Eight amounts of nitrogen ranging from 0 to 210 kg N/ha were applied to two tall and one semi-dwarf variety of winter wheat in the spring of 1975 and 1976. The tall varieties were Cappelle-Desprez and Maris Huntsman; the semi-dwarf variety was Maris Fundin in 1975 and Hobbit in 1976. Interactions between varieties and nitrogen were few and small compared with the main effects. All varieties produced their maximum grain yields with 180 kg N/ha. The yield of the semi-dwarf varieties, but not the others, decreased slightly with more nitrogen.

Cappelle-Desprez yielded less grain than the other varieties in both years. In 1975 the yields of Maris Fundin and Maris Huntsman were similar and in 1976 Hobbit yielded more than Maris Huntsman. The varieties had similar numbers of ears at maturity and similar patterns of tillering. The semi-dwarf varieties had most grains per spikelet, and hence grains per ear, and Cappelle-Desprez had least. The semi-dwarf varieties had the smallest grains. The semi-dwarf varieties had less straw than the other varieties and hence the largest ratios of grain to total above-ground dry weight. The decrease in dry weight of stem and leaves between anthesis and maturity was similar for all varieties. In 1975 the efficiency of the top two leaves plus top internode in producing grain was the same for all varieties, but in 1976 Hobbit was more efficient than the other two. There were some small differences between varieties in nutrient uptake that were not related to differences in growth. Maris Fundin tended to have a greater phosphorus and potassium content than the tall varieties. Hobbit contained slightly less nitrogen than the tall varieties at maturity, and had a smaller concentration of nitrogen in the grain.

Applying 210 kg N/ha doubled grain yield in 1975. Applying nitrogen resulted in a largeincrease in number of ears and a small increase in number of grains per ear due to the development of more fertile spikelets per ear. Nitrogen decreased dry weight per grain, especially of the semi-dwarf varieties. With extra nitrogen, straw dry weight at maturity, shoot dry weight atanthesis and leaf area were all increased relatively more than grain yield, and stems lost moredry weight between anthesis and maturity than without nitrogen. The year 1976 was exceptionallydry and nitrogen had only small effects in that it affected neither straw dry weight nor numberof ears but slightly increased grain yield by increasing the number of spikelets and number of grains per spikelet. It also increased leaf area proportionately to grain yield. In 1975 nitrogen increased evaporation of water from the crop before anthesis but decreased it after anthesis, even though it continued to increase the extraction of water from below 90 cm.

Two experiments compared yields of spring barley following barley, oats, beans (Vicia faba), red clover (cut) and (one experiment only) oil-seed rape, and tested effects of trefoil (Medicago lupulina) undersown in the preliminary crops of barley and oats. N fertilizer was applied at two rates to preliminary crops, and four rates to the final crop in each experiment. Barley following barley suffered severely from take-all disease (Gaeumannomyces graminis var. tritici); barley after other crops was little affected. Other recognized soil-borne diseases were unimportant. Barley yielded less after barley than after other crops except where excessive N fertilizer caused lodging. Clover and beans left N residues equivalent to about 88 and 44 kg fertilizer N/ha respectively; undersown trefoil left inconsistent N residues. Couchgrass (Agropyron repens) was more prevalent after barley than after other crops.

The ammoniacal nitrogen in the Rothamsted rainwater amounts on an average to 0·405 part per million, corresponding to 2·64 lb. per acre per annum. The yearly fluctuations in lbs. per acre follow the rainfall fairly closely. The monthly fluctuations also move in the same direction as the rain, but the general level is highest during May, June, July and August, and lowest during January, February, March and April (Tables 1, 2, 3, and Figs. 1 and 2).

The nitric nitrogen is on an average one-half the ammoniacal, viz., 1·33 Ib. per acre per annum. The amounts fluctuated year by year and month by month in the same way as the ammoniacal nitrogen and the rainfall until 1910, since when there has been no simple relationship (Tables 1, 2, 3, and Figs. 1 and 2).

Reasons are adduced for supposing that the ammonia arises from several sources. The sea, the soil, and city pollution may all contribute. Neither the sea nor city pollution seems able to account for all the phenomena: the soil is indicated as an important source by the fact that the ammonia content is high during periods of high biochemical activity in the soil, and low during periods of low biochemical activity.

The efficiency of visual selection in a glasshouse of 1600 seedlings compared with visual selection in the field of the same clones is examined. Also the amount of agreement in assessment between four different potato breeders screening the same clones is investigated. Seedlings were grown from true seed in four-inch pots in a glasshouse and all the clones which produced tubers were grown in the field the following year. Clones which produced more than one tuber from a seedling were grown at two locations in the first clonal year. One of the sites used in the first clonal year is normally used for potato yield trials (i.e. a ware site) and the other is normally used for the production of healthy seed tubers (i.e. a seed site). In all three environments, the tubers produced from each plant were assessed by four breeders independently on a 1–9 scale of increasing attractiveness.

From the data it was found that the repeatability of assessment between the glasshouse and the first clonal year was low in that the correlation between the average preference score of the four breeders in the glasshouse and each of the two first clonal year sites accounted for only 8·24 and 6·84% of the total variation. Many clones which had low scores in the glasshouse were subsequently given high scores in the first clonal year. It was therefore concluded that selection of seedlings was not very efficient. Although, in general, the weight of the tuber that was planted greatly influenced whether a clone was selected in the first clonal year, a large number of clones which produced only small tubers in the glasshouse were subsequently selected in the first clonal year.

Within each environment the four breeders were either all selecting, or all rejecting, a much higher proportion of clones than would be expected if selection had been made completely at random. The breeders were in most agreement when assessing clones at the ‘ware’ site, and in most disagreement when assessing them grown in the glasshouse from true seed. Therefore the poor efficiency of selection of seedlings grown in the glasshouse was not, in the main, a result of a high error variance in visual assessment but rather due to poor association between the performance of seedlings and first clonal year plants.

The follicle population of the Blackface breed (‘double-coated’) was followed in skin samples taken from four lambs at eight intervals between 3 days and 43 weeks of age. The follicle population differs greatly from that of the Romney and Leicester breeds previously studied (Burns, 1949).

1. At 1 month old the secondary/primary follicle ratio (S/P) was slightly lower than the Leicester and much lower than the Romney, and the difference became accentuated with age.

2. Fewer secondary follicles are developed after birth than in the Leicester or Romney, although the period during which they can be developed is longer, extending at least to 12 and possibly to 17 weeks after birth.

3. The follicle density is less than half that of the Leicester, but the difference in S/P ratio is not sufficiently large to account for this, which is mainly due to the Blackface having a much lower density of primary follicles at birth.

4. The possibility is suggested that the secondary follicles arise as a result of ‘induction’ by ‘follicle organizer’ coming from primary follicles in a quantity which decreases with advancing age. It may be that when the primary density is high the areas affected by organizer from each primary overlap, providing sufficient organizer to permit of numerous secondary follicles developing at a late post-natal stage, as reported in the Merino.

5. The Blackface contrast with the other breeds in that its primary follicles are conspicuously larger than its largest secondary follicles. All primary fibres are medullated except when about to shed, but many secondary fibres are free of medulla. Kemps are produced only by primary follicles, some of which however produce long ‘hair’ fibres.

6. Many fibres which grow strongly medullated fibres during summer change to the production of non-medullated fibres in winter. The shedding of the kemps in spring should probably be looked upon as physiologically an autumn moult, since the fibres cease growth and produce ‘brushes’ during the autumn.

Treatment effects on levels of soil carbon and nitrogen in four long-term experiments at Samaru are reviewed in relation to an expected change in the future away from a bush-fallowing agricultural system towards an intensive mechanized system of permanent agriculture.

Where different rates of farmyard manure were applied to the soil annually for nearly 20 years marked differences in soil organic matter contents developed. The mean soil carbon (0·82 per cent) of plots that received 12·5 tonnes ha-1 annum-1 is now almost four times as great as the mean content (0·22 per cent) of control-plot soils. Phosphate applications tended to encourage higher levels of soil organic matter, but where mineral fertilizers (N, P and K) were applied with farmyard manure lower soil organic matter levels and C:N ratios than those of manure-only plots resulted. Apparent retention in the soil of carbon and nitrogen applied as farmyard manure was of the order of 12–15 and 30% respectively. A groundnut shell mulch, applied for 9 years, produced significantly higher levels of soil organic matter than control plots.

In a rotation experiment in which three years of cropping alternated with either 2, 3 or 6 years of planted Gamba grass (Andropogon gayanus) fallow, large differences in soil organic-matter status and rate of turnover existed between the three rotations. In particular the 3-year fallow showed an annual rate of soil organic-matter increase over twice that of the 2-year fallow. Soil nitrogen build-up exceeded 50 kg ha-1annum-1 in the 3-year fallow.

Shortage of farmyard manure and the relatively poor return from systems that include unproductive fallows suggest that in future soil organic matter must be maintained by the return to the soil of all crop residues.

A dry-block digestion system suitable for the estimation of total protein nitrogen in plant material has been evaluated. The method was found to be as accurate as Kjeldahl flask digestion, required much less fume cupboard space and enabled samples to be dealt with in large batches through weighing, digestion and analysis. The batch size can be designed to be compatible with the autoanalyser capacity. These advantages result in more rapid analysis with less chance of errors and accidents. A 45 min digestion period was found suitable for several crop species of widely different protein content, only field bean seeds required longer digestion time. Using the technique described samples are digested at a relatively low temperature (330 °C) for a short time and digests do not solidify on cooling. The autoanalyser method for determining ammonia concentrations in barley and malt digests (Micheson & Stowell, 1970) has been slightly modified for use with the plant materials studied. The dry-block and autoanalyser system is rapid, precise and compact, requires small amounts of tissue and is suited to the routine analysis of breeding material.

Common bean (Phaseolus vulgaris L.) is the most important food legume for human consumption. Drought stress is the major abiotic stress limitation of bean yields in smallholder farming systems worldwide. The current work aimed to determine the role of enhanced photosynthate mobilization to improve adaptation to intermittent and terminal drought stress and to identify a few key adaptive traits that can be used for developing drought-resistant genotypes. Field studies were conducted over three seasons at Centro Internacional de Agricultura Tropical, Palmira, Colombia to determine genotypic differences in adaptation to intermittent (two seasons) and terminal (one season) drought stress compared with irrigated conditions. A set of 36 genotypes, including 33 common bean, two wild bean and one cowpea were evaluated using a 6 × 6 lattice design under irrigated and rainfed field conditions. Three common bean elite lines (NCB 226, SEN 56, SER 125) were identified with superior levels of adaptation to both intermittent and terminal drought stress conditions. The greater performance of these lines under drought stress was associated with their ability to remobilize photosynthate to increase grain yield based on higher values of harvest index, pod harvest index, leaf area index and canopy biomass. Two wild bean germplasm accessions (G 19902, G 24390) showed very poor adaptation to both types of drought stress. One small-seeded black line (NCB 226) was superior in combining greater values of canopy biomass with greater ability to mobilize photosynthates to grain under both types of drought stress. Two small-seeded red lines (SER 78, SER 125) seem to combine the desirable traits of enhanced mobilization of photosynthates to seed with effective use of water through canopy cooling under terminal drought stress. Pod harvest index showed significant positive association with grain yield under both types of drought stress and this trait can be used by breeders as an additional selection method to grain yield in evaluation of breeding populations for both types of drought stress.

Crop production is at the core of a ‘perfect storm’ encompassing the grand challenges of achieving food and nutrition security for all, in the face of climate change, while avoiding further conversion of natural habitats for agriculture and loss of biodiversity. Here, we explore current trends in crop modelling related to these grand challenges by reflecting on research presented at the Second International Crop Modelling Symposium (iCropM2020). A keyword search in the book of abstracts of the symposium revealed a strong focus on ‘climate change’, ‘adaptation’ and ‘impact assessment’ and much less on ‘food security’ or ‘policy’. Most research focused on field-level investigations and far fewer on farm(ing) systems levels – the levels at which management decisions are made by farmers. Experimentation is key to development and testing of crop models, yet the term ‘simulation’ outweighed by far the terms ‘experiments’ and ‘trials’, and few contributions dealt with model improvement. Cereals are intensively researched, whereas roots, tubers and tropical perennials are under-researched. Little attention is paid to nutrient limitations apart from nitrogen or to pests and diseases. The aforementioned aspects represent opportunities for future research where crop models can help in devising hypotheses and driving new experimentation. We must also ensure that crop models are fit for their intended purposes, especially if they are to provide advice to policymakers. The latter, together with cross-scale and interdisciplinary efforts with direct engagement of stakeholders are needed to address the grand challenges faced by food and agricultural systems in the next century.

Agriculture can benefit substantially from long-range weather forecasts, for the month or the season, which can help to optimize farming operations and deal more effectively with the adverse impacts of climate variability, including extreme weather events. In the context of climate change, long-range weather forecasts also represent key elements for the development of adaptation strategies. In spite of an undeniable potential, long-range forecasts issued for instance by the European Centre for Medium-Range Weather Forecasts (ECMWF) have yet to find widespread application in European agriculture. To address partially the question of why this is the case, the performance of the ECMWF monthly ensemble forecasting system was examined. It was noted that predictability is currently limited to about 3 weeks for temperature and 2 weeks for precipitation and solar radiation. This may appear deceptive at first sight, but it was noticed that precipitation forecasts over a month are, overall, at least as valuable as information obtained from observed climatology. Encouraged by this finding, the possibility of using monthly forecasts to predict soil water availability was tested. In an operational context, this could serve as a basis for scheduling irrigation. Positive skills were found for lead times of up to 1 month. It was concluded that more systematic investigations of the possibilities offered by long-range forecasts should be undertaken in the future. However, this will require additional efforts to increase the quality of the forecasts, design appropriate application tools and promote the dissemination of the outcome within the agriculture community.

1. A method is described by which it is possible to estimate the numbers of active protozoa in a soil.

2. The total number of protozoa is first found by a dilution method. A fresh portion of the soil is then treated with 2 per cent. HCl (sp. gr. 1·15) overnight. By this means all active forms are killed. A second count by the dilution method gives the number of cystic protozoa in the soil. From these results the number of active forms can be ascertained.

Root and shoot growth and nutrient uptake have been monitored for several winter wheat crops which gave a mean grain yield of 9·5 t/ha (85% D.M.) when grown on three soil types in 1980 and 1981. Averaged over all crops, maximum growth rates were 170 kg/ha/day for shoots and 14 kg/ha/day for roots; maximum nutrient uptake rates for N, P, K, Ca and Mg were 2·75, 0·47, 341, 0·60 and 0·18 kg/ha/day respectively. Maximum uptake of K and Ca occurred at anthesis with values of 239 and 38 kg/ha respectively, whilst for the other nutrients maximum uptake was at final harvest with values of 200, 39 and 14 kg/ha for N, P and Mg respectively. The grain contained 141 kg N, 27 kg P, 41 kg K, 3·2 kg Ca and 7·1 kg Mg/ha.

The quantity of nutrients arriving at root surfaces by mass flow was calculated for one of the crops from measurements of soil solution concentration and potential evapotranspiration data. The potential supply of nutrients by mass flow, as a percentage of that actually taken up between 19 March and 29 June, was 25% for N, 4% for K, 800% for Ca and 32% for Mg.

The spring wheat varieties Kolibri, a typical north temperate variety, Pitic 62, a Mexican variety known to respond to vernalization and two selections from the Institute's breeding programme TW 161 and TJB 155 were sown early (2–5 March), during the normal sowing period (27 March) and late (17 April). Primordium initiation was observed until the time of terminal spikelet initiation and the number of leaves and the number of spikelets were analysed in terms of rate and duration of leaf and spikelet primordium initiation. The rate of leaf initiation was affected by time of sowing but not in a systematic way and there were differences between varieties in the way in which the number of leaves changed in response to sowing time. The rate of spikelet initiation increased and the duration decreased with later sowing. There were strong variety × time of sowing interactions. For almost all characters measured, Pitic 62 responded least to time of sowing. Varieties differed in the way in which the number of spikelets per ear responded to time of sowing but in all cases the changes were only small. This waa because the change in the rate of spikelet initiation was almost exactly compensated for by a change in the duration of spikelet initiation. In each variety, the period from terminal spikelet initiation to ear emergence was similar in all sowing treatments and was of similar duration in the main shoot and in the ear-bearing tillers.

The number of leaves per shoot on the tillers was less than the number of leaves on the main shoot and the rate of spikelet primordium initiation of the tillers was faster than in the main shoot. These changes tended to synchronize the time of terminal spikelet initiation. Because of the changes in the number of leaves per shoot and the rate of spikelet initiation the number of spikelets borne on the main shoot and the tillers were similar although the growth period of the tillers was shorter than that of the main shoot.

Wheat, barley and two morphologically contrasting cultivars of peas (leafy and semi-leafless) were grown in pure stands, at standard agricultural densities, and in additive mixtures of cereals with peas. The stands were grown in boxes in the field, and partitions were used to separate the effects of root and shoot interactions. The cereals and peas were either planted at the same time, or one species was planted 10 days before the other. The origin of the N present in each species was determined by applying N fertilizer labelled with 15N.

Both cultivars of peas had greater shoot and root competitive abilities than wheat or barley, probably because of their larger seed size; leafy peas had greater shoot and root competitive abilities than semi-leafless peas. Sowing peas after cereals reduced their competitive ability.

The relative yield total (RYT) of cereal-pea mixtures, based on total biomass, averaged 1·6 when only the root systems interacted, and 1·4 when only the shoot systems interacted, but did not differ significantly from 10 when both root and shoot systems interacted. RYT values were greater when peas were grown with wheat, rather than with barley, and when peas were sown at the same time as the cereals.

Shoot competition from peas increased the N% of cereals, but substantially reduced their total N content, because biomass yield was reduced. Shoot competition from cereals had no effect on the N% of peas, and only slightly reduced their total N content. Shoot competition between cereals and peas had no significant effect upon the proportion of N derived from various sources by either cereals or peas.

Root competition from peas significantly reduced both the N% and total N content of cereals. Root competition from cereals had little effect on the N% of peas, but significantly reduced their total N content and increased the proportion of N derived from rhizobial fixation from 76 to 94%. Since cereals and peas largely used different sources of N, resource complementarity for N was probably an important component of intercropping advantage, when the roots of cereals and peas shared soil resources.

The structure, distribution and dimensions of skin strata and sweat glands have been investigated in Egyptian buffaloes and cattle. Samples from sixteen body regions were taken from three adult bulls of both species. Identical studies were also made on one buffalo calf and two buffalo embryos. Serial vertical and horizontal sections were cut from each body region using the ‘terpineol paraffin wax’ method. The following results were obtained.

1. Buffalo skin is characterized by dermal papillae enclosing papillomatous epidermis. The fibrous structure of the dermis is similar in both species. In buffaloes, the average thickness of skin, main epidermis, papillomatous epidermis, and cornium is 6·5 mm., 50, 115, and 11μ respectively. The epidermis coefficient is 12 for the main epidermis and 18 for the papillomatous epidermis. In cattle, the average thickness of skin, epidermis and cornium layer is 4·3 mm., 51 and 5 μ respectively, while the epidermis coefficient is 8.

2. The average number of hair follicles per sq.cm. of skin is 394 in the buffalo and 2633 in cattle. Each hair follicle is accompanied by two large lobulated sebaceous glands in the buffalo, and one small bilobed gland in cattle.

3. There is no species difference in the histology of the sweat glands. Each hair follicle is accompanied by one sweat gland in both species. In the buffalo, the body of the sweat gland is oval and convoluted, while the duct is twisted at its attachment to the body. In cattle, the body of the gland is elongated while the duct is straight. The number of sweat glands per sq.cm. of skin is 394 in the buffalo and 2633 in cattle. The dimensions of the sweat glands are larger in buffaloes than in cattle. The length, circumference and sweating surface of the gland is 0·58, 0·47, and 0·276 sq.mm. in the buffalo, and 0·47, 0·26, and 0·124 sq.mm. in cattle respectively. The glandular surface of sweat glands per sq.cm. of skin is 1·07 sq.cm. in the buffalo and 3·08 sq.cm. in cattle.

4. The type of sweat gland secretion is apocrine in both species. In the buffalo, successive stages of apocrine secretion are observed, and the merocrinelike form is rare. In cattle, the merocrine-like form prevails and the other stages are very rare. The theory (Findlay & Yang, 1950) of intraluminal transformation, of secretory products from coarse granularity to fluid homogeneity is supported. The effect of locality on the type of sweating activity is stressed.

5. There are species differences in the distribution of blood vessels and capillaries. In the subepidermal level, the arterial branches are more frequent and superficial in buffaloes than in cattle. Capillaries are found in the dermal papillae of buffalo skin. The capillary loops encircling the hair follicle are more frequent in cattle than in buffaloes. The blood capillaries supplying the sebaceous glands are more numerous in the buffalo than in cattle. The blood supply of sweat glands is poor in both species.

6. There are age differences in the skin histology. The number of hair follicles per sq.cm. of skin in a 5-months-old embryo, calf at birth, and adult buffaloes is 10560, 1248 and 400 respectively. There are no skin glands in the 1-month and 5-months-old embryos. The sweat gland in the calf is small in size and similar in structure to that of the adult. Calves have fewer sweat glands than adults.

7. The body conformation and the degree of pigmentation are affected by species, breed and locality.

8. The secreting activity of the sweat glands may be affected by the locality.

9. It seems that there are species differences in the mechanism of heat convection and radiation, insensible perspiration and sensible perspiration, due to histological differences.

Few reactions are more important to the soil chemist than that involved in the action of dilute acids on the phosphorus compounds of the soil, but, owing to its complex nature, little has been definitely ascertained about it. The importance of the reaction lies in the fact that it affords a distinction between those phosphorus compounds which are fairly easily soluble, and may therefore be expected to enter the plant root without much difficulty, and the less soluble compounds which are of less value in the nutrition of plants.

In a series of experiments in which variations in the level of carbohydrates in the plant have been brought about by means of short-term exposures to darkness and raised temperatures, it has been shown that:

1. The yield of leaf material after cutting is affected by pretreatments. This effect seems to be at least partly associated with the level of carbohydrates present in the stubble at the time of cutting.

2. The rate of growth of the plants is independent of the pretreatments imposed once growth is fully established.

1. Net pasture dry matter production and available pasture dry matter were measured over 3 years in a small-scale replica of the study of the effects of dairy cow grazing management and stocking rate reported by McMeekan & Walshe (1963).

2. The four treatments were

(i) Controlled rotational grazing, light stocking rate (0.95 cows/acre).

(ii) Controlled rotational grazing, heavy stocking rate (1.19 cows/acre).

(iii) Uncontrolled, set stocked grazing, light stocking rate (0.95 cows/acre).

(iv) Uncontrolled, set stocked grazing, heavy stocking rate (1.19 cows/acre).

3. The pasture measurement technique employed measured net pasture production (gains through new growth minus losses from all sources). It is argued that this parameter, rather than absolute pasture production, governs the changes in the dry matter feed supply to the grazing animal.

The effects of the anti-gibberellin triazole metconazole on yield, lodging resistance, seeds/m2 (sink size) and rooting in the presence of negligible amounts of disease were investigated using five multi-site experiments carried out in the UK between 1999 and 2007. The green area index (GAI) of the crop at the time of application had the greatest influence on the yield response across 173 comparisons between metconazole-treated and untreated crops. Crops with a GAI in March (growth stage (GS) 3·3–3·5 ‘green bud’) of 0·8–2·8, which represented moderate to large sized UK commercial crops, had an average response of +0·21 t/ha to metconazole applied at the full recommended rate of 1·2 litres/ha. Crops with a GAI of less than 0·8, which represented small commercial crops, had an average response of −0·14 t/ha. Applications between green bud and early flowering gave the greatest yield increase. Positive yield responses were associated with a reduction in lodging, or more seeds/m2, or a combination of both. The proportional area lodged was reduced by 0·1 for each 50 mm reduction in crop height (R2=0·60; P<0·001). Across six field trials, metconazole applied in spring increased root length density between soil depths of 0·40 and 1·00 m from an average of 0·478 to 0·601 cm/cm3 (P<0·05). It was estimated that this could increase yield by 0·2–0·3 t/ha in a dry season. The results show that the growth regulatory properties of metconazole can be used to improve several key aspects of growth that are believed to restrict current farm yields.

The Cornell-Penn-Miner (CPM) Dairy is an applied mathematical nutrition model that computes dairy cattle requirements and the supply of energy and nutrients based on characteristics of the animal, the environment and the physicochemical composition of the feeds under diverse production scenarios. The CPM Dairy was designed as a steady-state model to use rates of degradation of feed carbohydrate and protein and the rate of passage to estimate the extent of ruminal fermentation, microbial growth, and intestinal digestibility of carbohydrate and protein fractions in computing energy and protein post-rumen absorption, and the supply of metabolizable energy and protein to the animal. The CPM Dairy version 3.0 (CPM Dairy 3.0) includes an expanded carbohydrate fractionation scheme to facilitate the characterization of individual feeds and a sub-model to predict ruminal metabolism and intestinal absorption of long chain fatty acids. The CPM Dairy includes a non-linear optimization algorithm that allows for least-cost formulation of diets while meeting animal performance, feed availability and environmental restrictions of modern dairy cattle production. When the CPM Dairy 3.0 was evaluated with data of 228 individual lactating dairy cows containing appropriate information including observed dry matter intake, the linear regression between observed and model-predicted milk production values indicated the model was able to account for 79·8% of the variation. The concordance correlation coefficient (CCC) was high (rc=0·89) without a significant mean bias (0·52 kg/d; P=0·12). The accuracy estimated by the CCC was 0·997. The root of mean square error of prediction (MSEP) was 5·14 kg/d (0·16 of the observed mean) and 87·3% of the MSEP was due to random errors, suggesting little systematic bias in predicting milk production of high-producing dairy cattle. Based upon these evaluations, it was concluded the CPM Dairy 3.0 model adequately predicts milk production at the farm level when appropriate animal characterization, feed composition and feed intake are provided; however, further improvements are needed to account for individual animal variation.