specifications can cause significant issues. Even if manage- ment and all other factors are followed correctly, with the wrong feed specifications the pullets will not be conditioned properly by 20 weeks of age.
Feed increases in rearing In rearing, the objective is to reduce stress, maintain bird growth, and achieve a minimum of 68% average uniformity. To accomplish these goals, use a minimum of 2 g/week feed increases in this period (depending on diet density). These are the general guidelines to follow. • Ensure the 7-day bodyweight is on target and strictly con- trol bodyweight from 2 to 4 weeks.
• From 4 to 10 weeks of age, it is better to err on the side of below the standard bodyweight rather than over the standard. This will allow 2 to 3 gram feed increases until 12 weeks of age, at which point, the average bodyweight should be on target. Erring on the side of below the stand- ard also prevents building a very large frame that will require more feed to maintain during production.
• From 12 to 20 weeks of age, it is better to err on the side of over the bodyweight target. This will enhance fat deposi- tion and allow production to start earlier because the pullets have been correctly conditioned.
See Figure 1 and Table 1 for examples of field data collected using the rearing method described here.
Auto scales versus hand weighing In Figure 2 the blue dots are data points collected from the automatic scale, while the green dots were collected from manual weighing. Note that after 15 weeks, the manual weights start to differ from the automatic scale weights. This occurred because the location of the manual weighing changed at 15 weeks. Manual weighing moved towards the large feed hopper where heavier birds are more prevalent. This demonstrates the importance of weighing consistently (same location, equipment, time of day, etc.) in the house. Automatic scales can save considerable money in labour costs. Hand weighing in rearing is equal or very close to the auto scale but all depends on the sample size of the birds and the weight range used for the scale (use 30% above and be- low the average weight). Have the auto scale operate for two hours before feeding to get a relatively accurate dry body- weight sample of around 200 birds daily. The auto scale is very effective in rearing, and at 20 weeks of age the variation with hand weighing will be less than 2%. However, the varia- tion increases in production. At about 25 weeks of age, the variation increases to 3% and by 60 weeks of age, the varia- tion may be 5-6 %. This variation in weighing data occurs in production because the heavier females do not go on the scales as much as lighter females. Moreover, males may inter- fere with the weights. Male body weight difference compared with females at 30 weeks of age can be around 10%, which
the scale would accept. For these reasons auto scales are very efficient during rearing but should not be used after 25 weeks. Building scales on the slats so that the weights of all females are measured is an option. However, it is most impor- tant to use auto scales in rearing to reduce workload and get consistent body weight and uniformity data.
Uniformity In many countries the availability of labour limits the ability to undertake gradings. With no gradings, pens are not used in the rearing house. However, the first 8 weeks of rearing are
Automatic scales in the house will collect a repre- sentative daily dry bodyweight, help to track weight gain and determine whether the average body- weight is on target.
Table 1 – An example of bodyweights collected following the rearing method described.
Age (weeks)
1 2 3 4 5 6 7 8 9
10 11 12 13 14 15 16 17 18 19 20
Deviation from
-9 -9 -7 -9 -7 -5 -5 -6 -4 -1 1 3 3 4 3 3 5 3 2
Field
Standard Bodyweight Bodyweight 1
147 258 371 488 580 692 800 898 973
1080 1195 1309 1431 1533 1656 1737 1884 2087 2215 2340
Feed
Amount (g) 26 33 37 40 44 46 48 51 54 57 60 63 66 69 73 77 83 88 93 98
▶ POULTRY WORLD | No. 7, 2022
Weekly Feed Increase 0 7 4 3 4 2 2 3 3 3 3 3 3 3 4 4 6 5 5 5
17
PHOTO: COBB
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44
