Research On Critical Control Points Of Colostrum Quality And Feeding Mode In Medium-sized Dairy Farms In Shandong Province

Newborn calves have low immunity,poor resistance to external environment,and high morbidity and mortality.The placenta structure of cows is special,so newborn calves can not directly obtain maternal immunity from cows through placenta,but can only obtain passive immunity by feeding colostrum after birth.Therefore,colostrum feeding is the key link of newborn calf feeding.Existing studies have shown that whether calves can successfully obtain passive immunity is closely related to colostrum quality and feeding mode.The relevant standards or specifications for colostrum feeding of calves have been formulated and published successively,and have been promoted and used in large-scale intensive breeding farms,achieving good results.However,in medium-sized dairy farms,due to the relatively backward level of feeding management,the complicated colostrum feeding standards are difficult to implement,resulting in low passive immunization success rate of newborn calves,and high morbidity and mortality,which brings great economic losses to the farms.Therefore,it is urgent to further define the key control points of colostrum quality control and feeding mode,simplify feeding procedures,and develop colostrum quality and feeding management mode suitable for medium-sized dairy farms,so as to improve the passive immunization success rate of newborn calves and reduce economic losses.Firstly,four medium-sized dairy farms in Shandong province were investigated and found that colostrum quality and feeding management were not standardized.Then,we randomly selected one dairy fam as a case study,and conducted a one-month investigation and statistics on colostrum management,feeding pattern,transfer of passive immunity（TPI）effect,calf body weight（BW）,morbidity and mortality.for one month.The main problems were found as follows: the time of colostrum collection was not fixed;Colostrum quality was not detected,temporary feeding and temporary squeezed.Colostrum is not pasteurized;Colostrum feeding time was not fixed,and only 61.22% of calves were fed colostrum within2 h.The proportion of calves fed 2 L colostrum was the highest（46.89%）,and 34.69% of calves were not fed colostrum（replaced by mixed milk）.Passive immune transfer failure rate（36.73%）and incidence（63.27%）were high.In view of the above problems,we standardized management and application of colostrum quality and feeding mode in this cattle farm,evaluated the application effect,and finally determined the critical control points.To standardize colostrum quality,four tests were carried out.（1）Twenty-eight healthy third parturient holstein cows were randomly divided into 4 groups.Colostrum was collected immediately after postpartum,3-6 h postpartum,7-9 h postpartum and 10-12 h postpartum,respectively,and the effects of collection time on colostrum quality and quantity were observed.The results showed that the IgG content of colostrum collected from cows within12 h postpartum was high quality colostrum（IgG > 50 mg/mL）;With the delay of collection time,IgG content in colostrum decreased gradually,but the difference was not significant（P > 0.05）.（2）Seven healthy preparturient Holstein cows from 1 to 6 parities were randomly selected and colostrum was collected immediately after delivery.There was no significant difference in colostrum quality between parities（P > 0.05）;Colostrum amount in the first trimester was significantly lower than that in the second trimester（P < 0.05）,but there was no significant difference between the first trimester with the 3rd,4th and 5th parities（P >0.05）.（3）Eight healthy pre-parturition Holstein cows were randomly selected.Colostrum was collected immediately after delivery and IgG changes at different stages of colostrum collection were observed.5 L colostrum was collected from each cow and 1 L/ tube was used to detect IgG content changes in each tube.The results showed that there was no significant difference in IgG content among colostrum stages（P > 0.05）.（4）Twenty healthy pre-parturition Holstein cows were randomly selected.Colostrum was collected immediately after delivery and pasteurized（60°C for 60min）to observe the effect on colostrum.The results showed that there was no significant difference in IgG content and milk composition of colostrum before and after pasteurization（P > 0.05）,but the total bacteria count and escherichia coli content in colostrum were significantly decreased（P < 0.001）.These results suggest that the colostrum of healthy cows within 12 h of calving is all qualified colostrum,and the earlier the collection time,the higher the IgG content;Colostrum should also be pasteurized.In order to establish the colostrum feeding mode suitable for this farm,the passive immunity effect of three colostrum feeding modes was compared.Thirty-six newborn calves with similar body weight were randomly divided into 3 groups with 12 calves per group.The control group was the original colostrum feeding mode.In experimental group A,calves were fed with 4 L qualified colostrum within 2 h after birth and 2 L qualified colostrum after12 h.In test group B,calves were fed with 3 L qualified colostrum within 2 h after birth and another 2 L after 12 h.Serum was collected 24-48 h after birth to detect serum IgG content.The results showed that there was no significant difference in serum IgG content between experimental group A（14.83 ± 0.69 mg/mL）and experimental group B（15.42 ± 0.73mg/mL）（P > 0.05）,and the serum IgG content of group A and B were significantly higher than control group（10.31 ± 0.92 mg/mL,P < 0.001）.In the control group,5 calves had passive immune failure（serum IgG < 10 mg/mL）,accounting for 41.67%.The passive immune transfer of calves in experimental groups A and B was all successful.The incidence and mortality of calves were 33.33% and 8.33% respectively in the control group and 8.33%and 0% respectively in experimental groups A and B.In conclusion,the results of this study suggest that passive immunization of newborn calves can be successfully achieved by pasteurization of colostrum collected from healthy cows within 12 h of calving and feeding at least 3 L of colostrum within 2 h of birth and 2 L of colostrum after 12 h interval.