title: Effect of reducing dietary mineral content on growth performance, water intake, excreta dry matter content and blood parameters of broilers.
abstract: 1. The objective of this study was to investigate whether it is possible to reduce phosphorus (P) excretion by feeding a lower level of dietary P than that currently recommended, without compromising welfare, and whether this is sensitive to the level of dietary calcium (Ca). 2. A randomised complete block design was used with a total of 224 1-d-old male chicks of a commercial genotype in two batches. Chicks had a 10-d adaptation period. After this, they were moved to cages and allocated to one of 4 dietary treatments (4 and 3 birds per cage in batch 1 and 2, respectively). A standard level of Ca and P (8.3 and 6.6 g/kg, respectively) was compared with three lower levels of Ca (7.3, 6.3 and 5.3 g/kg) all at the same reduced level of P (5.5 g/kg). Records were made of live weight of birds on an individual basis and feed and water consumption on a cage basis. Every 7 d, the dry matter (DM) content of a sample of mixed excreta from each cage was measured. Birds were slaughtered and samples taken for analysis of plasma mineral content, retention of N, Ca and P and tibia bone strength. 3. The initial reduction in dietary mineral level did not adversely affect performance or bone strength. However, decreasing dietary Ca level below 7.3 g/kg, at constant P, led to reduced feed consumption and bone strength. Dietary treatment had no significant overall effect on water intake, water : feed ratio, excreta DM content, Ca and P retention or metabolisability of DM. There was no significant correlation between mean plasma Ca or P level and DM content of rectal digesta. 4. In conclusion, reducing dietary P from 6.6 to 5.5 g/kg to reduce potential environmental impact of broiler production had an adverse effect on bird welfare when the level of Ca was reduced below 7.3 g/kg, as a result of decreased feed intake in the early growth period and reduced skeletal strength.
authors.affiliation: Shahid Bahonar University of Kerman, Iran. Nemat.Ziaei@ncl.ac.uk
authors.forename: N
authors.initials: N
authors.lastname: Ziaei
authors.forename: J H
authors.initials: JH
authors.lastname: Guy
authors.forename: S A
authors.initials: SA
authors.lastname: Edwards
authors.forename: P J
authors.initials: PJ
authors.lastname: Blanchard
authors.forename: J
authors.initials: J
authors.lastname: Ward
authors.forename: D
authors.initials: D
authors.lastname: Feuerstein
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D002118:Calcium / Q000378:metabolism; D002136:Calcium, Dietary / Q000008:administration & dosage*; D002645:Chickens / Q000097:blood / Q000254:growth & development / Q000502:physiology*; D004032:Diet; D004326:Drinking; D004435:Eating; D008297:Male; D008903:Minerals / Q000008:administration & dosage*; D010758:Phosphorus / Q000378:metabolism; D016226:Phosphorus, Dietary / Q000008:administration & dosage*; D013977:Tibia / Q000502:physiology
chemical_list: D002136:Calcium, Dietary; D008903:Minerals; D016226:Phosphorus, Dietary; D010758:Phosphorus; D002118:Calcium