Monday, June 25, 2018

Is it Okay to Draw Blood After Day 2?

Drawing blood to check on the effectiveness of the colostrum management program is an increasing common best calf management practice. But, when should the blood sample be taken? A small research project drew blood samples daily for up to 10 days to answer that question.

1. Blood samples drawn up to 9 days of age will provide reasonably reliable estimates of passive transfer immunity.

2. Blood samples drawn 24 to 48 after first colostrum feeding do result in slightly more reliable blood serum total protein (BSTP) estimates than those at 8 and 9 days of age.  

3. But, for management purposes the variation between 2 and 9 day samples is small enough so that we should not hesitate to blood sample the older calves.

I recognize that not every dairy will find it possible to draw blood on all their calves between 24 and 48 hours like I did with my calves. These data support the practice of weekly blood sampling if daily blood draws are not practical. 

Alternatively, with a small herd with monthly or quarterly assessment of colostrum management blood sampling between days 2 and 9 may allow including enough heifer calves to give useful information. 

Just for Reminders:
A. Remember that blood samples are fragile - careful handling will result in fewer broken red blood cells and more accurate estimates.
B. Keep a supply of distilled water at hand all the time - it only takes a minute or two to calibrate your refractometer; reliable readings depend on calibrated instruments.
C. Lab practice suggests that blood samples that have been held more than one day may require some extra time in the centrifuge to get full separation of blood serum.
D. If using gravity method of separation, undisturbed samples held at room temperature for approximately 24 hours will have the closest match with samples spun with a centrifuge (i.e., between 95 and 98 percent agreement).

Reference: Wilm, Jensine and Others, "Technical Note: Serum total protein and immunoglobulin G concentration in neonatal dairy calves over the first 10 days of age." Journal of Dairy Science 101:6430-6436 June 2018

No comments: