d), respectively. The body weight, serum indices were determined at 28, 42, 56 and 80 days old of calves, and fecal score, diet intake were recorded daily. The result showed: 1) The dietary supplemented with MLF increased the average daily grain(ADG) during 56 to 80 days old of calves(P<0.05). 2) CT and MLF depressed the diarrhea incidence during 56 to 80 day-old and 42 to 56 days old(P<0.05),respectively. 3) The serum concentration of IgA was significantly increased by CT(P<0.05) and concentrations of IgG, BHBA at 80 day-old increased by MLF(P<0.05). However, there were no effect on serum concentrations of IgM, IgA and EGF supplementing MLF(P>0.05). There were synergistic actions of CT and MLF in serum concentrations of IgG, IgM, IgA and β-hydroxybutyric acid(BHBA)(P>0.05). The results suggested that CT depressed calves diarrhea by regulating gastrointestinal flora,and MLF improve the feed conversion efficiency and ADG by enhancing the immunity. There were synergistic action of CT and MLF for enhancing immunity, depressing diarrhea and improving ADG of calves.Experiment 2: Effects of Candida tropicalis and Mulberry leaf flavonoids on rumen fermentation characteristics in calvesThis trail aimed to investigate the effects of CT and MLF on energy and nitrogen metabolism,microbial protein synthesis and rumen fermentation in pre- and post-weaning calves. The trail was designed as same as the experiment 1. The rumen fluid were collected at 28, 42, 56 and 80 days old,digestion trials were conducted to estimate nutrients metabolism at 35 and 63 days old of calves,respectively. The result showed as follows: 1) During pre-weaning period, calves fed a dietary supplementation with CT had increased metabolic rate of energy, and nitrogen deposition, utilization of diet, and biological value of diet(P<0.05). There were synergistic action of CT and MLF in improvingmetabolizable energy and nitrogen biological value(P<0.05). During post-weaning calves, CT increased the ME/GE, ME/DE and nitrogen utilization of dietary(P<0.05). Meanwhile, MLF decreased the fecal energy and total nitrogen excretion(P<0.05). 2) A higher rumen fluid pH value emerged in CT+/MLFgroup than that in others(P<0.05), but no influence for ammonia nitrogen concentration(P<0.05). 3)Compared to other groups, CT+/MLF- group had significantly decreasing propionate concentration, and concentrations of total volatile fat acids and butyrate were increased in CT-/MLF+ group(P<0.05). So,supplementation with CT in the dietary can help to improve microbial protein synthesis and rumen fluid pH value, to increase ADG and nitrogen utilization of calves during the post-weaning. The MLF mainly increased nitrogen deposition, utilization and biological value during the pre-weaning. Meanwhile, MLF have the functions of improving rumen fermentation and raising butyrate concentration. There were synergistic actions of CT and MLF in increasing the rumen fluid pH value, microbial protein synthesis,metabolizable energy and nitrogen biological value of diet during pre-weaning period, and decreasing fecal energy and fecal nitrogen during post-weaning of calves.Experiment 3: Effects of Candida tropicalis and Mulberry leaf flavonoids on gastrointestinal development and enzyme activity in calvesThis trail aimed to investigate the effects of dietary CT and MLF supplementation on gastrointestinal development, enzyme activity and antioxidant capacity of calves challenged with enteropathogenic E. coli. The trail was designed as same as the experiment 1. The calves were orally challenged with E. coli at 56 days old and then were slaughtered at 64 days old. The serum was collected at 7 d of pre-challenged, and 0, 12, 24, 72 h and 7 d post-challenged. Then, the gastrointestinal development and enzyme activity were determined. The results were presented as follows: 1) MLF increased the ADG of calves challenged with E. coli(P<0.05). 2) The fecal score of CT+/MLF- group was decreased at 2 to 3 d of post-challenged(P<0.05), and supplementing CT and MLF were decreased at 4 to 5 d of post-challenged(P<0.05). 3) CT increased the serum concentrations of SOD, GSH-PX of calves at 7 d of post-challenged and AKP concentration at 12 h of post-challenged(P<0.05). There were synergistic action of CT and MLF in increasing concentration of SOD and GSH-PX and decreasing concentrations of MDA and cortisol of calves at 0 h, 7 d of post-challenged(P<0.05). 4) Rumen papillae length of CT+/MLF- and CT-/MLF+ groups were higher comparing with that of CT-/MLF- and CT+/MLF+ groups(P<0.05). Meanwhile, villus height and V/C of duodenum increased by supplementing CT or MLF(P<0.05). 5) MLF improved the activity of α-amylase and xylanase of rumen, as well as the activity of protease of abomasum(P<0.05). The results showed that: under the condition of calves challenged with E. coli, supplementation with CT improved antioxidant capacity,duodenum development and decreased the diarrhea of calves. MLF helps to improve the activity ofα-amylase, xylanase, and total protein concentration, as a result, increasing ADG. There were synergistic action of CT and MLF in increasing immunity, development of rumen papillae and duodenum villus. |
