1. Regression equations for the ratio of organic matter (O.M.) feed intake to O.M. faecal output on faecal N%, and the N% in the O.M. intake on faecal N% were established over a 52-week period by feeding caged Corriedale wethers on pasture cut from a Wimmera rye-grass (Lolium rigidum Gaud.), subterranean clover (Trifolium subterraneum) sward in a Mediterranean-type environment.

2. The regression equations and their application to grazing sheep together with the relation between O.M. intake and faecal N, are discussed.

Lactating Boran type zebu cows had high haemoglobin levels during the week after calving, after which these levels dropped sharply and then continued to decline more gradually until their calves were weaned. Some recovery was made during the subsequent dry period.

Cows fed 1 oz. dicalcium phosphate daily were constantly lower in blood haemoglobin level than their controls, and significantly so between the 14th and 20th weeks of the lactation. No differences were observed in weekly weight changes or in estimated milk yields.

Calf haemoglobins decreased gradually with age until relatively adult levels were reached at about a year of age. Initial content during the week of birth was lower than at a few weeks old. There was no difference in the blood haemoglobins of calves suckling on treated and untreated cows.

Individual variation was high in all groups. Some implications of seasonal effects and altitude are discussed.

1. To evaluate selection criteria in grass breeding, a series of investigations was conducted measuring plant performance in a wide range of field environments.

2. This paper reports on the behaviour of one variety of Lolium perenne, S. 24, grown in a logarithmically related series of densities and frequently defoliated for 2 years. Half the plots received only natural rainfall, the rest were irrigated so that the calculated soil moisture deficit did not exceed 2 in.

3. In 1958, with little effect of irrigation, swards yielded most per unit area, widest spacing (24 in.) least; there were no significant differences in yields from the other densities (3, 6 and 12 in.). In 1959, when yields were lower, irrigation increased production in all plots, the higher the density the greater the increase. In contrast to 1958, over the range of spaced densities, the higher the density the greater the yield. Individual harvests did not always conform to the annual pattern.

4. Lowest mean production per plant was from broadcast plots in both 1958 and 1959, yields of plants from 3, 6 and 12 in. plots showed a linear increase with a reduction in density, those from 24 in., though heaviest, yielded less than linear expectation. In 1959 irrigation increased yields per plant.

5. Of the components of yield, number of sterile tillers gave the best estimate of total fresh weight (95·3% reliability). However, total number of tillers (sterile plus fertile) was almost as efficient (94%). Tiller weight was a much less reliable index.

6. The results and their value in establishing efficient criteria for selection in grass breeding are discussed.

1. Recordings of faecal organic matter (O.M.), faecal N% (O.M. basis) and live weight, were made over 52 consecutive weekly periods on ten Corriedale wethers grazing a pasture consisting mainly of Wimmera rye-grass (Lolium rigidum Gaud.) with some subterranean clover (Trifolium subterraneum) in a Mediterranean-type environment. The amount of available O.M. and its N% were also recorded.

2. By applying regressions of (i) the ratio of O.M. feed intake to O.M. faecal output on faecal N% and (ii) the N% in the O.M. intake on faecal N%, to the above observations it was possible to estimate the following quantities: O.M. and digestible organic matter (D.O.M.) intake, N and digestible N intake and O.M. digestibility percentage.

3. The patterns of O.M. and D.O.M. intake, and N and digestible N intake are described. Similar patterns exist for each of these quantities. Two maxima, a large one in the spring and a smaller one in the autumn, and two minima, one in the summer and one in the winter, are exhibited. The values for these various maxima and minima are presented in the text.

4. Attention is drawn to variations from the general pattern for these quantities and factors which could influence these patterns are mentioned.

1. Variations in the crude-protein and mineral content of pastures at Muguga are described.

2. At all times sodium appeared to be inadequate, and during dry periods phosphorus and crude protein were also apparently deficient.

3. Except for sodium and calcium, the amounts present of all substances determined largely depended upon the amount of recent rain.

4. The difficulties of interpreting such data have been considered.

Bleasdale & Nelder (1960) refer to several models which have been used in studying the relationship of yield and density in crop plants and indicate that they regard as most satisfactory the equation:

where ω = yield/plant, ρ = number of plants/unit area and A and B are constants. The estimation of the constants for any given case is a very unattractive arithmetic exercise requiring a fairly large number of observations and a tedious iterative calculation; Nelder (1961) has discussed the least squares fit with the equation in the form

which may readily be derived from (1) by the substitutions

The data in the present case do not justify attempting this process but some progress can be made by the substitutions

by means of which it is easy to derive from (1) that

A description is given of a building and equipment which have proved suitable for cows in experiments involving the separate collection of faeces and urine.

There has been much speculation on the underlying mechanism of pregnancy toxaemia in the ewe (e.g. Reber, 1957; Kronfeld, 1958) and it is generally thought that the condition is a consequence of the failure of the ewe's metabolism to adapt to the increasing hexose demands of the foetus. Insufficient hexose is considered to be produced from dietary propionate and from the deamination of amino acids, with the result that liver glycogen is exhausted, citric acid cycle components are depleted and the resulting failure to oxidize activated acetate gives rise to ketone bodies. If this were the whole sequence of events the clinical symptoms should be reversible by the administration of glucose or glucogenic substances, orally or parenterally. Unfortunately clinical experience is that the condition shows a poor response to glucose therapy and the mortality of field cases is extremely high.

1. The effects of two heights of cutting—down to either 1 in. or 2–2½ in. from ground level—on herbage yields were studied for five seasons with a perennial rye-grass-white clover mixture and for three seasons with a timothy-white clover mixture. Superimposed on these height-of-cutting treatments were treatments simulating strip grazing with and without a back-fence, and also three fertilizer nitrogen treatments.

2. Over the 5-year period the rye-grass mixture consistently gave greater dry-matter and crude-protein yields of herbage when cut to 1 in. than it did when cut to 2–2½ in. from ground level, the mean dry-matter yield difference being 34%. The decline in the total yield per season with increasing age of the grass sward was similar under both heights of cutting.

3. The effects of the height-of-cutting treatments on the timothy mixture were similar to those noted on the rye-grass mixture in the first three seasons of the experiment, but in the third year the beneficial effects of close cutting were much reduced. It is suggested that this resulted from the rest period between cuts being insufficient for timothy to recover fully from the close defoliation.

4. The effects of the height-of-cutting treatments on the botanical composition of the sward were slight, particularly on plots of the rye-grass mixture.

5. Possible factors leading to the observed effects of the height-of-cutting treatments are discussed with reference to the results of other workers and to the results from a preliminary study of the differential effects of the treatments on stem and leaf formation in perennial rye-grass.

6. A simulation of strip grazing with and without a back-fence showed that the herbage yields from both seeds mixtures under both height-of-cutting treatments were considerably reduced by the removal of the regrowth which could take place in the absence of a back-fence.

7. The effects of delaying the first nitrogenoua fertilizer application of the season noted in an earlier experiment were fully confirmed in this experiment.

1. Δmin-Nad is the most satisfactory measurement for assessing mineralizable-N in the tropical forest soils used; values are treble those for Δmin-Nf and then increase even further on storage. Comparisons of Δmin-Nad are pointless unless methods of sampling, drying, storing and incubating are standardized.

2. Δmin-Nad is correlated with total N and organic C but not pH.

3. Undisturbed tropical forest soils can produce very large quantities of mineral N, particularly in their surface layers. This probably accounts for the lack of N responses in these soils. More intensive cultivation of these soils is only possible when organic matter is preserved by protecting cleared soils.

4. Added nitrogen was leached more rapidly in these soils than in comparable temperate soils but was not fast enough to prevent absorption by plants.

1. The composition of the bacterial population in the rumen of adult merino wethers conditioned to a diet of poor teff hay was studied during three consecutive periods of 60, 109 and 42 days when the ration was 1200,600 and 300 g. per day, respectively.

2. In all three periods there was no significant difference between the three sheep with regard to either the viable counts of the functional groups of bacteria fermenting cellulose, starch, glucose, xylose and lactate or the percentage proportions of the different morphological types occurring in each group.

3. The reduction of food intake had little or no influence on either the numbers or the morphological types of bacteria in each functional group.

4. The animals lost weight at approximately the same rate throughout the three periods of the experiment which was ended when they were in a state of prostration.

5. These results suggest that, providing the diet is changed only in respect of quantity, important functional groups of rumen bacteria can survive at levels of food intake which are insufficient for the survival of the animal.

There is a strong correlation between the digestibility of the organic matter and the percentage crude fibre, percentage lignin, and percentage cellulose plus lignin in the foodstuffs examined.

There is evidence that the holocellulose and xylan in grasses are different from those in legumes in the extent to which they are digested. It is suggested that this is due mainly to the xylans or hemicellulose fraction in the forages, and may be a reflexion of a different molecular structure for the xylans in either group.

Within each group of plants both the holocellulose and xylan percentages are strongly correlated to the percentage digestible organic matter.

Excessive heating of hay led to a marked rise in the percentage lignin. This is probably due to the xylans becoming horny and insoluble, therefore being determined as lignin. This also offers an explanation for the decrease in digestibility of the organic matter.

1. Italian ryegrass was used in 1958 and in 1959 to compare ‘single’ spring dressings of urea-formaldehyde fertilizer (UF) with equivalent spring dressings of ‘Nitro-Chalk’ (NC), and with ‘repeated’ NC (divided equally between three cuttings). Barley measured residues in 1960.

2. At the first cut each year, yields from UF and repeated NC were similar, but later NC gave much larger yields. Aggregate increases from UF were less than half those from equivalent NC.

3. Both forma of nitrogen had residual value for grass and barley.

4. Maximum recovery of N, over 3 years, was 54% for UF and 90% for equivalent NC. Single NC dressings were recovered more completely than repeated dressings.

5. The maximum aggregate uptakes over 2 years by grass receiving 2·0 cwt. N/acre each year were 72 lb. P and 611 lb. K/acre.

Eleven years of field experiments on manuring sugar beet were used by the late E. M. Crowther to compare methods of analysing soils for soluble P and K; this paper reports his work.

The experiments were divided by soil analyses into groups of equal numbers of sites; average crop responses were used to value the analytical methods. Such tables of average data overvalue soil analyses because each method was misleading in a small proportion of the fields used. A quantitative way was developed of assessing the gains from using soil analysis in planning fertilizing and of comparing analytical methods. The total profit from uniformly manuring all the soils examined was compared with the profit made by using analyses to select a proportion only of the soils to be manured; the total amount of fertilizer used was the same with each way of planning manuring. The most efficient analytical method gave the most profit.

For phosphate, differential manuring of sites selected by soil analysis was more profitable than uniform manuring, with all the methods of measuring soluble P that were tested. The best method used a rapid extraction with dilute hydrochloric acid, but extracting with water (calcium bicarbonate solution was used for calcareous soils), or with citric acid solution, was nearly as effective. These three methods, using little solvent relative to soil, were more useful than methods using larger volumes of dilute sulphuric acid, dilute acetic acid, and a lactate solution.

The sugar beet responded more often to K than to P manuring, so there was less chance of making extra profit by using analyses to detect the richer soils where either no K fertilizer, or small dressings only, should have been given. Using the citric acid method of measuring soluble-K to separate the soils into groups for differental manuring was more profitable than giving uniform dessings to all fields; acetic acid was less effective than citric acid, and the hydrochloric acid method gave no advantage over uniform manuring with the heavier rate of potassium. Water-soluble K measurements were worse than acid-soluble values; using them to predict responses and manuring would have given less profit than uniform manuring at the heavier rate used.

1. The composition of the bacterial populations of the rumen of three sheep on lucerne hay was very similar with regard to both the levels of the functional groups which ferment cellulose, starch, glucose and xylose and to the morphological types of which they were composed. The lactate-utilizing bacteria showed more variation in numbers between individual animals.

2. The rumen flora of lucerne hay fed sheep differed from that of sheep on teff hay not only in significantly higher counts of the carbohydratefermenting bacteria in the former group, but also in distinctive types of cellulolytic bacteria.

3. The short- and long-term variations in number of cellulose digesters found earlier in a sheep on a practical diet of lucerne hay were not markedly reduced by feeding the same animal lucerne hay of constant composition.

4. A correlation appeared to exist between the protein content of the lucerne hay and the level of the lactate-fermenting bacteria in the rumen.

5. The changes in the viable counts of the bacteria capable of fermenting cellulose, starch, glucose and lactate during the first 8 hr. after feeding a ration of lucerne hay were small compared with the in vitro rate of multiplication of a pure strain of cellulolytic cocci isolated from a sheep on the same diet. This is regarded as further evidence in favour of the notion that the rumen contents, particularly of animals on high roughage diets, approximates to a continuous culture system.

1. Rumen and caecal wall tissues were taken at slaughter from lambs varying in age from newborn to 11 weeks. The ability of these tissues to metabolize the short-chain fatty acids, acetic, propionic and butyric acid was compared with tissues from adult sheep. Ketone body production was measured.

2. The utilization of butyrate by the rumen wall in the newborn lamb was lower than in the adult, but exceeded the adult levels at 3 weeks of age and maintained this higher utilization to 11 weeks and probably longer. Ketone body production was negligible at birth but followed butyrate utilization closely thereafter.

3. The caecal wall in the newborn lamb utilized butyrate at a much higher rate than the adult sheep tissue. Foetal lamb caecal tissue utilized butyrate to the same extent as in the newborn lamb. Levels were, however, typical of the adult within a day or two of birth and showed no subsequent effect of age. Ketone body production was negligible at all ages.

4. Rumen development in milk-fed lambs slaughtered at 7 and 9 weeks of age was retarded anatomically and showed decreased capacity in the utilization of butyrate.

5. The utilization of acetate and propionate by rumen and caecal tissues showed no marked change due to age. Ketone body production from these acids was low.

The composition and feeding value of the common heather has been extensively studied by Thomas et al. (1934, 1935, 1953, 1955, 1956). He has shown that as the heather ages the protein content declines. Thus, samples from 2-year-old growths had a crude protein content (on a dry-matter basis) of 11·9% while that of growths 8 years old was 6·5–6·9%. Little or no information, however, appears to be available on the quality of heather protein, as judged by its amino acid composition.

Soil samples from 179 field experiments testing phosphate fertilizers on potatoes, swedes and grass were analysed for total phosphorus, and for phosphorus soluble in the following solutions: 0·3 N-HCl, 0·002 N-H2SO4, 1% citric acid (H3Ci), 0·5 N acetic acid (HAc), acetic acid-sodium acetate buffer (HAc-NaAc) at pH 4·8, 0·5 M-NaHCO3, and 0·01 M CaCl2.

Average values for soluble P were closely related to average crop responses to superphosphate in the experiments on swedes, but not in the grass and potato experiments. The extractants that differentiated best between responsive and unresponsive groups of experiments were HAc, HAc-NaAc, and NaHCO3 for potatoes, and HCl, H2S04, HAc–NaAc, NaHCO3 and CaCl2 for grass.

For the experiments as a whole 0·5 M-NaHCO3 was the ‘best’ extractant. The HCl, H2SO4, and HAc-NaAc buffer solution methods were roughly equally effective, though inferior to NaHCO3; the other three extractants (HAc, H3Ci, CaCl2) were of little general use. Total P in soil was also related to response to superphosphate, though less well than values for soluble P obtained by the better methods.

Estimates of soluble P by different solvents were often related. Estimates by HCl and H2SO4 methods were most closely related; values for P soluble in H2SO4 and in HAc-NaAc were also often significantly correlated, as were estimates by HAc–NaAc and CaCl2. The H3Ci and CaCl2 methods gave results that were least related to those with other methods.

The use of soil analyses in advising on P-manuring is discussed and a tentative method is proposed of establishing the analytical limits for soluble P that define ‘deficient’ soils. If the confidence attached to the limiting values that separate ‘deficient’ and ‘non-deficient’ soils is stated, farmers will be able to assess the risk entailed in accepting advice based on soil analysis.

A rapid and accurate atomic absorption method for the determination of chromium in faeces samples from pasture experiments using chromic oxide ‘markers’ is described. Of the elements present after ashing and digesting the samples in a phosphoric acid—manganese sulphate—potassium bromate solution silicate, aluminium, calcium and magnesium were found to interfere in the determination. The effects of these interferences were overcome by the addition of calcium to the test solution and by the addition of silicate to the standards, which were prepared in ‘blank’ solutions.

The sensitivities of a number of alternate chromium resonance lines relative to that of Cr 3578·7 Å. are given. These lines may be used to increase the concentration range of the analysis.

The results of a comparison of the atomic absorption method with a chemical method are given.

1. A group of four Ayrshire and four Friesian cows was strip grazed on a cocksfoot-dominant sward while a second, similar group was zero grazed on herbage cut from the same field. The experiment consisted of five 10-day periods, two in the spring and three in the summer.

2. The intakes of all cows were calculated from values for faeces output, estimated by using chromic oxide, and for herbage digestibility, estimated from faeces nitrogen. The regressions used for predicting digestibility were determined with the zero-grazed cows, digestibility coefficients being calculated from measured intake and estimated faeces output values.

3. Over the whole experiment there was no difference between treatments in milk yield, herbage digestibility or intake. The solids-not-fat content of the milk of strip-grazed cows was significantly higher than for zero-grazed cows.

4. In both spring and summer the increasing maturity of the herbage caused declines from one period to the next in herbage digestibility and intake, and there were declines also in milk yield and solids-not-fat content. The declines were greater for the zero-grazed cows, apparently because they, unlike the strip-grazed animals, were unable to select the more digestible and palatable components of mature herbage. The effects of selective grazing on digestibility, however, were evidently small, for the difference in between the treatment groups was never greater than one unit.

5. The estimated energy intakes of both treatment groups corresponded quite well with their theoretical requirements of energy for maintenance, milk production and live-weight gain, and there was no evidence of the energy cost of free grazing being appreciably greater than that of zero grazing.