Biomedical subjects

J D May

Publications and source records attributed to J D May.

At least 19 recordsLinked to original sources

PubMed1997

Supplemental thyroid hormones and molting in turkey breeder hens.

The objective of the current study was to determine whether thyroid physiology may affect molting time in turkeys. Two trials using approximately 144 hens were conducted to elucidate thyroidal factors that limit the molting process. Thyroid hormones or a thyroid blocker (thiouracil) were given to the hens during a molt by supplementing the diet with thyroxine (T4), triiodothyronine (T3), or thiouracil. Supplementing with T4 reduced the number of days to return to egg production, whereas supplementing with thiouracil or T3 prolonged days to first egg. The observations support previous suggestions of separate functions for T3 and T4 during molting. As had been observed many times previously, the feeding of thiouracil delayed the molt but did not completely stop the molting process. The hens fed thiouracil returned to 50% egg production nearly 10 d after the control group, whereas T3 prolonged the return to 50% egg production nearly 1 wk later. The data indicate the endogenous low levels of T4, but not T3 in modern strains of turkeys may contribute to a relatively longer molting period of turkey breeder hens induced to molt out of season.

Analysis of Variance↗

PubMed1997

Water consumption by broilers in high cyclic temperatures: bell versus nipple waterers.

Broilers were maintained on litter in environmental chambers to study water consumption from bell and nipple waterers. The chambers were set at high cyclic temperatures of either 24-35-24 C or 24-32-24 C daily cycles in three trials. Water consumption was recorded by computer each 30 min and calculated as a percentage of body weight. Daily water consumption from nipples was always less than from bell waterers. Water consumption by quarter-day revealed that consumption from nipples was often similar to that from bell waterers during the lowest temperatures but was less during the periods of highest temperatures. Further study revealed that water consumption from nipple waterers was related to the height of the nipples such that consumption was greater for lower nipples. The results suggest that panting broilers have difficulty drinking from high nipple waterers.

Analysis of Variance↗

PubMed1996

The effects of nonautoclaved and autoclaved water-soluble wheat extracts on the growth of Clostridium perfringens.

Clostridium perfringens is the causative agent of necrotic enteritis, a commonly diagnosed disease in chickens that is also observed in turkeys and geese. Two trials were conducted to determine the in vitro effect of filter-sterilized, water-soluble wheat extracts on the growth of C. perfringens. The extracts were either nonautoclaved or autoclaved at 121 C for 40 min and were used to reconstitute thioglycolate broth media. Results of this study suggest that growth of C. perfringens is suppressed in vitro by inclusion of either extract. Glycosyl composition analysis revealed no significant differences in arabinose, xylose, or mannose content between the nonautoclaved and autoclaved extracts. Galactose, glucose, and total glycosyl content were significantly higher in the nonautoclaved extract.

Animals↗

PubMed1995

Ability of broilers to resist heat following neonatal exposure to high environmental temperature.

Two trials were conducted to determine whether heat exposure of neonatal broilers had any effect on their growout performance or on their mortality during heat exposure later in life. Broiler chicks, 5 or 6 d old, were exposed to 36.1 C for 24 h in environmental chambers. At 47 d in Trial 1 and at 42 d in Trial 2, the broilers were exposed to 37.8 C for 6.5 h in Trial 1 and 8 h in Trial 2. Early heat exposure did not influence resistance to later heat exposure as measured by mortality. Also, early heat exposure did not affect body weight gain, feed efficiency, or growout mortality.

Adaptation, Physiological↗

PubMed1994

Acute heat acclimation and kidney function in broilers.

Broilers previously exposed to high environmental temperatures (heat-acclimated) are more resistant to heat stress and consume more water during heat stress than nonacclimated controls. Two experiments were conducted to determine whether heat-acclimated broilers conserve body water by reducing urine and solute (Na) excretion. In the first experiment, renal function studies were conducted at an ambient temperature (Ta) of approximately 21 C using anesthetized 7-wk-old male broilers. Control birds reared at a constant Ta of 24 C (Group N: noncycled Ta) were compared with birds that had been heat-acclimated by exposure for 3 to 6 d to a daily sinusoidal cycle of 24 to 35 to 24 C (Group C: cycled Ta). In the second experiment, renal function studies were conducted on anesthetized 5-wk-old control and heat-acclimated male broilers while they were exposed to a Ta of 21 C (Ambient Ta: Groups NA, CA), or to a Ta of 32 C (High Ta: Groups NH, CH). When high intravenous infusion rates (.37 mL/kg body mass per min) were used to simulate the volume expansion caused by thermogenic polydipsia, urine flow rates were significantly lower in Groups C and CA than in Groups N and NA, osmolal clearances were lower in Groups CA and CH than in Groups NA and NH, and all heat-acclimated groups in both experiments (Groups C, CA, CH) had significantly lower glomerular filtration rates (GFR), filtered loads of Na, and tubular Na reabsorption rates than the respective control groups (Groups N, NA, NH). These changes in kidney function potentially would minimize urinary fluid and solute loss when heat-acclimated broilers consume large quantities of water to support evaporative cooling. Reductions in GFR, filtered loads of Na, and tubular Na reabsorption rates also may help heat-acclimated broilers reduce the metabolic heat load associated with active (energy requiring) recovery of solute (Na) from the glomerular ultrafiltrate.

Acclimatization↗

PubMed1994

Effects of light and temperature on anticipatory feeding by broilers.

The objective of this research was to determine the effects of daily cycles of light intensity and temperature on anticipatory feeding by broilers. Broilers were maintained on litter in environmental chambers with feed provided for 12 h/d. Feed consumption was recorded by computer every 30 min and summarized for 2- and 24-h periods. In Trial 1, lighting was at 16 lx for 12 h and at 94 lx for 12 h each day. Feed was provided either during the 16- or 94-lx period. Broilers consumed more feed at the onset of feeding and at the end of the feeding period than at other times in both treatments. In Trials 2 and 3, the chamber temperature was cycled such that a 12-h feeding period was provided at either 32 or 16 C. Broilers consumed more feed at the onset of feeding than at other times but did not increase consumption at the end of the feeding period. The results indicate anticipatory feeding is enabled by cyclic lighting intensity but not by cyclic temperature. In Trial 4, the light intensity and temperature were cyclic. Feed was provided during high light intensity and at maximum temperatures. Feed consumption increased when temperature was declining, indicating broilers responded to the reduced temperature. The results show that a period of darkness is not required for anticipatory feeding and that environmental temperatures and lighting typical of curtain-sided broiler houses alter feed consumption patterns.

Animals↗

PubMed1993

Body and muscle growth of domestic turkeys (Meleagris gallopavo) and expression of myosin heavy chain isoforms in breast muscle.

Growth characteristics of breast (pectoralis) muscle of male Large White hybrid turkeys were described using the von Bertalanffy model and Huxley's allometric growth analysis, and the cellular maturation process of breast muscle was studied by examining the relationship between the timing of appearance of myosin heavy chain isoforms and circulating levels of thyroid hormones. The inflection points at which the maximum growth rate occurred were estimated to be 112 days for the body weight and 159 days for the breast-muscle weight. The allometric growth coefficient for pectoralis muscle, relative to the whole-body growth, was 1.23 and significantly greater than those of the gastrocnemius, sartorius, latissimus dorsi and extensor digiti muscles during the first 12 weeks posthatch. Myosin was prepared from pectoralis muscle of turkeys at ages ranging from 15 days of incubation (embryos) to 308 days (adult), and embryonic, neonatal and adult isoforms of myosin heavy chain were detected by monoclonal antibodies in the enzyme-linked immunosorbent assay. In turkey embryos, the embryonic myosin heavy chain isoform appeared by 22 days of incubation. The transition from embryonic isoform expression to neonatal isoform expression was noted shortly after hatch, and the transition from neonatal to adult was initiated at 7 days posthatch and was nearly completed by 28 days posthatch. The circulating thyroxine concentration rose and fell markedly around the time of hatch and fluctuated within the range of 11 to 19 ng/ml. The triiodothyronine concentration fluctuated within the range of 5 to 7 ng/ml after hatch and started to fall at 14 days posthatch to reach the adult level of 3 to 5 ng/ml.

Animals↗

PubMed1992

Feed and water consumption patterns of broilers at high environmental temperatures.

Broilers were reared on litter to determine the effect of cyclic environmental temperatures on feed and water consumption patterns. The temperatures were constant at 24 C for several days before cyclic temperatures were started. Control broilers continued at 24 C but the treatment was a daily 24-35-24 C cycle for 3 days. Broilers that were 5, 6, or 7 wk old consumed as much feed or water the 1st day of the cycle as on the succeeding days. Feed and water consumption were determined for 6-h periods each day beginning at minimum temperature with two periods during rising temperature and two periods during declining temperature. Feed consumption was depressed when the temperatures were declining. Water consumption increased during the 12 h when the temperature was maximum. At 7 wk, water consumption was greater for broilers on the cyclic temperature for each 6-h period except for the period of temperature decline immediately preceding the minimum temperature. Broilers exposed to the 3 days of cyclic temperatures consumed more water than controls during a subsequent exposure to temperatures up to 40.8 C. The data show that the increased water consumption and decreased feed consumption observed due to high, cyclic temperatures arise from changes that occur during some times of the day and no changes occur during other times. The increase in water consumption precedes the reduction in feed consumption.

Animals↗

PubMed1992

The effect of temperature, dietary energy level, and corn particle size on broiler performance.

Experiments were conducted to study the effect on broiler performance of grinding corn with different hammer mill screen openings (HMSO). Corn for Trials 1 and 2 was ground through HMSO of 3.18 or 9.59 mm and broilers were grown at 15.5 and 26.6 C in Trial 1 and at 26.6 C in Trial 2. Dietary energy levels used from 22 to 42 days were 3,050 and 3,230 kcal ME/kg for Trial 1 and 3,230 and 3,330 kcal ME/kg in Trial 2. In all starter and finisher diets, lysine and sulphur amino acid concentrations were similar on a megacalorie basis. In Trials 3 and 4, HMSO were 3.18, 4.76, 6.35, and 7.94 mm. Corn ground through a HMSO of 9.59 mm significantly reduced body weight and feed:gain ratio in Trials 1 and 2 at 21 days as compared with corn ground through an HMSO of 3.18 mm. At 42 days, body weights were reduced when corn was ground through 9.59- and 3.18-mm HMSO for the starter and finisher diets, respectively, as compared with those fed with the corn ground through a 3.18-mm HMSO in the starter diet. In Trials 3 and 4, significant differences in body weight and feed:gain ratios at 21 days were not noted for feed containing corn ground through an HMSO of 3.18, 4.76, 6.35, or 7.94 mm.

Animal Feed↗

PubMed1992

Effect of periodic feeding and photoperiod on anticipation of feed withdrawal.

Broiler chicks obtained from a commercial hatchery were reared on litter in environmental chambers. The rearing temperature was 32 C initially, and reduced 2,8 C/wk until 24 C was reached. Water was available for ad libitum intake. The treatments began at 7 days in Trial 1 and at 8 days in Trial 2, during which feed and water consumption were recorded by computer every 30 min and summarized for 2- and 24-h periods until each trial was completed. In Trial 1, the treatments were: 1) continuous light with feed available 12 h/day; and 2) 12 h light (L):12 h dark (D) with feed available for ad libitum consumption for 1 wk and unavailable thereafter during darkness. In Trial 2, the treatments were 1) 14L:10D; 2) 10L:14D; and 3) continuous light. During the treatments, no feed was provided during darkness and only for 12 h/day during continuous light. At 29 days, feeding and lighting were again continuously provided until the trial ended at 33 days. Broilers were able to anticipate the period of feed unavailability when it coincided with darkness. They were unable to anticipate the period when feed was unavailable if they were in continuous light. Continuously lighted broilers consumed more feed at the onset of the feeding period than did the broilers in light:dark cycles. Periodically lighted broilers consumed more feed at the end than at the onset of the feeding period. Resumption of continuous feeding occurred more quickly for continuously lighted broilers than for those previously on light:dark cycles. The data indicate that the internal clock that permits broilers to anticipate recurring periods of feed unavailability depends on a daily period of darkness.

Animals↗

PubMed1990

A comparison of flow cytometry and other techniques used for diagnosing Mycoplasma infections.

Mycoplasma isolates from chickens are usually identified by a fluorescent antibody (FA) technique that requires 7 to 10 days from sampling to the completion of identification. The FA procedure uses Mycoplasma-positive antibodies conjugated with fluoroisothiocyanate (FITC) to identify the colonies of the organism on agar. This paper describes a flow cytometric procedure that uses the same antibody-FITC conjugate and can be completed in 3 or 4 days. Broilers and egg-type hens inoculated with Mycoplasma gallisepticum and M. synoviae were swabbed from the choanal cleft and cultures were grown in broth. Broth aliquots were briefly incubated with polyclonal antisera to M. gallisepticum and M. synoviae conjugated with FITC, the same reagents routinely used in the FA technique. The sample was then analyzed by flow cytometry for the association of the fluorescent label and the organism. Samples from inoculated chickens incubated with the homologous antibody-FITC had greater fluorescent intensity than did those incubated with the heterologous antibody-FITC. Diagnosis by flow cytometry was consistent with that by the FA technique except that in one trial one sample was incorrectly identified by flow cytometry as positive for M. gallisepticum, although it was not inoculated with M. gallisepticum. Also, flow cytometry did not correctly identify M. synoviae organisms as readily when broilers were inoculated with both M. gallisepticum and M. synoviae.

Agglutination Tests↗

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↗