Abstract
Bunching is the term used to describe the protective aggregating behavior of cattle against the painful bites of stable flies (Stomoxys calcitrans), where cattle gather in a group with their heads to the center of the group and their tails to the outside to reduce stable fly attack. Both sexes of the stable fly feed on blood, and their painful bites negatively impact cattle health, productivity and welfare. A longitudinal study was conducted from April to July 2017 to estimate the stable fly activity on 20 California dairies (average herd size = 2466 ± 1050), to determine stable fly activity that induced bunching, and to evaluate the association between management and environmental factors, and cattle bunching. Stable fly activity was recorded weekly using trap counts and leg counts. Data was analyzed using linear mixed models with odds ratio. Cattle bunching at the dairy level was predicted by mean trap counts of ≥150 flies/trap/week, while bunching at the pen level was predicted by mean leg counts >1 fly/leg/cow or mean trap counts >50 flies/trap/week for traps closest to the pen. Additional risk factors predicting cattle bunching at the dairy level were study week (May/June vs July), presence of crops adjacent to dairy >2 sides, and feeding wet distillers grain. Additional risk factors predicting cattle bunching at the pen level were study week (May/June vs July), ambient temperature ≤30°C, pen design (freestall vs open dry lot or bedded pack), production status (lactating/dry vs close-up), presence of crops surrounding cattle pens, feeding rations containing molasses. Cattle bunching was reduced at the pen level by relative humidity >50%, and when the cattle pen was surrounded by other cattle pens or was bordered by a main road. At the dairy level, removal of manure along fence lines of cattle pens was protective against cattle bunching.
Highlights
Stable flies (Stomoxys calcitrans) are biting flies that feed on blood leading to high stress and elevated cortisol levels which may impact cattle health, productivity and welfare [1]
Cattle tend to aggregate in a tight group with their heads to the center of the group and their tails to the outside to protect themselves against the stable fly attack displaying a behavior known as bunching [12,13,14,15]
We examined the effect of environmental and management factors on California dairy farms that were associated with cattle bunching behavior
Summary
Stable flies (Stomoxys calcitrans) are biting flies that feed on blood leading to high stress and elevated cortisol levels which may impact cattle health, productivity and welfare [1]. Stable flies tend to bite the lower parts of the body such as the legs and abdomen, irritating cattle and provoking individual or group behavioral changes to repel or avoid the fly attack. Cattle might differ in how aggressively they engage in flyrepelling behaviors according to their breed, color, parity, productivity, and the number of stable flies attacking them [9,10,11]. Cattle tend to aggregate in a tight group with their heads to the center of the group and their tails to the outside to protect themselves against the stable fly attack displaying a behavior known as bunching [12,13,14,15]
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