Plasma progesterone and luteinizing hormone (LH) profiles were obtained during the first ovulatory cycle of heat-stressed (HS, 35 C; n = 24) and unstressed (US, 17 to 27 C; n = 24) hens using 30-min sampling intervals beginning approximately 6 h prior to ovulation. Progesterone levels from HS hens were lower from 6 h [.07 +/- .01 (SE) versus 1.66 +/- .25 ng/mL; P = .008] to predicted ovulation (.06 +/- .006 versus .70 +/- .18 ng/mL; P = .07). Likewise, LH levels from HS hens were lower from 6 h (1.55 +/- .16 versus 3.86 +/- .34 ng/mL; P = .007) to predicted ovulation (1.63 +/- .18 versus 2.50 +/- .27 ng/mL; P = .01). Eggs from HS hens were more often laid early (less than 24 h) than eggs from US hens (71.42 versus 13.33%, respectively; P = .01), but US hens more often laid eggs of a normal oviposition interval length (24 to 26 h) compared with HS hens (73.34 versus 14.29%; P = .0005). The percentage of delayed eggs (greater than 26 h) was not different (US, 14.29 versus HS, 13.37%; P = .75) between the two treatment groups. Basal production of progesterone by dispersed granulosa cells from US hens was 97.62 +/- 16.01 ng/mL. Challenge by LH increased this to 417.50 +/- 53.38 ng/mL (P = .0001). In contrast, basal progesterone secretion by cells from HS hens was 40.25 +/- 6.60 ng/mL (P = .0001) and LH challenge failed to increase progesterone production.(ABSTRACT TRUNCATED AT 250 WORDS)
An experiment was conducted to study calcium appetite and dietary calcium level related to laying hen performance. The experiment consisted of three periods: pre-experimental, training, and experimental. A total of 80 commercial strain laying hens (58 weeks old) were divided into two groups. One group (20 birds) served as a control throughout the experiment and was fed 3.5% dietary calcium without a free-choice calcium supplement. The other 60 birds were randomly divided into 3 sets of 20 and were all fed 3.5% dietary calcium for a pre-experimental period (13 days) as an adaptation period to a new environment prior to a training period (5 weeks). Dietary calcium level was decreased by .5% each week through the 5th week (to 1% Ca) for all 60 hens during the training period. The birds were given access to a free-choice calcium supplement (calcium carbonate granules) during both the pre-experimental and training periods. This dietary regimen was used in an effort to allow all hens to adapt to a supplemental feeding program and be prepared or conditioned for sudden changes in dietary calcium level. At the end of the training period, the 3 sets of 20 hens were fed either 1, 3, or 5% dietary calcium and a free-choice calcium supplement for 6 weeks. As dietary calcium level was increased, there was a decrease in free-choice supplemental calcium intake; however, all birds (except controls) consumed very large amounts of calcium. The training procedure was successful: no hens rejected the supplement. Neither dietary calcium level nor total calcium intake affected feed intake.(ABSTRACT TRUNCATED AT 250 WORDS)
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