1. The effect of four different planes of nutrition of lambs until they reach 30 1b. dressed carcass weight on the development of the form of the ribs is studied.

2. The growth in length of the ribs is found to be more influenced by age and less by the plane of nutrition than their growth in thickness, and is not reflected in the weight of the ribs.

To obtain large yields of grass much N fertilizer is usually needed, and when such grass is cut and conserved large amounts of K soon are removed from the soil. Some soils contain so little ‘available’ K that yields are soon limited unless grass is given enough K fertilizer, but other soils supply more K and so need less K fertilizer. Soils differ so greatly in their ability to supply crops with K that it is difficult to generalize about the fertilizer K requirements of grass, especially as the use to which the grass is put greatly affects the soil K ‘balance sheet’. On average, grass in England grows well for not much more than 6 months each year. This implies that, when cattle are maintained on hay or silage for much of the remainder of the year, on average one-third of the grass product each year may have to be cut, removed from the field, and conserved. Much of the N, P and K contained in this grass is not returned to the soil.

1. The levels of blood reducing sugars, haemoglobin, protein N, NPN, ammonia N, and urea N in addition to the nitrogen retention and digestibility coefficients of food constituents, were studied in lambs with and without ciliate protozoa.

2. The inoculated lambs have higher blood haemoglobin, protein N, and lower reducing sugars, ammonia N, and urea N values than those of the uninoculated lambs.

Fourteen experiments were carried out in various parts of England to compare ammoniumsulphate, ammonium nitrate, calcium nitrate andurea applied to grassland in early winter, latewinter and spring at rates supplying 40 and 80lb./acre of nitrogen. Yield of herbage and of nitrogen were recorded at one cut in spring..

1. Africander and Mashona steers, fitted with rumen cannulae, were used to study levels of various nitrogenous fractions and of dry matter in the rumen of cattle grazing on natural subtropical herbage throughout the year. Some steers received various concentrate foods in addition to veldt grazing during winter. During the summer rainy season, four steers, two of each breed, were under trial, while in the winter drought period two extra steers of each breed were added to the experiment. The eight steers were divided into four groups for the winter, one group received a protein-rich concentrate, another group received a carbohydraterich concentrate, a third group was given a mixture of the two concentrates, while the fourth group received no additional food.

1. Africander and Mashona steers, fitted with rumen cannulae, were used to study pH values and concentrations of volatile fatty acids in the rumen of cattle grazing on natural subtropical pasture through the year. Some steers received concentrated, foods in winter. During the summer, rainy season, two Africander and two Mashona steers were studied while in winter a further four steers, two of each breed, were added to the trial. The eight steers in winter were divided into four similar groups, one group received a carbohydrate-rich concentrate, another group received a protein-rich concentrate, a third group was given both concentrates, while the fourth group received no additional food.

The effects of rotational grazing (twice weekly pasture change) and two systems of set-stocking on plasma calcium and magnesium levels of lactating ewes have been studied.

In a replicated trial the high resistance to bacterial blight of the Allen derivatives Reba W296 and Albar strains was confirmed. Only one major gene, Lagière's B9, was detected in Reba W 296. The very high resistance of this variety is due to B9 fortified by genes of small effect.

The key to resistance in Albar derivatives is the major gene B2: the presence of B3 awaits confirmation. It was found that Albar 49, maintained in Uganda, had deteriorated in resistance to leaf infection in the Sudan. Possible reasons for this change are discussed. All Albar derivatives selected in East Africa for stem and boll resistance were found to be variable for leaf resistance under Sudan conditions.

The authors of most of the papers dealing with the seasonal breeding of sheep agree that the summer months are the less favourable season for sexual desire of the rams (Moule, 1960), their semen quality (McKenzie & Berliner, 1937; Gunn, Sanders & Granger, 1942; Comstock, Green, Winters & Nordskog, 1943; Phillips, Sohott, Eaton & Simmons, 1943; Sapsford, 1951; Hafez, Badreldin & Darwish, 1955; Cupps et al. 1960; and many others), and for spermatogenesis (Maqsood, 1951; Ortavant & Thibault, 1956).

1. Blood plasma of normal fed sheep is not pigmented but on starvation the plasma assumes a yellow to green colour. Unlike the pigments of the so-called yellow fatted sheep, the pigmentation disappears on refeeding.

2. Using spectrophotometric and chromatographic methods, this pigment has been identified as xanthophyll (lutein).

3. The xanthophyll content of plasma is related to the plasma non-esterified fatty acid (N.E.F.A.) concentration and it therefore appears that the pigment is mobilized from the fat depots together with the free fatty acids. Maximum levels of about 60μg./100 ml. xanthophyll are observed in sheep plasma after 4 days starvation.

A plot trial tested the fertilizer value of dung and urine evenly spread on Hyparrhenia veld which was very deficient in N and was also deficient, although less seriously, in P.

Semen characteristics of local and imported rams were studied over a period of 2 years.

Awassi and Border-Leicester rams with regular Awassi and Border-Leicester rams with regular semen collections throughout the year showed definite seasonal variations in the volume and number of sperms in their ejaculates: maximum levels during the autumn and minimum during the spring months. The sperm density reached its maximum during the spring and its minimum during the autumn as a result of the opposite changes of the semen volume. In the rams without regular semen collections, as those kept in the flock, these seasonal changes were not distinct. In the imported rams from breeds without a

1. Fifteen male Merino lambs suckling the ewe and four adult Merino wethers were fed the same pelletted diet. The lambs had free access to milk from the ewe and were creep-fed the pelletted diet. Feed intake by each lamb was measured daily.

2. The digestibility of the dry matter of the pelletted diet was determined in a conventional total collection trial with the adult wethers. Dry-matter and crude-protein digestibility "was determined in the lambs on faeces taken at, or just before, slaughter by the lignin-ratio method.

Data on the performance of British, Africander cross British and Brahman cross British females were examined. Of the animals mated only 56-0% of the homebred British cows produced live calves compared with 77-3 and 73-8% from Africander and Brahman cross cows respectively. Evidence was found that the low calving percentage for the.British females was connected with breeding stress, the British females being frequently unable to maintain weight if pregnancies occurred in two successive years. Under similar stress conditions crossbred-Zebu cows could thrive and breed and crossbred Brahmans in particular would normally maintain their weight.

The metabolic activity of spermatozoa, obtained from Awassi, German Mutton Merino, Corriedale and Dorset Horn rams, waa measured every 2–4 weeks over a 2-year period.

1. It has proved possible to operate a ‘worm-free’ area in which sheep grazing experiments can be carried out, without significant interference from disease.

2. The organization of such a unit is described and the results are presented in terms of the problems and difficulties which have been encountered during 4 years of continuous and increasing use. There is no apparent reason why these problems should increase with time.

1. A study of the effects of live-weight loss and recovery on the physical and chemical composition of 4- and 5-year-old Romney ewes is described. Six treatment groups each of eight ewes were involved. The diet consisted of chaffed lucerne alfalfa) hay. The treatment groups were:

(i) control (C);

(ii) low plane of nutrition for 21 days (LPS);

(iii) as for (ii) then changed to a high plane LPS: HP);

(iv) low plane of nutrition for 42 days (LPL)

(v) as for (iv) then changed to high plane for a short period (LPL:HPS); and

(vi) as for (iv) then changed to high plane for a long period (LPL:HPL).

Because of mortalities in the LPL:HPS and LPL:HPL groups, data on the carcasses and internal organs of the animals surviving to slaughter date in these treatments were not statistically analysed.

Exhaustion tests were carried out with two Awassi rams 4 times a year for 2 years. The maximum sperm number was obtained in October and the minimum in January. If we consider that the time needed for one spermatogenic cycle and for the migration of the sperm cells through the epid i dymal canal is over 2 months, we may assume that the spermatogenic activity changes with the length of day and reaches its maximum and minimum values during the longest and shortest days, respectively, whereas its androgenic activity is delayed by 3–4 months after the length of daylight changes.

Bull spermatozoa were deep-frozen to −79° C. in diluents prepared with 1% lecithin and containing mixtures of sodium citrate, sodium chloride, fructose, glycine and gelatin, and revival rates measured after thawing, using scores of motility rate of progression of spermatozoa), the visual estimation of percentage of motile spermatozoa and the percentage of spermatozoa unstained by Congo-red-nigrosin. The experimental design was a one-ninth replicate of a 37 factorial. A decrease in the time taken to cool samples