Biomedical subjects

J D May

Publications and source records attributed to J D May.

At least 19 recordsLinked to original sources

PubMed2000

The effect of air velocity on broiler performance and feed and water consumption.

Two trials were conducted to determine the effect of air velocity on feed and water consumption at a constant temperature of 27 C and a daily cyclic temperature of 22-32-22 C. Air velocity over the broilers was <15 or 120 m/min. These temperature and air velocity treatments were arranged in a 2 x 2 factorial design in eight environmental chambers, with two replications of each treatment. The air velocity treatments were applied, and total feed and water consumption and daily patterns of consumption were determined for broilers from 21 to 49 d of age. Broilers exposed to the high air velocity consumed less water and more feed, gained more weight, and had an improved feed:gain ratio. The high air velocity had little effect on daily patterns of feed and water consumption. Both feed and water consumption were depressed during the peak of the daily cyclic temperature.

Aging↗

PubMed2000

The effect of environmental temperature on growth and feed conversion of broilers to 21 days of age.

Temperature during rearing is a major factor in production efficiency for broilers. The objective of this research was to determine the effect of five temperature regimens on the growth, feed conversion, and mortality of broilers to 21 d of age. This information is needed to select the most profitable conditions for broiler production. Three trials were conducted in 10 environmental chambers; five chambers were stocked with males, and five were stocked with females. The chambers were initially set at 28, 29, 30, 31, and 32 C followed by daily reductions of 0.3 C for each beginning temperature. The dewpoint was set at 15.7 C throughout the experiments. Lighting was continuous, and feed and water were provided ad libitum. Weight gain and feed conversion were determined at 7, 14, and 21 d, and mortality was recorded as it occurred. Temperature did not affect weight gain or feed conversion for any period, but males were superior to females for these parameters for the 7- to 14-d and 14- to 21-d periods. Temperature affected mortality; most of the deaths occurred during the 0- to 7-d period and at the lowest temperature treatment. These results suggest that mortality is the best indicator of the effect of rearing temperature on performance.

Animal Feed↗

PubMed1998

Air velocity and high temperature effects on broiler performance.

Three trials, using a total of 1,320 male broilers, were conducted to study the effect of air velocity at 125 m/min on body weight gain and feed: gain. The broilers were placed on litter in pens in a wind tunnel or on litter in floor pens with conventional cross ventilation when 4 wk old. Except for air velocity, the conditions in the floor pens and the tunnel were the same. In Trials 1 and 2, only nipple waterers were used. In Trial 3, one-half of the pens on the floor and one-half of the pens in the tunnel were equipped with trough waterers; the remaining pens were equipped with nipple waterers. When compared with conventional ventilation, tunnel rearing improved body weight gain and feed:gain in all three trials. In Trial 3, waterer type did not significantly affect body weight gain or feed:gain in the tunnel. However, body weight gain and feed:gain were reduced in floor-reared birds using nipple waterers as compared with birds using trough waterers. The increased panting of the conventionally ventilated birds, as compared with the tunnel-ventilated birds, may have contributed to their decreased body weight gain and improved feed:gain. The lower body weights may occur because of the difficulty the birds experience when drinking from nipples while panting.

Animals↗

PubMed1998

The effect of environmental temperature and body weight on growth rate and feed:gain of male broilers.

High environmental temperatures are detrimental to the growth and feed:gain of broilers. The objective of this research was to determine the effects of incremental differences in environmental temperature on growth and feed:gain. The data are needed for decisions about the profitability of energy inputs when managing the housing environment. In Trial 1, broiler chicks were reared as a group to 21 d on litter with constant lighting and with water and feed available for ad libitum consumption. They were then moved to 10 environmental chambers. Each chamber was set at a different temperature ranging from 21.1 C to 31.1 C in 1.11 C increments. Weight gain and feed:gain were determined when the broilers were 28, 35, and 42 d old. In Trials 2 and 3, broilers were placed in the environmental chambers, and weight gain and feed:gain were determined for the 42 to 49 d period. The data were analyzed statistically, and regression equations were obtained for growth and feed:gain. Equations were based on body weight and temperature, and the body weight equation was plotted as grams gain per bird per day. Feed:gain was plotted for that body weight and temperature. Body weight gain per day increased to a maximum with increasing weight and then declined. The body weight at the maximum rate of gain was inversely related to temperature. Feed:gain increased as body weight increased. Feed:gain was directly related to temperature at weights above 800 g and the effect of temperature increased as body weight increased. The data will be useful for the evaluation of various management scenarios to determine the inputs that are profitable.

Adaptation, Physiological↗

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↗