[Chronic oversupply with copper as a potential herd health problem on a German dairy farm - Diagnostic value of different sample types for assessment of copper supply in dairy cows]. / Chronische Kupferüberversorgung als mögliches Bestandsproblem in einer deutschen Milchviehherde.

In contrast to sheep, chronic copper oversupply or toxicity represent infrequent events in cattle. This case report describes a chronically elevated exposure to copper arising from excessive supplementation of mineral feedstuff leading to a herd health problem in a German Holstein dairy herd. For diagnosis on herd level, 10 cows of both the close-up (VB) and high-yielding (HL) groups were selected and blood as well as urine samples were collected. Clinical chemistry investigation of these samples only revealed slightly raised activities of liver enzymes in cows of the HL group. Analysis of the total mixed ration (TMR) of both groups revealed a significant oversupply with copper, zinc, cobalt, and selenium. On the basis of these findings, the copper content of urine, feces, pigmented hair as well as plasma ceruloplasmin activity were measured additionally. Liver biopsies were performed in cows of the HL group and in heifers, the latter of which had received a mineral feed for young cattle according to the manufacturer's instructions. Results indicated increased fecal copper in both HL and VB groups as well as above normal or high-normal values of hepatic copper and cobalt resp. selenium, zinc, and manganese in the HL cows. In contrast, heifers had physiological amounts of trace elements in their liver tissues. This report demonstrates the suitability of fecal analysis and TMR for a reliable assessment of copper supply, while blood, urine, and hair failed to represent appropriate sample types. In order to attain a dependable diagnosis of potential copper oversupply, a liver biopsy - which may also be performed in buiatric practice - is deemed necessary.

Liver phosphorus content and liver function in states of phosphorus deficiency in transition dairy cows.

Phosphorus (P) deficiency in early lactating dairy cows is receiving increased attention because of incentives aiming at curtailing environmental pollution with P by reducing dietary P in ruminant diets. An in-vitro study using bovine hepatocytes incubated for 7 days with phosphate (Pi) concentrations of 0.9, 1.8 or 2.7 mmol/L, and an in-vivo study feeding late pregnant dairy cows diets with either adequate (0.28% and 0.44% in DM ante-partum and post-partum respectively) or low P content (0.15% and 0.20% in DM ante-partum and post-partum respectively) from 4 weeks before to 4 weeks after calving were conducted to explore effects of P deprivation on liver function. In vitro the relative abundance of mRNA of key enzymes of the carbohydrate metabolism in incubated hepatocytes and liver metabolites in culture medium were determined. In vivo health and productivity of experimental cows on low and adequate dietary P supply were monitored, and liver tissue and blood samples were obtained repeatedly. Liver tissue was assayed for its triacylglycerol-, mineral and water content as well as for the relative abundance of mRNA of enzymes of the carbohydrate-, fat- and protein metabolism. Reduced Pi-availability was not associated with altered enzyme transcription rates or metabolic activity in-vitro. The most prominent clinical finding associated with P deprivation in-vivo was feed intake depression developing after the first week of lactation. Accordingly cows on low P diets had lower milk yield and showed more pronounced increases in liver triacylglycerol after calving. Although the liver P content decreased in P deficient cows, neither negative effects on enzyme transcription rates nor on blood parameters indicative of impaired liver metabolic activity or liver injury were identified. These results indicate the P deprivation only indirectly affects the liver through exacerbation of the negative energy balance occurring as P deficient cows become anorectic.