This is just a reminder that all the antibodies that go into the front of a newborn calf do not necessarily end up her blood.
In a recently reported research project calves were fed 185g of immunoglobulins (IgG) using a lactation-based colostrum replacer in either one or two feedings. [Cabrel, R.G. and Others, "Colostrum replacer feeding regimen, addition of sodium bicarbonate, and milk replacer: The combined effects on absorptive efficiency of immunoglobulin G in neonatal calves." Journal of Dairy Science 97:2291-2296 April 2014].
Absorption Efficiency - that is a measure that compares the amount of IgG fed and the amount of IgG that ends up in the blood of a calf.
The different treatments for feeding the colostrum replacer (CR) were:
  • One feeding of the 185g IgG between 30 and 60 minutes after birth [They fed 3 packages of Calf Choice Total Gold brand colostrum replacer as 3L total volume]
  • Two feedings, 123g IgG between 30 and 60 minutes after birth and 62g IgG  six hours later. [same product split into 2/3 and 1/3 feedings]
Absorption efficiency - one-feeding treatment = 31.3% efficiency
                                   two-feeding treatment = 33.7% efficiency
Conclusion: Roughly about 1/3 of IgG fed are absorbed into the blood.
These values are similar to those reported in earlier research (e.g., Quigley and Others, " Absorption of protein and IgG in calves fed a colostrum supplement or replacer." JDS 85: 1243-1248, 2002. 
There was no significant difference between one-feeding and two-feeding treatments (only 10 calves per treatment so I have some reservations about the findings)
Blood IgG levels - one-feeding treatment = 15.9 g/L (above 6.0 refractometer reading)
                             two-feeding treatment = 16.5g/L (above 6.0 refractometer reading)
When absorption efficiency was compared between calves that were fed with a bottle and those fed with an esophageal feeder there were no significant differences in absorption efficiency.
1. Equal levels of efficiency of absorption of IgG's can be achieved with either one-time or two-time feeding given that the first feeding is ASAP after birth. This reinforces findings from earlier studies.
2. Good levels of immunity as measured by IgG's in blood can be achieved by feeding a sufficient volume of IgG's (in this case 185g).
Interpretation my part - I currently recommend feeding 200g of IgG soon after birth in either one or two feedings in order to achieve the goal of successful passive transfer of immunity to 95% of the calves (that is, 95% with blood serum total protein readings at 5.0 and higher).