Prevalence of risk factors for bovine subclinical mastitis in two major dairy areas of Trinidad

Author: Lisa Benjamin, Abiodun Adesiyun ^* and Winthrop Harewood

Received 19 December 2004, accpted 11 March 2005.

Abstract

A study was conducted in two major dairy areas (Carlsen Field and Waller Field) to determine the risk factors associated with subclinical mastitis and antimicrobial residues in milk. A comprehensive questionnaire was administered to all 151 farms in both areas and used to determine the prevalent risk factors following which 5 farms each were selected from each area. A maximum of 5 milking cows per farm in early lactation were selected. The California mastitis test (CMT) was then performed on composite milk samples collected from each of the ten farms fortnightly for a period of 12-months to determine the prevalence of subclinical mastitis. Most of the farms were categorized as employing fair sanitary practices, 38 (51.4%) of 74 in Carlsen Field and 50 (64.9%) of 77 in Waller Field (P>0.05; χ²). Hand-milking, as opposed to machine-milking, was practised by most farms in both areas, 67 (90.5%) of 74 farms in Carlsen Field and 64 (83.1%) of 77 farms in Waller Field. The use of tanks for storage of water from the water service provider, was more prevalent in Carlsen Field (45.9%) than in Waller Field (29.9%) (P>0.05). Daily water shortages were reported more frequently in Carlsen Field (33.8%) than in Waller Field (5.2%) (P<0.05; χ²). In Carlsen Field, 56 (75.7%) farms routinely screened for mastitis compared with 56 (72.7%) in Waller Field (P>0.05); teat dipping was practised by 24 (32.4%) and 21 (27.3%) farms respectively (P>0.05) and the frequency of use of dry cow therapy was 63.5% (47 of 74) and 50.6% (39 of 77) respectively (P>0.05). Over the 12-month study period the prevalence of subcilinical mastitis was 17.6% (97 of 469 observations) on 6 farms with four or more risk factors for subclinical mastitis compared with a prevalence of 20.7% (97 of 469) for 4 farms with 4 or less risk factors (P>0.05). It was concluded that the interplay of various types of the risk factors present on dairy farms in Trinidad affected the prevalence of subclinical mastitis on the farms.