Metabolic and hormonal responses of growing modern meat-type chickens to fasting.

1. The present study compared the effects of fasting on circulating concentrations of glucose, insulin and glucagon in male and female modern meat-type chickens (Ross 708) at three ages (19 d, 33 d and 47 d). 2. Plasma concentrations of glucose were reduced by fasting with reductions of 24.9% (19-d-old), 22.6% (33-d-old) and 17.9% (47-d-old) in broiler chickens fasted for 12 h. 3. Plasma concentrations of insulin decreased with fasting. For instance, circulating concentrations of insulin declined after 6 h of fasting by 45.7%, 54.7% and 50.0%, respectively, in 19-d-old, 33-d-old and 47-d-old broiler chickens. 4. Plasma concentrations of glucagon were increased by fasting. Plasma concentrations of glucagon were elevated by 3.79% (19-d-old), 3.51% (33-d-old) and 3.79% (47-d-old) with 6 h of fasting and remained elevated with 12 h, 18 h and 24 h of fasting.

Changes in body temperature during growth and in response to fasting in growing modern meat type chickens.

1. Rectal or core body temperature was determined in a study to examine the effects of fasting in modern meat type broilers at three stages of growth, namely d 19, 33 and 47. 2. There were two treatment groups: fed with feed available ad libitum and fasted. Rectal temperatures were determined at noon (1200 h). At that time, feed was removed from the fasted group. The body temperatures were then determined again after 6, 12, 18 and 24 h. 3. Core body temperatures decreased with fasting. The decrease was evident after as little as 6 h of fasting with a further decline evident by 12 h. 4. Accompanying the decrease in body temperature with fasting there were decreases in the venous concentrations of carbon dioxide in the blood and sodium in the plasma. 5. The decrease in both body temperature and carbon dioxide presumably reflects depressed metabolic rate. 6. Unexpectedly, the core body temperature increased progressively with age in the control fed group (d 19 = 41·04 ± 0·02°C, d 33 = 41·65 ± 0·05°C, d 47 = 42·21 ± 0·12°C). 7. In the fed control group, core body temperatures were reduced at night, when feeding activity would be anticipated to be greatly reduced.

Interactive effects of ammonia and light intensity on hematochemical variables in broiler chickens.

This study examined the influence of early atmospheric ammonia exposure, light intensity throughout rearing, and their interaction on blood gases, electrolytes, and acid-base balance in broiler chickens under environmentally controlled conditions. The experiment consisted of a 3 x 3 factorial arranged in a randomized complete block design, with trials being replicated over time. The 9 treatments consisted of 3 levels (0, 25, and 50 ppm) of ammonia concentrations for 14 d and levels (0.2, 2.0, and 20 lx) of light intensities from 8 to 36 d of age. Venous blood samples were collected on d 6, 11, 14, and 35. On d 6, partial pressure of CO2 and Na+ increased significantly (P

The effects of broiler catching method on breast meat quality.

Mechanical and hand catching of broilers (n=24 per treatment for each trial) were performed to determine if differences existed in breast meat quality among catching methods. Two trials (summer and winter 2005) were conducted, and it was determined that there was greater variation in meat quality in the summer in comparison to the winter within treatments in both catching methods. Neither catching method yielded breast meat with significant quality issues. Therefore, either catching method should be acceptable for catching broilers in respect to meat quality. However, mechanical catching and crating for 2h yielded slightly better (P<0.05) quality meat than hand catching in respect to averages and individual quality problems. These slight improvements in meat quality included higher (P<0.05) 15min pH, lower (P<0.05) drip loss, and lower (P<0.05) incidence of pale meat with a rapid pH decline in the summer.

Evaluation of models using corticosterone and adrenocorticotropin to induce conditions mimicking physiological stress in commercial broilers.

Three experiments (Exp) were conducted to delineate a suitable model for inducing conditions mimicking physiological stress with minimal bird handling. For Exp 1, Ross x Ross 308 male chicks were fed a control diet or a diet containing 5 mg of corticosterone (CS)/kg from d 1 to 7. For Exp 2, Ross x Ross 508 broilers received 1 of 4 dietary treatments: control; control + 4 IU/kg of BW of adrenocorticotropin (ACTH)/d i.m. from d 21 to 27; control + 8 IU/kg of BW of ACTH/d i.m. from d 21 to 27; or control + 15 mg of CS/kg of diet for 14 d from 21 to 35 d of age. In Exp 3, Ross x Ross 308 broilers were fed high or low nutrient density (ND) from 1 to 41 d of age, and 0 or 20 mg of CS/kg of diet from 18 to 21 d of age. Performance parameters (BW gain, feed intake, feed conversion, and mortality) were measured in all 3 experiments. In Exp 1, CS administration significantly decreased BW gain and decreased feed intake and mortality. In Exp 2, although ACTH injection resulted in significantly depressed performance responses relative to the control, CS administration yielded significantly stronger results. In Exp 3, ND and CS interacted (P = 0.04) to affect feed intake from d 0 to 34. Broilers fed diets containing high ND and CS had higher feed intake than broilers fed low ND and CS. From 0 to 21 and 0 to 42 d, CS decreased feed intake. Increased dietary ND improved BW gain and feed conversion in Exp 3. Also, CS decreased and increased BW gain and feed conversion, respectively, during all periods in Exp 3. Dietary addition of CS negatively impacted performance of broilers, and increasing dietary amino acid density did not ameliorate these effects.

Electrolyte diets, stress, and acid-base balance in broiler chickens.

We compared the acid-base balance in broiler chickens provided diets containing 2 dietary electrolyte balances (DEB), and administered with either adrenocorticotropic hormone (ACTH) or saline solution. Diets were moderate (174 mEq/kg) or high (241 mEq/kg) DEB formulated by altering Na-K-Cl based on actual analysis. The experiment was designed as a split plot, with the main unit consisting of 4 treatments and the factorial treatment structure arranged in a completely randomized design. Osmotic pumps delivered 8 IU of ACTH in saline/kg of BW per d for 7 d, or the same saline volume as used in ACTH at 1 microL/h for 7 d was implanted on d 35. Venous blood samples were collected on d 35 before the pumps were implanted and on d 42 and 49. Birds fed the high DEB diet exhibited significantly higher Na(+) and Ca(2+) levels than birds provided the moderate DEB diet on d 35. Infusion of ACTH significantly increased (P < or = 0.05) hematocrit, hemoglobin, partial pressure of CO(2) (pCO(2)), corticosterone, osmolality, and HCO(3)(-) and reduced pH, BW, partial pressure of O(2) (pO(2)), and plasma concentrations of Na(+) and Cl(-) in both diets compared with the control group on d 42. Similarly, the ACTH treatment significantly increased hematocrit, hemoglobin, Ca(2+), corticosterone, and osmolality and reduced (P < or = 0.05) pO(2), glucose, and BW on d 49. The diet formulated for high DEB partially lowered pCO(2) on d 42. Significant DEB x ACTH interactions were observed for pCO(2) and pO(2) on d 49. However, there was a reduction in pO(2) along with a concomitant increase in erythropoiesis under the ACTH treatment for both diets, compared with the saline control, because of the increased need for O(2) to support gluconeogenic energy production. This adaptive response provided greater numbers of erythrocytes and thus a higher amount of circulating hemoglobin to deliver O(2) for metabolism. The diet formulated for high DEB partially attenuated the adaptive stress condition in broiler chickens.

The effect of corticosterone-induced stress on amino acid digestibility in Ross broilers.

Two experiments (Exp.) were conducted to establish amino acid (AA) digestibility coefficients (DC) for broilers given corticosterone (CS)-induced stress using the apparent ileal digestibility assay. For Exp. 1, 192 Ross x Ross 708 male broilers were placed into 16 floor pens (12 birds/pen). For Exp. 2, 120 Ross x Ross 308 male broilers were placed into 10 floor pens (12 birds/pen). Pens contained nipple drinkers, pan feeders, and soft-wood shavings. Both experiments were completely randomized designs using pen as the experimental unit. In both experiments, chicks were given a common starter diet from d 1 to 20. From d 21 to 30, broilers were provided a control diet or the control + 15 mg of CS/kg of diet dissolved in soybean oil (8 and 5 replications/treatment in Exp. 1 and 2, respectively). Diets were based on corn (65.07%) and soybean meal (26.36%) and contained an indigestible marker (chromic oxide 0.3%). Diets were formulated to contain 3,175 kcal of ME, 18.5% CP, 0.79% digestible TSAA, and 1.00% digestible Lys. Stress validation was accomplished by measuring BW gain, feed intake, and liver weight on d 30. Evidence that stress occurred was apparent due to the fact that broilers fed CS had lower BW gain and higher liver weight than those fed control. On d 30, the ileal contents were removed from 3 birds/pen, pooled, dried, and analyzed for AA content. Amino acid DC were calculated using the following equation: DC = 100 -(dietary marker % x ileal AA %) / (ileal marker % x dietary AA %) x 100. Amino acid digestibility did not differ (P > 0.05) between treatments in either experiment. Based on this research, future research should be directed at establishing DC for other nutrients in stressed broilers or the effect of different nutrients on the stress response.

Stress and acid-base balance in chickens.

Two trials were conducted to study the effects of continuous infusion of adrenocorticotropic hormone (ACTH) on acid-base balance in broiler chickens. Osmotic pumps delivered 8 IU of ACTH in saline/kg of BW/d for 7 d or the same saline volume as used in ACTH at 1 microL/h for 7 d. Blood samples were taken on d 0 (baseline values) and on d 4, 7, and 14 after onset of the infusions. The ACTH treatment increased the hematocrit, partial pressure of CO2, anion gap, corticosterone, mean corpuscular hemoglobin concentration, the blood concentrations of hemoglobin and HCO3-, and reduced the partial pressure of O2, plasma concentrations of Na+, K+, and Cl-. Blood pH values and plasma concentrations of Ca2+ were unaffected by ACTH treatment. The ACTH infusion also resulted in a significant increase in plasma glucose, cholesterone, high-density lipoprotein, and triglyceride. There were no differences in any of the blood constituents measured from control groups. Results indicate that infusion of ACTH resulted in changes in plasma acid-base status along with changes in other blood metabolic variables. However, the ACTH treatment did not prevent homeostatic regulation of acid-base balance, as indicated by constant blood pH. There was, however, an increased need for O2 to support gluconeogenic energy production; the birds responded by increased erythropoiesis. This adaptive response provided greater numbers of erythrocytes and thus a higher amount of circulating hemoglobin to deliver O2 for metabolism.

Changes in tissue nitrite concentration in the crop of the turkey poult in response to Salmonella typhimurium challenge.

The present study examines whether Salmonella typhimurium colonization of the crop of young turkeys influences nitrite concentration in the component tissues of the crop. Nitric oxide (NO) is the principal compound in biological samples that is converted into nitrites and NO is known to be a component of the early host response to infection. Challenge with S. typhimurium increased the concentration of nitrite in the crop wall of 3-wk-old turkey poults. The magnitude of the response was reduced at 8 h and absent at 48 h after challenge. As would be expected, S. typhimurium concentrations in the crop were markedly increased following challenge, and were nondetectable in control poults.

Stocking density and physiological adaptive responses of broilers.

Three trials were conducted to assess the effects of stocking density on physiological adaptive responses of broilers. Male broilers were reared in floor pens under conditions similar to those used commercially in the United States. Accepted indicators of adaptation to a stressor were measured on d 49 including plasma concentrations of corticosterone, glucose, cholesterol, and total nitrites as an indicator of nitric oxide, as well as heterophil:lymphocyte ratio. In trial 1, calculated stocking densities were 20, 25, 30, 35, 40, 45, 50, and 55 kg of BW/ m2 and in trials 2 and 3, stocking densities were 30, 35, 40, and 45 kg of BW/m2. Stocking densities were calculated based on a final BW of 3.3 kg. Linear trend analyses were used to assess the role of stocking density on each of the physiological parameters. Results indicate that stocking density did not cause physiological adaptive changes indicative of stress.

Physiological stress in laying hens.

Stress responses in laying hens were mediated by continuous infusion of adrenocorticotropin (ACTH) via osmotic pumps. The ACTH was dissolved in saline solution (0.85%), and each pump delivered 8 IU of ACTH per kilogram of BW per day at the rate of 1 microL/h for 7 d. Control hens received pumps loaded with saline. Measurements were made at 6 d postpump implantation, unless otherwise indicated. The ACTH-treatment increased BW and total carcass, rear half of carcass, intestinal, and liver weights. Proximate analyses of liver showed increases in dry weight, moisture, protein, fat, carbohydrate, and ash content. Weights of the front half of the carcass, as well as weights of the abdominal fat pad, heart, head, feet, and skin were unaffected by ACTH-treatment. Plasma corticosterone, glucose, cholesterol, and high-density lipoproteins were increased by ACTH, whereas triglycerides were decreased. Feed and water intake, total excreta, and excretory DM were all increased in ACTH-treated hens. The ACTH decreased carbohydrate in excreta, whereas ash, protein, fiber, and gross energy of excreta were unaffected. The ACTH did not affect digestibility of dry matter, proteins, carbohydrates, fats, or gross energy; however, absorption of ash, protein, carbohydrates, and gross energy were increased by ACTH. Antibody levels to sheep red blood cells, cell-mediated immunity (wattle index to phytohemagglutinin-phosphate), and relative spleen weight were reduced by ACTH, whereas heterophil:lymphocyte ratio was increased. Reproduction in hens was negatively affected by ACTH treatment, as measured by cessation of laying on the third day of treatment, atretic follicles, and decreased oviduct weight.

Stocking density effects on male broilers grown to 1.8 kilograms of body weight.

This study examined the effects of stocking density on live performance, physiological stress level indicators, and processing yields of male broilers grown to 1.8 kg. A total of 3,120 Ross x Ross 708 male chicks was placed into 32 floor pens (5.57 m2/pen). Stocking density treatments were 25, (75 birds/pen), 30 (90 birds/ pen), 35 (105 birds/pen), and 40 (120 birds/pen) kg of BW/m2. The BW gain, feed consumption, and feed conversion were adversely affected with increasing stocking densities by 35 d. Physiological stress indicators (plasma corticosterone, glucose, cholesterol, total nitrites, and heterophil:lymphocyte) were not affected. Litter moisture was higher as stocking density increased, which led to higher footpad lesion scores. In parallel to growth responses, carcass weight was depressed by increasing stocking density, but carcass yield, absolute and relative amounts of abdominal fat, and carcass skin defects were not affected. Increasing stocking density decreased breast fillet weight and its relative yield and breast tender weight, but not breast tender yield. As calculated stocking density increased 5 kg of BW/m2 beyond 25 kg of BW/ m2, final BW and breast fillet weight decreased by 41 and 12 g, respectively. We conclude that increasing stocking density beyond 30 kg of BW/m2 adversely affects growth responses and meat yield of broilers grown to 1.8 kg but does not alter physiological stress indicators.

Dietary tryptophan effects on growth and stress responses of male broiler chicks.

1. Three experiments were conducted to determine growth of broiler chicks fed on test diets formulated to be deficient or adequate in tryptophan (Trp) using gelatin by-product as a means of generating a Trp deficiency. Growth response estimates of broiler chicks to graduations of Trp were determined by dose-response criteria and regression analyses. Experiments were conducted using broiler chicks from 1 to 20 d of age. 2. Broiler chicks fed Trp-deficient diets had poor body weight gain, feed intake and feed conversion. Recommended total Trp needs were 2.0, 2.1 and 2.2 g/kg for feed intake, body weight gain and feed conversion, respectively. 3. Blood plasma Trp exhibited a sigmoidal trend while blood plasma glucose increased in a linear manner to supplemental Trp. Physiological stress variables measured were unaffected by dietary Trp.

Stocking density effects on growth performance and processing yields of heavy broilers.

This study examined responses of male broilers during a 49-d production cycle to 4 placement densities in 2 trials. Trials were pooled because no treatment x trial interaction occurred. In each trial, 1,488 male chicks were randomly placed into 32 floor pens to simulate final densities of 30 (37 chicks/pen), 35 (43 chicks/ pen), 40 (50 chicks/pen), and 45 (56 chicks/pen) kg of BW/m2 of floor space based on a projected final BW of 3.29 kg. Growth rate and nutrient utilization were similar (P > or = 0.05) among the treatments from 1 to 32 d of age. From 1 to 49 d, BW gain (P = 0.011) and feed consumption (P = 0.029) were adversely affected by increasing the placement density from 30 to 45 kg of BW/m2 of floor space. The reduction in cumulative BW gain due to placement density can be partially explained by less feed consumption as evidenced by 95.4% of the sums of squares of BW gain being attributable to feed consumption. Litter moisture content (P = 0.025) and foot pad lesion score (P = 0.001) increased linearly with increasing placement density. Upon processing, whole carcass and breast meat yields relative to BW were not affected (P > or = 0.05) as density increased from 30 to 45 kg/m2. The proportion of whole carcasses with scratches, but not tears, on the back and thighs increased (P = 0.021) as density increased. These results indicate that increasing the density beyond 30 kg/m2 elicited some negative effects on live performance of heavy broilers.

Pulmonary hypertension syndrome in young chickens challenged with frozen and autoclaved cultures of Enterococcus faecalis.

Enterococcus faecalis, when administered in a growth medium or sterile saline, will cause pulmonary hypertension syndrome (PHS) in chickens. The objective of this study was to determine if frozen and/or autoclaved cultures of E. faecalis retain ability to evoke PHS. In Trial 1, chicks were inoculated with 3.6 x 10(7) E. faecalis (IA) in tryptic soy broth (TSB) from either a live culture or one that had been autoclaved (120 degrees C for 20 min). Controls received TSB. Autoclaved and live cultures produced the same degree of PHS in a majority of the birds. Trial 2 used the same protocol, except a frozen (-70 degrees C for 60 min) culture of E. faecalis was compared with the control. The results agreed with those of Trial 1, i.e., the frozen culture also produced PHS. Trial 3 was conducted to determine if E. faecalis caused PHS by producing and releasing some unknown substance into the supernatant. Incidence of PHS was based on percentage of birds exhibiting ascites fluid at 24 hr after challenge. Controls received sterile, frozen, or autoclaved TSB. As compared with controls, those birds that received challenge with E. faecalis alone, supernatant alone, and E. faecalis plus supernatant from live cultures exhibited similar incidence of ascites, whereas birds that received E. faecalis plus supernatant and supernatant alone from cultures that had been either frozen or autoclaved exhibited elevated incidence of ascites as compared with controls. Also, with frozen and autoclaved cultures, those birds that received only pelleted E. faecalis exhibited incidence of ascites that did not differ from controls. Apparently, E. faecalis produces PHS in chicks by producing and releasing an unknown toxin.

Heart growth in broilers.

1. Morphological development of the heart in fast-growing, meat-type fowl of both sexes was studied. 2. In 4 experiments, fowl were weighed, killed and hearts were dissected at 0, 20, 34, and 48th d of age. Heart weight (HW), length (HL), diameter (HD), and thickness of the right ventricular wall (RVW) and left ventricular wall (LVW) were determined. 3. This is the first description of sexual dimorphic differences in the heart of fowl. 4. Results indicate that males have greater HW, HL, and LVW thickness than females. However, thickness of the RVW during the embryonic period, as indicated by thickness of the RVW at hatching in females, exceeds that of males.

Growth promotion in chickens by interleukin-2.

Chicken interleukin-2 (cIL-2), which was prepared by sensitizing chicken lymphocytes with concanavalin A, was administered to fertile broiler eggs on Day 18 of embryonation (0.1 mg in 200 mL distilled water). Controls (CON) received distilled water. Hatched chicks were reared to 6 wk. Body weight (BW), as well as abdominal fat pad, liver, bursa of Fabricius, a thymic lobe, spleen, and gonads were excised and expressed relative to BW at 2, 4, and 6 wk of age. Additionally, hematocrit (HCT), hemoglobin (HGB), and plasma protein (PP) levels were determined at the three time intervals. Finally, chicks were sensitized against human gamma globulin (HGG) and challenged at 6 wk by intradermal injections into the wattles. Delayed type hypersensitivity (DTH) to HGG was used as a direct measure of cell-mediated immunity. In ovo cIL-2 increased BW consistently, relative fat pad weights at 2 wk, relative bursa and liver weights at 2 and 6 wk, HBG and relative thymic weight at 2 and 4 wk, and PP at 2 wk. Delayed type hypersensitivity to HGG was not affected by cIL-2. Potential metabolic and immunologic mechanisms to explain in ovo cIL-2 effects are discussed.

Bacteria in heart and lungs of young chicks.

AIMS: The purpose of these experiments was to determine whether the heart and lungs of young chicks harboured bacteria. METHODS AND RESULTS: Samples of the heart and lungs were aseptically removed from chicks on scheduled sampling days. Experiment 1 showed that of the 360 birds evaluated during the late embryonic and early post-hatching periods, only 10.8% harboured bacteria in the heart, lungs, and heart and lungs simultaneously. Experiment 2 suggested that bacteria in these organs were transient. Twenty-three bacterial species were found in the hearts whereas 30 were found in the lungs. Experiment 3 showed that only 1.4% of embryos harboured bacteria in the yolk, albumen, heart and lungs whereas 12.9% of the embryos had bacteria in the air cell. CONCLUSIONS: During the post-hatching period, there was a higher incidence of bacterial isolation in the heart and lungs, whilst during the embryonic development period, there was a lower incidence of bacterial isolation from these two organs. Results suggested that the heart and lungs do not have a residual bacterial flora; rather, opportunistic bacteria occasionally pass through these tissues. SIGNIFICANCE AND IMPACT OF THE STUDY: These experiments proved that bacteria could be isolated in the heart and lungs of healthy chicks reared from E17 to 3 weeks of age.

Morphological changes in heart and lungs of broilers experiencing pulmonary hypertension syndrome caused by Enterococcus faecalis.

In a previous report, a method of identification of birds experiencing early symptoms of pulmonary hypertension syndrome (PHS) caused by challenge with Enterococcus faecalis was delineated. This method involved subjective heart scores based on visual observation of a cavity on the external surface of the right ventricular wall (RVW), as well as tonicity and thickness of this wall. Accuracy in identifying birds 48 h postchallenge with E. faecalis was acceptable. However, this method did not attempt to offer other morphological or physiological characteristics for further understanding the etiology of PHS. In the present study, three trials were conducted to establish morphological characteristics of the heart from birds challenged with E. faecalis. In Trials 1 and 2, discrepancies were found in heart length (HL) and thickness of the RVW. In Trial 3, the dry weight of the right ventricle (RV) increased after challenge with E. faecalis, as was the ratio of the mass of the RV to the mass of the total ventricle (TV). Histopathological evidence of hearts and especially lungs of birds challenged with E. faecalis were suggestive of PHS. Results indicated that RV, RV:TV ratio, and histopatholgical evaluation of heart and lungs are complementary to diagnosis of PHS.

Biochemical and immunological changes in chickens experiencing pulmonary hypertension syndrome caused by Enterococcus faecalis.

Recent studies have proven that Enterococcus faecalis (1.5 x 10(7) live bacteria from a tryptic broth culture given s.c. or intra-abdominally (IA) to 5-wk-old broilers) caused pulmonary hypertension syndrome (PHS) in 97% of the birds within 48 h. Definitive diagnosis of PHS was made at necropsy by observing a cavity on the surface of the right ventricular wall and by increased ratio of left ventricular weight to total ventricular weight. A nonlethal method of diagnosing PHS would enhance the study of PHS and alert production poultrymen to the onset of ascites (waterbelly), which is the cuLminating event of PHS. In the present study, serum hemoglobin, glucose, protein, cholesterol, aspartate amino transferase (AST) and creatine kinase-MB (myocardial in origin) enzymes, differential leukocyte numbers, and specific antibody levels against Ent. faecalis were evaluated as nonlethal diagnostic indicators of PHS. Decreases in serum protein and cholesterol of 3 and 10%, respectively, plus increases in percentages of basophils and monocytes of 18 and 40%, respectively, appear to indicate that PHS has been initiated. An agglutinating antibody, specific against Ent. faecalis, but not against other closely related bacteria, has been developed. Presence of this antibody in a bird means that the bird has previously encountered Ent. faecalis. Thus, this antibody may become a diagnostic for PHS in fast-growing chickens.