Biomedical subjects

J D May

Publications and source records attributed to J D May.

At least 37 records · Page 2Linked to original sources

PubMed1990

The effect of light and environmental temperature on broiler digestive tract contents after feed withdrawal.

Contamination from the digestive tract is a persistent problem in broiler processing. Two experiments were conducted to determine the effects of lighting and environmental temperature on quantity of crop, gizzard, and small intestine contents during feed withdrawal. Broilers were on litter with a feeding regimen of 1.5 h on feed and 4.5 h off feed for 1 or 2 days. The withdrawal period began at the end of a 1.5-h feeding period. In the first experiment, broilers were cooped or left on the floor with and without lights. Crop contents of lighted broilers at 21 C were reduced 2 h after feed withdrawal for broilers on litter and in coops. In another experiment, broilers on litter were maintained at 18 and 27 C in light or in darkness. Lighting reduced crop contents 4 h after feed withdrawal but increased the contents of the small intestine 2 h after feed withdrawal at both temperatures. These results indicate that crop clearance is improved by lighting both before and after cooping.

Animals↗

PubMed1989

Digestive tract clearance of broilers cooped or deprived of water.

Feed is withdrawn from broilers to facilitate digestive tract clearance before processing. This research examined the effects of cooping and water deprivation on contents of the digestive tract during feed withdrawal in two experiments. Broilers were reared to 48 days of age on litter in a windowless house. Corn-soybean meal diets and water were provided ad libitum. In the first experiment, broilers were continuously fed before feed withdrawal. In the second experiment, broilers were placed on a meal-feeding regimen of 1.5 h on feed and 4.5 h off feed for 42 h prior to feed withdrawal. Withdrawal began at the end of a 1.5-h feeding period. At the time of feed withdrawal, broilers were cooped, left on litter without water, or left on litter with water available. At 2, 4, 6, and 8 h after withdrawal, ten broilers from each treatment were killed and the crop, proventriculus plus gizzard, and small intestine were removed. The weight of the contents of each segment was determined. Water deprivation did not change the weight of contents in any segment. Cooped broilers retained digesta in the crop and proventriculus plus gizzard for a longer time than broilers on litter. The combination of meal feeding and cooping soon after feed withdrawal greatly increased the quantity of digesta in the crop 8 h after feed withdrawal. Cooping should be delayed until the crop is empty. Meal feeding increases the time required to accomplish this.

Animals↗

PubMed1988

Effect of environmental temperature and feeding regimen on quantity of digestive tract contents of broilers.

Carcass contamination from contents of the digestive tract during processing is a recurring problem for the broiler industry. Environment and feeding regimen are often implicated as causative factors. The effects of environmental temperature and meal feeding on passage of feed through the digestive tract of broilers were examined. Broilers were reared in environmental chambers in five experiments. In the first experiment, environmental temperatures were constant temperatures of 16 and 27 C and cycles of 16-24-16 and 24-35-24 C and rate of passage of feed through the digestive tract (ROP) was determined with ferric oxide. Temperature did not consistently affect ROP. In the other four experiments, various environmental temperatures were investigated and broilers were fed continuously or for 12 or 16 h/day. Contents of the crop, proventriculus plus gizzard, and small intestine were weighed 2, 4, 6, and 8 h after feeding withdrawal. Environmental temperature did not directly affect the movement of digesta but the feeding regimen affected the quantity of digesta in some segments of the tract. Environmental temperature may have indirectly affected the quantity of feed in the crop by affecting the quantity of feed consumed. Limiting the feeding period resulted in retention of digesta in the crop of some broilers for an extended period. This increased the variability in quantity of crop contents. A feeding regimen X temperature interaction resulted in increased small intestine weight for meal-fed broilers at 16 C.

Animals↗

PubMed1988

Weight gain of summer-reared egg-type pullets fed pellets versus mash.

In an attempt to increase weight gain of egg-type pullets reared under high summer temperatures, pullets were fed feed in either pellet or mash form. Under high temperature rearing conditions, pelleting the diet did not significantly increase 12 to 20-wk body weight gain when compared to effects of the diet fed in mash form. Under a moderate temperature regimen (21 C), pelleting the diet did significantly increase 12 to 20-wk body weight gain in contrast to the effects of the diet fed in mash form.

Animal Feed↗

PubMed1987

Body temperature of acclimated broilers during exposure to high temperature.

Short-term acclimation to high temperatures increased resistance of broilers to heat exposure. Two trials were conducted to determined the effect of acclimation on body temperature (Tb) during heat exposure. Broilers, 46-days old, were maintained at control or acclimating temperatures for 4 days. The control temperature was a constant 21 C with a 10 C dewpoint, and the acclimating temperature was a diurnal cycle of 24-35-24 C with a constant 21 C dewpoint. During the 4th day, broilers of both groups were exposed to temperatures of 41 C and 23 C dewpoint for 210 min. Body temperature was determined at the beginning of the heat exposure and at 30-min intervals until the end of the exposure. The Tb of both groups increased throughout heat exposure, but acclimated broilers had significantly lower Tb than control broilers from 90 through 210 min. Acclimated broilers had significantly lower heat stress mortality. The data show that acclimated broiler's Tb rises upon exposure to heat but that acclimation gives the capacity to stabilize Tb above normal Tb. The data also suggest Tb is preferable to mortality as a measure of acclimation in broilers.

Acclimatization↗

PubMed1986

Relationship of photoperiod and feed intake to thyroid hormone concentration.

Broilers, obtained from a commercial hatchery, were reared in two environmental chambers with controlled temperature, humidity, and lighting in three trials. Lighting was continuous for 0 to 7 days and 12L:12D thereafter. Temperatures, initially 32.2 C in Trials 1 and 3 and 29.4 in Trial 2, were gradually lowered during rearing. At the end of the trials, temperatures were 21.1, 10.0, and 23.9 C in Trials 1, 2, and 3, respectively. Feed and water were provided ad libitum until 21 days in Trials 1 and 3 and 28 days in Trial 2. During the subsequent 14 days in each trial, feed was provided 12 hr/day with one chamber receiving feed during photophase (LF) and the other receiving feed during scotophase (DF). Plasma samples for 3,5,3'-triiodothyronine (T3) and thyroxine (T4) assay were obtained at 3-hr intervals throughout a 24-hr period at the end of the 14-day treatment period. During the 14-day treatment period, the weight gain of the DF broilers averaged 90% of the LF broilers for the three trials. This demonstrates broilers adapted very well to feeding during scotophase. The T4/T3 ratio increased during fasting and decreased when feed was available, but photoperiod had no discernible effect. The change in T4/T3 ratio over 24 hr was greater at high than at low environmental temperatures.

Animals↗

PubMed1986

Effect of acclimation and heat stress on thyroid hormone concentration.

In three trials, broilers were exposed to either moderate-constant or high-cyclic temperatures for 3 days. Broilers in both treatments were exposed to 41 C and high humidity over a 4- to 6-hr period on the 4th day. Blood samples, collected before and at the end of the heat exposure, were assayed for thyroid hormones. Neither acclimation nor severe heat exposure consistently affected triiodothyronine (T3) or thyroxine (T4) concentration. It appears the mechanism of short-term acclimation involves endocrine or physiological responses other than changes in circulating thyroid hormone concentrations.

Acclimatization↗

PubMed1985

Swab absorbability--effect on Mycoplasma gallisepticum isolation.

A single strain of commercial Leghorn vaccinated with F strain Mycoplasma gallisepticum (MG) was used in two trials to determine the effect of swab absorbability on MG isolation. For each of the two trials, 34 birds from each of five 10,000 bird houses were randomly selected and swabbed from the choanal cleft region; 17 birds from each house were swabbed with ethylene-oxide sterilized, 2.4-mm diameter calcium alginate-tipped swabs, while the remaining 17 birds were swabbed with similarly sized and sterilized rayon-tipped swabs. Results of this study indicate swab absorbability does not affect the recovery and subsequent isolation of MG from commercial layers.

Absorption↗

PubMed1984

Thyroidal influence on body growth.

This review of thyroid influence on body growth in poultry is organized around the following parameters of growth: increase in body weight and skeletal size, muscle growth, and growth of cartilage and bone. The greatest effect of goitrogens on growth of embryos occurs during late embryogenesis at a time when normal thyroid hormone levels are increasing. Posthatching growth is reduced in severely hypothyroid animals, and body weight gain is affected more than bone growth. Thyroid hormone replacement restores body growth of thyroidectomized chickens, but supplemental hormone in normal animals has no beneficial effect on growth. Excessive T3 (fed at 1 ppm) is detrimental to growth and feed efficiency. No clear correlation between thyroid hormone concentration and growth rate of normal chickens has been identified. Growth depression in sex-linked dwarf birds is at least partially reversed by supplemental T3. Muscle growth is reduced in goitrogen-treated chickens and the growth reduction is reversed by supplemental thyroxine. Total DNA accumulation is reduced in hypothyroid chickens, but muscle mass relative to DNA content is normal following long-term treatment; this suggests some regulation of muscle mass relative to DNA content. T3 increases the number of muscle fiber nuclei in hypothyroid chickens and the uptake of 3H-thymidine into nuclei within the basal lamina. T3 directly stimulates growth and maturation of embryonic chick cartilage and enhances the in vitro action of somatomedins on cartilage growth. There is little information concerning the role of the thyroid in posthatching cartilage and bone growth in poultry.

Animals↗

PubMed1984

The individual and combined effects of aflatoxin and ochratoxin A on various processing parameters of broiler chickens.

Male broilers (Hubbard X Hubbard) were placed at hatching into a completely randomized 2 X 2 X 2 factorial experimental design with the treatments consisting of 0 and 2.5 micrograms aflatoxin/g of feed (ppm) and 0 and 2.0 ppm ochratoxin A. In Trial 1, there were four replicate pens of 10 broilers per replicate at each treatment level. At 3 weeks of age two replicate pens were randomly selected and placed on control feed (0 to 3 weeks), the remaining two replicate pens were maintained on treatment (full-term). In Trial 2, there were three replicates of 38 broilers per replicate at each treatment level. At 3 weeks of age 13 broilers from each replicate pen were randomly selected and placed in separate housing and fed control diets (0 to 3 weeks). The remaining 25 broilers were kept on mycytoxin treatments until the conclusion of this trial (full-term). Data collected in these trials indicate that body weights of broilers were significantly (P less than .05) decreased by aflatoxin, ochratoxin A, and the combination treatments of the full term feeding regimen. Broilers partially recovered body weight in the 0 to 3-week feeding regimen; however, recovery was less rapid during ochratoxicosis compared to aflatoxicosis. Body weights of broilers in the combination treatment remained significantly (P less than .05) depressed throughout the trials. As body weight decreased, parts weights decreased accordingly. Carcass yield was significantly (P less than .05) decreased by all treatments, primarily by a decrease in breast yield.(ABSTRACT TRUNCATED AT 250 WORDS)

Aflatoxins↗

PubMed1983

Thyroid activity of selected, nonselected, and dwarf broiler lines.

Growth rates and serum thyroid hormone concentrations were compared in two trials. In Trial 1 Athens-Canadian (AC) randombred chickens (nonselected) were compared with commercial broiler line chickens (selected). Trial 2 involved the same nonselected and selected lines and a sex-linked dwarf line developed from the same background as the AC population. Selected line birds were heavier than nonselected line birds and nonselected line birds were heavier than dwarf line birds from 1 through 8 weeks of age. Overall, the selected line had lower 3,5,3'-triiodothyronine (T3) concentrations than the nonselected line. No significant differences in thyroxine (T4) concentrations were observed between selected and nonselected lines. The dwarf line had lower T3 and higher T4 concentrations than the other lines. The data suggest a lower rate of T4 deiodination in the dwarf line.

Animals↗

PubMed1983

Individual and combined effects of aflatoxin and ochratoxin A on bruising in broiler chickens.

A 2 x 2 factorial design with treatments of 0 and 2.5 microgram/g aflatoxin and 0 and 2.0 microgram/g ochratoxin A was used to evaluate the individual and combined effects of these mycotoxins on bruising and blood thigh syndrome in broiler chickens. Trial 1 consisted of four replicate pens of 10 broilers per replicate, which were maintained on these dietary treatments from 0 to 3 weeks of age. At 3 weeks of age two replicate pens per treatment were randomly selected and placed on toxin-free feed with two replicate pens remaining on toxin feed until they were 6 weeks of age when the trial was concluded. In Trial 2 three replicate pens of 38 broilers per treatment were maintained on toxin feed from 0 to 3 weeks of age. At 3 weeks of age 13 broilers per replicate were placed on toxin-free feed with 25 broilers per replicate remaining on toxin until they reached 7 weeks of age when Trial 2 was concluded. These data indicate that a synergistic toxicity exists between aflatoxin and ochratoxin A to significantly (P less than .05) decrease body weight. Body weights of broilers on aflatoxin or ochratoxin A diets for only 3 weeks partially recovered by 6 or 7 weeks of age; however, the body weights of broilers on the interaction treatments for only 3 weeks remained significantly (P less than .05) depressed at 6 and 7 weeks of age.(ABSTRACT TRUNCATED AT 250 WORDS)

Aflatoxins↗

PubMed1983

Effects of low level chronic aflatoxicosis in broiler chickens.

A completely random design consisting of three replicates of 25 broiler chickens (Hubbard x Hubbard) at each of four treatments was used to evaluate the effects of low level, chronic aflatoxicosis on performance and various processing parameters. The treatments in Trial 1 were control, .075, .225, and .675 and in Trial 2 control, .3, .9, and 2.7 micrograms/g toxin in feed (ppm). The chickens were maintained on these treatments from day-old to 7 weeks of age with feed and water available ad libitum. All aflatoxin dose levels in Trial 1 significantly (P less than .05) decreased live, dressed, and chilled eviscerated weight, whereas only 2.7 ppm significantly (P less than .05) decreased live and dressed weight in Trial 2, with chilled eviscerated weight being significantly (P less than .05) decreased at .3 and 2.7 ppm in Trial 2. Parts weights and dimension measurements reflected the aflatoxin-induced decrease in dressed weight. Breast yield (%) was significantly (P less than .05) decreased by aflatoxin while back, wing, drum, and thigh yields were significantly increased by aflatoxin. No effect of aflatoxin was seen on the incidence of crooked keel, feather follicle infection, breast blisters, or conformation. A hypocarotenoidemia and hepatic hyperlipemia were clearly a result of chronic aflatoxicosis in these broiler chickens. These data demonstrate that the toxicity of aflatoxin is dependent on the environment in which broiler chickens are exposed.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1983

Evaluation of immunity of young broiler chickens during simultaneous aflatoxicosis and ochratoxicosis.

A 2 X 2 factorial experimental design consisting of the treatments 0 and 2.5 micrograms/g aflatoxin and 0 and 2.0 micrograms/g ochratoxin A with 12 replicates of 10 birds per treatment level was used to evaluate the effects of these mycotoxins on various aspects of immunity. Male chicks (Hubbard X Hubbard) were maintained on these treatments from one day of age to 3 weeks of age at which time six replicate pens per treatment were sacrificed and various parameters measured. The additional six replicate pens per treatment were maintained on toxin feed beyond 3 weeks of age, and at 4 weeks of age, three replicate pens were immunized with sheep red blood cells (SRBC) and Brucella abortus. Antibody titers were measured up to 10 days postimmunization. Aflatoxin and ochratoxin A, individually, significantly (P less than .05) decreased body weight, and a synergistic toxicity was evident by a significant (P less than .05) decrease in body weight. Antibody titers and phagocytic activity of heterophils were not significantly (P less than .05) altered by any treatments. The relative weight of the bursa of Fabricius and the number of follicles for a given area of the folds of the bursa of Fabricius were significantly (P less than .05) decreased only by the interaction treatment. Complement activity was significantly (P less than .05) decreased by aflatoxin and the combination of aflatoxin and ochratoxin A and depressed, although not significantly (P less than .05), by ochratoxin A.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1982

The effect of floor type on the development of breast blisters and feather follicle infections in broilers.

The effect of floor types on the incidence of feather follicle infection and breast blisters in caged broilers was investigated in two trials. Broilers were reared on corn-soybean meal diets with warm-room brooding. Floor types included litter (control), wire, wire covered with various types of plastic mats, and wire woven with surgical tubing. In trial 1, the effect of a coccidiostat (Monensin, 120 mg/kg of feed) was investigated for broilers not on litter, and in trial 2, the effect of supplemental zinc was investigated. Broilers were processed in the laboratory processing plant when they were 51 (trial 1) and 53 days old (trial 2). Carcasses were evaluated for the occurrence of fleshing downgrades, crooked keels, feather follicle infection, and breast blisters. Incidence of feather follicle infection was low for broilers on litter or wire floor and high for broiler reared on plastic mats. Breast blisters incidence was low for broilers on litter and plastic mats and was high for broilers on the wire floor. Overall carcass quality for litter (control) was superior to any of the cage treatments. Neither the coccidiostat nor supplemental zinc affected the incidence of breast blisters or feather follicle infection.

Animals↗

PubMed1982

Effect of dietary thyroid hormone on survival time during heat stress.

Broilers were fed corn-soybean meal diets supplemented with either 3, 5, 3'-triiodothyronine (T3) or thyroxine (T4) for various time periods ranging from 8 to 26 days. Survival times during heat stress were determined for females and males fed the control, T3, and T4 diets. Serum hormone concentration for serums collected prior to heat stress was determined by radioimmunoassay. The combined results of both trials show significantly shortened survival times for T3 and T4 and that T3 had a much greater effect than T4. Male broilers had shorter survival times than females and there was no interaction of hormone and sex. Serum T3 and T4 concentrations were greater in serum T4 concentration, but dietary T4 had no effect on serum T3 concentration.

Administration, Oral↗

PubMed1981

Relationship of pen height to bone strength of broilers.

Broilers reared in cages have a high incidence of wing breakage during processing. Three trials were conducted to determine the effects of cage dimensions and floor types on bone breaking strength and wing breakage during processing. Broilers were fed commercial-type diets and processed through the pickers at a commercial processing plant or a research facility. Broken bones were detected by palpation, and humeri and tibia were removed. Breaking strength was determined for the humeri and tibia with a testing instrument. Incidence of breast blisters, crooked keels, follicle infection, fleshing downgrades, and slabsidedness were determined in one trial. Cage height was the major factor affecting wing breakage and humerus strength. Incidence of wing breakage for broilers on wire floors with cages .64 m high was not significantly different from that of control broilers reared on litter with ceiling 2.54 m high. Humerus breaking strength was significantly reduced in two of three trials by the .64-m-high ceiling. Cage rearing increased the incidence of crooked keels and feather follicle infections.

Animals↗

PubMed1980

Effect of dietary thyroid hormone on growth and feed efficiency of broilers.

Broiler chickens were fed corn-soybean meal diets supplemented with either 3,5,3'-triiodothyronine (T3) or thyroxine (T4) in five trials. Body weight gain and feed efficiency are reported for four trials. Chickens fed T3 at 1.00 ppm had poorer weight gain and feed efficiency than controls, but T4 at that same dosage did not adversely affect performance. Serum T3, T4, and 3,3',5'-triiodothyronine (rT3) were assayed by radioimmunoassay. T3 or T4 at 1.00 ppm in the diet resulted in respective serum T3 and T4 concentrations approximately three times the control concentration. Dietary T4 at 10 ppm resulted in increased rT3 values after 1, 2, 5, and 6 days of T4 feeding but increased T3 values at 1 day only. T4 was apparently deiodinated to rT3 and toxic concentrations of T3 were not observed during T4 feeding. The data indicate that chickens respond differently to T3 than to T4.

Animal Feed↗