The GMD of the diet did not affect

The GMD of the diet did not affect productive performance
of laying hens except for ADFI (P < 0.05) that
was greater for hens fed coarse-ground cereals (10-mm
screen) than for hens fed medium- or fine-ground cereals
(6- or 8-mm screens). Consistent with these results,
Vandenboorn (1993) found that when the corn portion
of the diet was milled to pass through a 9- vs. a 3-mm
screen, egg production and FCR of hens from 22 to 36
wk of age were not affected. Furthermore, Hamilton and
Proudfoot (1995) observed that BW, egg production,
egg weight, and FCR of SCWL from 20 to 70 wk of age
were not affected when diets based on 57% soft wheat
were ground fine or coarse. Maclsaac and Anderson
(2007) reported that coarsely ground grains (corn and
wheat, milled to pass through a 7- vs. a 5-mm screen)
did not affect egg production, egg weight, ADFI, or
FCR of SCWL from 20 to 64 wk of age, which, except
for ADFI, is in agreement with our results. The authors
have not found any scientific report that studied
the influence of GMD of durum wheat on productive
performance of brown egg-laying hens. Afsharmanesh to 470, 560, and 630 µm in broilers from 1 to 21 d of
age and did not find noticeable differences among diets
on AME, CP, and P digestibility or on productive
performance. However, Nir et al. (1994) and González-
Alvarado et al. (2007, 2008) found that an increase in
particle size of the diet of broilers was associated with
increased gizzard weight, reduced gizzard pH, and improved
nutrient digestibility. González-Alvarado et al.
(2007) indicated that coarse particles accumulate in the
gizzard, stimulating organ development and increasing
the reflux of the digest from the intestine to the upper
part of the gastrointestinal tract. However, in their
trial, no differences in broiler productivity were found
as a consequence of increasing GMD. These observations
confirm the suggestion that the ability of poultry
to grind grains in the gizzard is high and that under
most practical conditions, a reduction in GMD of the
diet will not improve productive performance.