Effects of housing and calcium-deficient diet on health and egg production in Bovans Brown hens
Public concern about the welfare of hens kept in conventional cages has become an important issue worldwide. The conventional cage system has been banned by the European Union since 2012. Several housing systems, including free range, have been developed as welfare friendly alternatives to the conventional cage system. In Experiment 1, the study examined the effects of housing environment, conventional cages vs. floor pens, on hens' health and egg production. Results showed there were no environmental effects on daily egg production, plumage condition, and feet hyperkeratosis of hens (P > 0.05, respectively). Compared to hens housed in floor pens, caged hens had longer claws (P < 0.0001). In addition, caged hens had greater egg weight at 22 wk of age (P = 0.001); while floor pen housed hens had cumulative higher %shell and shell thickness (P = 0.002 and P = 0.02, respectively). Floor pen housed hens also had greater BMD (bone mineral density) and BMC (bone mineral content) in the measured bones than those of the caged hens (P < 0.05). The H: L ratio, an immunological response parameter and stress indicator, was higher (P = 0.002) in caged hens than hens housed in floor pens. Overall, the results suggest that furnished floor pens may be a favorable alternative housing system to conventional cages for improving hen welfare; however the cages still have certain advantages for egg production. In Experiment 2, the study was to determine the effects of Ca-deficient diet on hens' health and egg production. A total of 120 20-wk-old Bovans Brown hens were randomly assigned into twelve 10-bird floor pens. After 2 wks acclimation to the environment, hens of half pens were treated with a Ca-deficient diet and other half hens were fed with a commercial layer diet for 4 wks. Each floor pen provides 3711 cm2 floor space per hen, and was furnished with perches, nest boxes, and wood shaving litter. During the 4 wk trail, experimented hens were fed with a diet contain 0.9% of Ca, while control hens were fed with a diet contain 3.3% of Ca. Eggs were collected and recorded for daily production; and egg and shell traits were analyzed at wk 22, 24, and 26. Eating, drinking, and perching behaviors were observed using scan sampling weekly from wk 22 to 26. Body weight, liver weight, and abdominal fat pad weight were measured at wk 26. Bone parameters including BMD and BMC of the tibia, femur, and humerus, bone ash, and bone Ca and P concentrations; and stressor indicators including liver fat, plasma epinephrine and norepinephrine, and H: L ratio, were also analyzed. Results showed that accumulative daily egg production and both shell thickness and shell percent were lower in Ca-deficiency fed hens compared to controls (P = 0.02 and P < 0.001, respectively), but there were no treatment effects on egg weight and size (P > 0.05). No difference was observed in hen body weight between treatments, but the liver weight and liver fat was higher in hens fed regular diet (P = 0.05 and P = 0.003, respectively). Drinking behavior was not affected by treatment (P = 0.77) but eating and perching activities were higher in control hens (P < 0.0001 and P = 0.01, respectively). Both BMD and BMC in the retrieved bones were lower in Ca-deficiency diet fed hens than controls (P < 0.05, respectively). The immunological parameters including H: L ratio and the plasma EP and NE were no affected by treatment (P > 0.05, respectively). Short-term deprivation of dietary Ca in Bovans Brown hens at the onset of egg laying had negative impact on egg production, shell quality, and skeletal mineralization, which will cause further economic loss and hen welfare issues. The data further evidences that dietary supplement of Ca is one of the critical factors to maintain chicken health and production. (Abstract shortened by UMI.)
Cheng, Purdue University.
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