Study On Effects Of 25-Hydroxyvitamin D₃ On Mid-Lactation And Transition Dairy Cows And Calves

At present,dairy industry in our country is facing many challenges,among the most serious problems are that hypocalcemia in postpartum cows and diarrhea in calves,which not only affect health and performance of dairy cows and calves,and seriously restricts the development of dairy industry in our country,so it is urgent to develop a safety and effective way to improve health of transition cows and calves.As an important nutrient,the main role of vitamin D₃ is to regulate the absorption and metabolism of calcium and phosphorus,especially in the bone health and reproductive performance of livestock.This study first investigated the effects of25-hydroxyvitamin D₃ on regulation of calcium and phosphorus,lactation performance and health status of mid-lactation dairy cows,so as to determine the appropriate dosage for dairy cows.This study further investigates the effects of feeding 25-hydroxyvitamin D₃ combined with oral calcium on hypocalcaemia,colostrum quality,lactation performance and health of transition dairy cows,and then investigates the effects of maternal feeding 25-hydroxyvitamin D₃ on the health and growth performance of their offspring calves.In addition,the effects of inclusion of25-hydroxyvitamin D₃ in milk replacer on growth and weaning stress are further evaluated.It is of great significance to improve the health and performance of transition cows and calves,and to promote the development of dairy industry in China.Experiment 1:Effects of 25-hydroxyvitamin D₃ on performance and health of mid-lactation dairy cowsThe objective of this study was to evaluate the effects of 25-hydroxyvitamin D₃ on the lactation performance,blood metabolites,and antioxidant and immune function in dairy cows.Thirty-six mid-lactation Holstein dairy cows were selected according to day in milk,milk yield and somatic cell counts and were randomly assigned to 3 treatments.Treatments were a basal diet plus 0 IU,40 000 IU or 120 000 IU 25-hydroxyvitamin D₃ per cow per day throughout a 9-week trial period.Milk were sampled at day 0,21,42 and 63 for milk composition analysis.Blood were sampled for blood metabolites,parameters of antioxidant and immune fu nction at day 0,21,42 and63.The results showed that dairy cows fed 25-hydroxyvitamin D₃ showed linear increases（P<0.05）in milk yield,energy-corrected milk,milk protein and lactose yield and a decrease in somatic cell counts in milk（P<0.05）.Feeding 25-hydroxyvitamin D₃ linearly increased serum total Ca,P,25-hydroxyvitamin D₃ and 1,25-dihydroxyvitamin D₃ and had no negative effect on blood biochemical parameters and energy metabolites（P>0.10）.Additionally,dietary 25-hydroxyvitamin D₃ linearly increased（P<0.05）total antioxidant capacity,total superoxide dismutase,glutathione peroxidase,immunoglobulin G and linearly decreased（P<0.05）malondialdehyde and tumor necrosis factor-α.The results showed that feeding 120 000 IU 25-hydroxyvitamin D₃ daily can effectively improve lactation performance,blood calcium,phosphorus and 25-hydroxyvitamin D₃levels,antioxidant capacity and immune function of mid-lactation dairy cows.Experiment 2:Effects of feeding 25-hydroxyvitamin D₃ combined with oral calcium on transition dairy cowsThe objectives of the current study were to evaluate the effects of 25-hydroxyvitamin D₃combined with oral calcium on colostrum quality,lactation performance,serum minerals and vitamin D₃ metabolites,blood biochemistry,antioxidant and immune function in multiparous dairy cows.To evaluate the effects of 25-hydroxyvitamin D₃ combined with oral calcium,48multiparous Holstein cows due for 21 days were randomly assigned to 1 of 4 treatments:（1）supplementing 120 000 IU/day vitamin D₃ without a postpartum oral Ca bolus（Control）;（2）supplementing 120 000 IU/day vitamin D₃ with an oral Ca bolus containing 90 g of Ca immediately postcalving（VD+Ca）;（3）supplementing 120 000 IU/day 25-hydroxyvitamin D₃without an oral Ca bolus（25D）and（4）supplementing 120 000 IU/day 25-hydroxyvitamin D₃ with an oral Ca bolus containing 90g of Ca immediately postcalving（25D+C a）.Colostrum and lactation performance during the first 21 days were measured.Blood were collected at the initiation of calving and then day 1,2,7,14,and 21 relative to the calving date.The yield of milk（P=0.06）,energy-corrected milk（P=0.05）,3.5%fat-corrected milk（P<0.05）and milk protein（P<0.05）were higher in 25-hydroxyvitamin D₃-treated groups within 3 weeks than in vitamin D₃-treated cows.Feeding 25-hydroxyvitamin D₃ significantly increased the levels of calcium and phosphorus,25-hydroxyvitamin D₃ and immunoglobulin G in colostrum（P<0.05）.The i Ca（P<0.05）and t Ca（P<0.05）were higher in both Ca and 25D+Ca cows than in the control and 25D groups within 48 h.The concentrations of serum t Ca（P<0.05）,t P（P<0.05）and 25-hydroxyvitamin D₃（P<0.05）in25D and 25D+Ca cows were higher than those in control and Ca cows within 21 days postpartum.Feeding 25-hydroxyvitamin D₃ also showed a lower concentration of malondialdehyde（P<0.05）,interleukin-6（P<0.05）and tumor necrosis factor-α（P<0.05）and higher concentration of alkaline phosphatase（P<0.05）,total antioxidant capacity（P<0.05）and immunoglobulin G（P<0.05）than vitamin D₃.Supplementing Ca bolus also showed lower concentrations of alanine tra nsaminase（P<0.05）and tumor necrosis factor-α（P<0.05）.The results showed that feeding25-hydroxyvitamin D₃ combined with oral calcium can significantly improve lactation performance,antioxidant capacity and immune function of dairy cows,and effectivel y prevent the occurrence of hypocalcaemia.Experiment 3:Effects of maternal feeding 25-hydroxyvitamin D₃ on their offspring calvesThe objective of this study was to investigate the effects of maternal feeding25-hydroxyvitamin D₃ on growth performance,blood 25-hydroxyvitamin D₃ and mineral levels and biochemistry,antioxidant and inflammatory parameters,as well as fecal short-chain fatty acids,microbial community composition and diversity induces of their offspring calves.This experiment is carried out on the basis of experiment 1.Offspring calves were fed colostrum and six transition milk which were only from their dams.The body weight and body structure of calves were measured at day 0,15 and 30,and blood was collected at the same time for analys is.In addition,feces were collected at day 30 for analysis of fecal short-chain fatty acids,bacterial community and diversity induces.The results showed that maternal feeding 25-hydroxyvitamin D₃significantly increased the body weight（P<0.05）and withers height（P<0.05）,and significantly reduced（P<0.05）the diarrhea of their offspring calves.Maternal feeding 25-hydroxyvitamin D₃significantly increased（P<0.05）serum 25-hydroxyvitamin D₃,calcium and phosphorus of their offspring calves at birth and 15 days of age.Maternal feeding 25-hydroxyvitamin D₃ significantly increased the IgG obtained from colostrum（P<0.05）,and increased the serum IgG level of calves within 48 h after birth（P<0.05）.Compared with maternal feeding vitamin D₃,maternal feeding25-hydroxyvitamin D₃ significantly increased the activity of catalase（P<0.05）and decreased tumor necrosis factor-α（P<0.05）of their offspring calves at 15 days of age.Maternal feeding25-hydroxyvitamin D₃ significantly increased fecal propionic acid（P<0.05）and butyric acid（P<0.05）.The relative abundance of Bacteroidaceae and Christensenellaceae were significantly increased（P<0.05）in offspring calves born by cows fed 25-hydroxyvitamin D₃.The results showed that feeding cows with 25-hydroxyvitamin D₃ significantly improved growth performance,serum levels of calcium,phosphorus and 25-hydroxyvitamin D₃,and immunoglobulin G concentration of calves.Experiment 4:Effects of different forms of vitamin D₃ in milk replacer on growth performance and weaning stress of calvesThe objectives of this study were to evaluate the effects of milk replacers contain ed25-hydroxyvitamin D₃ and enriched with vitamin D₃ on the growth performance,fecal scores,vitamin D₃ metabolites,biochemical blood parameters and antioxidant,inflammatory and stress-related parameters of Holstein male calves.Thirty Holstein male calves（body weight=41.4±2.79 kg）were randomly assigned to three groups for a 56-day experimental period.The control group received milk replacer containing 600 IU/kg vitamin D₃,the VD group received milk replacer containing 6 600 IU/kg vitamin D₃,and the 25D group received milk replacer containing 300 mg/kg 6 000 IU/kg 25-hydroxyvitamin D₃ plus 600 IU/kg vitamin D₃ until weaning at day 54.On day 52,57 and 59,which were defined as day-2,3 and 5 postweaning,blood samples were collected to measure biochemical blood parameters and antioxidant,inflammatory and stress-related indicators.Calves that received milk replacer containing 25-hydroxyvitamin D₃consumed more calf starter at one week postweaning（P<0.01）than those in the control and VD groups.Calves in the VD and 25D groups had a significantly（P=0.02）greater average daily gain than calves in control during the overall period.Calves in th e VD and 25D groups had greater body weight and withers height on day 60 than calves in the control group.Calves fed25-hydroxyvitamin D₃ displayed lower fecal scores and incidence of diarrhea overall periods.Calves fed 25-hydroxyvitamin D₃ increased serum 25-hydroxyvitamin D₃ during the preweaning（P<0.0001）and postweaning（P<0.0001）periods.Abrupt weaning increased concentrations of total protein,glucose,cholesterol,t Ca and t P.Calves fed 25-hydroxyvitamin D₃ had a higher t Ca（P=0.04）and t P（P=0.02）concentrations than those fed other diets.Weaning stress significantly decreased the catalase concentration and increased the malondialdehyde concentration,and calves fed 25-hydroxyvitamin D₃ displayed higher glutathione peroxidase and catalase and lower malondialdehyde concentrations during the weaning period.Weaning also significantly increased the cytokine contents,including interleukin-1,interleukin-6 and tumor necrosis factor-α,and stress indicators,including cortisol and haptoglobin.Significantly lower cytokines（interleukin-6 and tumor necrosis factor-α）and stress indicators（cortisol and haptoglobin）contents were observed in calves fed 25-hydroxyvitamin D₃ than those in VD and control groups at day 3 and 5 postweaning.The results showed that feeding 25-hydroxyvitamin D₃ significantly increased growth performance,decreased diarrhea,increased serum calcium,phosphorus and 25-hydroxyvitamin D₃,and improved antioxidant capacity,inflammatory factors and stress levels of calves after weani ng.In summary,this study drew the following conclusions:（1）Dietary 25-hydroxyvitamin D₃ increased milk yield and improved serum minerals,25-hydroxyvitamin D₃ levels,and antioxidant and immune function of dairy cows.（2）Feeding transition cows with 25-hydroxyvitamin D₃ combined with oral calcium bolus improved colostrum and lactation performance,Ca homeostasis,and antioxidant an d immune function of dairy cows,effectively prevented hypocalcemia in postpartum dairy cows.（3）Maternal feeding 25-hydroxyvitamin D₃ improved the levels of serum 25-hydroxyvitamin D₃,calcium and phosphorus of their offspring calves,which is conducive to develop healthy calves.（4）Feeding milk replacer with 25-hydroxyvitamin D₃ had the potential to improve the growth performance,promote bone development,decrease diarrhea and reduce weaning stress by enhancing the antioxidant capacity and decreasing the pro-inflammatory and stress indicators of calves.