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Energy - Fuel of Life

04 April 2014


Gary Hogue (Aviagen Regional Technical Manager, North America) and John Halley (Aviagen Nutritionist) offer advice to flock managers on choosing feed energy levels for their breeder flock.

Energy is often considered the 'Fuel of Life'. Primarily, it is needed for maintaining basic metabolism (maintenance energy). Any excess is then used for production of meat (growth) and/or eggs (production). Fed too much energy, hens become overweight (excess growth) leading to poor production. If fed too little energy, hens begin using protein to meet their basic maintenance needs and egg production may be compromised. As is the case with most things in life, balance is the key.

This article is an attempt to provide a flock manager with some tools to use when making decisions on feeding energy to a breeder flock. Some of the research cited is not current and is in no way intended to be anything more than an example of the thought processes that may be helpful when making difficult decisions about feeding.

Table 1 and Table 2 give a summary of research done by Pearson and Herron (1982) that predicts energy requirements of broiler breeders. Notice that at any given time, 70 to 85 per cent of the calories consumed are required strictly  for maintenance leaving only a small percentage leftover to use towards egg production. Internal data has shown that the figures given in Tables 1 and 2 are still relevant for today's modern broiler breeders.

To make things a little more interesting, variability exists in several areas that can change a flock’s energy requirement and thus how they allocate feed towards egg production. Flock condition, body weights, house environment, and feather condition are just a few of these areas. Using data obtained from several researchers as well as internal findings, below some scenarios in which adjustments that can be made to meet the energy needs of a flock are given.

Table 1. Predicted energy requirements of broiler breeder pullets to 20 weeks with a penBr>temperature, except brooding, of approximately 22°C (72°F)
  2 4 6 8 10 12 14 16 18 20
(kg) 0.20 0.36 0.60 0.82 1.05 1.25 1.48 1.70 1.95 2.16
(lb) 0.44 0.79 1.32 1.81 2.31 2.76 3.26 3.75 4.30 4.76
Predicted energy requirement (kcal/kg)
Total 70 120 140 165 190 218 235 250 265 290
Maintenance 40 80 100 125 146 165 185 200 220 245
% of total 57 67 71 73 74 76 78 80 83 84
Selected and rearranged data from Pearson and Herron (1982)


Table 2. Predicted energy requirement of broiler breeder hens from 20-68 weeks
at a pen temperature of approximately 22°C (72°F)
  20 24 28 32 36 40 44 48
(kg) 2.16 2.50 3.15 3.30 3.48 3.58 3.62 3.70
(lb) 4.76 5.51 6.94 7.28 7.67 7.89 7.98 8.16
 Egg production (5)
  5 60 85 82 77 73 68 63
 Average egg weight (g)
  47.2 54.4 58.6 61.1 63.3 65.2 67.1 68.4
 Average daily egg mass (g)
  2.4 33.0 49.8 50.1 48.7 47.6 45.6 43.1
 Predicted energy requirement (kcal/day)
Total 300 350 400 450 450 450 450 445
Maintenance 250 285 300 335 343 350 350 352
% of total 83 81 80 74 76 78 78 79
Selected and rearranged data from Pearson and Herron (1982)

As cooler weather approaches, house temperatures may fluctuate. Adjustments in feed allocation must be made in order to make up for the energy the birds use as they try to stay warm.

Estimating Energy Adjustment for Temperature Changes

A hen requires 30 kcal per day for each 5°C (9°F) change (reduction) in temperature (between about 15 and 25°C / 59 and 77°F).

A flock producing at a level of 60 per cent with an egg weight of 64g (27oz per dozen) and a bodyweight of 3.49kg (7.7lb) requires 388 kcal per day at 24°C (75°F), hens at 19°C (66°F) require 418 kcal per day.

For a diet with 2800kcal per kg (1270kcal per lb), this means an increase from 139g per bird and day (30.6lb per 100 birds per day) to 149g per bird and day (32.8lb per 100 birds per day).

A bird’s feathers act as an insulation barrier that allows it to maintain body heat more efficiently during cooler temperatures. Feathering must be considered when trying to allocate feed amounts under cooler house conditions. The loss of feathers in broiler breeders, whether they are housed close to thermoneutral or at cooler temperatures results in increased energy needs (Table 3).

Table 3. Predicted energy requirement (kcal/day) of a broiler breeder
with various feathering conditions
Feather Score
Pen Temperature °C (°F) Well feathered 20% feather loss 40% feather loss 60% feather loss almost no feathers
21°C (69.8°F) 450 464 495 536 601
14°C (57.2°F) 485 506 534 580 655

Average body weight of the flock is another factor that must be taken into consideration when determining feed amounts.

The following is a general rule for adjusting energy needs for over or underweight hens, within the range of body weights generally encountered.

Estimating Energy Adjustment for Body Weight Changes

Caloric needs increase by 10kcal per day for each 227g (0.5lb) change.

Example: A house of hens that average 3.63kg (8lb) requires an additional 3.6g per bird and day (0.8lb per 100 birds per day) of feed containing 2800kcal per kg (1270kcal per lb) when compared to a house of hens averaging 3.40kg (7.5lb).

Post peak feed allocation is critical to maintaining good persistency of lay over the life of the flock and can prove to be a difficult task to manage, especially when some of these other factors mentioned above are involved. Below is a general rule for calculating post peak feed reduction based on egg mass output.

Estimating Energy Adjustment for Egg Production Changes

Every one per cent difference in egg production (at same egg weight) alters the energy needs of the hen by approximately 1.85kcal per bird and day.

Example: 80 per cent egg production with a 65g (27.5oz per dozen) egg weight equals 52g per bird and day (1.83oz) egg mass output (EMO), if production drops to 79 per cent with same egg weight, EMO is 51.3g per bird and day (1.81oz). This is a 1.35 per cent drop in EMO, 0.0135 × 140kcal per egg = 1.89kcal per bird and day less energy required.

On a 2800kcal per kg (1270kcal per lb) diet, a 0.67g per bird and day (0.15lb per 100 birds per day) less feed would be necessary.

Energy management is critical for proper egg production to be attained and maintained. In the winter time, this becomes more difficult due to the many factors which can affect the amount of energy the bird has available for egg production.

The examples given here provide estimates of how the energy requirements of the bird can change, highlighting the fact that energy requirements do not remain constant and can be affected by a number of factors. Take this into account when determining feed levels.

Actual changes to feed amounts must be based on close monitoring of bodyweight gains, feather cover and feed reductions if egg production is to be kept on track.

April 2014

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