ARS | Publication request: Use of modified cages attached to growing calves to measure the effect of stable flies on dry matter intake and digestibility, and defensive movements

Submitted to: Professional Animal Scientist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 22, 2010
Publication Date: April 1, 2011
Citation: Schole, L.A., Taylor, D.B., Brink, D.R., Hanford, K.J. 2011. Use of modified cages attached to growing calves to measure the effect of stable flies on dry matter intake and digestibility, and defensive movements. Professional Animal Scientist. 27(2):133-140.

Interpretive Summary: The effects of stable flies on calves were studied by attaching cages with flies to the animals. Weight gain, amount of feed eaten, digestion of the feed, and behavioral responses were examined. Caged stable flies successfully fed on the calves and invoked defensive behaviors similar to those observed in field studies. The number of defensive movements increased relative to the number of stable flies. Stable flies did not affect the ability of the calves to digest their feed. Exposure to stable flies increased the amount of food the calves ate and reduced their ability to convert food into weight gain. Calves learned defensive behaviors during the course of the study and eventually became proficient at preventing the flies from feeding. However, the affects of stable flies on feeding and feed conversion to weight remained even when very few successfully fed upon the calves. Calves initially exposed to high numbers of stable flies exhibited more defensive movements, ate less, and gained less weight than those exposed to gradually increasing numbers of flies. The reduced productivity of cattle when exposed to stable flies appears to be caused by the calves behavioral responses rather than physiological responses.

Technical Abstract: The effect of stable flies on growing calves was examined using modified fly cages attached to the animals. Dry matter intake and digestibility as well as behavioral responses of the animals were monitored. Nine Holstein calves, individually housed in 3 x 3 m pens, were exposed to three levels of stable flies (0, 10, 100 flies/animal 3 times daily (900, 1200, 1500 h) for 30 min intervals. The study consisted of a 4 period crossover design; each period included 5-d adaptation, 7-d treatment, and 5-d post-treatment. Calf weights were taken on d 1 and d 17 of each period. Feed consumption was continuously recorded. Fecal samples taken on d 5, 6, 7, 12, 13 were used to determine dry matter digestibility (DMD). Three calves were monitored for activity and behavior during exposure. Caged stable flies successfully fed on the calves invoking defensive behaviors similar to those observed in field studies. Defensive behaviors were proportionate to the number of flies and calves became more proficient at interfering with fly feeding over time. Calves exposed to stable flies had higher DMI relative to their weight than those not exposed. Stable flies decreased ADG/DMI of the calves. Calves initially exposed to the 100 fly treatments exhibited more defensive behaviors, lower relative DMI, and ADG across all exposure levels relative to those calves exposed to the 10 fly treatment prior to the 100 fly treatment. Stable fly exposure did not affect DMD, number of meals, time eating, or amount eaten per meal. Host defensive behavior, not reduced DMI or DMD, appear to be the major factors reducing ADG of calves exposed to stable flies. Results indicate that cages placed on calves may be used to study effects of stable flies, but host exposure history and behavioral variables must be considered.