The effects of climatic stress on egg formation (weight, shape, formation period, clutch size and blood calcium) and shell quality were estimated in White Leghorn and White Plymouth Rock hens. Constant environments were used with 85°F 75- 80% r.h., 75-77°F 50-60% r.h. and 55°F 50-60% r.h. as well as a fluctuating environment with 10 h (day) 85°F 75-80% r.h. and 14 h (night) 65-70°F 50-60% r.h. The effects of dietary vitamin C (50 or 100 mg/kg feed), NaHCO 3 2.1 % and antibiotics were also tested.The author concluded the following. Fluctuating temperature had no effect. In heat-stressed hens vitamin C improved the diminished shell quality and raised blood calcium.At 75°F vitamin C and NaHCO 3 increased egg weight and shell quality. Combinations of antibiotics improved egg and shell weight. Microscopy of ground sections of the shell showed that heat diminished shell thickness and impaired the crystal structure of the calcified shell; vitamin C addition improved shell thickness.
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