The effect of management on mastitis incidence in dairy cows in Qwaqwa

Abstract

A study on the effect of certain management practices on mastitis incidence in dairy cows in the QwaQwa area situated in the north-eastern region of the Free State Province was undertaken during the period of November and December 2003. The study had the following main objectives: To study the level of the mastitis problem and farmers’ knowledge regarding mastitis control on dairy farms in QwaQwa; and to determine the effect of somatic cell count (SCC) on milk components. An individual questionnaire was used to collect data from sixty randomly selected small-scale dairy farmers. A total of 120 lactating cows from 30 selected farms were examined for SCC using the California mastitis test (CMT) kit in the farms and Fossomatic counter machine in the laboratory. The purpose of the questionnaire survey was to gather information on the farm and its management practices, while clinical examination using the Fossomatic machine and CMT screening was used to determine mastitis prevalence. The average age of the participant farmers was 55±13 (SD) years. Only 28% of the farmers had a secondary or tertiary level of education. The average dairy herd size was 39 ±36 (SD) animals. The cows in milk constituted 36% of the herd, while the remainder were dry cows (14%), heifers (16%), calves (30%) and bulls (4%). When farmers were grouped into their daily milk production capacity, 57% reported producing 1 to 50 litres, 20% 51 to 100 litres, and 23% more than 100 litres per day. Only 8.3% of the farmers reported having experienced mastitis problems. The average clinical mastitis cases reported per farm per year were 1.6±1.6 (SD) cases. The average incidence rate of clinical mastitis was 18.5% (calculated as the number of clinical cases divided by the number of cows in milk). As expected, the mastitis cases reported by small-scale dairy farmers showed a positive association with the number of cows in the herd. The incidence of mastitis reported for 1 to 50 litres, 51 to 100 litres and approximately 100 litres daily milk production groups was 20.5%, 24.7% and 8.1% respectively; however, the difference between the groups was not significant due to a large number of sampling errors. No other management practices - such as having a separate milking parlour, washing hands and teats before milking, and using disinfectant on teats - had an influence on the mastitis incidence reported by farmers. On average, the concentration of fat, protein, lactose and SNF in milk was 4.41%, 3.40%, 4.87% and 8.66% respectively. With the exception of parity, all other factors studied (breed, daily milk yield, and udder, rear leg and parlour cleanliness) did not have a significant influence on SCC, TPC, and CMT score (P>0.05). The SCC ranged from 198.8 ± 1.4 (cells/ml) for the Jersey breed to 400.3 ± 1.4 (cells/ml) for the Brahman breed. Both SCC and positive CMT increased (P<0.01) from first to fourth parity. Amongst milking management factors, washing of hands made a significant difference (P<0.05) to CMT and TPC count. No other management and animal-related factors studied had an influence on milk components (P>0.05). There was significant positive correlation between SCC and CMT score (r = 0.6). Somatic cell count and CMT produced showed significant negative correlations (r=-0.4; r=-0.37 and r=-0.4; r=-0.39) with lactose and SNF.