The ensiling characteristics of grasses and of red clover were examined by means of a small scale vacuum silage technique. Eight grasses, comprising three varieties each of perennial ryegrass and cocksfoot and two varieties of timothy, were evaluated after application of two levels of nitrogen fertilizer. Three varieties of red clover were evaluated at two stages of growth with and without sucrose supplementation during ensiling.

Perennial ryegrass varieties contained more water soluble carbohydrates than cocksfoot and timothy varieties. At the low level of fertilizer N, silages made from the first cut in mid-May were all well preserved 3 weeks after ensiling. At the high level of fertilizer only perennial ryegrass varieties and S345 cocksfoot were well preserved. After ensiling for 14 weeks perennial ryegrass silages remained well preserved but secondary fermentation in the cocksfoot and timothy varieties resulted in poor preservation. Silages made from the second cut at the end of May were all badly preserved except for silage made from tetraploid ryegrass at the low nitrogen level.

Significant correlations were established between the water soluble carbohydrate content of the grasses and the quality of the resulting silage, but herbage dry-matter content and buffering capacity were not significantly correlated with silage quality.

The red clover varieties were lower in water soluble carbohydrate and higher in buffering capacity than the grasses. Although the silages from red clover were well preserved they were of high pH. Supplementation with sucrose significantly reduced pH and ammonia content and increased lactic-acid content.

A Nigerian, long-season, sorghum produced 15 tons of dry matter/acre in about 155 days, but the grain yield was small (2000 lb/acre or 2242 kg/ha) because only part of the dry matter formed after heading went into the grain. In contrast, an American, short-season hybrid which formed only from one-half to one-third as much dry weight as Farafara, gave over 4000 lb of grain/acre (4484 kg/ha) in 100 days. A Nigerian sorghum of intermediate height and a long-season hybrid, produced by crosses between Nigerian varieties and an American, short-season sorghum, gave larger yields than the tall variety because they formed more heads/unit area and more grains/head.

Crop growth rates of the three long-season sorghums sown in June increased to a peak in July, but declined sharply to very small values in September, and then increased again very rapidly at the end of September as heads emerged. The most important factors causing the decline were a decrease in radiation and a loss in dry weight from decay and detachment of dead leaves. An increase in radiation at the end of September and developmental changes associated with head emergence contributed to the increase in growth rates just before heading.

A large proportion of the dry weight formed after heading in Farafara accumulated in the stem but a smaller proportion in the other long-season variety and the longseason hybrid. There was an inverse relationship between the increase in stem weight and the yield of grain. For large grain yields, sorghums are needed that will produce heads with sufficient grains to accommodate all the assimilate that the leaves produce at the end of the rains when crop growth rates are increasing.

Changes in the leaf area and light profiles of a tall and a short sorghum are described and the development of leaf area in these and in two other sorghums of intermediate height is examined in relation to the rate of appearance, the size and the length of life of the leaves. The extent to which these changes are related to the seasonal fluctuations in crop growth rate is discussed.

A laboratory investigation was made of the ammonification and nitrification in soil of pure urea with and without pure biuret and pure biuret alone. The soils ranged from acid (pH 5·1) to calcareous (pH 7·9). The work was done at two temperatures 5 and 25°C. The time between adding urea to the soil and the first analysis was from 1 h to 1 week. The soil moisture contents ranged from the wilting percentage to field capacity. In all work involving urea, ammonium sulphate was used as a standard to compare rates of nitrification.

Biuret had no detectable effect on the rates of ammonification and nitrification of urea. Biuret by itself nitrified in all the soils at both temperatures being slowest at 5 °C in the acid soil and fastest in the calcareous at 25°C.

Neither pH nor temperature appreciably affected the ammonification of urea but both had a marked effect on nitrification. The lower the pH and the lower the temperature the slower the nitrification. Ammonium from urea nitrified faster than ammonium sulphate and on the acid soil only ammonium from the urea nitrified.

The moisture content of the soil only affected ammonification of urea slightly but had a marked effect on the nitrification, the drier the soil the slower the nitrification. The same observation applied to ammonium sulphate.

Forty-six cows in store condition (mean ± S.E. body weight of 366 ± 8 kg) were fed individually either 3 or 4 kg of coarsely rolled sorghum grain/head/day for the last 100 days of pregnancy and the subsequent 70 days after parturition. Eleven of the cows on each level of feeding had their calves weaned at 3 days of age.

For the last 100 days of pregnancy, 3 kg of grain/head/day was an adequate ration for survival, but cows fed this ration lost a mean of 34 kg of body weight over this period compared to 8 kg by cows fed 4 kg of grain/head/day. Only 78% of the cows fed 3 kg grain/day survived to 70 days after parturition, whereas all cows fed 4 kg/day survived. There was a 44% incidence of retained placentae and metritis in cows fed 3 kg grain/day whereas those fed 4 kg/day had only an 18% incidence. Weaning of the calves at 3 days of age reduced the body weight loss of the cows by a mean of 40 kg over the first 70 days of lactation, but the effect was less for cows fed 3 kg grain (27 kg) than for those fed 4 kg grain (53 kg).

Birth weight of the calves was not affected by the level of grain fed to the cows, but calves weaned and given 3 kg of milk/day plus a 50/50 creep of lucerne chaff and sorghum grain grew faster than calves not weaned and given only a sorghum grain creep.

The omission of a source of calcium in the grain ration resulted in no apparent adverse clinical effects in the cows. The Na:K ratio of the saliva indicated that nine of the cows had been depleted of Na.

Pregnant ewes of the Scottish Blackface and Romney breeds were group fed to achieve different patterns of live-weight change between mating and parturition. One group had a net maternal live-weight increase of about 8%, the second a net loss of about 5% and the third a loss of about 16%. Wool growth and sulphur content of the wool were measured at intervals. During the period 6–8 weeks prepartum wool growth rate in the Blackface breed was low and there were no significant differences amongst treatments. Differences in sulphur content were highly significant (ranging between 3·97 and 3·46% for fine and coarse fractions respectively in the well-nourished sheep down to 3·68 and 3·20% in the undernourished group). In the Romney breed the situation was reversed. In the prepartum period there were no significant differences amongst groups in sulphur content (mean value 3·68%), but differences in wool growth rate were highly significant (0·021, 0·012 and 0·009 g/100 cm2/day).

Sixty-four Blackface ewes in moderately fat body condition, were divided into two groups at 17 days before a chemically synchronized mating. One group was penned indoors (sheltered group), the other group penned outdoors in a climatically exposed position and subjected to artificial wetting for 6 h daily (exposed group). The ewes were fed a maintenance ration of 1350 g pelleted dried grass/head/day indoors and 1500 g outdoors.

The treatment was continued from 17 days premating to 25 ± 3 day post-mating. Immediately after mating 16 ewes from each group were interchanged between the two environments. Matings and returns to service were recorded, and at 25 ± 3 days after first mating the ewes were slaughtered. Counts were made of active corpora lutea and embryos; retarded embryos were distinguished. Fresh weights of the ovaries, pituitary, thyroid and adrenal glands were obtained.

Body condition of the ewes within the two environments was maintained. The mean ovulation rates of ewes holding to first service were significantly different (exposed group, 1·52; sheltered group, 1·86). There was no difference between the treatment groups in the number of ewes returning to service, but there was some difference in partial embryo loss, most of which occurred outdoors on or about day 14 or 15 postmating. The results suggest that ovulation rate and possibly early embryo mortality can be influenced by cold stress.

The free-acid content of grass silages was reduced by the addition of sodium bicarbonate to the silage and increased by additions of lactic acid. In each of four comparisons the addition of sodium bicarbonate to increase pH from about 4·0 to about 5·4 resulted in significant increases in intake of dry matter which ranged from 9·7 to 20·7%. Intake of organic matter was consistently increased by this partial neutralization treatment, but the increases were not significant in all experiments. The addition of sodium as sodium chloride rather than sodium bicarbonate did not alter the intake of a highly acid silage. Addition of lactic acid to reduce the pH of a silage feed from 5·4 to 3·8 resulted in a decrease in dry-matter intake of 22%. The correlation between dry-matter intake and the silage characteristics: titratable acidity, total organic-acid content, lactic-acid content and pH were all significant.

It is concluded that the acids produced during the normal silage fermentation can limit the intake of the silage and it is suggested that chemical treatments to preserve wet grass without the presence or formation of large quantities of acids be investigated.

Fifty-three experiments made between 1959 and 1968 tested the response to magnesium sulphate by sugar beet on fields where magnesium deficiency symptoms were expected. Soil samples, taken before applying fertilizers, were analysed for exchangeable magnesium by four methods. Sodium, potassium and calcium in the soil extracts were also measured to determine whether they influenced response to magnesium.

Results of different methods of analysing soil for magnesium were related to each other and to the percentage yield-response to magnesium fertilizer. The concentration of other soil cations did not affect response to magnesium fertilizer, but giving other cations, especially sodium, as fertilizer decreased the concentration of magnesium in the crop. Nevertheless, even on fields deficient in magnesium, the largest yield was from plots given sodium and posassium fertilizer together with a dressing of magnesium.

Sugar beet grown on soils containing less than 20 p.p.m. Mg extracted with ammonium nitrate usually gave a profitable response to magnesium fertilizer. When soil magnesium was 20–35 p.p.m., yield of sugar beet on some fields was increased slightly. Plants in some experiments had poorly developed root systems and response to magnesium was then always larger than expected from soil analysis.

In sheep fed red clover hay nearly 40% of the feed hemicellulose left the rumen undigested and scarcely any of this hemicellulose was digested in the postruminal digestive tract. The caecal microflora from sheep fed the same diet did, however, yield enzyme extracts which readily hydrolysed isolated hemicellulose or xylan preparations. These caecal and rumen microbial extracts, were capable of hydrolysing the hemicellulose in undigested particulate plant material but were not capable of hydrolysing, to any extent, the hemicellulose in undelignified digesta particles from various parts of the postruminal digestive tract. The hemicellulose in delignified postruminal digesta and the hemicellulose polysaccharides isolated from the digesta were hydrolysed by both rumen and caecal hemicellulases. The results are discussed in the light of observations on the postruminal digestion of hemicellulosic material in roughage- and cerealfed animals.

Changes in the concentration of copper in the blood of 241 adult ewes bled 4 times over a 12-month period (and 332 ewes over a shorter period) were analysed to examine sources of variation in the changes. Breed, age and swayback history were the most significant of the factors associated with both the amount and rate of decline in copper level from summer through autumn to winter. The number of lambs born, age of ewe, and swayback history were the most significant factors associated with the increase in levels from winter to the following summer.

There was a tendency for the classes of sheep with the relatively higher concentrations of copper in their blood to show less seasonal fluctuation in those levels than classes of sheep with relatively lower concentrations of copper.

The body composition of parasite-infected sheep and of healthy sheep of various body weights and breeding was predicted from tritiated water (TOH) space and body weight using previously published regression equations. Results agreed well with body composition determined by analysis of the minced carcass though a small bias existed in some groups. It is concluded that the equations have a general application to the prediction of body composition in sheep.

Selfed and diallel progenies of selected clones of Lolium perenne were subjected to four nitrogen rates—0, 225, 450 and 675 kg/ha of N per annum. The herbage was analysed for total nitrogen (N), digestible dry matter (DMD), digestible organic matter (D) and acid-pepsin solubility was determined on total (PS) and organic matter (POMS) in 1967 and 1968.

Data for the percentage composition and the yield of quality components are presented with the variances of general (g.c.a.) and specific (s.c.a.) combining abilities for these characters. The g.c.a. and s.c.a. interaction with nitrogen is partitioned.

For percentage quality components and yields there were significant effects of years, nitrogen rates, progenies and their interactions. The variance for g.c.a. for all percentage quality components was not significant in 1968 but in 1967 all were significant except for total N. For yields, only the g.c.a.'s for PS and POMS were significant in 1967: no g.c.a.'s were significant in 1968.

There were considerable differences between years for heritability values. For digestibility the predicted performance of a theoretical F2 synthetic was little better than the mean of the population from which it was derived.

The implication of these studies in the formulation of a grass breeding programme is outlined.

Concentrate diets supplemented with 5, 20 and 40% of a high- and a low-quality hay were given ad libitum to British Friesian steers from 9 weeks of age to slaughter. The intake of dry matter and metabolizable energy was studied over weight ranges from 91 to 363 kg live weight. The quality of hay did not significantly affect the drymatter intake at any of the weight ranges studied. From 91 to 182 kg live weight the daily dry-matter intake decreased as the proportion of hay in the diet increased. Over the weight range from 182 to 272 kg live weight, intake was maximum at the 20% level of hay supplementation, while from 272 to 363 kg live weight, intake increased with increasing levels of hay in the diet. The supplementation of high-quality hay significantly increased the intake of metabolizable energy by animals weighing 91–182 kg. Increasing proportions of hay in the diet significantly affected the metabolizable energy intake at all stages of growth studied.

At 18 and 36 weeks of age digestibility and N balance studies were carried out. The metabolizable energy expressed as a percentage of the gross energy and the mean retention time of the diets were significantly affected by the age of animal, quality of the hay and the level of hay supplementation. Nitrogen retention was also affected by the age of the animal but not by the quality of the hay.

The relationships between the voluntary intake of dry matter and the metabolizable energy of the diet expressed as a percentage of the gross energy, for different stages of growth, are also presented.

The change in the digestibility and the mean time of retention of the diets in the digestive tract with age and the effect of this on the point where physical regulation to intake gives way to physiological regulation are discussed.

Concentrate diets supplemented with 5, 20 and 40% high- and low-quality hay were given ad libitum to British Friesian steers from 9 weeks of age to slaughter.

The performance of the animals was studied over 91 kg weight ranges from 91 to 363 kg live weight and from 9 weeks of age to slaughter. In the whole experimental period the daily live-weight gain was significantly greater on diets containing high-quality hay. There was also an increase in the daily live-weight gain in each of the weight ranges studied on diets supplemented with high-quality hay but this increase was not significant at the stage of growth from 272 to 363 kg live weight. As the level of concentrate in the diet increased there was a significant increase in the daily live-weight gain at each stage of growth studied and over the complete experimental period.

The mean feed conversion ratio was greater for diets containing low-quality hay. Except during the stage of growth from 272 to 363 kg live weight the proportion of hay in the diet significantly affected the mean concentrate conversion ratio. With increasing levels of hay in the diet there was a significant increase in the total dry-matter conversion ratio.

The conversion ratio of metabolizable energy was also increased on diets containing low-quality hay. The proportion of concentrate in the diet significantly affected the conversion ratio of metabolizable energy at all stages of growth studied.

There were significant differences in the killing-out percentages, weight and contents of the reticulo-rumen and the omasum plus abomasum expressed as a percentage of empty body weight, with increasing levels of hay in the diet. These measurements were not significantly affected by the quality of hay in the diet.

Indirect measurements of carcass composition indicated that the level of hay in the diet tended to affect the amount of fat in the carcass but the amount of lean was similar at the different ratios of concentrate to hay. The ratios of the weight of separable lean to the weight of separable bone in the 9–10–11th rib cut were similar at different levels of hay supplementation. The organoleptic appraisal of sample joints indicated that carcass quality was satisfactory.

Five selected clones of Lolium perenne were selfed and the ten possible diallel crosses, without reciprocals, made. The progenies were grown in a split-plot design in which whole plots comprised the four nitrogen rates (0, 225, 450 and 675 kg/ha of N) and sub-plots the fifteen progenies, square planted at 0·25 m.

The percentage of the applied nitrogen recovered, and the utilization of the nitrogen by the plant, were measured. Data were collected from four harvests in each of two consecutive years. The diallel was analysed by Griffing's (1956) Method II, Model II.

There were significant effects for nitrogen rates, progenies and their interaction for both ‘recovery’ and ‘utilization’, but years were significantly different for ‘recovery’ only. The effect of applied nitrogen was mainly linear and it was the linear effect of applied nitrogen which interacted most with the progeny effects.

Significant g.c.a. and s.c.a. effects were found but they varied between nitrogen rates and years. For ‘utilization’ the interaction nitrogen rates x g.c.a. was significant on two year means but there was no significance for the nitrogen interaction with s.c.a. The g.c.a. values obtained for both parameters did reveal some trends between the five parents.

The presence of significant additive and non-additive genetic variation is discussed in relation to a plant breeding programme.

Heat-exchange chambers, one for heating and one for cooling, were surgically embedded beneath the skin of a sheep. The intensity of heating and cooling was progressively increased, producing average subdermal temperatures up to 50·3 °C over one chamber and down to 21·0 °C over the other. The normal subdermal temperature was 37·7 °C.

Moderate heating produced a small increase in the length growth rate of wool over the hot chamber. Higher temperatures caused a marked reduction and with still further heating there was almost complete cessation of wool growth.

In contrast to heating, cooling always caused a suppression of wool growth which became more pronounced as the degree of cooling was intensified. The length growth rate decreased to half of normal at one stage but it never ceased.

There was evidence of a slight but progressive decrease in fibre diameter with increasing subdermal temperatures up to 45 °C but at a temperature of 48 °C many of the fibres exhibited a marked thickening. Cooling the skin had little effect on fibre diameter. Pigmentation of the fibres was unchanged throughout the whole range of temperatures used and there was no evidence of change in crimping of the fibres.

Heating in the range 45–50 °C produced an increase in epidermal thickness. Sweat and sebaceous glands, and erector muscles appeared unchanged after heating or cooling but innervation of the skin appeared to be reduced by extreme heating.

The skin and wool growth over a dummy chamber were normal and similar in all respects to that in other control areas.

In a 2-year experiment anhydrous ammonia (82% N) and an ammonium nitrate fertilizer (34·5% N) were applied at three annual rates—100, 200 and 300 lb N/acre (112, 224 and 336 kg/ha)—on an S.24 perennial ryegrass sward. At each rate the two fertilizers were applied either as a single dressing in the spring or as five equal split dressings over the season. Total yields of herbage dry matter and of crude protein were determined by cutting the herbage at approximately the same stage of growth five times each year. On the basis of total yield and seasonal distribution of yield anhydrous ammonia was best applied as a single dressing in the spring, whereas ammonium nitrate was best applied as five equal split dressings over the season. However, in both years anhydrous ammonia applied as a single dressing gave smaller yields and a poorer seasonal distribution of production than did ammonium nitrate applied as five equal split dressings. The factors contributing to the lower yield level with anhydrous ammonia applications are discussed. It is concluded that anhydrous ammonia has no marked advantages over ammonium nitrate as a nitrogen fertilizer for intensively managed grassland.

The effect of three levels of N fertilizer on the ensiling characteristics of S. 24 perennial ryegrass and S. 37 cocksfoot have been examined during first growth in two growing seasons. The effects of sucrose supplementation, inoculation with Lactobacillus plantarum and wilting were also examined in certain cuts. All silages were made in the laboratory using a small scale vacuum silage technique.

The perennial ryegrass herbage was higher in water soluble carbohydrates than the cocksfoot, N fertilizers decreased soluble carbohydrates and dry-matter content in both species. Buffering capacity was not consistently different between grasses or between N levels.

Herbage was cut at two stages of maturity in the first year. In the first cut (8 days before ear emergence), perennial ryegrass silages were well preserved irrespective of the amount of N applied to the grass. Cocksfoot silages were well preserved only when the lowest level of N fertilizer had been applied (50 kg/ha). Supplementation of cocksfoot with sucrose prior to ensiling markedly improved silage quality, but inoculation had no effect. In the second cut (26 days after ear emergence) the grasses were higher in drymatter content and showed a lower buffering capacity, but neither ryegrass nor cocksfoot silages were well preserved unless supplemented with sucrose prior to ensiling.

In the second year of the experiment only one cut was taken (9 days after ear emergence). As in the previous year, silages made from herbage at a late stage of growth were poorly preserved. Wilting prior to ensiling resulted in well-preserved silages.

It is concluded that the need for additives and wilting to ensure satisfactory preservation varies in relation to the variety of grass used and its stage of growth.

Measurement of the variation in reproductive characters between genotypes of Phleum pratense showed that inflorescence length had a significant variance and was correlated with seed yield/plant. Genotypes with the longer inflorescences showed a quicker response to a long photoperiod and had a longer period of inflorescence development, and there was an indication that selection for increased inflorescence length might affect the production of leaves. A genetic analysis of a 6 x 6 half diallel cross showed that additive and non-additive effects were evident in the control of inflorescence length under natural conditions, but the non-additive effects were almost entirely suppressed under glasshouse conditions.