Long-Term Feeding of High Zinc Sulfate Diets to Lactating and Gestating Dairy Cows,

Abstract

Thirty dairy cows, fed a control diet consisting of silage and concentrates, were given either 0, 1000, or 2000 ppm of supplemental Zn (DM basis), from zinc sulfate monohydrate (ZnSO4.H2O) for most of a lactation. Feeding 2000 ppm Zn decreased milk yield and feed intake after several weeks. Some cows were affected more severely than others. Generally, primiparous animals were more tolerant of the high Zn diet than multiparous cows. Milk Zn was materially higher for cows fed 1000 ppm added Zn than controls. With 2000 ppm Zn, milk Zn was elevated further but returned to control values when the high Zn diet was discontinued. Plasma Zn was higher in cows fed supplemental Zn with the increase from 1000 to 2000 greater than that for the first addition. Plasma Cu was lower in cows feed 2000 ppm Zn but milk Cu was not reduced. Milk fat content was not affected, but protein and SNF were reduced by the 12th wk with the 2000 ppm Zn diet. There was no apparent effect on long-term health or performance after the cows were removed from the 2000 ppm Zn diet. Except for lower calf weights with 2000 ppm Zn, reproductive performance was not measurably affected by the dietary treatments. The 1000 ppm added Zn diet had no adverse effect on the cows in any parameter measured.

Influence of Age, Sex, and Production Class on Liver Zinc Concentration in Calves

“…Zinc concentrations in livers of calves that died from zinc toxicosis are reported to be between 144 and 510 mg/kg wet weight. 2,3,13 Calves can be more susceptible than adult cattle to zinc toxicosis, 13,25 with clinical signs of zinc including diarrhea, anorexia, pica, polyuria, polydipsia, pneumonia, cardiac arrythmias, and seizures. 14 Pathologic findings associated with zinc toxicosis in calves include diffuse bronchopneumonia, noninflammatory pancreatitis, nephrosis, hepatosis, and adrenal cortical fibrosis.…”

Remedial investigation/feasibility study of the Clinch River/Poplar Creek Operable Unit. Volume 3. Risk assessment information. Appendixes E, F

“…Anemia and pancreatitis were the major adverse effects observed in chronic animal studies (Aughey et al 1977 Livestock and small mammals are tolerant of extended dietary loadings >lo0 times the minimum recommended daily zinc requirement (Eider 1993). No adverse effects on general health or reproduction were observed in dairy cows fed 1310 mg zinckg food (Miller et al 1989). A diet of 4000-5000 mg zinckg food for 18 days resulted in fetotoxicity and poor reproduction in rats WAS 1979).…”

Effect of copper and zinc on blood and milk parameters and performance of dairy cows

“…The concentration of copper in dairy cow blood was decreased as the zinc in the diet reached 2000 mg/kg. While the zinc level is 1000 mg/kg, there was no signifi cant affect to the concentration of copper in cow blood (Miller et al, 1989). Copper and zinc are known components of SOD, and Cu seems to regulate the enzyme's activity (Paynter et al, 1979).…”