Plasma gastrin levels in cows at various growing stages.

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Abstract
Plasma gastrin levels before and after feeding were determined by radioimmunoassay in cows at various ages. Pre-feeding levels of immunoreactive gastrin (IRG) increased with age to the maximum value (190.8 .+-. 27.0 pg/ml) in 4-month-old calves weaned immediately before and thereafter decreased gradually to adult low levels (69.1 .+-. 17.6 pg/ml). Suckling calves were fed colostrum and then whole milk at 12-hour intervals. Plasma IRG levels increased rapidly after the 1st suckling and remained high (700-1,300 pg/ml) until 42-54 hours after birth. This hypergastrinemia disappeared suddenly at 60 hours after birth and gastrin levels returned to the pre-suckling levels. In 1-month-old calves, plasma IRG levels attained at a peak value of 100-160 pg/ml 2-4 hours after suckling, and decreased gradually to 51.0 .+-. 6.7 pg/ml by the next suckling. Elevations of the IRG level after suckling were variable between 2- to 3-month-old. Weanlings were fed 3 times daily hay, haylage, and concentrated ration. In 4- to 13-month-old calves, large fluctuations occurred irrelatively to feeding. In 14- to 16-month-old calves and adult cows, IRG levels remained constant without specific post-prandial responses.