Thus the kids depend on the colostrum as their source of antibodies, providing passive immunity until they are developing their own active immune system. The period in which the immunoglobulins can be absorbed through the kid's GI tract lasts 3 to 4 days in goats. Beyond this time, the digestive enzymes in the gastrointestinal tract of the kid will break down the protein structures of the antibodies, rendering them ineffective. The high percentage of these immunoglobulins in colostrum, along with albumin, gives it its thick, sticky consistency. 20 Globulin, having a high proline content, is also important for the formation of hemoglobin in the young kid.
Normal milk is much lower in globulin levels, having instead a higher level of casein.
The functional importance of casein is that it is the only milk protein forming a curd upon coagulation in the abomasum thereby creating a slower moving food reserve for the young kid. The dry matter content of colostrum is much higher than in normal milk, primarily due to the large amount of proteins, especially albumin and globulins. The colostral content of iron is generally about 15 times greater than in normal milk, while vitamin A and vitamin D levels are about 10 and 3 times those of normal milk. 22 Colostrum or milk bypasses the reticulorumen area because of the formation of the esophogeal groove, thus preventing the milk from laying in the rumen and turning rancid, which would then develop scours. The formation of this groove is in response to the sucking reflex of the young kid.