The effect of maize and maize oil on egg weight

In two short‐term experiments involving about 1500 laying pullets it was confirmed that the direct substitution of maize for wheat in a laying diet leads to a small but significant increase in egg weight.

It was further shown that when oat hulls were added to a diet containing 55 per cent maize to make it isocaloric with a diet containing 55 per cent wheat, there was still a significant improvement in egg weight with the maize diet. The addition of 2 ‐5 per cent and 5 per cent maize oil to a 55 per cent wheat diet resulted in increases in mean egg weight of 0.7 g. and 1.3 g. respectively. The same response to 2 .5 per cent maize oil was obtained when oat hulls were added to make the diet isocaloric with the basal diet.

It is concluded that maize has an effect on egg weight which is not attributable to the differences in dietary energy normally associated with the substitution of one cereal for another in practical diets. The effect is associated specifically with the oil content of the maize.     

Incorporation of triticale in layer diets

1. Diets containing either maize or triticale were fed unsupplemented or supplemented with meat meal or groundnut oil to White Leghorn pullets for two periods of 11 weeks each.

2. The egg production of birds fed on the unsupplemented triticale diet was significantly higher than that of the birds fed on the unsupplemented maize diet, but was not significantly different from that of the birds fed on the maize plus meat meal diet.

3. Protein quality of the unsupplemented triticale diet as judged by efficiency of nitrogen retention was similar or inferior to that of the unsupplemented maize diet.

4. The higher protein content of triticale and the increased intake of these diets seemed to be responsible for the better performance observed.

5. Addition of groundnut oil to the triticale diet did not improve either egg weight or production.

6. It is concluded that the quantitative substitution for triticale of maize does not adversely affect egg production and egg weight.     

Effect of dietary inclusion of ascorbic acid and palm oil on the performance of laying hens in a hot tropical environment

1. Two experiments were conducted to evaluate the effects of including ascorbic acid (AA), palm oil or a combination of both in the diets of laying hens during the hot months in a tropical environment.

2. The inclusion of AA improved egg production, food intake and efficiency of utilisation, and decreased the cost of food per kg egg. The addition of 400 mg AA/kg diet gave the most efficient performance.

3. Palm oil inclusion reduced the effect of heat stress and increased egg production, egg weight, food intake and efficiency of utilisation.

4. When 200 mg AA and 50 g palm oil/kg were used, additive responses were obtained with further improvements in egg production, food cost and efficiency.

5. Ascorbic acid and palm oil when fed alone or in combination reduced the incidence of cracked eggs.

6. Thus, 400 mg ascorbic acid/kg of diet, 50 g palm oil or 200 mg AA plus 50 g palm oil/kg diet ameliorated the effects of heat stress in laying hens.     

Efficiency of egg production of three types of caged layers fed diets containing maize, oats or barley as the main cereal ingredient

The results of two similar experiments, each using 204 pullets in cages, are presented. In each experiment, a type of light commercial hybrid, heavier commercial hybrids and Brown Leghorn×Light Sussex cross‐breds were compared, in factorial design, on diets containing either 65 per cent barley, 55 per cent maize or 35 per cent oats and 15 per cent bran. Individual records of egg production, egg weight, food conversion and body weight were kept for eight 28‐day periods, starting when the pullets were in full production.

There were no significant differences in egg production between diets but in both experiments a significantly improved food conversion ratio was obtained on the high maize diets, which also gave the highest level of energy consumption.

Most breed differences were not significant but in Experiment 1 the crossbreds produced significantly fewer eggs than the hybrids and in Experiment 2 the light hybrids gave a significantly better food conversion ratio than the two heavier types. The crossbred pullets consumed the most energy in both experiments and in Experiment 1 had significantly the worst energetic efficiency of egg production.

There were no significant interactions between type of pullet and type of diet in either experiment. Thus there were no indications that, at the energy levels investigated, favourable effects may be expected from the feeding of higher energy diets to the lighter hybrid type pullet.

The practical significance of feeding a high barley diet is discussed.     

Replacement of groundnut cake by dried poultry manure in the diets of laying hens

1. The effect on food consumption by pullets when dried poultry manure (DPM) replaced part of dietary groundnut cake depended on the strain of the birds: in two of the three hybrids food consumption was not affected when up to 100 g DPM/kg was fed.

2. Increases in food consumption were accompanied by increases in egg production.

3. The food required per dozen eggs was improved by up to 100 g dietary DPM/kg and variation in the sizes of eggs laid depended on the hybrid.

4. Concentrations of DPM up to 100 g/kg did not affect the water‐soluble nitrogen content of the egg but the crude albumen nitrogen content was depressed at concentrations of 80 g/kg or above.

5. Feeding DPM to laying pullets depressed body weight.     

The effects of early and late maturity on the protein requirements of pullets

Growing pullets were exposed to two light patterns which caused a difference in sexual maturity of 5 weeks. From 28 to 38 weeks of age they were fed diets containing crude protein levels of 7.0, 8.5, 10.0, 11.5, 13.0 and 14.5 per cent. Yellow maize provided 45 per cent and soyabean meal 55 per cent of the protein in all six diets.

Rate of lay, egg weight and body weight were greater in the late maturing flock than in the early flock at the start of the assay and throughout the assay period. The late maturing pullets required more protein to reach and maintain their maximum potential than the early birds, presumably because their potential output was greater. The late birds showed a diminishing but continued response to protein up to the highest level fed (14.5 per cent corresponding to 23 g. protein per bird day). The early maturing pullets showed no response to dietary protein levels beyond 11.5 per cent and their estimated protein requirement was about 16 g. per bird day.

When limiting amounts of protein were fed (7.0–10.0 per cent of the diet) the two flocks achieved similar levels of egg output. In both flocks and throughout the assay, body weight and egg weight fell at the two lowest levels and increased at the three highest levels of protein.

It is concluded that the protein requirements of early maturing and late maturing flocks of pullets may differ, but only in a way which corresponds directly with their different potential outputs. In the late flock, which had the higher protein requirement, excellent production was obtained with a diet containing 14½ per cent crude protein all of which came from vegetable sources.     

Calcium and phosphorus levels in the diet of laying birds

Two hatches of crossbred pullet chicks were brooded and reared to 18 weeks of age on diets which conformed to the recommendations of the National Research Council (N.R.C.) of America for calcium and phosphorus. The pullets of each hatch were then divided at random into six laying groups. Three groups were fed diets containing 2.25, 3.14 and 5.0 per cent respectively of calcium without supplementary phosphorus and the other three groups were fed diets of the same graded calcium levels but with supplementary phosphorus to give a total inorganic phosphorus content of 0.45 per cent. When the rate of egg production in the groups receiving 2.25 per cent calcium exceeded 70 per cent an ad libitum supply of limestone grit was provided and the intake recorded. Over the twelve months of lay this resulted in an average total dietary intake level of nearly 2.65 per cent calcium.

Egg yield was not significantly influenced by the diets, except that the production of birds fed on the diet containing 5 per cent calcium without supplementary phosphorus was significantly depressed. Food intake was not adversely affected by the higher levels of ground limestone; in fact, there was a positive regression of food consumption on the percentage of calcium in the diet. Because of the greater food intake and the lower egg production, food consumed per dozen eggs and cost of food per dozen eggs were higher in the groups receiving 5 per cent dietary calcium without phosphorus supplementation, compared with groups which received lower dietary levels of calcium. There were, however, no significant differences between the various groups in income or in the margin of income over costs, per bird or per dozen eggs.

The data on egg grading showed that over the two experiments and at all levels of calcium there was no evidence of any influence of phosphorus on the combined percentage of large and standard eggs. The average percentage for the two diets with the 5 per cent level of calcium was significantly greater than the combined average for all the other diets.

The average percentage of cracked eggs for the groups with diets containing 5 per cent calcium was 9.4 per cent compared with an average of 11.1 per cent for all the other diets, but the difference was not significant.

The results suggest that there is no economic advantage in raising the calcium content of the basal diet used in these experiments beyond the level of 3.14 per cent and that at this level there appears to be no need with this basal diet to supplement the phosphorus content.     

Studies on the effect of lysine and methionine supplementation of a high‐protein maize‐soyabean diet and of a low‐protein barley‐white fish meal diet on the performance of caged layers

Selected literature relating to the amino acid supplementation of layers’ diets is reviewed and the results of two experiments are presented.

In the first experiment a basal soyabean meal diet (14.3 per cent crude protein) was supplemented with L‐lysine and DL‐methionine, singly and together. Supplementation of the basal soyabean diet with the amino acids caused no significant effects on egg production, mean and total egg weight or food conversion efficiency. None of the soyabean diets proved as satisfactory for egg production or food conversion efficiency as a fish meal control diet (16.9 per cent crude protein).

In the second experiment the effect of adding 0.1 per cent each of L‐lysine and DL‐methionine or 0.2 per cent each of l‐lysine and DL‐methionine to a low fish meal diet (2.5 per cent fish meal) was examined. The addition of 0.2 per cent of each amino acid caused an increase in egg production.

Mean egg weight was improved by the addition of amino acids at both levels although this effect was not statistically significant. Comparison of the low fish meal diets with a fishmeal control diet (10 per cent fishmeal) showed that at the 0.2 per cent addition of amino acids, egg production, total egg weight and food conversion efficiency were better than on the 10 per cent fish meal control diet.

Two breeds, light and medium hybrids were used in both experiments.

The results are discussed with reference to their practical significance.     

Effect of feeding low lysine starters and developers on growth,sexual maturity and subsequent performance of broiler breeder pullets 1

Pullets that were fed diets containing 0.53 per cent and 0.42 per cent lysine grew at a slower rate and matured later than those that were given adequate amount of lysine. The latter pullets converted their food more efficiently than did the restricted pullets with the exception of the group fed the ration containing 0.53 per cent lysine for the first 12 weeks. The restricted pullets consumed less food during the growing period. A smaller bird was produced on less food. The restricted pullets were also lighter than the control pullets at the end of the laying season. A saving in food costs is indicated because the smaller hen would require less food for maintenance.

There was a higher mortality in the pullets fed a ration containing 0.53 per cent lysine during the growing period. The mortality in the group fed the ration containing 0.42 per cent lysine from 7 to 22 weeks of age was the same as that of the control. There were no differences in mortality during the laying season that could be related to methods of rearing the pullets.

During the laying season, the highest rate of lay was obtained from hens which had been fed the ration containing 0.42 per cent lysine from 7 to 22 weeks of age. Hens fed on the ration containing 0.53 per cent lysine from o to 4, 8 or 12 weeks of age showed no improvement in rate of lay as compared with controls.

Hens fed the ration containing 0.42 per cent lysine from 7 to 22 weeks laid fewer small eggs at the beginning of the laying season than did hens receiving adequate amounts of lysine throughout or fed the ration containing 0.53 per cent lysine from o to 4, 8 or 12 weeks. The hens fed the latter ration laid smaller eggs throughout the laying season.

No differences were found between the fertility, hatchability or embryonic mortality of eggs obtained from hens fed on lysine deficient diets during growth and those fed on diets adequate in lysine.     

Effects of linseed oil and palm oil on growth performance,tibia fatty acid and biomarkers of bone metabolism in broilers

1. This study was conducted to determine the effects of different dietary fat sources on growth performance, tibia fatty acids and biomarkers of bone metabolism in broilers.

2. One-d-old commercial Arbor Acres broilers were fed with a maize–soya bean basal diet for 42 d, supplemented with oils according to the following 5 treatments: lard (lard group); linseed oil (linseed oil group); palm oil (palm oil group); linseed oil + palm oil (60:40 or 40:60 w/w, LP-1 group and LP-2 group, respectively).

3. No significant differences in weight gain, feed intake and gain/feed ratio were observed between the lard and linseed oil groups. Birds fed on palm oil had significantly greater weight gain and feed intake than those fed on lard or linseed oil. Growth performance in LP-1 and LP-2 was significantly greater than that of single-oil groups.

4. Tibia growth and bone characteristics were not influenced by supplementation with lard, linseed oil, or palm oil alone, but broilers fed on a mixture of fats had significantly greater tibia weight and length compared to broilers fed on linseed oil. Bone mineral density in tibia was significantly increased in LP-1 and LP-2 groups.

5. Supplementation of linseed oil alone or in combination with palm oil enhanced apparent digestibility of calcium, reduced serum calcium and increased tibia calcium concentrations. Moreover, supplementation with linseed oil alone or in combination with palm oil had a positive effect on biomarkers of bone growth.

6. The combination of linseed and palm oils was beneficial for growth performance, tibia growth and biomarkers of bone metabolism.     

Comparison of nutritive values of groundnut oil cake and Niger oil cake for laying pullets

1. The nutritive value of Niger oil cake (Guizotia abyssinica, Cass.) as a protein supplement for layers’ diets has been assessed.

2. Replacing groundnut oil cake (GNC) by Niger oil cake (NC) on an isonitrogenous basis, did not affect egg production, egg weight or the amount of food required per dozen eggs.

3. The percentage retention of nitrogen from diets containing 30% GNC or 30% NC was similar.

4. The ME value of NC used was 3025 kcal/kg.

5. It is concluded that NC can replace GNC in layers’ diets.     

Some effects of changing protein levels during the pullet laying year

Three diets containing 12, 14 and 16 per cent crude protein were fed to laying pullets from 23 to 63 weeks of age. The laying year was divided into three periods of 10, 15 and 15 weeks to examine the effect of feeding these diets at different stages of lay. Eighteen treatments were used, representing all possible combinations of three diets in the first period, three diets in the second period and two diets (16 and 12 per cent) in the third period. Two groups of 75 pullets were allocated to each treatment.

In each period the diet had a significant effect on the rate of lay, egg output (g./day) showed a linear regression on protein intake. There was no indication that the amount of protein needed to maximise egg output was any less in one period than another, although the level of maximum output varied substantially as the year progressed.

Where the feeding of an inadequate level of protein in one period was followed by a higher level in the next, liveweight showed a marked recovery but there was little evidence of compensatory egg production. When the protein of the diet was reduced from 16 to 12 per cent, rate of lay fell sharply to a level below that of birds which had received the 12 per cent protein diet throughout.     

Effect of low-energy cereals and cereal by-products and of a vegetable fat supplement on egg production and food conversion in caged layers

The aim of this work was to ascertain the value of alterations in the energy concentration in layers' diets by the incorporation of high‐energy cereals and fat in diets composed of ingredients commonly used in the United Kingdom. Two similar experiments, employing 22 individually‐fed Light Sussex pullets on each diet, were carried out using cereal and cereal by‐products in four diets containing 1200, 1050, 1000 and 880 k cal. M.E./lb. Significant improvements in food conversion efficiency were found when low energy cereals were replaced by maize. Furthermore, the diet of lowest energy content led to a considerable reduction in the total energy intake of the pullets accompanied by a fall in production. There is evidence that the efficiency of utilisation of M.E. for egg production is not affected by the dietary level of M.E. over the range of energy concentration studied in these experiments.

In two further experiments four groups of 48 Brown Leghorn x Light Sussex pullets were fed diets containing three levels of vegetable fat as groundnut oil to give dietary concentrations of 1170, 1240, 1270 and 1340 k cal. M.E./lb.

The results show that fat addition had no significant effect on egg production or egg size.     

Effect of constant and of changing photoperiods on age at first egg and related traits in pullets

1. The effects of constant photoperiods and of single (5 h) changes in photoperiod applied at 12 or 17 weeks of age upon age at first egg (AFE) were studied using ISA Brown and Shaver 288 pullets.

2. Birds reared from 2 d of age until after maturity on constant 10 h photoperiods matured 8 d earlier than birds reared on constant 8 h and 5 d earlier than the average for 13 or 18 h photoperiods.

3. A single increment in photoperiod from 8 to 13 h advanced AFE by 23 d (compared to 8 h constant day controls) when applied at 84 d, but by only 6 d when given at 119 d. An increase in photoperiod from 13 to 18 h advanced AFE by only 4 d, averaged across breeds and age at increase. A reduction in photoperiod from 13 to 8 h delayed AFE by 22 d when given at 84 d and by 16 d at 119 d. A similar 5 h reduction in photoperiod, but from 18 to 13 h, retarded maturity by 11 d in ISA Brown pullets, but only when given at 84 d, and delayed AFE in Shaver 288 by 12 d, but only when given at 119 d. This interaction may be partly explained by the different physiological stages reached by the two breeds when the photoperiod was changed.

4. Under constant daylengths cumulative food intake before first egg was positively correlated with photoperiod, but the early AFE for birds on 10 h photoperiods resulted in this group having the lowest cumulative food intake to first egg.

5. A 5 h increase in photoperiod at 84 d significantly reduced the food consumed to first egg, but had no effect when given at 119 d. A 5 h decrease in photoperiod generally increased the food consumed to first egg, but the effect was only significant when the daylength was reduced from 13 to 8 h at 119 d. Food intake to first egg in birds subjected to a change in photoperiod was highly correlated with AFE.

6. The data confirm that sexual development in growing pullets responds more to changes in photoperiod than to the absolute daylength, that changes made at different daylengths are not equivalent and that sensitivity changes with age.     

Effects of age on the tryptophan requirement of laying hens

1. White Leghorn pullets which had been used for an assay of tryptophan requirement between 32 and 40 weeks of age were used for similar determinations between 63 and 73 and, after a moult, from 97 to 106 weeks of age.

2. A tryptophan‐limiting protein mixture was used and by dilution seven dietary protein contents were produced, supplying from 0.84 to 1–92 g tryptophan/kg diet. The diet of lowest protein content was also sup‐lemented with free tryptophan. These diets were fed in experiments using 24 groups of 72 pullets at 63 to 73 weeks and 45 groups of 21 hens at 97 to 106 weeks.

3. The relationship between egg output and tryptophan intake was the same in moulted hens as in young pullets, but pullets of 63 to 73 weeks of age yielded a different response curve; more tryptophan being needed for a given egg output.

4. It is concluded that tryptophan required, per day, does not decrease during the first laying year, despite a decrease in rate of egg output.     

A study of the effect of variation in the calorie‐protein ratio of a medium energy diet and a high energy diet containing sucrose on the efficiency of egg production in caged layers

Literature pertaining to the variation in the protein content of layers’ diets is discussed and the lack of information on the effect of calorie‐protein ratio on food conversion is mentioned. The experiment described in the present paper was designed to test the effect of variations in calorie‐protein ratio on food conversion on a diet of high energy content (1340 k cal/lb.) based on sucrose supplementation and on a medium energy diet (1160 k cal/lb.). At the same time three types of pullet, Thornber 606, Thornber 404 and Light Sussex x Brown Leghorn pullets were compared on the two types of diet, each being fed at three nominal protein levels of 13, 15 and 17 per cent giving a total of eighteen treatments. The pullets were individually recorded for egg production, egg weight and food consumption. Meta‐bolisable energy crude protein determinations were carried out on each of the six diets employed and the actual calorie‐protein ratios calculated.

There was no significant effect on egg production when the calorie‐protein ratio of the diet was raised from 69 (i.e. k cal M.E./lb. per 1 per cent protein) to 90 but an increase to 103 reduced production and egg weight. It was found that maximum efficiency of food conversion was realised at ratios of 76 to 78.

The efficiency of conversion of dietary energy was unaffected by energy concentration in the diet.

The lightweight hybrid (Thornber 606) produced eggs more efficiently than either the Thornber 404 or the crossbred type.     

Studies on egg shell strength,shell stiffness,shell quantity,egg size and shape

Physical properties which included shell stiffness, egg weight, width and length, shell weight and thickness, percentage shell, shell weight per unit area, shape index and roundness were studied in relation to maximum force and energy absorbed at failure in 2733 eggs produced by sixty SCWL pullets. Pooled‐egg, bird‐average and individual‐bird bases were used for correlation and regression analyses.

All physical properties in combination accounted for 61.9 and 88.2 per cent of the variation in force and 19.6 and 59.5 per cent of energy absorbed at failure in pooled‐egg and bird‐average analyses respectively. The non‐destructive measurements of shell stiffness, egg size and shape gave R ² values of 60.5 and 86.9 per cent with force and 16.2 and 55.0 per cent with energy in corresponding analyses.

Shell stiffness proved to be the most important predictor of force at failure. Analyses in which variation of shell stiffness was explained by other physical properties supported the conclusion based on theories of elasticity applied to shell structures that shell stiffness was largely an indirect measurement of egg shell quantity together with lesser effects of egg size and shape.

Bird‐to‐bird variation in relations between physical properties and shell strength was evident from individual bird analyses. Coefficients of determination from force at failure regressed on shell stiffness had a mean value of 0.455 with a standard deviation of 0.178 (n = 60).     

The protein requirements of two strains of laying pullets

Diets with 16.5, 14.5, 12.5 and 10.5 per cent protein and 2765 k cal. metabolisable energy per kg. and a fifth diet containing 10.5 per cent protein and 2165 k cal. M.E./kg. were fed to Rhode Island Red x Light Sussex pullets and to “hybrid” pullets which weighed 33 per cent less and produced 20 per cent more eggs. Both strains had protein requirements of the order of 20 g./bird/day. It is possible that the assumed higher requirement of the “hybrid” pullets for productive purposes was offset by a smaller requirement for maintenance and growth. Expressed as a percentage of a 2765 k cal. diet, the small strain required at least 16.5 per cent protein and the large strain no more than 12.5 per cent protein for maximum performance. Both strains performed well on the 2165 k cal., 10.5 per cent protein diet, illustrating that high energy diets are not essential for small strains of pullets.

Egg size was reduced by protein restriction in the heavy strain but not in the light strain. On isocaloric diets the light strain consumed more food only at the lowest protein level whereas the heavy strain tended to eat progressively more as the protein was reduced from 16.5 to 12.5 per cent. When offered the low energy diet both strains ate more food, but substantially fewer calories, than when given diets of 2765 k cal. M.E./kg. Protein restriction had a marked effect in reducing live‐weight gains. Energy level of the diet had a large effect on weight gain and also on fat deposition in the carcass.

The greatest differences in performance due to diet did not occur at the time of maximum egg output. The evidence indicates that a diet which is too low in protein to support peak egg production will also fail to support normal egg production at any later stage of the laying year.     

The effects of crude and refined low erucic acid rapeseed oils in diets for laying hens

1. The effects of feeding diets containing 15% crude or refined low erucic acid Span rapeseed oils, refined regular rapeseed oil or lard to pullets on productive performance and the lipids of egg yolk were determined.

2. Productive performance was best with the low‐fat control diet, less good with the crude low erucic acid Span oil or lard‐containing diets, intermediate with the diet containing refined Span oil and worst with the diet containing regular rapeseed oil.

3. The various dietary treatments did not affect total lipid content of egg yolk but did affect the fatty acid composition of egg yolk lipids.

4. No substantial amounts of erucic acid were found in the eggs indicating that the hen is able to control the lipid concentration in egg yolk though control of the fatty acid composition of lipids is poorer.     

Asociation of plasma 5'‐nucleotidase and alkaline phosphatase with production traits in chickens: Effects of age and housing systems

1. The housing system, age of pullets and their interaction had a significant effect on plasma 5'‐nucleotidase and alkaline phosphatase activities.

2. Activities were higher in birds in cages than in those on the floor, reflecting perhaps the stress of caging. Activities increased with age.

3. Activities were higher in pullets selected for higher production.

4. The type of housing had no effect on egg production, but age at first egg, egg weight and 40‐week body weight were found to be affected significantly.