Estimation of the effects of buffalo fly (Haematobia irritans exigua) on the milk production of dairy cattle based on a meta-analysis of literature data

Published reports on the effect of buffalo fly Haematobia irritans exigua D e Meijere (Diptera: Muscidae) and the closely related horn fly (H. irritans ) were examined and analysed using non-linear weighted regression technique s in an attempt to establish the relationship between daily production loss (D), average number of parasites (n) and the average damage per parasite p er day (6), and to provide estimates of expected losses in milli yield (MYD ) and live-weight gain (LWG) in dairy cattle. A Mitscherlich three-paramete r model was used to explain the relationship between the total loss of prod uction attributable to buffalo flies and the average number of flies associ ated with cattle. This model was significant (P < 0.01), with R-2 = 20.2% a nd predicted a threshold number of flies (n = 30) below which no adverse ef fects would be noted. At a moderate level of infestation (n=200) d(MYD) was 2.6ml/fly/day and d(LWG) was 0.14g/fly/day, resulting in estimated daily l osses in milk yield (D-MYD) and live-weight gain (D-LWG) Of 520 mi and 28 g , respectively.