Effect of molting method and dietary energy on postmolt performance, egg components, egg solid, and egg quality in Bovans White and Dekalb White hens during second cycle phases two and three.

Two experiments of 4 x 2 x 2 factorial arrangements of 4 dietary energy levels, 2 molting methods (feed withdrawal and no salt diet), and 2 strains (Bovans White and Dekalb White) were conducted to determine the effect of dietary energy and molting method on long-term postmolt performance of 2 strains of commercial Leghorns. In experiments 1 and 2, Bovans White hens (n = 576) and Dekalb White hens (n = 576) were randomly divided into 16 treatments (6 replicates of 12 birds per treatment). Experiment 1 lasted from 86 to 96 wk of age, and experiment 2 lasted from 100 to 110 wk of age. Bovans White hens had significantly higher egg production than Dekalb White hens, whereas Bovans White hens had significantly lower egg weight, percentage of eggshell, and egg specific gravity than Dekalb White hens. Based on improved feed conversion, dietary energy of 2,846 kcal of ME/kg appeared to be enough for optimal performance during second cycle phase 2. Based on BW of hens, dietary energy level for optimal performance should be less than 2,936 kcal of ME/kg during second cycle phase 3. There can be no fixed ideal dietary energy level for optimal profits for postmolt egg production. Molting method had no effect on egg production and egg mass during the early and middle stages of the postmolt production period. However, hens molted by feed withdrawal had significantly higher egg production and egg mass during the later stage of the postmolt production period compared with hens molted by a no salt diet. There was no significant difference in egg specific gravity due to molting method. Feeding a no salt diet resulted in reasonable long-term postmolt performance and eggshell quality, rather than optimal performance and eggshell quality.

Effect of dietary energy on performance and egg composition of Bovans White and Dekalb White hens during phase I.

A 4 x 2 factorial experiment with 4 dietary energy levels (2,719, 2,798, 2,877, and 2,959 kcal of ME/ kg) and 2 strains (Bovans White and Dekalb White) was conducted to determine the effect of dietary energy on reproductive performance, egg composition, and profits of 2 strains of commercial Leghorns. This experiment lasted 16 wk. Bovans White hens (n = 768) and Dekalb White hens (n = 768) in phase I (21 wk of age) were randomly assigned into 8 treatments (16 replicates of 12 birds/treatment). Bovans White had significantly higher feed intake, egg production, egg mass, body weight, percentage egg yolk, and yolk/albumen ratio than Dekalb White. Bovans White had significantly lower feed conversion, egg weight, egg specific gravity, percentage of albumen weight, percentage of shell weight, and Haugh unit than Dekalb White. When dietary energy increased from 2,719 to 2,956 kcal of ME/kg, hens adjusted feed intake from 107.6 to 101.1 g/hen per day to achieve a constant energy intake so that the same amount of dietary energy (5.8 kcal) was used to produce 1 g of egg. Increasing dietary energy by the addition of poultry oil increased early egg weight, which was mostly due to increased yolk weight. Increasing dietary energy by addition of poultry oil significantly decreased feed conversion and egg specific gravity but had no effect on egg production, egg mass, body weight, or mortality. Increasing dietary energy by addition of poultry oil to a ratio of 282 kcal of ME/g lysine maximized egg weight during phase I. The energy per lysine ratio required for optimal profits varied with egg price and feed ingredient prices, which were variable.

Effects of beta-mannanase in corn-soy diets on commercial leghorns in second-cycle hens.

beta-Mannanase (Hemicell) is a unique enzyme-based feed ingredient that can hydrolyze beta-mannan, an antinutritional fiber in feed. Because soybean meal contains beta-mannan and its derivatives, addition of beta-mannanase may improve soybean-meal utilization. The purpose of this study was to evaluate the effect of beta-mannanase on performance of commercial Leghorns fed corn-soybean meal based diets. In this experiment, 3 diets were formulated. The metabolizable energy content for diet 1 (high-energy diet) was 2,951 kcal/kg, which was 120 kcal/kg higher than diet 2 (low-energy diet supplemented with beta-mannanase) and diet 3 (low-energy diet without beta-mannanase). Hy-Line W-36 hens (n = 720, 98 wk old) were randomly divided into 3 dietary treatments (16 replicates of 15 hens per treatment). The trial lasted for 12 wk. Overall average feed conversion of hens fed the low-energy diet supplemented with beta-mannanase was similar to that of hens fed the high-energy diet, and both were significantly lower than that of hens fed the low-energy diet without beta-mannanase. There were no significant differences in overall average egg production and egg mass among 3 dietary treatments for the 12-wk period. However, the addition of beta-mannanase significantly increased average egg production and egg mass of hens fed the low-energy diet from wk 5 to 8. There were no significant differences in feed intake, egg specific gravity, egg weight, mortality, body weight, and body weight variability among the 3 dietary treatments. beta-Mannanase supplementation improved energy utilization of corn-soybean layer diets and has potential to reduce the cost of practical laying hen diets containing beta-mannan.

The influence of the light transmission properties of plastic window coverings on broiler pigmentation.

An experiment was conducted to determine the effect of different window coverings on broiler pigmentation. Equal numbers of male and female broilers were grown in open-type houses. The control house had open sides, while each treatment house had window coverings with either 42% or 89% light transmission properties. Birds from houses with window coverings deposited the same amount of pigment in the skin as did birds from the open house as indicated by blood xanthophyll level and excitation purity. Skin color scores, however, as well as dominant wavelengths and luminosities of shanks from these birds, indicated that pigmentation of birds grown in the house with 42% light transmission window coverings was significantly inferior to that observed for birds grown in either the open house or the house with 89% light transmission window covering. It was concluded that in situations where pigmentation is of concern, care should be taken in selecting window coverings which will not adversely affect pigmentation.

Influence of high temperature stress of 16-day embryos on subsequent hatchability.

Two experiments were conducted to determine the effect of acute heat stress on late-stage chicken embryos. Embryos were incubated at a normal control temperature (37.5 degrees C.) for 16 days and were then subjected to 40.6, 43.3, 46.1 or 48.9 degrees C. for various periods of time in another incubator of the same type. At the end of the stress period all embryos were placed back into the control incubator for the remainder of the incubation period. Exposure of embryos for 24 hours to a temperature of 40.6 degrees C, caused no major detrimental effects on hatchability. Exposure for 6 hours to the temperature of 43.3 degrees C, caused a decrease in hatchability with a severe decline in hatchability occurring after 9 hours of exposure. Exposure to 46.1 degrees C. for 3 hours or 48.9 degrees C for 1 hour killed all embryos. Chicks which hatched following a severe heat stress had a high incidence of clubbed, wiry down and exhibited an unsteady gait.

Status of the digestive system and tibiae of cropectomized hens at night.

Experiments were conducted to determine the effect of cropectomy on the total amount and calcium content of ingesta in the digestive tract of the laying hen at night, as well as to determine if any abnormal physiological changes had occurred in the cropectomized hens. Treatments were cropectomized, sham operated and unoperated control hens. The gizzards from cropectomized hens contained about twice as much feed at 7:30 p.m. as that of the controls. The gizzard weight, without contents, was also significantly heavier in cropectomized hens than that of the controls. At 7:30 p.m. total contents of the digestive system of cropectomized and control hens were 15.94 gm. versus 24.07 gm., respectively. The control birds also had 2.71 times more total calcium in the digestive system at 7:30 p.m. than the cropectomized birds. The contents of the small intestine of cropectomized birds had 17% more calcium at 7:30 p.m. than did that of the controls. However, by 5:30 a.m. the contents of the small intestine of the control birds had 3.17 times more calcium than did that of the cropectomized birds. No differences were found between treatments or between time periods in relation to tibia breaking strength, calcium content of tibia or percent tibia ash. The degree of dietary calcium deficiency at night appears to be greater with cropectomized hens, even though the gizzard compensates, in part, for the loss in storage capacity of the crop. It is hypothesized from these data that the crop is an important and necessary organ in the laying hen for supplying nutrients throughout the night when the hen is not consuming feed.

Characteristics of White Leghorn chickens selected for heat tolerance.

A series of studies was conducted to identify and delineate factors associated with responses of chickens to high ambient temperatures. Two populations of birds were used which had been selected divergently for tolerance to stress at 40.6 degrees C. and 75% R.H. and at 5 weeks of age. After four generations of selection for survival time the lines had separated by 28 minutes: 58 vs. 86 minutes for the low and high, respectively. Egg production, hatchability, Haugh units and specific gravity did not differ between lines. Egg weight was greater in the low line. The body temperature of chicks at 30 minutes of heat stress was correlated (r = -0.454; P less than 0.05) to survival time. Body weight was correlated (r = -0.325) with resistance to heat stress while loss of body weight during heat stress was correlated (r = +0.478) with resistance. There was no apparent difference between lines in respect to resistance of 16-day old embryos to heat stress.

The effect of cropectomy on selected reproductive and physiological characteristics of laying hens.

Two-hundred and fifty Babcock B-300 pullets (18 weeks of age) were either cropectomized, sham-operated or used as unoperated controls in two experiments. Although feed consumption was slightly less in cropectomized birds than in control birds, the pattern of feed consumption in relation to time of day remained unchanged. Egg production and body weight of cropectomized birds were significantly lower than that of control or sham birds. Egg weight was not affected by cropectomy or the sham operation. Cropectomy had no influence on the pattern of serum calcium or on egg specific gravity in relation to time of day; however, serum calcium and egg specific gravity was consistently lower at each time interval measured throughout the day or night when compared to that of controls. The adverse effect of cropectomy on specific gravity of eggs and serum calcium indicated that the crop is an important organ in the laying hen. The crop appeared to serve as a storage depot for feed providing the bird with nutrients necessary for optimal shell quality during periods on non-consumption.