1. The rectal temperatures of three 4-month-old Ayrshire bull calves were measured in individual 6 hr. daily exposures to 15, 20, 25, 30, 35 and 40° C. dry-bulb temperature at low humidity (17 mg./l. absolute humidity) and to 30, 35 and 40° C. at high humidity (7 mg./l. saturation deficit). The experiments on each animal lasted 45 consecutive days and consisted of five replications of these nine environmental conditions. Measurements of rectal temperature were made every 5 min.

2. The rectal temperatures of the animals rose with increasing environmental temperature and humidity.

1. Four trials on methods of bloat-prevention vare described: (a) A comparison of ‘break’ grazing and normal ‘rotational’ grazing without restriction of feed in either case. Break grazing observations covered two and five breaks per day.

(b) A comparison of these two systems where ‘break’ grazing involved restriction of area available to the cows, and ‘breaks’ varied from seven to eleven per day.

(c) Comparison of ‘off and on’ grazing with normal rotational methods in an attempt to force changes in grazing pattern.

(d) Comparison of the same pasture grazed at different lengths under rotational grazing methods.

2. Grazing behaviour and degree of bloat were noted.

3. In general, the results showed that, irrespective of number of breaks, break grazing with or without restriction gave no effective control of bloat.

4. There were definite indications that a strictly enforced system of ‘off and on’ grazing could afford considerable practical control.

5. Long feed proved definitely safer than feed of the same botanical composition grazed at shorter stages of growth.

6. It was found that cows on potentially dangerous grass had short grazing times with few periods of intense activity. Thus, the oft-stated opinion that bloat is caused by cows eating greedily of dangerous pastures was not substantiated. On the contrary, cows on such pasture showed marked reluctance in their grazing activity.

7. Bloat-producing swards were also associated with reduced rumination time, even in respect to cows showing no symptoms. Bloated cows showed generally very low rumination times.

8. Many of these observations were made on identical twins. From the similarity in their behaviour, it can be concluded that inheritance is an important factor affecting the occurrence of bloat amongst cows grazing the same herbage.

9. In the early stages of bloat, ruminal movement and belching increased in frequency and intensity. This is contrary to the theory that bloat is due to rumen atony. Atony was observed only in the advanced stages of the trouble.

Fourteen pairs of monozygous twin cows of mixed ages were used to determine the effect of underfeeding from the 3rd to the 8th week inclusive after calving on milk and butterfat production and on the composition of the milk.

Those cows which were well fed over the 6-week period produced more milk and a larger weight of butterfat than their sisters which had been poorly fed. The milk from the well-fed cows had a lower percentage of butterfat, but higher percentages of solids-not-fat and total protein, than the milk from the poorly fed cows.

The complete lactation averages failed to show statistical significant differences in all characteristics except in the case of solids-not-fat percentage. The mean difference between the two groups for solidsnot-fat was found to be highly significant.

In general, the results support the conclusions of other workers, that underfeeding dairy cows may depress the solids-not-fat content of the milk.

It appeared that differences between the two groups in butterfat percentage over the 6-week experimental feeding period were strongly correlated with differences in weight changes and that the small amount of variance associated with milk yield differences was not significant.

1. The skin temperatures at each of eight positions on the trunks of three 4-month-old Ayrshire bull calves were measured at 5 min. intervals in individual 6 hr. daily exposures to dry-bulb temperatures of 15, 20, 25, 30, 35 and 40° C. at 17 mg./l. absolute humidity, and 30, 35 and 40° C. at 7 mg./l. saturation deficit in a modified form of Latin square arrangement of environmental temperature. The schedule of experiments on each calf lasted 45 consecutive days and consisted of five replications of each of the nine environmental conditions.

2. The skin temperatures of the calves all rose with increasing environmental temperature, humidity and time of exposure.

In 1939, Pinous & Waddington reported tetraploid early cleavage stages of the rabbit after colchicine treatment of fertilized eggs in vitro. Chang (1944) inseminated rabbit does with sperm suspended in 1/1000 colchicine in 0·9% NaCl and noted a few abnormal young in the resulting litters. No chromosome counts were made, but Chang considered the possibility that colchicine had entered the egg and caused polyploidy. Using the same technique as Chang, Swedish workers have claimed the production of two adult triploid rabbits and one adult triploid pig (Häggqvist & Bane, 1950a, b, c, 1951; Melander, 1950, 1951). This Swedish work has been criticized (Beatty, 1951; Beatty & Fischberg, 1950; Becker, 1952–3; Hertwig, 1951; Nachtsheim, 1950; Rostand, 1951; Venge, 1953). Nevertheless, the technique is ingenious and the claim of great interest. The present note records preliminary attempts to extend the technique to cattle and to confirm the results in rabbits.

1. A series of observations on the grazing behaviour of identical twin cattle on two contrasting systems of pasture management—rotationally and continuously grazed—is described.

2. The rotationally grazed cows averaged only 11 min. (day/cow) shorter feeding time and 18 min. shorter ruminating time than their continuously grazed co-twins. The total time they spent in work was thus 29 min. shorter.

3. While the average differences in total work over the whole trial was not great, the continuously grazed cows worked for appreciably longer daily periods at the time of seasonal feed shortage during which time the rotationally grazed cows were buffered by their pasture diet being supplemented with silage.

4. The differences in grazing behaviour between the cows of the two treatments, together with the magnitude of the seasonal variations which occurred in both groups, indicated that dairy cows attempt to maintain a stable production in the face of adverse pasture conditions by increasing their feeding time.

5. Previous conclusions based on observations of uniformly treated twins regarding the importance of heredity in the determination of grazing behaviour were fully confirmed.

1. The temperature of the surface of the scrota of three 4-month-old Ayrshire calves has been measured in environments of 15, 20, 25, 30, 35 and 40° C. at a low humidity of 17 mg./l. absolute humidity and in environments of 30, 35 and 40° C. at a high humidity of 7 mg./l. saturation deficit. Five replicate experiments were performed at each environment on each animal and the animals were exposed to each environment for 6 hr.; measurements of scrotal temperature were made once every 5 min.

2. The scrotal surface temperature increased with increasing environmental temperature ranging from 32° C. at 15° C. to 39° C. at 40° C. The rates of increase in scrotal surface temperature with environmental temperature were curvilinear for two of the animals and rectilinear for the other. For the two whose rates of increase were curvilinear the rate of increase was constant at 0·2° C./° C. environmental temperature in the range 15–25° C.

1. The necessity for further information on the digestibility of heather, with particular reference to the effect of age, has been discussed.

2. The digestibility of well-defined samples of heather of 4 and 10 years of age has been determined.

3. Four-year-old Blackface wethers in crates were fed diets containing 50% of heather and 50% of medium-quality meadow hay.

4. The younger sample of heather was found to have appreciably higher digestibility coefficients for all nutritive constituents other than crude fibre.

5. Agreement between duplicate sheep in respect of their capacity to digest crude protein was found to be good, and faecal metabolic nitrogen outputs were similar.

6. Faecal metabolic nitrogen output was inversely related to the percentage of heather contained in the diet. No relationship between faecal metabolic nitrogen and bulk, as measured on a basis of volume per unit weight, could be established.

7. It has been concluded that heather, though inferior as a source of protein, provides rather more energy than a poor-quality meadow hay, and is thus of value as a winter feed.

1. The surface temperature of the right and left ears of 4-month-old Ayrshire bull calves subjected to temperatures of 15, 20, 25, 30, 35 and 40° C. at a low humidity of 17 mg./l. absolute humidity and to 30, 35 and 40° C. at a high humidity of 7 mg./l. saturation deficit, have been measured in a climatic room.

2. From 20 to 40° C. at both humidities, but excluding 40° C. at high humidity, the ear-surface temperatures behaved exactly as did the mean surface temperature of the trunk as expressed in the relation

1. 101 Rhode Island Red × Light Sussex chickens have been made to conform to four major changes in the shape of their growth curves from hatching to twenty-four weeks, by control of their plane of nutrition. The four treatments (HH), (LH), (HL) and (LL), allowed comparisons to be made between birds of the same age, but different weights. As the main concern has been to find the essential nature rather than the precise extent of the effects produced by different planes of nutrition, the treatment differences were made as extreme as possible without allowing the rations to become unbalanced.

2. Certain individual organs and tissues, the gonads, thyroid and thymus, and the combs and wattles have reacted differentially to the contrasted treatments when compared on a basis of equal body weight. All the organs, with the exception of the very early maturing eyes and heart, have reached significantly different weights on the basis of equal age. Those organs which have yielded treatment differences judged on both the basis of equal weight or equal age have all been late maturing. The results therefore indicate that the effect of treatment has been to restrict the development of the later maturing parts in the case of the low-plane birds, and to accelerate the development of these organs when the birds are reared on the high plane. The results are insensitive to any differential effects which may have been brought about in the early maturing organs, since the design of the experiment did not allow of the slaughtering of birds at equal weight but only at equal age. The means of Comparison of differences at equal weights was the less precise method of ascertaining whether the high- and low-plane regression lines of weight of part to total weight of bird differed significantly the one from the other.

1. The two spring oat varieties, Argentine and Victory, and the two winter varieties, Grey Winter and Black Winter, have 0.10, 0.07, 1.57 and 0.41% pollen mother cells with irregular meioses respectively.

2. F1Victory x Argentine had 3.43% of irregular meioses, and F1. Grey Winter x Black Winter 1.58%.

1. Wheats from manurial trials, whose nitrogen contents differed by reason of the fertilizer treatment applied, have been used as the sole source of protein in rat-feeding experiments.

2. Pairs of rats given such diets have shown increased growth when fed wheat of higher nitrogen content.

3. Measurement of the ratio of growth rate to nitrogen ingested, suggests that the difference obtained is due, not to increase in the acceptability of the diet, but to the greater nutritive value of the grain from the manurial plots.