The hexosamine and uronic acid contents of the matrix of shells of eggs from pullets fed on diets of different manganese content

Three experiments are reported concerning the effect of the manganese content of the diet on the acid mucopolysaccharide content of egg shell matrix. In the first experiment hexosamine was taken as an index of acid mucopolysaccharide, but in experiments 2 and 3 uronic acid was determined instead.

It was found that a low‐Mn diet depressed the hexosamine and uronic acid content of the matrix of eggs sampled at the start of lay. However, eggs from low‐Mn fed pullets after three months of lay showed a significant increase in matrix uronic acid.

Other characteristics of shells from low‐Mn fed pullets taken at the start of lay were a low weight of shell per unit area and a high weight of matrix per unit area, which led to an abnormally high proportion of matrix to mineral in the shell.

As a model for normal shell development eggs were extracted from the uterus at an early and late stage of shell formation. Although these uterine shells resembled the poor shells from the low‐Mn diet from the point of view of poor shell thickness and low matrix uronic acid content, the proportion of matrix to mineral in shell was similar to that of the fully‐formed shells and not as high as in shells from low‐Mn fed birds. This last observation led to the conclusion that low‐Mn shells were not unfinished products arising from a premature expulsion from the oviduct.     

The influence on shell formation of the pre‐laying period for which a low‐manganese diet is given

The effect of a low‐Mn diet on egg shells was assessed by recording the number of soft shells laid at the beginning of lay, and the shell thickness of subsequent eggs. Observations were made on eggs from two batches of pullets: one that had been fed the low‐Mn diet from 1 month before egg laying began and the other from 2 months before onset of lay. The 2 month period gave fewer soft shells but thinner firm shells than the 1‐month period.

Similar observations were made with groups having mean pre‐laying periods on the low‐Mn diet of 46, 33, 21 and o d. There was a tendency for more soft shells and thinner shells to be produced the longer the period of low‐Mn feeding before laying began.

Pullets that had been in lay for 6 months or low‐ or high‐Mn diets were given an enforced rest period for 6 weeks. On recommencing to lay the low‐Mn birds produced a large number of soft shells and slightly thinner shells than similar birds that had been allowed to continue laying on the same diet.     

The effect of low‐protein grower diets on the subsequent response of pullets to quantitative food restriction during lay

1. The laying responses of pullets fed from 8 weeks of age on a 12.5% protein grower diet and subsequently subjected to food restriction commencing at various times between 20 and 40 weeks of age were compared with those of pullets reared on diets containing 12.5 or 16% protein and given access to food throughout lay.

2. Restricted feeding during lay of pullets reared on the low‐protein diet substantially improved laying performance, the best results being obtained from pullets fed the low‐protein grower diet and restricted from 20 weeks. The laying responses of pullets restricted after peak‐lay at 40 weeks of age were not significantly different from those of birds restricted prior to peak‐lay.

3. Maximal egg production of 81 % over the 48weeks of the experiment was attained on an average daily ME intake of 270 kcal (1130 kJ) and a FCR of 2.06 : 1.

4. It is suggested that food restriction of laying pullets previously reared on low‐protein diets may be successfully utilised prior to peak‐lay provided such restriction is not so severe as to retard the rate of attainment of mature weight and a continued slight gain in weight thereafter.     

Effect of diet and natural variations in climates on the performance of laying hens

1. Laying hens raised in 3 natural tropical environments were fed on 2 series of diets with a view to defining the optimum combination of climate and dietary energy.

2. A combination of 3 growing climates, 3 laying climates (temperate, hot dry, hot humid), and 2 dietary energy concentrations (10.03 and 11.70 MJ ME/kg with protein concentrations proportional to energy) were tested for 46 weeks using 432 point‐of‐lay pullets.

3. Both growing and laying climates significantly affected most traits measured during the laying period. The patterns of egg production showed good persistency in all environments and differences observed reduced with age.

4. The difference between the high and low energy intake reduced at high ambient temperatures. Feeding low energy diets did not affect mean age at first egg, rate of lay or the egg output in the hot dry environment, nor egg weight in either hot dry or hot humid climates. Rather, feeding low energy diets resulted in improved body weight change in all 3 laying environments.

5. The growing climate and diet interacted significandy on body weight change, while highly significant interactions between laying climate and diet occurred on rate of lay, food and energy intake and egg weight during the laying period.     

Selection for high and low percentages of chicken eggs with blood spots 1

Eggs were examined for presence of blood spots in a base generation of White Leghorns part of which were fed on an adequate diet and part on a diet inadequate in vitamin A that increased blood spot incidence. From theory and data, the selection differential was larger for low incidence selection for pullets on the inadequate diet than pullets on the adequate diet. Statistical and genetical models were given for estimating variances of this all‐or‐none trait with h ² = 0.16 and 0.60 for the lines on the adequate and inadequate diets respectively.

Predicted selection gains for individual selection of females alone were: adequate diet, low ‐0.91%, high 2.36%; inadequate diet, low ‐10.71%, high 14.58%. After eight generations of selection for high and low incidence on each of the diets there was a difference of 23.5% between high and low lines selected on the adequate diet and 37.7% on the inadequate diet. Evidence was inconclusive that selection for low incidence on the inadequate diet produced birds with a lower incidence on the adequate diet than birds selected on that diet.

Specific gravity showed a negative correlated selection response in both lines on the adequate diet but no correlated response was evident in the lines on the inadequate diet. There was a negative correlated response for Haugh units and a positive correlated response for blood spot size in all lines. Egg weight did not show a correlated selection response.     

Susceptibility of two commercial single comb white leghorn strains to calcium‐induced urolithiasis: Efficacy of dietary supplementation with dl‐methionine and ammonium sulphate

1. Susceptibility to calcium‐induced urolithiasis was assessed in pullets of two commercial SCWL strains (A and B) reared together from 5 to 18 weeks of age on diets containing 10 g/kg calcium (normal calcium: NC) or 35 g/kg calcium (high calcium: HC).

2. Kidney damage was not observed in pullets reared on NC diets. For pullets fed on HC diets, strain A developed significantly greater kidney asymmetry, a higher incidence of gross kidney damage and a higher incidence of uroliths than strain B.

3. Supplementing the HC diet with 6 g/kg DL‐methionine significantly reduced the incidence of calcium‐induced gross kidney damage and urolith formation in both strains. Ammonium sulphate (5.3 g/kg) was significantly more effective than dl‐methionine in reducing calcium‐induced kidney damage.

4. Neither dl‐methionine nor ammonium sulphate caused a measurable metabolic acidosis. Neither supplement consistently affected water consumption or manure moisture.     

Restricted feeding of broiler breeder pullets during the rearing period and its effect on productivity and breeding

A total of 2000 broiler breeder pullets was used for an experiment comparing two levels of restricted feeding from 6 to 20 weeks with three levels of low‐lysine feeding from o to 12 weeks of age. The object of the experiment was to obtain matching body weights at 20 weeks of age between the two levels of quantitative restriction and the highest and lowest levels of lysine feeding and to compare subsequent biological performance during lay. A control treatment was included in which birds were fed ad libitum at all stages.

Both methods of nutrient restriction reduced intake to 20 weeks of age. From 1 d to 60 weeks of age total food intake was reduced in proportion to the degree of restriction applied during the growing stage.

Sexual maturity was delayed by both methods of restriction, though low‐lysine diets produced a greater delay than quantitative restriction. Production of total eggs and of settable eggs was increased by both quantitative food restrictions and by the least severe of the lysine‐deficient diets. Following quantitative restriction egg size and fertility were both improved, but these advantages were not obtained by lysine restriction.

Mortality and culling were mainly influenced by a high incidence of “rupture of the gastrocnemius tendon “ which occurred exclusively in pullets fed lysine‐deficient diets during rearing.

It is concluded that quantitative restriction is to be preferred because of its advantageous effects on egg weight, rate of lay and fertility, and because it avoids the high mortality rate found with severe lysine restriction.     

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.     

The nutrient intake of laying hens given a choice of diets,in relation to their production requirements

1. Sixty individually‐caged birds, each of two stocks, were offered either a complete diet (11.2 MJ ME, 173 g crude protein and 32 g Ca per kilogram) or a choice between the same diet and ground barley. All diets were offered ad libitum from 41 to 56 weeks of age.

2. Weight gain, rate of lay, mean egg weight, egg output, shell thickness and total food intake were unaffected by the treatments in either stock.

3. The mean intake of the complete diet was 825 and 845 g/kg of total intake with standard deviations between individuals of 73 and 61 g/kg respectively in the two stocks.

4. In birds given a choice of diet the one selected was related to output (P < 0.01).     

Egg production of light and medium hybrids given diets varying in energy level during the chick,rearing and laying stages

A total of 1000 birds, one‐half of which were light and the other half medium hybrids, were given diets containing either high or low levels of metabolisable energy ad libitum during the chick (0.6 weeks), rearing (6–16 weeks), early laying (first 8 months) and late laying (last 4 months) stages.

The medium hybrids ate more and were heavier than the lighter hybrids at all stages. More eggs were laid by the light than by the medium hybrids but the latter laid larger eggs so that the total weight of eggs laid did not differ significantly between the two groups.

Medium hybrids given a low‐energy chick diet laid more eggs subsequently than those given a high‐energy chick diet, while the opposite result was obtained for the light hybrids.

Birds given a low‐energy rearing diet were lighter at 16 weeks and subsequently laid more eggs than birds reared on a high‐energy diet.

During the first part of the laying period consumption of the low‐energy diet was greater than that of the high‐energy diet, but the level and efficiency of egg production were the same for both dietary treatments. Mortality during lay was not significantly affected by dietary treatment or breed.     

Effect of light,vitamin d and dietary phosphorus on egg‐shell quality late in the pullet laying year

1. Eighteen diets supplying all combinations of three phosphorus contents (3.1, 4.0 and 4.8 g non‐phytate P/kg) and six vitamin D supplements (37.5 or 150 μg cholecalciferol/kg; or 16 or 24 μg 25‐hydroxy‐cholecalciferol/kg; or 37.5 μg cholecalciferol/kg with either 16 or 24 μg 25‐hydroxycholecalciferol/kg) were fed to 2 880 pullets of two stocks from 64 to 74 weeks of age. The birds were housed in eight light‐proof rooms, four of which had 24‐h light‐dark cycles (16L : 8D) and four had 28‐h cycles (20L : 8D).

2. The dietary treatments had no significant effect upon food intake, egg output, shell thickness, shell deformation or specific gravity of the eggs.

3. The 28‐h cycle reduced mean rate of lay by 4.5%, increased egg weight by 5.8% and increased shell thickness by 9.4%. The proportion of eggs with shell faults revealed on candling was reduced from 4.1 % to 2.8%.

4. It is concluded from this and other sources that decreasing dietary phosphorus or modifying vitamin D supplements may sometimes lead to increases in shell thickness of the order of 1 to 2%, but that these changes are unlikely to result in a measurable reduction in the proportion of cracked eggs late in the laying year.

5. A 28‐h light‐dark cycle results in a longer and more uniform interval between consecutive ovipositions and thus gives reliable increases in shell thickness which are large enough to reduce the proportion of cracked eggs in many practical situations. Whether it is profitable to use an ahemeral cycle will depend upon the relative prices paid for eggs of different sizes.     

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.     

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.     

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.     

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.     

Dietary selection of protein and energy by pullets and broilers

1. White Leghorn pullets and sexed broilers were allowed a free choice of two “ split‐diets “ which were concentrated sources of either crude protein (463 g/kg diet) or energy (13.32 to 14.00 MJ/kg diet).

2. Pullets receiving these two diets displayed a slower, but more uniform growth rate than did birds offered a single conventional diet. Up to 11 weeks of age, control birds consumed significantly more protein while the converse was true from 11 to 20 weeks. These differences are discussed in relation to the stage of sexual maturity.

3. Broilers offered the split‐diets grew more slowly and had an inferior food conversion ratio compared with control birds fed on a two‐stage rearing programme.

4. Among the broilers offered split‐diets, the usual sex differences were not observed for weight gain or carcass fat content.     

The influence of dietary manganese and stage of egg production on the hexosamine and hydroxyproline contents of parts of the oviduct

The total hexosamine, or glucosamine and galactosamine contents and hydroxy‐proline content of secretory tissue of the isthmus and uterus were determined.

A low‐Mn diet depressed the glucosamine content of isthmus and uterus but had no effect on galactosamine nor hydroxyproline.

The contents of hexosamine were similar after 3 months of egg production to those at the start of lay, and hexosamine and hydroxyproline values did not differ whether a non‐calcified egg was in the isthmus or one with an almost fully formed shell was in the uterus.

The glucosamine content of the isthmus was significantly greater than that of the uterus; the reverse was found for hydroxyproline and there was no difference between the galactosamine contents. In tissue from both regions the concentrations of glucosamine was several times greater than that of galactosamine.     

Voluntary food restriction by laying hens mediated through dietary self‐selection

1. Individually caged Single Comb White Leghorn hens simultaneously received two diets which allowed selection of certain nutrients: these “ split‐diets “, essentially provided concentrated sources of either protein and energy (191 g crude protein, 12.82 MJ ME and 4.7 g Ca/kg diet), or calcium (107 g CP, 7.28 MJ ME and 131 g Ca/kg).

2. During four, 28‐d periods of lay, birds offered these split‐diets consumed some 7% less food in total than did control birds receiving a conventional diet ad libitum.

3. Calculation of nutrient intakes showed that birds on the split‐diets consumed significantly less protein, energy and calcium than the control birds.

4. Giving split‐diets also resulted in superior shell quality; treatment differences were also noted in the timing of oviposition.

5. It is suggested that the voluntary reduction in food intake noted for birds offered split‐diets is associated with an appetite for calcium.     

Effects of battery gage shape and dietary energy regulation on the performance of laying hens offered diets containing dried poultry manure

1. About 3000 medium‐weight hybrid chicks were used in a factorial experiment involving two “chick” treatments: diets containing 0 and 50 g dried poultry manure (DPM)/kg; three “grower” treatments, diets with and without 50 g DPM/kg given ad libitum and regulated amounts of the diet with DPM; five “layer” treatments: diets with 0, 100 or 200 g DPM/kg given ad libitum and regulated amounts of diets containing 110 and 220 g DPM/kg and two shapes of layer cages: deep (conventional) and shallow.

2. Chick diets had no significant effects on rearing or subsequent laying performance.

3. Food‐regulated pullets were 7% lighter than pullets given the DPM diet ad libitum at 18 weeks but consumed 12.5% less food; growing treatments had no significant effect on subsequent egg production.

4. Hens housed in shallow cages laid 10.3 eggs/bird‐housed more than those in deep cages, produced 3.8% greater egg mass, consumed 2.7% less food and produced fewer damaged (cracked, broken and hair‐cracked) eggs (P< 0.001).

5. DPM‐containing layer diets had no adverse effects on egg production, or mortality; with 100 g DPM/kg efficiency of food conversion (EFC) was better than with 0 or 200 g/kg (P< 0.001).

6. Reduction of the energy intake of L110R and L220R hens with diets containing 110 and 220 g DPM/kg by 8.2 and 9.0% respectively, reduced the number of eggs laid/hen‐housed by 6 and 10.7 but improved the EFG (P< 0.001); there was no significant interaction between cage shape and energy regulation.     

The effects on rearing and subsequent laying performance of rearer diets containing two levels of protein and dried poultry manure or urea

1. Six hundred and seventy‐two light‐hybrid pullets aged 6 weeks were allocated to eight experimental treatments and cage‐reared to 18 weeks of age when they were transferred to single‐bird battery cages and fed on a common layer diet.

2. In the 6‐ to 12‐week period four dietary treatments were applied: a diet containing about 160 g crude protein (CP)/kg with or without 50 g dried poultry manure (DPM)/kg (diets 2 and 1 respectively) and a diet containing about 140 g CP/kg with or without 50 g DPM/kg (diets 4 and 3). In the 12‐ to 18‐week period two additional diets were fed: diets 1 and 3 supplemented with 10 g urea/kg (diets 5 and 6 respectively). Diets containing DPM were formulated to utilise the CP, energy, calcium and 50% of the phosphorus content of DPM.

3. Pullets fed on diets 1, 2 and 5 (high‐protein) were significantly heavier at 18 weeks than those fed on diets 3, 4 and 6 (low‐protein). In the laying period total estimated egg weight, food intake and conversion were significantly greater, and the age at first egg was significantly less (2.4 d).

4. Dietary DPM had no significant effect on the 18‐week body weight but food consumption was significantly less and conversion was significantly improved. There were no significant effects on subsequent laying performance. Dietary urea caused no significant effects on rearing or laying performance.