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1. Observations were made on the behaviour of young spring- and autumn-bom calves reared at pasture.2. Bucket-fed calves rapidly learnt to graze, whereas single-suckled animals running with their dams made no serious attempt to graze until they were 6 weeks old.3. The time spent in grazing was modified by the presence of hay and probably by that of concentrates, and it was influenced also by the quality and quantity of herbage on offer.

The treatments in this summer-grazing experiment were designed as a 3 x 3 factorial; 3 levels of nitrogenous fertilizer, supplying 0, 336 and 672 kg N/ha per annum, and 3 stocking rates. The fertilizer was applied in 6 to 8 dressings at intervals of 3 to 4 weeks. The animals used were fattening Hereford x Friesian steers. The stocking rates were calculated on the basis of data available on herbage production under N and irrigation treatments and varied according to the level of N input. The experiment was laid out in 6 randomized blocks, which were grazed in rotation. Blocks were removed from the grazing cycle in spring and early summer of each of the 3 years (1962-4) over which the experiment was conducted and cut for conservation; yields were recorded. Details are given of: grazing management; results of studies of soil-N levels; the quantities of herbage removed for conservation; the quantity, chemical and botanical composition of the herbage available for grazing; and herbage consumption.

In a 3 X 3 factorial experiment, the effects of three levels of nitrogenous fertilizer (0, 336 and 672 kg/N per ha) and three grazing intensities on live-weight gains and carcass attributes were measured. The live-weight gains of the animals (per head) over the season were greater at the low and moderate grazing intensities than at the high; this effect occurred mainly from July to October each year. Gains were low on the no-nitrogen swards from July 1962 to the end of the grazing season and throughout 1963: this was related to the very high clover content of the swards. In all years, as grazing intensities increased, the carcass weights per animal became lower. Carcass balance, carcass length, depth of longissimus dorsi muscle, fat thickness over the longissimus dorsi, weight of kidney suet and channel fat, and weight of the alimentary tract also reflected the effect of treatment on weight gains. The results are discussed in relation to the botanical composition and consumption of the herbage, presented in Part I.

The treatments in this summer-grazing experiment were designed as a 2 x 3 factorial, there being two levels of nitrogenous fertilizer (nitro-chalk), supplying 0 and 336 kg of N/ha per annum (NO and N3, respectively) and three stocking rates. The fertilizer was applied in 7 dressings at approximately three-weekly intervals. The animals used were Hereford x Friesian steers; these were slaughtered at the end of the grazing season. The stocking rates were calculated on the basis of expected herbage production. The experiment was laid out in 6 randomized blocks which were grazed in rotation. Two blocks were cut for conservation before grazing each year; up to the end of June only 4 blocks were used for grazing. There was little contamination of the swards with unsown species. With the NO swards the clover contents declined each year, but remained fairly high at over 20% in 1965. Clover contents also declined each year in the N3 swards and by 1965 were only 2 to 4%. The quantities of herbage cut for conservation were higher from the swards receiving N. The live-weight gains of the cattle (per head) were higher at the lower stocking rates, the effect of stocking rate being more noticeable in the July to Oct. period. Live-weight gains per ha increased at the higher stocking rates. In 1963 and 1965, as stocking rates increased carcass weights per animal decreased and carcass quality, as indicated by the commercial grades, was poorer. In 1964, a dry spell from July to Oct. necessitated the removal of cattle from the experiment and the effects of treatment on carcass weight and quality were not apparent.

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B ETWEEN 1938 and 1949 seven different unrelated inbred lines of Duroc swine were developed by the Oklahoma Agricultural Experiment Station in cooperation with the Regional Swine Breeding Laboratory. In sixteen of the twenty-two farrowing seasons from the spring of 1939 through the fall of 1949, both inbred and two-line-cross litters were produced. In some seasons outbred Duroc and three-linecross litters were farrowed.The purpose of the present study was to determine if selection within moderately inbred Duroc lines followed by crossing of these lines resulted in improved performance. If so, its manner of expression and the time at which it was first evident were to be investigated.