The digestibility of some fats (beef tallow, HEF, herring oil, soyabean oil and maize oil) were studied in balance trials with sheep which had been maintained on the diets for a 35 day period of acclimatization to establish ‘steady state’ conditions. Corrected digestibility coefficients for the individual fats were calculated from a knowledge of the intake and output of lipid on a low-fat basal ration. The difference between the intake of fat and the corrected lipid output (total lipid output minus lipid output on basal ration) expressed as a percentage gave the corrected digestibility coefficients.

It was found that the corrected digestibility coefficients for beef tallow was 85%; HEF, 74%; herring oil, 84%; soyabean oil, 83%; and maize oil, 70%. The values for beef tallow and HEF were comparable to similar estimates in pigs. The digestibility of the highly unsaturated soyabean and maize oil were markedly lower in comparison with non-ruminant species. Extensive hydrogenation of dietary unsaturated fatty acids was confirmed. For soyabean and maize oil the corrected output of stearic acid exceeded the dietary intake.

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.

Statistical tests were made on the data obtained from 100 non-pregnant lactating cows, whose milk production ranged from 4 to 22 kg/day. The cows were kept in metabolism stalls and fed 37 different rations.

The authors have studied the correlation between total water intake, faecal and urinary water losses, absorbed and available water and the numerous other factors which were analysed in each of the 37 rations.

Total water intake is closely related to the dry-matter intake and the dry-matter content of the diet; it is related also to the composition of the ingested dry matter but is unrelated to the daily milk production.

Faecal water losses are closely related to the dry-matter intake and the dry-matter content of the diet; increase of pentosans and crude-fibre intake enhances the losses.

Urinary water excretion is related to the amount of absorbed water and to the dry-matter content of the diet; a highly significant correlation exists also between urinary water and urinary nitrogen and potassium. Daily milk production and urinary water are negatively correlated.

Water secretion in the milk depends on the dry-matter intake and on its composition; but there is no significant correlation between total water intake and milk water.

The effect of fatty acid chain length and unsaturation on digestibility in sheep were examined using partially purified samples of lauric, myristic, palmitic, stearic, oleic and linoleic acids. The digestibility of the fatty acids was relatively constant with only a very slight decrease on increasing chain length. There was an extensive hydrogenation of the unsaturated fatty acids.

The corrected digestibility coefficients for lauric acid was 91%, myristic 86%, palmitic 87% and stearic acid 81–83% whereas the corrected digestibility coefficients for oleic and linoleic acids were calculated at 87 and 93% respectively. The digestibility coefficients for the saturated fatty acids are higher than similar estimates that have been reported for non-ruminants. It is suggested that the ruminant is better able to utilize saturated fatty acids than the non-ruminant.

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.

Carcass yield and chemical composition of edible meat of fifteen fattened yearling rams and fifteen fattened yearling wethers of Sudan Desert sheep were studied. The animals studied were random samples from groups which had been fattened for 2 months on three different rations. They were about 14 months old at slaughter, and their weights at slaughter ranged from 25 to 52 kg. The average dressing percentage for rams and wethers was 53·0 and 52·2% respectively. Warm carcass weights were 20·22 kg for rams and 19·64 kg for wethers, and these carcasses lost 4·2 and 3·1% of their weight respectively, after 48 h storage in the cold room at 0°C. The bone content of carcasses of rams and wethers was 23·4 and 21·3% respectively. The longissimus dorsi ‘loin eye’ area at the 12th rib was 8·6 cm2 and 8·3 cm2 for rams and wethers. The proportions of wholesale cuts in ram and wether carcasses were comparable, whereas the proportions of slaughter by-products varied between the two ‘sexes’. Mean weight of kidney fat in wethers was 50% greater than in intact rams, but the mesenteric and caul fat was heavier in rams than in wethers.

Ram carcasses had higher specific gravity than those of wether carcasses. Specific gravity was negatively correlated with fat content and positively correlated with protein, moisture and ash content of the edible meat of the carcass. The regression equations relating specific gravity to the major chemical components of meat had too high standard errors to be of predictive value in a practical sense.

Four soil moisture and two nitrogen levels were combined in eight treatments to study moisture and nitrogen effects on Dular (June–September crop) and Patnai-23 (June–November crop) varieties of rice. Both the varieties when grown under natural precipitation yielded significantly less than at other moisture levels. Whereas there were no significant differences amongst the three treatments of submergence (15–10 cm), cyclic submergence (15–0 cm) and cyclic wetting-drying (saturation to field capacity) for Dular rice, the former two treatments proved better than the latter for Patnai-23 rice. Dular responded to the treatments of cyclic wetting-drying in a way similar to that of submergence because the crop completed its life cycle during the period of low evaporative demand. Among the levels of nitrogen, 40 kg N/ha proved optimum for Dular rice and 6O kg N/ha for Patnai-23 rice. The increase in yield of grain was associated with increase in the number of panicles, number of spikelets/panicle and percentage of ripened spikelets. The concentration of N, P, Fe and Mn in the plant was maximum under submergence followed by cyclic submergence, cyclic wetting-drying and natural precipitation. Higher levels of nitrogen increased only N and P contents in the plant.

An experimental and a conventional grazing system for 7- and 19-month-old dairy replacements were compared during 136 days of the grazing season. In the experimental system A, 24 calves were rotationally grazed around paddocks followed by 24 pregnant heifers which ate the herbage residue left by the calves. The conventional system B consisted of 24 calves and 24 pregnant heifers maintained at the same overall stocking rate as in system A, but the calves and heifers grazed in completely separate rotations. Half the calves on each system were drenched with an anthelmintic at weekly intervals from mid-July onwards to estimate within systems the effect of gastrointestinal worms on live-weight gain.

Results are given for a second period of 9 years, 6 on the pattern of 1951–9, with the last 3 years used for ad hoc management experiments. The meteorological specification of a year of ‘irrigation need’ was satisfied in 4 years: there were good responses in 5 years. During the first 6 years, out of twenty-four sets of crop yields (from eight different crops), very good responses were obtained on nine, good responses on eight, and zero or very slightly negative responses on the other seven.

A general theory of the inter-relationships of growth and water, and of growth and radiation, leads to an expression

k = 39ε t ha−1 cm−1,

as the maximum possible response to irrigation in terms of total dry matter produced, where ɛ is the fraction of solar radiation fixed by the crop (ɛ has a range 50–100 × 10−4 for good to very good farming) when irrigation is needed. The ‘need’ is defined through

Y = k(ET + De − Dm),

where Y is the yield, ET is the total potential evaporation, De is a limiting deficit up to which there is no check to growth, and beyond there is no growth, and Dm is the maximum deficit experienced by the crop at the time of measuring Y. The agronomic object of the experiments is to determine De, i.e. what reserve of soil water can be used by the crop before irrigation is necessary.

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.

Experiments on a sandy loam, using adequate fertilizer, gave:

(a) Crop yield (as total dry matter) when soil water content was kept near field capacity.

(b) A measure of the departure from field capacity (limiting deficit, Dι) that produced no detectable change in yield.

(c) Responses to irrigation: (i) conventional, as δY/δI; (ii) a theoretical maximum, k, after allowing for Dι in the water balance.

(d) Other information, botanical and technical.

Grass (S 22 Italian ryegrass)

Two year crop, cut fourteen times, October 1959 to October 1961.

(a) Best yields: 1960, 15 t ha−1 (ɛ ≃ 100 × 10−4); 1961, 12 t ha−1 (ɛ ≃ 70 × 10−4).

(b) Dι ≃ 5 cm.

(c) (i) δY/δI: 1960, 0·36; 1961, 0·43 t ha−1 cm−1; (iii) k: 1960, 0·40; 1961, 0·27 t ha−1 cm−1.

(d) In 1960 irrigation was needed in spring only: the benefit was maintained on plots with large N and K dressings, but almost disappeared on those with small dressings (Y = 11 t ha−1). In 1961 the unirrigated crop could not exploit all the limited summer rain: hence δY/δI > k.

One year crop, cut five times, March to October 1965.

(a) Yield, 12 t ha−1 (ɛ ≃ 90 × 10−4, from emergence).

(b) and (c) (i) The meteorological need was slight, Dι (above) was not exceeded, and there was no response; (c) (ii) k = 0·46 t ha−1 cm−1.

Lucerne (Du Puits)

Three year crop, cut eleven times, April 1962 to November 1964.

(a) Best yields: 1962, 7; 1963, 8; 1964, 10 t ha−1.

(b) Dι = 11 cm for established crop.

(c) (i) No response other than in first dry spring of establishment. At first cut δY/δI = 0·18 t ha−1 cm−1, (ii) k = 0·26 t ha−1 cm−1.

(d) Extra K seemed to be helpful in sustaining the early benefit throughout the 3 years.

Clover (Crimson)

One year crop, drilled April and cut (once only) July 1963.

(a) Best yield: 3 t ha−1.

(b) Dι, not detectably different from zero (evidence inadequate).

(c) (i) δY/δI = 0·16 t ha−1 cm−1; (ii) k ≃ δY/δI (?).

(d) First cut completely defoliated irrigated crop, there was no recovery, and the experiment was abandoned.

Clover (Dorset Marl)

One year crops undersown in previous barley crops, 1963 for 1964 (three cuts), 1964 for 1965 (three cuts).

(a) Best yields: 1964, 9 t ha−1 (ɛ ≃ 60 × 10−4); 1965, 8 t ha−1 (ɛ ≃ 60 × 10−4).

(b) Dι ≃ 2·5 cm.

(c) (i) δY/δI: 1964, 0·24 t ha−1 cm−1. 1965, no response; (ii) k: 0·22–0·34, depending on method of derivation.

(d) The response to irrigation was slightly greater on plots not previously irrigated in the barley year. In (c) the uncertainties arise out of excessive rain after the first irrigation in 1965; there was estimated drainage from the irrigated plots but not from the control plots. In 1964, the control plots failed to exploit all the summer rain.

General

There seems to be a need to know two limiting deficits, one, the Dt of these papers, that is a measure of what can be tolerated without any check to growth, and a second that is a kind of maintenance deficit, necessary to keep the crop non-senescent so that it can use all the rain it gets.

Irrigation greatly helped the establishment of all three leys, and both grass and clover responded well to later irrigation. Lucerne did not. In English units, the limiting deficits, Dt, for well-fertilized established crops were, approximately, 4 in for lucerne, 2 in for grass, and 1 in for clover.

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.

The total body content of fat, protein, ash, moisture and energy of 43 male cross-bred lambs was determined after the lambs had suckled the ewe at pasture for between 2 and 5 days. Sixteen lambs were dissected into seven compartments, namely, carcass, skin, wool, blood, viscera (two groups) and vastus lateralis muscle, and the chemical composition of each was determined. The heats of combustion of the fat and fat-free tissues were also determined. The relationships between empty body weight and body and organ composition were described by logarithmic regression equations.

Eighteen male cross-bred lambs (aged 2–5 days) in two equal groups were given artificial milk diets of either low- or high-protein content; subgroups of three lambs were slaughtered after 2, 4 and 6 weeks on experiment. The composition of the change in empty body weight (E.B.W.), and the chemical composition of the change in weight of the separate compartments and organs, were determined by the comparative slaughter method.

Lambs given the high-protein diet made significant gains in weight and in all chemical components in all periods. The composition of their E.B.W. was closely related to E.B.W. regardless of age. Lambs given the low-protein diet made only small gains in weight in 6 weeks, of which 76% was fat. The chemical composition of their E.B.W. was closely related to E.B.W. within each age group. The net gain of protein of these lambs in 6 weeks represented only 1% of the total weight gain, and over 50% of the protein gain was in wool. The skin and blood lost protein during the first 2 weeks, and failed to recover this loss during the remaining 4 weeks. Other organs lost protein initially but recovered this loss between 2 and 6 weeks.

It was concluded that the initial loss of protein represented the labile protein reserves of the lamb, and the subsequent recovery was an adaptation to the low-protein diet. Furthermore, the results with both diets indicated that the skin and blood were the most inefficient of the organs in the body in utilizing the available N during a period of protein deficiency, or during a period of abundance in the dietary supply of N.

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.

Experiments on a sandy loam, using adequate fertilizer gave:

(a) Crop yield when soil water content was kept near field capacity.

(b) A measure of the departure from field capacity (limiting deficit, De) that produced no detectable change in yield.

(c) Responses to irrigation: (i) conventional, as δγ/δΙ (ii) a theoretical maximum, k, after allowing for De in the water balance.

(d) Other information, botanical and technical.

Sugar beet

(a) Best yields of sugar: 1963, 9; 1963, 10; 1964, 8 t ha-1.

(b) Limiting deficit can increase to ca. 10 cm by end of September.

(c) (i) Best δγ/δΙ. 1963, 0·18 t ha-1 cm-1 (some need); 1964, 0·62 t ha-1 cm-1 (great need); 1965, slightly negative (no need); (ii) inferred k = 0·4 t ha-1 cm-1 for sugar, and ca. 1·0 t ha-1 cm-1 for total dry matter. For the period sowing to harvest the values of e are 0·7 and 1·8 x 10-2 respectively.

(d) Excess water (as in 1964) seems to depress the sugar yield slightly.

Potatoes, main crop (part of an experiment on control of nematodes, under continuous cropping)

(a) Best fresh weight yields of tubers: 1966, 46 (without irrigation); 1967, 38 (with irrigation); 1968, 33 (with irrigation), t ha-1.

(b) Evidence inadequate.

(c) Responses were small, or negative; (i) best response, in 1967, 0·7 t ha-1 cm-1; (ii) evidence inadequate.

(d) Decreased yield in 1966 may be caused by early summer leaching: the effect was about equal to removing half of the nitrogen fertilizer applied.

Potatoes, early (Arran Pilot)

(a) Best fresh weight yields of tubers: 1960, 32; 1961, 37; 1962, 16 t ha-1, all at larger of two nitrogen dressings, and after normal cultivation.

(b) De ≃ 2·5 cm.

(c) (i) Best δγ/δΙ. 1960, 1·7; 1961, 2·0; 1962, 1·1 t ha-1 cm-1, (ii) k = 1·8 t ha-1 cm-1 for nitrogen at 0·6 cwt acre-1; k = 2·11 ha-1 cm-1 for nitrogen at 1·2 cwt acre-1. Inferred values of ɛ are 1·15 and 1·45 x 10-2.

(d) Weed control by chemical means was not successful: all yields and responses were decreased by about one-third.

Barley, spring (Proctor, Maris Badger)

After early potatoes, some plots has a crop of trefoil, ploughed in (crops of 1961–3). In 1968, barley was test crop in an experiment on fumigants. Cropping in 1960 and 1964 was normal.

(a) Best yields of grain, 3·4–4·8 t ha-1 (without trefoil); 4·1–5·4 t ha-1 (after trefoil).

(b) De ≃ 4 cm before ear emergence, and unimportant thereafter.

(c) (i) Best δγ/δΙ, in 1962, ca. 0·20 (no trefoil), and 0·30 (after trefoil) t ha-1 cm-1, both at upper of two nitrogen dressings; (ii) k (for variety Proctor only, and no trefoil) ≃ 0·20 t ha-1 cm-1, and may be independent of nitrogen treatment.

(d) Previous management of early potatoes did not affect barley yields. For 1961–3—average yield of all treatments = 3·53 t ha-1—the average responses were: to trefoil, 0·46 t ha-1; to nitrogen, 0·76 t ha-1; to water 0·95 t ha-1. Trefoil halved the response to nitrogen, and may have increased the response to water.

Within limits, water and nitrogen seem to be interchangeable as management factors.

Wheat, spring (1965, Opal, in a normal experiment. 1966, 1967, Kloka in an experiment with a dwarfing compound, CCC. Four levels of N fertilizer)

(a) Best yields of grain, 1963, 4·5; 1966, 5·8; 1967, 5·9 t ha-1.

(b) De ≃ 4 cm before ear emergence, and ca. ET/4: thereafter.

The evidence is flimsy.

(c) (i) Best δγ/δΙ. 1965, 0·11; 1956, 0·16; 1967, 0·12 t ha-1 cm-1; (ii) evidence is inadequate to derive values of k, but it seems to be very small with N1 (0·4 cwt acre-1 N), and perhaps of order 0·2 t ha-1 cm-1 at all the bigger dressings (2–4 x N1).

(d) On average, CCC had no effect on grain yields, but it decreased straw yields. In 1967 many sub-plots gave very large yields: the average of nine was 12 t ha-1 as total dry matter; three were not irrigated, and had no CCC; three had CCC and were irrigated. None was at the smallest N treatment. Spring wheat responds to water like any other crop when given enough N (ca. 0·8 cwt acre-1 N, or a little more). The need continues after ear emergence.

Beans, winter 1960, spring 1961, 1962, 1968

(a) Best yields of grain, 1960, 3·7; 1961, 3·1; 1962, 3·6; 1968, 3·0 t ha-1.

(b) De ≃ 4 cm.

(c) (i) Best δγ/δΙ. 1960. 0·18 (late watering); 1961, 0·15 (early watering); 1962, 0·22 (late watering); 1968, 0·02 (early watering and then rain in excess); (ii) k = 0·17 t ha-1 cm-1.

(d) There is no evidence to show that irrigation is more important either before or after flowering (early and late, in (c)).

General

Exception for the main-crop potatoes, all crops responded to irrigation as expected, with gains of 50–100% in the driest summers. In English units, the values of the limiting deficits were, approximately, up to 4 in by the end of September for sugar beet, 1 in for early potatoes, 1½ in for barley before ear emergence, 1½ in for wheat before ear emergence and up to about 3 in 5 weeks later, and 1½ in for beans.

Nineteen male cross-bred lambs, aged between 2 and 5 days, were allotted to each of three dietary treatments. The protein contents of the diets (on a dry-matter basis) were 12·0% (diet A), 28·5% (diet B) and 45·5% (diet C). The energy intakes of groups of lambs within each dietary treatment varied from below maintenance to ad lib.

The experimental period was of 3 weeks and the composition of the live-weight gain was estimated by the comparative slaughter method.

Body composition within each dietary treatment was highly correlated with empty body weight, but not with the previous energy intake. The fat content of the gain decreased, and the water and protein contents increased, as the dietary-protein concentration increased.

When compared at the same empty body weight, the protein content of the fat-free body of lambs given diet C was significantly higher than that of lambs given diet A. This effect of dietary-protein concentration could not be explained by differences in the amounts of protein stored as wool.

Seed of Lolium perenne L. was grown from material collected from three S.23 leys and one S.24 ley that had been subjected to high rates of stocking and nitrogen application. Comparisons were made between plants grown from seed derived from the leys and from breeders' seed of S.23 and S.24.

Seedling characters indicated that the populations derived from leys differed from each other and from the plants grown from breeders' seed. In S.23 populations the main change occurring in intensively grazed leys was towards higher tillering prostrate seedlings. This did not occur in the S.24, but here the survivor population had a slightly shorter fifth leaf and a lower number of leaves on the main tiller of the seedlings.

As spaced plants, the population derived from the S.23 ley, with the highest percentage ryegrass and the reputation for the highest yields on the farm, gave a higher yield, recorded in three cuts in the first year and in four cuts in the second year, than any other populations. Small differences between S.23 populations in aftermath heading, reaction to rust, and mean date of panicle emergence were recorded. Variance of spaced plant yield decreased in ryegrass derived from older S.23 leys. The S.24 ‘survivor’ population was much later in mean date of panicle emergence than S.24 grown from breeders' seed.

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.