The effect of restricting the individual daily energy intake of caged layers on the efficiency of egg production

Two experiments are described in which the daily metabolisable energy intake of laying hens fed a concentrated diet (ME = 3550 kcal/kg) was restricted on an individual hen basis. Performance on this diet was compared with that of hens fed a high‐energy diet (ME = 2690 kcal/kg). In experiment 1 medium‐weight hybrid pullets were used and in experiment 2 two light‐weight hybrid strains were used.

In both experiments maximum egg production was obtained from the birds fed the high‐energy diet ad libitum. Restriction of the concentrated diet caused a significant reduction of body weight gain and a statistically insignificant fall in the total weight of egg product and in percentage production in both experiments.

Restriction of the concentrated diet caused improvements of 22 and 18 per cent in the efficiency of utilisation of metabolisable energy in experiments 1 and 2 respectively.

The data are discussed in relation to the relevant literature and the current cost of concentrated sources of energy.     

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.     

Rapid determination of metabolisable energy of foods using cockerels

1. Adult cockerels were trained to consume their daily food allowance of about 100 g in 1 h. Excreta were collected for the next 24 h and the metabolisable energy (ME) content of the diet was determined.

2. Two different diets were used to study effects of ME on adaptation to diet. Repeatable estimates of ME were obtained without a period of adaptation.

3. No difference in ME was found when a test diet was fed to adult cockerels for 1 h, or fed continuously and excreta collected over 5 d. The conventional total collection method of determining ME using groups of growing chickens yielded similar results.

4. Excreta collected between 24 and 48, or 48 and 72 h post‐feeding yielded constant energy values following feeding of two different diets, indicating that all excreta from the 1‐h feeding were voided during the next 24 h.

5. The method is precise and results can be reported 36 h after receipt of food sample.     

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.     

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.     

The performance of male ducklings given starter diets with different concentrations of energy and protein

1. Male ducklings were fed for 14, 21 or 28 d on diets containing 180, 200, 220 or 240 g of protein and 10.88 or 12.55 MJ of metabolisable energy (ME) per kg, followed by a common finisher diet until 56 d of age.

2. Birds given starter diets with 220 or 240 g of protein per kg were significantly heavier at 14 d than those given diets with 180 or 200 g protein per kg.

3. There was no significant benefit in feeding diets with protein levels greater than 180 g/kg for more than 14 d.

4. Diets with only 10.88 MJ of ME per kg produced significantly lighter birds at 28 and 56 d of age and significantly reduced food conversion efficiency up to 14 d.     

Efficiency of utilisation by growing chickens of the energy of dietary fat and oil

1. Calorimetric studies were conducted with groups of five chickens to determine if availability of metabolisable energy (ME) changed with increasing concentrations of corn oil or tallow added to six diets.

2. There was no significant difference between the diets in the regression equations relating ME intake and energy retention. There was a slight increase in partial efficiency with increasing ME intake, from 82% at the mean daily intake of 1 874 kJkg W ^0.75 to 85% at the highest intake of 2 300 kJ/kg W^0.75.

3. Energy retention was greatest at the highest concentration of tallow (140 g/kg) in the diet; there was an indication that availability of ME may be greater for tallow than for oil at a similar ME inclusion rate when compared at the mean daily intake of ME. Without any lipid in the diet, partial efficiency was 77% and energy retention was lower than on the diets with added oil or fat.     

A comparison of the energy and nitrogen metabolism of fed ducklings and chickens

1. Energy measurements were made over 4 d on groups of three ducklings (aged from 5 to 22 d), and three broiler chickens (aged from 11 to 32 d) offered high‐ or low‐energy diets.

2. Food, metabolisable energy (ME) and water intakes were significantly higher for ducklings than for chickens. The ratio of water : food was 4.2 : 1 and 2.3 : 1 for ducklings and chickens, respectively. The food conversion ratio differed between diets but not species. Performance was generally better for both species on the high‐energy diet.

3. Heat production, energy, fat and protein retentions were higher for ducklings than chickens, and ducklings retained 0.44 of their energy as fat compared with 0.37 for chickens. Overall the ratio of protein (g) to fat (g) retention was 2.2 : 1 and 2.8 : 1 for ducklings and chickens respectively.

4. For ducklings, metabolisability of the high‐energy diet declined from 0.774 to 0.747, and to a lesser extent of the low‐energy diet, as they aged. There was no such decline for chickens. Net efficiency of utilisation of ME for gain was 0.64 for ducklings compared with 0.50 for chickens.

5. Fractional retention of dietary nitrogen (N) was 0.62 for ducklings and 0.55 for chickens. Gaseous ammonia‐N was 4.5 and 2.2%, respectively, of N retained.

6. In a second experiment groups of ducklings only, were offered high‐and low‐protein diets from 12 to 22 d of age. Comparisons among four diets showed that food and energy intake was lower on the low‐protein diet than on the other three. Energy retention on the high‐energy diet was greater (P<0.05) than on the other three diets.

7. It was concluded that a high‐energy diet is important for ducklings and chickens for maximum biological performance during the first 4 weeks of life.     

The nutritional value of low lathyrogenic Lathyrus (Lathyrus sativus) for growing chicks

1. The feeding value of new low β‐N‐oxalyl‐amino‐L‐alanine (BOAA) lines of Lathyrus sativus (lathyrus) and the benefits of dehulling the seed or of pre‐adapting chicks to lathyrus‐based diets were examined in several experiments.

2. Chicks fed on diets containing 400 g/kg of the low (1.3 g BOAA/kg seed) and medium (2.2 g BOAA/kg seed) BOAA lines did not differ (P>0.05) in weight gain (WG) or in apparent fat and protein digestibilities compared to birds fed on a wheat‐based diet.

3. Consumption of 600 g low BOAA lathyrus/kg diet caused a slight, but significant (P< 0.05), decrease in WG. Food efficiency decreased as the amount of dietary lathyrus was increased, suggesting that lathyrus may contain an antinutritive factor(s) other than BOAA.

4. Removal of the hull (70 g hull/kg seed) from the seed did not affect chick performance (P> 0.05).

5. Pre‐adapting chicks for 7 d to diets containing up to 600 g medium line lathyrus/kg diet did not reduce the detrimental effects of the lathyrus.

6. Although dehulling and pre‐adaptation of chicks to lathyrus were not beneficial, the low and medium lines of lathyrus tested show potential for use in chick diets up to at least 400 g lathyrus/kg diet.     

Metabolisable energy and digestible nutrient contents of brewers grains and glucose for the young Turkey

1. The metabolisable energy (ME) contents of dried brewers grains and of dried brewers grains with yeast were 5.51 +0.69 and 7.20 ±0.69 MJ/kg dry matter or 0.25 + 0.03 and 0.34 + 0.03 of their respective gross energy contents.

2. In these respective ingredients, the apparent digestibility coefficients of protein were, 0.66 + 0.08 and 0.69 + 0.08; of fat, 0.49 + 0.16 and 0.64 + 0.16; of dry matter 0.14 + 0.05 and 0.24 + 0.05, while fibre and nitrogen‐free extract (NFE) were not digested.

3. In balanced low‐protein diets formed by adding glucose to a high‐protein diet, the ME content of glucose was 15.12 + 0.44 MJ/kg dry matter or 0.97 ± 0.03 of its gross energy content, while the apparent digestibility coefficient of its NFE was 0–99 + 0–02, and that of its dry matter was 1.02 + 0.04.

4. Imbalancing diets greatly by removing or adding glucose to a balanced diet did not affect the nutrient digestibility or the ME of glucose, indicating that the basic assumption of linearity of these measurements with dietary content of the test ingredient was valid.     

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.     

Effects of lighting regimen and grower diet energy concentration on energy expenditure,fat deposition and body weight gain of laying hens

1. Mean metabolisable energy (ME) intakes and heat productions over a laying year were calculated for laying hens which had been submitted to one of various lighting regimens and given either a normal or a high energy ration during the rearing period.

2. Daily ME intake and heat production per hen in the laying period were unaffected by either lighting regimen or grower diet. ME intake per kg W ^0.75 and heat production per kg W ^0.75 during lay increased significantly with laying photoperiod, was non‐significantly higher following an 8‐h rather than an 11‐h rearing photoperiod, but was unaffected by dietary energy concentration. The increase in heat production (/kgW°‘⁷⁵) associated with a 1‐h increment in photoperiod was similar to predictions made from calorimetric measurements of diurnal variation.

3. Efficiency of conversion of food to egg was unaffected by either lighting regimen or dietary energy concentration.

4. Fat weight gain in lay was not influenced by lighting regimen, but was significantly lower in birds reared on the high, compared to the normal, energy grower ration. Fat‐free weight gain in lay was unaffected by grower diet, but was significantly increased by photoperiods longer than 8 h.

5. ME intake and heat production per kgW^⁰⁷⁵ were negatively correlated with age at first egg, but ME intake and heat production per bird d were not related to age at sexual maturity.     

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.     

Effect of environmental temperature,dietary energy,age and sex on broiler carcase portions and palatability

1. Two environmentally‐controlled houses, one at a constant 21°C (low temperature), the other diurnally cycling at 21 to 30°C (high temperature) and two diets of 13.0 MJ ME/kg (low energy, LE) and 13.8 MJ ME/kg (high energy, HE) were used to study the effects of age and sex on broiler carcase portions, dissected tissue proportions, and meat quality.

2. Slaughtering at 54 d instead of 34 d produced broilers with breast and leg weights of 277 and 308 instead of 284 and 319 g/kg carcase respectively, and a higher cutting loss (31 versus 6 g/kg carcass).

3. Males had lower proportions of breast, breast meat and fat, but higher proportions of leg, leg bone, and total meat to fat ratio than females.

4. Cycling high temperature resulted in higher breast, and lower leg proportions than constant low temperature.

5. High dietary energy content increased cutting loss, proportion of breast fat and lowered meat to fat ratio when compared to low energy, but did not affect the flavour of the meat, which was improved by age and high environmental temperature.     

The effects of dietary calcium concentration on pheasant breeder performance

1. Thirteen pens of breeding pheasants (Phasianus colchicus) were fed ad libitum on diets containing 20, 23 or 27 g calcium/kg.

2. All diets were formulated to contain 10.6 MJ ME/kg.

3. Three pens of birds receiving the diet containing 23 g calcium/kg were also offered grit free choice containing 280 g calcium/kg.

4. There were no effects of treatment on food consumption or reproductive performance.     

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.     

A comparison of the energy and nitrogen metabolism of broilers selected for increased growth rate,food consumption and conversion of food to gain

1. Calorimetric measurements were made on 5‐week‐old male chickens sampled from the third generation of three lines selected for either increased live‐weight gain (W), food consumption (F), or food conversion efficiency (E). A control line (C) was also measured.

2. Food intake and food conversion ratio were greater (P<0.05) in the F line than in the E and C lines.

3. Metabolisability of the diet was 0.8% higher in the E line than in the other lines.

4. Metabolisable energy (ME) intake and heat production were greater (P<0.05) in the F line than in the E and C lines, and energy balance was greater (P<0.05) in the F than in the W and E lines.

5. During starvation, excreta energy and heat production were greater (P < 0.05) in the F than the other lines.

6. Availability of ME (net energy) was the same (85%) for all lines but calculated daily maintenance energy requirements (kJ ME/kgW) were W, 860; F, 937; E, 796 and C, 810.

7. By 9 weeks the F line contained more fat and less water than lines E and C.     

Effect of different concentrations of metabolisable energy and protein on performance of White Leghorn layers in a tropical climate

1. An experiment was conducted to study the effects of feeding graded concentrations of metabolisable energy (ME) and crude protein (CP) on the performance of layers. Nine diets with three concentrations each of ME (10.04, 10.67 and 11.30 MJ/kg) and CP (150, 165 and 180 g/kg) in a 3 × 3 factorial arrangement of treatments were formulated.

2. A total of 5544 White Leghorn (WL) pullets (20 weeks of age) were housed in 4-bird colony cages and 22 adjacent cages constituted a replicate. Each diet was fed ad libitum to 7 replicates from 21 to 72 weeks of age. Production variables were recorded in 13 laying periods of 28 d each, and the data were pooled into three production phases, namely initial (21–32 weeks), peak (33–52 weeks) and post-peak (53–72 weeks).

3. No interaction was observed between ME and CP for egg production (EP), food intake (FI), food efficiency (FE), egg weight (EW), egg mass (EM) and body weight gain.

4. The EP, EW and EM during the initial phase of production were not affected by dietary ME concentrations, while the EW and EM improved with increasing concentrations of dietary CP from 150 to 165 g/kg.

5. During the peak production phase, improvements in EP (ME and CP), FI (ME), FE (ME, CP), EW (ME) and EM (ME, CP) were observed with increasing concentrations of energy and protein to 11.30 and 180 g/kg diet, respectively.

6. EP, EW and EM were unaffected by dietary variation in concentrations of ME and CP during post-peak production phase, but the FE improved and FI reduced with increasing dietary concentrations of these nutrients.

7. It is concluded that the optimum concentrations of ME for WL layers during the 21–32, 33–52 and 53–72 weeks of age are 11.30, 11.30 and 10.04 MJ/kg diet, respectively. The corresponding values for CP in diets are 180, 180 and 150 g/kg.     

Fat deposition and heat production as responses to surplus dietary energy in fowls given a wide range of metabolisable energy: Protein ratios

1. Female broiler fowl between 21 and 42 d of age were given diets with apparent metabolisable energy (AME) contents ranging from 8 to 15 MJ/kg at each of two crude protein (nitrogen x 6.25; CP) contents (130 and 210 g/kg).

2. Food intake was measured daily for 21 d. Body composition was determined at 42 d and gains in body mass, protein, fat and gross energy calculated by comparison with a group analysed at 21 d. Heat production was calculated by difference between AME intake and energy gain.

3. Decrease of food mass intake with increased dietary AME concentration limited the increase in AME intake to about 25%, despite the near 2‐fold range of AME concentrations.

4. There was no effect of CP concentration on food mass intake. CP intake was directly related to CP: AME ratio.

5. When body weight differences were taken into account, heat production was independent of dietary AME concentration, but increased by about 8% on the higher‐protein diets.

6. There were strong linear correlations between dietary CP:AME ratio and carcase protein: energy ratio, carcase fat content and carcase protein content.

7. It was concluded that the growing fowl responded to dietary nutrient: energy ratio, and the associated differences in nutrient and energy intakes, by varying the rate of energy deposition as fat, without regulatory variation of energy dissipation as heat.     

A marginal income and cost analysis of the effect of nutrient density on the performance of white leghorn hens in battery cages 1

In an experiment lasting 40 weeks with 576 caged White Leghorn (WL) hens and using linearly programmed least‐cost rations, the influence of increasing the nutrient density by increments of 100 kcal metabolisable energy (ME)/kg food, within the range 2500 to 3200 kcal ME/kg, on production was studied.

Increasing the nutrient density was accompanied by increases in egg weight, body weight and ME intake/hen d but mortality and the number of eggs laid were not affected (P<0.01). From a regression analysis carried out on the combined results of this and of another similar experiment, it was found that with each 100 kcal/kg rise in the ME content, the mean ME intake/hen d increased by 3.14 ± 0.59 kcal, the body weight by 38.85 ± 10.7 g and the egg weight by 0.21 ± 0.04 g.

A marginal income and cost analysis, using the above data, was carried out for three price situations of raw materials in 1970 and for two price situations of eggs and carcasses. The rations had a marginal cost structure for each nutrient density. From the analyses it appeared that the effect of the increases in egg and body weight in determining the most profitable nutrient density were at least as important from the economic point of view as the influence of the increased ME intake caused by increasing nutrient density. In the price situations considered, they neutralised the effect of one another, so that the diets with the lowest cost per calorie were also the most profitable.

For every price situation of raw materials, eggs and hens, the economical optimal food composition can be quickly and accurately determined by making use of the marginal profit analysis. It is also possible to couple the regression analysis for the adaptation of the mathematical functions to the parametric computer program which calculates the least‐cost rations.