Birthcoat samples from Lincoln and Welsh Mountain lambs born in an ova transfer experiment (Weiner & Slee, 1965) were examined to determine the fibre type arrays and any effect of ova transfer on manifestation of the prenatal check or the base (Dry, 1965).

In the Lincoln breed arrays were Truncated Ravine or Truncated Valley thus showing central checking. Pre-curly tip fibres were mainly confined to central primary follicles. Post-natal medullation was plentiful, especially in peak curly-tips, but kemp was absent. In the Welsh lambs all identifiable arrays were either Plateau or Saddle, with the lateral primary fibres more checked than the centrals. Pre-curly tip fibres occupied almost all the primary follicles, with only a few curly-tips in primary laterals. Post-natal medullation was strongest in pre-curly tips and their successors.

The effect of ova transfer was to decrease the manifestation of check in Lincoln-in-Welsh and increase it in Welsh-in-Lincoln, without affecting the base. Although this, in each case, changed the check of the lamb in the direction of that of the foster breed, it is suggested that this may not be due to any influence of maternal check on foetal check. The effect on pre-natal check may be due to foetal size, and in particular skin expansion, during a short period immediately following completion of primary follicle initiation. As compared to their respective controls, the Welsh transfer lambs had a higher S/P ratio at birth, whilst that of the transferred Lincolns was reduced.

If increased prenatal fibre check is associated with increased foetal growth rate at the relevant period, it may also be correlated with increased lamb size at birth and therefore have been favoured in selection for meat production, at least in some breeds.

In each of two experiments the comparative slaughter technique was used to compare the retention of energy by young Border Leicester × Merino wethers when the same total amount of food was offered according to two different feeding regimens. These were designed to simulate, in pens with a diet of pelleted lucerne, feeding patterns typical of continuous and intensive rotational grazing.

In the first experiment ten 9-month-old sheep that were offered the same amount of food daily (mean intake 367 g digestible organic matter) during each of 14 weeks made mean daily gains of 39 g live weight, 6·3 g body fat and 0·59 MJ (140 kcal) energy compared with a gain of 30 g live weight, a loss of 1·4 g body fat and a gain of 0·28 MJ (67 kcal) energy by a similar group that ate the same total quantity of food but in amounts that ranged, during each week, from 1·8 to 0·1 times the daily intake of the other group. This cyclic feeding pattern caused a small decrease in the digestibility of dietary organic matter.

In the second experiment two similar feeding patterns were compared with ten pairs of 3-month-old sheep eating twice as much food each week as in the first experiment. One member of each pair was, in each of 13 weeks, offered food ad lib. for 3 days and then amounts falling to 20% of voluntary intake on the seventh day; the other one ate the same amount of food each week but in seven almost equal feeds. The latter sheep gained, on average, 132 g live weight daily and retained 58 g body fat and 2·96 MJ (707 kcal) energy compared with 124 g live weight, 49 g body fat and 2·61 MJ (624 kcal) energy by the sheep on the cyclic feeding pattern. In neither experiment was wool growth affected by feeding pattern.

The greater effect of the cyclic feeding pattern in reducing the efficiency of energy retention in the first experiment is attributed to the higher number of days each week during which these animals were estimated to be in negative energy balance. These results suggest that adverse nutritional effects of a fluctuating feeding pattern in rotational grazing are likely to be most important where sheep are being rationed near their maintenance level and only small where food is ample.

Recently developed mathematical models have been used to study the effects of plant population density and arrangement on the yield of cotton in central Uganda. Optimum density did not vary with variety, but was less with bollworm infestation, infertile soils and drought. A reasonable compromise between a population density suitable for adverse conditions and one suitable for good conditions is 7·4 plants m−2. This population is best achieved with 0·45 × 0·25 m spacing but if such rows are too close to manage then 0·2 m in rows 0·7–0·9 m apart is recommended. The mathematical models used in the study are discussed and appraised.

Early stages in the development of reproductive tillers of S. 24 and S. 23 perennial ryegrass are described. The pattern of development of the stem apex and of the unemerged leaves present at the time of floral initiation is traced up to the time when internode extension results in the elevation of the stem apices above the level of defoliation. If tillers with stems about 10 cm long, or more, escape damage to the stem apex during defoliation, the regrowth may be expected to deteriorate rapidly in leafiness, since at this stage there are few or no unemerged leaves. Tillers with 3–4 cm stems generally bear 1–2 unemerged leaves, and hence the regrowth is more leafy.

For a given stem length apical development was slightly more advanced in S. 24 than in S. 23. Consideration is given to selection methods to be used in breeding for leafy regrowths in springtime.

Two chickpea pure lines, one being short and wide in stature and the other tall and narrow, were crossed. Parents, F1 and F2 generations were grown in the field to study the inheritance of plant dimensions, as well as their correlation with seed yield. Heritability, in broad sense, for plant height and width was 36 and 20% respectively. Estimated minimum number of genes for plant height was two and for plant width was three pairs of genes. Plant height showed correlation values of 0·43 and -0·67 with yield of seed and 1000 seed weight respectively. There were no significant correlations between plant width and the same two yield components.

Certain aspects of puberal development and reproductive performance in Clun Forest ewe lambs with a wide range of birth dates were investigated during the two seasons 1969–71. Of 33 ewe lambs born in the spring of 1969, 26 exhibited their first oestrus at a mean date of 8 November 1969 ± 2·5 days, the mean age being 228·3 ± 2·4 days and the mean body weight 36·3 ± 0·9 kg. The lambs which failed to breed in their first year, together with lambs born in the autumn of 1969, attained puberty during the autumn of 1970. Twenty-three ewe lambs carried foetuses to term in the spring of 1970 and had a mean lambing rate of 113·0 ± 7%. Of 84 ewe lambs born in the spring of 1970, 73 attained puberty in the first year of life at a mean date of 11 November 1970 ± 2·7 days, the mean age being 223·7 ± 3·0 days and the mean body weight 32·2 ± 0·5 kg. Cyclic activity of ewe lambs born in 1970 was recorded throughout their first breeding season. They experienced their last oestrus of the season at a mean date of 24 January 1971 ± 2·2 days, the mean age being 296·9 ±3·9 days and the mean body weight 32·4 ± 0·6 kg. The mid-breeding season was 18 December 1970, coinciding with the shortest days, and the mean number of heats exhibited throughout the season was 5·15 ± 0·24 per lamb.

Marked individual variation existed in age and body weight at puberty and in breeding activity, largely due to differences in date of birth and growth rate during rearing. Ewe lambs born early tended to experience their first oestrus earlier in the season than late born lambs but they did so at a higher age and heavier body weight. Fast growth rate and earliness of puberty were associated with extended duration and enhanced regularity of cyclic activity. Time of birth was clearly of fundamental importance in relation to the onset and duration of breeding activity in the ewe lambs included in the present study.

Adult rams of three breeds were found to vary consistently in the proportion of ewe lambs which they detected in oestrus, rams of the lambs' own breed being most efficient.

Significant differences were found in the flavour characteristics of stewed minces from lambs raised on either lucerne or phalaris pastures. The meat from lambs raised on lucerne had a more intense ‘sharp’ and ‘sickly’ aroma and flavour and a significantly lower flavour acceptability. These characteristics were not significantly alter when the lambs were starved for up to 3 days before slaughter. However, the flavour of meat from lambs transferred from lucerne to phalaris 7 or 14 days before slaughter was not significantly different from that of lambs grazed solely on phalaris.

Merino wethers grazed pure stands of rape, vetch or oats for 76 days in 1969 and 35 days in 1970. A laboratory taste panel found that the flavour characteristics of meat from these sheep differed significantly from those of meat from similar sheep grazing ryegrass-white-clover pasture or native pasture.

Grazing on rape often produced a meat with a nauseating aroma and flavour, and with significantly lower acceptability of flavour than the pastures. There was no significant difference in the acceptability of flavour of meat from pasture and vetch fed sheep, although vetch gave an intense meaty flavour. Meat from sheep grazing oats possessed a pungent odour and flavour, but with a flavour only slightly, but significantly, less acceptable than that of meat produced on pasture.

An experiment is described which investigated for a period of 12 years the effects of four methods of basic cultivation – ploughing, rotary cultivating, cultivating and discing – on crop yields in a four-course rotation of winter wheat, sugar beet, spring barley followed by either potatoes (on one half of each main plot) or ley (on the other). The cultivations were carried out at two different times and each crop was grown at two levels of fertilizer.

The method of cultivation had no effect on the yield of barley when weeds were controlled by chemicals but, in the absence of such control, the three deeper working methods of cultivation gave higher yields than discing towards the end of the experiment. In the case of wheat, ploughing generally led to the highest yields and rotary cultivating led to higher yields than either cultivating or discing after the ley. Discing led to relatively low yields, particularly with cultural methods of weed control at the lower level of fertility.

With the sugar-beet crop, yields of sugar were higher in all rotations after ploughing than after cultivating or discing, irrespective of the method of weed control and although yields after rotary cultivating were similar to those after ploughing in the second rotation they did not consistently exceed those after cultivating or discing in the other two rotations. With discing, in the absence of chemical weed control the yields were markedly reduced in the last rotation period. Ploughing also led to the highest yields of potatoes but there were no consistent differences between the other methods and an apparent trend to lower yields after discing in the absence of chemical methods of weed control had not reached significance by the end of the experiment.

It was concluded that ploughing was a more reliable method of seedbed preparation, not only with regard to consistency of performance under different conditions but also with regard to depth of working and extent of weed control.

Ploughing appeared to be of particular value with the root crops used but the other methods led to satisfactory yields of the cereals grown after roots.

Three maize hybrids (Kelvedon 75A, Kelvedon 33, and Anjou 210) were grown under irrigated conditions at a wide range of density from 5·4 to 21·6 seeds/m2 at a rectangularity of 1:1. For yield of digestible dry matter at the time of silage harvest (7 October) a seed rate of 10·8 seeds/m2 (44000/acre) appeared adequate, as doubling the density to 21·6/m2 only resulted in 7% higher yield. K 33, which is a late·maturing hybrid bred for silage in south-east England (50·5–52·5 °N) produced the highest total yield of digestible dry matter due to a high yield of digestible stem. However, the dry matter % of this material would be too low for good ensilage and for a high level of feed intake. In the early grain hybrid K 75 A, 62% of the digestible dry matter was contained in the ear at the silage stage which improved the digestibility and dry matter % of the whole crop with only a 12% lower yield than K 33.

The optimum density for grain was 10·8 seeds/m2. This is a higher response to density than is believed to occur in field crops in Britain as in these experiments the seed was planted on the square and irrigation was applied at moisture sensitive stages. The parabolic relationship between grain yield and density was closely related to grain number per unit area. At 10·8 seeds/m2 all three hybrids were of similar yield and grain number per unit area. In Anjou 210 this was achieved with one large ear per plant, whilst for the two Kelvedon hybrids mean ear production was 1·34/plant but with 27% fewer grains per ear.

Work that has been reported from some African countries indicates a dependence of grain yield in maize on the duration of leaf area after flowering. This paper studies maize yield in south-east England and confirms work at a similar northern latitude in Canada which has shown that considerable remobilization of photosynthate from the stem to the ear takes place during the main ear fill period.

A similar grain yield was obtained from two contrasting hybrids. In a short early hybrid, Kelvedon 75A, there was a low peak leaf area index (5·3) but the net assimilation rate was high due possibly to efficient light interception by leaves that maintained an erect posture. Stem dry matter was also low and hence in this hybrid the high reproductive/vegetative ratio shows that there has been economy in the production of leaves and stem, especially as a 48% stem loss occurred during the period of ear fill.

In contrast, in a later hybrid, Anjou 210, the final shoot dry matter was 20% higher as the peak leaf-area index of 7·7 gave slightly higher crop growth rates than K 75A. Although the remobilization of stem dry matter was similar in both hybrids it was notable that a different partition of dry matter in the ears of Anjou 210 gave a higher grain/rachis ratio.

In three experiments high quality, autumn-harvested dried Italian ryegrass and lucerne in the form of cobs and pellets and in one of these experiments in the chopped form were offered to mature castrated male sheep at a maintenance level of feeding. Only small differences were found between the physical forms of forage in digestibility of organic matter, retention of nitrogen and loss of energy in the urine, but the digestibility of crude fibre and the mean retention time of stained feed in the gut decreased with decreasing particle size. Increasing the level of feeding of cobs and of pellets from 800 g daily by three equal increments of 400 g caused a linear decline in digestibility but no difference was found between cobs and pellets in the rate of decline of digestibility. In three experiments the dried forages were offered ad libitum and in a fourth experiment a wide range of particle size was simulated by offering ad libitum five ratios of chopped and pelleted grass. Voluntary intake tended to increase as the particle size was reduced over the whole range, but there was no significant difference between the voluntary intakes of mixtures with a modulus of fineness of 4·4 or less. No difference was detected between the voluntary intake of cobs and pellets.

An experiment was conducted using 36 Hereford × Shorthorn bullocks of about 350 kg initial live weight. Winter planes of nutrition 13 December to 23 March were ‘low’ (hay only) and ‘medium’ (hay plus 1·8 kg concentrate); the former group of 18 bullocks lost on average 21·5 kg while the latter gained 26·5 kg. Each group was then stocked at 2·5 (low), 4·3 (medium) and 6·2 (high) bullocks per hectare and rotationally grazed on 10 plots, 7 of which contained H.I.-white clover mixture and the remaining 3 contained permanent pasture. Pasture digestibility and intake were determined for 16 weekly periods between early April and the end of September. Organic matter digestibility (OMD) of grazed herbage was determined in vitro on samples obtained by means of two rumen-fistulated bullocks. One gelatin capsule containing about 10 g of chromic oxide was daily administered to each bullock to estimate organic matter output. Winter feeding planes had no significant effect on OMD, and increasing the stocking rate increased herbage OMD only during the final 6 weeks. Significantly more organic matter was ingested during the grazing season by animals which had previously been fed on a low plane of nutrition. Stocking rates also significantly affected OMI. Bullocks fed on a low plane during winter were slightly more efficient subsequently in converting herbage into live-weight gain but this was a reflection of their lower average body weight; when feed efficiency was expressed on the basis of metabolic size, bullocks fed on a medium plane were more efficient in converting feed to live-weight gain. It is concluded that the higher daily gains on pasture of bullocks previously fed on a low plane is largely the result of a significantly higher feed intake by these animals.

Following both a low and high plane of winter feeding two groups of 18 bullocks each were stocked at 2·5 (low), 4·3 (medium) and 6·2 (high) bullocks per hectare. The Hereford × Shorthorn bullocks averaging 350 kg live weight were rotationally grazed on ten plots, seven of which contained a H.I. white clover mixture and the remaining three contained permanent pasture. Pasture digestibility and intake were determined for 16 weekly periods between early April and late September. In vitro digestibility was determined on samples obtained by means of two rumen-fistulated bullocks. A gelatin capsule containing 10 g of chromic oxide was administered daily to each bullock to estimate faecal output. Digestibility, faecal output and intake were expressed on both a dry and organic-matter basis. Increasing the stocking rate resulted in a corresponding decrease in organic matter (OM) percentage of the faeces but the magnitude of the differences varied throughout the growing season. The average decline (all 16 periods) was linear, the OM percentage of faeces being 80·9, 76·8 and 72·6 for low, medium and high stocking rates, respectively. Faecal ash content of rectal samples and those taken from the pasture differed significantly only in a few instances, indicating that pasture faecal contamination may not be serious if careful sampling is practised. Higher ash intakes at high stocking intensities are reflected in herbage intake errors when results are expressed as dry matter instead of organic matter.

Thirty-two beef calves (mean body weight 79 kg) were given a ration which depleted their body reserves of Na as was evidenced by a narrow Na to K ratio in the parotid saliva. Eight calves were then assigned to each of the following four treatments: low Na basal ration alone, basal ration plus either 1·09, 2·19 or 3·28 g Na/calf/day as bicarbonate.

Forty 6½-year-old Scottish Blackface ewes were used in an experiment to investigate the effects of low protein and low calcium (Ca) intakes during pregnancy on body composition and mineral contents. Six sheep were slaughtered at the commencement of the experiment as controls; 28 were used in a 2 × 2 factorial experiment in which semipurified diets containing 11·8 and 6·0% crude protein (CP) and 1·2 and 0·11% Ca in the dry matter were offered to maintain non-esterified fatty acids (NEFA) and ketone bodies in the plasma at levels comparable to those found in hill sheep in winter. All ewes were slaughtered after parturition and the carcase dissected into soft tissue and skeleton fractions. Both fractions were dissolved in HNO3 and the fat and mineral contents measured.

The effects of low protein and low Ca intakes during pregnancy on lamb composition and mineral contents have been investigated. Twenty-eight 6½-year-old Blackface ewes were used in a 2 × 2 experiment in which semi-purified diets containing 11·8 and 6·0% crude protein and 1·2 and 0·11 % Ca in the dry matter were offered to maintain constant levels of non-esterified fatty acids (NEFA) and ketone bodies in the plasma, comparable to those found in hill sheep in winter. A further group, control, were fed a conventional diet containing adequate crude protein and Ca to maintain NEFA and ketone body levels typical of well-nourished sheep. The lambs were killed at birth and whole body fat, moisture, nitrogen, Ca, P, Mg, Na and K contents determined. Further data was obtained on the brain, liver and semitendinosus muscle.

Within the context of the experiment the most important factor in determining the mineral content of the lambs was the protein intake of the ewe, mainly due to its effect on lamb body weight. The mean Ca content of lambs from the control ewes was 47·8 g. By comparison that of lambs from the high and low protein groups was reduced by 4·9 and 12·9 g respectively.

Calcium intakes as low as 27 mg/kg ewe body weight/day had no significant effect on lamb birth weight or mineral composition.

The mean concentrations (g/kg) of minerals in the fat-free bodies of the lambs ranged from 12·1 to 14·6 for Ca, 6·6 to 7·4 for P, 0·49 to 006 for Mg and from 1·9 to 1·6 for K in the control and double deficiency groups respectively. It was concluded that these changes in lamb composition could be interpreted according to classical studies on the influence of undernutrition on the relative growth and development of animal tissues.

The livers of the lambs, although significantly reduced in weight by the protein deficiency showed no evidence of being relatively more severely affected than muscle tissue.

Twenty-eight 6½-year-old Scottish Blackface ewes were used in a 2 × 2 factorial experiment and given semi-purified diets containing 11·8 or 6·0% crude protein (CP) and 1·2 or 0·11 % calcium (Ca) in the dry matter (DM). The amounts of diet offered were adjusted to maintain non-esterified fatty acids (NEFA) and ketone bodies in the plasma at levels comparable to those found in hill sheep in winter. Mean group values of NEFA during the final 6 weeks of pregnancy were maintained at these levels (1100–1300 μ-equiv/1) and ketone bodies at approximately 4·8 mg/100 ml. A further six sheep were fed a conventional diet containing adequate CP and Ca, to maintain NEFA and ketone bodies at levels typical of well-nourished sheep. Ewes and lambs from the undernourished groups were slaughtered after parturition and the chemical compositions of their bodies and those of six ewes slaughtered at the commencement of the experiment determined.

The results obtained for dry matter and energy digestibility with 116 different rations fed to 242 non-pregnant dry cows and 96 laotating cows were studied.

With winter rations, dry-matter digestibility (Y) is linearly related to dry-matter intake (X1) and to the crude fibre content of the dry matter (X2):

Y = 89·58–0·557X1–0·863X2.

A similar equation was obtained for energy digestibility (Y):

Y = 90·68–0·195X1–0·892X2,

where X1 represents the energy intake (in 1000 kcal) and X2 the crude-fibre content.

Digestible dry matter or energy can be estimated very accurately from dry matter or energy intake and from crude-fibre content.

There is a highly significant linear relation between dry matter or energy digestibility and nitrogen concentration of the faeces, especially with grass.

Dry-matter digestibility is also influenced by the physical form of the feeds and by individual factors.

The results obtained for nitrogen and ether extract digestibility with 116 different rations fed to 242 non-pregnant dry cows and 96 lactating cows were studied.

A hyperbolic relation exists between nitrogen digestibility (Y) and crude protein content (X), with the equation:

Y = 88·6–(301/X)(r = – 0·928**, RSD = 4·78).

Digestible protein content ( Y) is linearly related to crude protein content(X):

Y = 0·90X-3·10 (r = 0·982**, RSD = 0·823).

From dry-matter intake and crude protein content it is possible to estimate accurately the amount of digestible nitrogen. With all the experimental rations the mean metabolic faecal nitrogen was 496 mg/100 g of ingested dry matter, and the true nitrogen digestibility was conspicuously constant up to 90%.

Digestibility of ether extract depends on the nature of the feeds. When the concentrate percentage of the ration is high, the digestibility of ether extract obeys the same laws as that of nitrogen.