Effects of female sex hormones on uterine motility and reactivity to oxytocin in goats.

Uterine motility was recorded for several weeks in 10 ovariectomised goats, using small intra-uterine balloons, to study the effects of female sex hormones on uterine activity and reactivity to oxytocin. Oestradiol stimulated uterine contractions and increased both the sensitivity and intra-uterine pressure response to oxytocin. When progesterone was administered in addition to oestradiol, spontaneous uterine motility became irregular with low amplitude contrations; the sensitivity and reactivity to oxytocin was significantly depressed.     

Relationships of concentrations of certain blood constituents with milk yield and age of cows in dairy herds.

Regression analyses were performed on data from 48 Compton metabolic profile tests relating the concentrations of certain constituents in the blood of dairy cows to their milk yield, age and stage of lactation. The common partial regression coefficients for milk yield, age and stage of lactation were estimated for each blood constituent. The relationships of greatest statistical significance were between the concentrations of inorganic phosphate and globulin and age, and the concentration of albumin and milk yield.     

A comparison of the effects of two low‐calcium diets on egg production in the domestic fowl

1. Hens fed on a diet containing 0–05% calcium virtually ceased egg laying (production <4%) whereas those fed on a diet containing 0–5% Ca maintained production at between 20 and 30%.

2. After a return to a normal diet (3% Ca) egg weight, shell weight, ovarian characteristics and oviduct size were of a similar nature in the two groups, though the differences in egg weight, shell weight and shell calcium were significant at the 1 % level.

3. Bone weight and bone ash did not differ significantly between the groups but after a return to normal rations, bone weight and bone ash became higher in the group that had received the 0.05% Ca diet.

4. There were no clinical signs of bone demineralisation during the experiments.     

A study of the mechanical properties of egg shell

1. The mechanical behaviour of the egg shell of the domestic fowl was investigated by cutting strips from the shell and testing the flection either in a four‐point load test or in a cantilever beam test.

2. It was found that moisture content, temperature and load rate have important effects on shell properties ; both the strength and stiffness of the shell are greater in snapping‐inward tests than in snapping‐outward tests; residual stress exists in the egg shell; the correlation between failure moment and shell thickness was highly significant, on average about 0.9, and was dependent on the spread in the thickness data.

3. Estimates were made of the ultimate strength and Young's modulus of egg shell material and it is concluded that a substantial size effect exists in the egg shell.