| This experiment was conducted to investigate the effects of sodium butyrate(SB)and Yucca(Y)on growth performance,rumen fermentation and serum parameters of dairy calves before weaning.In the first experiment,the optimal dosage of SB and Y promoting the growth of dairy calves before weaning were selected.Furthermore,according to the result of the first experiment,evaluation of SB and Y,both individually and in combination,for their ability to improve growth,health and reduce diarrhea in newborn dairy calves challenged with Escherichia coli K99 before weaning were performed.The specific research content is as follows:Experiment 1: To investigate the effects of SB on growth performance,rumen fermentation,antioxidant and immune capacity of dairy calves before weaning.Forty female newborn Holstein calves were randomly divided into 4 groups(n = 10).SB was fed from the 4 days of age.Each group was supplemented with a dose of 0 g/d SB(SB0),15 g/d SB(SB15),30 g/d SB(SB30),and 45 g/d SB(SB45).The test was carried out until the end of weaning at 60 days of age.The results showed that: 1)With the increase of SB dose,the average daily gain of dairy calves increased in a quadratic curve(P = 0.066),and SB30 group was the highest.2)With the increase of SB supplementation,the ammonia nitrogen concentration of rumen fluid in the treatment group was quadratically decrease(P < 0.05).3)With the increase of SB supplementation,the malondialdehyde content in the serum of dairy calves decreased linearly,and the glutathione peroxidase activity showed a quadratically increase(P < 0.05).4)With the increase of SB supplementation,the content of immunoglobulin A in the serum of dairy calves showed a trend of quadratic increase(P = 0.097).Considering the conditions of experiment,SB recommends an optimal dosage of 30 g/d.Experiment 2: To explore the effects of Y on growth performance,rumen fermentation,antioxidant and immune capacity of dairy calves before weaning.Forty female newborn Holstein calves were randomly divided into 4 groups(n = 10).Y was fed from the 4 days of age.Each group was supplemented with a dose of 0 g/d Y(Y0),3 g/d Y(Y3),6 g/d Y(Y6),and 9 g/d Y(Y9).The test was carried out until the end of weaning at 60 days of age.The results showed that: 1)With the increase of Y supplementation,the average daily gain of dairy calves showed a quadratic curve increase(P = 0.057),and the value of Y9 group was the highest;the fecal score of dairy calves decreased linearly(P = 0.001).2)With the increasing Y supplementation,the Acetic: Propionic in rumen fluid of dairy calves increased linearly(P < 0.05).3)With the increase of Y supplementation,the activity of glutathione peroxidase and catalase in serum of dairy calves increased linearly(P < 0.05).4)With the increase of Y supplementation,the concentrations of immunoglobulin A and immunoglobulin G in the serum of dairy calves increased linearly(P < 0.05),and the value of Y9 group was the highest.Considering the conditions of experiment,Y recommends an optimal addition dose of 9 g/d.Experiment 3: This experiment was conducted to evaluate the effects of supplementation of sodium butyrate(SB)or Yucca(Y)on the growth and health of newborn calves challenged with Escherichia coli K99.A total of 40 healthy Holstein calves were randomly allocated to 1 of 4 treatment groups(n=10).The control group was fed the basic diet(Ctrl);the SB group was fed the basic diet+30 g/d SB;the Y group basic diet+9 g/d Y;the SB+Y group basic diet+30 g/d SB and 9 g/d Y.The calves were challenged with Escherichia coli K99 at 7 days of age,and the experiment ended at d 14.The results showed that: 1)At 1 to 7 days of age,compared with the Ctrl group,the SB+Y group significantly reduced the average daily feed intake of calves(P < 0.05).2)At 11 days of age,the catalase activity in serum of calves in treatment group was significantly higher than that of the Ctrl group(P < 0.05).At 14 days of age,the catalase activity in serum of SB+Y group was significantly higher than that of the Ctrl group(P < 0.05).At 11 days of age,the glutathione peroxidase activity in serum of Y group had a tendency to increase(P = 0.088),and SB+Y group significantly increased the activity of glutathione peroxidase(P < 0.05).At 7 days of age,compared with the Ctrl group,the Y group had a tendency to reduce malondialdehyde content in serum of calves(P = 0.050).When dairy calves were under stress condition induced by challenge of Escherichia coli K99,SB and Y supplementation improved the antioxidant capacity of calves and reduce diarrhea,but it has no effect on the growth performance of calves.The combined supplementation of SB and Y improved the antioxidant capacity of calves,but reduce the average daily feed intake and increase diarrhea of calves.The mechanism needs to be further explored. |
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