ENERGY LEVELS AND FEED PRESENTATION FOR LAYING HENS: EFFECTS ON PERFORMANCE AND INTAKE By Philippe Joly Introduction It is generally acknowledged that a laying hen adapts its intake relatively well to the energy value of its feed. This regulation is however far from perfect. The hen is influenced by the form in which the feed is presented, notably by particle size or granulation. Energy regulation is modified by the presence of fat in the feed, which modify its form and palatability. Inversely, the cellulose content of the feed can be a limiting factor for intake when cellulose content is high, but it seems to play an important role in the behaviour of hens, notably feather pecking, and by its effect on the digestive tract and the digestibility of the feed. Moreover, the genotypes currently used have evolved considerably over the past 40 years. It seems necessary to look once more at energy regulation. The aim of this summary is to give an overview of experiments carried out over recent years. Good knowledge of the factors regulating energy intake is essential for realising genetic potential and lowering production costs.

1. Effect of feed dilution on performance 1.1. Materials and methods In order to make a distinction between the effect of diluting feed and the effects of adding oil, we have taken up those experiments carried out over recent years where the fat content was comparable. Diets where the increase in energy level resulted from an increase in fat content are studied further below. We have taken up experiments carried out by Walker (1991), Peguri (1991), ISA, Joly (1997), Grobas (1999), Balnave (2000), Leeson (2001), Harms (2000) and van der Lee (2001). The principal characteristics of the diets are given in table 1. The majority of these experiments were carried out with ISA brown hens. For each experiment, a regression method was used to determine the effect of a 100 kcal energy level change on variations in energy consumption, laying rate and egg weight. Walker (1991) used diets where the energy level varied between 2560 and 2799 kcal, without added fat, and between 2775 and 2990 kcal with a level of 3% added fat. Peguri (1991) compared 4 energy levels at different temperatures; the feeds were diluted with sand and cellulose. The results obtained between 16°C and 27°C were used for this study. In the experiment carried out by ISA, 3 energy levels were used: 2208, 2460 and 2712 kcal. The 2208 kcal diet contained 9% bran and 22% sunflower meal. The 2460 kcal diet was a mixture of the 2712 and 2208 kcal diets. The 2798 kcal diet was diluted with sand to give a level of 2519 kcal in the Harms experiment. Balnave (2000) used rice husk to make up 8.3% of the 2535 kcal diet. In an early experiment, Leeson (2001) diluted the diets with a 50/50 mix of sand and cellulose (alphafloc).

1.2. Results Energy consumption seems largely influenced by the type of diet and dilution methods used. For this reason, the principal characteristics of the feeds are shown in table 1. The zoo technical results are shown in table 2 of the appendix. Variations in performance observed for a 100 kcal change in energy level are given in table 3. Variations have been expressed as percentages. Energy consumption: Between 2200 and 3000 kcal, an average drop in energy consumption of 1.2% is seen when the energy level decreases by 100 kcal, with a variance of 0 to 3%. These results agree with those obtained by Morris in a 1968 overview.

Energy levels and feed presentation for laying hens

2009-10 Page | 1

The experiments showing the greatest reduction in consumption seem to be those where pure cellulose was used to dilute the feed, either through the addition of pure cellulose, sunflower meal or rice husk, which led to a great reduction in intake. In fact, the addition of cellulose contributes to a reduction in feed density and therefore to a considerable increase in the volume which has to be ingested. The greatest reductions in energy intake were obtained by Balnave (2000), with a reduction of 2.96% for 100 kcal, due in all likelihood to his use of 8.3% rice husk in his 2535 kcal diet. In the experiment carried out by ISA, (Joly, 1997) the cellulose content of the feeds was 4%, 5.9% and 7.8%. The 2200 kcal diet contained 22% sunflower cake and 8.9% bran. As for Leeson (2001), dilution was carried out with a mixture of pure cellulose and sand, with incorporation levels of 2.5%, 5% and 7.5% pure cellulose (alphafloc). The Peguri (1991) 2702 kcal diet also contained 2.9% pure cellulose. These results show that feed density plays an important part in energy regulation. Inversely, dilution with sand has much less effect. This was only 0.8% in the trial carried out by Harms, where all dilution was by means of sand. Walker (1991) observed no variation in energy intake between 2560 and 2800 kcal because none of his diets contained added fat. The same is true of diets with 3% added fat where the energy level ranged from 2775 to 2990 kcal. Table n°3: Effect of feed dilution on variations in intake, rates of lay and weight of eggs, expressed as a % for an increase of 100 kcal in feed energy level. Authors Walker 0 % (1991) Walker 3 % (1991) Peguri (1991) a ISA –Joly (1996) Grobas (1999) Balnave (2000) a Harms (2000) Leeson (2001) a Van Der Lee (2001) Average

Variation as a percentage per 100 kcal Intake Rate of lay Egg weight +0.17 +0.30 -0.06 +0.68 +2.75 +0.30 +0.83 +1.98 +0.27 +0.64 -0.24 +0.09 -0.47 +2.96 +0.55 +0.24 +0.82 +0.08 -0.37 +1.41 -0.36 +0.71 +0.82 -0.73 +0.68 +1.18 +0.03 +0.36

Energy levels used (kcal) 2560-2679-2727-2799 2775-2822-2895-2990 2702-2812-2912 2208-2460-2712 2680-2810 2535-2725 2519-2798 2465-2610-2755-2900 2644-2763

Reduction in energy intake levels varies by 0% to 3% per 100 kcal and depends upon the raw materials used, the average working out at 1.2%. This largely depends upon the way in which dilution has been carried out. The amount of the energy intake seems to depend upon the feed density. This observation was already made by Gleaves (1965) who concluded that the quantity of the energy intake was in relation to the feed density. Performances: Number of eggs: This is largely unaffected by the feed energy level and in all cases, the difference being less than 1%. With a variation of the energy level from 2560 to 2800 kcal, Walker (1991) observed no difference in production. In the ISA experiments (Joly, 1997) no significant differences were seen. The observed reductions in performance were only 0.2% with the 2460 kcal diet and 1.3% with the 2208 kcal diet. The lay was only reduced by 1% with the 2535 kcal diet in Balnave’s experiments (2000). The 2465 kcal diet diluted with the sand/cellulose mixture gave better performance (+2.7%) than that of the 2755 kcal diet in the experiment carried out by Leeson (2001). Egg weight: Egg weight reduces in line with the reduction of the feed energy level. The reduction can be estimated at about 0.4% for an energy level variation of 100 kcal. This represents only about 0.2 grams. This reduction in egg weight can be explained by a reduction in energy intake and a reduction in the weight of the hen when diluted diets are used. The mass of egg produced would reduce by about 0.36% for a reduction of 100 kcal in the feed energy value.

Energy levels and feed presentation for laying hens

2009-10 Page | 2

Energy efficiency: The energy efficiency, expressed in kcal per gram of egg production, shows constant improvement with dilution of the feed. The gain is about 0.8% per 100 kcal. This efficiency gain can be attributed in part to a reduction in body weight, to an improvement in plumage and perhaps (Hetland 2003) to improved digestibility of the feed. In the ISA experiments carried out in 1996, we noted that the hens on the 2208 kcal diet had plumage which was generally in better condition than did those on the other diets at the age of 52 weeks. Van der Lee (2001) observed an improvement in plumage where a diluted diet was used. Castaing et al (1995), using diets at 2 energy levels, 2740 and 2900 kcal with either 0, 1 and 2% animal fat or 3, 4 and 5% maize oil did not observe any difference in productivity nor in the consumption index expressed in kcal per gram of egg production. This was due to the fact that the hens were rationed to maintain energy intake at identical levels. The improvement in the index is therefore the result of the effect that the energy level can have on feed consumption. Table n°4: Effect of energy level on body weight Peguri, 1991 Weight at 36 Energy, kcal wks. 3010 1582 2928 1574 2812 1530 2702 1518

Joly, 1997

Balnave, 2000

Energy, kcal

Weight gain

Energy, kcal

Weight

2712 2460 2208

225 179 87

2920 2727 2535

2226 2189 2142

Effect on digestibility: Soluble non-starch polysaccharides have been the subject of much research in recent years. The insoluble fraction used to be considered as performing an exclusively dilutionary role. Recently, some work has been dedicated to them. In addition to their effect on energy consumption and consumption time, it was shown by Hetland et al (2003) that the insoluble fibres improved the digestibility of the starch by increasing the gastro-intestinal reflux of bile salts, with both crushed and whole wheat, and increased retention times in the gizzard (Hetland and Choct, 2003). Gizzard size was very significantly improved by the distribution of 20g of wood shavings from 15 to 25 weeks and 30g thereafter. Measurements were carried out at 29 weeks. The same results were obtained for broiler chickens with shavings or oat hull. Effect on liveability: Dilution of the feed obliges hens to increase the volume and quantity of feed intake and so to increase feed consumption times (Vilarino, 1995). This leads to an improvement in plumage (Van der Lee 2001) and a reduction in actual feather pecking. This could explain the reduction in mortality observed in certain trials using diluted diets. In Hartini's view (2003), the reduction in pecking and of mortality could be linked to the non-starch polysaccharide content. The author has noted an increase in feed consumption time and a reduction in pecking (cf table n°6 and 10). This aspect will be mentioned again in examining the impact of the form in which the feed is presented on liveability and plumage. Another trial confirms the importance of consumption time. The trial was carried out on ground pens with a litter of wood shavings (Steenfelt et al, 2001) and using undebeaked hens. It consisted of comparing the performance and behaviour of hens receiving a commercial feed, with or without access to maize silage, pea-barley silage or carrots. At 54 weeks, the mortality was 15.3% for the control group and 1.5%, 2.5% and 0.5% respectively for the other diets.

Energy levels and feed presentation for laying hens

2009-10 Page | 3

Table n°5 Effect of feed energy dilution on mortality Balnave (2000) Mortality, % Energy, kcal 2920 7.29 b 2727 4.69 ab 2535 1.04 a

ISA - Joly (1997) Energy, kcal Mortality, % 2712 4.7 2460 5.7 2203 3.7

Hetland and Choct (2003) consider that there is a specific need for insoluble fibre. The opportunity to consume insoluble fibre afforded to hens raised on litter explains why the weight of their gizzard is higher than in hens housed in cages. According to them, the presence of feathers in the gizzard would depend on the nature of the feed. These authors assume that feather pecking is connected to a need for fibre, since in their experiments, the hens were housed in individual cages. Table n°6: Effect of fibre type on the mortality of hens of which half un- debeaked Mortality in % 17-20 wks. 21 to 24 wks. 13.2b 28.9b 3.9a 14.3a 5.8a 15.9a 4.1a 17.8a

Type of diet Standard feed (corn) Insoluble fibre (mill run) Soluble fibre (barley) Soluble fibre (barley) + enzyme

Effect on consumption at onset of laying: 3 trials mention changes in consumption at the onset of laying (cf. table n°7). In each of the 3 trials, the reduction in intake is greatest over the course of the 4 weeks following the change of feed. In the Peguri and Balnave trials, the reduction in intake was greater than the rate of reduction in the feed energy level. Table n°7 : Changes in energy consumption at start of production according to feed energy level Energy Level ( kcal ) 19-23 wks 23-27 wks 27-31 wks 31-35 wks 35-39 wks

2712 100 100 100 100 100

Joly (1997) 2460 96.7 98.2 97.8 96.2 97.5

2208 86.9 89.8 90.9 90.5 90.3

Peguri (1991) 2755 2645 100 94.6 100 97.1 100 96.1 100 96.9

Energy levels and feed presentation for laying hens

Period 19-35 wks 35-63 wks 63-83 wks

Balnave (2000) 2727 2536 100 92.4 100 94.9 100 94.4

2009-10 Page | 4

The limitation of the energy intake is due to the decrease in feed density. Balnave (2001) notes that the respective volume of feed intake for each diet was 219 ml (2536 kcal), 160 ml (2727 kcal) and 140 ml (2920 kcal). This difficulty in adapting largely explains the body weight differences observed at the onset and at the end of laying.

2. Effect of the addition of fat 2.1. Materials and methods We took up the same experiments and studied the diets where the increase in energy level resulted from an increase in fat content. We also took up other experiments looking at the effect of fats at a constant energy level. This involved experiments carried out by Halle (1996) and Whitehead (1981, 1991 and 1993). The main characteristics of the diets are shown in table 1. For each of the experiments, we used a regression method to determine the effect of a 100 kcal change in energy level on variations in energy consumption, rates of lay and egg weights. 2.2. Results The addition of fat increases the palatability of the feed, increases the feed energy density and consequently the quantity of energy intake. The zoo technical results are shown in table 2 of the appendix. Variations in performance observed for a 100 kcal change in energy level are given in table 7. Variations have been expressed as percentages. Table 8: Effect of addition of fats on variations in intake, rates of lay and weight of eggs, expressed as a % for an increase of 100 kcal in feed energy level. Authors Walker (1991) Peguri (1991) ISA –Joly (1997) Harms (2000) Halle (1996) Average

Fat added, % 0 -3 2 – 3.8 0-1-2 0-6 2.5 - 5

Intake +1.12 -0.44 +1.33 +3.00 +2.20 +1.44

Rate of lay n/a -0.44 0 0 +0.48 0

Egg weight +0.56 +0.04 +0.12 +1.51 +0.58 +0.56

Energy levels used (kcal) 2775-2990 2928-3010 2700-2800-2900 2798-3078 2556-2687

Effect on feed consumption: Consumption appears to depend on the quantity of added fat. Harms (2000) on introducing 6% fat into the feed at 36 weeks, observed an increase in energy consumption of 8.4% over the following 8 weeks. For Halle (1996) when the level of added fat rose from 2.5% to 5%, feed consumption increased by 3%. The experiments carried out by Grobas et al (2001) allow the energy level effect to be separated from the added fat effect. For this, 2 energy levels were compared, 2680 and 2810 kcal each one incorporating either 0% or 4% fat. The quantity of energy intake was not affected by the energy level but only by the incorporation of fats. At an equal energy level, the energy intake increases by 2.8% with the addition of 4% fats. This effect was also observed by Walker (1991). No increase in intake was observed when the feed energy level increased at a constant fat level. However, the addition of 3% fats brought about an increase of 2.0% in daily energy intake. The results obtained by Peguri (1991) and Whitehead (1991) seem to disagree with the other results, but also with many earlier results.

Energy levels and feed presentation for laying hens

2009-10 Page | 5

Table n°9: Effect of addition and nature of fats on variations in intake, laying rates and egg weight expressed as % in the absence of variation in the energy level

Authors

Nature of fats used Maize oil 1.15% linoleic acid 0.88% linoleic acid Maize oil Coconut oil Fish oil Tallow Maize oil Maize oil Maize oil Maize oil Soya oil Coconut oil

Fat level %

Intake

Whitehead 0 - 5.5 n/a (1991) 0-4 +2.80 Grobas (1999) 0.4 - 3 -0.35 Whitehead 0-6 (1981) 0-6 Whitehead 0-6 (1993) 0-6 # 0-1 # 0-2 # 0-4 # 5 # 5 # 5 Halle (1996) # # (1) i.e. 2.5 grammes – (2) i.e. 1.2 grammes - (3) i.e. 1.5 grammes

Laying rate n/a +2.05 -0.54 -1.04 +0.30 - 8.40 -0.73

Egg weight ca. 4 %(1) +1.9 % (2) +2.63 %(3) +4.28 % +1.39 % -1.95 % +1.11 % + 0.35 % +1.04 % +5.16 % 65.71g 65.51g 64.79g

Energy Level used (kcal) 2727 2745 2632 2713 " " " " " " 2687 " "

In many experiments, the addition of fats seems to have a specific effect on energy consumption due to better palatability and physical form of the feed. It is equally possible that the lipids energy density tends to cause over consumption. Such results are shown in table 9. These experiments attempt to determine the effect of fats at a constant energy level. The results obtained by Harms (2000), Halle (1996) and Grobas (1999) lead one to suppose that the increase in intake depends on the quantity of lipids added and their unsaturated fatty acid content. Performances Number of eggs: The number of eggs produced does not seem to be affected by the use of fats. Only Grobas (1999) observed a statistically significant increase in rates of lay. Egg weight: The egg weight increases with increasing feed energy levels. The increase can be estimated at about 0.6% for an energy level change of 100 kcal. This represents about 0.4 grams. This increase in egg weight is linked with an increase in the energy intake and weight of the hens. The mass of egg produced increases by the same proportions. When the effect of the oil is studied at a constant energy level, a relatively large increase in egg weight is observed. This increase depends equally on the type of fats used. This has been studied by Whitehead (1993) and by Halle (1996). Whitehead (1991) gives the change in egg weight after 5 weeks of use. Oils rich in polyunsaturated fatty acids are responsible for a large increase in egg weight. This effect seems to be an indirect effect linked to the increase in the quantity of energy intake and their energy value. Castaing (1995) allocated the same quantity of energy to different batches of hens receiving different fats at varying levels and having varying levels of linoleic acid. He observed no difference in egg weight between the different treatments. It is possible to conclude that the oils improve the palatability of the feed, bringing about an increase in energy consumption, and as consequently an increase in the weight of the hen and the egg weight. Energy efficiency: The energy efficiency, expressed in kcal per gram of egg production, falls away when the energy level of the feed is increased. This fall in the efficiency can be attributed in part to an increase in body weight, and in part to a fattening of the hens as witnessed in the trial carried out by Harms (2000).

Energy levels and feed presentation for laying hens

2009-10 Page | 6

3. Effect of the form in which feed is presented 3.1. Presented in crumb or pellet Presentation of the feed in granular or crumb form theoretically allows feed consumption to increase, but this assumes that the feed is actually presented in crumb or granular form in the feeder. In practice, feed granulation also leads to problems with shell quality. To resolve this, it would be necessary to be able to incorporate carbonate particles after feed granulation. Presentation of the feed as pellets or crumbs is known to reduce feed consumption time with an increase in the frequency of feather pecking and mortality as a consequence. Poor quality pellets or crumbs can often lead to under consumption due to the accumulation of fine particles in feeders or because of their unpalatability. Newcombe and Summers (1985) have shown that consumption by pullets was reduced with an increase in the amount of cellulose added to the feed, whether presented finely milled or as crumbs. However, feed granulation, increasing the feed density, allowed the reduction in energy intake to be limited. Many studies have been undertaken in recent years on the relationship between feed presentation and feather pecking. Savory et al (1997) observed that for hens raised on the ground, consumption times are significantly lower when the feeds are presented in pellet or crumb form, and that the frequency of feather pecking by peers is significantly lower when feeds are presented in finely-milled form. Their observations were carried out at the age of 21 weeks (i.e. 6 weeks after the change of feed) in the first experiment (in cages) and from 21 to 23 weeks in the second study (on the ground, with litter). These authors noted that presentation of the feed as pellet provoked feather consumption. These results have been confirmed by other studies. Walser et al (1996) considered that feather pecking behaviour could be influenced by feed structure. Hens receiving a feed in finely-milled form spent longer eating, pecked less and had better plumage. However these results were not confirmed by Wahlström et al (2001). Neither plumage quality, nor wound percentage, nor mortality percentage at 80 weeks were affected by the feed type presented (pellet or finely-milled). The hens were on litter, with perches available. It is however possible that the lack of results was due to the fact that the feed used was rich in fibre and had a very low energy level (2490 kcal). Aerni et al (2000) also noted a reduction in consumption time when the feed was in pellet. This leads to an increase in feather pecking and plumage degradation for laying hens without access to a straw litter. Comparing the effects of feed dilution and feed presentation, Hartini et al (2003) observed a reduction in consumption time when the feed was low in fibre. The authors also noted that the frequency of feather pecking depended both on the form of the feed and its fibre content. This is corroborated by Vilarino et al (1996) who noted that consumption times depended upon the feed density and presentation. They concluded that feeding behaviour was affected by the feed’s physical characteristics. Mortalities observed in the 2 experiments carried out by Hartini et al (2003) are shown below (table 10). The hens were housed in cages, subjected to raised light intensity, not debeaked, and aged 70 weeks in experiment 1 and 54 weeks in experiment 2. Table n°10: Effect of feed fibre content along with presentation on mortality Fibre content

Presentation

Low High Low High

Pellet Pellet Finely-milled Finely-milled

Mortality in % Exp.1 Exp.2 19 44 c 12 17 b 11 22 bc 6 11 a

Energy levels and feed presentation for laying hens

2009-10 Page | 7

In conclusion, the consumption time by hens depends on the form in which the feed is presented and leads to an increase in feather pecking where the environment is unfavourable. It seems that feather pecking is not observed when hens have litter available or when the feed is low in energy. Aerni et al (2000) concluded that hens with no access to litter should be fed with finely milled feed, and that litter becomes indispensable when feed is presented in pellet form. When egg production is in cages, presentation of the feed in crumb form increases the risks of feather pecking. This can be reduced by the careful control of light intensity and duration. There is no question that presentation in crumb or pellet form leads to improved energy consumption with diets which are diluted or where particle size is unsuitable.

3.2. Effect of granulometry Feed consumption is highly dependant upon granulometry. Chickens have a marked preference for grains. They are easy to pick up and do not lead to beaks becoming clogged. A hen will always tend to leave fine particles. We (ISA, 1999) carried out the following trial: a commercial feed, of good particle size, was re-milled through a finer screen. The feeds were distributed from 19 weeks of age. The results are shown in table n°10. Table n°11: Influence of feed granulometry on performance of laying hens between 23 and 51 weeks Particle size

Difference in %

Standard

Fine

< 0.5 mm

9%

31 %

> 3.2 mm

10 %

0%

0.5 to 3.2 mm

81 %

69 %

> 1.6 mm

65 %

21 %

Laying, %

93.9

90.7

- 3.4

Egg weight, g

63.3

62.7

- 0.9

Egg mass, g/j

59.41

56.85

- 4.3

Consumption, g/j

118.1

114.2

- 3.4

Consumption Index

1.989

2.008

+ 0.9

Weight at 33 wks (g)

1.930

1.883

Feed consumption is reduced by about 4 g when the feed is finely ground. This leads to a reduction in rate of lay of 3.4% (6.3 eggs), a reduction in egg weight of about 1%, and the egg mass is reduced by 2.6 g/day. Distribution of fine feed is equivalent to rationing for hens. The laying rate proves to be affected more than the egg weight. Currently, feed restrictions always translate into lower rates of lay.

4. Conclusions and practical applications Variation of the feed energy level within the 2400 to 3000 kcal range has no effect on egg production. However, when the energy level rises by 100kcal, the quantity of energy intake increases by 1.2% leading to an increase of 0.2 grams in egg weight and about 25 g in body weight of the hen. The energy efficiency expressed in kcal per gram of egg produced becomes higher in line with the increase in the feed energy level. When the feed is diluted, the reduction in consumption is most noticeable at the time the change of feed takes place. The hens increase their consumption level gradually over several weeks.

Energy levels and feed presentation for laying hens

2009-10 Page | 8

Energy regulation depends upon the dilution methods used. Feed density (g per litre) seems to be the limiting factor in intake regulation. By increasing the intake volumes and consumption times, dilution leads to a reduction in energy intake, an improvement in plumage and viability. Feed consumption is highly dependent upon the volume to be ingested. The presence of insoluble fibre appears indispensable, causing an increase in gizzard size, improving starch digestibility and limiting feather pecking by reducing the need to ingest feathers. Inversely, the addition of fat leads to an improvement in the palatability of the feed and therefore to an increase in energy intake which can be quite considerable. An increase in egg weight is just one consequence of this. The increase in quantity of energy intake and the effect on egg weight depend upon the quantity and nature of the added fats. The principal applications and recommendations are: Pullet feed: this must have an energy level lower than or equal to that of feed for laying hens and must be of lower density, to encourage consumption at the onset of laying. Feed for laying hens: At the onset of laying, it is desirable to encourage feed consumption and quickly to obtain eggs of marketable size. For this, a feed enriched in fat and incorporating a minimum of insoluble fibre is recommended. After the onset of laying, a slightly lower energy level, richer in cellulose, will allow a good energy efficiency to be obtained (expressed in kcal) and plumage to be maintained. This strategy could be particularly beneficial for alternative production (free range, organic…), especially in the absence of ground litter. From the practical point of view, the effect of raw materials which are rich in cellulose (insoluble fibre) and of low density can be compensated by the use of fat. Feed granulometry also affects energy consumption. Particles which are too fine lead to a reduction in consumption. It appears therefore that the following 3 factors need to be controlled: feed presentation, cellulose content and oil content. A balance between these 3 criteria needs to be researched to allow the fullest expression of the genetic potential at the lowest cost. The hens’ consumption time depends on the cellulose content of the feed. Feather pecking is inversely proportional to consumption time. Where hens are reared on the ground or in henhouses, it is best therefore to avoid energy levels which are too high, and to incorporate a minimum of cellulose. The use of a minimum of litter in the runs is recommended.

REFERENCES AERNI, V., EL-LETHEY,H. and WECHSLER, B. (2000). Effect of foraging material and food form on feather pecking inlaying hens. British Poultry Science, 41, 16-21 BALNAVE, D. and ROBINSON, D. (2000) . Amino Acid and Energy Requirements of Imported Brown Layer strains. RIR DC publications N° : 00/179 CASTAING, J. and BOUVAREL, I. (1995). Influence du taiux de maÏs et du niveau d’acide linoléique dans l’aliment pondeuses. Sciences et Techniques Avicoles. 10, 10-13 GLEAVES, E.W., and al. (1965) . The action and interaction of physiological food intake regulators in the laying hens. Poultry Science, 45 : 38-67 GROBAS, S., MENDEZ, J., DE BLAS, C., and MATESS, C.G. (1999). Laying hen productivity as affected by energy, supplemental fat, and linoleic acid concentration of the diet. Poultry Science, 78, 1542-1551 HALLE, I. (1996). Effect of dietary fat on performance and fatty acid composition of egg yolk in laying eggs. Arch. Geflüglek, 60, (2), 65-72 HARMS, R.H, RUSSEL, G.B and SLOAN, D.R. (2000). Performance of four strains of commercial layers with major changes in dietary energy. J. Appl. Poultry Res. 9 : 535 –541 HARTINI, S., CHOCT, M., HINCH, G. and NOLAN, J., (2003) . Effect of diet composition, gut microbial status and fibre forms on cannibalism in layers. A report for the Australian Egg Corporation Limited. April 2003. HARTINI, S., CHOCT, M., HINCH, G., KOCHER,A. and NOLAN, J., (2002) . Effect of light during rearing and beak trimming and dietary fiber sources on mortality, egg production and performances of ISA Brown laying eggs. J. Appl. Poult. Res. 11:104-110

Energy levels and feed presentation for laying hens

2009-10 Page | 9

HETLAND, H. and CHOCT, M. (2003). Role of non starch polysaccharides in poultry nutrition. th Proceedings of the 14 Eur. Symp. Poult. Nut., Aug. 2003 (Lillehammer, Norway) HETLAND, H., SVIHUS, B.and KROGDAHL, A. (2003). Effects of oat hulls and wood shavings on digestion in broilers and layers fed diets based on whole or ground wheat. British Poultry Science, 44, 275-282 JOLY, P., and BOUGON, M. (1997). Influence du niveau énergétique sur les performances des ème pondeuses à oeufs roux et évolution de l’ingéré en fonction de l’âge. 2 journée de la Recherche Avicole- 8-9-10 avril 1997, 2, 115-120 LEESON, S., SUMMERS, J.D., and CASTON, L.J. (2001). Response of layers to low nutrient density diets. J. Appl. Poultry Res., 10, 46-52 MORRIS, T.R. (1968). The effect of dietary energy level of the voluntary calorie intake of laying birds. British Poultry Science, 9, 285- 295 NEWCOMBE, M., and SUMMERS, J.D. (1985). Effect of increasing cellulose in diets fed as crumbles or mash non the food intake and weight gains of broiler and leghorn chicks. British Poultry Science, 26, 3542 PEGURI, A. and COON, C., (1991). Effect of temperature and dietary on layer performance. Poultry Science, 70, 126-138 SAVORY,C.J. and HETHERINGTON, J.D. (1997). Effects of plastic anti-pecking devices on food intake and behaviour of laying hens fed on pellets or mash. British Poultry Science, 38, 125-131 STEENFELT,S., ENGBERG,R.M. and KJAER, B., (2001). Feeding roughage to laying hens affects egg th production, gastrointestinal parameters and mortality. Proceedings of the 13 Eur. Symp. Poult. Nut., Oct. 2001 (Blankenberge, Belgium) VAN DER LEE, A.G., HEMKE, G., and KWAKKEL, R.P. (2001). Low density diets improve plumage condition in non-debeaked layers. 13 th European Symposium on Poultry Nutrition. Blankenberge, Belgium. Sept 30 – oct 04. p244-245. VILARINO, M., PICARD, M.L., MELCION, J.P. and FAURE J.M., (1996). Behavioural adaptation of laying hens to dilution of diets under mash and pellet form. British Poultry Science, 37, 895-907 WAHLSTRÖM, A., TAUSON, R. and ELWINGER, K. (2001). Plumage condition and health of aviarykept hens fed mash or crumbled pellets. Poultry Science, 80, 266-271 WALKER, A.W. , TUCKER, S.A and LYNN, N.J (1991). Effect of nutrient density and fat content on the performance of laying hens . British Poultry Science, 32, 1138-1139 WALSER,P.,PFIRTER, H.P. and WENK, C., (1996). Effect of feed structure and feed composition on performance and feather pecking in two strains of white leghorn hens. Proceedings of the World Poultry Congress. New Delhi, India. Vol-IV p 259 WHITEHEAD, C.C.(1981). The response of weight to the inclusion of different amounts of oil and linoleic acid in theee diet of laying hen. British Poultry Science, 22, 525-532 WHITEHEAD, C.C, BOWMAN, A.S. and H.D. GRIFFIN.(1991). The effects of dietary fat and bird age on the weights of eggs and egg components in the laying hen. British Poultry Science, 32, 565-574 WHITEHEAD, C.C, BOWMAN, A.S. and H.D. GRIFFIN.(1993). Regulation of plama oestrogen by dietary fats in the laying hen: relationships with egg weight. British Poultry Science, 34, 999-1010

Energy levels and feed presentation for laying hens

2009-10 Page | 10