Stocking density and physiological adaptive responses of broilers.

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

Ocular responses to ammonia in broiler chickens.

In two trials, 60 male commercial broilers were placed in each of eight environmentally controlled chambers receiving 0, 25, 50, or 75 ppm aerial ammonia from 1 to 28 days. Birds exposed to 25 ppm (lower concentration) ammonia gas developed ocular abnormalities but at a slower rate when compared with birds exposed to 50 and 75 ppm (higher concentrations). Birds exposed to higher concentrations also developed more severe lesions. With little atmospheric ammonia present after 28 days of the grow-out stage, the corneas indicated signs of healing. Lymphocytes and heterophils were seen in the iris at 49 days in ammonia-exposed birds even when ammonia exposure was terminated at 28 days. The lower ammonia concentrations resulted in abnormalities that were slight when compared with those seen at the higher ammonia concentrations. As measured by the incidence of inflammatory infiltrates in the trachea, lung, and air sacs, respiratory tract tissues did not appear to be affected by any tested level of aerial ammonia. The findings in this investigation represent the first report indicating that ammonia-induced uveitis in chickens clears rapidly after exposure to ammonia ceases.

Live performance of male broilers subjected to constant or increasing air velocities at moderate temperatures with a high dew point.

This study examined the effects of varying air velocities vs. a constant air velocity with a cyclic temperature curve of 25-30-25 degrees C and a dew point of 23 degrees C on broilers from 28 to 49 d of age. Four replicate trials were conducted. In each trial, 742 male broilers were randomly allocated to 6 floor pens or 2 air velocity tunnels, with each tunnel consisting of 4 pens. Bird density, feeder, and waterer space were similar across all pens (53 birds/ pen; 0.07 m2/bird). The treatments were control (still air), constant air velocity of 120 m/min, and increasing air velocity (90 m/min from 28 to 35 d, 120 m/min from 36 to 42 d, and 180 m/min from 43 to 49 d). Birds grown in a still air environment gained less weight, consumed less feed, and converted feed less efficiently between 28 and 49 d than birds subjected to moving air (constant or increasing). Growth responses between the air velocity treatments were similar from 28 to 35 and 36 to 42 d of age. Increasing air velocity to 180 m/min improved (P < or = 0.02) the growth rate of broilers from 43 to 49 d of age over birds receiving an air velocity of 120 m/min, but the incidence of mortality was not affected. These results provide evidence that increasing air velocity from 120 to 180 m/min is beneficial to broilers weighing 2.5 kg or greater when exposed to moderate temperatures.

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

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

Growth responses of male broilers subjected to increasing air velocities at high ambient temperatures and a high dew point.

This study examined live performance responses of male broilers to increasing air velocity of 120 and 180 m/min reared under high cyclic temperatures (25-35-25 degrees C) with a 23 degrees C dew point from 21 to 49 d. Birds were reared in an environmental facility containing 2 wind tunnels (4 pens/tunnel) and 6 floor pens (control). At 21 d, 53 birds were placed in each pen of the wind tunnels and control group, respectively, and growth performance was determined weekly. Increasing air velocity from 120 to 180 m/min improved BW and BW gain from 29 to 35, 36 to 42, and 43 to 49 d of age leading to a cumulative advantage of 287 g in BW gain and a 10-point difference in feed conversion from 21 to 49 d of age. Subjecting birds to air velocity improved growth rate, feed consumption, and feed conversion at each weekly interval from 28 to 49 d over the control birds. These results indicate that male broilers approximating 2.0 to 3.0 kg respond to an air velocity of 180 m/min when exposed to high cyclic temperatures.

A self-propelled, constant-speed spray vaccinator for commercial layer chickens.

Vaccination of commercial layer chickens is labor intensive and often results in poor rates of seroconversion, which, in turn, generally correlate with decreased flock uniformity and performance. Attempts to improve the vaccination process include numerous variations of individual shop-built vaccinators in use by the layer sector of the poultry industry. Each of these vaccinators has limitations that contribute to poor vaccinations. Major problems include the nonuniform speed of the applicator system and pressure fluctuations at the spray nozzles, which contribute to sporadic dispersion of the vaccine as the vaccinator is pushed or carried past the cages. A battery-powered, self-propelled, constant-speed vaccinator was designed and constructed that operates with constant nozzle pressure. In field use, this vaccinator has resulted in both labor savings (reduction of manpower from five to one to vaccinate 75,000 chickens) and time savings (from 45 min to 7.5 min/poultry house) as well as improved vaccination results (higher positive seroconversion rates) against the poultry pathogen Mycoplasma gallisepticum (MG), a bacterium associated with losses of 15.7 eggs/hen over a 45-wk laying period in MG-infected layers as compared with layers maintained free from infection with MG.

Atmospheric ammonia is detrimental to the performance of modern commercial broilers.

Atmospheric ammonia inhibits broiler performance. Quantified effects are based on older genetic stock with a BW of 2000 g at 7 wk. In contrast, modern genetic stock reaches 3200 g at 7 wk of age. To assess the impact on present day broilers, 2 trials were conducted exposing male broilers to graded levels (0, 25, 50, and 75 ppm) of aerial ammonia from 0 to 4 wk of age. Sixty, 1-d-old chicks were placed in environmentally controlled chambers, weighed weekly as a group, and processed with yield determined at 7 wk of age. Final BW was significantly depressed by 6 and 9% for the 50 and 75 ppm concentrations of ammonia as compared with 0 ppm. Also, mortality was significantly greater at the 75 ppm ammonia concentration, 13.9% compared with 5.8% for the 0 ppm treatment. Percentage yield of deboned meat per bird decreased slightly with increasing exposure to ammonia but was not statistically significant. Although current genetic stock reaches growout weights that are approximately 60% greater than those 2 decades ago, the relative quantified effects of ammonia exposure were similar. Additionally, statistical analysis of the results provided a simple equation, presented herein, for predicting the decline in BW of male broilers after exposure to ammonia.

Total and water-soluble phosphorus in broiler litter over three flocks with alum litter treatment and dietary inclusion of high available phosphorus corn and phytase supplementation.

Three pen trials were conducted to determine the main effect of alum addition to litter on form of poultry litter P using a 2 x 2 factorial structure of the subunit treatments: diets including high available phosphorus/low phytate corn (HAPC) and phytase (PHYT). Male broilers (1,760 per flock) were grown to 42 d having starter diets with 0.45% available P and grower diets with 0.35% available P. In the first trial, total litter P (tP) was greatest for the yellow dent corn (YDC) diet (12 g/kg) and least for the HAPC and PHYT combination (H&P) diet (6.9 g/kg) with the individual PHYT and HAPC diets falling in between at 9.1 g/kg and 9.4 g/kg tP. Also in the first trial, the litter water-soluble P (wP) was highest for PHYT (2.8 g/kg), least for the HAPC and H&P diets (1.5 g/kg) with the YDC diet falling between (2.2 g/kg). Alum was added to the litter after the first experiment. In the second and third experiments, alum inclusion significantly reduced the wP when compared with the treatments with no alum. In the third trial, the least wP was present in the alum-HAPC treatment. Phytase, YDC, and HAPC diets with no alum litter treatment generated the most wP. Since these diets appear to have little or no difference with respect to quantity of wP, this work suggests that form of litter P generated by alternative diets should be considered as criteria when attempting to reduce P in broiler litter applied to land.

The effects of high-air velocity on broiler performance.

Two trials using a total of 1,484 Ross male broilers were conducted to study the effect of air velocities of 180 and 120 m/min versus still air (<15 m/min) on BW gain (BWG) and feed:gain from 3 to 7 wk of age. Broilers were raised in a common environment to 3 wk of age. The experimental facility was a closed sided house containing eight wind tunnel floor pens and six floor pens. There were two wind tunnels (four pens/tunnel) used to test air velocities of 180 or 120 m/min. At 3 wk of age, 53 birds were placed in pens on litter in each of two wind tunnels (four pens/tunnel) or on litter in floor pens (six pens) in an environmentally controlled facility. All floor pens contained 3.75 square meters of floor space, one tube feeder, and one trough waterer. The temperature regimen was a diurnal cycle of 25-30-25 C with 23 C dewpoint. Air velocities of 180 and 120 m/min had no significant effect on BWG or feed:gain during the first week (3 to 4 wk) in the tunnels as compared with the still air. However, significant improvements were noted in BWG and feed:gains for increased air velocities from 4 to 5 and 5 to 6 wk of age. During the last week (6 to 7), an air velocity of 180 m/min significantly improved BWG and feed:gain, as compared with the 120 m/min or the still air.

Effects of F-strain Mycoplasma gallisepticum inoculation at twelve weeks of age on performance and egg characteristics of commercial egg-laying hens.

The effects of F-strain Mycoplasma gallisepticum (FMG) inoculation during the pullet period on the subsequent performance and egg characteristics of commercial Single Combed White Leghorn hens were evaluated. In two trials, BW, feed consumption, egg production (EP), egg weight, egg size class, relative eggshell water vapor conductance, and relative percentages of eggshell, yolk and albumen weights were determined through approximately 60 wk of age. In each trial, pullets at 12 wk of age were randomly assigned to negative pressure biological isolation units. Birds in one-half of the total units were inoculated with FMG, and the other half were sham-inoculated with sterile media. In both trials, onset of lay was delayed approximately 1 wk in layers inoculated with FMG. Control birds that had not been previously inoculated with FMG laid their first egg at 18 wk of age, while birds that had been previously inoculated with FMG laid their first egg at 19 wk of age. In Trial 1, FMG-inoculated hens laid significantly fewer total eggs, which became apparent at each week after Week 42. In Trial 2, a numerical decrease in total EP occurred, and the percentage of undersized eggs laid by FMG-inoculated birds was significantly lower at 19 wk of age but was higher at 20 and 21 wk when compared to controls. Mortality was not significantly different between the treatments in either trial. These data demonstrate that when birds are housed in isolation facilities and inoculated with FMG at 12 wk of age, onset of lay is delayed. These data also suggest that FMG may lead to delays in undersize EP and decreases in total EP. However, because significant FMG effects on these parameters were observed in only one trial, additional studies may be necessary to verify these effects.

The effects of 6/85 live Mycoplasma gallisepticum vaccine in commercial layer hens over a 43-week laying cycle on egg production, selected egg quality parameters, and egg size distribution when challenged before beginning of lay.

In each of two trials, 80 commercial leghorn-type pullets were separated into two treatments with four replicates of 10 chickens in each treatment. Forty pullets were designated as controls and received no inoculation, whereas the remaining 40 pullets received the 6/85 vaccine strain of Mycoplasma gallisepticum (MG) at 10 wk of age. Hen-day egg production, egg weight, eggshell strength, Haugh unit score, pimpling incidence, and blood/meat spot incidence were monitored and recorded weekly in each trial through an entire laying cycle of 43 wk. Further, eggs from all treatments were collected daily, Monday-Thursday, and individually weighed. No significant difference was observed between the treatments for 43-wk means for hen-day egg production, for any of the monitored egg or eggshell quality parameters, or for the number of extra large, large, medium, small, pee wee, or undergrade egg sizes. A significant (P < or = 0.05) difference was observed for the number of jumbo-sized eggs between the two treatments. Results of this study suggest that vaccination of commercial layer chickens at 10 wk of age with 6/85 strain MG does not detrimentally impact egg production, egg size distribution, or ovary/oviduct function as evidenced by selected egg parameters monitored in this study.

Relating weight gain and feed:gain of male and female broilers to rearing temperature.

The effects of environmental temperature on growth and feed:gain were studied in three trials each for male and female broilers. Chicks were reared in a common environment to 21 d of age. At 21 d, they were randomly allocated to 10 environmental chambers. Each chamber was maintained at a constant temperature; the chambers ranged from 12 to 30 C in two-degree increments. The dewpoint was maintained at 18 C, except that relative humidity was not permitted to exceed 82.9%. Body weight was determined at 21 d. Weight gain and feed:gain were determined at 28, 35, 42, and 49 d. The data were analyzed statistically, and regression equations were obtained for weight gain and feed:gain for each sex. Equations were based on body weight and temperature, and the body weight equations were plotted as grams gained per bird per day. Feed:gain increased with increasing weight. The temperature that resulted in the most favorable feed:gain decreased with increasing weight. These results support lower rearing temperatures for optimum growth and feed:gain by large broilers than those of other reports in the literature.

The effect of nipple height on broiler performance.

Two trials, using a total of 3,200 male broilers, were conducted to compare the effects of a trough drinker versus three different heights on a nipple drinker system on body weight gain and feed:gain. The broilers were housed in temperature-controlled litter pens at 25 or 30 C. An 8-ft open trough was used. The nipple drinker heights were adjusted as 1) low (no neck stretch and drink from the side of the beak), 2) medium (stretch neck and drink from the end of the beak), and 3) high (first elevate breast, then stretch neck and drink from the end of the beak) positions. The nipple heights were adjusted twice weekly by visual inspection. The open drinker produced the heaviest birds. No significant treatment differences were observed for feed:gain at 25 C but increased numerically with increasing nipple height. This same pattern was evident at 30 C, but statistically significant differences did occur. Drinking from a nipple drinker is an unnatural drinking act for birds, and the greater the neck extension, especially during a panting situation, the more detrimental the effect on both body weight and feed:gain.

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.

The effects of ts-11 strain Mycoplasma gallisepticum vaccination in commercial layers on egg production and selected egg quality parameters.

Live Mycoplasma gallisepticum (MG) vaccines have been USDA approved and licensed for use in commercial layer chickens since 1988; however, egg production and egg quality data exist only for the F strain of MG. Information pertinent to the effects of ts-11 MG on egg and eggshell quality parameters, as well as egg size distribution, is lacking. In this study, pullets were inoculated at 10 wk of age with ts-11 strain MG and placed in biological isolation units at 10 birds/unit. Hen-day egg production, eggshell strength, Haugh unit score, pimpling incidence, and blood/meat spot incidence were monitored and recorded in each trial through a 45-wk production cycle. Further, eggs from all treatments were collected daily, Monday-Thursday, and individually weighed. Results of this study indicate that no significant difference was observed between the treatments for the parameters measured or for egg size distribution. Therefore, these data should lessen producers' concerns pertaining to the impact of ts-11 strain MG on egg production, egg and eggshell quality parameters, and egg size distribution.

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.

Effects of age at inoculation and induced molt on the recovery of Mycoplasma gallisepticum from layer chickens.

An experiment was conducted to determine the effects of age at inoculation and induced molt on the reisolation of Mycoplasma gallisepticum (MG) from commercial leghorn hens that had been eyedrop-inoculated with F strain MG at either 10 or 66 wk of age. Chickens were maintained in biological isolation units from 10 wk of age through 78 wk of age. At 70 wk of age (premolt), hens were swabbed, cultured for MG, and molted. Swabs were taken both at the end of molt (postmolt [74 wk]) and again 4 wk later (postmolt+4 [78 wk]). A significant (P < or = 0.05) decrease in MG isolations was observed in the postmolt swabs as compared with the premolt swabs of hens inoculated at either 10 or 66 wk of age. A significant (P < or = 0.05) increase in isolations was observed in the postmolt+4 swabs as compared with the postmolt swabs of hens inoculated at either 10 or 66 wk of age. For the hens inoculated at 10 wk, no significant difference was found in premolt as compared with postmolt+4 MG isolations; however, for hens inoculated at 66 wk, a significant (P < or = 0.05) decrease was observed between premolt and postmolt+4 isolations. Significantly (P < or = 0.05) fewer MG isolations were obtained from the premolt swabs of hens inoculated at 10 wk as compared with hens inoculated at 66 wk. No significant difference in MG isolations was observed in either the postmolt or postmolt+4 swabs between hens inoculated at either 10 or 66 wk.

The effects of F strain Mycoplasma gallisepticum, Mycoplasma synoviae, and the dual infection in commercial layer hens over a 44-week laying cycle when challenged before beginning of lay. II. Egg size distribution.

In each of two trials, 160 commercial pullets were separated into four treatments with four replicates of 10 chickens in each treatment. Forty pullets were designated as controls and received no inoculation; 40 pullets received F strain Mycoplasma gallisepticum (FMG); an additional 40 pullets received Mycoplasma synoviae (MS); and the final 40 pullets were inoculated with both FMG and MS (dual). All inoculations occurred at 10 wk of age. Eggs from all treatments were collected daily, Monday-Thursday, and individually weighed. No significant difference was observed among the treatments for percentages of jumbo, extra-large, medium, small, peewee, or undergrade eggs. As a percentage of eggs laid for the 4 days of each week over the 44-wk laying cycle of each trial, the FMG hens laid significantly fewer large size eggs (43.2%) as compared with either controls (51.17%) or dual-infected hens (49.95%). No significant difference was found in percentage of large eggs laid by FMG hens when compared with MS hens.

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.

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.