The effects of changing to a high starch: low roughage diet have been studied in two Friesian and two Jersey cows, surgically prepared for the simultaneous study of udder metabolism (arteriovenous difference x udder blood flow) and whole body turnover of milk precursors (isotope dilution).

In the Friesian cows milk fat concentration was lower on the high starch diet but in the Jerseys fell only slightly in one animal. In both Friesians and in the one Jersey these changes were accompanied by an increase in total rumen VFA concentration. Rumen acetate concentration did not change but propionate doubled. Thus this confirms that the usually reported fall in ‘acetate:propionate ratio’ is due to a rise in propionate production rather than due to a fall in acetate production.

There were significant falls in the blood concentrations of acetate and β-hydroxy-butyrate. The rate of extraction by the udder of acetate and β-hydroxybutyrate did not change but triglyceride extraction fell. Therefore since udder blood flow did not alter the uptake of all three fat precursors fell.

The entry rate of glucose into the circulation and its contribution to total body CO2 increased. The entry rate and contribution to CO2 of acetate decreased but this was probably mainly due to a fall in endogenous acetate production by the body tissues. Plasma FFA concentration showed little change but the entry rate of palmitate fell on the high starch diet. There was also an increased proportion of unsaturated and trans fatty acids in the plasma and milk triglycerides.

1. Nitrogen-balance experiments showed that casein supplements fed to hill ewes on a low plane of nutrition in the later stages of pregnancy were used very ineffectively, despite the animals' need for protein.

2. In confirmation of McDonald (1948a, b, 1952) extensive conversion of casein to ammonia was found to occur in the rumen, with absorption of ammonia into the blood stream.

3. Casein administered to sheep by duodenal fistual was better utilized than when administered by ruminal fistula.

4. The course of dissolution in the rumen of casein in the form of tough lumps was observed by a staining procedure.

5. It was found possible to process casein in a way that led to better utilization as shown by nitrogenbalance experiments. This processed casein gave less ammonia in the rumen.

6. It is concluded that the formation in the rumen of ammonia from proteins may be an important factor determining their usefulness to the animal. Processing may have effects on the value of a protein for ruminants quite different from those on the value for non-ruminants. The tendency to value proteins for ruminants solely in terms of their digestibility is criticized, and it is suggested that casein has disadvantages as a ‘standard protein’ in nutrition experiments with ruminants.

1. The accurate measurement of the amount of bone, muscle and fat in the bodies of meat animals is of considerable importance in all technical studies relating to carcass quality. Chemical analysis and laboratory dissection of complete animals are associated with disadvantages which preclude their extensive use. Material derived from nutritional experiments has provided the opportunity for statistical investigation of the possibility of using sample joints and carcass measurements as indices of the composition of bacon pigs of 200 lb. live weight. The extent and nature of the variation in the composition of the pigs concerned adds to the significance of the results obtained.

2. The total weight of bone, muscle and fat in the bacon-pig carcass can be estimated with a high degree of accuracy from the respective weights of these tissues in either the loin or the leg. The combination of these two joints provide even higher correlations in each case than either one alone. In all cases the correlation coefficients approach unity and are strongly significant at the 1% point. For the combined joints the values of r for bone, muscle and fat respectively are +0·9444, + 0·9765 and +0·9750. Regression functions have been developed for the purpose of estimating carcass composition from these joints.

The study examined the extent to which n-3 PUFA from different sources were biohydrogenated in the rumen and their effects on rumen microbial efficiency and whole tract nutrient digestibility. Four ruminally and duodenally cannulated wether lambs were used in a 4×4 Latin square design. Four iso-energetic and iso-nitrogenous diets based on dried grass were formulated to provide similar fat levels (60g/kg DM) from different sources; Megalac (palmitic acid: C16:0; Control), whole linseed (α-linolenic acid, C18:3n-3 ; Linseed) fish oil (eicosapentaenoic acid, C20:5n-3, EPA and docosahexaenoic acids C22:6n-3, DHA; Fish oil) and whole linseed plus fish oil providing equal amounts of oil (LinFish). Diets were offered at a rate of 1·2kg/day in 12 equal portions.

Total fatty acid intake was similar on all diets whilst duodenal fatty acid flow varied between 101, 94, 87 and 90% of dietary intake for animals fed the Control, Linseed, Fish oil and Linfish diets respectively. Duodenal flow of C18:3 n-3 in animals fed the Linseed diet was twice that of animals fed the Control diet (P < 0·01) whilst animals fed the Fish oil diet had a significantly greater flow of EPA and DHA than those fed any of the other dietary treatments. Duodenal flow of trans C18:1 in animals fed the Linfish diet was significantly greater than that in animals fed either Linseed, Fish oil or Control diets (P < 0·001). Biohydrogenation of C18:3n-3 was 80 to 93% in all diets whilst that of C20:5n-3 and C22:6n-3 was 72 to 79% in diets that contained fish oil or linseed and fish oil. Apparent fatty acid digestibility (duodenum to rectum) tended to be greater for unsaturated than saturated fatty acids whilst whole tract fatty acid digestibility (mouth to rectum) was significantly greater in animals fed diets containing fish oil (P0·05). All dietary n-3 PUFA sources decreased microbial protein synthesis and efficiency when expressed as either gN/kg organic matter (OM) apparently or truly degraded in the rumen. Additionally, the inclusion of fish oil increased the proportion of propionate in the rumen whilst depressing the rumen digestibility of OM and fibre (P < 0·01), but had no significant effect on whole tract OM or fibre digestibility.

Ethiopia is one of the countries most vulnerable to the impacts of climate variability and change on agriculture. The present study aims to understand and characterize agro-climatic variability and changes and associated risks with respect to implications for rainfed crop production in the Central Rift Valley (CRV). Temporal variability and extreme values of selected rainfall and temperature indices were analysed and trends were evaluated using Sen's slope estimator and Mann–Kendall trend test methods. Projected future changes in rainfall and temperature for the 2080s relative to the 1971–90 baseline period were determined based on four General Circulation Models (GCMs) and two emission scenarios (SRES, A2 and B1). The analysis for current climate showed that in the short rainy season (March–May), total mean rainfall varies spatially from 178 to 358 mm with a coefficient of variation (CV) of 32–50%. In the main (long) rainy season (June–September), total mean rainfall ranges between 420 and 680 mm with a CV of 15–40%. During the period 1977–2007, total rainfall decreased but not significantly. Also, there was a decrease in the number of rainy days associated with an increase (statistically not significant) in the intensity per rainfall event for the main rainy season, which can have implications for soil and nutrient losses through erosion and run-off. The reduced number of rainy days increased the length of intermediate dry spells by 0·8 days per decade, leading to crop moisture stress during the growing season. There was also a large inter-annual variability in the length of growing season, ranging from 76 to 239 days. The mean annual temperature exhibited a significant warming trend of 0·12–0·54 °C per decade. Projections from GCMs suggest that future annual rainfall will change by +10 to −40% by 2080. Rainfall will increase during November–December (outside the growing season), but will decline during the growing seasons. Also, the length of the growing season is expected to be reduced by 12–35%. The annual mean temperature is expected to increase in the range of 1·4–4·1 °C by 2080. The past and future climate trends, especially in terms of rainfall and its variability, pose major risks to rainfed agriculture. Specific adaptation strategies are needed for the CRV to cope with the risks, sustain farming and improve food security.

1. Eighteen determinations of the energy retention of six sheep were made when they were given the same batch of dried grass in the form of chopped material or as cubes. The cubes were made following hammer milling to a medium and fine particle size. The fasting heat production of each sheep was also determined, following subsistence on a standard ration.

2. Agreement between determinations of energy retention calculated from the carbon and nitrogen retentions and from the energy exchange was good. The mean discrepancy was 4 Cal./24 hr.

3. There were no statistically significant differences in energy retention as between the three materials at either a low (600 g./24 hr.) or a high (1500 g./24 hr.) level of feeding. Calculations of net energy/100 Cal. of food ingested showed that higher values occurred at the lower level of feeding. Standard errors of the means were small, about ±3% of the determined values. Further analysis showed that no large differences in the net energy value of the materials would appear within the normal feeding range, but slight extrapolation of the data indicated that the cubes would be superior at high feeding levels.

4. Faecal losses of energy were considerably greater when cubes were given and methane losses were much smaller. Individual sheep which showed low methane losses also showed high faecal energy losses. Faecal losses of energy were smaller at the lower feeding level. Urine energy losses were unaffected by the amount or physical form of the food given.

5. Heat losses were greater at the higher nutritional level and were considerably less for cubes than for chopped material. Constancy of net energy value in this study thus involved compensation of high faecal energy losses by low losses of energy as heat and methane.

6. The determinations of the digestibility of the carbohydrate fractions of the grass showed that a fall in the digestibility of the structural components of the cell was the major factor causing increased faecal losses. The digestibility of intracellular constituents fell very much less.

7. It is shown that evaluation of the grasses in terms of metabolizable or digested energy does not place them in their correct physiological order of nutritive value, and that estimates of nutritive value using Kellner's and other factors do not give their true nutritive worth.

8. It is pointed out that physical factors, which change the rate of passage of food through the gut, change the rate and nature of the microbial fermentation, and cause variation in the mechanical work involved in prehending, masticating and cudding food, are as important as the chemical composition of the food in determining its nutritive value.

A collection of 26 wheat genotypes widely grown in Spain during the 20th century was evaluated in eight contrasting environments in order to quantify breeding achievements in yield and associated traits. From 1930 to 2000, yield increased at a rate of 35·1 kg/ha/yr or 0·88%/yr, but estimations of relative genetic gain (RGG) were environment-dependent. RGG estimated for yield were positively associated with the average minimum daily temperatures from sowing to heading in the testing environments (R2 = 0·81; P < 0·01). The number of grains/spike and the number of spikes/m2 increased at a rate of 0·60%/yr and 0·30%/yr, respectively, while grain weight remained unchanged. The present study detected two main episodes of yield improvement during the century. The first one coincided with the introduction, during the 1950s, of the first improved cultivars derived from intra-specific crosses, which increased the yield of landraces by 30% due to an increase of c. 58% in the number of grains/spike, accompanied by a 16% reduction in grain weight. These initial cultivars (termed ‘old-bred’ in a previous study by Sanchez-Garcia et al. 2012) exhibited a higher harvest index (HI), increased from 0·25 to 0·40, but maintained the same aboveground biomass at maturity as the landraces (despite reducing both plant height and the number of tillers/plant) due to increases in the proportion of tillers bearing spikes. The second yield gain occurred after the introduction, in the early 1970s, of semi-dwarf germplasm from CIMMYT (International Maize and Wheat Improvement Centre) and some French cultivars. This new germplasm further reduced plant height, improved HI up to 0·45 and increased the number of tillers/plant while maintaining their rate of fertility, thus resulting in a yield gain of c. 37%. The cultivars released during the last decade of the century did not contribute to significant yield improvements.

Four groups of eight sheep, 4 months of age and reared parasite-free from birth, were used to investigate the effect of the abomasal parasite Ostertagia circumcincta on the intake and efficiency of utilization of food. One group (CI) was killed initially as control. Two further groups (ALC and ALI) were offered ad libitum a complete ruminant diet. The ALI group was dosed daily for 14 weeks with 4000 infective larvae. Sheep in a further group (PF) were individually paired to members of the ALI group and offered the same amount of food as was consumed by their pair. Balances of N, Ca and P, and the digestibility of energy and N were determined for the ALI and PF groups during weeks 2–3, 7–8 and 12–13. After 14 weeks of dosing the sheep were killed and the bodies of these and the CI sheep analysed for water, fat, N, Ca and P contents.

Parasitism caused a 20% reduction of food intake by week 2 which was maintained throughout the experiment. Apparent digestibility of nitrogen was reduced from 60 to 44% at weeks 2—3 but subsequently showed a gradual recovery. Nitrogen balances of infected sheep were inferior to those of controls which, with the exception of the first trial during which urinary N excretion of infected sheep was increased, was entirely related to the reduced digestibility. Energy digestibility was reduced by 2 percentage units during all trials.

Weight gain of ALI sheep was only 80% of that of PF sheep. Nitrogen anabolism was reduced by parasitism, but pair-feeding showed that reduced food intake rather than a specific effect on protein metabolism was responsible. Fat deposition was markedly reduced. It was calculated that the gross efficiency of utilization of metabolizable energy for growth was reduced by 30% compared with either ALC or PF controls.

Mineral deposition (Ca or P) in the skeleton of the ALI sheep was reduced to about 35 and 50% of that in ALC and PF groups, respectively.

A field experiment was conducted for two years (1994–96) to evaluate three nitrogen fixing bacteria (NFBs) namely Azotobacter, Azospirillum and Beijerinckia as foliar biofertilizers on mulberry (Morus spp.). Foliar application of these bacteria in their specific culture media with half of the recommended dose of N as a basal application of chemical fertilizer were compared with the recommended dose of N (300 kg/ha per year in four equal splits) but without biofertilizer. Other controls for comparison were respective culture media with half N. All the NFBs improved leaf yield over their respective controls (specific culture media). The addition of Azotobacter resulted in significantly greater yield than that given by the recommended dose of N. The Beijerinckia treatment resulted in a leaf yield equal to that from the recommended dose of N and Azospirillum reduced leaf yield in comparison to that from the recommended N treatment although the yield from Azospirillum treatment was more than that from the culture medium treatments. A combination of NFBs where Azotobacter was one of the components improved leaf yield over single NFB treatments. NFBs also resulted in improved leaf quality as indicated by their protein content and their impact on silkworm rearing and cocoon production when treated leaves were subjected to bioassay. The use of these NFBs, particularly the Azotobacter, as a foliar biofertilizer to increase mulberry leaf production has not been investigated before.

Avalon winter wheat was grown in 1983 on a light-textured, sandy loam (Cottenham series) which had a subsoil pan with a maximum dry bulk density of 1·8 g/cm3 at 35 cm depth. This was destroyed on part of the site with a ‘Wye Double Digger’ so that crop growth in panned and pan-free soils could be compared. The interaction of the pan with soil water supply was studied by sheltering the crops during May, June and July and either withholding water completely or irrigating weekly back to field capacity.

The pan had a major effect on the vertical extension rate of the root system as monitored both by coring and from observation tubes. Roots were largely confined above the pan until March, but compensatory growth occurred within this soil layer and the total length of root was unaffected. At anthesis, roots had reached a maximum depth of 100 cm in the panned soil compared with 140 cm in the pan-free soil.

Early shoot growth and N content were substantially reduced by the pan because of the inaccessibility of mineral N in the subsoil. However, both the growth of the crop and N uptake recovered following top dressings of N fertilizer and, when water was not limiting, the pan had a negligible effect on grain yield.

Root and shoot growth were reduced by the fixed shelter, but the imposed drought did ot affect water use by the crops until after anthesis when the root systems were already fully developed. Without irrigation, the crop growing on the double-dug soil yielded 5% more than that growing on the panned soil, but there was no evidence for extra water use from the subsoil by the former crop. The best treatment (double-dug with irrigation) outyielded the worst (panned soil with drought) by 8%.

A comprehensive study of how age and weaning affect intestinal structure and enterocyte ability to digest and absorb nutrients has been carried out in 4- and 6-week-old piglets.

Villus length, which did not change significantly in unweaned piglets 4–6 weeks after birth, was halved 5 days after weaning. Crypt depth, which increased normally in unweaned piglets, is further increased by weaning in both 4- and 6-week-old animals.

Lactase activity, which decreased normally with age, was inhibited more than a-glucosidase by weaning. Weaning of 6-week-old piglets also caused a significant increase in maltase II and III activities. Alkaline phosphatase activity was unaffected by age or weaning in 4- and 6-week-old piglet intestine.

Na-dependent alanine transport was reduced in 6- compared with 4-week-old unweaned piglet intestine. Weaning inhibited Na-dependent alanine transport in 4- but not 6-week-old pigs. Na-independent alanine transport, which was considerably less than that found in the presence of Na, was not noticeably affected by age or weaning.

Weaning-induced problems in intestinal function appear from the present results to be caused more by changes in intestinal structure and specific loss of digestive enzymes rather than by any gross change in absorptive function. The possible role of immune as well as nutritional factors in causing these weaning-dependent changes in intestinal function is discussed.

A series of laboratory silages were prepared and opened after 2, 20, 60 and 150 days. The silages were made without any additive and with formaldehyde, formic acid, hexanoic acid, benzoic acid or sulphuric acid. The cellulose, hemicellulose, acetyl, alkali-labile phenolic acids and core lignin were determined in all silages as well as the composition of the hemicelluloses. In all the silages, the core lignin remained unchanged while the cellulose content only decreased by up to 5%. Large losses of acetyl residues and alkali-labile phenolic acids were observed in all the silages and losses of 10–20% of the hemicelluloses were found. The losses of hemicellulose were not uniform. The arabinose side chains were preferentially cleaved relative to the xylose residues. It was shown that part of the loss of carbohydrate could have been caused by the acidic conditions in the silage as well as by microbial activity. The silages made using the acidic additives with the highest pKa values lost the greatest proportion of carbohydrate. The implications of these results on rumen activity are discussed.

Understanding and predicting small-grain cereal development is becoming increasingly important in enhancing management practices. Recent efforts to improve phenology submodels in crop simulations have focused on incorporating developmental responses to water stress and interpreting and understanding thermal time. The objectives of the present study were to evaluate data from three experiments to (a) determine the qualitative and quantitative response of wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) to water stress and (b) ascertain where in space to measure temperature, to provide information required to improve phenological submodels. The first experiment tested the phenological responses of 12 winter wheat cultivars to water stress for two seasons at two sites. The second experiment tested the timing of water stress on spring barley phenological responses for 2 years. In a third experiment, soil near the shoot apex of field-grown spring wheat was heated to 3°C above ambient soil temperature for three planting dates in each of 2 years, to test whether it is better to use soil or air temperature in calculating thermal time. The general response of wheat and barley to water stress was to reach growth stages earlier (i.e. to hasten development). The most significant response was for the grain filling period. Water stress had little effect on jointing and flag leaf complete/booting growth stages. Thermal time to jointing was highly variable across locations. However, thermal time to subsequent growth stages was very consistent both within and across locations. The winter wheat cultivars tested followed this general response across site-years, but inconsistencies were found, suggesting a complicated genotype by environment (G×E) interaction that makes improving phenology submodels for all cultivars difficult. The G×E interaction was most prominent for anthesis (A) and maturity (M) growth stages. Results of heating the soil at the shoot apex depth were completely unexpected: heating the soil did not speed spring wheat phenological development. These results, and others cited, suggest caution in allocating effort and resources to measuring or estimating soil temperature rather than relying on readily available air temperature as a means of universally improving phenology submodels. These results help quantify the response of wheat to water stress and thermal time for improving crop simulation models and management.

Eighty Friesian heifers were used to study the effect on milk production of two fixed levels of intake at two stages of the lactation. The rations were estimated to contain 7·9 and 6·2 kg starch equivalent per day, with adequate protein content. The heifers were allocated at random to these two levels of intake for weeks 1·9 of lactation and re-allocated at random to them for weeks 10–18 of lactation. Apart from minor variation the heifers were all fed alike for the remainder of the lactation.

The higher level of feeding increased yields of milk and milk solids and solids-not-fat content in each period but had a smaller effect in mid- than in early lactation, a trend which was shown to continue further into later lactation. It also conserved body reserves.

There was a residual effect in weeks 10–18 from the level of feeding in weeks 1–9 of lactation. This was directly additive to the effects of the current level of feeding. Those animals which had received the higher level of feeding in weeks 1–9 yielded more milk of higher solids-not-fat content than those which had had the lower level of feeding in weeks 1–9. The former group gained less live weight. The effect on milk production over the full lactation from additional feeding in early lactation was three times that observed in early lactation itself. Additional feeding in mid-lactation did not have a residual effect.

The absolute output of milk per unit of food over the 18-week period was greatest for that group which had received the lower level of feeding throughout, followed by the group which received the higher level of feeding in weeks 1–9 only. This superiority was achieved at the expense of body reserves. There was a negative regression of live-weight change on milk production.

Estimated intakes of metabolizable energy agreed closely with requirements for milk production as indicated by the Agricultural Research Council (1965).

A series of irrigation experiments was done at Rothamsted where the soil is a flinty silty clay loam over flinty clay. The results are compared with those obtained by Penman (1962, 1970, 1971) at Woburn where the soil is a loamy sand over sand. The limiting deficits, Di, above which irrigation increased yields, were about 2·5 times greater at Rothamsted than at Woburn; this ratio approximates to the ratio of the water-holding capacities of the soils (– 0·1 to – 15 bar) to a depth of 1 m. The limiting deficits at Rothamsted were 80 mm for spring-sown field beans, 84 mm for main-crop potatoes, 100 mm for spring barley and 140 mm for spring and winter wheat. The responses to irrigation were not determined accurately as there were few years with a large response for any crop. However, the evidence is that the maximum response that could be expected for potatoes was 0·19 t/ha/mm water, and for grain dry matter of beans 0·006 t/ha/mm. The figure for potatoes agrees with that obtained by Penman at Woburn; the response of beans was much smaller at Rothamsted, partly because of severe attacks of broad bean stain virus.

Globally, agriculture accounts for 0·80–0·90 of all freshwater used by humans and, in many crop production systems, this water use is unsustainable. The current paper focuses on the potential exploitation of novel drought stress biology in both crop improvement programmes and via changed crop management practices. The aim is to deliver ‘more crop per drop’. In order to respond to the challenge of feeding a world population of seven billion and growing, it is concluded that an interdisciplinary approach is needed involving new genetic opportunities and plant breeding. It is also shown how crop management can exploit the drought stress physiology of plants to deliver improved water productivity without sacrificing crop yield.

Pig and cow slurries were applied to bare soil surfaces in the laboratory. Volatilization of NH3 was measured using ventilated enclosures for 3·25 days after slurry application. Slurries were acidified to pH values between 7 and 4 with 5 M H2SO4. Lowering cow slurry pH to 5·5 decreased NH2 volatilization by 95%, while lowering pig slurry pH to 6·0 decreased NH3 volatilization by 82%. A field experiment, measuring the volatilization of NH3 for 2 h after application to grassland stubble of slurry acidified to pH values between 7·5 and 5, gave similar results to the laboratory study.

Titration curves were constructed within the pH range of 9 to 4 with cow and pig slurries. There was a significant (P < 0·05) positive correlation between the NH4+-N content of the slurries and the volume of acid required to attain a target pH of 6·0 for pig slurries and a pH of 5·5 for cow slurries. One litre of slurry containing 2 g of NH4+-N required c. 20 ml of 5 M H2SO4 for acidification.

1. Previous work on the validity of the t and z tests on non-normal distributions is described. The question as to whether these tests, which are all on small samples from theoretical distributions, are really apposite is discussed.

2. The necessity of making a practical test with actual data which shall comply with the usual conditions obtaining in agricultural experiments is urged.

3. A practical test has been made on a skew distribution obtained from the observation of 256 height measurements on wheat. The distribution of the values of R. A. Fisher's z from a thousand random samples has been obtained and found to agree satisfactorily with the theoretical distribution.

1. Three species of grass, rye-grass (two varieties, S 23 and S 24) cocksfoot (variety S 37) and timothy (variety S 48) were cut at various stages of maturity, dried and given at several planes of nutrition to sheep in respiration chambers. The detailed chemical composition of the grasses and the apparent digestibility of the constituents were studied.

1. The volume of rumen liquor in milk-fed calves at different ages up to 32 weeks was estimated by injecting polyethylene glycol into the rumen and subsequently determining its concentration in the rumen liquor. This volume increased progressively with age in relation to unit body weight. The increase xswas approximately fourfold between 4–8 weeks on the one hand and 28–32 weeks on the other.

2. The amount of milk entering the rumen during a feed was estimated at different ages up to 32 weeks by the subsequent determination of the volume and fat content of the rumen liquor. In the majority of cases less than 5% of the milk fed entered the rumen. There did not appear to be any increase in the quantities of milk entering the rumen as the calves got older.

3. An estimate of the rate of flow of fluid into and out of the rumen (other than milk at feeding) was made by measuring the rate of disappearance of polyethylene glycol from the rumen. A mean figure of 255 ml./hr./100 kg. body weight s.d. ± 50 was obtained in this way. It is suggested that this value probably represents the rate of flow of saliva.

4. Magnesium, in a concentration up to about 8 mg./100 ml. in the rumen liquor, did not appear to be absorbed to more than a small extent through the rumen wall.