Absorption of 45 Ca and 80 Sr from the Abomasum of the Calf ∗

Summary

In vivo experiments, using 12 anesthetized calves, were conducted to determine the extent of abomasal absorption of ⁴⁵Ca and ⁸⁹Sr. In two experiments, one with milk-fed calves and another with hay and grain-fed calves, a large amount of variation in absorption was noted. This was attributed to a lack of mixing of the isotope with abomasal ingesta. Variability was reduced in a third experiment by increasing the dose volume to 225 ml. An average of 20.8 ± 3.1% of an administered dose of ⁴⁵Ca and 3.2 ± 3.0% of ⁸⁹Sr were absorbed from the abomasum within 25 min. These estimates were based on the amounts of isotope recovered from ingesta and abomasal tissue of four animals and is substantiated by the rapid appearance of ⁴⁵Ca in venous blood drained from the abomasum.