A previous article about commercially available colostrum substitutes has spawned questions about natural colostrum from a cow that lost a calf or from a dairy cow. An important factor that influences colostrum quality (immunoglobulin concentration) is the age of the cow. Heifers have poorer quality colostrum while older cows have the best quality colostrum. Another very important factor is milking stage. In general, colostral immunoglobulin concentration is halved with each successive milking, therefore the first milking colostrum has twice the immunoglobulin content of the second milking colostrum. Colostrum leakage and premilking both adversely influence colostrum quality. Purchasing colostrum from other farms should be done with caution. Diseases such as Johne’s Disease may be transmitted from one operation to another via colostrum.
Cow calf producers are aware that natural colostrum must be ingested by baby calves within 6 hours of birth to acquire satisfactory passive immunity. However some calves do not have ample opportunity to receive colostrum. Perhaps the mother is a thin two-year-old that does not give enough milk or the baby calf was stressed by a long delivery process and is too sluggish to get up and nurse in time to get adequate colostrum. These calves need to be hand fed stored colostrum in order to have the best opportunity to survive scours infections and/or respiratory diseases.
Colostrum can be refrigerated for only about 1 week before quality (immunoglobulin or antibody concentration) declines. If you store colostrum, unfrozen be sure that the refrigerator is cold (33-35°F, 1-2°C) to reduce the onset of bacterial growth. If the colostrum begins to show signs of souring, the quality of the colostrum is reduced. The immunglobulin (very large protein) molecules in colostrum that bring passive immunity to the calf will be broken down by the bacteria, reducing the amount of immunity that the colostrum can provide. Thus, it is important that colostrum be stored in the refrigerator for only a week or less.
How long can the frozen colostrum be stored? We often answer this question flippantly by saying, "just as long as you would store frozen fish to eat!" Colostrum may be frozen for up to a year without significant breakdown of the immunoglobulins. However this is one example where improved technology is not in our favor. Frost-free freezers are not the best for long-term colostrum storage. They go through cycles of freezing and thawing that can allow the colostrum to partially thaw. This can greatly shorten colostrum storage life. Freezing colostrum in 1 quart in 1 or 2 gallon zip-closure storage bags is an excellent method of storing colostrum. Many producers have had great success using the zip-closure bags. Use two bags to minimize the chance of leaking, and lay them flat in the freezer. By laying the bags flat, the rate of thawing can be increased, thereby reducing the delay between time of calving and feeding. The freezer should be cold (-20°C, -5°F) - it's a good idea to check your freezer occasionally. Much more information about colostrum use and transfer of passive immunity is available from the OSU Fact Sheet F-3358 Disease Protection of Baby Calves.