Effect of strain and age of the broiler breeder female on incubation time and chick weight.

Two experiments were conducted to evaluate effects of strain [five in Experiment (Exp.) 1 and six in Exp. 2)] and age (29, 47, and 57 wk in Exp. 1 and 29, 41, and 52 wk in Exp. 2) of commercial broiler breeders on incubation time and chick weight. Highly significant differences in egg weight were found among strains in both Exp. After adjusting for effects of egg weight, significant effects of strain, age, and their interactions were found on incubation time, egg weight at transfer, and chick weight at hatch in Exp. 1, but not in Exp. 2. Mean incubation times varied among strains from 496.6 to 498.8 h in Exp. 1 and from 499.3 to 501.9 h in the second experiment. In Exp. 1, incubation time decreased from 498.6 h when breeders were 29 wk to 494.8 at 47 wk, whereas in Exp. 2, it decreased from 510.5 h at 29 wk to 495.1 h at 41 wk. This decrease also resulted in a negative correlation between egg weight and incubation time. Differences due to strain and age were found for yolk and albumen percentage and yolk: albumen ratio. Percentage yolk was 27.2 and 32.7% and percentage albumen was 60.1 and 55.9% in eggs from 29 to 52 wk breeders, respectively. Shell percentage was significantly affected by strain. Strain by age interactions were found for each response in Exp. 1 but only for set and chick weight in Exp. 2. Differences among incubators were found only for incubation time; interactions of incubation time and strain and age were also detected. Results indicate that genotype, age of the female breeder, and incubator should be considered along with their interactions to obtain optimum hatching performance.

Relaxin: an ovarian hormone in an avian species (Gallus domesticus).

The objective of this study was to characterize the biochemical, immunological, and biological activity of avian relaxin and to immunolocalize relaxin-like peptides in the ovary of the hen (Gallus domesticus). A relaxin-like peptide was partially purified from ovaries of actively laying hens by size-exclusion chromatography and further purified by ion-exchange chromatography on CM-cellulose. Those fractions containing relaxin immunoreactivity were identified with the use of a homologous porcine relaxin radioimmunoassay on selected column effluent and pooled, and a sample was subjected to SDS-gel electrophoresis. The SDS-gel-separated proteins were electrotransferred onto a nitrocellulose membrane and immunostained with an antiserum to porcine relaxin which showed the presence of a single band of approximately 6000 daltons. The dose-response curve generated by avian relaxin-like peptide in the homologous porcine relaxin radioimmunoassay was parallel to that produced by the porcine relaxin standard. Like porcine relaxin, avian relaxin-like peptide eluted from the Sephadex G-50 in an elution volume for a molecule of approximately 6000 daltons, was retained on CM-cellulose, and was bioactive in in vitro inhibition of spontaneous contractions of estrogen-primed mouse uterus (a relaxin bioassay). Using an antiserum specific to porcine relaxin, avian relaxin-like peptide was immunolocalized to the granulosa cells of postovulatory follicle from ovary of a hen less than 24 hr postoviposition. No immunostaining was detected in the cells of the largest preovulatory follicles or when the antiserum was preabsorbed with porcine relaxin prior to staining. The finding of this study indicates that the avian postovulatory follicle, like the corpus luteum of other vertebrate species (sharks and mammals), contains a relaxin-like peptide.

Low temperature effects on embryonic development and hatch time.

A series of experiments was conducted to estimate phenotypic correlations between incubation characteristics, and to evaluate the effects of cold stress and genotype during incubation on chick weight, egg weight loss, hatching time, and embryonic mortality. Eggs were cooled at 18 or 24 C, for 12, 24, 36, 48, or 72 h beginning on Day 8, 12, 14, 16, or 18 of incubation. Other eggs were cooled intermittently for 6 h every 48 h or 12 h every 96 h. A control group in each experiment was not cold stressed. Results indicated a low and negative correlation between hatching time and chick weight, and a low and positive correlation between hatching time and weight loss from transfer to hatching when variability due to egg weight was removed. Chick weights at hatching were lower in chicks from cooled eggs than those of chicks from eggs incubated under normal temperature. The chicks from cooled eggs were more susceptible to dehydration during holding in the hatcher. Incubation times were delayed approximately as long as the times of embryonic cooling. Embryonic mortality was significantly increased under continuous (single period) cold stress, but not under intermittent cooling (6 h every 48 h). Significant genotype by environment interactions were found in the response of embryos of various strains to cold stress. Exposure for 36 h or longer had detrimental effects on chick weight and embryo viability, but these effects were modified by interactions among the factors involved. The results indicated that embryos from cooled eggs lose more weight during incubation and that the neonatal chicks are more susceptible to dehydration during holding time, and have a longer incubation period, and a greater embryonic mortality.

Response of broiler breeder females to feed restriction below recommended levels. 3. Characterizing the onset of sexual maturity.

The objective of this study was to characterize how the physical attributes associated with sexual maturity would be affected by feed allocation as female broiler breeders passed through the pullet-layer transition period. Treatments consisted of five feeding programs, or body weight goals, during the period of 0 to 20 wk of age. Those were 8% above breeder standard, standard (primary breeder recommended body weights), and 8, 16, and 24% below standard. The characteristics measured included body and fat pad weights, pubic spread, comb development, head score (comb and wattle appearance), shank length, total plasma lipid concentration, ovary weight, oviduct weight, bursa of Fabricius weight, and age at sexual maturity. The generalized effect of increased severity of the feed restriction programs was to delay the birds' development without altering their ultimate physiological values. The exceptions to this were relative body weight and shank length after maturity, which were reduced in the most severely restricted birds. Measurements of pubic spread and comb growth and subjective scores of head appearance would be useful and easily obtained information when estimating the progression of a flock toward sexual maturity.

Seasonal temperature and its influence on plasma corticosterone, triiodothyronine, thyroxine, plasma protein and packed cell volume in mature male chickens.

1. The relationship between seasonal changes in environmental temperature and hematological parameters was investigated in mature, single comb white leghorn (SCWL) male chickens. 2. Samples of blood plasma, obtained monthly from two groups of birds over two separate 12 month periods, were analysed for corticosterone (CT), 3,5,3'-triiodothyronine (T3), thyroxine (T4), plasma protein (PP), and packed cell volume (PCV). 3. Statistical analyses revealed that blood plasma concentrations of T3 were significantly correlated negatively with monthly dry-bulb temperatures. 4. There were no consistent or significant relationships between monthly dry-bulb temperature and CT, T4, PP or PCV over the two 12 month periods. 5. The results of this study indicate that blood plasma concentrations of T3 are influenced by season of year in mature, male domestic fowl.

Effect of daily restriction and age at initiation of a skip-a-day program for young broiler breeders.

Two experiments were conducted with Cobb feather sex broiler breeders comparing skip-a-day (SAD) feeding programs which began at either 2, 4, 6 or 8 wk of age. A fifth program, daily restriction started at 2 wk of age, was also compared. Chicks hatched in December and July, respectively, in Experiments 1 and 2 were exposed to natural daylight until 20 wk of age. All birds were fed ad libitum until the respective restriction programs began. All grower programs terminated at 20 wk of age. A breeder diet was given daily after 20 wk. Males and females were grown together. Sexual maturity was reached earlier in the 2-wk restriction groups (2-wi SAD in Experiment 1 and the 2-wk daily restriction in both experiments) than in the 8-wk SAD group. Egg production in Experiment 1 was also improved by the early restriction. Fertility and hatchability were not significantly affected by treatment. Based on the results of these experiments a SAD program beginning at 2 wk of age was as good as or better than one initiated at later ages. The 2-wk daily restriction program was equivalent to the 2-wk SAD program.

Feeding time and body temperature interactions in broiler breeders.

Four groups of 70-wk-old broiler breeder females were fed once daily at 0600, 1000, 1400, and 1800 h to determine the effect of feeding time and eating on body temperature. The photoperiod was from 0430 to 1930 h. Four floor pens of 30 hens each were assigned per feeding time. Following a 9-day adjustment period, body temperature was determined, in series, by rectal probe of 5 birds/pen at 7 and 3 h prefeeding and 1, 5, 9, and 13 h postfeeding. Body temperature was increased .5 C at 1 h postfeeding in all groups and at 5 h postfeeding in the 0600-h fed group. The rate of feed consumption was fastest with afternoon feeding. Four 1-yr-old broiler breeder males were implanted with an FM radio transmitter for monitoring body temperature and housed in an environmental control chamber. Body temperature was monitored when the birds were fed at 0600, 1000, 1400, and 1800 h. The chamber temperature cycled from 22.2 to 33.3 C (22.2 C: 2200 to 0800 h; 33.3 C: 1200 to 1600 h; 27.8 C: 0800 to 1200 h and 1600 to 2200 h). Lights were on from 0430 to 1930 h. Body temperature changes were also monitored under constant temperature (27.8 C) and light for birds fed ad libitum or at 1000 h. Body temperature increased as much as 1.5 C following feeding and reached a maximum at 5, 4, 3, and 2 h postfeeding at feeding times of 0600, 1000, 1400, and 1800 h, respectively. Males unable to feed displayed a significantly increased body temperature when they observed other birds eating. A specific body temperature response to feeding activity was observed only when males were fed once daily under constant environment.

Lighting of end of lay broiler breeders: fluorescent versus incandescent.

An 18-week experiment was conducted to investigate the effects of changing from incandescent to fluorescent lighting on egg production, egg weight, fertility, and hatchability of end of lay broiler breeders housed in an open-sided house. Forty-eight-week-old Cobb feather-sexed broiler breeders were housed, 30 females and 3 males per pen, in a total of 28 pens. Incandescent lights had been used previously, so pens were randomly assigned to either fluorescent or incandescent lights giving 20 lx of light at bird level. Lights used were 60 W incandescent and 22 W fluorescent cool-white circular. Body weight and egg production were measured weekly, and fertility, hatchability, and egg weight were determined monthly from 48 to 65 weeks of age. No significant treatment effects were observed on body weight, fertility, hatchability, or egg weight. A significant reduction in egg production was observed with fluorescent lighting from Weeks 58 to 65. The reduced egg production indicated it was detrimental to change from incandescent to cool-white fluorescent lighting.

Feeding pattern responses to changes in dietary energy or environmental temperature in the domestic fowl.

Two experiments using 64-week-old Single Comb White Leghorn roosters were conducted to determine the meal response to an abrupt change in dietary energy or environmental temperature. In the first experiment, dietary energy level was changed from 200 kcal to either 250 or 150 kcal/75 g. In the second experiment, environmental temperature was changed from 22.2 C to either 13.3 or 30.0 C. Feeding behavior was recorded throughout both experiments. Meal size, meal frequency, and time spent eating a meal were measured. Roosters changed to high-energy or low-energy diets consumed low or high amounts of feed, respectively. Those fed the high-energy diet tended to decrease meal size and meal duration and to increase the number of meals. Roosters changed to the low-energy diet decreased meal size and meal duration and increased the number of meals eaten. The results tend to confirm the chemostatic mechanism in birds as food intake was related to energy in the diet. Roosters changed to high or low environmental temperature responded by decreasing or increasing their feed intake, respectively. Roosters changed to a high environmental temperature significantly decreased meal size, meal duration, and increased the number of meals. Those changed to a low environmental temperature significantly increased meal size and decreased meal frequency and meal duration.

Dietary self-selection of laying hens inadequate to overcome the effects of high environmental temperature.

Two environmental temperatures, 21 and 30 C, were used during a 28-day experimental period. There were two groups of hens in each temperature treatment. The control groups (C) were given a conventional balanced diet and each dietary self-selection group (S-S) was provided, on an individual hen basis, three diets each one being high in energy, protein, or calcium. The S-S groups had significantly reduced egg production, which probably resulted from the significantly reduced protein intake. Egg weight and energy intake were reduced in the S-S group at 21 C while calcium intake and egg shell strength at 30 C were higher as compared to the corresponding C group. Dietary self-selection did not enable hens to regulate nutrient intake for comparable performance to hens provided one balanced diet. Also, the detrimental effects of high environmental temperature were not overcome by dietary self-selection.

Performance of laying turkeys grouped according to daily food intake.

The individual food intake of 120 Large White turkey hens in cages was measured for 3 weeks for 36 to 39 weeks of age. Based on that rate of intake, hens were divided into four treatment groups: two high intake (HI) and two low intake (LI). A control diet was fed to one HI group and one LI group. In addition, diets with different nutrient density were formulated for one HI group and one LI group. The experimental period was for 10 weeks beginning when the hens were 39 weeks of age. There were no significant differences among the groups for rate of egg production, total number of eggs, egg weight, or egg specific gravity, although there were significant differences for the daily intakes of protein, sulfur amino acids, lysine, phosphorus, calcium, and metabolizable energy. These data indicate that, at 39 weeks of age, there was no benefit from grouping birds based on previous food intake and feeding them diets to increase or decrease daily intake of certain nutrients.

Metabolic responses of the rooster after exogenous thyroid hormones.

Total sensible heat loss, O2 consumption, and CO2 production were monitored in 20 White Leghorn roosters (1.85 +/- .05 kg body weight) subjected to either saline, or triiodothyronine (20 micrograms/kg; T3), or thyroxine (50 micrograms/kg; T4) administered in a single dose. Treatment occurred after a 26-hr fast and the fast was maintained for the duration of the experiment. Plasma T3 concentrations in birds treated with T3 were higher than controls for an 8-hr period after treatment (P less than .01). Plasma T4 in birds treated with T4 was higher than controls for the 24-hr sampling period (P less than .01). Sensible heat loss, but not O2 consumption or CO2 production, was affected by treatment during the first 10 hr following treatment (P less than .05). Heat loss after T3 and T4 treatments did not differ; however, pooled results of the treated groups were higher than that of control (P less than .05). Heat loss, O2, and Co2 varied with time (P less than .001) during the 10-hr period following treatment or saline. Sensible heat loss was also affected by treatment during the period of 21 to 25-hr posttreatment (P less than .001). During that period, the heat loss after T4 treatment was greater than that after T3 (P less than .005). These data suggest that a single administration of either T3 or T4 can affect total sensible heat loss but not O2 consumption of CO2 production within 10-hr posttreatment in mature roosters.

Cyclic changes in plasma phosphorus of laying turkeys.

Plasma phosphorus of laying turkeys measured at 0, 6, 18, and 24 hr after oviposition showed a cyclic pattern similar to that reported for laying chickens. Plasma phosphorus was lowest at oviposition and remained relatively low until 6 hr postoviposition; values at 18 and 24 hr postoviposition were higher. Plasma phosphorus was higher (P less than .05) 24 hr postoviposition than 0 or 6 hr postoviposition. The changes were assumed to be associated with egg shell calcification and bone resorption. Plasma phosphorus values of turkey toms measured during a 24-hr period remained constant and were not significantly (P less than .05) different from each other.

The effect of CO2 and temperature on respiratory movements in the chicken.

We studied the effect of increasing colonic temperature (Tc) on respiratory amplitude and frequency at different levels of PICO2 in anesthetized, unidirectionally ventilated cockerels. We also evaluated the relationship between PICO2 and PaCO2. Increased PaCO2 augmented respiratory amplitude and decreased frequency at every Tc. Respiratory amplitude increased as Tc rose from 41 to 45 degrees C at each level of PaCO2. During the same rise in Tc, respiratory frequency decreased at the low PaCO2 seen in awake, panting cockerels but increased at eucapnic PaCO2. Tc had no effect on frequency at high PaCO2. Values for respiratory frequency of unidirectionally ventilated cockerels at given Tc and PaCO2 predict those of awake cockerels. We conclude that amplitude of breathing increases in acute hyperthermia unless accompanied by hypocapnia and that without hypocapnia maximal panting frequencies cannot be reached.

Respiration during hyperthermia in the chicken as influenced by an increase in inhaled CO2.

Respiratory rate was measured in unanesthetized, adult hens when abruptly exposed to 1.5% CO2 as they were responding to an environmental temperature of 38 C. Inhalation of 1.5% CO2 greatly depressed respiratory rate at high panting rates, but produced only slight changes during the lower, but sharply increasing, rates of respiration. The initial portion of the panting response appears to be mostly controlled by the respiratory drive initiated by thermoreceptors while higher respiratory rates seem to be more affected by chemical changes.

Are avian intrapulmonary CO2 receptors chemically modulated mechanoreceptors or chemoreceptors?

Openings of paleopulmonic parabronchi in paralyzed, unidirectionally ventilated geese were photographed through small holes in the birds' mediodorsal secondary bronchi during single-unit recording from intrapulmonary CO2 receptors. Changes in the discharge frequency of the receptors as fractional CO2 concentration of ventilating gas was alternated between 0 and 0.05 were compared with the changes in cross-sectional areas of randomly selected parabronchial lumina. Intrapulmonary CO2 receptors, similar to those found in other avian species, are also present in geese. Changes in intrapulmonary CO2 concentration greatly influenced the discharge of these receptors but did not induce movement of parabronchial smooth muscle in this region of the lung. If most of the receptors are located in the paleopulmonic parabronchi, as currently appears to be the case, we must conclude that changes in receptor discharge in response to changes in intrapulmonary CO2 concentration do not result from mechanical distortion of the receptors induced by smooth muscle contraction; intrapulmonary CO2 receptors appear to be true chemoreceptors.

Alleviation of fluorine toxicity in starting turkeys and chicks with aluminum.

Aluminum (Al) compounds were evaluated as fluorine (F) toxicity alleviators in starting broiler chicks and turkeys. Added F levels from NaF ranged from 0 to 1000 ppm, whereas Al levels varied from 0 to 800 ppm. Al was fed either as Al2O3 or Al2 (SO4)3.18H2O. When fed as the sulphate salt, 800 ppm of Al completely prevented the toxic effect of at least 1000 ppm of F. Al2O3 was not effective as an alleviator of fluorine toxicity. When the mode of action of Al2(SO4)3.18H2O against F toxicity was studied in colostomized turkeys it was apparent that F absorption occurred but was probably less efficient than previously reported in ruminants. Al significantly (P less than .05) reduced F absorption in turkeys. Urinary F levels were: 2.4 ppm in birds fed a control diet (26 ppm F), 17.8 ppm in birds fed a diet with 1000 ppm F, and 6.7 ppm in birds fed the high F diet with 800 ppm Al as the sulphate salt. In addition, data from this study indicated that starting broiler chicks were more tolerant (800 ppm F) than starting turkeys (600 ppm F) to fluorine toxicosis.

Energy requirement of roosters as influenced by environmental temperature, dietary energy and age.

Little information is available on the energy requirement of roosters. The voluntary energy intake is reported for roosters exposed to environmental temperatures of 23, 30 or 37 degrees C. while fed one of three diets differing in energy level. There was a reduction in the energy intake as the environmental temperature increased. The data indicated that the energy requirement was reduced somewhat as the birds get older than 9-10 months of age.