Production performance of dairy cows after the dietary addition of clinoptilolite

Clays are frequently proposed for the addition to dairy cattle diets to reduce the transfer of mycotoxins in milk. This study examined the effect of the addition of Clinoptilolite to the diet of lactating dairy cows on milk production and milk com- position. Thirty-two lactating Holstein cows (average lactation length: 142 d) were blocked according to milk production, parity, and days of lactation for assignment to one of two dietary treatments: control diet; control diet + Clinoptilolite, 200g/d. The control diet was based on corn and alfalfa silages, hay and concentrates, and did not contain aflatoxins above the safe level. The experimental period lasted 76 days. The Clinoptilolite supplementation did not affect milk yield and milk composition other than urea contents. The urea level in milk was negatively affected by Clinoptilolite addition (con- trol group 29.7 mg/100 ml vs Clinoptilolite group 31.3 mg/100ml). The dietary addition of Clinoptilolite did not change pH, ammonia content and VFA molar percentages in the rumen. No dietary effect on mineral contents of blood plasma (Na, K, Zn, and Ca) was observed. In case of clinoptilolite use in dairy cattle feeding, scarce negative effect on milk pro- duction and quality are expected