Performance and anticoccidial effects of nicarbazin-fed broilers reared at standard or reduced environmental temperatures.

A series of 4 floor pen studies was conducted to evaluate the effects of environmental temperature modification on nicarbazin (NIC) responses in broiler chickens raised to 28 d of age. Birds were reared at either standard temperatures (recommended by the primary breeder for ages zero to 28 d) or at 3°C below this level. From placement to 28 d, birds were provided feeds containing zero, 100, or 125 ppm NIC, comprising a 2 × 3 factorial arrangement in each test. Two of the trials were conducted in the presence of an imposed coccidial challenge and 2 were conducted in healthy animals. At 18 and 28 d of age, performance was recorded; cloacal temperatures were measured at 7, 14, 21, and 26 days. Mortality data were collected daily and coccidial lesions were scored at 6 d post challenge. Results of these studies revealed that NIC improved coccidial lesion scores regardless of environmental temperature. In the absence of coccidial challenge, NIC depressed performance, but reductions in environmental temperature diminished the magnitude of these responses. Under conditions of coccidial challenge, NIC significantly improved body weight gains in both temperature environments. Compared to standard temperature conditions, lower environmental temperatures exerted a positive effect on feed conversion rates of NIC-fed broilers. Birds reared in the low temperature environment exhibited lower cloacal temperatures than standard environment groups throughout the test period. Irrespective of coccidial challenge, lower environmental temperatures significantly reduced nicarbazin mortality compared to standard temperature groups, resulting in a significant nicarbazin x temperature interaction. This finding indicates that temperature modification is a practical method for minimizing mortality over the course of 28-day nicarbazin usage.

Sensitivity of Eimeria field isolates in the United States: responses of nicarbazin-containing anticoccidials.

A series of studies were conducted to assess the drug sensitivity of 26 coccidial field isolates to the anticoccidial effects of nicarbazin (NIC) and narasin + NIC (NAR + NIC). Isolates were collected from typical broiler farms in the United States from 2003 to 2006, propagated once in the absence of anticoccidial medication, and then used to inoculate broilers that were fed nonmedicated rations or those containing NIC 125 ppm or NAR + NIC 80 ppm. Results of these sensitivity trials indicated that 81% of these coccidial isolates were sensitive to the effects of NIC, but only 22% of these coccidia were controlled by NAR + NIC. Studies conducted to evaluate performance responses to these drugs demonstrated that birds fed NIC gained more weight and utilized feed more efficiently than those receiving NAR + NIC. The results of 2 floor pen tests, conducted to confirm the results of the above sensitivity trials, demonstrated that NIC provided a greater level of protection from coccidiosis than NAR + NIC. Lower lesion scores and improved performance were recorded for birds receiving NIC compared with NAR + NIC. Results of these studies revealed that changes in the susceptibility of Eimeria spp. to the activity of NAR + NIC are evident. These changes appear to be associated with the reduction in ionophore sensitivity that has been documented in most areas of the world.

The influence of withdrawal time on the performance of broiler chickens fed semduramicin.

Three 49-d experiments, with a total of 6,528 male broiler chicks in floor pens, were conducted to test the hypothesis that Semduramicin feeding-time affects the body weight gain, feed consumption, and feed conversion ratio of broilers. Semduramicin ionophore was added to corn and soybean meal-based diets at the recommended level, 25 mg/kg for 0,34,39, or 42 d. Thus, three withdrawal times were employed (7, 10, and 15 d) during each experiment. Significant differences among experiments were observed for body weight gain, feed intake, and feed conversion ratio, but no significant differences due to Semduramicin were noted in body weight or feed intake. There was only one treatment by experiment interaction found for 0-to-34-d feed intake (P = 0.028), but it was not evident for 0 to 39 d (P = 0.818) or any other times. Feeding Semduramicin with a 10- or 15-d withdrawal period resulted in an improvement in feed conversion of about 0.04 units.

Studies on semduramicin and nutritional responses: 2. methionine levels.

Three experiments were conducted to determine whether feeding semduramicin at recommended levels would affect the broiler chicken's response to dietary methionine. In Experiment 1, three levels of methionine (0, 0.15, 0.30%) were fed to chicks in battery brooders. In Experiment 2, two levels of protein (18 and 22%) and three levels of methionine (0, 0.15, 0.30%) were fed to chicks in floor pens from 18 to 44 d. In Experiment 3, two methionine supplements were fed during each of the starter (0 and 0.21%, 0 to 18 d) and grower (0 and 0.10%, 18 to 35 d) periods to chicks in floor pens. In all experiments, male commercial broiler chicks were used, and all diets were fed with and without 25 mg/kg diet of semduramicin. The basal diets were based on corn, soybean meal, and poultry oil. In Experiment 1, there was a growth and feed conversion ratio response to methionine supplements, but there was no effect of semduramicin on growth nor any semduramicin by methionine supplement interaction. In Experiment 2, at 44 d, protein and methionine levels both influenced feed conversion ratios, but semduramicin did not. Feeding 22 vs 18% protein increased carcass and breast muscle yields and decreased abdominal fat pad weights. The results of Experiments 2 and 3 were very similar. Overall, the effects of semduramicin on growth and processing parameters were small and not significant, but considerable benefits in performance and carcass parameters could be realized by feeding the higher levels of protein or methionine.

Studies on semduramicin and nutritional responses. 1. Level and source of protein.

An experiment was conducted to determine whether feeding semduramicin at recommended levels (25 mg/kg) would affect the broiler chicken's response to dietary protein; and to determine whether protein source (all vegetable, corn and soybean meal, vs 12% high animal protein ingredients) would affect the response to semduramicin. Semduramicin was fed to half of 1,584 male Ross x Ross broilers in floor pens during the growing phase (18 to 35 d). Three protein fortification levels were also fed with protein and amino acid minimum restrictions at 80, 100, and 120% of NRC (1994) recommendations. At 35 d, semduramicin was found to cause a slight growth depression in body weight gain only when low protein levels were fed (P = 0.051). After a 7-d withdrawal period, compensatory gains occurred (P = 0.006) such that there was no interaction effect of semduramicin by protein level for 42-d body weight (P = 0.75). Birds fed the diets containing high animal protein were slightly heavier than those fed control diets containing all-vegetable protein (2.40+/-0.02 vs 2.36+/-0.01 kg/bird; P = 0.059). Semduramicin feeding did not affect feed consumption (2.43+/-0.03 vs 2.40+/-0.02 kg per bird during the growing period when it was fed) so that overall feed conversion ratios were identical to two decimal places (1.90+/-0.02 vs 1.90+0.02). Neither did semduramicin affect feathering score or weight of the No. 8 primary feather, except that feather weight tended to be improved by semduramicin feeding with the diets containing ingredients high in animal protein (P = 0.067).

Dietary and monensin effects on activity of hepatic microsomal mixed function oxidase system in chickens.

Four experiments were conducted to investigate if the degree of activation of the microsomal mixed-function oxidase (MFO) system was related to the degree of growth depression associated with the addition of monensin to the diet. The experiments were conducted with broiler chicks in battery brooders in which the chicks were fed diets of various composition and containing monensin at 0 to 160 ppm. In all experiments, the activity of the MFO system was estimated by the change in the content of cytochrome P-450 in the hepatic microsomes. Activities of some microsomal enzymes were also measured in some of the experiments. Feeding a diet with 24% protein containing fish meal, alfalfa meal, and torula yeast significantly increased the activity of the MFO system in comparison with feeding an isonitrogenous and isoenergetic corn and soybean diet, but there was no difference between the diets in the toxicity of monensin as measured by growth rate. Supplementing a 16% protein but not a 24% protein diet with monensin significantly reduced growth rate. In none of the four experiments was there a statistically significant change in the hepatic content of cytochrome P-450 as a result of feeding monensin. Thus, variation in the magnitude of growth depression caused by monensin in diets of different protein concentration or ingredient composition does not appear to be explained on the relative degree of the activation of the MFO system.

Staphylococcus-induced gangrenous dermatitis in broilers.

An infectious bursal disease (IBD)-vaccinated flock of 23,900 broilers, 17 days of age, experienced sudden onset of depression, dermatitis, and mortality. Postmortem examination showed extensive subcutaneous serosanguineous fluid accumulation over the pectoral muscles, discrete hepatic whitish foci, fluid-filled intestines, and small, flaccid bursae of Fabricius. Gram-stained impression smears from the affected areas revealed numerous gram-positive cocci. Aerobic culture of liver and subcutaneous tissue consistently produced heavy growth of penicillin-sensitive Staphyloccus aureus. Histopathologically, subcutaneous tissue showed diffuse hemorrhage and large numbers of gram-positive cocci with severe congestion and hemorrhage of the underlying skeletal muscle. Liver sections showed multiple, randomly scattered areas of acute coagulation necrosis with numerous gram-positive cocci. Bursal lesions were characterized by extensive follicular necrosis and collapse. A diagnosis of staphylococcal gangrenous dermatitis secondary to IBD was made. Mortality returned to preinfection levels within 72 hours after penicillin was added to the drinking water.

Interaction of monensin with dietary vanadium, potassium, and protein, and its effect on hepatic rubidium and potassium in chicks.

A series of experiments was undertaken to further investigate the influence of diet composition on chick response to monensin supplementation. Experiments were conducted to determine the effect of monensin on growth rate and hepatic Rb and K content as affected by dietary content of V, K, or protein. A factorial experiment involving V levels of 0, 5, 10, or 20 ppm and monensin levels of 0, 120, or 160 ppm was conducted with broiler chicks to 4 weeks of age. Growth rate was significantly depressed by 10 or 20 ppm V but not by monensin. Hepatic K content was not affected by dietary treatments. In another factorial experiment, effects of levels of 0 and 120 ppm monensin and 0 and 5 ppm V were compared. Growth rate was significantly depressed by both V and monensin but with no significant interaction. Neither hepatic Rb or K content was significantly altered by the supplements. A third factorial experiment involved monensin levels of 0, 120, or 160 ppm, added K levels of 0 or .3%, and dietary protein levels of 16 or 24%. Body weight at 3 weeks of age was significantly depressed by 160 ppm monensin in the high protein diet and by 120 or 160 ppm in the low protein diet. Added K did not counteract the growth depression. Hepatic Rb content was increased by monensin and significantly reduced by K supplementation. Hepatic K content was not increased by K supplementation. Chicks fed the low protein diet had significantly lower concentrations of hepatic Rb and K than those fed the high protein diet.

Activation of hepatic microsomal mixed function oxidase system in broiler chicks by diet changes.

Two experiments were conducted to investigate the effect of diet composition on activity of the microsomal mixed function oxidase (MFO) system in broiler chicks. One-day-old chicks were fed for 10 days either a corn-soy (CS) diet or diets supplemented with a combination of fish meal, alfalfa meal, and torula yeast (FAY) or individually with fish meal (FM), alfalfa meal, distillers dried grains with solubles (DDGS), or torula yeast (TY). Activities of hepatic microsomal aniline hydroxylase and aminopyrine N-demethylase were increased when chicks were fed FAY, FM, TY, or DDGS compared with those fed CS. In another experiment chicks were fed the CS and FAY diets to 4 weeks of age. Hepatic microsomal cytochrome P-450, cytochrome b5, and activities of aniline hydroxylase and aminopyrine N-demethylase were significantly increased in birds fed the FAY diet. Activities of NADPH and NADH-cytochrome C reductase were not affected. These results show that the hepatic microsomal MFO system is activated by changes in diet composition and suggest that this activation may be responsible for reducing estradiol and liver lipid levels when similar diets are fed to laying hens.

Liver lipid content in broilers as affected by time without feed or feed and water.

The purpose of this study was to determine if length of time of feed withdrawal of broilers prior to slaughter could affect the lipid content of their livers. Seven-week-old male broilers were allocated to three treatments: 1) no feed and water, 2) no feed, and 3) feed and water ad libitum. Those in the first treatment were held in plastic coops and those in the latter two treatments were kept in floor pens. Eight birds were randomly sampled initially and eight birds from each treatment at 4, 8, 12, 16, and 24 hr after the start of the study. The birds were weighed, killed, and the livers removed and analyzed for lipid content. The regression slopes of the two treatments without feed for body weight, liver weight, liver weight per unit body weight, and liver fat per unit body weight were significantly different from the control treatment. The slopes for liver fat were not significantly different among treatments. No obvious differences in the gross appearance of the livers were detected. The occasional problems with fatty livers in commercial broilers apparently cannot be accounted for by the length of time of feed withdrawal before slaughter.