Calcium Metabolism in Lactating Goats as Studied with Ca45 Following Oral and Intravenous Administration

Authors:
  • WVW.J. Visek
    W.J. Visek
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Abstract
Only a limited amount of research has been reported relative to calcium metabolism of the lactating ruminant as measured with Ca 45. Aten and tIeyn (3) studied the rate of Ca 4~ secretion into the milk of a lactating goat following subcutaneous injection of a solution of Ca45C12. Err and Pecher (8) gave tracer doses of radiostrontium to two dairy cows and followed its rate of secretion into the milk. Tracer quantities of radiostrontium and radiocalcium have been shown to behave qualitatively the same in other species (10, 14, 25, 26, 27). Normal non-pregnant lactating goats were selected for experimentation in these studies. Goats offered opportunity of providing pilot information for subsequent research with dairy cows without requiring as much radioactive material for comparative measurements. Additional advantages were low cost and ease of handling. Presented in this paper are results of experiments showing the distribution of Ca 45 in the blood, milk, urine and feces as a function of time following oral and intravenous administration of single doses of the radioisotope. Data also are included to show the effects of stage of lactation on the above distribution pattern following oral administration. GENERAL METttODS All experiments were carried out in an experimental nutrition barn. I~einforced pans of heavy galvanized metal were placed on the barn floor and all equipment connected with these studies including the metabolism cages was kept in these pans in order to localize the radioactivity. Individual metabolism cages were designed to separate the urine and feces as they were voided. All animals were confined to the metabolism cages at least 5 days prior to administration of the labelled dose. Their legs, necks and underline were closely clipped to reduce chances of radioactive contamination. For 2 wk. following dosing, the milk and excreta not required for analyses were collected and buried. Recommendations of Asdell and Marquardt (2) were followed in caring for the animals. Allowances of digestible nutrients for maintenance and milk production were calculated according to the recommendations of Gaines (11). This schedule was followed at least 1 too. prior to administration of the radioactive material." The level of feeding was established at least 5 days prior to dosing and renmined unchanged for the duration of the balance period which followed. Hay was chopped and fed after the grain. The animals were fed before milking,

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