Subchronic Administration of Technical Pentachlorophenol to Lactating Dairy Cattle: Performance, General Health, and Pathologic Changes

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Abstract
Technical grade pentachlorophenol [herbicide] (PCP) was fed subchronically to lactating dairy cattle to establish whether exposure approximating farm environments containing substantial PCP-treated wood represented a hazard to animal health. Holstein cattle (4) in early lactation were fed 0.2 mg PCP/kg body wt per day for 75-84 days followed by 2 mg PCP/kg body wt per day for 56-60 days. Each treated cow was paired with a control cow of equivalent stage of lactation. Milk production, feed intake and body weight were not affected by doses except that treated cattle were more efficient converters of feed to milk during the early stage of the 2 mg/kg period. Milk fat production and somatic cell count in milk were not affected by exposure to PCP. Postmortem examination revealed enlargement of liver, lungs, kidneys and adrenals and thickening of the urinary bladder wall. Chronic interstitial nephritis and subacute urocystitis were the major pathologic changes in PCP-treated cattle. In vitro testing of kidney slices confirmed significant loss of renal function. The relationship of lesions to PCP administration was not clear.