Biomedical subjects

D M Denbow

Publications and source records attributed to D M Denbow.

At least 55 records · Page 3Linked to original sources

PubMed1995

Improving phosphorus availability in soybean meal for broilers by supplemental phytase.

A 21-d experiment was conducted with day-old male broilers (n=840) to evaluate the effectiveness of supplemental phytase for improving the availability of phytate P in soybean meal when varying levels of P were fed. The semi-purified basal diet (.18% phytate P) contained soybean meal as the only protein source. Seven levels of phytase (0, 200, 400, 600, 800, 1,000, and 1,200 U/kg diet) were added to diets formulated to contain .20, .27, or .34% nonphytate P (nP; or .38, .45, and .52% total P, respectively). The desired levels of nP in the three basal P diets were achieved by adding varying amounts of defluorinated phosphate. A 2:1 Ca:total P ratio was maintained in all diets. Body weight gains and feed intake were improved (P < .001) by phytase at all nP levels, but the magnitude of response was greatest at low nP levels, resulting in an nP by phytase interaction (P < .01). Gain:feed was unaffected by phytase addition. A high mortality (35 to 45%) was observed for the .20 and .27% nP diets without added phytase, but this declined to normal levels with the addition of 200 to 400 U phytase/kg diet. Ash percentage of toes and tibia and shear force and stress of tibia increased with added phytase. These responses clearly show that the phytate-bound P in soybean meal was made more available to broilers by microbial phytase, and the total response was related to the phytase and nP/total P levels. Based on the high R2 values for the second order translog equations, BW gain, feed intake, and toe ash percentage were the most sensitive indicators to assess P availability, followed by tibia force and ash percentage. Derived nonlinear and linear equations for BW gain and toe ash percentage at the two lower nP levels were used to calculate P equivalency values of phytase for inorganic P. Using the average function of P released ( gamma ) by microbial phytase ( chi ) derived with nP levels of .20 and .27% for BW gain and toe ash percentage, gamma = 1.120 - 1.102e-.0027chi, 1 g of P could be released with 821 U of phytase. The amount of P released increased with increasing levels of phytase, but the amount of P released per 100 U of phytase decreased. Released P ranged from 31 to 58% of phytate P for 250 to 1,000 U of phytase/kg of diet.

6-Phytase↗

PubMed1995

Response of turkey poults to tiered levels of Natuphos phytase added to soybean meal-based semi-purified diets containing three levels of nonphytate phosphorus.

A 3-wk feeding trial using 920 day-old turkey poults was conducted to evaluate the addition of seven levels of phytase (Natuphos; 0, 200, 400, 600, 800, 1,000, and 1,200 U/kg of diet) to diets containing three levels of nonphytate P (nP) (.27, .36, and .45%). A positive control diet contained .60% nP. Semi-purified basal diets contained soybean meal as the only protein source. The increase in BW gain from added phytase was greatest for the lowest nP diet (nP by phytase interaction, P < .001). At .27% nP, gains improved (P < .001) to 800 U of phytase/kg of diet and then reached a plateau. At .36 and .45% nP, increases in gains were observed only for 200 U of phytase/kg of diet. The highest phytase addition to.36 and .45% nP diets produced gains equal to those of the positive control diet. Feed intake increases paralleled those of BW gains. Gain:feed was lowest for the .27% nP diets without phytase, but improved (P < .001) to 800 U of phytase/kg of diet and then reached a plateau. The high incidence of leg disorders and high mortality (40%) observed for the poults fed the .27% nP diet without added phytase declined with the addition of 200 to 400 U of phytase/kg of diet. Ash percentage of toes and tibias increased as the levels of nP (P < .001) and phytase (P < .01) increased; the magnitude of the response to phytase decreased as nP in the diet increased, resulting in an nP by phytase interaction (P < .001). Tibial shear force and stress responded in a similar manner to increasing levels of nP and added phytase. Results show that 652 U of microbial phytase is equivalent to 1 g of P from defluorinated phosphate in turkey starter diets using soybean meal as the only source of phytate P. The response per 100 U of phytase decreased as the total amount of phytase added was increased.

6-Phytase↗

PubMed1994

Nitric oxide controls feeding behavior in the chicken.

To investigate the effect of nitric oxide (NO) on food intake in the chicken, L-NG-nitro-arginine methyl ester HCl (L-NNA), an inhibitor of NO synthase, was applied. When i.p. administered, L-NNA significantly inhibited the food intake of broiler chickens in a dose response manner. Food ingestion was also depressed by the i.c.v. injection of L-NNA in a dose response fashion. The effect of L-NNA was attenuated by i.c.v. administration of L-arginine. These results suggest that central NO may control feeding behavior in the chicken.

Animals↗

PubMed1994

Peripheral regulation of food intake in poultry.

This review focuses on food intake regulation in avian species with the emphasis on sites of action outside of the central nervous system using data obtained mainly with studies involving poultry. Avian species do appear to regulate food intake, and there is good evidence that both the gastrointestinal tract and the liver are primary sites for regulation. Although young meat-type chickens may be eating near gut capacity, this does not appear to be the case in older birds. Furthermore, although the crop probably has a role in food intake control when meal feeding, its role during free access feeding is marginal. Food intake can be altered in chickens by infusion of glucose, lipids, epinephrine and possibly amino acids into the liver. The response to such infusions is altered by genotype and feeding state (fed or unfed). In addition, injection of peptides including cholecystokinin, bombesin, and gastrin outside the central nervous system decrease food intake. It is uncertain whether the anorexigenic effect of these peptides is a specific response, or if it is a general response caused by abdominal discomfort. Opioids appear to stimulate food intake with at least part of their effect being from outside of the central nervous system. Therefore, although the central nervous system is involved in food intake control in avian species, there are other sites involved. Furthermore, genetic selection for growth in meat-type chickens has altered the responsiveness of these control mechanisms suggesting that there is genetic variation for these physiological systems.

Amino Acids↗

PubMed1993

Food and water intake responses of the domestic fowl to norepinephrine infusion at circumscribed neural sites.

The effect on food and water intake of injection of norepinephrine into circumscribed brain sites of the domestic fowl was investigated. Injection of norepinephrine into sites throughout the preoptic area caused reliable increases in food intake. Food intake was also increased by injection of norepinephrine in the ventromedial nucleus, paraventricular nucleus, and medial septal sites. Food intake was decreased by injections near the lateral septal organ and the anterior portion of both the nucleus reticularis superior, pars dorsalis, and the tractus occipitomesencephalicus. Within the preoptic area, water intake was increased at basolateral sites but was inconsistently affected at more medial sites. No consistent trends were noted at sites examined outside the preoptic-hypothalamic area.

Animals↗

PubMed1993

Feeding behaviour in chickens given diets containing medium chain triglyceride.

1. The effect of dietary medium chain triglyceride (MCT) on short-term food intake was compared with the effect of long chain triglyceride (LCT) in chickens. Maize oil was used as the LCT while glyceryl tricaprylate (C 8) and glyceryl tricaprate (C 10) were used as MCT. Cumulative food intake was determined during the 6 h after the start of feeding. 2. Chicks were given diets containing 200 g C 8/kg diet, 200 g C 10/kg diet or 200 g LCT/kg diet in experiment 1. As early as 30 min after feeding, cumulative food intake in both MCT-supplemented diets decreased significantly compared with the diet containing LCT. 3. To determine if endogenous cholecystokinin (CCK) was responsible for the decrease in food intake caused by MCT, birds were injected with the CCK-A receptor antagonist devazepide (DVZ, 1 mg/kg BW) before diet presentation. DVZ had no effect on food intake with either LCT- or MCT-supplemented diets. 4. In experiment 3, chicks were given a choice between either diets containing LCT and C 8, LCT and C 10, or C 8 and C 10 to confirm whether or not the palatability of the diets was influenced by the dietary fat sources. There was no difference in food intake between C 8 and C 10-supplemented diets. However, chicks preferred the LCT-supplemented diet compared with either of the diets containing MCT.

Animal Feed↗

PubMed1993

Supplemental dietary L-tryptophan effects on growth, meat quality, and brain catecholamine and indoleamine concentrations in turkeys.

1. An experiment was conducted to investigate the effects of feeding supplemental tryptophan during the two weeks before market on growth, mortality during transportation, meal quality and brain neurotransmitter concentrations in male turkeys. 2. Brain serotonin, 5-hydroxyindoleacetic acid and norepinephrine concentrations were increased dose-dependently with 1.0, 2.0 and 3.0 g/kg supplemental dietary tryptophan. 3. Supplemental dietary tryptophan had no effect on body weight gain, food intake, food efficiency or mortality. 4. Carcase and individual thigh weights were significantly heavier in those birds fed 1.0 g/kg supplemental tryptophan.

Animal Feed↗

PubMed1993

Early feed restriction of broilers: effects on abdominal fat pad, liver, and gizzard weights, fat deposition, and carcass composition.

A total of five experiments were conducted to investigate the effects of early feed restriction on organ weights, fat deposition, and carcass composition in broilers. In Experiments 1 and 2, broiler chicks were reared in litter pens for 49 days, whereas Experiments 3, 4, and 5 were conducted in battery cages for 28 days. Feed restriction in all experiments was accomplished by providing male broiler chicks 40 kcal per bird per day for 7 (Experiments 1 and 2) or 6 (Experiments 3, 4, and 5) days, starting at 4 days of age. Feed restriction of broiler pullets in Experiment 1 was imposed from 4 to 9 days of age. Furthermore, the starter and grower diets in Experiment 2 contained either 1 or 4% added fat and the starter diets in Experiments 3, 4, and 5 contained either 21 or 26% protein. No significant differences were observed for abdominal fat pad and gizzard weights, liver and carcass fat, or carcass protein between early restricted birds and ad libitum controls at 49 days of age in Experiments 1 and 2. Furthermore, with the exception of Experiment 4, no differences in abdominal fat pad weights were observed among the different feeding regimens. Significant increases in abdominal fat pad weights, percentage liver, and percentage carcass fat were noted for females at 49 days of age when compared with male broilers. Carcass fat was significantly higher and carcass protein was significantly lower in broilers fed commercial versus reduced fat diets. Broilers fed a 21% protein diet had significantly heavier abdominal fat pad weights at 28 days of age than birds fed a 26% protein diet.

Adipose Tissue↗

PubMed1993

Characterization of lipogenic and lipolytic activity, muscle tissue composition, and DNA and RNA levels of broilers eating ad libitum or severely restricted at an early age.

Four experiments were conducted to characterize the rates of lipogenic and lipolytic activities and the composition and DNA and RNA concentrations in muscle tissue of broilers that were feed restricted at an early age. In all experiments, feed restriction (40 kcal/day per bird) was initiated at 4 days of age with ad libitum consumption of feed resuming at either 11 (Experiments 1 and 2) or 10 (Experiments 3 and 4) days of age. Female chicks in Experiment 1 were feed restricted at the same level from 4 to 9 days of age. Birds consuming feed ad libitum served as controls in all experiments. Broilers restricted for 7 days had significantly lower plasma very low density plus low density lipoproteins (VLDL+LDL) than the ad libitum birds at 49 days of age in Experiments 1 and 2. However, the reverse was observed at 28 days of age, as plasma triglycerides and lipoproteins and lipogenesis were greater in restricted chicks when compared with controls. No significant differences were observed in plasma triglycerides at 49 days of age or lipolysis, DNA and RNA concentrations, muscle protein, and muscle fat at 28 days of age between restricted and ad libitum broilers. Results from these studies indicate that early feed restriction may have induced a metabolic shift in restricted broilers that increased lipogenesis at 28 days of age, followed by a partitioning of excess nutrients to support anabolic activity at market age.

Adipose Tissue↗

PubMed1992

The effect of triacylglycerol chain length on food intake in domestic fowl.

Triacylglycerols of varying chain lengths were tested for their effects on food intake in fasted Single-Comb White Leghorn cockerels 9-12 weeks of age. Tributyrin, tricaprylin, triolein, or saline were intubated intragastrically or infused intrahepatically. All triacylglycerol administrations were in 10 ml volumes with 10 kcal being infused intrahepatically and 10 or 20 kcal being infused intragastrically. When administered intragastrically, the short-chained triacylglycerol tributyrin decreased food intake at most times tested; the medium chain-length tricaprylin and the long chain-length triolein affected food intake sporadically. When infused into the liver, tributyrin and tricaprylin decreased food intake at most times tested, whereas triolein decreased food intake at 60 and 180 minutes only. Satiating effectiveness was related to triacylglycerol chain length when intubated, which may reflect rate of absorption from the gut; however, hepatic satiety receptors were also differentially sensitive to triacylglycerol chain length indicating that more than rate of assimilation from the gut must be considered.

Animals↗

PubMed1992

The effect of light source and intensity on turkey egg production.

The effect of light source and intensity on egg production, fertility, hatchability, egg weight, and shell quality in turkey hens was investigated. Turkey hens were exposed to either incandescent, high-pressure sodium vapor (HPSV), or daylight fluorescent (FL) lights at an intensity of 21.6 1x during the growth phase (after 8 wk). During the breeder phase, hens were assigned to the same light sources at light intensities of either 53.8 or 166.4 1x in a 3 x 3 x 2 factorial arrangement of treatments. Light source during the growth phase had no significant effect on subsequent egg production, egg weight, fertility, or hatchability. Egg production, shell quality, fertility, and hatchability were also unaffected by light source or intensity during the breeder phase. Egg weight was significantly increased in hens exposed to HPSV compared with incandescent lights during the breeder phase. The HPSV and FL lights can be used effectively for turkey breeder hens both during the prebreeder and breeder periods. Furthermore, light intensities of 53.8 and 166.4 1x appear to be equally effective in stimulating production.

Animal Husbandry↗

PubMed1992

Effect of early feed restriction on growth, feed conversion, and mortality in broiler chickens.

Two floor pen and two battery experiments were conducted to determine the effects of early feed restriction on the performance of commercial broilers. Feed restriction was induced in all experiments by providing chicks with 40 kcal of ME per bird per day, commencing at 4 days of age. Male chicks were feed-restricted for 7 (Experiments 1 and 2) or 6 days (Experiments 3 and 4), whereas broiler females were restricted for 5 days (Experiment 1). Ad libitum feeding was resumed after the restriction periods, and continued through the conclusion of the experiments at 49 (Experiments 1 and 2) or 28 (Experiments 3 and 4) days of age. Broilers provided ad libitum access to feed for the entire experimental period served as the controls in each study. Broilers subjected to an early feed restriction had significantly (p less than or equal to .05) lower mean body weights than controls for all ages measured in the four experiments. However, feed conversion ratios for restricted broilers were significantly lower at 28 (Experiments 1 through 4) and 49 (Experiments 1 and 2) days of age than for birds consuming feed ad libitum. Through regression analyses, it was estimated that male broilers in Experiments 1 and 2 would require approximately 2 additional days to obtain body weights similar to those observed in control broilers and would still maintain a lower feed conversion ratio at this older age. In Experiments 1 and 2, weekly body weight gains for restricted broilers were significantly lower than for controls from 0 through 28 days of age. However, restricted broilers (7 days) in Experiment 2 had significantly higher rates of gain from 29 to 49 days of age than unrestricted controls. Total pen body weights for restricted and ad libitum groups were similar at 49 days of age in Experiments 1 and 2, which reflected the significant difference in mortality observed between the two groups.

Age Factors↗

PubMed1992

Effects of light sources and the presence or absence of males on reproduction of female breeder turkeys.

The effects of sodium vapor (SV), daylight fluorescent (DF), and incandescent (IN) light sources and the influence of the presence or absence of males on reproduction of female turkeys were evaluated. Hens under SV and DF lights consistently laid more eggs than those under IN lights. There were no significant differences in hen-day egg production among hens in the physical presence of males and hens allowed visual and vocal contact with males. However, hen-day egg production was significantly lower for females in pens in which males were absent. Fertility, hatchability, days to first egg, egg weight, and egg specific gravity were unaffected by light source treatments or by the presence or absence of males in pens of females.

Analysis of Variance↗

PubMed1991

Induction of food intake by a GABAergic mechanism in the turkey.

The effect of GABAergic influences on food and water intake in Large White turkeys was investigated. In Experiment 1, food and water intake were monitored in hens injected intracerebroventricularly (ICV) with varying doses of muscimol, a GABA agonist. In Experiment 2, hens were pretreated with ICV injections of picrotoxin, a GABA antagonist, prior to the injection of muscimol. In Experiment 3, the effect of ICV injections of muscimol on water intake was determined in hens not allowed access to food. The ICV injection of muscimol caused a dose-dependent increase in food intake with 75 nmole being the most efficacious dose. Water intake was stimulated following the injection of muscimol when food and water were available ad lib. However, water intake was not affected by the ICV injection of muscimol if food was not simultaneously available, indicating that the increased water intake was a result of increased food intake. The effect of muscimol on food intake was significantly attenuated by pretreatment with picrotoxin. It appears, therefore, that GABA acts within the brain of the turkey to increase food, but not water, intake.

Animals↗

PubMed1991

Protein and energy self-selection of turkey hens. Serum prolactin and luteinizing hormone concentrations.

1. The incidence of broodiness was four times as high among turkey hens fed a complete control diet than among hens allowed to self-select their diet from two different feed sources, one being relatively high in protein and the other relatively high in energy (i.e. split-diet). 2. Among non-broody birds, hens fed the split-diet had a significantly lower serum prolactin concentration in the third month of production as compared to control hens. 3. Hens in their second season of egg production had significantly lower serum luteinizing hormone concentrations during the latter stages of egg production than did first season hens.

Animals↗

PubMed1991

Self-selection of dietary protein and energy by turkey breeder hens.

1. An experiment was conducted to determine the effects of self-selection of dietary protein and energy by turkey hens on reproductive performance in a warm environment. 2. Dietary self-selection had no significant effect on egg production, egg weight, or body weight of turkey hens. 3. Fertility and hatchability of eggs produced by self-selecting hens were significantly reduced compared to eggs from control hens fed on a complete diet. 4. Protein intake was significantly reduced among self-selecting hens when compared to control hens fed on a complete diet (P less than or equal to 0.001). 5. Food and energy intake decreased as the ambient temperature increased. Nevertheless, protein intake of self-selecting hens increased over the course of egg production despite decreasing food intake. Therefore, self-selecting hens preferred a diet with a greater protein content (g protein/kg diet) in the last 10 weeks of egg production than during the first 10 weeks of egg production.

Animal Feed↗

PubMed1991

Effect of coccidiosis on plasma epinephrine and norepinephrine levels in turkey poults.

Plasma epinephrine, norepinephrine, and glucose levels were measured in 3- to 4-wk-old turkey poults that had been infected with the coccidium Eimeria adenoeides. When measured at 6 days postinoculation, the acute stage of the infection, the epinephrine and norepinephrine levels of the infected poults showed a dose-dependent increase over levels in controls, with poults that were most heavily infected having the highest levels. The catecholamines appeared to show a classic stress-elicited response: this response increases with time to high levels during the acute stage of the infection, and then returns to levels approximately the same as those of the controls as the poults recover from the infection. Anorexia, or feed restriction, appeared to be primarily responsible for the increase in norepinephrine. However, epinephrine levels in the infected poults were significantly higher than in their pair-fed, uninfected counterparts, indicating that factors other than reduced feed consumption contributed to the increase. The data indicate that plasma catecholamines are increased during coccidial infection. As pressor compounds, they may contribute to the previously observed changes in blood pressure and heart function in infected poults.

Animals↗

PubMed1990

Neonatally-induced thermotolerance: physiological responses.

1. Broiler cockerels exposed to neonatal heat (35-37.8 degrees C for 24 hr) at 5 days of age experienced significantly lower mortality upon exposure to elevated temperatures (35-37.8 degrees C) at 43 days of age than did cockerels not given neonatal heat exposure. 2. No differences were found between neonatally stressed and neonatal control groups in water consumption, core and surface temperature, plasma T3 and T4, protein or glucose concentration when exposed to juvenile heat stress. 3. Heterophil to lymphocyte ratios were significantly lower in the neonatally stressed than in the neonatal control group when exposed to heat at 44 days of age. 4. The results indicate that lower mortality during periods of high environmental temperature in the neonatally stressed chicks may involve homeostatic mechanisms different from those utilized during acclimation to high environmental temperature.

Adaptation, Physiological↗