Colostrum from Pastured Irish Cows
I had the opportunity to review an article published in 2013 (M. Conneely et al., "Factors associated with the concentration of immunoglobulins in the colostrum of dairy cows." The Animal Consortium 7:11 1824-1832) that focus on a population of Irish cows. These cows were quite different from USA cows reported in the work of Morrill, et al. ("Nationwide evaluation of quality and composition of colostrum on dairy farms in the United States" Journal of Dairy Science 95:3997-4005 2012).
In contrast to the confinement-housed U.S. cows with year-round calving this Irish population had seasonal calving and was managed in a grass-based system. The US National Agricultural Statistics Service reported average milk production of 20,400 pounds (305 days) in USA (2010). This Irish cow population managed on a grass-based system had an estimated milk production of 11,600 pounds (305 days). Due to missing data in the Morrill report it is not possible to compare cow populations by breed and parity.
- Colostral IgG concentration - wide variation in both populations. Irish low = 13g/l USA low =<1.8g/l Irish high = 256g/l USA high = 200g/l
- Colostral IgG mean value much higher among Irish cows compared to USA cows. Irish mean = 112g/l USA mean = 69g/l.
- Colostral IgG tended to go up by lactation in both populations.
Lactation - values are grams/liter
1 2 3&greater
Irish 97 99 115
USA 42 69 96
If I was asked by an Irish dairy farmer about how much colostrum to feed newborn calves given this high quality colostrum my recommendation (based on antibodies delivered) would be 2 liters as soon as possible after birth. Given the wide variation among dams, however, I would still recommend using a Brix refractometer or Colostrometer to check antibody concentration before feeding the calf. More than 2 liters of lower quality colostrum might be a better practice to achieve adequate immunity.
The Irish study also found that cows milked closer to calving consistently had higher IgG values than those milked with a longer calving-milking interval - longer 9 hours post-calving among these cows seemed to be a break point indicating lower quality.