Following both a low and high plane of winter feeding two groups of 18 bullocks each were stocked at 2·5 (low), 4·3 (medium) and 6·2 (high) bullocks per hectare. The Hereford × Shorthorn bullocks averaging 350 kg live weight were rotationally grazed on ten plots, seven of which contained a H.I. white clover mixture and the remaining three contained permanent pasture. Pasture digestibility and intake were determined for 16 weekly periods between early April and late September. In vitro digestibility was determined on samples obtained by means of two rumen-fistulated bullocks. A gelatin capsule containing 10 g of chromic oxide was administered daily to each bullock to estimate faecal output. Digestibility, faecal output and intake were expressed on both a dry and organic-matter basis. Increasing the stocking rate resulted in a corresponding decrease in organic matter (OM) percentage of the faeces but the magnitude of the differences varied throughout the growing season. The average decline (all 16 periods) was linear, the OM percentage of faeces being 80·9, 76·8 and 72·6 for low, medium and high stocking rates, respectively. Faecal ash content of rectal samples and those taken from the pasture differed significantly only in a few instances, indicating that pasture faecal contamination may not be serious if careful sampling is practised. Higher ash intakes at high stocking intensities are reflected in herbage intake errors when results are expressed as dry matter instead of organic matter.

A total number of 5949 birth records collected over a period of 9 years from a crossbreeding experiment at Sakha Animal Research Station were used in this study. The following breeding groups were included: Fleisch Merino (M), native Ossimi (0) and Barki (B) breeds, MO, MB, ¾M ¼ O, ¾ M ¾ B and the inter se mating groups of the backcrosses (’¾ M ¼O’ and ‘¾ M ¼B’). Productive traits studied were birth, 4-month and yearling weight, lamb liveability at 4 months of age; and first fleece weight (at 10 months of age).

Generally, the cross-bred lambs were heavier in body weights and sheared more wool than the pure breds, with the differences being almost significant. In liveability, native breeds showed significantly higher estimates than the cross-breds where the Merino breed was the poorest in this respect.

Merino × Ossimi first cross was the best breed group showing a high heterosis estimate of 0·9, 5·2, 10·3, 7·6, 0·9 and 0·7 kg in birth, 4-month, yearling males and females body weights and first fleece weight, respectively. They were followed by ¾ M ¼ O with a corresponding heterosis value of 0·8, 3·9, 7·4, 4·2, 0·5 and 0·5 kg respectively. Merino x Barki and their backcrosses to Merino are ranked second to the Ossimi crosses. Heterosis in the Barki backcross was 0·8, 2·9, 4·8, 2·1, 0·4 and 0·4 kg compared with 0·5, 2·5, 3·1, 2·7, 0·5, 0·4 kg for MB, on different traits, respectively. The interbreeding of the backcrosses caused a diminishing in hybrid vigour. Heterosis estimates in ‘¾ M ¼ O’ were 0·3, 0·9, 4·6, 2·3, 0·3 and 0·3 kg, whereas it was 0·1, 0·3, –0·1, –0·3, 0·0 and 0·1 kg for ‘¾ M ¼B’, in different traits respectively. All cross-breds showed negligible or/and negative heterosis in lamb liveability up to 4 months.

The effects of breed group, year of birth, age of dam, sex and type of birth were found to be highly significant on all traits except the effect of type of birth on lamb liveability.

A detailed study was made of the tillering of barley plants grown at densities which ranged from 50 to 1600 plants m–2. Throughout the season the initiation of tiller buds and their growth in length and leaf number were followed, and measurements were made of leaf sheath and lamina length and lamina width. A proportion of tillers died and their positions and times of death are given.

Three phases of tillering were recognized. The first, tiller bud initiation, was little affected directly by density. During the second phase, buds did not grow or did grow and emerge from the subtending leaf sheath. If they grew, there was no difference in growth rate of tillers at different densities. At the higher densities fewer buds developed, and the morphology of those tillers which did grow was affected by density. This suggests that the growth of the tiller bud may be controlled by levels of endogenous gibberellin, while in the final stage, growth after emergence from the subtending leaf sheath, competition for light appears to be the factor which determines whether a tiller survives to produce an ear. The data are discussed in relation to the practical importance of tillering.

Sheep were given artificially dried grass either in the long form or as pellets, and their energy retention measured. Experiments were made both at the maintenance level of feeding and when feed was offered ad libitum. An analysis of the effects of preceding and current daily feed consumption on heat production was made and both exact and approximate methods of estimating the mean food intake to which a determination of heat production should be referred, are given. Pelleting the dried grass increased voluntary intake of dry matter by 27%, and the intake above maintenance by 59% The metabolizable energy of the grass was depressed by pelleting but the net availability of metabolizable energy for production was 52% for pellets and 40% for long material. The percentage of the gross energy supplied above maintenance which was retained was 28% greater for pellets than for long dried grass. The results show that energy retention of the sheep was almost doubled when the grass was pelleted.

Thirty-two beef calves (mean body weight 79 kg) were given a ration which depleted their body reserves of Na as was evidenced by a narrow Na to K ratio in the parotid saliva. Eight calves were then assigned to each of the following four treatments: low Na basal ration alone, basal ration plus either 1·09, 2·19 or 3·28 g Na/calf/day as bicarbonate.

Forty 6½-year-old Scottish Blackface ewes were used in an experiment to investigate the effects of low protein and low calcium (Ca) intakes during pregnancy on body composition and mineral contents. Six sheep were slaughtered at the commencement of the experiment as controls; 28 were used in a 2 × 2 factorial experiment in which semipurified diets containing 11·8 and 6·0% crude protein (CP) and 1·2 and 0·11% Ca in the dry matter were offered to maintain non-esterified fatty acids (NEFA) and ketone bodies in the plasma at levels comparable to those found in hill sheep in winter. All ewes were slaughtered after parturition and the carcase dissected into soft tissue and skeleton fractions. Both fractions were dissolved in HNO3 and the fat and mineral contents measured.

Four experiments are described in which the response of sugar beet to irrigation was measured over a range of approximately 30000–150000 plants per hectare, and one experiment where the effects of plant population and spatial arrangement were studied. The experiments were carried out on a sandy soil in the south-east of England and extended from 1960 to 1965. The response of sugar beet to irrigation was affected by plant density. It is suggested that some explanation for the modified responses may be provided by considering effects of plant population on (i) the rate at which the soil surface is covered by leaves, and (ii) effects on the volume of soil exploited for water.

Four equally spaced feeding levels, estimated to cover the range of commercial practice, were examined using a total of 208 pigs over the live-weight range 28–100 kg. The pigs were penned in groups of six or eight and were balanced for sex within pens. Three centres participated in the experiment contributing five, two and one replicates respectively.

Efficiency of feed conversion was not significantly affected over the range of feed intakes studied, thus daily gain was linearly related to feed intake. A 10 decrease in feed intake increased killing-out percentage by 0·3 unit and decreased backfat thickness by 1 mm at both the shoulder and mid rump. The corresponding changes in the percentages of subcutaneous fat plus skin and meat were similar in magnitude at approximately 0·85 unit.

Muscle quality was reduced with higher feed intakes but weight of liver, as increased. Details of other offal weights and carcass measurements are given.

The effects of low protein and low Ca intakes during pregnancy on lamb composition and mineral contents have been investigated. Twenty-eight 6½-year-old Blackface ewes were used in a 2 × 2 experiment in which semi-purified diets containing 11·8 and 6·0% crude protein and 1·2 and 0·11 % Ca in the dry matter were offered to maintain constant levels of non-esterified fatty acids (NEFA) and ketone bodies in the plasma, comparable to those found in hill sheep in winter. A further group, control, were fed a conventional diet containing adequate crude protein and Ca to maintain NEFA and ketone body levels typical of well-nourished sheep. The lambs were killed at birth and whole body fat, moisture, nitrogen, Ca, P, Mg, Na and K contents determined. Further data was obtained on the brain, liver and semitendinosus muscle.

Within the context of the experiment the most important factor in determining the mineral content of the lambs was the protein intake of the ewe, mainly due to its effect on lamb body weight. The mean Ca content of lambs from the control ewes was 47·8 g. By comparison that of lambs from the high and low protein groups was reduced by 4·9 and 12·9 g respectively.

Calcium intakes as low as 27 mg/kg ewe body weight/day had no significant effect on lamb birth weight or mineral composition.

The mean concentrations (g/kg) of minerals in the fat-free bodies of the lambs ranged from 12·1 to 14·6 for Ca, 6·6 to 7·4 for P, 0·49 to 006 for Mg and from 1·9 to 1·6 for K in the control and double deficiency groups respectively. It was concluded that these changes in lamb composition could be interpreted according to classical studies on the influence of undernutrition on the relative growth and development of animal tissues.

The livers of the lambs, although significantly reduced in weight by the protein deficiency showed no evidence of being relatively more severely affected than muscle tissue.

Potential cellulose digestibility, measured by incubation in vitrofor 6 days, decreased during floral development in perennial ryegrass, Wimmera ryegrass, cocksfoot, oat and tall fescue. The rate of decline was slower than for cellulose digestibility measured after incubation in vitro for 2 days only. Morphological fractions ranked in order of descending potential cellulose digestibility – leaf blade, inflorescence, leaf sheath and stem.

Lignin content was determined chemically by the method of Van Soest (1963) and lignified tissue was assessed by staining transverse sections of leaf blades and leaf sheaths with safranin and fast green. Both lignin and lignified tissue increased with maturity. Lignified tissue increased mainly through increase in the number of scleren-chyma cells, but was also affected by the formation of lacunae or cavities between the vascular bundles in leaf blades of cocksfoot and in leaf sheaths of all species studied. For 19 samples of leaf blades and leaf sheaths, potential cellulose digestibility had significant negative correlations with both lignin content (r = -0·862) and lignified tissue (r = -0·905). Limitations to the techniques used to assess lignification and further factors which may affect the relationship between lignification and potential cellulose digestibility are discussed.

The balance between heat production and heat loss and the partition of heat exchanges of cattle in relation to air humidity has been studied at two different air temperatures using a direct (gradient-layer) calorimeter.

Increasing humidity at 35 °C air temperature caused no significant change in heat production or in the level of total heat loss finally attained, but body temperature and respiratory activity were both increased.

Increasing humidity at 15 °C air temperature caused a small reduction in heat loss by evaporation but had no effect on sensible heat loss, body temperature or respiratory frequency.

Heat loss by evaporation amounted to 18% of the total heat loss at 15 °C and to 84% at 35 °C.

Heat loss by respiratory evaporation amounted to 54% of the total evaporative heat loss at 15 °C and to 38% at 35 °C.

Maize or lucerne silages were fed to two groups of cows in a large dairy herd. Metabolic profile tests carried out during the trial showed that abnormal blood chemistry such as might lead to production disease did not occur in either group.

The results of feed analysis and digestibility trials showed that the two silages provided equal quantities of digestible energy but that the lucerne silage provided more digestible protein than the maize silage. Blood glucose concentrations were similar in both groups of cows but serum urea and albumin concentrations were significantly higher in the cows fed lucerne silage than in those fed maize silage. There was also evidence that lucerne silage provided slightly less available phosphorus but more calcium than the maize silage.

It is concluded that maize silage, as used in these experiments, showed no tendency to lead to production disease, and furthermore the metabolic profile test provided additional information to feed analysis in making this assessment.

Organic-S and sulphate-S were measured in the Northern Guinea savannah zone down soil profiles under undisturbed natural vegetation, and in land cleared and cropped, with and without fertilizers and farmyard manure. The main soil type was a drained, red to red-brown, sandy clay to clay loam (pH 4·1–5·6 in 0·01 M-Cal2), which strongly sorbed sulphate.

Organic-S was most in the surface layers and decreased with depth. Root remains from the natural fallow vegetation, present up to 9 years after clearance, strongly influenced the distribution of organic-S. The roots disappeared after 19 years, when distribution of organic-S mainly reflected crop-root distribution; amounts of organic-S were related to crop yields. FYM was less effective in maintaining organic-S than fertilizers containing P and N.

Profiles under natural vegetation contained little sulphate-S but it accumulated in the sub-soil after clearance when S was not removed. The sulphate pattern of profiles under unfertilized crops resembled that under natural vegetation. All fertilized sites had a well-defined sulphate sorbtion pattern, the deepest maximum was at 50 cm on a plot where more than 800 kg S/ha had been applied in nineteen annual aounts. Sulphate-S ranged from > 1 ppm, in the deepest samples, to 52 ppm at the absorption maximum.

Almost all the sulphur applied was in the profiles or removed in harvested crops, showing that losses from erosion and leaching were small.

Twenty-eight 6½-year-old Scottish Blackface ewes were used in a 2 × 2 factorial experiment and given semi-purified diets containing 11·8 or 6·0% crude protein (CP) and 1·2 or 0·11 % calcium (Ca) in the dry matter (DM). The amounts of diet offered were adjusted to maintain non-esterified fatty acids (NEFA) and ketone bodies in the plasma at levels comparable to those found in hill sheep in winter. Mean group values of NEFA during the final 6 weeks of pregnancy were maintained at these levels (1100–1300 μ-equiv/1) and ketone bodies at approximately 4·8 mg/100 ml. A further six sheep were fed a conventional diet containing adequate CP and Ca, to maintain NEFA and ketone bodies at levels typical of well-nourished sheep. Ewes and lambs from the undernourished groups were slaughtered after parturition and the chemical compositions of their bodies and those of six ewes slaughtered at the commencement of the experiment determined.

The oestrogenic activity and coumestrol content of ‘diseased’ and ‘clean’ white clover and lucerne were investigated. It was found that both coumestrol content and oestrogenic activity were increased in diseased white clover. However, there was insufficient coumestrol to account for the oestrogenic activity and it was suggested that other factors (e. g. oestrogen potentiator, unidentified oestrogen) were involved.

The results obtained for dry matter and energy digestibility with 116 different rations fed to 242 non-pregnant dry cows and 96 laotating cows were studied.

With winter rations, dry-matter digestibility (Y) is linearly related to dry-matter intake (X1) and to the crude fibre content of the dry matter (X2):

Y = 89·58–0·557X1–0·863X2.

A similar equation was obtained for energy digestibility (Y):

Y = 90·68–0·195X1–0·892X2,

where X1 represents the energy intake (in 1000 kcal) and X2 the crude-fibre content.

Digestible dry matter or energy can be estimated very accurately from dry matter or energy intake and from crude-fibre content.

There is a highly significant linear relation between dry matter or energy digestibility and nitrogen concentration of the faeces, especially with grass.

Dry-matter digestibility is also influenced by the physical form of the feeds and by individual factors.

Two experiments carried out in 1968 and 1969 are described which examined, through growth and yield analysis, the effect of nitrogen on the growth of oilseed rape. The results of the second experiment, when 0, 105·5 and 211·0 kg N/ha were compared, are presented and discussed. The application of nitrogen increased the yields of seed and oil, principally through increased production of seeds by a larger number of pods. However, the application of nitrogen had little effect on average pod weight or average seed weight. Crop growth rates were increased by the application of nitrogen and reached their highest levels during the period of pod development when the leaf areas had declined to very low levels. The order of effects of nitrogen (N 2 > Nl > NO) was similar for LAI, number of pods per plant and number of seeds per pod and it is likely that the effect of nitrogen was achieved indirectly through an increase in the supply of assimilates to the flowers and young pods. This suggests that the maintenance of a large and photosynthetically efficient leaf area during the period of flowering is necessary for high yields in this crop.

The results also suggest that once pods are macroscopic they produce much of the assimilates needed for their own growth.

The implications of these findings with regard to both practice and further research are discussed.

The phenological development from sowing to flowering of the eaxly maize hybrid INRA 200 is related to the weather conditions. Plot trial data from Wytham, near Oxford, England, and weather information from that and nearby sites formed the basic data.

The mean rate of development per day from sowing to emergence is related by linear correlation analysis to the mean values of soil temperature at 5 cm depth and soil moisture deficit. A range of temperature thresholds for emergence development exist, which depend upon the soil moisture, and which differ from the true physiological threshold.

Between omergence and flowering the mean rate of development per day is related by linear correlation analysis to mean air temperature, solar radiation and potential transpiration estimated from weather data. All correlations are significant, but the parameters which combine radiation and temperature are statistically better.

The results obtained for nitrogen and ether extract digestibility with 116 different rations fed to 242 non-pregnant dry cows and 96 lactating cows were studied.

A hyperbolic relation exists between nitrogen digestibility (Y) and crude protein content (X), with the equation:

Y = 88·6–(301/X)(r = – 0·928**, RSD = 4·78).

Digestible protein content ( Y) is linearly related to crude protein content(X):

Y = 0·90X-3·10 (r = 0·982**, RSD = 0·823).

From dry-matter intake and crude protein content it is possible to estimate accurately the amount of digestible nitrogen. With all the experimental rations the mean metabolic faecal nitrogen was 496 mg/100 g of ingested dry matter, and the true nitrogen digestibility was conspicuously constant up to 90%.

Digestibility of ether extract depends on the nature of the feeds. When the concentrate percentage of the ration is high, the digestibility of ether extract obeys the same laws as that of nitrogen.

The main objective of the experiments described was to compare the effects of milling straw and/or soaking or spraying it with sodium hydroxide on its digestibility and acceptability to sheep. Some preliminary trials were made in the laboratory to compare different alkali treatments with respect to losses of organic matter, chemical composition and digestibility in vitro.

In a feeding trial of Latin-square design, involving six sheep, the following treatments of barley straw were compared: C, chopped; M, coarsely-milled; OIL, chopped and soaked in 1·5% NaOH (9 g NaOH/100 g straw); CIH, chopped and soaked in 3·0% NaOH (18 g/100 g straw); CS, chopped and sprayed with 16 % NaOH (8 g/100 g straw); MS, milled and sprayed with 16 % NaOH. After treatments OIL and CIH the straw was washed; this caused losses of organic matter of 28 and 32%, respectively. For CS and CM the excess NaOH was neutralized by addition of 7·4 ml propionic acid/100 g straw.

The straws were given with supplements of purified soya protein, minerals and vitamins. The digestibility of energy for the straw was (%): C, 40·4; M, 39·1; CIL, 65·0; CIH, 64·4; CS, 57·3; MS, 60·2. Dry-matter intake (g/kg W0·75 per day) was: C, 26·7; M, 36·2; CIL, 37·1; CIH, 44·2; CS, 48·4; MS 53·6.