Data representing 1928 lambing records were analysed to study the effects of inbreeding and cross-breeding on lamb survival to the ages of 7, 30, 120 and 180 days. The sheep flock consisted of two native breeds, Barki (B) and Rahmani (R); and the imported Fleisch Merino (M) as well as the crosses M × B and M × MB. Analysis was made by fitting a least-squares linear model that included the main effects of year and season of birth, sex, age of dam, type of birth, inbreeding of the lamb (Fd) and the dam (Fd) and breed group and the interactions season × type of birth, season × Fo and season × breed group. Lambs were classified into six groups according to the magnitude of the inbreeding coefficient: F ≤ 0·05, 0·05 < F ≤S 0·10, 0·10 < F ≤ 0·15, 0·15 < F ≤ 0·20, 0·20 < F ≤ 0·25 and F > 0·25. The average inbreeding coefficient in the flock was 0·12 and 0·08 For the lambs and their dams, respectively.

Sex of lamb and age of dam had no significant effect on lamb survival at any age while single-born lambs had a higher (P < 0·01 or P < 0·05) survival than twins at all ages except 7 days. Inbreeding of the lambs showed significant effect at 7 and 120 days. Increase in inbreeding of the dams was associated with higher mortality at all ages but the trend was not significant.

Differences among breed groups were not significant at 7 and 30 days, but were highly significant at later ages. The contribution of breed group to the total variance in survival increased with age. Hybrid vigour was highly significant in both crosses at 120 and 180 days.

A study was conducted at two different sites in the Egyptian western desert to investigate the activity of carnivorous birds on some invertebrates. At the first site (sand-dunes in the Gharbaniat area, 52 km west of Alexandria), the most interesting bird found was the great grey shrike Lanius excubitor which seizes its prey and impales it upon spines of Lycium europaeum or on barbed-wire fencing. Studies carried out from January to July 1977 indicated that this bird prefers to feed on certain tenebrionid or scarabaeid beetles as well as some orthopterous insects and small lizards of the area. At the other site (inland depression near Omaycd, 80 km west of Alexandria, and 12 km from the sea) a snail-eating bird, (bifaciated lark) Alaemon alaudipes, was found to be the commonest bird where the non-saline soil of the site is suitable for the desert snail, Eremina desertorum, to breed, so much so that the snails constitute one of the prominent features of the site.

The latter bird is more active in the winter than in the summer. From February to the end of June 1979, the estimated snail flesh weight eaten by A. alaudipes birds was about 6·50 kg taken from an area of 2·4 ha. The birds seize a snail, fly upwards to a distance of 6–23 m, select a hard stone, then drop the snail. The snail eventually breaks, and the flesh exposed is readily eaten by the bird. In January 1980, a survey was conducted to investigate the species of birds found in the area that extends between Alexandria and el Alamein. Twenty-six resident, as well as migratory, bird species were observed. The number of species and individual birds in cultivated areas, and sites near the sea shore, were found to be greater than those in natural ecosystems at a distance from the sea.

Three successive sowings of marrow-stemmed kale (cv. Maris Kestrel) were grazed with lambs (initial weight 22·5 kg) for two consecutive 6-week periods, so that crop yield at the time of grazing was kept relatively constant at 6·5 t D.M./ha. Three crop allowances, 3·9 (H), 2·6 (M) and 1·3 (L) kg D.M./animal/day were imposed in a replicated design. Halfof the 32 lambs grazing each allowance received intraperitoneal injections of L-methionine + L-threonine three times per week. Twelve lambs were slaughtered at the start of the experiment and 48 at the end of each period.

Leaf tissue, the diet of the H groups, contained 0·5% D.M. as S-methylcysteine sulphoxide (SMCO) and 0·7–1·5% total N as nitrate. Whole plants, the diet of the L groups, contained 0·75% D.M. as SMCO and 4·0–7·5% total N asnitrate. The diet of the M groups was intermediate.

Rates of live-weight gain (LWG), empty-body weight gain (EBWG) and carcassweight gain (CWG) were lower in period 1 than in period 2 for animals grazing at all three allowances. A Heinz-Ehrlich body anaemia developed that was more severe in the first period, but did not differ between groups receiving the different allowances. Methaemoglobin was only detected in significant quantities at the time of peak Heinz body formation in period 1. CWG/EBWG was increased by the amino acid supplementation during period 1 but not period 2, showing that there was a temporary amino acid deficiency corresponding to the time when tho anaemia was most severe and body growth most depressed.

In both periods animals grazing at L allowance had lower rates of LWG, EBWG and CWG than M and H animals, who performed similarly. Most of the differences in EBWG between feed allowance treatments and between periods could be explained by changes in estimated intake. Wool growth rates increased with increasing feed allowance and were slightly stimulated by amino acid supplementation.

Copper true availability was calculated to be 1·6–2·7% with the lowest values for leaf tissue due to its high sulphur content. Truly available Cu/kg plant D.M. was below the minimum requirement for lamb growth, thus leading to a reduction in total liver Cu as the experiment progressed. Some indication was obtained that this could have been depressing LWG in the second period, especially in H lambs. Slight increases in thyroid gland weight were observed as the experiment progressed, but these were considered unlikely to have depressed body growth. It was concluded that the major factor limiting the feeding value of B. oleracea was its high content of nonprotein sulphur compounds, especially SMCO.

The variability generated in a diallel cross between seven genotypes for vegetative and phenological characters was studied in the F1 and F2 generations in lowland Papua New Guinea. The mean narrow-sense heritability values of mean leaf size and leaf area index at flowering were 88·0 and 78·5%. The parental values of these characters gave good predictability of the performance of the parents in hybrid combination. For mean number of leaves per plant at flowering, environmental effects were of major importance, and consequently selection between crosses for number of leaves is considered futile. There was a large genotype ˣ environment interaction for time to first flower. The role of various environmental factors in causing the interaction for flowering is discussed.

The loss of potassium through the cutaneous route was measured in three Chokla rams by balance trial and by washing the animals (ambient temperature 28–33 °C, 28–30 mmHg vapour pressure). The excretion of potassium through urine and faeces was 46·7 and 19·4% of the intake, respectively. The excretion through skin recorded by washing the animals was 29·1% against 33·7% potassium available for excretion through the thermoregulatory route. About 2·56 g potassium was thus excreted through the cutaneous route per day. There was a net retention of 9·8 g sodium/ram/day.

Animals fed sole diets of kale (Brassica oleracea) were compared with animals fed ryegrass-clover pasture grown on the same soil type in two experiments. In Expt 1 young cattle grazed the two forages for 24 weeks, with supplementary copper and iodine being administered by injection. In Expt 2 young sheep were individually fed the two forages indoors at equal D.m. intake.

Animals grazing kale in Expt 1 showed the characteristic symptoms of haemolytio anaemia from ruminal fermentation of S-methyl cysteine sulphoxide (SMCO) (Smith, 1974). This was most severe over the first 6 weeks, during which live-weight gains were very low (250 g/day). In the absence of copper supplementation animals grazing kale showed symptoms of copper deficiency. This was characterized by live-weight gain remaining low throughout the experiment (mean 280 g/day), rapid depletion of liver copper reserves, progressive reductions in serum copper concentration, reductions in erythrocyte copper and reduced glutathione (GSH) concentrations and a massive hepatic accumulation of iron. Copper deficiency only slightly lowered heart muscle copper concentration in kale-fed cattle, and this was counteracted byheart hypertrophy. The major effects of copper deficiency in kale-fed cattle were in erythrocytes, and a metabolic diagram is presented showing these effects to be biochemically similar to those produced by ruminal fermentation of SMCO.

Copper supplementation of animals grazing kale increased live-weight gain (mean 425 g/day), reduced Heinz body formation, allowed the animals to recover gradually from the haemolytic anaemia and prevented other symptoms of copper deficiency. In contrast, animals grazing ryegrass-clover pasture showed only a very mild depletion of copper, there being no response in live-weight gain to copper supplementation.

Activity of the enzyme glutathione peroxidase (GSH-Px) in whole blood was dependent upon blood selenium concentration in cattle fed both diets. In cattle fed on kale, bub not on pasture, reductions in erythrocyte GSH due to ruminal fermentation of SMCO and to copper deficiency were also associated with depressed blood selenium status.

Glucosinolates were present in the kale (11μM/g D.M.) but absent from the pasture diet. Despite this, neither T4 production from the thyroid gland nor the conversion of T4 to T3 appeared to be impaired by kale feeding in either Expt 1 or Expt 2. In Expt 1 serum T3 concentration was better relatedto live-weight gain than was serum T4 concentration, in accord with T3 being the active form of the thyroid hormone.

It is concluded that supplementation with copper but not iodine is essential where growing cattle are fed sole diets of kale for periods in excess of 12 weeks

Five Zn-deficient soils designated A–E (pH 7·3–7·7) and a reference soil F (pH 7·6) were used in a glasshouse study on maize in which five fertilizer treatments: 75 μg P/g alone and together with all combinations of 0 and 5 μg/g of Mg and Zn and with 10 μg Mg + 5 μg Zn/g and a control were applied. The forage yield of soils A–E ranged from 2·5 to 2·9 g when no Zn was applied and from 5·1 to 5·6 g with added Zn, showing that Zn was the major limiting nutrient. Applied Mg significantly increased yield, the main exceptions being soils D and E which had the highest exchangeable Mg.

Addition of Mg to a P but not PZn treatment significantly increased P concentration and uptake. For soils B and E, Zn addition significantly depressed P concentration in maize. The P treatment significantly depressed Zn concentration but increased Mg concentration and uptake by maize. Although Mg application either depressed or had no effect on Mg content of maize, it caused a significant increase in Zn concentration and uptake. The correlation coefficient (r) between Zn and Mg in maize was – 0·61 (P < 0·001). Possibly, Mg was replacing Zn in the clay lattice or in its metallo-protein complex within the root.

Two indigenous breeds of sheep in Nigeria, the Yankasa and Uda and crosses of these with exotic breeds, were evaluated for lamb weights at birth, 3 months and 6 months of age and for adult ewe weight. The cross-bred lambs were significantly (P < 0·05) heavier than the indigenous breeds at all ages. Differences among the indigenous breeds were not significant. Mature ewe weight was 40·8 kg in the cross-bred and 36·0 and 31·1 kg in the Uda and Yankasa respectively, differences between all breeds being significant (P <0·05). Lamb productivity (lamb weight per kg of ewe metabolic body weight) estimates demonstrated that the differences between breeds were small.

Least-squares estimates of effects of environmental factors on lamb performance showed that type of birth and age of dam were important for lamb weights at the three ages. Season and sex also had significant effects on birth and 6-month weights respectively. Correction factors for lamb weights were derived from least-squares estimates.

The correlation coefficient between birth and 3-month weight was significant in all breeds and ranged from 0·39 to 0·55. Three-month and 6-month weights were highly correlated with estimates of correlation coefficients ranging from 0·71 to 0·74. Repeatability estimates of birth, 3·month, 6·month and ewe weights, all as traits of the ewe in the Yankasa, were 0·25, 0·21, 0·09 and 0·48, respectively.

In Expt 1 40 lactating British Friesians, 20 cows and 20 heifers, were used to study the effect of crude protein (CP) content of the whole ration on milk yield, milk composition and live-weight change when maize silage was fed as the basal ration. There were four treatments with five cows and five heifers on each. During lactation weeks 4–12 the cows on treatments 1, 2, 3 and 4 all received 7 kg maize silage dry matter (D.m.) plus 8 kg D.m./day of a concentrate containing either 14, 18, 22 or 24% CP, respectively; heifers received 1 kg/day less of both silage and concentrate. This produced whole-ration CP contents of 11·7, 13·9, 16.·0 and 17·1%. In the subsequent lactation weeks 13–20 silage feeding was increased to 9 kg D.m./cow/day and concentrate feeding decreased to 5 kg D.m./cow/day. Heifers again received 1 kg/day less of both silage and concentrate. This decreased whole-ration CP contents to 10·5, 11·7, 12·9 and 13·4%.

During lactation weeks 4–12 and 13–20, with the exception of milk fat content in weeks 13–20, there were significant linear effects of whole-ration CP content on milk yield, milk fat, protein, lactose and total solids. There were no significant curvilinear relationships. Thus, despite the fact that the highest numerical values were generally recorded for the animals on treatment 3, the results indicate that a whole-ration CP content of at least 17·1 and 13·4% are required in early and mid-lactation respectively.

In Expt 2 the loss of D.m., acid-detergent fibre and nitrogen from maize silage suspended in nylon bags in the rumen was measured. Compared with feeding either a low or high protein supplement, losses were greater for silage fed alone. If it is accepted that nitrogen loss can be approximated to protein degradability, then the value for maize silage was between 0·6 and 0·7. Using the same technique in Expt 3, comparable nitrogen losses for fish meal, decorticated groundnut meal and soya-bean meal were 0·3, 0·9 and 0·9, respectively, after 24 h incubation.

The relationship between calcium and phosphorus metabolism in wether sheep given high or low Ca diets, with or without 1α-hydroxycholecalciferol (1α-0H-D3) has been studied by a mineral balance and radioactive technique.

Ca absorption was not related to Ca intake but was stimulated by 1α-OH-D3. More Ca was absorbed by treated animals from the high Ca diet than from the low diet and all the extra Ca absorbed was retained, increased retention being brought about largely by an increase in the rate of bone accretion.

P absorption was increased to approximately the same extent from both diets suggesting that stimulation was due to the 1 α-0H-D3 treatment rather than increased Ca absorption. Whereas the extra P absorbed from the high Ca diet was retained, together with Ca, in bone and soft tissues, that absorbed from the low Ca diet was largely excreted in the urine. It is suggested that this difference in P retention reflects a difference in availability of Ca for retention in bone and P retention was in fact found to be directly related to Ca retention.

The roles of secretion of P into the gut, absorption of P from the gut and urinary excretion of P are discussed in relation to P homoeostasis.

As absorption of P from the intestine and loss of P to bone, soft tissues and urine increased, so endogenous faecal loss decreased until it reached a value of approximately 35 mg/day per kg body weight when it remained constant. It is suggested that this value may represent the inevitable loss of endogenous P in the faeces from a hay and concentrates diet and that this minimum value may have a bearing on the calculation of P requirements.

The aim of this investigation was to grow barley as a fodder crop under highly saline conditions. Saline irrigation waters with an electrical conductivity (EC) of 2·5, 4·0, 6·0 and 8·0 mmhos/cm respectively were used to irrigate test crops of barley over two growing seasons.

It was concluded that in general more highly saline water leads to a considerable increase in soil salinity even over a short period of growth, and a close control of soil salinity through leaching is required. Saline water with an EC of 4·0 mmhos/cm may be utilized without excessively high yield reductions if the soil salinity is well maintained. The saline waters with an EC of 6·0 mmhos/cm and 8·0 mmhos/cm may lead to yield reduction, and they require careful managmeent to control soil salinity build-up.

Hofuf-Alhassa is one of the important agricultural areas of the Kingdom of Saudi Arabia. The water available for irrigation purposes is limited in quantity and saline in nature.

To maximize the use of available water sources, a technique is described to mix irrigation water with drainage water, taking into consideration the salt balance effect in the soil under the Alhassa conditions.

Since 1966 a closed line of Hereford × Shorthorn cattle (selected line) has been selected principally for growth rate under conditions of moderate to high environmental stress. Responses in growth rate were measured over the years 1970–5 as differences from an unselected control line. Birth weight declined but live weight at all other ages increased.

Groups of animals were taken from each line in 1976 and 1977 and used to determine the reasons for the differences in growth rate. Growth rate of the groups was measured when they were exposed to several different levels of stress, namely, the plane of nutrition, high ambient temperature, infection with bovine infectious keratoconjunctivitis(BIK) or gastro-intestinal helminths. The selected line was shown to be more heat tolerant, to have lower maintenance requirements and greater resistance to infection with BIK and helminths and, in consequence, always had higher growth rates in the presence of these stresses. However, they did not have superior growth rate at low levels of these stresses. Thus, selection had not increased the components associated with growth potential, and the improvement in growth rate was achieved entirely through increases in resistance to environmental stresses which affected growth rate.

The application of these findings to selection for growth rate, particularly in harsh environments, is discussed.

A number of early generation inbred families and lines, as far as the S5, have been produced by self-pollination in Lolium perenne L. variety S. 23. The pedigree structure is given for 13 parent plants used in the breeding programme to show the patterns of segregation for self-fertility genes and to give the ancestry of eleven S5 inbred lines. Data on numbers of seed set, flowering time and inflorescence production reveal a wide range of variation due to both environmental and genetic components.

Results are reported from four separate trials carried out to determine the precision of the Sonatest (simple A-mode ultrasonic machine) and the Scanogram (modified linear scanner) for predicting the body composition of live cattle. Cattle in the four trials differed in breed, sex and origin, and the data provided an opportunity to determine the consistency of results in different circumstances. A total of 210 cattle were involved.

Fat thickness measurements (Sonatest and Scanogram) and fat and M. longissimus areas (Scanogram only) were taken at the 10th and 13th ribs and at the position of the 3rd lumbar vertebra. Their precision as predictors of carcass tissues percentages was examined when they were used in addition to live weight at evaluation.

There was little consistency between trials in the positions and measurements which gave the most precise prediction. The lowest within-breed residual standard deviations of carcass lean percentage obtained with fat thickness measurements taken by Sonatest were in the range 2·5–2·7 and there was little advantage in using additional measurements in multiple regression.

Fat areas taken by Scanogram were more precise predictors (within-breed residual standard deviations were close to 2·0). Precision was improved marginally to about 1·8 by using combinations of fat areas but M. longissimus areas were of little additional value.

Sucking behaviour and age of weaning were investigated in a herd of East African zebu cattle in which all calves born had been retained for several years. Suckling rates were compared at different periods of the 24 h cycle and found to be less at night than during any day-time period. The highest rates of suckling took place in the early morning and in the late afternoon. The early morning suckling was triggered by the dawn. During both night and day, suckling was irregular and bouts were presumably due to sympathetic induction because a high proportion of the calves was suckled on each occasion. The total sucking time and the number of bouts varied significantly in inverse relation to age of the calf but the duration of a sucking bout was constant at 8 min and independent of age. There was an average of 4·8 sucking bouts within 24 h giving a total duration of 38 min. Sucking behaviour did not exhibit sex-specific differences. The average age of natural weaning was 10 months but there was a marked sex difference. Female calves were prevented by their mothers from sucking after an average age of 8·8 months but male calves continued to be suckled for a further 2·5 months and were weaned at an average age of 11·3 months.

Two years with contrasting weather, 1976 and 1977, were used to investigate the effects of nitrogen fertilizer on the uptake of nitrogen by crops of winter wheat and on the rate of photosynthesis of flag leaves. The studies involved a number of crops which received various amounts of nitrogen fertilizer at various stages of growth. Weekly measurements were made of the amount of nitrogen in the crops and its distribution within the plant, while a mobile gas exchange system measured the photosynthesis of individual flag leaves.

While the treatments imposed in 1976 resulted in different concentrations of nitrogen in the flag leaves, the maximum rate of photosynthesis and its efficiency in dull light were both unaffected when leaves of the same age were compared. The 2 years gave contrasting results in terms of the amounts of nitrogen taken up during grain growth: in the very dry summer of 1976 it could account for only 25% of the nitrogen in the ear at harvest while in 1977 it could account for almost 50%. These different amounts of translocation to the grain were accompanied by different photosynthetic behaviours of the flag leaves and our analysis shows that, in all treatments, the maximum rate of photosynthesis after anthesis was related to the fractional loss of nitrogen from the leaves.

The implications of these results for farming practice and for techniques used to investigate the effects of nitrogen on photosynthesis are discussed.

Observations were made on high resolution radiographs of foetal sheep, from ewes slaughtered at 7-day intervals from 34 to 55 days after mating, to examine the onset of ossification of some of the major components of the axial and appendicular skeleton. There were 83 foetuses measured, retrieved from 24 Finnish Landrace × Polled Dorset Horn ewes mated to Suffolk rams. The litters comprised five sets of twins, eight of triplets, seven of quadruplets, three of quintuplets and one set of sextuplets.

Half of the ewes were subjected to a 50% reduction in food on the 28th day of gestation, but this was considered not to have affected skeletal growth and development.

There were major changes in skeletal mineralization from one slaughter date to the next, particularly between 34 days, when no skeletal elements were detectable, and 41 days, when components of the skull, thorax, fore and hindlimbs were clearly seen. There were some differences in the number of primary centres present both within and between litters of the same gestational age. The mineralized shaft of the fibula was seen in 30/35 of the foetuses at 41 days, but only in 9/25 at 55 days; other transient centres were also observed.

Changes in the linear dimensions of six limb bones were measured and the mean values are presented in tabular form.

In a study of two breed groups, coarse wool Barki and ⅜ Merino ⅜ Barki, data were obtained on skin histology from birth to the age of 1 year, birthcoat fibre type arrays and fibre-follicle relationship.

The ⅜ Merino exceeded Barki lambs in the maximum S/P ratio, values of which were 3·40 and 5·64 obtained at 6 and 8 months in Barki and ⅜ Merino respectively.

Internal diameters of primary follicles ranged from 39·0 to 64·7 and from 41·0 to 56·8 μm; those of secondaries ranged from 19·8 to 34·9 and from 22·6 to 33·3 μm in Barki and ⅜ Merino respectively.

The ratio of primary to secondary follicle diameters showed high values in both breed groups; averages were 1·89 and 1·71 for internal diameter and 1·86 and 1·71 for external diameter in Barki and ⅜ Merino respectively.

Birthcoat fibre type arrays were mostly saddle, only 8·3% were plateau (P3) in both breed groups.

In Barki primary centrals grew halo hairs, super sickle (A, A′, B), primary laterals produced super sickle (A, A′, B), sickles, coarse and medium curly tips, and secondaries mostly grew medium and fine curly tips and histerotrichs.

In ⅜ Merino primary centrals produced halo hairs, super sickle (A, A′, B), primary laterals grew super sickle (A, A′, B), sickles, medium curly tips, and secondaries produced medium and fine curly tips and histerotrichs.

Five investigations were carried out to determine the magnitude of root-size variation within crops of cv. Chantenay Supreme grown under competitive and non-competitive conditions, and to study possible sources of inter-plant variation.

In the first experiment root-size variation from crops grown at a high population density (245 plants/m2) and at a low density (25 plants/m2) were compared over a 21-week period from sowing. The c.v.s of root weight were always higher from the high density than from the low density over the harvesting period from 11 to 21 weeks after sowing, and ranged from 74 to 94% and from 50 to 63%, respectively. A second study showed that even with a very low population density (3 plants/m2) the c.v. of root weight at harvest was 58%. The third study showed that 40% of the root weight variation was accounted for by the time of seedling emergence. The results of a pot experiment indicated that when the size of seed, sowing depth, rooting medium and time of seedling emergence were made as uniform as possible, a very uniform population of roots was produced with a c.v. of root weight of 32%. In the final field experiment when time of seedling emergence, seed size and spatial distribution of the plants were the experimental variables, the results confirmed the importance of variability in time of seedling emergence and seedling size in creating variation at an early stage of growth.

The results of these studies indicate that competition per se was not a prime source of variation in root size but magnified any initial variation within the crop at the time of seedling establishment. The importance of this early establishment phase in determining the spread of root-size distribution within a crop is discussed together with the factors which influence the time of seedling emergence and seedling size.