Twenty-seven sheep feeding trials were carried out on freshly cut Andropogon gayanus, fed daily during three wet seasons, 1966–8.

In each year, dry-matter voluntary intake and digestibility were highest during the first part of the growing season and declined with advancing maturity of the herbage. However, at the time of ear emergence in early October, there were small increases in voluntary intake of dry-matter and crude protein digestibility, although further decreases followed after mid-October.

Determinations of in vitro digestibility indicated that elongating stems during early October were at least as digestible as leaves.

Seasonal changes in crude protein digestibility were much greater than changes in dry-matter digestibility; seasonal changes in feed intake were intermediate. Voluntary feed intake was related to dry-matter digestibility.

Voluntary feed intake and digestible crude protein were both closely related to the crude protein content of the forage. It was concluded that crude protein is a useful criterion for predicting nutritive value.

Two varieties of irrigated rice N.P. 130 (a tall variety) and Taichung Native-1 (a dwarf variety of indica rice) were compared in 1966 and 1967 when grown with several amounts of sodium nitrate and ammonium sulphate. Comparisons of ammonium sulphate treated with ‘N-Serve’ or with ‘AM’ against untreated ammonium sulphate were made.

Applying more than 60–80 kg N/ha did not increase the number of panicles per m with N.P. 130 but lowered the number of spikelets and filled grain percentage. Up to 120 kg N/ha, panicle number and the number of spikelets of Taichung Native-1 increased significantly but the filled grain percentage was not increased; yield of grain responded significantly up to 120 kg N/ha. Taichung Native-1 yielded more grain and less straw than N.P. 130. Increasing the nitrogen applied significantly increased the yield of straw from both varieties.

Ammonium sulphate increased panicle number and reduced the percentage of filled grain compared to sodium nitrate but the increase in panicle number was higher with Taichung Native-1 than with N.P. 130; as a result ammonium sulphate consistently increased the grain yield of Taichung Native-1. When the ammonium sulphate was treated with either inhibitor it gave more grain of Taichung Native-1 than untreated fertilizer; treated fertilizer gave more straw of both varieties.

In two feeding experiments the effects of different sources of protein on nitrogen utilization were studied. Three protein sources were examined in both experiments; (a) soya-bean oil meal; (b) lucerne hay or vetch oat hay, and (c) a mixture of soyabean oil meal and hay. The first experiment was carried out with nine adult rams and the second with twelve growing rams.

The results of N balance experiments showed clearly the superiority of the hay ration over the soya-bean meal ration. N retention when the mixed ration was given was greater than on hay alone. No parallel trend was found between the protein digestibility of any of the diets and its efficiency for N retention.

With adult sheep a negative correlation between the extent of N retention and blood urea concentration was found; this agreed with our earlier findings. No such negative correlation was found with growing animals.

The highest concentrations of the various forms of soluble N compounds such as soluble a-amino N, diffusible N and diffusible peptide N were found in the rumen liquor taken from the sheep kept on the hay diet. The lowest amounts were observed when the soya-bean oil meal diet was given and intermediate amounts with the mixed diet. These trend sappeared to be related to the NPN (non-protein nitrogen) content of the diet, but the amounts of soluble N compounds present in rumen liquor were not directly correlated with the extent of N retention.

Concentrations of VFA present in rumen liquor depended primarily on the carbohydrate composition in the diet. The type of protein ingested exerted some influence, particularly on the concentrations of caproic and iso-caproic acid. The ratios of concentrations of the individual fatty acids in blood to the concentrations of the same acids in rumen liquor were found to increase with lengthening of the fatty acid chain.

Maturation studies were carried out on 241 cattle oocytes. Media used were bovine follicular fluid and growth medium. Both media supported a resumption of meiosis in ca. 80 % of cases, but growth medium proved superior in terms of final maturation.

Fertilization attempts were carried out on 564 oocytes following culture (27–32 h) in growth medium. In vitro fertilization attempts (107 oocytes) and in vivo fertilization attempts (82 oocytes) in the rabbit yielded negative results. Following in vivo fertilization attempts in the ewe, ova containing pronuclei as well as apparently normal cleaved ova were recovered.

Sweating rate and the electrolyte content of secretions from the skin of cattle have been measured on five Bos taurus and five B. indicus cross-bred cows by absorbing secretions into filter papers under polythene disks applied to shaved skin areas on the shoulder, sacral and lumbar regions for 5 min. The increase in weight of the filter paper was taken as a measure of sweating rate and the distilled water eluate from the filter paper was analysed for sodium and potassium. Animals were exposed for 4 h to air temperatures of 20–45 °C at 30% r.h., and for 5–7 h to air temperatures of 40 and 45 °C at 40% r.h. Estimated sweating rates were low by comparison with previously reported values, probably due to rising levels of humidity under the polythene disks during exposure to the skin. B. indicus cross-bred cows had higher sweating rates than B. taurus cows at high air temperatures but the difference between the groups was not significant statistically. Sweating rates were generally highest on the shoulder and lowest on the lumbar region.

The amounts of sodium and potassium recovered from filter papers were small and very variable at low air temperatures but increased significantly with air temperature (P < 0·01). No significant differences in the amounts of electrolyte recovered from filter papers were recorded between the species groups or between different sites of collection. The secretions from cattle skin at high ambient temperatures contained at least four to five times as much potassium as sodium. Total sodium and potassium loss through the skin of these experimental animals at the highest ambient temperatures was estimated to be no more than 1–3 % of the sodium and potassium intake in the feed. Absorbing sweat on to filter paper as a method of measuring sweating rate and sweat composition is rather less satisfactory for use with cattle than with man.

An experiment was carried out in which each of thirty-six ewes was offered one of six dietary treatments from the 30th to the 140th day of gestation. The treatments supplied two levels of metabolizable energy (ME) intake (128 and 116 kcal/kg W0.75/day) each at three patterns of protein intake, namely equal increments at 22 day intervals, equal decrements at the same intervals and a constant daily intake throughout. The protein intake patterns supplied a mean daily intake of digestible crude protein of 3·74 g/kg W0.75/day. Nitrogen balances were carried out on four ewes from each dietary treatment during the last 10 days of each 22 day period.

Thirteen ewes randomly distributed on all dietary treatments were barren. Mean rate of live-weight gain in the pregnant ewes was 123 g/day compared with 66 g/day in the non-pregnant ewes and was not significantly affected by treatments. Lamb birth weights adjusted to the basis of twins were 3·83, 4·02 and 3·56 kg for the increasing, constant and decreasing patterns of protein intake respectively.

Within patterns of protein intake there were no significant differences in nitrogen retention between pregnant and non-pregnant ewes until after 90 days of gestation. Thereafter retention increased in the pregnant ewes offered the constant and increasing patterns of crude protein and remained constant in the non-pregnant ewes. During the same period the retention of both pregnant and non-pregnant ewes on the decreasing pattern decreased.

The effects of both energy and protein intake on nitrogen retention in early and late pregnancy were assessed by multiple regression analysis. The results are discussed in relation to other recent findings.

Surface soils (0–15 cm) from a field experiment on a sandy podzol were used to evaluate the residues from basic slag, Gafsa rock phosphate and superphosphate (using ryegrass in pots), and to measure the solubility and buffer capacity during cropping, and the distribution of the residual phosphate in different particle-size fractions of the soil.

After applying P at about 3·6 g P/m2/year for 6 years, residues of the three P fertilizers were equivalent but after applying more P (9–11 g P/m2/year) for a further 8 years, basic slag and rock phosphate gave larger labile P values, were more effective for ryegrass and buffered soils more than residues of superphosphate. The percentage recoveries of P from the surface soils were approximately 7, 40 and 65 % of the total applied in 8 years as superphosphate, basic slag and rock phosphate respectively.

Residues from basic slag (mainly 75–20 μm particles) accumulated in the < 20 μm fraction of the soil. Rock phosphate (mainly 200–20 μm particles) dissolved more slowly and about one-half of the material > 20 μm remained in the sand fractions of the soil.

Residues from rock phosphate maintained values of ½pCa + pH2PO4 and pH–½pCa consistent with the solubility of fluorapatite, even when P was removed from the soil by exhaustive cropping with ryegrass. Residues from basic slag were more soluble than hydroxyapatite.

Sixteen varieties of groundnuts were included in a variety trial at three locations in 3 years in Western Nigeria. Significant ‘variety x environment’ interactions were observed, indicating that none of the varieties possessed wide adaptation. It is suggested that Western Nigeria be divided into sub-areas for which varieties showing specific adaptation could be developed.

The nitrogenous composition of the water soluble fraction of maturing grass silage was investigated in detail. Empirical methods of group analysis demonstrated the complete absence of water soluble proteins, and that the major changes, involving the formation of amino acids and volatile amines, were completed within the first 2 months of ensiling. These methods were unable to account for a high proportion of the soluble nitrogen. Changes occurring within the soluble carbohydrate and volatile fatty acid fractions indicated that while secondary fermentations occurred some 8 months after ensiling they did not have any marked influence on the nitrogenous components.

A detailed analysis of the individual components of the nitrogenous fraction was undertaken using both conventional methods of ion exchange chromatography and techniques developed especially for this purpose (see Hughes, 1969). Selective degradation of the amino acids liberated by the proteolysis of the grass proteins occurred. The volatile basic nitrogen content was comprised of ammonia. The non-volatile amine fraction, which accounted for a considerable proportion of the soluble nitrogen, was mainly composed of putrescine and cadaverine. There was no free histamine and only low concentrations of bound histamine were found. Evidence suggested that these amines were being further metabolized during the storage of the silage.

A project has been initiated to study the growth of barley under conditions of partial drought. The method of producing the drought and comparisons of measurements of evaporation using lysimeters and neutron moisture meters are discussed. Good agreement was obtained between the lysimeter and neutron probes in the lysimeter tank and in the field.

In the plots subjected to drought the evaporation was reduced by approximately the amount of rain prevented from falling on the plots and, as a result, the reduction in soil moisture deficit was quite small.

Estimates of internal diffusion resistance are made throughout a full season.

Evapotranspiration from spring barley plots grown at a range of densities was estimated using the neutron probe technique. Early in the season rainfall led to percolation and kept the soil at field capacity, but from the beginning of June significant differences were found in the cumulative evapotranspiration. As the crop canopy was complete by this time in all densities, it seems probable that evapotranspiration at this time was dependent on rooting density. Although the total water use at the end of the season was similar at all densities, the more rapid use earlier in the season at higher densities may have led to a reduction in growth at the grain filling stage.

Soils from Broadbalk field were used to find whether differences in K-manuring had altered K:Ca exchange relationships during 100 years cropping with wheat, by measuring cation exchange capacities and quantity/intensity (Q/I) relationships.

Cation exchange capacities (CECs) were measured with and without the contribution of the soil organic matter and the following mainly non-significant trends arose during 100 years: (1) The CECs of plots given K fertilizer increased slightly when the organic contribution is included and decreased slightly when it is not. (2) The CEC of the plot given farmyard manure increased greatly when the organic contribution is included and decreased slightly when it is not. (3) The CEC of the unfertilized plot increased very slightly, whether or not the organic contribution is included.

The K buffer capacity, the slope of the Q/Icurve when the soil neither gains nor loses K, was related to the K saturation of the CEC better when the organic contribution was omitted from the CEC than when it was included, suggesting that K: Ca exchange measured by the Q/Icurves occurs mainly on the non-organic part of the CEC. Two soils depleted of K had anomalously large buffer capacities, but two undepleted samples behaved similarly.

Superimposing Q/Icurves by eye showed no appreciable differences between samples from different years or from different plots, even at large activity ratios. Plotting exchangeable K against I0, the activity ratio when the soil neither gains nor loses K, gave a single curve embracing all plots from all years, similar to the superimposed Q/I curves. Long–term manuring with ammonium sulphate has not affected K–Ca exchange.

In each of two years, 36 Blackface ewes were brought to a high state of body condition at mating and in early gostation. At approximately 16 weeks prepartum the ewes were divided into two similar groups and fed to maintain the live weight and body condition of one group (fat), and to decrease that of the other group (lean). At 8 weeks prepartum mean differences of 14kg live weight and two scores of body condition had been created between the groups. During the last 6 weeks of pregnancy food was rationed to all ewes per unit of live weight to provide the theoretical requirements of Blackface ewes in late pregnancy. Both groups of ewes made similar live-weight gains in late pregnancy and blood plasma F.F.A. values confirmed that the ewes had been similarly nourished regardless of live weight or body condition. During early lactation food was restricted to fat and lean groups of ewes for either a 2- or 4- week period followed by ad lib. feeding for the remainder of lactation. A lamb-suckling technique was used to measure milk production during a 10-week lactation. During the first and second weeks of lactation the mean milk production of groups of both fat and lean ewes was approximately 2·1 and 1·3 kg/day for twin- and single-suckled ewes respectively. Ad lib. feeding following restricted feeding during the first 2 weeks of lactation resulted in increased milk production of fat and of lean ewes to mean maximum values of approximately 2·7 and 1·7 kg/day for twin- and single-suckled ewes respectively. In contrast, groups of ewes which had restricted feeding for the first 4 weeks of lactation showed almost no increase in milk production when fed ad lib. During the extended period of restricted feeding the milk production of twin-suckled ewes which were fat at parturition was significantly greater than that of twin-suckled lean ewes but there was no difference with singlesuckled ewes. All groups of ewes lost similar amounts of live weight and body condition during their respective periods of restricted feeding. In the respective 6-week periods following ad lib. feeding the live-weight gain of the lean ewes was significantly greater than that of the fat ewes (339 v. 222 and 356 v. 250 g/day for twin- and single-suckled ewes respectively), but they did not attain parity of live weight by the end of lactation. When fed ad lib. the mean intake of all groups of ewes attained similar maximum values of approximately 2·2 kg D.O.M./day. The results indicate that the stage of lactation is an overriding factor governing the response to increased nutrition and that body condition of ewes at parturition acts as a buffer between nutrient intake and nutrient requirements for lactation. It is suggested that when body reserves of ewes are severely depleted, factors other than nutrient intake may become limiting to milk production.

On the feeding regimes examined, i.e. hay ad libitum restricted hay and restricted hay with supplementary glucose, the quantities of extracellular water-soluble polysaccharides in rumen liquor were small (3·6–9·0 mg/100 ml) and could have originated from the diet or the saliva as well as from microbes. The polysaccharides extracted with hot water (fraction B) and acetate buffer (fraction C) were also small in amount in the rumen liquor from sheep on any of these diets (less than 56 mg/100 ml) and were composed of rhamnose—containing polysaccharides, starch-like polysaccharides and xylose polymers. Syntheses of these B and C polysaccharides were found with the hay and glucose diet but the quantities involved were small (12·27 mg/100 ml rumen liquor). Degradation of the polysaccharides occurred at 4–6 h after feeding. The consistently high ratios of rhamnose to hexose in the B and C polysaccharides from rumen liquor suggest that these were microbial in origin. Iodine-staining organisms in the rumen liquor were a small proportion of the total and showed no increases after feeding.

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.

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.

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.

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.

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.