$sup 65$Zn metabolism, secretion into milk, and biological half-life in lactating cows
Following oral dosing, zinc-65 metabolism was studied in 10 first- lactation Holstein cows during the 5th and 6th wk of an experiment in which a high beet pulp, low-zinc diet (16.6 ppM) was fed without and with (39.5 ppM total zinc) supplemental zinc. For the 14 days after dosing, cows fed low zinc had a much higher net zinc-65 absorption (53.4 versus 34.8%) and consistently secreted far more zinc-65 into milk (14.4 versus 6.3%). The zinc secreted into milk of cows fed low zinc during the 14 days had been in the body a shorter time than in controls, indicating greater dependences on recently consumed zinc for secretion into milk, The biological half-life (in lactating ruminants defined as the time required for one-half of the zinc-65 dose to leave the body via feces and milk) was shorter for the cows fed low zinc. Lactating cows are able to absorb a high percentage of dietary zinc, and lactation is a major factor in zinc metabolism and homeostasis. Major changes in zinc metabolism occur before performance is affected. (auth)
- Research Organization:
- Univ. of Georgia, Athens
- NSA Number:
- NSA-29-016070
- OSTI ID:
- 4387624
- Journal Information:
- J. Dairy Sci., v. 56, no. 12, pp. 1526-1530, Other Information: Orig. Receipt Date: 30-JUN-74
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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