Relationship between oestrous behaviour and frequency of visits made by dairy cows to out-of-parlour concentrate dispensers.

Sixty-five oestruses in 38 cows were confirmed either by using progesterone concentration determined in milk or by conception to a service on the same day. The cows were fed concentrates through variable-time out-of-parlour dispensers and the number of visits made by each cow to the dispensers was automatically recorded daily and a 10-day running mean calculated. A significant increase or decrease in visits was recorded when the number of visits on one day differed from the mean number of visits during the previous 10 days by at least two standard deviations. Ninety-three increases and 40 decreases in visits occurred within +/- 10 days of the 65 confirmed oestruses. There were significantly more (16) than the expected number of increases on the day before oestrus (P less than 0.001) but at no other time. Recording increased visits to out-of-parlour concentrate dispensers may help to identify oestrus in dairy cows.

Distribution of hexoestrol residues in caponised chickens.

A radioimmunoassay method is described for the detection and measurement of residues of hexoestrol and other stilbenes in tissues of poultry. The residues following caponisation with 12 mg hexoestrol were measured in leg muscle, liver, visceral fat and neck 44 days after implantation. They were significantly greater than values obtained from eight untreated control birds. The mean values obtained in the caponised chickens ranged from 471 pg/g net weight of leg muscle to 584,500 pg/g of tissue from the upper neck region, which included the site of implantation. Control values in untreated birds fell within the range of 8 pg/g in leg muscle to 44 pg/g in liver tissue.

Plasma concentrations of ovarian hormones during the oestrous cycle of the sheep and cow.

Measurements were made of the plasma concentrations of testosterone, progesterone and oestradiol-17 beta during the oestrous cycle of the ewe, and of the plasma concentrations of testosterone and progesterone during the oestrous cycle of the heifer. The maximum concentration of progesterone in the heifer was nearly twice that in the ewe. The maximum concentration of testosterone was similar in both species and occurred at the onset of luteolysis; in the ewe the peak concentration of 19.5 ng/ml plasma was significantly greater (P less than 0.05) than the concentrations of testosterone measured during the remainder of the oestrous cycle.