The results of 84 experiments with six levels of nitrogen were used to investigateresponse curves relating the dry-matter yield of grass herbage to fertilizer nitrogen. Of the five curves tested, the inverse quadratic represented the relationship well, although no one curve fitted best on all experiments.

Forty-four turkeys including both sexes of two genetic strains were drawn at mean weight-for-age at 2 week intervals from a flock of 380 birds from hatching to 20 weeks post-hatching. Birds were dissected and linear measurements of skeletal units and breast dimensions were compared with keel length using the logarithmic form of Huxley's allometric growth equation. Live weights and weights of selected muscles were similarly compared with breast muscle weight. Wing bones and the biceps brachii muscle grew at approximately the same rate as keel length and breast muscle, respectively. However, leg bones and semitendinosus and gastrocnemius muscles exhibited slower growth than the breast region. Growth of maximum breast length and width was closely matched to keel length but growth in keel depth was much slower. The desirable convexity in breast shape lateral to the keel was considered to be directly proportional to maximum meat depth over the sternum and inversely proportional to keel depth. Maximum meat depth increased at a faster rate than either keel length or depth.

The rate of development of resistance to Du-Ter in Spodoptera littoralis (Boisd.) has been determined. The results show that true resistance to Du-Ter could not be induced throughout 33 successive generations. Also, it was found that the rate of development of resistance to DDT in the DDT + Du-Ter strain after being selected with DDT + Du-Ter pressure for 17 successive generations was 11·5- and 43-fold that in the DDT strain. It is concluded that the application of DDT and Du-Ter mixture, having dissimilar modes of action, considerably controls the development of resistance to DDT.

Photosynthetic rates, chlorophyll content and activity of ribulose 1,5-diphosphate carboxylase (RuDPC) were determined for 18 genotypes of wheat (Triticum aestivum L.) in pot culture. Measurements were made at various growth stages. Correlation studies between physiological characteristics and seed yield were made at each stage separately.

Genotypic variations were observed at different growth and developmental stages in photosynthetic rates (1·8–2·7-fold), chlorophyll contents (1·2-fold) and enzyme activities (2-fold). Chlorophyll content and enzymic activity increased in plant leaves with advancing age while apparent rates of photosynthesis decreased.

RuDPC activity in flag leaf at anthesis showed significant positive correlation with grain yield (r = 0·55). Other attributes did not show significant association with grain yield.

An attempt has been made to produce barley lines in accordance with an ideotype designed in 1968. Current lines are early maturing, uniculm, six-row barleys, of medium height, high harvest index, and moderate resistance to lodging. However, they have lax leaves of medium length, in contrast to the short, erect leaves of the ideotype. When sown in narrow rows at a rate three times that of tillered lines, they have given grain yields greater than the two- and six-row tillered controls, especially in favourable seasons, but less so in dry years. The quality of the grain has not been examined. In the absence of plasticity in number of tillers, uniculm lines show increased plasticity in number of grains per ear and weight per grain. It is possible that the uniculm habit, apart from effects on morphology and maturity, may permit more exacting selection of high-yielding plants than is possible among plants each comprising many mutually competing culms.

The jaws of 481 adult culled ewes were examined visually and radiographically for dental abnormality and changes in skeletal structure; the findings were correlated with ante-mortem body condition score and breed. Only two ewes had normal buccal morphology; the remainder of the sample showed a range of abnormalities which included loose and missing teeth, gingival hypertrophy, food-filled gingival pockets, ridging and shearing of the occlusal surfaces. There was a general loss of bone structure. Dental abnormality was not strongly correlated with breed but showed a significant relationship with radiographic assessment of bone density. Body condition did not appear to be adversely affected by dental disease. Skull dimensions and dental pad position were strongly associated with breed. The state of the incisor teeth alone was a poor indicator of cheek tooth condition.

The yield and quality of herbage produced by six grasses (perennial ryegrass, cocksfoot, timothy, rough-stalked meadow grass, tall fescue and Italian ryegrass) were examined both without irrigation and under two irrigation regimes. Water was applied according to the potential soil water deficit (potential SWD): the soil was either partially returned to field capacity (FC) after each cut or fully returned to FC whenever the potential SWD reached 25 mm. The swards were cut either at 3 (C3) or 6 (C6) week intervals over a 2 year period.

Partial irrigation increased yields by 12–14% in the first year and by 36–58% in the second. Full irrigation produced little more growth than partial irrigation in the first year (maximum SWD, 188 mm) but increased yield by 78–93% in the second, very dry, year (maximum SWD, 311 mm). Under treatment C3 response per unit of water applied was similar with both partial and full irrigation, but under C6 the response was greater with partial (2·86 kg D.M./m3) than with full irrigation (1·79 kg D.M./m3).

There were marked differences between the species in their ability to grow under drought conditions in the second year of the experiment. Without irrigation, roughstalked meadow grass and Italian ryegrass did not survive the drought. The performance of tall fescue was markedly superior to both perennial ryegrass and cocksfoot in these conditions. Of the surviving grasses timothy made least growth.

The carcasses of 20 Landrace, 20 Hampshire and 20 Duroc Jersey barrows were dissected in order to study the influence of the breed on tissue weight distribution.

After weaning, at 56 days of age, the animals were allocated to individual pens and fed a standard diet containing 18% crude protein and 13 MJ ME/kg, until they reached their designated slaughter weight.

The Landrace and Hampshire pigs were slaughtered between 60 and 115 kg and the Duroc Jersey ones between 40 and 115 kg live weight. The right half carcasses were completely dissected using strictly anatomical criteria. Individual muscles were classified into eight anatomical groups (Carden & Goenaga, 1977).

The results were examined by covariance analyses utilizing the allometric equation. Carcass tissue composition was studied using the weight of the dissected side as covariate. When muscle: bone ratio was examined, the weight of total side muscle was used as the independent variable. The growth of different parts of a tissue relative to the corresponding whole tissue was studied.

Concerning carcass composition, there were significant breed differences in muscle and fat contents and in the muscle:bone ratio.

Breed differences were found in muscle distribution. The 6 values of muscle groups 1 (proximal hind limb), 2 (distal hind limb), 6 (distal forelimb) and 7 (muscles connecting forelimb to thorax) were statistically different as were the adjusted means of groups 3 (spinal column), 5 (proximal forelimb) and 8 (muscles connecting forelimb to neck and intrinsic muscles of neck and thorax).

Significant differences were also found in bone weight distribution. Slope values of the tarsals, os coxae, scapula and sternum were statistically different. Adjusted means of tibia-fibula, sacrum, spinal column, radius-ulna, carpals and ribs were also significantly different.

Finally, there were breed effects in the distribution of fat, the relative weight of subcutaneous and of intermuscular fat being statistically different.

A study of the birthcoat and its relation to kemp succession in the adult fleece of coarse-wool Awassi and Hamdani sheep was carried out, as an aid to early selection. Lambs were covered, at the age of 2 months up to 15 months, by fixing patches of canvas on six body positions.

Both Awassi and Hamdani birthcoats had high halo hair grades. The animals played the dominant role in affecting different traits of the birthcoat which indicated the importance of genetic factors in further development of the birthcoat. The birthcoat of both types of lambs showed only coarse (plateau) and less coarse (saddle) fibre type arrays.

Hamdani had more kemp as Gt and G2 (first and second generations respectively) than Awassi sheep. The shed Gx following the different fibre type arrays, showed some overlapping between plateau and saddle. The same arrays of the birthcoat behaved differently on the different positions, where generally the anterior positions had less kemp than those posteriorly. Percentages of shed fibres were 100, 17·14, 2·38 and 0·35 of halo hairs, super sickles, sickles and chalky curly tips respectively in Awassi. Corresponding figures were 100, 29·26, 5·87 and 7·73 in Hamdani. In Awassi, halo hairs, of the birthcoat, showed a relatively high correlation (P < 0·01) with G1 kemp on the hip and britch. Within saddle array, in Awassi, the correlation between halo hairs and Gx kemp showed the highest values (P < 0·01), whereas in Hamdani the correlation between super sickles in the birthcoat and G2 kemp showed medium values (P < 0·05).

Selection of high halo hair grade lambs, in the birthcoat, that have saddle arrays, with high percentage of sickle fibres in Awassi and with low percentage of super sickles in Hamdani, would result in low percentages of kemp in the adult fleece. High halo hair grades would be necessary for early survival of lambs.

The use of soil water by six grasses (perennial ryegrass, cocksfoot, timothy, rough stalked meadow grass (RSMG), tall fescue and Italian ryegrass) was measured over 2 years. The swards were cut either at 3-week (C3) or 6-week (C6) intervals. In both years the maximum soil water deficit attained under C6 was greater than under C3. Following several of the cuts from C6 there was a marked, although temporary, reduction in the rate of water uptake.

An extended dry period in the second harvest year revealed substantial differences in the total water used and in the patterns of uptake from the soil profile by the grasses. Effective depths of utilization of water under treatment C6 were: RSMG, 40 cm; timothy, 70 cm; cocksfoot, 70 cm; perennial ryegrass, 80 cm; tall fescue > 100 cm. This order of depth of utilization corresponded with the order of yields obtained during drought conditions. An examination of the root systems of four grasses also showed that, particularly under treatment C6, roots of tall fescue were more numerous at depth than those of timothy, cocksfoot or perennial ryegrass, and under this treatment it showed its greatest tolerance to dry conditions. Drought tolerance in these grasses appears largely determined by the volume of soil exploited by the roots for water.

Seed treatments and methods of sowing sugar beet were tested in the laboratory and in field trials in 1975, 1976 and 1977 on a range of soil types including a sand, several loams and a peat.

‘Advancing’ the seed by controlled imbibition of water followed by drying before sowing, gave 2–3 % more emergence. Seedlings appeared 3–4 days earlier and were up to 50 % heavier at the four to six leaf stage, but by final harvest yields of sugar per unit area were similar from advanced and untreated seed. ‘Priming’ in osmotic solutions of salts or polyethylene glycol, to bring all seeds to the point of germination, before drying back and sowing gave inconsistent effects in the field with emergence percentage frequently being below that of the control. Steeping seed in water, aimed at removing germination inhibitors, improved germination and reduced the time to, and duration of, germination when tested in the laboratory but gave poorer results than the untreated control in the field. ‘Chitting’ the seed in the laboratory greatly improved emergence characteristics but treatment effects in the field were very variable. Chitted seeds were sown in carrier gels in the field to try to protect the radicles from damage but seedling establishment was no better from fluid drilling than from normal dry seed sown ‘raw’ or pelleted in clay, even when only chitted seeds were put into the fluid. Possible reasons for this are discussed.

Fluid-drilled seeds consistently gave quicker emergence and larger seedlings. Even when these were 30–50 % heavier, differences had usually become negligible by the end of the average 230 days long growing season, so that sugar yields were not consistently affected by the treatments tested.

The phosphorus status of five Nigerian coastal plain sands was evaluated by determining the relative abundance of the various P forms and the P adsorption capacities of the soils. Total P ranged from 4460 to 1129 mg/kg. Organic P had a range of 23–232 mg/kg and formed below 30% of total P in four of the profiles but above 50% in the hydromorphic Otegbo profile. The relative distribution of the various inorganic forms was in the increasing order of residual P, active P and occluded P, except in the Onne profile in which the residual P was relatively the least abundant. The relative distribution of the active P forms was in the decreasing order of Fe-P, Al-P and Ca-P.

The adsorption capacity varied widely among the soils. The amount adsorbed from the addition of 150 mg/100 g of soil ranged from 40–2 to 86–2 mg/100 g and was related to the clay content. The adsorption at 0–3 mg/1 P in equilibrium solution ranged from 19 to 265 mg/kg. The subsoils generally adsorbed more P than the surface soils. The P requirements of the soils estimated from the sorption capacities were in the low and medium ranges.

The pattern of leaf growth and death was followed in stands of cowpea grown in the field at Ibadan, Nigeria. Temperature affected this pattern. Leaf area index increased quicker and leaf death started sooner during warm seasons. Individual leaves died while pods at the same node were filling. The rate of leaf appearance increased with temperature and the duration of expansion of individual leaves decreased so that a constant number of leaves were expanding at one time. The mean rate of expansion of individual leaves increased with temperature proportionately more than the duration decreased, hence final leaf size increased with temperature. Base temperatures for leaf appearance and leaf expansion were 16 and 20 °C respectively.

Male and female (Suffolk × (Finnish Landraee × Dorset Horn)) lambs were used in three experiments to examine the replacement of milk by undried and dried fish protein hydrolysates (FPH), a mixture of lard and coconut fat, and partially hydrolysed starch (Protamyl 110). The animals received the experimental diets from 1 week of age in Expts 1 and 2, and from 4 weeks of age in Expt 3. They were given the diets in eight equal feeds (i.e. every 3 h) from an automated teat bar system. The level of feeding was 1·046 MJ/kg0−76/day. Experiments 1 and 2 lasted for 35 days, during which live-weight gain and food conversion ratios were recorded and at the end the digestibility of N, dry matter and starch was determined. Experiment 3 consisted of three small digestibility trials.

In Expt 1, the replacement of milk protein with undried FPH and of milk fat with lard plus coconut fat had no significant effects on live-weight gain, food conversion ratio or nutrient digestibility. Somewhat lower gains for the lambs given the FPH than those given milk protein were observed during the first 15 days of the experiment. Apparent digestibility of milk protein and milk fat was 95 and 99% while that of PFH and lard plus coconut fat was 94 and 96% respectively. The replacement of milk fat with lard and coconut fat caused some reduction in live-weight gains and nutrient digestibility. Lactose was completely replaced by protamyl both in diets based on milk protein or FPH with no effect on live-weight gains or food conversion ratio.

Apparent digestibility of fish protein was not affected by the drying process. Fat digestibility of diets containing undried or dried FPH ranged from 46 to 98% according to the type of emulsifier used. The results are discussed in relation to published data concerning the problems associated with the use of fish protein in milk replacers.

Information on the total dry-matter intake (TDMI), concentrates supplied (C), live weight (LW), week of lactation (WL), milk yield (MY) and composition, quality of forage fed to, and parities of, 385 cows from five different sources were assembled to develop appetite prediction equations. The equations were based on multiple regression and least squares constants and were calculated using the data from each source and the data pooled from all sources. The major factors affecting total dry-matter intake (TDMI) were C, LW, WL and MY and for the pooled data these factors explained 73–76% (R2) of the total variation in TDMI. The predictive values of some of the equations were tested against independent sets of data and for groups of cows and individual cows, the equations predicted TDMI within ±1·1 and 1·6 kg, respectively. The application of the equations in the field is discussed and some suggestions made for increasing the R2 of future appetite equations.

An analysis has been made of the reproductive performance of Red Sokoto goat of Nigeria. Data are based on records of 140 kiddings from 96 does. Age at first kidding was 435 ± 18·9 days. The mean litter size at first kidding was 1·45. Prolificacy increased with parity, the kidding percentages from first to third parities being 141, 186 and 200 respectively. Doe weight was significantly correlated with litter size (r = – 0·27). Repeatabilities of litter size per doe kidding and of litter weight were negative. Heritability of litter size was 0·08 ± 0·02. Birth weights were low, the mean weight of kids during the 3 years ranging from 1·48 to 1·64 kg. Doe weight was related to litter weight in a manner such that litter weight as a proportion of doe weight tended to decline as doe weight increased. The ratio of litter weights of singles to twins at any given weight of the doe was 100:180. Kid mortality by 3 months of age was 30·8 %. Mortality among twins was only slightly higher than singles. However, mortality in kids born in multiple births (triplets and quadruplets) was much higher. Birth weights of surviving kids were significantly higher than of those that died.

Nine strains of Rhizobium sp. were studied in vivo for their nodulation capacity, leghaemoglobin content, grain yield, crude protein and 16 amino acids content, in the chick pea variety C 235 grown on a calcareous saline alkali soil. There was no significant correlation between grain yield and number of nodules (r = 0·37) or dry weight of nodules (r = 0·29), but grain yield was significantly correlated with leghaemoglobin content of nodules (r = 0·95). Of the 16 amino acids analysed in seed samples, aspartic, glutamic, proline and histidine were greatest with strain H 45; glycine, leucine and arginine with strain F 6; norleucine, tyrosine and phenylalanine with strain KG 38; and alanine and valine were greatest with strain KG 41. Strain KG 38 led to significantly higher grain yield than the other strains.

The pattern of dry weight accumulation and partition of cowpea crops grown in Nigeria is described. For the first 50 days, increase in dry matter was proportional to intercepted radiation. Differences in dry weight between crops were due equally to variations in incident solar radiation, the fraction of this radiation intercepted, and the efficiency with which it was used. The variation in total pod weight from 206 to 312 g/ma resulted from differences in number of pods, mean pod weight being constant. The pod weight ratio was relatively constant and there was a strong relationship between final number of pods and total plant dry weight.

Twenty-seven British Friesian heifer calves were housed as a group but fed individually barley-lucerne pellets according to a scale related to body weight. At 16 weeks and again at 31 weeks of age nine calves were implanted subcutaneously at the base of the ear with 300 mg trenbolone acetate (group T), nine calves were similarly implanted with 140 mg trenbolone acetate and 20 mg oestradiol-17/? (group TE) and the remaining nine calves were sham implanted (group C).

As a result of increased feed conversion ratios, body-weight gains were significantly greater in group T (0–80 kg/day) and group TE (0–87 kg/day) than in group C (0–72 kg/ day) during the 15 weeks following the second implant, but there was no significant difference between groups following the first implant.

Following both implants in groups T and TE the mean concentrations of urea and albumin in serum decreased, and that of globulin increased. The mean urea: creatinine ratio in the urine of animals in groups T and TE relative to that in group C also decreased.

The heifers were served by an Aberdeen Angus bull at the first and, when they occurred, subsequent oestruses. Following calving the mean milk yields in the first lactation in group T (641 kg in 96 days) and group TE (1993 in 212 days) was considerably lower than in group C (3636 kg in 293 days). The udder size in both groups of animals treated with the anabolic steroids was markedly reduced. It is concluded that despite an improvement in feed conversion ratios and body-weight gains, trenbolone acetate should not be administered to prepuberal heifers which will be retained for breeding and milk production.

Between 1972 and 1976 a series of 15 trials was carried out at various climatically favoured sites throughout Scotland to assess the potential of new hybrid maize varieties of European origin under Scottish conditions. No meaningful differences were found between varieties in respect of dry-matter yield or maturity.

Seed rates ranged from 100 to 200 × 103 seeds/ha giving final stands from 40 to 194 × 103 plants/ha. Regression analyses for the variety Dekalb 202 included in 54 treatments indicated that the relationship between plant population density and dry-matter yield was partly linear with an important quadratic function, suggesting an optimum of 179 × 103 (± 80 × 103) plants/ha. Plant population density accounted for 65·9% (P < 0·01) of the variance in dry-matter yield but was not significantly related to dry-matter content.

Climatic variation between years had no overriding influence on growth and development. Dry-matter production for the variety Dekalb 202 sown in mid-May ranged from 2·86 (1972) to 14·54 t/ha (1975) with associated dry-matter contents of 15·1 and 24·1% respectively. In a few instances slightly higher dry-matter contents (maximum 28·6%) from mid-May sowings were associated with lower yields.

Neither date of sowing nor accumulated temperature to harvest measured as Ontario Heat Units was significantly related to yield but date of sowing accounted for 29·5% (P < 0·01) of the variance in dry-matter content. Accumulated Ontario Units at harvest were not significantly related to dry-matter content.

An interesting relationship between dry-matter yield and the date on which the crop had received 1379 Ontario Units was found. This relationship may be useful in selecting sites at which maize may be grown or to predict maximum potential final yield in any given season.