Variation in urinary creatinine in nine male and twelve female buffalo calves divided into three equal groups on diets containing three levels of dietary protein intake (low, medium and high) was estimated. The variation in urinary creatinine (% and total) was large from animal to animal and also from day to day (P < 0·01) in the same animal. It was not affected (P > 0·05) by the level of dietary protein. The creatinine-nitrogen ratio decreased (P < 0·01) with increase in the protein level of the ration, but the creatinine coefficient (creatinine per kg body weight) did not differ significantly (P > 0·05). The male and female animals responded similarly.

It was concluded that urinary creatinine (% and total) and the creatinine coefficient cannot be used as an index either in nutrient balance studies or for evaluating ruminant nutrition in general. The creatinine-nitrogen ratio could also not provide a suitable yardstick to evaluate protein status of the animals because of the significant interaction of days × protein. The nitrogen balance is considered to be better for this purpose.

Nineteen feedstuffs were evaluated for total digestible nutrients (TDN), digestible energy (DE) and metabolizable energy (ME) using growing pigs. DE values, on a drymatter basis, ranged from 1570 kcal/kg D.M. (grassmeal) to 4890 kcal/kg D.M. (BP Grangemouth protein). ME averaged 97·4% of DE for cereal feeds and 81·9% of DE for protein feeds, the ratio of DE to ME being significantly affected by the crudeprotein content of the feedstuff:

ME/DE × 100 = 99·7–0·18 × crude protein (%): r = –0·94; P < 0·01.

TDN was more closely related to ME than DE:

DE (kcal/kg D.M.) = 45 TDN + 156: r = 0·92; P < 0·01,

ME (kcal/kg D.M.) = 43 TDN + 71: r = 0·98; P < 0·01.

ME values were corrected to both 30% and 0% nitrogen retention. Correction to 30% retention caused a maximum change of 3% in ME value while correction to 0% retention had a variable effect related to protein content of the feedstuff:

(ME(N0)/ME) × 100 = 98·3–0·113 × crude protein (%): r = –0·80; P < 0·01.

Eighteen individual feedstuffs and 19 mixed diets were used in a study attempted to relate determined energy values to various chemically determined measures. For cereals the level of fibre could be used to predict digestible and metabolizable energy (DE and ME). In the case of DE the relationships with crude fibre and modified acid detergent fibre (MADF) based on 14 feeds were:

DE (kcal/kg D.M.) = 4179–86 MADF (%): r =–0·96; P < 0·01,

DE (kcal/kg D.M.) = 4228–140 x crude fibre (%): r =–0·97; P < 0·01.

For all feeds the following equations gave the best prediction of energy values from dietary analysis (on the basis of correlation coefficients and residual standard deviations):

DE (kcal/kg D.M.) = 109·9 x crude protein (%) + 149·3 x acid ether extract (%) + 90·1 x nitrogen-free extract (%)–5030: R = 0·95; P < 0.01.

ME (kcal/kg D.M.) = 99·5 x crude protein (%) + 144·7 x acid ether extract (%) + 87·8 x nitrogen-free extract (%)–4795: R = 0·94; P < 0·01.

Digestible nutrients were closely related to DE and ME, e.g.

DE (kcal/kg D.M.) = 52·9 x digestible crude protein (%) + 108·3 x digestible ether extract (%) + 39·4 x digestible crude fibre (%) + 39·9 x digestible nitrogen-free extract (%) + 183·7: R = 0·99; P < 0·01.

Following a 14-day uniformity period when they were stall-fed to appetite on a grass silage-grass ration, 18 cows in mid lactation were allocated to three treatments on which they received during the following 28 days either 100%, 75% or 50% of their previous voluntary feed intakes.

Treatment effects were measured on milk yield and composition, live weight, liveweight change and fasted live-weight change. Twice during uniformity period, and on the 7th, 14th, 22nd and 26th days of the treatment period, samples of jugular blood were obtained from each cow immediately before and 3 h after the first meal of the day. These were analysed for percentage packed cell volume, blood acetone and β-hydroxybutyrate levels, plasma glucose, non-esterified fatty acid, and total fatty acid concentrations.

Alternative methods of collecting blood samples, involving cannulation of the vein and venipuncture, were compared. Obtaining samples through cannulae took nearly three times as long as by venipuncture, but the method of sampling did not significantly affect the concentrations of individual blood metabolites. Blood samples collected before as contrasted with after feeding had significantly higher concentrations of nonesterified fatty acids and glucose, and lower concentrations of acetone and β-hydroxybutyrate.

The feed requirements of the cows were assessed using data on live weights, fasted live-weight change and milk production by calculating the regression of estimated net attributable energy/kg LW0·75 on digestible energy intake/kg LW0·75, from data for the full 28-day period. The maintenance requirement was 124 kcal net energy/kg LW0·75, and the efficiency of conversion of digestible energy to milk and body-tissue loss or gain was 60%. These data were used with each animal's live weight, milk yield and liveweight change appropriate to each blood-sampling day to calculate individual feed requirements on every occasion. Ratios of actual feed consumed to estimated requirements were calculated subsequently to provide quantitative indices involving all cows and feeding levels. Regressions of these indices on individual blood metabolites were examined to assess the value of the latter as predictors of the relative nutritional status of the cows as defined in this way. Of the blood metabolites studied, only plasma NEFA were consistently significantly correlated with these indices, and relationships were specific to each feeding level. Thus although, at a common feeding level, plasma NEFA can be used to categorize lactating cows according to degree of nutritional stress, they will have limited values as predictors if applied indiscriminately to the wide range of feed availabilities and intakes which exist between herds at similar stages of lactation.

The results have been discussed relative to previously published work, mainly with sheep and beef cattle.

A technique for estimating the intake of liquid supplements by individual, grazing animals was used in a trial with 200 sheep grazing poor quality pasture and given access to a urea-molasses supplement (19%, w/v).

A mathematical procedure was developed to estimate intake of supplement based on measurements of the accumulation of tritiated water (TOH) and its rate of turnover in the body of each animal after a TOH-labelled mixture had been available for a period of 7 days.

In calculating the level of intake of labelled supplement, it was assumed that each animal ingested the mixture once daily over the 7-day period, since animals were observed to take the supplement daily and the daily loss of supplement from the dispenser was noarly constant. It was estimated that the combined intakes of the animals accounted for 87% of the known total loss of labelled supplement from the dispenser.

Of the 200 sheep, 97 did not consume any supplement and among the other 103 animals, estimated intake varied from 5 to 550 ml/day.

All sheep lost body weight during the trial, but those consuming the supplement lost significantly less weight, and grew significantly more wool during the period of supplementation, than did the sheep that did not consume the supplement.

A small but significant amount of the variance (13%) in body-weight change and wool growth during supplementation was removed by multiple regression analysis, by including the intake of the supplement, faecal egg count (as an indication of parasite burden) and body weight at the start of the trial, as independent variables. Other factors not studied (e.g., dry matter intake) apparently accounted for a large proportion of the variance.

The relationship between body-weight change and intake of the urea-molasses mixture was compatible with the hypothesis that the supplement was used largely as a concentrate feed, and not solely as a nitrogen supplement.

In a field experiment sunflower plants were subjected to soil water stress (SWS) at — 15 bar during stages of slow elongation, rapid elongation, flowering and ripening.

Significant decreases in yield, 100-seed weight and oil content were found as a result of SWS. The treatment resulted too in less evapotranspiration and a better water economy for production of seeds and oil.

The iodine value but not the acid or saponification values of the oil was affected by SWS. No qualitative differences in oil composition occurred at different treatments. However, percentage of oleic acid was higher than that of linoleic acid; SWS resulted in a clear tendency for an increase in the ratio of oleic/linoleic acids especially for plants subjected to SWS during elongation stage.

Sunflower plants were more sensitive to SWS during the elongation and flowering stages than during ripening stage

Sebum was collected from pre-cleaned areas on the skin of Ayrshire calves at a fixed time using a cup and solvent technique, extracted and weighed. The rate of sebum output decreased with time and after 18 h there was very little increase in the weight of sebum on the skin surface. Sebum output over a period of 3 h was not statistically different between animals of different ages but tended to be higher in castrated males than in females and was lower in winter than throughout the remainder of the year.

Six hybrids, either pure dent or flint x dent crosses, together with two open-pollinated flint varieties of early maturity, were grown at Oxford, England, and the yield of grain determined over a range of 15 densities (5.30.8 plants/m2). The relationship of yield to density was studied by fitting mathematical functions to the observed yields. Only two functions, (1) the inverse quadratic on yield per unit area, and (2) the linear regression between density and the logarithm of grain yield per plant, were satisfactory fits. The linear regression was preferred because of its ease of calculation and interpretation. Between genotypes the largest differences in grain yield per unit area were found at densities either above or below those which are employed in normal practice.

The ranking of the genotypes for grain production depended upon the density. Whereas at the lowest density a very short, early-maturing flint genotype, GaspéFlint, yielded least, and a tall, full season dent hybrid, 0X324, yielded most, this position was reversed at the higher densities. Maximal levels of yields of the open-pollinated flint varieties were low, and it is apparent that the incorporation of this source of germplasm in hybrids is limited if commercially acceptable yields are to be attained. Maximal yields of 600 g/m2 were produced by three hybrids, but the optimal densities were markedly divergent. They ranged from 6.2 plants/m2 for 0X324 to 9.7 and 10.8 plants/m2 for INRA 270 and INRA 200. Possible reasons for such differences are discussed in terms of the interactions of density and genotype on the components of yield.

In one experiment, variety Kutsaga 51 was grown at inter- and intra-row spacings of 60, 80 and 100 cm. Both yield and quality of leaf were improved as plant density per unit area increased. The greatest yield and highest quality were obtained from the 60 x 60 and 80 x 60 cm spacings while the lowest yield and quality were obtained from the 100 x 100 and 100 x 80 cm spacings.

In a second experiment the same variety was subjected to three levels of N and four levels of K. Higher doses of N or K were not necessarily effective in increasing the yield or improving the quality of leaf; on the contrary rates higher than 42/ha reduced both yield and quality of the leaf. Progressively higher doses of K did not offset the ill effects of excessive N.

Yield of leaf was primarily a function of leaves per unit area in the plant density experiment and number of leaves per plant in the fertilizer experiment.

Residual effects of N, P and K applied to cotton on the following crops of dura (Sorghum vulgare), lubia (Dolichos lablab) and wheat (Triticum vulgare) were investigated using data obtained over a 30-year period from a factorial field experiment including various levels of the three nutrients. The three crops differed in their response to residual N, P and K. Dura and wheat, being nitrogen depleters highly responsive to fertilizer nitrogen, were consistently affected by residual N. The residual effects of N on grain and straw yields of both dura and wheat were significant in all seasons and the effects were proportional to the amount of N applied to the preceding cotton. There were indications, however, that a much greater part of the N applied in the preceding year was not available to the succeeding crop. Residual P did not have a significant effect on dura but it varied in its effect on the different components of wheat in different seasons. Residual K did not have any effect on dura or wheat. Data on nutrient uptake and composition of wheat tended to support the yield responses. Contrary to the response of the two cereal crops lubia, being a nitrogen fixing legume, did not respond to the effect of residual N and was consistently affected by residual P. Residual K had a slight effect on lubia in only a few seasons.

The annual patterns of infestation of sugar-beet root and seed crops by green aphids (Myzus persicae) and by black aphids (Aphis fabae) were similar, paralleling population changes shown by catches on sticky traps in southern England, but the incidence of yellows in root crops was not correlated with incidence in seed crops in the same year. Few green aphids overwintered on beet-seed plants and the incidence of yellows was consistently low in the main seed-growing areas where all the stecklings are raised under cereal cover crops. Elsewhere, yellows sometimes spread in the autumn and many green aphids occasionally overwintered. Black aphids were seldom prevalent; the severity of attack correlated with the number of eggs laid on spindle (Euonymus europaeus) during the previous autumn.

Twenty-two per cent of mangold clamps checked in mid-April contained aphids, but only about 5 % contained M. persicae. Seventeen per cent of the infested clamps contained aphids infective with BMYV and 10% contained aphids infective with BYV. However, the acreage of mangolds grown in England has decreased.

Myzus ascalonicus overwintered on weeds more often than M. persicae or other species likely to act as vectors of viruses affecting sugar beet. Forty per cent of samples of some common weeds collected from sheltered sites during mid-April from 1963 to 1973 were infested with aphids, and those on chickweed (Stellaria media), groundsel (Senecio vulgaris) and shepherd's purse (Capsella bursa-pastoris) were commonly infective with yellowing viruses. Weeds are probably a major source of yellowing viruses in southern England.

Experiments in England from 1970 to 1973 investigated the possibility of extending the growing season and increasing yields of bolting resistant sugar beet by sowing in autumn rather than in spring. September-sown plants grew rapidly in spring and achieved a complete leaf cover by mid-June by which time they had intercepted 40 % of radiation incident since mid-April compared with 28 and 9% for crops sown on 13 October and 13 April respectively. By early June autumn-sown plants were 20 fold heavier than spring sown but this advantage was progressively lost with the onset of bolting. Root growth slowed as assimilates were diverted to stem and inflorescence growth. Delaying autumn sowing from late September until mid-October delayed and reduced the frequency of bolting, probably because of a shortening of the period when plants were sufficiently large to respond to cold. Cutting down bolting inflorescences at frequent intervals improved root growth of both bolters and non-bolters. However, yields from autumn sowing never exceeded those from spring sowing, the best yield from an autumn-sown crop was 6·1 t/ha of sugar which was similar to that of the spring-sown crop. To try to prevent bolting of overwintered plants the growth regulator ethephon was applied at 10000 mg a.i./l water sufficient to wet the foliage in mid-April. Growth was severely checked and 55 % of plants died. Of the remainder 25–30% fewer than in the untreated crop bolted but yields were 26–42 % less. Less concentrated doses of ethephon did not affect bolting.

Seven determinations of energy and nitrogen retention using four adult wether sheep were made when they were fed a complete cobbed diet. The diet contained 30% of barley straw and had a metabolizable energy value of 10·9 kJ/g organic matter and the net availabilities of its metabolizable energy were 52·8% for fattening and 72·8% for maintenance. The starch equivalent on a dry basis was 53.

Prenatal mortality was examined in 74 primiparous Merino ewes which, after hand mating to fertile rams on the second oestrus following synchronization, were allocated to two groups. One group of 38 ewes was confined to yards and restricted to approximately 30% of their maintenance requirement for 14 days while the other group of 36 remained at pasture. The degree and timing of prenatal loss was assessed by corpora lutea counts, pregnancy diagnosis about day 40, returns to service and lambing records.

The mean ovulation rate was 1·06 and the 19-day non-return rate was 87·8%. Pregnancy failed in a higher proportion of the underfed ewes (45·0%) than in the control ewes (30·8%) but this difference did not reach significance. Of the ewes returning to service, significantly more did so with cycles longer than 19 days in the underfed group (9/12) than in the control group (2/8), indicating that in the latter stages, the treatment may have been detrimental to embryo survival.

In a second experiment, ovulation rate and prenatal mortality, assessed as in the first experiment, were studied in 85 mature Merino ewes subjected to the following nutritional treatments: HH, control; HL, 30% submaintenance feeding for 14 days following mating; LH, 15% submaintenance feeding for 7 days prior to mating; LL, both submaintenance treatments.

Acute undernutrition prior to mating (LH) had no effect on ovulation rate or prenatal mortality. Ovulation rates were low over all groups (mean 1·09) and thus precluded any valid examination of ovulation rate and body weight relationships. The right ovary was significantly more active in producing ova than the left in all groups (P < 0·05). Although ova wastage was apparently higher in. the post-mating undernutrition groups (HL, 44%; LL, 48%; LH, 50%) than in the control group (HH, 35%), the differences were not significant. An increased incidence of extended (> 19 days) first-return cycle lengths in group LL provided some evidence of induced prenatal mortality.

In so far as the experiments can be considered together, they indicate that if body weights are comparable, primiparous 1½-year-old ewes are not necessarily more susceptible than mature ewes to prenatal mortality induced by severe short-term undernutrition.

Oestrus, ovulation rate and prenatal mortality were studied in 114 mature Merino ewes of high and low body weight at mating. Three nutritional treatments were imposed over 8 weeks prior to hand mating to fertile rams; high plane (HH), low plane (LL) and 7 weeks of high plane followed by 1 week of fasting immediately prior to mating (HL). Ovarian activity, ovulation rate and the extent and timing of prenatal loss were assessed by the appropriate use of direct ovarian observations, pregnancy diagnosis, returns to service and lambing records.

While both prolonged undernutrition (LL) and acute nutritional restriction (HL) were associated with some suppression of behavioural oestrus, neither had any appreciable effect on ovulation rate or prenatal mortality. In all groups the right ovary was more active in producing ova than the left, and the HH group had more ovarian follicles (≥ 4 mm diameter) than the other two groups. Large unruptured ovarian follicles (6—15 mm diameter) were observed in nine ewes. Significantly more ova shed in multiple ovulations were lost, and multiple-ovulating ewes were more likely to suffer complete rather than partial loss of both embryos. Impaired fertility was evident when ewes that returned to service at an extended cycle length were re-mated.

Six herbage samples (ranging from poor quality hill herbages to high quality ryegrass and clover) were analysed for soluble carbohydrate, total and soluble nitrogen (N), cell-wall carbohydrates and in vitro digestibility. Changes during freezing and thawing processes were measured. Invertase activity occurred in all frozen and thawed samples. Although the total N content of all samples remained constant throughout, the soluble-N contents of the four better quality herbages were considerably reduced on freezing and thawing. Cell-wall carbohydrates and in vitro digestibility measurements were unaffected by freezing and thawing.

The upgrading programme of. the Local Indian Dairy cattle in Malaysia to the Red Sindhi over a period of 21 years is evaluated. Heterosis was not observed among the Fx cross-breds for milk yield and related traits. The attempt to upgrade local dairy cattle using Red Sindhi however resulted in deterioration of performance.

The fertility, especially potassium status, of the Barming series in East Kent was studied by laboratory and pot test procedures to determine the effect of indigenous glauconite. Half of 12 otherwise similar soils contained appreciable glauconite.

Glauconite contributed positively to the potassium status of the soils, especially the B horizons (45–65 cm), and was associated with higher values of exchangeable potassium, cation exchange capacity, nitric acid soluble potassium and intensity of potassium supply as measured by ΔḠ. More potassium was taken up and more released from initially non-exchangeable sources to ryegrass from the glauconitic soils. The available magnesium content of the soils was also positively correlated with glauconite content but available phosphate was not.

Twelve stagnogley soils of the Denchworth series from East Kent were studied to determine the effect of indigenous glauconite on their fertility. The presence or absence of glauconite was not the major factor controlling the potassium or magnesium status which was largely determined by the nature of the < 2 μm clay. Glauconitic soils had much higher levels of available phosphate than corresponding non-glauconitic soils due to calcium phosphate associated with the glauconite in the parent material. Weathering has partially converted this to aluminium and iron phosphates which were the main forms of phosphate present, especially in the A (0–15 cm) horizons.

Seven hundred and twenty-five adult ewes of six breeds, namely Marwari, Chokla, Magra, Pugal, Jaisalmeri and Russian Merino x Marwari (F1) were typed for blood potassium, haemoglobin and erythrocyte-reduced glutathione (GSH) types. The nature of the association between each polymorphic trait and wool production efficiency (wool yield per kg body weight) in these breeds has been examined.

GSHh animals were predominant in all the breeds. A negative correlation was observed between wool production per kg body weight and erythrocyte glutathione level. In general, mean wool production per kg body weight was found to be more in animals of Hb type A than in other Hb type animals. No significant correlation between blood potassium level and wool production per kg body weight was found in any of these breeds.