A two-pool + time delay model was used to analyse ideal marker concentration patterns generated, using an interactive computer simulation program, from data for the mean retention times of [51Cr]EDTA and [103Ru]phen in the reticulo-rumen, abomasum and caecum-proximal colon and the transit times of these markers through the omasum, small intestine and distal large intestine of sheep. Although providing a reasonably close fit to the generated data, the fitted curves showed small but systematic deviations, indicating that the model does not consistently characterize the kinetics of the markers in the ruminant gastro-intestinal tract.

When the components of the two-pool model were correctly identified, predicted rumen mean retention times (MRT) were within – 1 to + 13% of the observed values. However, identifying the component with the longer MRT as the rumen resulted in up to 2·6-fold overestimation (17·5 v. 6·77 h). The model underestimated the time delay and the overall MRT. It is suggested that the correct identification of the two components can be achieved by the simultaneous use of a solute-and a particulate-phase marker because, in ruminants, they do not behave independently in the caecumproximal colon.

Genetic analysis for eight morphological traits, number of days from sowing to first flower, to complete pod filling, and to first mature pod, height of plant from the ground to the first fruiting node, distance between the first and last fruiting nodes, number of nodes from the ground to the first pod-bearing node, average internode length and number of flowers per axil, was done by following numerical and graphical approaches in a nine parental half diallel. Components as well as the graphical approach showed the importance of non-additive gene effects for height of plant from the ground to the first fruiting node, number of nodes from the ground to the first pod-bearing node and number of days from sowing to first mature pod, while for other traits additive genes were important. The high performance of number of nodes from the ground to the first pod-bearing node and number of flowers per axil was governed by recessive alleles while other traits were governed by dominant alleles. Consequently for developing an efficient plant type hybridization between parents like P23, EC109182, EC109196, LMR200 and LMR8 is advocated. Leafless segregants from the present set of crosses which exhibited potential for high yield in national tests have been isolated.

Generalized lattice designs (a member of the class of incomplete block designs) have been used in 13 potato variety yield trials over 3 years. Results from these designs are shown to be generally more precise than from comparable complete block designs.

One hundred and eighty triple test cross families arising from three barley crosses (C 164 x EB 1556, BG 25 x NP 21 and BH 15 x RD 103) were grown in two blocks of a randomized-block design in saline-alkali soil prepared in micro-plots. The families were evaluated for number of days from sowing to heading, plant height, number of tillers per plant, ear length, number of grains per ear, 100-grain weight and grain yield per plant. The cross BG 25 x NP 21 showed epistasis only for number of days toheading and number of grains per ear; in contrast, epistasis was present in all traits in BH 15 x RD 103. In cross C 164 x EB 1556, epistasis was detected for plant height, ear length and number of grains per ear. Thus, epistasis appears to be related to specific cross combination. The ‘j and l’ type epistasis was more pronounced than the ‘i’ type. Early generation selection may be used for number of days to heading which Exhibited epistasis marginally with preponderance of additive gene effects, while for the remaining traits selection should be deferred till an advanced generation.

Field and pot investigations of the vegetative and early reproductive growth of a winter wheat and a winter rye cultivar over three seasons (1978–9, 1980–2) have shown that higher and earlier forage yields of rye are due to a combination of factors, notably more rapid rates of germination, crop emergence, leaf appearance and leaf expansion coupled with higher leaf area ratios. There was no evidence, from studies of net assimilation rate, that the photosynthetic apparatus of rye plants is better adapted than wheat to the low temperature and light conditions of winter and early spring. However, the earlier initiation of rye stem extension was associated with significant increases in net assimilation rate, which compensated for reductions in the leaf area ratio. Practical aspects of these results are discussed briefly.

Neem (Azadirachta indica juss) seed kernel cake was water treated and dried in the sun. It was palatable to cattle, despite its bitter smell.

Twelve growing calves were divided into two equal groups; one group (control) had a standard concentrate mixture consisting of crushed maize 30 parts, groundnut cake 30 parts, wheat bran 38 parts and in the second group (experimental) the concentrate mixture had crushed maize 30 parts, neem seed kernel cake (water washed) 45 parts and wheat bran 23 parts. Both the mixtures had common salt and mineral mixture 1 part each. The roughage fed was the same in both groups.

The mean growth rate of calves in 273 days was 403 g/day in the control group and 344 g/day in the experimental group which did not differ significantly (P > 0·05). The dry-matter intake, digestibilities of all the organic nutrients, total digestible nutrient values and the balances of nitrogen, calcium and phosphorus remained similar (P > 0·05) in the two groups. The blood haemoglobin, serum inorganic phosphorus and the activity of serum alkaline phosphatase, serum acid phosphatase, serum glutamic-pyruvic transaminase and serum glutamic-oxaloacetic transaminase also did not differ significantly (P > 0·05) in the two groups.

It is concluded that water washing of neem seed kernel cake very largely removes toxic principles responsible for retardation in growth.

To determine economic thresholds of pest infestation caged plots of oil-seed rape (Brassica napus L.) were infested with different populations of the seed weevil (Ceutorhynchus assimilis Payk.). Less than one seed weevil per plant resulted in pod infestation levels of seed weevil larvae that by themselves were insufficient to warrant insecticide application, but owing to secondary infestation of pod midge (Dasyneura brassicae Winn.), substantial seed loss occurred. Greater populations of seed weevil adults gave correspondingly larger levels of pod midge and diminishing yields.

In commercial crops individual plants were able to compensate, and even to overcompensate for damage resulting from low levels of pest infestation, but increasing levels of infestation resulted in progressively fewer seeds per plant.

The implications of the results on pest control and further research are discussed.

Main-stem apical development and its inter-relations with other aspects of plant morphology were studied in seven field crops of winter wheat (Triticum aestivum L., cv. Maris Huntsman).

Apical primordia were produced slowly in autumn and winter, then faster in spring as the weather became warmer. Spikelets were initiated about three times as fast as leaves. Leaf initiation ended at around the time that tiller bud initiation stopped. Apical dome length and diameter both increased during leaf initiation, reached a maximum at double ridges and then decreased. Double ridges appeared when very nearly 50% (range 49–52%) of the final number of spikelets was present. Spikelet initiation ended a few days after the first florets were initiated and when stem extension began, but usually before the stem apex rose above the soil. Floret initiation finished at about the time that the flag leaf appeared. Throughout tillering there was a strong association between tiller emergence and leaf appearance.

There were considerable differences between seasons in the timing of developmental events on the apices of main stems, but a difference in sowing date of 5 months was reduced to little more than 1 month in the timing of anthesis and the maximum numbers of organs varied only slightly with sowing date.

Methods of controlling Sitona lineatus adults and larvae were tested in 13 experiments on spring-sown beans, four on autumn-sown beans and two on dry-harvested peas. A total of 16 insecticides were used, though not all combinations of insecticide, application method and crop were tested. Applications included granules or sprays to the foliage, seed-bed treatments, seed-furrow treatments and seed treatments. Phorate as a furrow treatment at sowing at 1·24 kg a.i./ha increased yields of spring-sown beans by an average of 0·5 t/ha but was not persistent enough to protect autumn-sown beans from attack. Foliar applications of systemic insecticides (carbofuran or carbosulfan) at similar doses decreased attacks but effects on yield need further evaluation. Preliminary work indicates that seed-bed or furrow treatments of phorate can also be used to control S. lineatus on peas.

The effect of ratios of calcium to phosphorus in the diet (varying from 0·6 to 3·6) on the absorption and excretion of P was investigated with four sets of 9-month-old chimaera-derived triplets. A pelleted cereal-based diet supplemented to contain 1·5, 3·1 or 6·2 g P/kg D.M. and 3·4 or 5·4 g Ca/kg D.M. was used in a factorial design.

The additional Ca in the diet reduced the efficiency of absorption of the P supplements in the diet by 0·18 ± 0·04.

The efficiencies of absorption of total P were very similar within but markedly different between (P < 0·001) sets of triplets, the mean values being 0·62, 0·74, 0·82 and 0·84. The fractional absorption of inorganic P alone showed the same ranking and the mean values were 0·47, 0·67, 0·85 and 0·92. These differences between triplets support the view that the individual differences in P metabolism have a genetic basis. The mean absorbability of P in the basic diet (0·77) and in the P supplements (0·73) were similar.

The pattern of excretion of absorbed P between the faecal and urinary route of excretion varied between the sets of triplets; as P intake increased, the additional absorbed P was excreted in faeces by one set, in urine by another and in faeces and urine by two sets. The relative importance of the faecal route was dependent upon the fractional absorption of P secreted into the gut.

Five experiments which studied the effects of a wide range of dates of planting on contrasting potato varieties in Pembrokeshire are reported. In three experiments (1976–7) four early varieties (Home Guard, Arran Comet, Irish Peace and Ulster Sceptre) were sprouted from the end of dormancy and compared at four dates of planting, which began as soon as soil conditions allowed (February in 1975 and 1976 and March in 1977). In these experiments all early-emerging treatments were damaged by frost and in 1975 and 1976 date of planting had little effect on leaf area index or yield. In 1977 planting in late April delayed and increased peak leaf area index but reduced yields throughout harvesting. In all experiments the emergence of varieties was affected by date of planting. The varieties with the longest sprouts emerged first only from the earliest plantings; at late plantings all varieties emerged together, which suggests that rate of post-planting sprout elongation decreased in this old seed as planting was delayed despite increasing soil temperatures. The implications for testing of early varieties are discussed.

In two further experiments two early varieties (Home Guard in both years and Red Craigs Royal and Arran Comet in 1 year) were compared with three maincrop varieties (Désirée, Maris Piper, Stormont Enterprise) using seed which did not begin to sprout until January at dates of planting beginning in March. Sprout length was again poorly related to earliness of emergence. Delaying planting delayed and increased peak leaf area index in all varieties but only increased yields in the early varieties which had the smallest leaf areas. In maincrop varieties date of planting had little effect on final yields. In these years there were long periods without rain and in 1976 yields were limited by the amount of water available from the soil, for as each treatment exhausted this supply bulking ceased.

Soya-bean meal and rapeseed meal treated with 0, 0·4 or 0·8 g formaldehyde/100 g crude protein (N × 6·25) was incubated in the rumen in nylon bags with 10 and 40 μm aperture.

Disappearance of dry matter and nitrogenous compounds was reduced with increasing formaldehyde treatment.

The proportion of acid-pepsin soluble nitrogen in the undegraded residues of untreated and treated soya-bean meal was similar to the original samples. For rapeseed meal the proportion of acid-pepsin soluble nitrogen in the undegraded residues decreased with increasing rumen incubation time. This reduction decreased with increasing formaldehyde treatment.

Concentration of amino acids in the undegraded residues did not generally deviate from those in the original samples. However, a distinguishable decrease in the methionine concentration was observed in all the rapeseed meal samples and in glutamic acid concentration in rapeseed meal treated with 0 and 0·4 g formaldehyde/100g- crude protein.

Most of the changes due to rumen incubation were smaller using the 10 μm bags than using the 40 μm bags. However, the bag pore size did not play a decisive role in the conclusions of the results given.

A scheme was developed to describe how the rate at which apical primordia are initiated in cereals depends on temperature and photoperiod. It was used to analyse initiation in field crops of winter wheat (Triticum aestivum L., cv. Maris Huntsman).

For the initiation of leaves and spikelets, a straightforward linear regression of initiation rate R against mean air temperature (Ta) gave base temperatures (Tb) close to 0 °C for leaves and for spikelets. However, initiation rate was also correlated with mean photoperiod (P) and base photoperiods (Pb) of –0·5 h and 4h were established for leaf and spikelet initiation. When R was correlated with the index (T – Tb) (P – Pb), r2 was 0·62 for both leaves and spikelets.

Measurements were taken on 36 laying hens, 46 growing female turkeys and 36 broiler chickens using modified abdominal fat calipers to determine the prediction of abdominal fat in different classes of poultry. Four pairs of caliper measurements were taken on each bird by three operators (layers and turkeys) and one operator (broilers). The live laying hens and the plucked turkey carcasses were also scored for fatness. The caliper measurements were significantly related to the proportion of abdominal fat (g abdominal fat/kg body weight) in all three groups of birds. The correlation was greater in laying hens (0·81) and turkeys (0·76) than in broilers (0·51). There were significant operator effects upon the prediction of abdominal fat. In each case the measures obtained by two practised operators gave better prediction of abdominal fat than those from an unpractised operator.

Data from nine experiments from 1973 to 1981 which examined the effects of physiological age on sprout and field growth of early potato varieties are reported. Length of longest sprout per tuber and all aspects of field growth were related to number of daydegrees > 4 °C experienced by the seed after onset of sprout growth (measured as the appearance of a 3 mm sprout). It is, therefore, suggested that this scale is an effective measure of physiological age. In Home Guard and Maris Bard, increasing age of seed tubers resulted in earlier emergence and tuber initiation, larger early leaf areas and increased early tuber yields. As growth proceeded young seed produced the largest and most persistent leaf areas and the yields surpassed those of older seed and in some experiments yields decreased with increasing age at the final harvests.

Optimum ages for specific harvesting periods were determined from regressions of tuber yield on age. In both varieties, they decreased with delay in harvesting. However, optimum ages differed in the two varieties and the implications for production and storage of seed and testing of varieties are discussed.

Five Romney wethers, fitted with rumen fistulae, were each fed five pelleted diets high in starch (30–50%) containing 0·72, 1·22, 1·72, 2·47 and 3·72% N respectively. Samples of rumen liquor were incubated with glycerol-tri-[1-14C]oleate or with [1-14C]- linoleic acid. The rates of lipolysis or hydrogenation of these substrates were measured. In addition rumen contents of the sheep when fed the 1·22% N diet were incubated with radioactive substrates plus 0, 100 and 200 mg finely ground casein.

It was found that there was an approximately linear increase in the rate of lipolysis between 0·7 and 2·5% N. The rate of hydrogenation did not increase below l·2% N and tended to decrease above 2·5% N. The potential for hydrogenation of unesterified linoleic acid was calculated to be 4–6 times greater with all diets except that containing 1·2% N. This may be one explanation for the elevated concentration of the rumen unsaturated fatty acids in sheep fed diets containing ca. 1–1·5% N.

It was also established that the addition of finely ground casein to the incubate was without effect.

It was concluded that microbial composition is important in regulating the relative rates of lipolysis and hydrogenation which determined the amount of unsaturated dietary fatty acid present in the rumen.

Results of a 2-year study in a rainforest zone of south-western Nigeria to determine the effects of various planting and harvesting times on the yield, HCN, dry-matter accumulation and starch contents of cassava showed that times of planting and harvesting significantly affected all the variables studied. May planting gave highest yield arid starch contents, which suggests that large-scale production of cassava for industrial starch and human consumption should be planted in the month of May.

The harvesting time experiment shows that cassava tuber will continue to increase until the 24th month, although, because of increasing demand for land, it will not be economic to leave cassava on the field for more than 15 months. For optimum starch and dry-matter accumulation, cassava should be harvested between 12 and 15 months.

Results are presented from two experiments (1973 and 1974) in which high potato yields were obtained (60–70 t/ha). In both, Désirée and Maris Piper accumulated much more N and K (> 200 and 300 kg/ha respectively) than was applied as fertilizer (160 kg N and 189 kg K/ha). Increasing planting density (to levels above commercial practice) increased nutrient accumulation but had only small effects on yields. Thus, high yields are associated with but not necessarily caused by large accumulations of nutrients. As a general principle, increasing fertilizer rates above those shown to be optimal will not increase yields.

The body composition of young mammals has been investigated in relation to environmental temperature and energy intake. Piglets were weaned at 14 days and then kept separately at 35 or 10 °C and fed either a high or a low energy intake. The animals were killed at 38, 48, 56 or 64 days of age and the carcass divided into four compartments: superficial tissue (skin and subcutaneous adipose tissue), muscle, contents of abdomen (gastro-intestinal tract, liver and kidneys), contents of thorax (heart and lungs). Each compartment was analysed for fat, nitrogen and energy content.

The results were analysed using a non-orthogonal analysis of variance in oider to investigate the separate effects of environmental temperature and energy intake, to test for possible interactions between these two factors, and to assess the time it takes for any effects to develop.

The total amount of fat stored in the body was greater in the pigs kept at the high temperature than in those kept at the low temperature and increased with an increase in food intake; there was no evidence of an interaction of temperature and diet, suggesting that their effects were exerted independently. The extra fat was stored mainly in the superficial tissue and muscle, but partly also in the deep body compartments. However, when expressed as a percentage of the total fat store a greater proportion was found in the deep body compartments of those kept at the low temperature and on the low intake, although the absolute quantities of fat involved were small.

The nitrogen content was also greater at 35 than at 10 °C, and on the high than low intake. Most of the nitrogen was present in the muscle and the proportion of the total body nitrogen stored here was greater in the warm than in the cold, whereas it was unaffected by energy intake. The energy contents of the tissues measured by bomb calorimetry and estimated from the chemical composition were similar. For animals kept at 35 °C most of the energy was stored in the superficial tissue, with the muscle as the second highest store. By contrast, those in the cold stored most of their energy in the muscle.

The present investigation has thus highlighted the large and partly independent effects that environmental temperature and food intake can have on the distribution of energy within the body and the chemical form in which it is stored.

Three varieties of triticale (TL-238, TL-257 and TL-319) bred by the Plant Breeding Department of Punjab Agricultural University were studied for nutrient composition and metabolizable energy (ME) content for egg-type chicks. A feeding trial was also conducted to study the suitability of triticale as a replacement for maize in conventional high- and low-cereal diets for different classes of egg-type chickens.

The crude protein contents of TL-238, TL-257 and TL-319 were respectively 13·4,14·4 and 2·1%. Corresponding values for starch content were 51·5, 49·2 and 54·3%, respectively. ME in triticale varieties closely followed the trend of starch content. Accordingly TL-319 was higher in ME (13·58 MJ/kg D.M.) than TL-238 and TL-257 (12·91 and 12·49 MJ/kg D.M. respectively). There were no significant differences in body-weight gain or in food conversion of chicks fed diets containing different varieties of triticale. The substitution of triticale for maize in a conventional high-cereal diet improved growth and food conversion of starter chicks. In a low-cereal diet, however, triticale had an adverse effect on the growth rate and food conversion of starter chicks. At the end of 18 weeks of age, the differences in body-weight gain, food conversion and efficiency of protein utilization by chicks on all the treatments were not significantly different (P > 0·05). Results of the production phase showed that egg production, egg mass, food conversion and energetic efficiency were significantly (P < 0·05) improved by feeding triticale.