The effects of supplements of protein meal or sorghum grain given to young cattle for 140 days during their first winter and spring post-weaning, were recorded over 560 days for cattle grazing on low quality pastures in subtropical Australia. The supplements were offered to steers in four treatment groups, replicated three times, at the following rates per head to late spring: (a) mineral mix (M) + cotton-seed hulls, 90g/day (control), (b) M + protein meal, 600 g/day (protein daily), (c) as for (b) but at 2·1 kg/3·5 days (protein twice-weekly), or (d) M + sorghum grain, 560 g/day (sorghum). For the next 130 days, to late summer, only supplement (c) was continued while the remaining three groups were not supplemented. None of the supplements was offered for the final 290 days of the experiment when the steers grazed an improved pasture.

At the end of the first spring, the live weight of the steers supplemented daily and twice-weekly with protein was respectively 229 and 216 kg. These were significantly (p < 0·01) heavier than the sorghum-supplemented (174 kg) or control steers (160 kg). At the end of the first summer, the steers given supplements of protein meal twiceweekly, or daily, remained significantly heavier (265, 250 kg respectively) than sorghum-supplemented or control steers (209, 198 kg). By the second summer, the steers previously given protein supplements were still heavier than the steers from the control group (357 v. 317 kg, respectively).

In steers which were offered the protein supplement during winter and spring, samples of blood taken at the end of spring had lower (P < 0·01) plasma ratios of glycine to branched-chain amino acids (valine, leucine and isoleucine) and a lower ratio of methionine: valine, than in the steers which were not offered the supplement. These ratios were significantly (P < 0·05) correlated with live-weight change over the preceding 140 days. On this basis it was considered that the improved growth of the steers offered the protein supplements was associated with an increased availability of specific essential amino acids, which may have initiated in the steers an increased appetite for pasture D.M.

Adult goats provided with permanent jugular and portal vein catheters were used to study the relation between spontaneous meals and blood composition in free-feeding goats in order to determine which constituents might fulfil a feedback signal function in the control of feed intake. Animals were fed ad libitum concentrates, supplemented with a small amount of hay. Blood samples were collected before, during and after spontaneous meals by means of a remote sampling system and were analysed for volatile fatty acids, glucose, insulin, glucagon and growth hormone.

In a preliminary experiment the relationship between body weight, voluntary feed intake, blood glucose and plasma insulin was examined in goats fed ad libitum concentrates and hay for 18 weeks. The data indicate a regulation of energy balance through control of feed intake. Since an increased glucose and insulin concentration was observed concomitantly with a decline in feed intake, glucose and/or insulin may fulfil a signal function in the control of energy balance.

Spontaneous meals were not preceded by a systematic change of any of the above blood constituents. Therefore, it is unlikely that meal initiation is governed by one of those. In contrast, spontaneous meals resulted in a rapid increase of insulin during eating (P < 0·025) whereas no clear changes were observed for the other substances. Thus, insulin might be a candidate for a feedback function in the control of meal duration.

Field experiments were conducted for 2 years (1977–8 and 1978–9) at the Indian Agricultural Research Institute, New Delhi under semi-arid seasonally dry tropical conditions to evaluate the possibility of growing two crops under natural precipitation, where traditionally one crop is grown. Short-season fodder crops of cow pea (Vigna unguiculata), guar bean (Cyamopsis tetragonoloba), moth bean (V. aconilifolia), soya bean (Glycine max.) or pearl millet (Pennisetum typhoides) harvested before the end of monsoon rains enabled sufficient recharge of the profile from the precipitation received subsequently to enable barley to be sown in the winter season. Although the pearl millet yielded more biomass, the soil fertility enrichment was greater from the legume fodders. The grain yield and total nitrogen removal by barley was higher after the legume fodders than after the non-legume fodder pearl millet. Benefits from the previous fodder legumes were equivalent to or more than 40 kg N/ha applied to barley crop following a previous crop of pearl millet.

Phaseolus vulgaris (cv. Provider) was assessed as a vegetable and seed crop in southeast England. Experiments were designed to simulate ‘pick your own’ harvest systems which are becoming increasingly popular. Edible pods were removed on either one or two occasions at varying developmental stages, remaining pods being left to produce seed. The yield of edible pods increased considerably as pod removal was delayed but subsequent seed yield was reduced. However, depodded plants showed compensatory increases in mean seed weight so that seed yield reduction was less than expected.

Results are discussed in relation to decline in seed moisture content and the dual use of this crop for vegetable pod and seed. It is concluded that dual use is not convenient for large-scale agricultural operations. ‘Pick your own’ programmes utilize the potential of this crop more efficiently than present mechanical harvesting systems.

Following the measurement of tritiated water (TOH) spaces, 31 cattle were slaughtered and chemically analysed in this study. They included several breeds, both females and castrate males, and were of varied nutritional history. Their body-fat content ranged from 4 to 21% of fasted live weight.

Total body water (including the water in the gut contents) was reliably estimated from TOH space, measured after allowing an overnight 16 h waterless fast for TOH equilibration. Following this regime, residual D.M. in the gut contents amounted to 1·75% of fasted live weight. The relationships of body fat to body weight, and body fat to body water when both were expressed as percentages of body weight, were too variable to be used in any predictive fashion. Equations were derived, using fasted live weight, allowing the accurate estimation in vivo of the quantities of the chemical components in the whole body (i.e. total body minus D.M. in gut contents).

It was demonstrated that the sum of total body water and total body fat constituted virtually 80% of total body tissues, and that total body protein closely approximated 80% of the fat-free dry matter, in cattle varying widely in body condition. These relationships constitute the physiological basis of the equations presented.

Comparable principles appear to apply to sheep, and a range of other mammalian species.

Non-breeding groups, I, II and III, each with six high-potassium (HK) and six lowpotassium(LK) Chokla ewes were given water once in 24, 48 and 72 h respectively. In the next summer, seven ewes (4 HK and 3 LK) from each group I, II and III were switched over to a watering schedule of once in 24, 72 and 96 h respectively and were naturally bred. All the animals were maintained on grazing alone.

Water deprivation for 72 h caused 18·8 and 19·2% body weight loss in HK and LKewes respectively; an overall average maintenance of weight loss in LK ewes was significantly higher than in HK ewes from the same group. There were significant differences in water intake due to treatments only. The HK and LK ewes from groups I and III showed a similar trend.

Pregnant ewes of HK and LK types given water once in 96 h lost 21·7 and 23·8% of their body weights respectively. Corresponding weight loss in aborted ewes were 23·8 and 33·3%. Two ewes, each from 3 LK and 4 HK animals aborted owing to water deprivation for 96 h. The water intake reached 30 and 36·5% of body weight in LK and HK pregnant ewes given water intermittently.

The wool attributes of non-pregnant ewes did not indicate a significant influence of blood potassium types. Four out of five ewes of the LK phenotype died during 3 years, irrespective of watering schedule.

An analysis of yield data from 31 tea clones grown in replicated trials at four locations revealed the presence of significant genotype-environment interactions. Joint regression analysisshowed that a significant proportion of these interactions could be attributed to differences in the linear response of each genotype (clone) to the range of environments. However, estimates of the deviations from regression were also significant, indicating the presence of some unpredictable variation.

The response of each individual clone was estimated by computing the regression coefficient of individual yield on environmental mean yield at each location. The clones used in this study had regression values ranging from 0·19 to 2·08, indicating considerable genotypic difference in response to environmental change. Genetic variation in adaptation was also found to be present. Clones of the Assam type were found to possess general adaptation whereas the one clone of Indo-Chinese origin was specifically adapted to low-yielding environments.

Some known features of several tea clones are explained on the basis of the linear regression model and a more scientific basis is provided for the recommendations of clones for differentdistricts. The implications of genotype-environment interactions in practical tea breeding and selection are also discussed.

Over the 4 years 1965–8, a total of 105 mature Friesian cows and 84 Friesian heifers were fed various levels of nutrition at two stages of the lactation to study the effect on milk production. The experiments were carried out over a whole lactation at four Experimental Husbandry Farms, Boxworth, Bridget's, Great House and Trawsgoed. There were three treatment levels in early lactation (weeks 3–10) comprising 5·9, 7·8 or 9·8 kg D.M./day of concentrates for mature cows and 1·6 kg D.M./day less at each level for the heifers. In mid-lactation (weeks 12–18) the two lower levels of concentrates were fed arranged factorially with early-lactation levels. A basal forage ration usually of hay was fed to provide 85% of the basal maintenance requirements. During the remainder of the lactation all animals received the same level of nutrition. In addition to the pre-determined feed treatments, one further group of animals in each block was fed according to the milk production in the preceding week.

Overall an increase in level of nutrition in early lactation produced a regular increase in milk production from successive increments with adult cows but only for the first increment with heifers. Raising feed level in mid-lactation increased milk production for all animals. There were considerable residual effects from early-lactation feeding but these were less with mid-lactation feeding. These same effects were also noted with yields of solids-not-fat and to a less extent in milk fat production.

The experimental results indicated not only the mean effects of treatments but more important the interaction with individual animals. Study of the response of individual animals indicated that the effects of level of feeding varied in proportion to the potential of the cow. The presentation of mean results can therefore be misleading. The potential of a cow was indicated by milk production in the immediate post-calving period. This period could be used both in experimental designs for selecting animals in the allocation to experimental treatments and also in the practical context for rationing individuals or groups of cattle.

The absolute plane of nutrition related to the potential of the animal was the most important factor in determining the efficiency of utilization of feed for milk production.

In a study with chicks, the metabolizable energy (ME) values of two maize and two wheat offal samples were estimated using regression procedures in which the ME of the fishmeal supplement, common to all diets, was first calculated.

From chemical analysis, the wheat offal samples would have been expected to yield at least as much ME as oats, but results fell short of expectation by as much as a quarter in the case of one sample of wheat middlings. The significance of these findings is discussed.

By comparison with previously determined ME values on the same samples fed to sheep, the chicken tended to metabolize more of the maize energy and less of the wheat offal energy.

The indices of susceptibility of five new varieties of maize: TZE 3 (3·01), TZE 4 (6·69), TZSR (5·58) developed at the International Institute of Tropical Agriculture, Ibadan, and MSRB-W (9·53) and MSC-opaque (5·0) at the National Cereals Research Institute, Ibadan, showed that the yellow variety, TZE 3, is the most resistant to post-harvest infestation by Sitophilus zeamais Motsch and Sitophilus oryzae (L.), the latterbeing the more abundant species.

Emerging F1 generation adults of either species of Sitophilusdeveloped longer, and were more numerous in soaked maize seeds without testa than in unsoaked, intactmaize seeds. Seed germinability declined as the number of holes per maize seed caused by adult insect emergence increased.

The wool-severing properties of 2·8% aqueous solution of calcium thioglycollate were increased by 76% by dissolving the depilatory agent in a KCl-NaOH buffer of pH 12·5. The optimum Ca-thioglycollate concentration for defleecing was 3·6%. One ml of this solution defleeced an area of 12·1 cma.

A comparison of five buffers and water as solvents for 3·6% Ca-thioglycollate indicated that the area of skin defleeced was directly related to solution pH and the stubble remaining appeared to be inversely related to solution pH. A KCl-NaOH buffer of pH 12·0 provided the optimum relationship between area defleeced (10·2 cm2/ml applied) and stubble (ca. 2 mm wool) remaining.

Single site applications of 0·1–1·0 ml of defleecing agent at skin level were compared and it was shown that the application of 0·1 ml aliquots would require 320 ml solution to defleece an average-sized sheep.

Preliminary evaluation of 6% formaldehyde buffered to pH 6 and a carbowax-citric acid solution of pH 2 showed that protection of fibres against dissolution by Cathioglycollate solutions can be sustained for 21 days. Pre-treatment with these compounds could therefore produce a protected band of wool immediately above the proposed site of wool dissolution.

The practical implications of these findings are discussed with regard to a wool harvesting programme.

The artificial fibre bag technique has been widely used in studies of forage dry-matter digestibility (Van Keuren & Heinemann, 1962) and of the release of a range of plant constituents during fermentation in the rumen (Playne, McLeod & Dekker, 1972). More recently, the technique has been promoted as a simple means of estimating the rate and extent of food protein degradability in the rumen (θrskov & Mehrez, 1977; Mathers, Horton & Miller, 1977).

Maize grain production in Nigeria is the collective effort of several growers individually cropping small areas. In these farms, maize stands are at suboptimal densities, soil fertility is low and crop loss from pests is high. Consequently, grain yields are characteristically low. By planting maize at closer spacing than the current standard, 90 x 25 cm, Fayemi (1963), Chinwuba (1967), and Okigbo (1972) were able to raise grain yield. However, the effect on pest population in Nigeria of increasing host plant density has received little research attention. Cromartie (1975) showed that host plant density and arrangement affect insect population dynamics. Other reports by Ficht (1932), Finch & Skinner (1976), Ralph (1977), Zepp & Keaster (1977), Adesiyun (1978) and Mayse (1978) indicate differential insect colonization, establishment and damage on host plants sown at different densities.

The determination of in vitro dry-matter digestibility (DMD) of grass and pasture legumes under both temperate and tropical conditions is well established (Tilley & Terry, 1963; Minson & McLeod, 1972). One application of the in vitro DMD estimation of pasture samples is, together with an estimate of faecal output, the measurement of the herbage dry-matter intake of grazing cattle. Pasture samples are usually collected with oesophageal fistulated cattle. This technique is well documented and has been reviewed by a number of authors (Langlands, 1975; Minson et al. 1976).

The forage potential of Andropogon gayanus (gamba grass) was assessed in cutting experiments on a low fertility, acid Ultisol in Colombia. This grass recently introduced from Africa outyielded Hyparrhenia rufa, Panicum maximum, Brachiaria decumbens and Digitaria decumbena in various mixtures made up of a single grass and a single legume. A. gayanua performed well as a companion grass with the legumes Styloaanthes guianensis, Stylosanthes capitata and Centroaema sp., while B. decumbena suppressed the legumes planted in these trials during the 2nd year following establishment.

Milk production of cows grazing Rhodes grass without the addition of grain supplements can be increased by feeding casein protected from deamination in the rumen with formaldehyde (Stobbs, Minson & McLeod 1977; Flores, Stobbs & Minson, 1979). No increase in milk production was achieved when unprotected casein was fed, indicating that production on a tropical grass was limited by the quantity of amino acids absorbed from the small intestines (Stobbs et al. 1977). Formaldehydetreated casein (formal-casein) increased by 5% the milk production of cows grazing ryegrass in New Zealand when an energy supplement was also fed but had no effect oh milk yield when only ryegrass was fed (Wilson, 1970). In a review of this subject Clark (1975) reported that pen studies showed post-ruminal supplementation with casein increased milk production from 1 to 4 kg/day. The result with ryegrass in the absence of an energy supplement is therefore unexpected and warrants further study.

Low quality roughages are a major feed resource for ruminants in Australia and many other parts of the world. Factors limiting the intake of these roughages include their high cell wall component and low crude protein content. Palatability may also be important. Low quality roughages are frequently dusty. Hence, the present experiment was initiated to determine whether water would affect the intake of paspalum hay (Paspalum dilatatum).

Differences in the partitioning of fat in the carcass may affect ‘carcass quality’ and depending upon the particular market requirements the optimum partitioning of fat may vary. Differences in fat partitioning may also affect the accuracy with which total carcass fat can be predicted from an assessment of subcutaneous fat (Pomeroy & Williams, 1974).

In the Sudan, rice has been grown since 1905, but on only a very limited acreage, and information about methods of production are lacking.

With the introduction of a large number of rice varieties into the country (Moir, 1965, 1966, 1967, 1968), an irrigation and drainage experiment was initiated by Hack (1968) at Kenana Research Station (KRS). Using the variety H.D.41, he found no advantage from very short watering intervals (1–3 days) in the early stage of growth, i.e. up to the boot stage, whereas better results were obtained from watering every 6 days in the early stage, to obtain a large number of flowers, and every other day in the late stage, to obtain relatively low sterility and large grains.

It is now possible to synchronize the cycle of ewes at all times of the year (Gordon, 1975). Conception rates approaching those obtained following natural service have been reported following double (Colas & Brice, 1970; Colas et al. 1973; Barlow, Pryce-Jones & Reed, 1974; Gordon, 1975) or single (Smith, Boland & Gordon, 1978) set-time inseminations. In France, synchronization of ewes' oestrous cycle is based on the use of a Cronolone pessary (Colas, 1975), while field trials conducted in Britain have used the 60 mg Medroxy progesterone acetate (MAP) sponge (Barlow et al. 1974). Robinson et al. (1967) in an evaluation of different progestagen treatments found MAP to be less predictable than Cronolone. The purpose of the present experiment therefore was to evaluate the use of a 30 mg Cronolone or a 60 mg MAP intravaginal treatment when used in conjunction with fixed-time inseminations. In addition, two dose levels of pregnant mare serum gonadotrophin (PMSG) were compared.