management guides cannot accommodate this transient en- ergy change in predictions of daily feed intake, since timing (days of age) of the diet change is so variable.

Feed texture While colour, taste and nutrient/ingredient composition may contribute to a transient change in feed intake in response to novel feeds, it is clear that the main factor impacting ‘feed re- fusal’, is feed texture. For broilers this is most noticeable in the change from starter crumbs to grower pellets. We feed pellets because it allows for rapid intake within competitive feeding systems and reduces the net energy for maintenance of feed- ing activity and so improves the F:G. Delaying the introduc- tion of pellets because of the perception that young birds “will not eat pellets”, ensures reduced feed efficiency. You cannot expect the same feed efficiency of birds fed pellets (vs small crumbs) introduced at 15d vs as late as 24d, as some- times occurs. Research suggests that when given a choice, young broilers prefer large particles and generally avoid the smallest particles (Table 3).

Table 1 – Relative significance of factors impact- ing transitory feed intake due to diet change.

Feed texture

Ingredient composition Feed hardness/density Nutrient profile Feed colour Feed taste

50% 15% 10% 10% 10% 5%

Table 2 – Effect of dietary energy change on expected daily feed intake.

Day 17 Day 18

Starter @ 3000kcal/kg 87g/d = 260kcal/d 93g/d = 279kcal/d

-3g/bird/d = -150kg/d for 50,000 broilers

Table 3 – Feed particle size preference of broilers in first 4h following introduction of a novel mixed-size feed.

>2.4 mm

1.2-2.4 mm 0.9-1.2 mm 0.6-0.9 mm <0.6 mm

(Portella and Leeson,1985) 20 ▶ POULTRY WORLD | No. 1, 2021

8d age 46% 54% 0 0 0

16d age 38% 59% 0 0

3% Grower @ 3100kcal/kg 90g/d = 279kcal/dJaar

Birds do not like change in any aspect of their environment and take time to adjust to novel situations. This is particularly important to the bird when it comes to feed, since a novel of- fering may be hazardous and so they are initially wary and take time to investigate and eventually accept the new feed. However, this adjustment time may be much shorter than is suggested by anecdotal observations on the farm. The broilers initial reluctance to eat pellets is associated with certain behavioural changes. Birds actually approach the feeder more often at this time, but this is often with a ‘closed beak’ which supports the observation of birds ‘playing’ with the feed or even scattering feed onto the litter. In the first 20 minutes there are also more instances of birds picking up the pellets but not swallowing them, so again they may be dropped onto the litter. In one study, dropping pellets onto the litter increased ten-fold in the first 20 minutes after initial- ly offering pellets, although actual wastage was just a few grams/bird. Pellet hardness and colour have been shown to have little impact on this transient ‘feed refusal’ behaviour.

No feed phobia These feed phobia behaviours therefore form the basis for the supposition that broilers “won’t eat pellets” at an early age, and thus the necessity to feed crumbs much later in the pro- duction cycle. However, such feed phobia are going to occur regardless of age and delaying the introduction of pellets to, say, 21-24 days is, in fact, going to have a bigger impact on reduced growth than accepting any transient step-back at an early age. Research findings do not support the contention that changing to pellets sets the bird back by 2-3 days. De- tailed observations show that for individual birds ‘feed refusal’ is observed mainly in the first 20 minutes but that within 24 hours of the diet change, there is compensatory feeding that normalises, or even exceeds, expected feed intake for that day. We rarely measure this overall intake pattern but rather respond to that first 20 minutes of clearly seen feed phobia. Consequently, transient feed refusal is an inevitable and inher- ent behaviour but one that we can perhaps temper. Since birds are reacting to a novel situation, an obvious approach is to make sure that birds have access to some pellets prior to the changeover. Adding 5% pellets to a crumbed feed 5-7 days ahead of the changeover is one approach, while a more com- mon solution is to feed 50:50 (crumbs: pellets) as the first deliv- ery of feed at the transition time. An even more radical ap- proach would be to offer the first pelleted feed as a ‘poor quality’ pellet. But even with an abrupt change from crumbs to pellets, the economic loss in terms of wasted feed or reduced growth rate is probably much less than suggested by casual observation of initial bird behaviour. We should accept these transition issues and get it over and done with as early as possi- ble, to capitalise on the amazing ability of the broiler to eat pelleted feed and so promote growth and feed efficiency.

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