A descriptive background is given to a group of beef farms in Jamaica on which a series of grass and animal production studies were carried out using technical and economical data derived from those farms over a 5-year period. During this time the farms co-operated in keeping standardized costaccounts and recording detailed outputs from farms and from improved and unimproved lands within those farms. Studies were made of the economics of pasture improvement and also of improvement in husbandry and breeding programmes. The possible value of the results to the small farms in the area is discussed.

1. The age of 210 days was selected for calf weight standardization. In general this is a preweaning weight under prevailing Jamaican conditions, and it represents a compromise between a very early age (90–120 days) which would reflect closely the milking ability of the dam, and the actual weaning age (approximately 260 days) when the grazing management of the herd would constitute a major unpredictable variable.

2. Either one or two weighings taken between the fourth and the ninth months of life was used to standardize calf weights to 210 days of age. In either instance for groups of calves, a mean estimate was derived which was very close to the actual mean 210-day weight, and which was suitable for data relating to groups of animals.

1. The data used in this study were the estimated 210-day weights of 2351 calves born on eight farms in the years 1958–61. In each year data were only used from herds which recorded at least five calves of each sex in that year. One hundred such herd years were included in the study.

2. The mean 210-day difference in weight between male and female calves was 27 lb. 1202 male calves had a mean weight of 380 lb. and 1149 female calves had a mean weight of 353 lb.

3. The response of calf weight to age of dam was different in the two sexes. The weight of the female calf was found to increase with dam age in a linear fashion, whereas the response of male calves was best described by a quadratic relationship with the maximum response at a dam age of 8 years.

The cost of developing and maintaining pangola grass pastures has been examined under a range of conditions. The direct cost of improving pastures to the stage where they were established as 5–10 acre, fenced, watered units of pangola grass was about £30 per acre. Under favourable conditions this cost could be reduced to £20, but with difficult land or poor techniques the cost could rise to £40 or more per acre. In addition to the direct cost of establishment there was an indirect cost due to land being out of use or stock numbers having to be reduced. This indirect cost appeared to be highest on lands where planting costs were least. It was suggested that there might be an inverse relationship between direct and indirect costs which tended to narrow the total range of establishment costs.

Yields from improved (pangola) and unimproved pastures on a group of beef cattle farms have been recorded during the years 1958–62. On these farms it was shown that there was a highly significant relationship between the percentage of improved grassland and the live-weight output per acre of the whole farm. This relationship indicated that the output of unimproved land on these farms was of the order of 45 lb. per acre, and that of improved (pangola) pasture 260 lb. per acre.

1. Moderate percentages of urea are widely and successfully used in compound fertilizers but the use of large proportions may be accompanied by two disadvantages:

(a) the loss of nitrogen as ammonia from surface applications,

(b) the occurrence of toxic effects when urea and seeds are drilled together in soil. This paper shows that both these effects are consequences of the rapid hydrolysis of urea to ammonia and carbon dioxide.

2. The effect on brairding of the presence of urea and of ammonium sulphate drilled with wheat seeds, and the loss of ammonia from top-dressings of the compounds on bare soils have been studied on a range of soils. Phytotoxicity was most pronounced in those conditions in which ammonia evolution was greatest. Thus, in a sandy soil, from which about 75% of the nitrogen of a top-dressing of urea was evolved as ammonia in our conditions, more than 15 lb. nitrogen as urea per acre reduced the braird of wheat seeds; while in a clay soil, from which only 10% of a top-dressing was lost as ammonia, up to 60 lb. nitrogen as urea per acre could be added before braird was reduced. Intermediate results were obtained with three more soils and ammonia evolution and brairding were always closely parallel.

1. Four steers were used in thirty-five experiments each lasting 4–5 days in which the effects of variation in air velocity from 0·4 to 1·6 m.p.h. at environmental temperatures of 0°, 10° and 20°C. on heat production were studied using a respiration chamber. Measurements were made on animals with winter coats and in the same animals after shearing.

2. Standing time was increased by exposure to cold and slightly reduced by exposure to wind. The wind was so small that it had no effect on the measured coat depth. Piloerection increased winter coat depth by 30%. Heat production was increased by 17–20 kcal./hr. on standing.

Grundy & Healy (1950) developed a method of ‘restricted randomization’ applicable to factorial experiments of 2n or 3n type laid out either in quasi-Latin squares of size 8 × 8 or 9 × 9, or in blocks of 8 or 9 plots. This method of randomization, while in no way affecting the validity of the normal analysis, prevents the appearance of designs with obviously undesirable features. Grundy & Healy gave an example of a quasi-Latin square inwhich the main effect of one factor corresponded to the pattern:

The number of spermatozoa in bull semen was determined by electronic counting, light scattering and absorptiometry. Electronic counting was found to be accurate, fast and reliable and seems to be the method of choice.

Determination of the light scattering was found to be the more sensitive of the indirect methods, but absorptiometry also yields consistent and reliable results. The accuracy obtained by absorptiometry was found to be independent of the sensitivity of the instrument.

Individual variation in the triple relationship of food intake, live weight and gain was examined in 40 twin calves. Appetite largely determined food intake.

Regression analyses of fortnightly gain on protein and starch equivalent and mean weight are presented. Gain per lb. of P.E. or S.E. showed real but irregular changes from fortnight to fortnight. The food differential between heavier and lighter animals decreased during adaptation to new surroundings and diets.

Records of fertility and birth weights were examined in eight breeds of goat, indigenous to, or imported into, the subtropical environment of Israel. These included the local Syrian Mountain, Negev and Damascus breeds, and the imported Malta, Appenzeller, Saanen, Fawn German and Anglo- Nubian.

All breeds of goat, local or imported, kidded at the end of winter and in early spring, and all, save the late-maturing Damascus and part of the Anglo- Nubian, kidded for the first time at the age of 1 year.

In imported breeds of goat which acclimatized well in the subtropical environment fertility was not impaired.

1. The effect of undernutrition on the levels of five enzyme activities has been observed in liver biopsy specimens taken from Suffolk-cross ewes in late pregnancy.

2. There was no significant effect on the levels of three important NADPH2-generating enzymes (i.e. glucose-6-phosphate, 6-phosphogluconate and tsocitrate dehydrogenases) when comparisons were made between groups of animals at the same stage of pregnancy. However, the proportion of very low 6-phosphogluconate dehydrogenase levels assayed in livers of the undernourished ewes was significantly increased as parturition approached.

1. The effect of undernutrition on the levels of plasma glucose, N.E.F.A. and ketone bodies was observed in fourteen Suffolk-cross ewes late in pregnancy by comparing with data obtained on seven control ewes of comparable pregnancy status. An attempt is made to relate these changes with plasma triglyceride levels, liver fat deposition and plasma pigmentation.

2. Evidence is presented which shows that while plasma glucose values are normally distributed, plasma N.E.F.A. levels show a positively skew distribution. This abnormality is corrected by transforming plasma N.E.F.A. values to their logarithms.

A comparison of eighty-eight steers and heifers, representing equal numbers of Herefords and 3/4 Hereford–1/4 Brahman cross-breds, showed that the cross-bred dressed higher (60·3 % against 58·7 %) and that the cross-bred carcasses had more flank (6·9 % against 5·6 %).

In two out of three palatability experiments, Hereford meat was more tender and, in one experiment, juicier than cross-bred meat. When breeds were compared as to colour of meat, cross-bred was judged darker. Also, heifer meat was judged darker than steer meat.

Two pairs of identical twin steers and six other adult cattle were killed, and their carcasses and tissues examined as necessary to study: (a) the muscle changes resulting from severe weight loss from starvation; (b) the reversability of such changes, as shown at various stages in recovery of the animals' weight.

Decrease in the cross-sectional area of muscle following starvation was associated with reduction in muscle fibre diameter. There was no suggestion of the complete loss of any fibres; thus, with regain of live weight, recovery both of whole-muscle dimensions and muscle fibre diameter, appeared to be complete.

1. The results are reported of three experiments in which metabolism trials were carried out with milking cows given artificial diets low in magnesium with or without supplementary magnesium.

2. In Exps. 1 and 2, the basal diets provided cither about 13 or about 9 g. of magnesium/day, that is an intake of magnesium similar to that found previously with cut-grass diets (Rook & Balch, 1958) which produced hypomagnesaemia. The ‘availability’ of the magnesium of the artificial diets was, however, of the order of 25–35 % and higher than that of cut-grass diets, and for all cows the artificial diets provided magnesium in excess of requirements, as indicated by the excretion of measurable amounts of magnesium in the urine and the maintenance of normal concentrations of magnesium in the blood serum.

It has been shown that lucerne/grass mixtures, especially those containing a high proportion of cocksfoot, can make a valuable contribution to the winter feeding of livestock when the autumn growth is allowed to stand in the field until the winter. For instance, Hughes (1954) showed that it was possible to carry store cattle right through the winter on such herbage with little supplementary feeding. Other experimental work (Barker, Hanley & Ridgman, 1955) has shown that mowing or grazing this autumn growth in September may lead to poorer production in subsequent years than October defoliation. It therefore seemed desirable to determine the effect of date of grazing in the winter on the subsequent yield of a lucerne/grass ley and two experiments for this purpose were carried out at Cambridge from 1953 to 1957.

A summary of the objectives of the present studies has been presented in a previous paper (Lazenby & Rogers, 1962): traditional methods used in the selection of improved grass varieties were reviewed together with a history of varietal assessment and some recent research developments of importance to both grass breeder and grassland agronomist. For full evaluation of selection criteria, the performance of the grass plant should be studied when the variables potentially affecting growth and development are controlled individually and in combination. Results were reported of an experiment designed to study the behaviour of one variety of Lolium perenne, S. 24, grown in different densities and under two moisture règimes. Data presented were total yield per unit area and the botanical components of such yield—number of plants, yield por plant, number and weight of sterile and fertile tillers—together with a statistical appraisal of their interrelationships (Campbell, 1962).