Egg Mass Output Research Articles

Comparison of Energy Utilization Efficiency Among Six Lines of White Leghorns

Individual records were used of feed consumption, BW, BW change, and egg mass (EM) output during a 4-wk period for 180 hens from six different lines of White Leghorn chickens (30 hens per line). The diet contained 16.45% protein and 2,825 kcal ME/kg. Feed consumption was used to calculate actual ME intake (AcME) for each hen. Multiple regression of AcME was performed with metabolic BW, BW change, and EM production as independent variables. The regression coefficients and the independent variables were then used to calculate the expected ME intake (ExME).The following values were calculated for each hen and were used to compare energy efficiency among the six lines: the residual component of energy intake (RES), defined as the difference between the AcME intake and ExME intake; the relative efficiency ratio (RER), defined as (ExME+AcME) × 100 (calculated using the partial regression coefficients of the overall equation); and feed conversion, the ratio of feed consumed to EM. Significant differences among the lines in efficiency of EM produced were observed regardless of the efficiency measurement used. Feed consumption did not indicate differences in RES or RER.A multiple regression equation was derived for each line. Significant differences were found among the six lines in their energy requirements for maintenance and for egg production. These results suggest the possible use of the partial regression coefficients as selection criteria for separately improving maintenance efficiency and egg production efficiency.

Research Note: Adding Coefficients for Dietary Protein and Energy to Equations for Predicting the Metabolizable Energy Intake of Laying Hens

The data from two published experiments were used to determine whether feed consumption prediction equations could be improved by the addition of coefficients for levels of protein and energy in the diet. The two experiments were conducted from 20 to 44 wk of age with hens housed in cages. Diets contained primarily corn, dehulled soybean meal, wheat middlings, and poultry oil. When the standard form of feed consumption prediction equations was fitted to the data, only the coefficient for egg mass (b3) was different from zero (P<.10): MEI=b0+b1BWn+b2Δg+b3EM where MEI = metabolizable energy intake; BW = average body weight (kilograms), Δg = daily body weight change (grams); n = .65, .75, 1, or 2; and EM = daily egg mass output in grams.Three published equations that have been used to predict feed intake based on body weight and egg mass output were chosen for evaluation. For two equations the residual MEI (observed – predicted) was found to be predictable from protein or energy levels fed. Inserting dietary protein and dietary energy data for the feed decreased the observed error in equations to predict MEI, but the effect was small.

Self-select feeding of commercial pullets using a complete layer diet and a separate protein concentrate at cool and hot temperatures

Three experiments were conducted to examine the effects of self-select feeding to 40 weeks of age on food, protein and metabolizable energy (ME) intakes and egg mass output of pullets previously trained to this feeding system between 15 and 19 weeks of age and kept at cool (10�-20�C) and hot (25�-35�C) temperatures. In two experiments different lighting patterns were also compared without noticeable effect. Except for ME intake on the low-ME diet in Experiment 2, protein and ME intakes were significantly improved when pullets fed a low-ME (10.2 MJ/kg) or high-ME (12.0 MJ/kg) complete layer diet at both temperatures were offered a separate protein concentrate on a self-select basis. Increases in egg mass output were most pronounced when the high-ME complete diet was fed with the protein concentrate at the hot temperatures. The resulting egg mass output was similar to that obtained when the low-ME complete diet was fed with the protein concentrate or when a highly concentrated, complete diet, based on the intakes of the high-ME diet and the separate protein concentrate selected by pullets of similar age in an earlier study, was fed. Providing a separate granular source of calcium had no significant effect on the responses to self-select feeding.

Relationships between fear of humans, productivity and cage position of laying hens.

1. The productivity and behavioural responses of laying hens to humans were examined in relation to the effects of tier, row and position of the cage along the row over three consecutive 4-week periods. 2. Birds from the top tier had lower hen-day production, lower egg mass output and poorer efficiency of food utilisation than birds from the bottom tier in the third period. 3. Birds from the top tier showed greater avoidance of an approaching experimenter when in their cage or when on a table. 4. The production variables were significantly correlated with a number of behavioural responses to humans and a novel object, and with the corticosteroid response to handling/blood sampling. 5. The data suggest that birds from the top tier were more fearful of humans and that this higher level of fear may have been responsible for their lower productivity.

Responses of sexually-maturing pullets to self-selection feeding under different temperature and lighting regimens.

1. Pullets allowed to self-select nutrients from a protein concentrate and either a separate complete diet or cereal-based, energy-rich mixture showed preferences for protein and energy which varied in relation to the time of their onset of lay. 2. The selected protein:metabolisable energy (ME) intake ratio increased from 14 g protein per MJ of ME 2 to 3 weeks before sexual maturity to approximately 19 g protein per MJ of ME at and after sexual maturity. 3. This response to self-selection feeding was consistent with different temperatures, lighting patterns and dietary manipulations. 4. Egg mass output was improved by self-selection feeding at hot (25 degrees to 35 degrees C) temperatures in experiments 1 and 2 and at ambient temperatures in experiment 3. No beneficial response in egg mass from self-selection feeding was observed at cold (6 degrees to 16 degrees C) temperatures in experiment 1. 5. Providing 2 h of additional light during the dark (cool) part of the day, with or without 2 h of darkness in the middle of the extended light (hot) period, had no effect on the egg mass output of pullets at hot (25 degrees to 35 degrees C) temperatures.

Influence of dietary energy, nutrient density and environmental temperature on pullet performance in early lay.

1. Alterations in dietary metabolisable energy (ME) concentration had a limited influence on food and nutrient intakes and egg mass output of hens in early lay kept at the prevailing air (10 degrees to 24 degrees C), cold (6 degrees to 16 degrees C) or hot (25 degrees to 35 degrees C) temperatures. 2. Energy intakes were not improved by increasing the dietary concentrations of nutrients other than energy. 3. At prevailing air and cold temperatures all dietary ME-nutrient density combinations allowed hens to meet the recommended daily protein intake but only hens fed the most concentrated diets were able to meet this recommendation at hot temperatures. 4. Even the highest intakes of ME and protein achieved at hot temperatures failed to increase egg mass output to the values attained on any diet at cold temperatures.

Production responses of laying hens to 28 h bright:dim light cycles using different light intensity ratios and a 24 h temperature regimen.

Seven hundred and twenty laying hens housed in 8 environmentally-controlled rooms were changed from a 24 h light:dark cycle to a 28 h ahemeral bright:dim cycle. The ahemeral cycles consisted of periods of bright and dim light in ratios of intensity: 5:1, 10:1 and 30:1. The last regimen was applied either at a constant 21 degrees C or with a 24 h alternating temperature varying between 21 and 31 degrees C. Eggs were collected hourly from each bird for 5 d immediately before the introduction of ahemeral cycles and then over the same period 2 weeks after introduction. The interval between successive eggs within sequences lengthened with increasing bright:dim ratios. The increase in egg weight and decrease in deformation score were not significant. Total egg mass output was not altered. The cycling temperature regimen did not alter the entrainment of the birds, although intra-sequence interval decreased. The decrease in egg weight and increase in deformation score were not significant.

A Comparison of Glandless and Regular Cottonseed Meals for Laying Hens

A comparison of glandless cottonseed meal (GCSM) with a regular meal (RCSM) was carried out in a 336-day laying hen study using 5, 10, and 15% of each in the diet. Egg production (hen-day) rates obtained with these meals at dietary levels up to 10% were comparable to those of birds fed the soybean meal basal diet. The GCSM caused a decrease in production rate when fed at 15%. Egg mass output (grams egg/bird/day) was not adversely affected by any of the dietary treatments employed.Apparent lysine availabilities, evaluated with laying hens, were 62.1% for GCSM and 49.7% for RCSM, and true availabilities were 81.9 and 71.7%, respectively.Metabolizable energy contents of the two meals were similar with true metabolizable energy values of 3.04 and 2.81 kcal/g, apparent metabolizable energy values of 2.02 and 2.04 kcal/g and free gossypol levels of .012 and .039% GCSM and RCSM, respectively.No yolk discolorations were found in stored eggs from GCSM-fed birds. The 15% RCSM caused yolk discoloration in 72.5% of the stored eggs.The low residual oil in GCSM (.9% as compared to 1.7% for RCSM) was not sufficient to cause significant changes in yolk fatty acids. Total yolk saturated fatty acids increased from 38.43% for the basal diet to 47.49% with the inclusion of 15% RCSM.

The influence of body weight at point-of-lay on the production responses of restricted-reared pullets

The food intake, age at sexual maturity, egg weight and daily egg mass output of pullets fed on a time restriction basis during growth were significantly influenced by body weight at 21 weeks of age. Egg production was not affected significantly when 21-week body weight varied between 1.3 and 1.8 kg. It is suggested that one of the major factors influencing the performance of a pullet flock during lay is the number of birds of abnormally low body weight present at the end of the growing period.

Performance of layers reared and/or kept under different 6-hour light-dark cycles.

Using 60 hens reared and kept on a standard lighting programme (decreasing followed by increasing photoperiod to 22 weeks of age and 14 h continuous light: 10 h continuous dark during lay) as control, the effects of the following intermittent patterns on development and performance were studied. Group 1. The same rearing programme, followed by, between 20 and 36 weeks, 3 h light (L):3 h dark (D) intermittent and then from 36 weeks a regime in which each light period was progressively shortened by 30 min every 8 weeks with corresponding lengthening of the dark period so that the last cycle used between 52 and 60 weeks was 1.5 h L:4.5 h D. Group 2.6-hour light-dark cycles from hatching; the light:dark ratio first decreasing and then increasing, such that total light hours per day varied as in the control group to 20 weeks, and then subsequent lighting as in 1. Group 3. Intermittent lighting of 1.5 h L:4.5 h D unvaryingly from 4 to 60 weeks. Sexual development was essentially the same in all groups. Egg numbers were decreased slightly by the short light-dark cycles but daily egg mass output was the same in all groups. Food utilisation was best in group 1 and worst in the control group. In general egg weight and shell quality were improved by the short light-dark cycles; the effect appearing with the first eggs and being especially marked for group 3. On intermittent regimes ovipositions were equally distributed, between the four daily light-dark periods when the light:dark ratio was near unity but were more numerous during the first half of the solar day when the ratio was 1.5 L:4.5 D.

Use of Individual Feed Records in a Selection Program for Egg Production Efficiency: III. Relative Effectiveness of Two-Stage Selection

Two kinds of selection programs were compared. The first uses information on body weight (BW), egg mass output (EM), and individual bird feed consumption records (FC) to form a conventional single-stage selection index computed on all breeder candidates, T, in the flock from which S birds are selected as breeders. The second uses information only on BW and EM in Stage 1 from which t birds are chosen for testing in Stage 2 in which FC records are obtained. From these, the best S birds are chosen as breeders. The second program would be less costly because fewer birds, (T–t), are measured for individual FC records. Our results showed that when the net selection intensities in the two programs are equal with t/T = .5, the genetic gain in income over feed cost in the second would be about 3% less than in the first. Thus, there is a trade-off between the cost of testing and the expected genetic gains. The study was based on parameters estimated from two Leghorn populations for which individual feed records were taken.

Genetic parameters for egg weight v. age curve, and other egg production and egg weight traits, in synthetic lines of chickens

An exponential curve, W = P-Qexp(- Rt), where W is egg weight at age t, was fitted to egg weights of individual pullets, and genetic parameters were estimated for P, Q and R, the residual standard deviation and other egg weight and egg production characters. The data consisted of records collected over six generations on more than 4000 pullets in two selection lines and a control line which originated from a synthetic gene pool of White Leghorn x Australorp crosses. The half-sib and offspring-on-parent regression estimates of heritability pooled over the lines were 0.23 and 0.33 for P, 0.14 and 0.20 for Q, and 0.14 and 0.25 for R. Genetic correlations were estimated to be -0.10 between P and Q, -0.46 between P and R, and 0.90 between Q and R. These estimates suggest that the egg weight v. age curve may be modified to increase the proportion of eggs in desirable weight grades and reduce the incidence of oversized eggs later in the production year. The genetic correlation between mean weight of first 10 eggs and egg weight at 62 weeks of age was estimated to be 0.68, further suggesting that early egg weight may be improved partly independently of late egg weight. The heritability estimates of egg mass output were not higher than those of egg number in spite of the highly heritable average egg weight being an important component of egg mass, probably because of the negative genetic correlation (r = -0.49) between egg number and average egg weight. The standard deviation of individual pullet's egg weights was moderately heritable and genetically correlated positively with egg weight characters and negatively with egg production; these estimates were consistent with the responses to selection for reduced egg weight variability observed elsewhere

Significance of Body Weight as a Performance Parameter

The laying performance of different body weight classes, defined on both a genetic and phenotypic scale, were compared. The distribution of pedigreed Leghorn breeders of both sexes were truncated on the basis of 30 week body weight into two classes: light (L) or heavy (H). The progeny then were classified according to parental mating types as either L × L, L × H, or H × H. Differences among these progeny groups defined the genetic scale. The phenotypic scale was derived separately by phenotypic truncation of the progeny distribution into light (L), medium (M), and heavy (H) body weight classes at 30 weeks.Differences in rate of lay and in egg mass output between classes were in poor agreement with respect to the two scales. Light birds were poorest egg producers on the phenotypic scale but were the best egg producers on the genetic scale. Superior egg production by the heavy-bird class during the late spring and early summer months of the year could not be demonstrated. Deviations in body weight sharply reflected poorer performance on the phenotypic scale but not the genetic scale. This emphasizes the dominant role of management, feeding, and disease control over the genetic influence in maintaining optimum size for satisfactory productivity.

Comparison of the productive performances of the Sinai Bedouin fowl, the White Leghorn and their crossbreds: study under laboratory conditions.

1. A comparison of the productive performance of the Sinai Bedouin fowl (from the Sinai desert), the commercial White Leghorn and their reciprocal crossbreds was made uniform normal conditions. 2. The Sinai produced significantly fewer, smaller eggs, resulting in lower egg mass output (g/bird d), than the Leghorn and the crossbreds. 3. Egg weight of both crossbreds was intermediate between Sinai and Leghorn but laying rate was closer to that of the Leghorn. 4. Differences in egg mass output apparent at 8 to 10 months of age decreased considerably with age. 5. These findings suggest that selection or crossbreeding of the Sinai might improve productive performance while maintaining improved egg-shell quality.

Effects of food intake regulation on the energy metabolism of hens and cockerels of a layer strain

1. Indirect calorimetry was used to study the effects on the energy metabolism of cockerels and hens after peak lay of a hybrid layer strain of regulating food or energy intake to 80% of ad libitum for an extended period of time. 2. Regulation of food intake decreased fasting and fed heat productions per bird and per unit metabolic body weight (kg0.75). 3. Maintenance energy requirements (per kg0.75) of both sexes were reduced about 20% by regulation; maintenance requirements of cockerels were about 30% lower per kg0.75 than hens on the same treatments. 4. Reducing the intake of all nutrients by 20% had the same effect on the energy metabolism of cockerels as restricting energy alone by the same amount. 5. Gross efficiency of egg production, in terms of both mass and energy, was higher when intake was regulated. During weeks 21 to 52 of restriction, daily egg mass output was significantly higher in hens fed ad libitum. 6. After 52 weeks of food regulation, restricted hens weighed 20% less and their total carcass energy was 36% less than hens fed ad libitum; similar effects were found in the cockerels.

Hydrolysed feather protein as a source of amino acids for laying hens

1. The value of hydrolysed feather protein (HFM), included at 70 g/kg in a wheat‐based diet, as an amino acid source for laying hens was determined. 2. Egg production was reduced in hens fed on diets containing HFM owing to a deficiency in lysine, methionine and tryptophan. 3. Supplementation of the diet containing HFM with 3'0 g lysine (as L‐lysine HC1), 0.7g DL‐methionine and 0.5g L‐tryptophan per kilogram, resulted in a daily egg mass output similar to that achieved with a conventional layers’ diet.

Effects of nutrient concentration and dietary presentation on performance of dwarf hens

1. Diets containing 170 or 190 g protein/kg and 10.9 or 11.7 MJ ME/kg in all combinations were offered to dwarf hens in two dietary presentations: a complete mash or a form in which part of the protein and calcium contents were presented as soyabean meal pellets and limestone grit respectively. 2. Egg production and egg mass output were higher with the 190 g protein/kg diets. 3. Lower‐energy diets gave better egg production, while higher‐energy diets containing 190 g protein/kg improved food conversion efficiency. 4. Separation of protein and calcium constituents tended to give better egg production, food conversion efficiency, shell thickness and egg mass output.

Efficiency of selection in layer-type chickens by using supplementary information on feed consumption

Selection indexes to maximize net income for egg laying chickens were constructed with information on egg mass output, body weight and individual feed records. Relative selection efficiencies were then compared with different kinds of information in the index. If the genetic variation in feed consumption is completely determined by egg mass output (M) and body weight (W), using reliable estimates of genetic correlations or pehnotypic regressions of these traits with feed consumption in the index is equally efficient to an index with individual feed records. If real genetic differences in feed efficiency exist which are independent of egg mass and body weight, (h u (2) ), then there is greater justification in using individual feed consumption records. Forexample, if h u (2) =0.2, h W (2) =0.6, h M (2) =0.15 and rGWM (genetic correlation)=0.2, the use of individual feed records is expected to improve efficiency of the selection for net income by 9 p. On the other hand, if the genetic correlations of feed consumption on body weight and on egg mass are substituted in the index for records on individual feed consumption, only slightly less selection efficiency would result.

Value of Feed Consumption Records to Predict Net Income in Layer-Type Chickens

The importance of measuring feed consumption as a supplementary criterion of net performance was studied from two different sources of data: (1) random sample egg production tests conducted in the United States between 1949 and 1957 (USRST) and (2) a private test of experimental commercial strains conducted by the Goto Hatchery, Inc., Gifu City, Japan, between 1968 to 1971 (GOTO). Seven traits included in the study were net income (NI), egg rate (ER), egg weight (EW), body weight (BW), mortality (MORT), maturity (MAT) and feed consumption (FEED). Performance indexes were derived as multiple regression equations with NI dependent on the other traits. To test the value of feed consumption records, two performance indexes were compared in each data source. The first, I(6), contained all 6 independent variables, and the second, I(5), contained all variables except FEED.The correlations between NI and I(6) were 0.820 and 0.824 and between NI and I(5) were 0.818 and 0.822 in the USRST and GOTO data, respectively. The difference between the correlations with and without feed was nil in either data source. Thus, measuring FEED did not significantly improve the predictive value of a performance index when prior information was available on the other five variables.I(5) was also compared with an empirical performance index, I(E), defined as the ratio of egg mass output to the ¾ power of body weight. The latter simulates a feed efficiency index where egg mass output is an estimator of feed utilized for egg production and the ¾ power of body weight is an estimator of feed used in the maintenance of body tissues. The correlations between I(E) and net income were 0.68 ond 0.74 in the USRST and GOTO data, respectively, which were only slightly lower than the corresponding correlations between net income and I(5) when the latter was applied to the data source other than that from which it was derived. Thus, a rather simple empirical performance index of egg production efficiency, I(E), was almost as accurate in predicting net income as a multiple regression-derived performance index.

Performance of Dwarf Chickens Compared with Normal Small-Bodied Chickens

A large body line (B) and a small body line (C) of Leghorns were each crossed reciprocally with a homozygous dwarf line (D). Feed conversion and other performance traits of the pure lines and crosses were compared. The main question explored was how mini-type chickens, produced by conventional methods of selection compare with dwarf mini-chickens in efficiency of egg production. Two years of data showed that the dwarf gene reduced body size about 30% and egg weight about 8%; this is in agreement with reports of others. Age at maturity was delayed by about one week, and rate of egg production was depressed by about 5%.Comparisons of feed conversion, measured as the ratio of egg mass output to total feed consumed over a 15 week test period, demonstrated that the dwarf advantage in feed efficiency was a direct consequence of its reduced body size. When the dwarf cross (D♂ × B♀) was compared with a normal cross (C♂ × D♀), each having about the same body weight, no advantage could be demonstrated for the dwarf gene. For this comparison, the dwarf pullets were 13% heavier (1.7 kg. vs. 1.5 kg.), laid 11% fewer eggs (65% vs. 76%), and produced 12% less egg mass per unit of feed consumed than did normals. Feed conversion ratios of egg mass produced per g. of feed consumed were .38 g. for the dwarfs, and .43 g. for the normals. From this study we conclude that mini-chickens produced by conventional selection would be at least equal to and probably superior to the dwarf mini. However, this would probably require at least 7 generations of selection to be equivalent in size to a dwarf mini-pullet.