In an experiment involving sixty Large White pigs fed maize or barley based diets either ad libitum (AL) or to one of two restricted scales (R1 and R2), between 55 and 86 kg live weight, there were no significant cereal × feeding interactions for growth rate and the mean growth rates for the main effects were 0·62, 0·63, 0·81, 0·73 and 0·35 kg/day for the maize, barley, AL, R1 and R2 treatments respectively. There were no significant cereal × feeding treatment interactions for iodine number or calorific value of carcass backfat and the only significant differences between the main effects were those of lower iodine numbers for the barley (cf. maize) and the AT. (cf. R1) treatments.

Feeding of white clover or red clover oestrogenic diets to wethers produced increases in teat length but did not affect the basal plasma luteinizing hormone levels or pituitary sensitivity to luteinizing hormone-releasing hormone.

Hens and cockerels of a White Leghorn strain (‘H & N’) were kept at a constant temperature of 23 °C from 1 year until 2¼ years of age. The mean fasting heat production, which was measured 6 times during this period, varied between 404 and 464 kJ/kg0·75/day for the hens and between 223 and 349 kJ/kg0·75/day for the cockerels. The sex difference in heat production is discussed and an attempt is made to explain the variation in heat production for each sex.

Plasma free fatty acid (FFA) concentrations are generally a reflexion of the extent of mobilization of depot fats (Frederickson & Gordon, 1958). In non-fasted sheep values are low, usually in the region of 100–200 μ-equiv./litre plasma, but occasionally values up to 500 μ-equiv./litre have been noted in fed, unstressed sheep (Leat & Ford, 1966). To obtain information on the variation in the concentration of plasma glucose and FFA, sheep were studied over a period of two seasons.

Three experiments involving three early maincrop cultivars explored the effect of nitrogen fertilizer (0–301 kg N/ha) applied to seed potato crops on seed performance and the growth of the subsequent early ware crop.

The tuber N-content ranged from 1·1 g N/100 g dry matter (D.M.) to 1·6 g N/100 g D.M. for seed tubers obtained from crops grown at 0 and 201·301 kg N/ha. Seed of cv. Maris Peer from crops given 100 kg N/ha in 1969 produced ware yields 10% and 24% higher than those obtained from seed from crops given 0 and 201 kg N/ha. No effects of fertilizer applied to the seed crop on subsequent growth were observed in the other two experiments.

It is suggested that the effects of nitrogen fertilizer applied to the seed crop on subsequent growth other than that related to seed tuber size only arise as a result of effects on the maturity of the seed crop. Thus any observed effect is attributed to differences in the ‘physiological age’ of seed rather than to differences in seed tuber N-reserves.

The heat production of hens and cockerels of a White Leghorn strain (‘H & N’) was measured after acclimation to environmental temperatures of 16, 23, 27 and 33 °C. No difference in fasting heat production was found between 16 and 23 °C for well-feathered hens in the first few months after moult though there were substantial reductions at 27 °C and above. Both hens and cockerels showed a trend of increasing net availability of metabolizable energy with increasing environmental temperature though this was non-significant. There were significant reductions between 16 and 27 °C in the metabolizable energy requirements for maintenance for both sexes.

Results are also given for the heat production of laying hens exposed to short daylight periods and high or low environmental temperatures. Although the mean fasting heat production of the high-temperature group was greater, the difference was not statistically significant.

Distribution of red cell potassium in buffaloes and its possible genetic control was investigated. The mean values of red cell K+ varied between 37 and 41 m-equiv/l in LK type animals and between 87 and 91 m-equiv/l in the HK type. Red cell K+ concentration within individual animals of either LK or HK type was fairly stable over successive samplings, whereas the same values among animals within a type varied rather widely. The inheritance of red cell K+ type in buffaloes appeared to be controlled by a single pair of genes. HK animals were homozygous for the recessive allele while LK animals represented the heterozygotes and also the homozygotes for the other allele. In addition, there was indication that the gene responsible for LK phenotypes might not be completely dominant over the recessive allele. The three populations of buffaloes examined were found to be in genetic equilibrium in respect of red cell K+ polymorphism. HK animals predominated in both the breeds, the frequency of the recessive gene (h) being 0·78 and 0·74 for the Murrah and Bhadawari breeds respectively.

The technique of regression on environmental index is used to examine the behaviour of varieties in monoculture and mixture. It is shown that, sometimes, single regressions for each variety do not provide an adequate explanation of the interactions between varieties and environments.

Two experiments were made in each of the seasons 1971/72 and 1972/73 to determine the effect of seed treatment on groundnut emergence.

In one of the experiments, groundnut seed germinated at a faster rate when the seed was dressed with Aldrex T at 2·2 g/kg of seed.

In the other experiment, no difference in emergence was found between varieties whether planting was on the same day as shelling or 12 weeks after shelling.

The reproductive performance of breeding and cyclic Welsh Mountain (WM) and Border Leicester (BL) ewes was compared in two contrasting photoperiodic environments during January 1971–April 1972. Treatment 1 consisted of natural daylength changes at latitude 51° 43’ N. There was no difference between the two breeds in onset of the breeding season, percentage exhibiting oestrus or percentage lambing. The breeding season of BL ewes terminated earlier (mean date, 31 January) than that of WM ewes (mean date, 9 March). The WM ewes had 8–12 oestrous periods and the BL ewes 7–11 oestrous periods. In treatment 2 a simulated equatorial photoperiod (13 h light: 11 h dark) was applied from January 1971 but was inadvertently interrupted by a short period of continuous light in June 1971. All WM ewes exhibited oestrus compared with 37·5% of BL ewes. The failure to show oestrus in the majority of BL ewes contributed to the marked difference between breeds in the percentage of ewes lambing: 88·9% in WM compared with 11·1% in BL ewes. In the cyclic subgroup, the WM ewes had 3–10 oestrous periods and the BL ewes, 2–7 oestrous periods.

It is concluded that the breeds showed a differential response to the two treatments and that Treatment 2 had a marked adverse effect on the reproductive potential of the Border Leicester ewes.

The possible adaptive significance of the occurrence of HK and LK red-cell types in Murrah buffaloes was investigated. Judged by haematological indices and thermorespiratory responses under conditions of moderate thermal stress, LK animals appeared to have a greater adaptive potential than HK animals in a hot arid environment. Dry matter percentage, packed cell volume (pcv), haemoglobin concentration (Hb), red blood corpuscles (RBC) and plasma protein values were significantly higher in LK-type animals. In addition, under identical conditions of thermal stress the LK animals exhibited significantly less rise in rectal temperature and respiratory rate than the HK animals.

To measure the accumulation of Pb in an area 42 km from London and within 2 km of the A5, A6 and M1 trunk roads, the Pb contents of topsoils collected from sites at Rothamsted Experimental Station since 1881 have been determined. From 1883 to 1972 the increases ranged from 17 to 46% but because of the variable Pb contents within fields, the absolute rate of accumulation is difficult to determine. The Pb content of herbage harvested twice yearly since 1920 has not increased noticeably.

Two field experiments were conducted in 1971–72 and 1972–73 on two similar sites of calcareous clay soils (vertisol) with paste pH 8·2, 0·024% and 0·22% organic carbon. Wheat (Triticum aestivum L. var. (LR N10) An3) was grown and the fertilizers ammonium sulphate, urea, nitrophoska 15% N, 15% P2O5, 6% K2O), calcium nitrate (Ca NO3)2·4H2O) and ammonium sulphate nitrate were each used at 70 kg N/ha at seeding, tillering, jointing or ear emergence and there was one treatment with no N fertilizer. The treatments were arranged in a randomized block design with four replications. Each plot was 6·0 x 7·0 m of which 4·0 x 5·0 m was harvested. N fertilizers were broadcast by hand and no basal potassium or phosphorus were added since they are known to have no effect on wheat yield on these soils. Seed a rate equivalent to 85 kg/ha was weighed separately for each plot and sown by hand in rows spaced 20 cm apart. Each experiment received 10 irrigations, each equivalent to a head of 10 cm of water, at 10-day intervals.

The gross energy of forages can be classified into three fractions, namely the unavailable fraction, the digestible energy fraction and the potentially digestible energy (PDE) fraction. The PDE fraction can only be made available by appropriate treatment and supplementation (Pigden & Heaney, 1969). In young forages the PDE fraction is relatively insignificant, but as the plant matures, the PDE fraction increases very rapidly. By treating matured forages with delignifying agents, increased nutrient digestibilities have been demonstrated Chandra & Jackson, 1971; Wilson & Pigden, 1964), but no significant improvement on the voluntary intake was achieved unless the treated material was supplemented with a source of nitrogen (Donefer, Adeleye & Jones, 1969). While Zafren (1960) used ammonium hydroxide (NH40H) as the treatment alkali, with the claim that the ammonium acetate resulting from the neutralization of the excess alkali could serve as an extra source of nitrogen in the treated straw, other investigators (Donefer et al. 1969) have adopted the method of supplementing the treated straw with a source of nitrogen. Since the efficiency with which dietary nitrogen is converted to microbial nitrogen in the rumen has a considerable influence on the efficiency the animal as a whole, studies herein reported were carried out to test the effectiveness with which rumen micro-organisms utilize different nitrogen sources in degrading cellulose in vitro.