| Perinatal dairy cows are affected by a series of physiological activities,such as fetal development,the upcoming delivery and lactation,resulting in the exuberant metabolism of a variety of nutrients.If the ingested nutrients can not meet the needs of the body at this time,it will easily lead to increased calcium loss and calcium homeostasis disorder,thus triggering hypocalcemia of dairy cows.Hypocalcemia will lead to negative energy balance and mineral metabolism disorders in the body,and interact with other postpartum diseases to disorder the immune system of dairy cows,and further secondary to related postpartum diseases,thus seriously affecting the health status and production performance of dairy cows,and causing serious economic losses.In this study,the incidence and influencing factors of common postpartum diseases as well as the effects of adding anionic salts in pre-perinatal diets on postpartum diseases,production performance,serum calcium balance and related blood metabolites in peripartum Holstein cows were investigated.The research included the following three parts:1.Investigation on the incidence of postpartum diseases and its influencing factors in a dairy farm in Hebei province.The incidence of postpartum diseases and deliveries of 3520 dairy cows in two farms from July 2021 to June 2022 were investigated by consulting the cattle farm archives and asking the resident veterinarians.The results showed that the incidence of postpartum endometritis(PPE,33.24%)was the highest,followed by bovine ketosis(BK,21.88%),retained fetal membranes(RFM,10.74%),mastitis(MET,7.07%),parturient paresis(PP,4.94%),and displaced abomasum(DA,2.96%);Season had significant effects on the incidence of BK,PP,DA,RFM and MET,especially the incidence increased in summer and winter.The incidences of BK,PP,DA and RFM increased significantly with the increase of fetus number.Premature delivery greatly affected the incidence of PPE and RFM,while late delivery greatly affected the incidence of BK and DA.The incidence rate of the dairy cows with normal delivery is obviously lower than that of the dairy cows with assisted delivery and dystocia;The incidence of postpartum diseases in dairy cattle whose neonatal weights were within the normal range was lower.The incidence rates of BK,PP,DA,PPE and RFM of the dairy cows which gave birth to twins increased significantly.2.Effects of anionic salts on postpartum diseases of peripartum dairy cows.A total of 382 lactating dairy cows were selected from August to September,2022.Among them,206 dairy cows in the pre-perinatal period(28 days before delivery)were treated with anionic salts in their diets as the experimental group,and the remaining 176 dairy cows were fed with normal diets as the control group.The perinatal diets of the experimental group and the control group were randomly collected and analyzed for S2-content,Na+,K+,and Cl-content and the dietary cation-anion difference(DCAD).The incidence and cure of postpartum diseases in dairy cows of the two groups were counted and the results were analyzed.The results showed that the DCAD value in the diet of experimental group was-81.02 meq/kg DM,and that in the control group was 34.19meq/kg DM.The anionic salt could significantly reduce the DCAD value in the diet(P <0.05).The incidences of BK,PP and RFM of dairy cows in the experimental group were significantly reduced,while those of DA and MET were slightly reduced,but the incidence of PPE was slightly increased,and the cure rates of BK,PP and MET were increased.3.Effects of anionic salts on performance and serum indicators of peripartum dairy cows.Thirty healthy pregnant dairy cows were selected from the experimental group and the control group respectively.Among them,the pregnancy duration,parity(2–4 fetuses),body condition,feed intake,and milk yield in the previous lactation period were similar.At 7 d prior to the pre-feeding period and 3 w during the gavage period,Collected the middle section urine within 2-3 hours after the dairy cows eat in the afternoon,and measuring the p H value;The feed amount and residual feed amount were recorded daily from 21 d before delivery to the day of delivery,and the dry matter feed intake was calculated.The body condition of each test cow was scored 28 d before birth,0 d and 28 d after calving.After calving,calving difficulty and calf birth weight were counted;The colostrum within 2 h after delivery was collected,and the daily milk secretion of dairy cows within 60 d after delivery was counted.Three milk samples were collected 28 d after delivery to analyze the milk components.Ten dairy cows were randomly selected from the experimental group and the control group respectively.When 14 d and 7 d before delivery and 0 d,7 d,14 d and 21 d after delivery,collected caudal venous blood,and serum was separated for analysis of Ca,P,Mg,and blood Glucose levels.The contents of hyperparathyroidism,1,25-dihydroxyvitamin D3,calcitonin,nonestesterified fatty acid,β-hydroxybutyric acid and Interleukin-1β in serum were determined by ELISA.Blood was collected at 5,10,and 15 d postpartum for blood ketone determination.The results showed that the p H of cow urine in the experimental group was about 6.5;postpartum feed intake recovered quickly,and the body condition score decreased due to production could be recovered more quickly(P = 0.05).The milk yield was significantly higher than that in the control group(P < 0.05),and the number of normal milk somatic cells was decreased(P < 0.01).The levels of blood Ca were significantly increased 14 days before and 7 days after childbirth(P < 0.01),but P and Mg did not change significantly(P > 0.05).The level of PTH was significantly increased from14 days before childbirth to 21 days after childbirth(P < 0.01).The levels of serum1,25(OH)2D3 were significantly increased from 14 days before childbirth to 7 days after childbirth(P < 0.05).However,there was no significant difference in CT level(P > 0.05).The contents of glucose,nonesterified fatty acid and β-hydroxybutyric acid were increased on the 0-day postpartum(P < 0.05),and Glu level was significantly lower than that of the control group on the 5,10 and 15-day postpartum(P < 0.01).In summary,the incidence of postpartum diseases in a dairy farm in Hebei Province was related to the delivery season,fetus number,pregnancy time,calving mode,calf birth weight,and single and double fetuses.Anionic salts help to stabilize blood calcium of peripartum dairy cows,down-regulate the incidence of postpartum diseases,up-regulate the cure rate,and improve serum fat metabolite levels,thereby improving production performance. |
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