MEXICO - Encouraging broilers to be more active did not reduce growth but had little beneficial effect on their leg health in two experiments, Mexican researchers report, although it did affect the birds' behaviour.
The results of two experiments in Mexico suggest that longer distances between feed and water in the broiler house have limited effects on bone strength but affect bird behaviour by increasing the latency to lie – in other words, birds spend more time lying down.
According to the authors – led by C.A. Ruiz-Feria of Texas A&M University in the US – this behavioural difference may change feeding patterns and carcass characteristics, as evidenced by the lower abdominal fat content in these broilers.
The researchers also found that the presence of ramps or inclination appeared to weaken the leg tendons.
In the introduction to their a paper in Poultry Science, Ruiz-Feria and co-authors explained that lameness or leg weakness is becoming an important problem in broilers selected for rapid growth, and although the causes are not known, sedentary behaviour could be a cause.
They conducted two experiments to study the effects of distance and the presence of ramps between resources (feed and water) on bone and tendon strength, ability to stand and productive performance.
In experiment 1, straight-run (mixed-sex) Ross 708 chicks (n=1,260) were randomly assigned to one of three treatments: 1.0, 3.3 or 6.6 metres between resources (six pen replicates per treatment).
In experiment 2, Cobb 500 male chicks (n=864) were randomly assigned to one of four treatments (2×2 factorial, four pen replications per treatment) consisting of two distances (3.0 or 8.0 metres) with (WR) or without (NR) a ramp (a triangular prism 31cm high and 132cm wide at the base).
On days 21, 45, and 56 (experiment 1), or days 28, 35, 42 and 49 (experiment 2), birds were weighed, killed, and tibias collected to measure breaking strength (BBS), and abdominal fat (AbF) content.
On day 49 (experiment 2), calcaneus tendons were also collected to measure breaking strength (TBS). Foot pad lesions and latency to lie (LTL) were determined before killing the birds.
In experiment 1, distance did not affect BBS, LTL, foot pad lesions or bodyweight but on day 49, birds in the 6.6-metre treatment had lower AbF than birds in the other treatments.
In experiment 2 on day 49, birds in the 8.0-metre treatment tended to have a higher BBS than birds in the 3.0-metre treatment (P=0.09), whereas WR birds had lower tendon breaking strength than NR birds (P<0.01). However, LTL was highest in 8-metre NR birds.
Final bodyweight was not affected by distance but birds in the NR group were heavier than birds in the WR group, and AbF was lower in 8-metre than in 3-metre birds.
Ruiz-Feria C.A., J.J. Arroyo-Villegas, A. Pro-Martinez, J. Bautista-Ortega, A. Cortes-Cuevas, C. Narciso-Gaytan, A. Hernandez-Cazares and J. Gallegos-Sanchez. 2014. Effects of distance and barriers between resources on bone and tendon strength and productive performance of broiler chickens. Poultry Science. 93(7):1608-1617. doi: 10.3382/ps.2013-03421
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