Isolated mammary glands of lactating goats were perfused with heparinized and oxygenated blood for 8 to 15 h. Adequate quantities of glucose, acetate, and amino acid were added to the perfusate. After addition of propionate to the perfusion blood, concentrations of odd-numbered and of monomethyl-substituted fatty acids other than those with iso and anteiso configuration increased in the milk fat. These acids seem to be synthesized de novo in the mammary gland. The increase of C17:0 concentration was weak and problematic. We suggest that propionate is acting as a precursor for monomethyl-substituted fatty acids by way of methylmalonyl-CoA. The activating effect of propionate administration upon milk fatty acid production was largest for odd-numbered followed by monomethyl-substituted fatty acids. No increase of iso acids was observed in milk fat in the propionate-infused glands whereas the increase of anteiso acids was extremely small. This agrees with the conception that iso and anteiso fatty acids are synthesized by rumen bacteria.

SUMMARY Cross-circulation experiments were carried out using either two lactating ewes (six experiments) or one sexually mature ram and one lactating ewe (seven experiments). Under local anaesthesia an anastomosis was established by means of two plastic tubes between a jugular vein of one animal (A) and a jugular vein of the second animal (B) in each pair. The other jugular veins were clamped. Vaginal distension performed in ewe A by means of an inflated balloon often caused a sharp rise of pressure in the udder cisterns of ewe B after a minimum latency of 30 sec. Many pressure curves could be obtained successively in the same preparation by repeating the vaginal distension stimulus. Massage of the seminal vesicles and ampullae of the ram often caused a sharp pressure rise in the udder of the ewe after a minimum lag period of 30 sec. This effect could be obtained several times with the same preparation, but considerable individual variation was observed between the different rams used. Massage of the seminal vesicles and ampullae induced emission in many cases but not always. Intravenous injection of a synthetic oxytocin, Syntocinon (500–1000 mu.), in the ram or distension of the vagina in the ewe failed to elicit emission. Pressure responses were induced by injection of suitable doses of Syntocinon into the plastic tube leading to the ewe in which the cistern pressure was recorded, after a latency of approx. 30 sec. It may be concluded that vaginal distension in the ewe causes the discharge of a hormone from the head. A similar phenomenon occurs in the ram after massage of the seminal vesicles and ampullae. These effects are not abolished by atropine. It is postulated that this hormone is oxytocin in both sexes. The amount of hormone released after one stimulus was usually equivalent to 40–100 mu. oxytocin in the ram and 20–50 mu. oxytocin in the ewe.

The serum growth hormone (BGH) and free fatty acid (FFA) concentrations of large groups of calves (male and female ranging in age from 8 to 14 days and from 3 to 6 months old), bulls, oxen, heifers and cows under normal conditions were compared with the serum BGH and FFA values of corresponding large groups of animals under stress conditions. Stress was caused by transport, as it routinely occurs, and was further reinforced by a stay of several hours in unfamiliar surroundings. Stress provokes a significant increase in serum FFA in all groups and induced a significant decrease in serum BGH in all groups, with the exception of the non-pregnant heifers. The male and female calves which were 8 to 14 days old, had significantly higher BGH levels than the older animals. The female calves from 3 to 6 months of age, and the heifers had significantly lower BGH levels than the cows. The males had higher serum BGH values than the females, but a significant difference could be demonstrated only between the male and female calves of both age-groups. The oxen, which were 1 to 3 years old, had significantly higher BGH levels than the non-pregnant heifers of the same age. It appeared that gestation had no influence on the serum BGH and FFA levels of both heifers and cows.

1. The distributions of (14)C have been compared in the glucose and galactose moieties of lactose obtained from cows' udders perfused with blood containing [1-(14)C]-, [2-(14)C]- and [6-(14)C]-glucose. The (14)C of the glucose moiety was found in the same position as that of the administered glucose, but in the galactose moiety the (14)C from [2-(14)C]glucose was extensively randomized into positions 1 and 3. It is concluded that the glucose moiety arose from free glucose and the galactose moiety from hexose phosphate intermediates and that the latter reflected the randomization occurring through reactions of the pentose cycle. 2. The proportion of the glucose metabolized via the pentose cycle for those cells making lactose was estimated from the distribution of (14)C in the galactose moiety and found to be about 23% in one experiment and 30% in another experiment. 3. The yield and distribution of (14)C were determined in the glycerol of fat from the tissue in experiments with [2-(14)C]- and [6-(14)C]-glucose. There was a greater randomization of (14)C in the glycerol than in C-1, C-2 and C-3 of the galactose moiety of lactose. The ratio of the yield of (14)C in the glycerol from [2-(14)C]glucose to that of [6-(14)C]glucose was very low and from this ratio it was calculated that less than 10% of the glucose was metabolized by the Embden-Meyerhof pathway and approx. 60-70% was converted into lactose. 4. [6-(14)C]Glucose and [6-(3)H]glucose were used to determine whether the (3)H at the C-6 position remained stable during its conversion into glyceride of fat from the tissue. Twenty-seven per cent of the (3)H was labilized during this conversion. Therefore it was not possible to use [2-(14)C]glucose and [6-(3)H]glucose in a single experiment to measure the relative conversion of the C-2 and C-6 positions of glucose to glycerol.