Growth rates of Shorthorn and Friesian heifer calves from 0 to 6 months of age were studied from live-weight data collected over a 10-year period.

Friesian calves were heavier than Shorthorn. Male calves were heavier than female. Calves born to the first pregnancy were smaller than those born to later ones. Gestation length was 5 days shorter for Friesian than for Shorthorn cows. It tended to be slightly shorter for female than for male calves. Non-foetal loss of weight at calving was greater with male than with female calves.

High-level feeding before calving was associated with heavier calves but the effect was not statistically significant.

Calf birth weight increased by 0·026 lb./lb. increase in post-calving live weight of the dam and by 0·564 lb./day extension of the gestation period.

Growth rate accelerated from birth to 3–4 months of age and then declined slightly. Autumn-born calves grew faster in the first 90 days than springborn calves. Age of dam and level of feeding before calving had no effect on rate of growth of the calf.

For both breeds there were significant negative correlations between birth weight and rate of gain in the first month after birth.

1. Early transplanting of seedlings resulted in the production of rice plants with greater total tiller and leaf number, greater total leaf area, leaf area per shoot and per leaf lamina, greater height, greater total fresh weight yield and yield of grain than late transplanting.

2. Early transplanting reduced the number of days from seeding to ear emergence.

3. Deep transplanting favoured greater leaf area per shoot and per leaf lamina and greater maximum tiller number and reduced the percentage tiller mortality.

4. Deep placement of fertilizer resulted in the production of plants with greater tiller and total leaf numbers, greater height, greater total leaf area, leaf area per shoot and per leaf lamina and greater total fresh weight and grain dry weight than surface placement.

5. Deep placement of fertilizer hastened the time of ear emergence of late transplanted seedlings.

6. The practical significance of these findings is that early transplanting of seedlings (30 days old), shallow transplanting, and deep placement of fertilizer will lead to greater yield of the rice variety BG 79.

1. A large-scale grazing management study comparing rotational grazing and continuous grazing with dairy cows at two stocking rates over four complete production seasons is described.

2. The four treatments were: (i) controlled grazing, light stocking rate; (ii) controlled grazing, heavy stocking rate; (iii) uncontrolled grazing, light stocking rate; (iv) uncontrolled grazing, heavy stocking rate.

Each treatment involved 40 cows for a first 2-year phase and 42 cows for the following 2 years. Each herd had a normal age distribution pattern and seven 2-year-old first lactation heifers (17% of total herd) were introduced each year to maintain this pattern.

3. Stocking rate was the more important factor affecting the efficiency of pasture utilization as measured by per acre output of milk and butterfat. In general, high stocking was associated with higher outputs per acre despite lower yields per animal.

4. Grazing method was of less importance. In general, controlled rotational grazing was superior to uncontrolled continuous grazing, both per animal and per acre, but the average influence even of these extremes of management was only half that of stocking rate.

5. Significant interactions between stocking rate and grazing method existed. Under continuous grazing a point was reached where production per acre declined to the vanishing point with increased stocking rate due to excessive depression of per cow yield: this point was not reached under rotational grazing at the same high stocking levels.

6. The results suggest that optimum stocking rate under rotational grazing occurs at a level some 5–10% higher than under continuous grazing. A depression of 10–12% in per cow yield, compared with more lenient grazing, corresponds with optimum stocking level irrespective of the grazing system. This estimate is suggested as a guide line in applying the principles involved.

1. A review of land restoration problems in relation to the soil depth required for successful crops showed that factual information on this orthodox method of restoration was inadequate.

2. A field trial sited on pulverized fuel ash is described in which the relationship between crop yield and soil depth at a range of fertilizer levels was determined; kale, oats, rape, barley and potatoes were the test crops.

3. The crops were divided into two groups, sensitive (kale and barley) and tolerant (oats, rape, potatoes) to ash toxicity, on the basis of their response to soil depth at the high fertilizer level. Quadratic expressions relating yield to soil depth, over the range 3–36 in. at each fertilizer level were fitted to the data for each crop group.

4. Yield isoquants, derived from the fertilizer response curves at each soil depth, enabled soil depth-fertilizer level combinations to be ascertained for producing a given level of crop yield. Fertilizer could be substituted for soil more effectively for tolerant than sensitive crops.

5. A 12 in. cover of soil together with 1½ times the normal farm fertilizer dressing for the crop was the minimum for acceptable yields. Fertilizer use may have to be increased to twice normal dressings to maintain yields if soil depths are reduced to below 12 in.

6. Crop yields were not increased by a soil covering greater than 24 in. deep.

1. An artificial diet low in magnesium (0·01–0·02% of the dry matter), and providing about 0·5 g. magnesium daily, was prepared from paper pulp, maize gluten, magnesium-free minerals and vitamins A and D and used in experimental studies with two non-lactating cows.

2. The omission of a dietary supplement of magnesium oxide (5 g./day) caused a rapid fall in the excretion of magnesium in the urine, from values of 1–2 g./day to virtually zero within about 4 days. There was a similar rapid fall in the concentration of magnesium in the serum, from about 2·7 to 2·0 mg./lOO ml., and then a slow fall to between 1·0 and 1·5 mg./lOO ml. after 12 days. Faecal excretion of magnesium was also reduced but the faecal loss continued at about 1·0 g./day after 2–3 days on the low magnesium diet.

3. The availability of the magnesium of various salts was determined by giving them as supplements to the basal diet and measuring the increase in the excretion of magnesium in the urine. The mean value was 26·2% in one cow and 34·5% in the other, a highly significant difference (P < 0·01). The availabilities of the oxide, nitrate, acetate and lactate were similar, but the citrate gave a higher value and the sulphate, silicate and, in one cow, the chloride a lower value.

1. Two cuts, the leg and the loin, were taken from the right sides of 102 pig carcasses. Their densities were determined by weighing in air and in water and the cuts were dissected into fat, muscle, bone, skin and connective tissue. Samples of the muscular and fatty tissues were taken to obtain a measure of the analytically determined fat content. The weights of each tissue were expressed as a percentage of the weight of each cut and related to density by the methods of correlation and regression. Correlation coefficients and regression equations were calculated separately for legs, loins and the composite leg plus loin for each pig and for legs and loins rogarded as 204 separate pieces of pig carcass.

2. Correlations and regressions were used to relate the composition of the loin cut to three measurements of backfat thickness taken over the eye muscle at the level of the last rib, and to eye muscle area. These allowed a comparison of density and backfat thickness as measures of the fat and lean content of the loin cuts.

3. There was evidence of a high degree of association between the fat or muscle contents of the cuts and the density or the reciprocal of density. In no case was the simple correlation coefficient between muscle and density or fat and density less than 0·84. The greatest standard error of estimate of any of the regressions of porcentage fat or percentage muscle on density was 3·3% fat, for the regression of percentage separable fat on the reciprocal of the density of the loin cuts. Density was found to be a better measure of the muscle or fat content of the loin cuts than eye muscle area or any of 3 measurements of backfat thickness taken over the eye muscle.

4. Dissection data from 25 whole sides supported these results showing a high correlation between density and percentage fat or percentage muscle.

5. There was a low correlation, r = 0·41, between percentage bone and density of 102 leg cuts. That between density and percentage bone of 25 whole sides was r = 0·47; suggesting that bone content has but a small influence on carcass density.

6. It is suggested that carcass density is a better measure of carcass fatness or leanness than measurements of backfat thickness or eye muscle area.

A long-term experiment designed to study the effects on crop yields of different basic methods of cultivation used in the preparation of seedbeds is described and the results of the first completed cycle of 4 years are discussed. Four basic methods of cultivation were compared, namely, ploughing, rotary cultivating, cultivating and discing. Each one of these was done, early and late, for each crop in two four-course rotations which differed only in the cropping of 1 of the 4 years when potatoes were used in one case and a 1-year ley in the other. Each crop in the rotation (winter wheat, sugar beet, barley, ley or potatoes) was grown at two levels of fertilizer application and provision was made in the design of the experiment for two different weed control régimes. The soil was fairly easy to work, being of the Milton series of river gravels.

As a result of the work described, the following conclusions have been drawn:

1. Ploughing was the most consistent method of providing a satisfactory basis for the final seedbed preparation but in some circumstances other methods were equally good. On average, ploughing led to the highest yields and discing the lowest, with rotary cultivating second and cultivating third in order of merit.

2. The yields of cereals grown after root crops were not dependent on the method of basic cultivation used.

3. The effects of the cultivations on the yield of winter wheat after the ley appeared to be due to the extent to which the regrowth of rye-grass was controlled, the plough being most effective in this respect.

1. The problems involved in conservation of fodder in Northern Rhodesia are discussed in relation to climate and present day practices. Special reference is made to the conservation of grassland herbage.

Climatic conditions do not appear suitable for haymaking.

2. A number of silage samples were collected from dairy farms in the territory and from Mount Makulu Research Station. Chemical analyses of these samples are given and their nutritional value is discussed with special reference to their crude protein contents. The majority of the silages were found to have low crude protein.

3. A type of miniature tower silo designed for experimental work is described.

4. Three crops commonly used for ensilage, i.e. maize, maize with legume and Napier grass, were compared with giant Rhodes grass (Chloris gayana Kunth.) when ensiled in these miniature silos. The type of fermentation and loss of nutrients was studied. Rhodes grass ensiled at the early flowering stage was found to compare favourably with the other three. Napier grass (Pennisetum purpurem) cut when over 6 ft. high did not ensile well and had a low crude-protein content.

5. Giant Rhodes grass was ensiled in miniature experimental silos at two different stages of growth. Cutting the grass at a height of 20 in., three times during the season, resulted in a higher yield of dry matter and crude protein per acre than cutting once at a height of 40 in. even when the resultant aftermath growth was included.

An experiment is described in which four pairs of individually fed identical twin calves were used to investigate the effects of castration at 1 and 7 months, on growth, efficiency of food utilization and carcass composition and conformation.

The results indicate that up to 28 weeks of age the late-castrated animals wore superior in liveweight increase, width of head and efficiency with which they converted food to live weight. By slaughter time, at about 18 months, these differences, except width of head, had been eliminated.

The carcasses from both treatments were very similar except that a slightly greater percentage of the total muscle occurred in the thoracic and abdominal muscles of the late-castrated animals than in the early-castrated ones. A statistically significant higher percentage of the total fat occurred as subcutaneous fat in the late-castrated animals than in the early-castrated ones.

For three years the persistence of six grasses and one herb sown singly or in combination under poultry grazing was studied. Established swards were regularly mown and either not grazed (control) or grazed every other week or every other month. The results are compared with those from earlier trials and reasons for the differences are discussed. Red fescue, perennial rye-grass and smooth-stalked meadow grass increased in amount, red fescue being particularly unpopular with poultry. Meadow fescue and timothy were slightly, and cocksfoot and yarrow drastically, reduced under poultry grazing.

The preferences of poultry for certain herbage species and varieties are discussed but no reasons adduced owing to lack of data.

One week's and 4 weeks' grazing made no difference to the persistence and palatability of the grasses tested, but these were always in a short leafy condition when grazed.

1. Observations were made during the autumn and spring of 1959–60, 1960–61, and 1961–62 on pregnant and lactating Clun ewes of mixed ages grazing under natural conditions. The pattern of food intake during pregnancy and lactation, the output achieved in the form of weight of lambs produced at parturition, milk yield, and bodyweight change of the ewes themselves was investigated. The interrelationships between these factors, as influenced by the feeding of supplementary concentrate, either for 7 weeks before or 7 weeks after lambing, or during both periods, was elucidated.

2. Daily dry-matter intake was found to be of the order of 1·5–2·0 kg. for this type of ewe, but there was considerable individual variation (coefficient of variation about 20%). Intake did not increase concurrently with the demands of the foetus during the later stages of pregnancy, and even became depressed as parturition approached. Immediately after lambing there was a spectacular increase in intake, which, after rising to a peak, was maintained at a high level during the lactation. Ewes receiving supplementary concentrates showed an increase in food intake over those unsupplemented, but this increase was less than the amount of dry matter fed in the supplement, even on rather bare pasture.

3. During the early stages of pregnancy there was no apparent difference in the weight gains of singleand twin-bearing ewes, but during the last 8 weeks prior to lambing twin-bearing ewes made greater weight gains. In relation to weights taken just after parturition ewes producing twins had lost most weight. Unsupplemented ewes lost more weight than those receiving supplements. Lack of supplementation prior to lambing only limited production in the case of twin-bearing ewes.

1. Two trials are described in which the live weights of sheep grazing four different pastures were compared. The four pastures comprised perennial rye-grass (P), perennial rye-grass plus white clover (P + C), short-rotation rye-grass (S), short-rotation rye-grass plus white clover (S + C).

2. Large and highly significant differences existed between the mean live weight of the sheep on the various pastures in each trial. Thus the P sheep had a mean live weight of 107 and 102 lb. in trials I and II, respectively, at the end of each investigation, the P + C sheep 123 and 122 lb., the S sheep 125 and 126 lb., and the S + C sheep 140 and 137 lb.

3. The differences in live-weight growth on the four pastures contain two major effects; an effect due to the difference between P and S and an effect which can be attributed to the presence of white clover in the pasture treatment.

Data from thirty-five digestibility trials with sheep in metabolism cages were used to investigate statistically the relationships between organic matter intake (I), faecal organic matter output (F), and the nitrogen concentration in faecal organic matter (N).

The data fell easily into groups due to botanical or seasonal differences in the feed. These groups of data were homogeneous and provided highly significant linear equations of the forms I = bF + cFN and I = a + cFN. When compared these groups of data sometimes showed differences in slope, position or both. A quadratic expression

I = bF + cFN + dFN2

was found to accommodate a majority of the data but to be less precise than I = a + cFN.

A further expression incorporating N as an independent variable was also examined,

I = a + cFN2 + eN.

This expression, although far from being universally adequate, proved to be generally better than existing formulae. When applied to the data of Greenhalgh et. al. (1960), it substantially reduced heterogeneity between data for spring and data for summer pastures.

Causes of variation in the relationship between organic-matter intake and nitrogen in faeces, and some of the hazards of extrapolation from empirical regression relations, are discussed.

1. The results of two trials with Romney ewes grazed on perennial rye-grass (P), perennial rye-grass with white clover (P + C), short-rotation rye-grass (S) and short-rotation rye-grass with white clover (S + C) are reported. Chemical and dissection analyses of their carcasses were made and the weights of certain internal organs were obtained.

2. It was found that the sheep grazed on the P plots had the lightest carcasses (56·2 and 40·9 lb. in trials I and II, respectively), followed by those on the P + C (70·2 and 59·2 lb.), by those on S (74·7 and 61·2 lb.) and the heaviest carcasses were yielded by sheep from the S + C plots (81·5 and 69·1 lb., respectively).

3. The weights of dissectible fatty tissue and chemical fat of the carcasses were related to the carcass weights of the different groups of sheep; the group with the lightest carcass weight had the least fat. The other components of the carcass (protein, water and ash) followed the order for group mean carcass weights except that the S carcasses in trial II had slightly less water, protein and ash than the P + C carcasses. The percentage chemical fat of the S carcasses in trial I was also lower than the P + C carcasses.

4. In general, the non-carcass components of live weight (head, feet, skin, liver, mesenteric fat, omental fat, kidneys, stomach empty, and intestines empty) all followed the same pattern of increasing weight (P < P + C < S < S + C).

1. A study was made of the effects of feeding regimen and the composition of the diet on the ruminal production of V.f.a.'S in cattle.

2. The day-to-day variations in the pattern of rumen fermentation in cows given a diet of hay and concentrates indicated that within-cow differences in the molar proportions of the acids from diet to diet are of significance if they exceed about 3% (of the mean value) for acetic acid, about 10% for propionic and butyric acids, and about 25% for valeric acid. The results emphasized also the important differences to be found between cows given the same diet.

3. A change in the frequency of feeding from once to four times daily at a constant daily drymatter intake had little effect on the daily mean values for pH, concentration of total V.f.a.'S, or the molar percentages of the individual acids, but almost invariably decreased the range of values observed between feeding.

4. With diets of hay and of hay and concentrates an increase in daily dry-matter intake was associated with a fall in pH and an increase in the concentration of total V.f.a.'S; with the diet of hay and concentrates there was a considerable decrease in the molar percentage of acetic acid and a corresponding increase in N-butyric, but there was little change in the molar percentages of the acids with the diet of hay.

1. The mean thyroid weights of ewes grazed on the different pastures (perennial rye-grass (P), perennial rye-grass plus white clover (P + C), short-rotation rye-grass (S), short-rotation rye-grass plus white clover (S + C)) did not differ significantly, but those injected with iodinated poppy-seed oil had lighter (P < 0·01) thyroids than the non-injected ewes grazed on the same pastures.

2. Neither the live weights of the ewes nor their lambing performances were affected significantly by treatment with iodine.

3. Lambs from ewes grazed on pastures containing white clover had thyroid glands significantly heavier than those of ewes grazed on rye-grass pastures. The largest thyroids were from the lambs of ewes not treated with iodine and grazed on S.

4. The iodine contents of the thyroids of the lambs at slaughter, measured as percentage dry weight, did not differ significantly. It seems likely that the differences in thyroid weights were caused by factors operating early in the lives of the lambs.

5. The lambs of ewes injected with iodine grew faster after weaning than those of non-injected ewes on the same pastures. The interpretation that this difference was in fact caused by the iodine treatment of the ewes was not wholly acceptable, because the differences in growth rate were not greatest in those groups of lambs showing greatest differences in thyroid weight.

1. Soil samples were incubated at 60% W.h.c. at 20° C. and leached after 8 and 20 weeks. On subsequent incubation, the rate of nitrate production in the leached samples was greater than that in unleached control soils. The increase in nitrate production seems to be due to an increased rate of ammonification.

2. Adding 100 p.p.m. of nitrate nitrogen to the soil before incubating had no effect on mineralization.

3. Adding a leachate of incubated soil to new soil samples reduced the rate of mineralization on incubation. This reduction is not due to nitrate or any other anion, since deionized leachate was equally effective.

The relative importance of variation in the components of wool production to variation in wool production itself was estimated by two methods of analysis. About 30% of the attributable variation in total fleece weight was found to be due to variation in surface area and 70% was due to wool production per unit skin area. Between 50 and 60% of the variation amongst sheep in the latter character was found to be due to variation in fibre weight, the rest being attributed to variation in number of fibres per unit area (fibre density). The variation in mean fibre weight was further partitioned into 50 to 70% due to variation in mean cross-sectional area and the remainder to variation in mean fibre length.

Variation in wool production per unit skin area was also analysed according to growth period and position on the body. The results are discussed in relation to the partition of variance in wool production of other breeds.

For highest revival rates in experiments on the deep-freezing of bull spermatozoa to – 79° C., a period of incubation of the undiluted semen at 30° C. did not eliminate the need for overnight equilibration at 5° C. The addition of 1·25% fructose or arabinose to the diluent improved revival rates of non-equilibrated spermatozoa but these rates still did not equal those of equilibrated spermatozoa.

Glycerol apparently penetrated spermatozoa rapidly and spermatozoa survived in glycerol solutions as high as 2·0m if 0·1m buffered citrate was also present. Omission of the citrate solutions caused immediate death of the spermatozoa.

A one-ninth replication of a 37 factorial experiment showed that, by all scoring criteria, 40° C. was superior to 0° C. as a thawing bath temperature. A diluent containing 8% (v/v) glycerol was superior to either 4% or 6% if activity of spermatozoa after thawing was the scoring criterion, but there was no difference in the percentage of spermatozoa stained by congo-red-nigrosin when frozen in diluents containing these levels of glycerol.

In the range of tonicity 80, 100 and 120% (0·9% NaCl = 100% tonicity), using the diluent composed of a mixture of fructose and citrate, there were more motile spermatozoa than in buffered citrate or fructose alone. Increasing tonicity had an adverse effect on revival rates of spermatozoa in the buffered citrate diluent. Spermatozoa stored chilled at 5· C. for periods up to 36 hr. prior to freezing survived best in the mixture of fructose and citrate.

The investigation of the equilibration phenomenon showed that an improvement in survival after deep-freezing occurred if diluted semen was stored for up to 12 hr. after dilution, but this was not dependent on the presence of glycerol in the diluent during this ageing process.

1. The effect of applications of liquid manure during the winter months was studied and compared with the application of dry artificial fertilizers on six different swards in two experiments in each of the years 1960, 1961 and 1962.

2. The liquid manure supplied an average of 69 lb. N and 114 lb. K/acre at each application and plots received one dressing only applied in November, December, January, February or March. Further treatments consisted of applying conventional dry fertilizer supplying the same weight of nitrogen and potassium as the liquid manure and applied on the same day. A control plot received no added fertilizer or liquid manure.

3. All plots were cut in May and a second cut was made 8–10 weeks later to measure residual effects of treatments.

4. The maximum increase in dry-matter yields at cut 1 occurred with the February application although the January and March applications gave only slightly lower yields. The dry-matter yield/lb of N applied even from some November applications was comparable to the response obtained from applications of inorganic nitrogen made in summer in earlier experiments by other workers.

5. The production of crude-protein followed a similar pattern to that of the dry-matter, and the maximum increase was from the March application.

6. With similar rainfall conditions but different winter soil temperatures a mixture of Italian and perennial rye-grasses under average fertility conditions gave the highest response to liquid manure. This was followed by the later growing cocksfoot sward and the permanent pasture, on both of which yields were increased by all the monthly applications. The two swards containing grass and clover mixtures showed a response to the later dressings whereas a vigorous Italian rye-grass ley in the mild winter of 1961 was unaffected by treatment.