Eimeria tenella oocyst shedding and output in cecal or fecal contents following experimental challenge in broilers

摘要

Two experiments were conducted to determine whether Eimeria tenella oocyst output in cecal and fecal contents, lesion development, and performance characteristics were affected by ad libitum versus restricted feeding and challenge level. In experiment 1, 144 Cobb 500 males were placed in battery cages with 6 chicks/pen. On d 20, half of the battery pens were placed on feed restriction and all broilers were orally challenged with Eimeria tenella oocysts at one of 3 challenge levels (0, 5,000, or 20,000 sporulated oocysts). Cecal and fecal material were collected separately from d 4 postchallenge through d 10 postchallenge for oocysts output (oocysts shed/g) determination. Six days postchallenge, 3 broilers from each pen were removed and subjected to necropsy for lesion assessment. In experiment 2, 96 Cobb 500 males were placed in identical battery pens with 8 chicks/pen. On d 14, restricted feeding was initiated and broilers were challenged with Eimeria tenella oocysts at one of 3 challenge levels (1,000, 5,000, or 20,000 oocysts). Twenty-four hour collections of cecal and fecal material were obtained separately from d 4 postchallenge through d 10 postchallenge for oocysts per gram and total output determination. Six days postchallenge, 4 broilers from each pen were removed and subjected to necropsy for lesion assessment. In both experiments, BW gain was not affected by challenge dose in either the ad libitum-fed or restrict-fed broilers. Increased lesion development was observed with increasing challenge levels, and oocyst shedding peaked between d 7 and 9 postchallenge in both experiments. Oocyst concentration was higher in cecal droppings compared with fecal material throughout peak shedding; however, total oocyst output for the challenge period was similar between fecal material and cecal droppings.