Energy requirements of laying hens in a semi‐arid continental climate 1

A total of 1260 Single Comb White Leghorn layers were used in three experiments, each of 12 months duration. The experimental site was inland, at an elevation of 995 m above sea level and received a mean annual rainfall of 450 mm. The metabolisable energy (ME) contents of the diets used ranged from 2582 to 2918 kcal/kg, lower energies being achieved by the substitution of barley for maize and higher energies by the use of beef tallow.

Differences in dietary energy caused significant differences in egg production and weight in two of the experiments. Increasing ME of the diet caused significant decreases in food intake in two experiments and significant improvements in the efficiency of food conversion in all experiments. Dietary energy was found to affect body weight gains significantly in only one experiment. Energy intake during the summer was 10 to 15% lower than during the winter or spring.

It is concluded from this study that hens of the strain used, laying at a rate of 70 to 75% and weighing about 1·65 kg in a semi‐arid continental climate, require approximately 300 kcal (1·25 MJ) per bird‐days. This requirement varies with the season, being approximately 20 kcal (84 kJ) higher during the winter and 20 kcal lower during the summer.     

A calorimetric estimate of the efficiency of utilisation of dietary energy by the growing cockerel

The metabolic rates of four growing cockerels, aged between 10 and 18 weeks, were measured using respiration calorimetry. Measurements were made when the birds had been fasted for 48–72 h and when they had been given a cereal‐type diet at maintenance and production levels.

The mean fasting heat production (±SE) was 92.3 (±5.0) kcal/kg d or 113.4 (±5.7) kcal/kg3/4 d. The relationship between energy balance (T) and ME intake (X) was calculated to be Y = 0.851X—92.9 indicating that the maintenance ME requirement was 109.1 kcal/kg d and that the net availability of the ME was 85.1 per cent. The efficiency of energy utilisation in relation to plane of nutrition and to the amount of protein and fat deposited is discussed.     

True metabolisable energy values of some feedingstuffs

1. The apparent metabolisable energy (AME) and the true metabolisable energy (TME) contents of some feedingstuffs were determined with cockerels. The test materials consisted of feed‐grade lentil, lentil bran and wild vetch seed.

2. The average values of nitrogen lost, endogenous energy losses (EEL) and endogenous energy losses corrected to zero‐nitrogen balance (EEL_n) were found to be 1.18 g, 62.13 kJ and 21.51 kJ/bird/48h, respectively, from adult cockerels given an energy supply as 50 g glucose during starvation.

3. The nitrogen‐corrected apparent metabolisable energy (AMEn) values for feed‐grade lentil, lentil bran and wild vetch seed, respectively, were 6.84, 3.05 and 14.31 kJ/g dry matter. The nitrogen‐corrected true metabolisable energy (TME_n) values for the respective feedingstuffs were 7.44, 3.65 and 14.90 kJ/g dry matter.     

Studies on the incorporation of triticale in diets for growing chicks

1. The classical ME value of triticale varied from 12.305 to 13.778 kJ/g or 11.819 to 13.016 kJ/g corrected for N‐retention depending upon method of calculation.

2. Substituting triticale for maize, weight for weight, but not on a iso‐nitrogenous basis, in a groundnut oil cake (GNC) starter diet improved weight gain (P < 0.05) when the substitution exceeded 75% without affecting the protein efficiency ratio (PER).

3. A similar substitution in a soybean oil meal diet, improved weight gain (P < 0.05) at 50% or more but PER declined (P < 0.05).

4. The net protein utilisation and protein retention efficiency values of the diets in which maize protein was replaced by triticale protein were significantly reduced.

5. The maize‐GNC diet was equally limiting in methionine and lysine while the triticale‐GNC diet was not.

6. The growth and food efficiency obtained with a triticale‐GNC diet was higher (P < 0.01) than with the maize‐GNC diet but not with a maize‐GNC supplemented with fish meal and methionine.

7. It is concluded that triticale could quantitatively substitute maize in the starter diets.     

Response of broiler chicks to threonine‐supplemented diets to 4 weeks of age

1. Two experiments were carried out to determine the response of broiler chicks to threonine‐supplemented diets between 10 and 28 d and 7 and 21 d of age, respectively.

2. In the first experiment female broiler chicks were fed on 11 experimental diets. Two iso‐energetic basal diets (diets 1 and 2) were prepared with 200 and 160 g CP/kg and 7·6 and 6·0 g threonine/kg respectively. Both diets contained 11·5 g lysine and 8·7 g sulphur‐containing amino acids/kg. Diet 3 was composed of diet 2, supplemented with all essential and non‐essential amino acids (EAA and NEAA, respectively) except threonine, to the concentrations of the amino acids in diet 1. The NEAA were added as a combination of glutamic acid and glycine. Diets 4 to 11 had the same compositions as diet 3, but contained increasing amounts of threonine.

3. For birds fed on diet 2, gain was significantly lower and food/gain ratio was significantly higher than for birds fed on diet 1. Supplementation with EAA, NEAA and threonine to the same concentrations in diet 1 resulted in a performance similar to that found on diet 1.

4. In experiment 2, male and female broiler chicks both received 10 experimental diets. Diet 1 contained 220 g CP/kg and 8.5 g threonine/kg, diet 2 contained 160 g CP/kg from natural raw materials and 6 g threonine/kg. Both diets contained 12·4 g lysine and 9·3 g sulphur‐containing amino acids/kg. Basal diet 2 was supplemented with all EAA and NEAA to the concentrations of basal diet 1, except for threonine. Diets 3 to 10 had the same compositions as the supplemented diet 2, but contained increasing amounts of threonine.

5. For male and female chicks on diet 2, gain was significantly lower and food/gain ratio significantly higher than those on diet 1. Diet 10 (160 g CP/kg plus all EAA, including threonine, and NEAA supplemented to the concentrations of diet 1) resulted in the same performance as diet 1.

6. The results indicate that, when low protein maize‐soyabean meal diets supplemented with EAA and NEAA with 13·31 MJ ME/kg were fed to male and female broiler chicks until 21 d of age, improvements in gain and food/gain ratio were obtained when the dietary threonine content was increased to 7·25 g/kg. When female chicks were fed threonine‐supplemented diets to 28 d of age, improvement in gain and food/gain ratio was obtained when the threonine concentrations were increased to 6·32 g/kg diet.

7. Curves have been fitted to the data, from which a cost‐benefit analyses can be made and an optimum threonine dose calculated, using local prices.     

Energy and nitrogen metabolism of broilers selected over ten generations for increased growth rate,food consumption and conversion of food to gain

1. Energy and nitrogen (N) metabolism were studied in 6‐week‐old male birds taken from 4 lines of chickens selected for 10 generations for increased weight gain (line W), increased food consumption (line F), increased conversion of food to gain (line E) or at random (controls, line C).

2. Calorimetric measurements were made 8 times on each line while fed ad libitum in large open‐circuit respiration chambers for 3 d, and 11 to 13 times without food in smaller closed‐circuit respiration chambers for 24 h.

3. The F line ate 60% more food, produced 90% more excreta and 34% more heat and retained 80% more energy and 35% more N in their bodies than lines E and C. Line W was intermediate.

4. When differences in body weight were taken into account, the E and W lines had lower heat production than the C line, while the F line ate 40% more food, produced 30% more heat and retained 70% more energy and 30% more N than the E line.

5. In lines W, F, E and C respectively, the mean metabolisability of dietary energy (%) was 69·4, 62·9, 70·1 and 67·8 ; the fasting heat production (mean ± SE) was 481 ±9, 569 ± 10, 485 ± 9, and 508 ± 9 kJ/kgW d; the net availability of metabolisable energy (NAME) was 0·68 ± 0·05, 0·76 ± 0·04, 0·85 ± 0·06 and 0·73 ± 0·04; the estimated daily maintenance energy requirements were 671 + 15, 866 ± 14, 701 ± 13, and 742 ± 11 kJ ME/ kgW; and the proportion of N retained per unit increase in N intake was 0·38 ± 0·08, 0·50 ± 0·06, 0·56 ± 0·10 and 0·53 ± 0·06. 6. The contribution of line differences in the above traits to large line differences in efficiency of food utilisation is discussed.

     

Metabolisable energy determinations using chicks and turkeys

Experimental mashes containing different proportions of maize, wheat, barley and oats were fed to young broiler chickens and turkeys. Metabolisable energy (ME) determinations were carried out from 5 to 7 and from 19 to 21 d of age.

The turkeys obtained 3.2 and 1.7% more metabolisable energy than chicks from the diets used when assessed on a classical ME and N‐corrected ME basis respectively. The difference was smaller when maize formed a major part of the diet than for the other cereals. Higher ME values were also obtained in the older birds but the effect was not reproducible.     

Effects of force‐feeding and dietary cereals on gastrointestinal size,intestinal absorptive ability and endogenous nitrogen in ducks

1. Gastrointestinal size, intestinal absorption of glucose and L‐methionine, and intestinal endogenous nitrogen in Pekin ducks were measured after the birds were subjected to force‐feeding with excessive amounts of a diet based on maize or barley for 12 d.

2. Force‐feeding significantly increased the weight and area of the crop, the weight of the proventriculus, the length and area of the jejunum and ileum, but decreased the weight of the gizzard and the thickness of its caudodorsal thick muscle. Feeding a barley‐based diet also decreased the thickness of caudodorsal thick muscle of gizzard.

3. Force‐feeding enhanced the absorption rates (μmol/cm²) of glucose and L‐methionine in both jejunum and ileum. Ducks fed on a maize‐based diet showed a slightly higher absorption rate of glucose compared to those fed on a barley‐based diet.

4. Force‐feeding caused a significant increase of endogenous non‐protein nitrogen (μg/cm²/h) in both jejunum and ileum and a slight increase of endogenous protein nitrogen in the jejunum.     

Decreasing egg weight by energy or protein restriction and energy required for repletion 1

1. A diet containing 110 g crude protein/kg caused smaller losses in egg weight, numbers and body weight in Babcock B300 layers than diets containing 90 g protein/kg, 6.56 MJ ME/kg or 7.90 MJ/kg.

2. The sequence of repletion of depleted birds was body weight, egg weight and egg number. For the first alone more than 420 kJ/d was required, for body weight and egg weight more than 630 kJ/d and for all three more than 1170 kJ/d.     

Effects of restricting the amounts of medium or low‐energy diets fed to laying hens in different colony sizes

1. Light hybrid hens between 32 and 68 weeks of age kept 4, 5 or 8 birds to the cage received one of three energy intakes, from a medium‐ or low‐energy diet.

2. Ad libitum fed birds laid more and heavier eggs than any of those restricted. A decrease in daily egg output of about 5 g was associated with each 100 kJ decrease in daily intake of metabolisable energy.

3. For the same energy intake, egg output of birds fed on the low‐energy diet was markedly greater than that associated with the medium‐energy diet.

4. The mortality of birds receiving restricted quantities of the medium‐energy diet was two to three times greater than that associated with similar rationing of the low‐energy diet.     

Effect of genetic line, sex of birds and the type of bioassay on the metabolisable energy value of maize

1. Experiments were conducted to determine the differences in the energy utilisation of adult hens and cockerels of a layer (Rhode Island Red) and a broiler line (Cornish). The effect of 2 different precision-feeding methodologies (wet and dry-feeding) were also compared. Birds were fasted for 24 h, precision fed with 35 g dry or 33.5 g wet corn and fasted for a further 48 h period. Excreta were collected during this period. 2. Non of the parameters (method, sex, line) had a significant effect on the ME content of maize. However, a significant interaction was found between the sex of the birds and the methodology used. Females of both genetic lines utilised the energy content of maize more efficiently than males. The opposite was found when the wet precision-feeding method was used. 3. Weight loss and endogenous energy excretions (EEL) of birds were also effected by sex and genotype. Cockerels of both lines had significantly greater EEL than females. However, since hens lost less nitrogen, the nitrogen corrected EEL (EELn) was higher for the hens.     

The response of male broiler chickens to diets with various protein contents during the grower and finisher phases

1. In two trials, each using 960 male broilers from 21 to 42 d of age increasing dietary protein from 175 to 220 g/kg at equal ME increased body‐weight gain from 986 to 1090 g and gain:food ratio from 0·439 to 0·499, while abdominal fat pad weights (40·7 to 35·2 g) and total carcass fat content (140 to 118 g/kg) decreased.

2. From 42 to 49 d gain: food ratio increased with increasing protein content, while body‐weight gain and abdominal fat were not affected.

3. Broilers fed on the lower‐protein diet from 21 to 42 d showed compensatory growth during the finisher phase (371 versus 331 g gained) and utilised food more efficiently (0·383 versus 0·340 g gained/g food consumed).

4. Decisions regarding nutrient concentrations during grower and finisher phases should take into account compensatory growth and food utilisation as well as body‐weight gain, food consumption and carcass composition.

     

Effects of environmental temperature,dietary energy,sex and age on nitrogen and energy retention in the edible carcase of broilers

1. Two environmentally‐controlled houses, one set at constant 21°C (low temperature, LT) and the other set at diurnally cycling 21°C to 30°C (high temperature, HT), and two dietary energy concentrations of 13 MJ ME/kg (low energy, LE) and 13.8 MJ ME/kg (high energy, HE) were used to study nitrogen and energy retention in the edible carcase of male and female broilers slaughtered at 34 and 54 days.

2. Carcase nitrogen was higher in males than in females, and in birds reared at LT than in those reared at HT.

3. Birds at LT and on HE diet, regardless of sex, retained more energy as fat in their carcases than those at HT and on LE diet respectively.

4. Maintenance energy requirement averaged 6.70, 7.67, 7.43 and 9.01 kJ per g metabolic body size (kJ/gW 0.66) for broilers at HT and LT up to 34 d and at HT and LT up to 54 d, respectively.

5. There was a similar increase with age in the energy requirement for growth but with requirements of broilers at LT consistently lower than for those at HT.     

A study of digestibility and biological value of protein in diets fed to colostomised laying pullets to determine their protein requirement

Hybrid pullets were colostomised just after the commencement of laying. A nitrogen‐free diet was used to determine metabolic faecal nitrogen (MFN) and endogenous urinary nitrogen (EUN). The mean figure obtained for MFN/kg. wt./100 g. dry matter/day was 67.2 mg. and for EUN/kg. body weight 3/4/day was 83.3 mg.

High energy diets of about 1350 k cal./lb. containing 13, 15 and 17 per cent protein and medium energy diets of 13 and 17 per cent protein were fed to colostomised pullets to determine their digestibility, biological value and net protein value. In a further experiment a maize‐fishmeal diet of 1370 k cal. ME/lb. and 17 per cent protein, a soyabean‐maize diet of 1330 k cal. ME/lb. and 14 per cent protein and the latter diet supplemented with methionine and/or lysine were also examined. The mean BV and NPV values of the diets considered in Experiment 1 were 60 and 52 respectively.

Addition of methionine to the maize‐soyabean diet increased the BV from 43.9 to 61.6, the addition of lysine to 43.0 and the addition of both to 67.1.

A factorial method of calculating the daily protein requirement of the pullet based on the data for MFN and EUN and the NPV of each diet is presented. The estimate of 13.3 g. protein per day for the hybrid pullet is compared with other estimates in the literature.     

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.     

Influence of energy intake on growth and utilisation of dietary protein and energy in germ-free and conventional chicks

The effect of metabolisable energy (ME) intake on the growth and utilisation of dietary protein and energy in germ-free (GF) and conventional (CV) chicks was investigated in two experiments. In experiment 1 a high energy diet (HED, 14.8 kJ ME/g) and a marginally-adequate energy diet (AED, 11.7 kJ ME/g) were fed to the GF and CV chicks at 240 g/2 birds/10 d. In experiment 2 a diet with 13.7 kJ ME/g was fed at 118 g (low level, LL) or 128 g (high level, HL)/bird/10 d. Body weight gain, protein retention and protein retention rate were similar in GF and CV chicks on both AED and HED in the first experiment, but in the second were higher in GF than in CV chicks. The increased ME intake of the CV chicks in experiment 2 may be too small to compensate for the increased requirement. ME intake was significantly higher in the CV chicks than in the GF chicks, whereas energy retention was similar in both groups.     

Estimation of endogenous energy and nitrogen losses in the cockerel during fasting and postprandial

1. The endogenous energy (EEL) and nitrogen losses of adult cockerels were studied during both when the animals were starved and when they were fed on a highly digestible nitrogen-free diet. The birds were fed three intakes by intubation and the effects of these intakes were compared. 2. During the 48-h study, the excretion of energy (EEL) was found to be 49.4 kJ, when the birds were given food. When starved this estimate was considerably higher, 70.3 kJ. 3. When endogenous energy per 48 h was corrected to zero nitrogen balance (EEL0), the value of starved animals of 30.1 kJ was still considerably higher than the 13.4 kJ for fed birds. 4. It was concluded that feeding a nitrogen free, highly digestible diet reduces the excretion of endogenous energy. Thus determinations from starved birds appear to give biased estimates of EEL and EEL0. Hence, true metabolisable energy values would also be overestimated where endogenous energy values from starved birds were used.     

Effects of temperature treatments on the energy and nitrogen metabolism of fed chickens

1. Calorimetric measurements were made for 5 d on individual broiler chickens (1 kg) fed ad libitum and acclimated or unacclimated to six temperatures from 2 to 35 °C (constant), or alternated between these temperatures and 22 °G (alternated). For the four treatments, heat production was related to temperatures and the resultant curves were significantly different.

2. Food intake, heat production and maintenance energy requirement all increased linearly with decreasing temperature. Metabolisability of the diet was only 13.8 kJ/g at 35 °C, compared with a mean value for all treatments of 14.1 kJ/g.

3. Energy retention and nitrogen (N) retention (g/d, or % dietary N) were maximal at 22 and 16 °C, however the amount of energy deposited as protein remained relatively constant below 30 °C.

4. Net availability of metabolisable energy was calculated in two ways: by calculating the increase in heat production of fed birds above their starvation values giving a mean value of 0.82; this was similar to the mean regression coefficient which included starvation data, and related ME intake and energy retention; but without these data availabilities ranged from 0.45 at 35 °C to 1.0 in the cold.

5. Acclimation or alternating of temperature had very few significant effects, however there were temperature x acclimation effects on N retention and heat production. Similarly alternating temperature significantly increased food intake and heat production at high temperatures, but decreased metabolisability of the diet to 13.7 kJ/g at 35 °C from an overall mean of 14.1 kJ/g.     

No effect of short‐term exposure to high‐fibre diets on the gastrointestinal morphology of layer hens (Gallus gallus domesticus): body reserves are used to manage energy deficits in favour of phenotypic plasticity

Summary Using layer hens, Gallus gallus domesticus, we compared the digestive capabilities of birds on a low‐fibre diet (LF, 8.49% neutral detergent fibre; NDF), with those fed a high‐fibre diet balanced for energy and protein to match the LF diet (high fibre balanced, HFB; NDF = 15.61%) and those fed a high fibre unbalanced (HFU) diet (NDF = 16.68%). The HFU diet had the lowest apparent dry matter (DM) metabolisability at 58.14 ± 6.46%, followed by HFB, 65.87 ± 3.50 and the LF diet, 70.49 ± 7.07%. Despite significant differences between apparent DM metabolisabilities of LF and HFU diets, no morphometric changes in the gastrointestinal tract (GIT) of layer hens were observed (including crop, gizzard, proventriculus, liver, large intestine, paired caeca and small intestine). Conversely, body mass losses were recorded for animals on HFU diet, while those on the LF and HFB diets actually gained body mass over the 14‐day trials. We suggest that the body mass losses seen in the animals fed HFU diets were attributed to losses in adipose tissue, but this was not quantified. Assuming body mass losses were mainly in adipose tissue, we propose that adipose may act to buffer environmental challenges like shortfalls in nutrient acquisition when dietary energy requirements are not met. Compared with smaller birds (e.g. quail), the larger body size of the layer hens may offer them a greater safety margin in terms of body energy reserves before changes in the GIT might be needed to redress energy deficits associated with hard‐to‐digest, high‐fibre diets.     

Influence of level of feed input and procedure on metabolisable energy and endogenous energy loss (EEL) with adult cockerels

1. Two experiments were performed to study the relationship between apparent metabolisable energy (AME) and true metabolisable energy (TME) values at different feed intakes. Rhode Island Red (RIR) adult cockerels were used in two bioassays, under standard conditions. 2. In the first experiment (precision feeding) the birds were not fed for 24 h and then various quantities of maize were fed. There were 6 replicates per treatment. Droppings voided during the 48 h of the experimental period were collected and assayed for gross energy and nitrogen. 3. In the second experiment, each bird was given a 3-d adaptation period, fasted for 24 h and then given maize as an admixture (conventional addition method: CAM) to the same rations as those used in the first experiment. During the 3 d of the experimental period, droppings were collected and frozen for chemical analysis. 4. The results showed that mean metabolisable energy (ME) values obtained by the precisionfeeding procedure were higher than those obtained by CAM. The endogenous energy loss (EEL) (FE m + UE e ) determined by precision feeding was lower than that given by CAM. 5. It was concluded that the method of feeding does not influence ME of maize at different feed inputs. However, differences among intercepts of the regression between ME and feed input suggest that EEL varies at different maize inputs. 6. The optimum maize quantity was approximately 35 to 40 g for adult RIR cockerels by both procedures.