Beak regrowth measures followed a predictable
growth curve based on guard-plate length and energy
setting. Birds trimmed using the shorter plate
(25/23C) had shorter upper and lower beaks compared
with those trimmed with the longer (27/23C) plate, as
more beak tissue was exposed to the infrared energy (P
< 0.0001; Tables 1 and 2). The greater the energy level
used, the shorter the upper, and generally, lower beak
length. However, a difference in BW based on beaktrimming
protocol was unexpected (P < 0.001; Table
3). Although differences in BW were rarely significant
at each given sample time, repeated measures analysis
of body BW showed differences across all time periods.
Previous studies have shown alterations in feeding behavior
and BW of trimmed birds (Gentle, 1986; Hester
and Shea-Moore, 2003). These differences are generally
no longer detectable by sexual maturity (Cunningham,
1992). Hens trimmed with 27/23 (48) had the greatest
BW overall, whereas hens of 25/23 (44) protocol
had the lowest. Reductions in BW have been suggested
to be associated with the pain of beak trimming and
changes in the beak morphology that alter the bird’s
ability to perform natural feeding behaviors (Gentle et
al., 1982). Previous studies of pain and HB trimming
suggest that beak trimming-associated pain is more
common at young ages (Jendral and Robinson, 2004).
Therefore, the effect of BW is most likely due, at least
in part, to changes in beak morphology. Our data suggest
that infrared trimming protocols can be optimized
for longer beak length and improved BW compared
with conventionally trimmed hens.
The frequency of feeding behaviors did not differ between
beak-trimming treatments for any age observed
in the present study (P = 0.78). However, our analysis
of feed waste noted that hens trimmed with both plates
using the moderate energy setting (48) and the 25/23
(52) protocol tended to waste less feed compared with
HB hens (P = 0.089; Figure 1). Using only two 4-h periods
(4 h at both 20 and 30 wk of age) to collect feed
waste data resulted in a high degree of variability, ultimately
reducing our power to determine significant differences
between the beak-trimming protocols. However,
it did give us an initial view of how feeding efficiency
might change through differences in feed wastage based
on beak-trimming protocols. These data suggest that
energy level used for IR trimming may be a more important
factor when considering feed waste than plate
length. However, our data also show the need for further
study into the effects of different beak-trimming
protocols on feed waste.
Reduction in overall activity level has been seen in
trimmed birds and is suggested to be an indicator of
their reduced overall well-being (Hughes and Gentle,