Neave and Others reported on a study that compared two treatment groups: One group received one 3 -liter colostrum replacer feeding at birth receiving a total of 200 grams of antibodies (IgG). The other group received two 3-liter colostrum feedings, one at birth (200 grams of IgG) and a second at 6 hours after birth.
 
Here are the results for the two groups at 1, 7, 14, and 28 days of age:
[we like to see serum values above 15 to show successful passive transfer]
 
            Serum Levels (mg/ml)
Day of Blood      One Feeding     Two Feedings     Increase Due to 2nd Feeding
  Draw                                                                                   (percentage)
         1                       20                        28                                  40
         7                       13                        20                                  54
       14                       11                        16                                  45
       28                         8                        11                                  38
 
Not only does the second feeding result in a 40 percent increase in IgG levels at one day but this improvement persists.
 
For those dairies giving only one feeding of colostrum replacer with a total of 150 grams, these results should suggest that there would be a significant value in changing the protocol to include a second feeding near the 6 hour threshold.
 
Reference: H. W. Neave, Z. Cocker, and D. M. Veira, "Two Feedings of Colostrum within 6 Hours of Birth Improves Serum Immunoglobulin G Levels in Dairy Calves Up To 28 Days of Age." Proceedings of Western Canadian Dairy Seminar, March, 2014.