Diurnal changes in number of protozoa were examined in two wethers fed once and twice daily with 0·4 kg of concentrate and 0·4 kg of hay per day. The number of protozoa varied from 4·8 × 105 to 12·5 × 105 cells/ml of rumen fluid, depending on the feeding frequency and time of the day. Entodinia formed 96·3%, Holotricha 2·0%, Diplodinia 1·3%, and Ophryoscolex 0·4% of the total counts. All taxonomic groups of protozoa reached maximum concentration immediately before feeding and decreased by about 60·80% during 4·12 h after feeding. Larger decreases occurred in animals fed once daily.

Rumen fluid volume varied from 3·12 to 4·47 l but in different ways due to feeding frequency. Diurnal patterns of dilution rate of rumen fluid were the same in animals fed once and twice daily, showing the decrease from 0·98 1/h at 09·00 h to 0·311/h at 01·00 h. It is suggested that some factors other than dilution rate may be responsible for the decrease of protozoa after feeding.

A study of the fractionation of nitrogen isotopes in the diet by cattle is described and the results discussed.

Compared with the diet, urine had a lower ratio of 15N to 14N, but faeces, blood and milk all had a higher ratio.

It is argued that the use of natural 15N as a tracer in grazed ecosystems is more complicated than was at first thought.

Twelve genotypes of cauliflower were grown in two seasons from six seedling propagation treatments in three sequential sowings. There was a high genotypic component of variation for curd weight, indicating that this character can be improved by breeding. A large genotype × environment interaction included genotypic differences in stability to the environment, notably in the self-compatible genotypes. Mean curd weight and stability of genotypes to the environment for this trait were uncorrelated, indicating that high weight and high stability could be bred into a single variety.

Three cultivars of P. vulgaris, tested 39 and 69 days after planting, differed in the extent to which nitrogen (C2H2) fixation and nodule development were affected by plant density.

At the 39-day harvest the climbing cultivar P590 declined in fixation from 15·1 μmol C2H4 produced/plant/h at 8·5 plants/m2, to only 4·2 μmol C2H4 produced/plant/h at 41·5 plants/m2; while the prostrate P498 showed consistently high fixation from 8·5 to 41·5 plants/m2. Variation in nitrogen fixation could be explained largely by change in nodule weight, though specific nodule activity (SNA) was affected, particularly in the cultivar P590. Since the percentage soluble carbohydrate in nodules of two varieties increased at certain planting densities while SNA decreased, some nodule dysfunction is possible.

Density changes affected leaf, root and stem development in all cultivars, leaves on the lower nodes being most severely affected.

At the 69-day harvest two varieties were advanced in filling the pods and showed poor nodulation and limited fixation, even at the widest plant spacings, while nodulation and nitrogen (C2H2) fixation in the third variety, which had just flowered, showed optima similar to the earlier harvest.

The effect of herbage allowance and milk intake upon herbage intake and performance was investigated using 48 Hereford × Friesian calves purchased at 10–12 days of age and reared on reconstituted milk substitute. Groups of 24 calves were fed low (L) or high (H) daily quantities of milk normally associated with 240-day lactation yields of 1000 or 2000 kg. Six calves on each milk treatment were allocated to four daily herbage allowances during the grazing season. These were 20, 40, 60 or 80 g/kg herbage dry matter/kg live weight.

There was no effect of herbage allowance before day 95; thereafter both herbage intake and live-weight gain of the L20 and H20 groups were depressed. The effect was greatest for the L calves. Additional milk consumption reduced herbage intake at all herbage allowances. Milk intake influenced the extent to which calves were buffered from the effects of a low herbage allowance.

From gel filtration studies it has been found that more than 50% of organic phosphorus dissolved in pig slurry is contained in compounds of high molecular weight. Various ions, e.g. calcium, copper, orthophosphate, are bound by these compounds. From the purine and pyrimidine base composition and resistance to acid and alkali treatment it follows that these organic compounds probably are complexes derived from polydeoxyribonucleotides (DNA).

The effect of drying pig slurry at various temperatures (0–100 °C) on the solubility of phosphorus, calcium and copper after redispersion of the dried slurry was investigated. The solubility of organic phosphorus was not affected by drying and redispersion in water, but the amount of phosphorus contained in dissolved organic molecules of high molecular weight decreased on drying at higher temperatures. The solubility of copper was also not affected by heat treatment. The solubility of inorganic phosphorus is mainly related to the solubility constants of mineral phosphates. On the other hand the total solubility of the cations involved is determined by complex formation.

The results of 80 calorimetric experiments with sheep and cattle, mostly conducted in Scotland, were analysed using a generalization of the Mitscherlich equation R = B(l–exp(–pG))–l, where R is daily energy retention and G daily gross energy intake, both scaled by dividing by the fasting metabolism. The relations between gross energy and metabolizable energy were also examined. Methods of fitting the Mitscherlich equation and the errors associated with it are presented.

It is shown that the gross energy of the organic matter of feed can be estimated from proximate principles with an error of ±2·3% (coefficient of variation) and that provided different classes of feed are distinguished, the metabolizable energy of organic matter can be estimated from gross energy and crude fibre content with an error of ±6·9%. Parameters of the primary equation made with cattle agreed with those made with sheep and there was no evidence of non-proportionality of responses on substitution of feeds in mixtures.

The efficiency of utilization of gross energy for maintenance and for body gain of energy was related to the metabolizability of gross energy and, in addition, to fibre or to protein content. Prediction equations are presented which describe these relationships.

It is shown that the primary equation can be manipulated to express a number of biological concepts and that its two parameters B and p can be simply derived from estimates of the two efficiency terms for maintenance and production.

The results are discussed in relation to the design of feeding systems for ruminant animals and to the derivation of optima in their feeding.

Forty Large White × Wessex pigs were fed from 7 to 27 kg live weight, on diets containing either 28 or 14% crude protein. From 27 to 113 kg live weight the pigs were fed a common diet ad libitum. Pigs from each treatment were killed at 27, 54, 82 and 113 kg live weight and the chemical composition was determined. From 7 to 27 kg and from 27 to 113 kg live weight, daily gain, food intake and food conversion efficiency were similar for the two treatments.

At 27 kg, pigs on the lower protein diet were fatter and contained less lean tissue. Between 27 and 54 kg live weight the pigs previously on the higher protein diet deposited a much greater amount of fat than the pigs on the lower protein diet, so that by 54 kg the pigs initially on the lower protein contained less fat. At 82 and 113 kg live weight the pigs given the lower protein diet initially also tended to contain less fat. These findings are discussed with particular reference to the voluntary energy intake of growing pigs.

Two experiments were carried out to examine the effects of restricted food access on the voluntary food intake of pigs given diets of varying energy content or palatability. Where pigs were offered access to food for a restricted time period each day, the voluntary food intake was reduced in relation to the length of access allowed. Compensation was slow, particularly where a low-energy diet was fed. Younger pigs (35–45 kg) compensated faster than heavier pigs (100–110 kg). The responses of the heavier pigs appeared to be similar to those reported for genetically obese rats in their strong reaction to diets of different energy content or palatability.

Observations were made on mating behaviour and reproductive performance during the puberal period in 61 well-grown Perendale (Cheviot × Romney) ewe lambs. In four animals, the first oestrus (as indicated by raddle marks) was not accompanied by ovulation, and three other lambs, though marked by the rams, were not inseminated.

The behavioural responses to a ram, of ewe lambs experiencing oestrus for the first and second times, showed many signs of inadequacy by comparison with those of mature ewes. Individual ewe lambs and mature ewes in oestrus were exposed to a ram in a pen for 3 h, and their responses were ranked on a scale of 1 (full adult response) to 5 (weak response). Of mature ewes 95% scored 1, compared with only 27% of ewe lambs. Across the lambs 59% scored 3 or more, indicating failure of some aspects of the courtship sequences which are required to sustain and reinforce the ram's interest. In a paddock-mating system many lambs showed a strong tendency to disassociate themselves from the rams after each courtship and mating sequence. Consequently there was little evidence of harem formation. Fifty-six per cent of services came in the first 2 h of oestrus, only 14% after the 6th hour and none after the 11th hour.

Duration of the first oestrus in lambs was 18·4 h compared with 29·3 h in mature ewes. Mating the 61 ewe lambs over the first three cycles after puberty resulted in 38 of them being pregnant with 46 foetuses at autopsy in mid to late pregnancy. The success rate did not differ between cycles.

The effect on palatability of crossing Angus with other beef breeds has been studied. Purebred Angus and Jersey × Angus crosses were significantly more tender and of a higher general acceptability than the Simmental × Angus and Limousin × Angus crosses. The possible cause of tenderness differences amongst the cross-breeds is discussed.

This research was conducted to determine the effects of applying N-fertilizer to standard and semidwarf spring wheat varieties on the components of grain yield, and especially on the ability of tillers to develop and produce ears under semiarid conditions. For two growing seasons at Mandan, North Dakota, tillers were identified and tagged according to the leaf axil from which they originated. The survival and development of these tillers, identified as M, T1, T2, and T3 for main stem and tillers from axils of first, second and third true leaves respectively, were observed and measured from emergence to maturity. N-fertilizer was applied at 0, 50 and 270 kg N/ha annually, representing deficient, adequate and excessive N supply.

N-fertilizer application increased grain yield of both varieties, with the increase between 50 and 270 kg N/ha being significant for the standard variety only. Most of this response to N resulted from an increase in the number of ears/ha, arising from reduced mortality of tillers, particularly T2 and T3 tillers during the latter part of the season when water was limited. For a given variety, grain production by M and by T1 tillers was seldom affected by N treatment. Although data were analysed by several means, all results indicate that improved N nutrition enables the later-developing tillers to survive and produce ears more competitively. Final grain yield was closely correlated with N content of a given tiller at the tillering stage, and to dry weight of individual tillers at both tillering and heading. Order of tiller had no appreciable effect on N content of grain. The proportion of final grain yield originating from M decreased from about 60% without N to about 36% for 270 kg N/ha, primarily because of increased survival and production from T2 and T3 tillers following the application of N-fertilizer.

The Br content of soils and herbage from sites in north-west Pembrokeshire was determined. Topsoils had a range of Br contents from 10 to 515 μg/g, with a mean of 54 μg/g, subsoils ranged from < 1 to 455 μg/g, mean 47 μg/g, and herbage samples from 5 to 157 μg/g, mean 45 μg/g.

The topsoil Br content can be related to the loss on ignition and drainage status of the soil; the topsoil Br/loss on ignition ratio becomes smaller with increasingly poor drainage. It was found that the Br distribution in the soil profile is also related to drainage status, the topsoil/subsoil Br ratio increasing with increasingly poor drainage.

There is no clear relationship between soil Br and the amount of the element taken up by the herbage at the same sites.

Root interactions between populations of Lolium perenne, Dactylis glomerata, Holcus lanatus and Anthoxanthum odoratum collected from fertilized and unfertilized plots of the Park Grass Experiment were investigated at two levels of NPK over a period of 3 years.

The root competitive abilities of species were dependent on fertilizer applications and changed with time. For example, L. perenne was more competitive at high nutrient application and during the early stages of the experiment. On the other hand, the root competitive ability of H. lanatus was greatest on unfertilized soil and increased with time. The large effect of root interaction on plant yield and the effects of fertilizer application on this, may be regarded as evidence of competition for one or more of the elements, N, P and K. H. lanatus, the most aggressive species, was more competitive on the unfertilized soil (NIL) than on the fertilized soil (NPK). However, this could not be confirmed by chemical analysis of plant material; there was no conclusive evidence that aggressive species contained higher concentrations of these nutrients when grown in mixtures with less aggressive species. The possibility of allelopathy, the production of toxins by one plant which inhibit the growth of another, cannot be precluded.

The root competitive ability of species and populations was not positively correlated with the yield of species and populations in pure stand. Indeed, negative correlation was found especially on unfertilized soil. In this case varieties or species with a low yield in pure stand were highly successful root competitors in mixtures, while those with high yield in pure culture were poor root competitors.

The present study deals with the reproductive performance of an imported Suffolk flock and the cross-bred ewes resulting from upgrading the local Ossimi sheep with the Suffolk. A total of 1738 ewe records were available for the study.

No significant difference was found between Suffolk and Ossimi ewes in conception rate or proportion of multiple births. However, the Ossimi ewes (mated to Suffolk rams) weaned 25 more lambs per 100 ewes lambing than the imported ewes. The cross-bred ewes were of better reproductive performance than both pure-breds. The best Suffolk cross-bred ewes were those of 40–49 % Suffolk breeding. They weaned 21 more lambs per 100 ewes run with the rams than the local ewes. Reproductive performance of the cross-bred ewes declined with increasing Suffolk genotype above this proportion.

Under the prevailing sub-tropical conditions, the Suffolk ewes have an anoestrous period of 200 days from late January to late July or August; the local ewes showed oestrous activity throughout the year, but with some irregularity.

Lamb and fattening performance and carcass quality of Suffolk x local Ossimi cross-bred lambs are discussed. 1369 cross-bred lamb records over the period from 1957 to 1970 were available for the study. The lambs of 50–59% Suffolk were the best cross-bred group with an advantage of 7–7, 14–2 and 17–1% over the native Ossimi lambs in birth weight, 120-day and yearling body weights, respectively. Generally, lamb performance declined as the Suffolk breeding was increased. However, breed groups variation was not statistically significant, except for birth weight.

Seventy-one weaned male lambs, 4 months of age, from three breed groups: 70–90% Suffolk, 35–45% Suffolk and local Ossimi, were fattened for 16 weeks using two levels of feeding. The two Suffolk cross-bred groups gained slightly more body weight than the local Ossimi. After 8 weeks of fattening, the 35–45% Suffolk lambs gained significantly more weight than the local lambs. However, the local lambs were more efficient in converting food to live-weight gain.

The carcass quality of the Suffolk cross-bred lambs was better than the local lambs, and the advantage was greater for the high Suffolk breeding group.

The effect of herbage allowance on the intake and performance of Scottish Half bred ewes with twin lambs was investigated over the first 16 weeks of lactation. Herbage allowances were defined as g herbage D.M./kg live weight (LW)/day, and were maintained by provision of fresh areas of ungrazed sward each day.

Herbage allowances in the range 25–120 g D.M./kg LW/day were offered on an area of perennial ryegrass (Lolium perenne cv. S. 23). Parturition was synchronized and ewes and lambs were turned out to pasture 1 day after lambing.

Measurements were made of the herbage intake, live-weight change and milk yield of ewes, of lamb growth rates and of the herbage intake of lambs from 10 weeks of age.

Herbage allowance had a significant linear effect on intakes of grass by ewes and lambs. The highest intakes by the ewes were achieved during the second week, and were in the range 23–43 g OM/kg LW/day. Intakes declined, as lactation proceeded, to 19–29 g OM/kg LW/day at week 12. Intakes of lambs were similar in weeks 10 and 12 and were in the range 17–24 g OM/kg LW/day. Allowance had a significant effect on live-weight change of the ewes after the first month and upon final body condition.

There was no effect of allowance on milk yield until week 6. Mean milk yields were 2·3 kg/day at day 14, 1·0–1·5 kg/day at day 42 and 0·7–1·1 kg/day at day 84. There was a positive effect of allowance on growth rates of the lambs after the first month. Mean overall growth rates to 84 days of age were 175–243 g/day.

In order to investigate the characteristics of inverted cassava plantings, seven-node cuttings were planted upright or inverted, and such that four nodes of each cutting were within the soil in a glasshouse. They were observed for 7 weeks. The inverted cuttings sprouted less rapidly, but the percentage of the cuttings which eventually sprouted was not decreased. The inverted cuttings produced more sprouts than the upright ones, and a greater percentage of their sprouts were produced below ground than for the upright cuttings. At 5 and 7 weeks, the total leaf area per cutting was less for the inverted cuttings. The number of leaves per cutting did not differ between the treatments.

In a field experiment comparing upright and inverted stem pieces, field emergence and tubering were slower in the inverted cuttings. Yield per plant and per unit area was significantly lower for the inverted cuttings. In the upright planting, most of the tubers originated at the lowest extremity of the cutting and formed a compact bunch there. For the inverted planting, most of the tubers arose from the shallower-lying submerged nodes, but the tubers did not form a compact bunch. The inverted planting had a lower percentage of its tubers lying along the ridge. In a few of the inverted plantings, but not in the upright, the bases of some stems became tuberous. The treatments did not differ with respect to mean tuber length, radius of spread of the tuber tip, and the number of major stems per plant.

The use of non-radioactive ruthenium phenanthroline (Ru-P) and chromium EDTA (Cr-EDTA) as dual phase markers of digesta flow was examined and compared with chromium sesquioxide (Cr2O3) in conjunction with spot samples of digesta collected from T-shaped cannulae situated in the proximal duodenum of weaned calves.

In vitro estimates of organic matter digestibility indicated that on a cubed barley diet, Ru-P exhibited toxic effects at concentrations on 2·2 × 10–5 M and above. No such effects were noted with Cr-EDTA. Subsequently satisfactory infusion rates of 12 mg Ru and 280 mg Cr/kg dry-matter intake were established.

Daily flows of organic matter, starch, nitrogen, fibre, sodium and potassium at the proximal duodenum were calculated by the dual phase marker system and by Cr2O3, and regression equations relating these two for each dietary component were calculated. Examination of the intercepts revealed that they all differed significantly from zero (P < 0·05) whilst all the regression coefficients were significantly different from unity (P < 0·05), thus indicating that Cr2O3 underestimated nutrient flows at low flow rates and overestimated them at high flow rates relative to the corresponding estimates based on Ru-P plus Cr-EDTA.

The efficiency of utilization of the energy of the food by growing pigs of the Large White breed was measured. Ten diets had a digestible energy varying from 75·3 ± 0·91 to 85·7 + 0·81% and a metabolizable energy from 72·3± ·92 to 83·4±0·64% of the gross energy. Net energy was 85·2±3·20% of the metabolizable energy (ME).

Regression calculations resulted in the following estimates: a maintenance requirement of 151 kcal ME for growing pigs weighing 9–58 kg and efficiencies of 66·7 and 100% for the utilization of ME for protein and fat accretion, respectively.

Feeding regime (ad libitum or restricted at about 80% ad libitum) did not influence food utilization.