The survival of potted plants of the North African Festuca arundinacea populations syn. 1 and syn. 2 was compared to that of the British cultivar S. 170 following 18 h periods in a growth cabinet at 24 °F, 21 °F and 18 °F. No plants in any of the three populations were killed by the 24 °F or 21 °F treatments but, following the 18 °F treatment, survival of both synthetics was greatly reduced, especially amongst plants that had been cut back to 1 in. (2·5 cm) 6 days prior to the cold treatment. Reduction in tillering and deaths in syn. 1 were both greater than in syn. 2. Both cut and uncut plants of S. 170 survived the 18 °F treatment, their tillering being relatively little affected.

In a subsequent study, survival of syn. 1 and syn. 2 at temperatures decreasing to 16 °F was less amongst plants cut back to soil level than amongst those cut back to 3 in (7·5 cm) or left uncut. No differences were detectable between survival in the two synthetics, nor was there any significant effect, on such survival, of time interval prior to the cold shock.

The results showed close agreement with previous patterns of winter survival of these populations in the field.

Ewo milk yield data obtained by the lamb suckling technique from nutritional experiments were analysed statistically to obtain estimates of the several components of variation. Diurnal variation was studied. The fitting of a sinusoidal curve removed a significant amount of variation.

There was a highly significant correlation between successive milk yields obtained at 4 h intervals. Number of lambs suckled and body weight of ewe at parturition had a significant effect on total daily milk yield.

The variation within ewes after the removal of diurnal variation and between ewes after the removal of the effects of number of lambs suckled and body weight at parturition were computed. These sources of variation were combined in a general equation which enabled the prediction of the standard errors associated with daily milk production for a given sampling technique. The practical application of the predicted standard errors is discussed.

Following three differing pre-stress temperature treatments, potted plants of three populations of Festuca arundinacea, syn. 1 and syn. 2 (North African) and S. 170 (British) were subjected to a cold stress of 20 h at – 8 °C in a growth cabinet.

In all populations, survival was greatest when the cold stress followed continuous low temperatures for 2 weeks, was intermediate after part-day low temperatures for the same period, and poorest after continuous warmth. The hardening response, especially after the fluctuating regime, was greater in S. 170 than in either syn. 1 or syn. 2, between which little difference was detectable.

There was no overall difference in survival between spring-sown and autumn-sown material, nor any apparent relationship between survival and relative growth rate.

In a further trial, the same three populations were subjected to differing periods of cold stress at — 9 °C-single exposure for 12 or 18 h periods, or one, two or three 6 h periods.

The synthetics were progressively weakened by repeated stresses, and were almost completely killed out by 12 or 18 h exposure. Differences in mortality following short and longer periods of exposure were associated with differences in soil temperatures.

Data collected from mid-pregnancy until the 5th week of lactation were used to select three nearly uniform groups each of nine ewes suckling single lambs. After 4 weeks of lactation, experimental treatments were applied to these selected groups as follows: Group I. Both ewes and lambs fed ad lib.throughout. Group II. Ewes fed ad lib. throughout. Lambs offered one-third the quantity of solid food being consumed by group I lambs. Group III. Food intake of ewes restricted to 9·2 g D.o.M./kg, based on their mid-pregnancy live weights. Lambs fed ad lib. throughout. The effects of these treatments were assessed in terms of milk production, food intakes and live-weight changes of ewes, and the solid food intake and growth rates of lambs. Mean total milk production of ewes of groups I and II remained similar until the 8th lactation week, but during the 8–12 week period milk production of the ewes in group II was 6·17 kg greater than that of ewes in group I. The data suggest this difference was due to a reduced intake of milk by the lambs suckling the ewes in group I during the weaning process. From week 4 the milk yield of group III ewes declined rapidly and though these ewes drew on body reserves for milk production, this process could not sustain milk yields. The average daily live-weight gains of lambs of groups I and III were both significantly greater than that of group II, and the gain of group I lambs was significantly greater than that of group III. All groups of ewes made similar live-weight gains during early lactation and after 4 weeks each group had attained a mean value of about 60 kg. Groups I and II continued to gain weight and during week 12 their respective mean weights were 67 and 65 kg. This difference was not statistically significant. The mean live weight of group III ewes declined rapidly after week 4, reaching a minimum value of 41·5 kg. The mean daily intake of dry matter by ewes of all groups reached a maximum value of about 2·9 kg/ewe in lactation week 3 and declined to about 2·6 kg in week 4. Intakes by ewes in groups I and II were almost identical throughout. During the period of restricted feeding the mean daily intake of group III ewes was 0·58 kg dry matter/ewe. During week 5 the mean daily intakes of solid food dry matter by lambs of groups I, II and III were 44, 32 and 158 g respectively. These increased to 1230, 418 and 1537 g respectively during week 12.

The effects of annual applications of up to 300 lb/acre of N, 100 lb/acre of P2O5 and 200 lb/acre of K2O on cut swards of S. 24 ryegrass, S. 37 cocksfoot and S. 215 meadow fescue were measured in an experiment lasting 3 years.

There were some differences between species in their dry-matter and nutrient yield response to nitrogen and potash applications, but not to phosphate. These differences were inconsistent and over the 3-year period were negligible.

A large response to nitrogen was only fully maintained when phosphate and potash were also applied. There was no response above 50 lb/acre of P2O5 in any year. In the second year, 100 lb/acre of K2O was sufficient, but more than this was necessary in the other years. Symptoms of phosphate and potash deficiency were seen where high rates of nitrogen were applied without phosphate and potash respectively.

Plants of three populations of Festuca arundinacea, syn. 1 and syn. 2 (North African) and S. 170 (British) were subjected to 3 h cold stress treatments in the range 13–25 °F. Such treatments were applied independently to either roots or shoots, the untreated plant portions remaining at 35–40 F°.

In all populations considerable tiller death occurred following exposure of roots to temperatures of 17 °F or below; however at no temperature was there complete killing of tillers. Tiller deaths occurred following shoot exposure to temperatures below 21 °F in syn. 1 and syn. 2, and below 19 °F in S. 170. Universal mortality occurred in all populations after shoot exposure to 13 °F.

The degree of insulation of the root: shoot junctions affected survival of both roots and shoots in all populations. Discrepancies between apparent damage to plant parts following treatment, and subsequent survival, suggested that the ability of plants to replace damaged parts might influence survival.

Conclusions are included from the completed programme of growth cabinet studies on cold tolerance of F. arundinacea populations reported in the present series of papers.

The incidence and distribution of haemoglobin types and potassium and sodium concentrations in whole blood of 411 Sudan Desert sheep and 11 Merino sheep were determined. Haemoglobin types were distinguished by electrophoresis in starch gel and blood potassium and sodium levels by flame photometry.

Of the 411 animals examined, 396 possessed haemoglobin B in the homozygous state while only 15 possessed haemoglobin AB. The homozygous AA haemoglobin was not detected. No bimodality was found in whole blood potassium and sodium levels and the distributions were normal.

Using Persian Blackhead ewes, milk composition and the effect of diet on content of milk fat and milk yield were investigated. Analysis of the milk of nine ewes for fat, protein, ash and lactose (by difference) throughout a twelve-week lactation gave results which were compared with those in the literature. Average values were 5·9, 5·6, 1·0 and 4·8 % respectively. The milk of nine ewes fed on a high plane of nutrition contained significantly more fat than that of ewes fed on a low plane of nutrition; values were 8·8 and 8·3 % respectively. High plane ewes gave significantly more milk than low plane ewes. Ewes suckling twins gave significantly more milk than those suckling singles. Lambs suckling high plane ewes gained significantly more weight than those suckling low plane ewes both from birth to 3 weeks as well as from birth to 12 weeks. Male lambs gained significantly more weight than females.

Highly significant correlation coefficients were obtained between milk consumed by the lamb and its gain in weight. Conversion efficiencies of milk to gain in weight were calculated and compared with literature values.

Diallel crosses, without reciprocals, were made between two strains resistant to leaf curl and two susceptible strains as part of a breeding programme for leaf curl resistance. F1, F2, F3 and backcross progenies were studied. Results revealed that leaf curl resistance, previously described as polygenic, is controlled by a major dominant gene designated as Vr1. The presence of minor modifier genes was also indicated.

Results of 132 maize fertilizer experiments (NP and NPK) carried out over 3 years in Western Tanzania have been grouped to give sixteen ‘response areas’. Responses to N and P were very large in the south-western half of the research zone, where rainfall is fairly well distributed. On granitic soils around Lake Victoria, responses were mainly to N alone. In the drier areas, notably Shinyanga district, responses to both N and P were on average very small. No significant positive responses to K were found, except for one trial in Karagwe district.

It was found that all observed responses to N and P could be accounted for in terms of a generalized two-factor Mitscherlich-Baule yield equation, with constant curvature terms, cn and cv.

Using this equation it is possible to define ‘maximum economic requirements’ of the nutrients N and P for various maize and fertilizer prices and potential yields. The difference between this maximum requirement and the amounts of these nutrients supplied by the soil (given by the Mitscherlich-Baule parameters bn and bp',)represents the optimum rate of fertilizer application, where profit per acre is at a maximum.

Empirical equations are presented for estimating b from soil analysis results for areas not adequately covered by these experiments, but such estimates may not always be accurate.

The effects of N, P and K applied broadcast on yields, percentage nitrogen and kernel weights of barley were studied over two seasons.

The average yield increase over thirteen sites was 5·1 cwt and 8·2 cwt from applications of 35 lb and 70 lb/acre of fertilizer N respectively. A mean yield increase of 4·4 cwt/acre was obtained from 27 lb P at four sites where the soil phosphorus test did not exceed 2 ppm P. Potassium applied at rates varying from 0 to 168 lb K/acre increased yields at one site only and decreased them at another site.

The mean grain nitrogen percent without fertilizer N was 1·47 and applications of 35 and 70 lb N/acre gave increases of 0·06 and 0·19% respectively. The overall effects of P and K on the percent nitrogen in the grain were small.

Applications of 35 and 70 lb N/acre increased the mean 1000 kernel weights by 0·7 and 1·0 g respectively. When lodging occurred kernel weights were decreased. Fertilizer P and K had little effect on the kernel weights.

The significance of these data are discussed in relation to previous cropping and rainfall during the growing season and during the previous winter.

Twelve Friesian heifers were given four dietary treatments from 2 months before first calving to the end of the first lactation. Two of the treatments involved the ad libitum feeding of a complete diet consisting of a basal concentrate meal of rolled barley with supplements, incorporated into a mixture with either hay or barley straw both coarsely ground and included at a level of 25 % of the complete mix. In the other two treatments either the hay or the straw was given ad libitum in the long form and the concentrate mix fed ad libitum from a separate self-feeder.

Full records were kept of the intake of food and water, the output and quality of the milk and of live weight. Detailed measurements were made of various aspects of rumen function using one cow on each treatment fitted with a cannula. Rumen samples were also obtained from non-fistulated cows by stomach tube.

The intake of long roughage, particularly straw, by the cow, when offered in conjunction with a separate supply of the concentrate mix, was very low and led to serious falls in milk butterfat content. Where the roughage was incorporated into the complete diet normal butterfat levels were maintained. However, apart from the depressed butterfat levels on the two long roughage treatments the health and condition of the cows remained good.

The very low intake of long straw was associated with a smaller volume of liquid in the rumen, a reduced rate of flow of liquid leaving the rumen, a lower proportion of acetic and butyric acids and a greater proportion of propionic acid in the rumen liquor and finally with a higher blood glucose content. The inclusion of milled roughage resulted in values within the normal range for volume of liquid in the rumen, flow rate of liquid from the rumen, V.F.A. proportions in the rumen liquor and blood glucose.

The intake of both food and water over the productive cycle showed a consistent pattern for all cows. Food intake reached its lowest point around calving followed by a sharp rise to a peak in the 4th month after calving and then a gradual but increasing decline. Water intake followed a similar pattern but the fluctuation was greater and the peak consumption occurred in the 3rd month of lactation. Water intake was more closely associated with D.M. intake than with milk output.

The efficiency of utilization of the complete diets containing the milled roughages is discussed in relation to comparable data from cattle fed conventionally.

The effects of changing plant density and nutrient supply on the yield of swedes were measured in nine experiments over 3 years. With small populations, a large nutrient supply was required to reach the maximal yield of roots, but with large plant populations the same nutrient rate depressed yield. This interaction is illustrated by a response surface, and reasons for it are discussed. The interaction is of limited importance in practice because it was small over the range of population and nutrient supply commonly used. Even with small populations, the compensation achieved by applying more fertilizer was uneconomic. On crops with large populations, such as swedes for human consumption, however, the normal recommended rate of fertilizer should not be exceeded because of loss of yield as well as increased cost. More fertilizer and greater plant density were needed to give maximal total yield (roots + tops) than of roots alone. Effects of nutrient supply and plant population on plant establishment and dry-matter content of the swedes are discussed.

Percentages of soluble dry matter (S.D.M.), determined in expressed sap from the pith of kale stems by using a hand refractometer, were higher near the vascular bundles than in the centre of the pith and also varied from the top to the base of any one stem. Sampling errors were minimized by taking vertical borings midway between the vascular bundles and the pith centre and by taking two bores per stem (base and top). Inbred lines varied for mean S.D.M. Relative S.D.M. values for two inbred lines were maintained through wet and dry periods in the autumn, and values for fifty-eight inbred lines were significantly correlated in the successive years, one with a dry autumn and the other with a wet.

S.D.M. values were positively and significantly correlated with dry-matter percentage (D.M.) of the pith and with total water soluble carbohydrates (W.S.C). Close correlations were also found between S.D.M. and resistance to cold damage, both in the field and in freezing cabinets for inbred lines of marrow-stem kale and for other cultivars of Brassica oleracea. Although there are some exceptions to these correlations, the rapid method for determining S.D.M. should be very useful in screening breeding material for cold resistance. The combination of high percentage digestibility of the dry matter of stems and improved winter-hardiness can be achieved by selecting in addition for low fibre content using penetrometer tests.

In a 2-year experiment conducted on a pure S. 24 perennial ryegrass sward, fertilizer nitrogen in the form of ‘Nitram’ (34·5%) N was applied at rates of 100, 200 and 300 lb/ acre either as single dressings in the spring or as two, three, four or five split dressings at successively later dates in the growing season. Total yields of herbage dry matter and of crude protein, and their distribution over the season, were determined by cutting the herbage five times at intervals of approximately 5 weeks. Yields of herbage dry matter were increased by increasing the nitrogen application rate and by splitting the total amount of fertilizer nitrogen into either three or four equal dressings. The mean crudeprotein content of the herbage dry matter was increased by increasing the nitrogen application rate, but it was reduced by splitting the total amount of fertilizer into several dressings. The nitrate content of the herbage was higher after a single heavy dressing of fertilizer nitrogen than after several split dressings. It is concluded that the optimum application programme for a total rate of 100 lb nitrogen/acre was three split dressings each of 33J lb/acre, and for the 200 and 300 lb nitrogen/acre rate, four split dressings of 50 and 75 lb/acre respectively.

Although beans are grown primarily because samples they are richer in protein than the cereal grains, the energy they contribute to mixed diets is also important. An unpublished computer calculation of least-cost formulae for laying hen diets has indicated that if two samples of bean meal were of the same composition, except that one had 300 kcal/lb more metabolizable energy (M. E.) than the other, its worth would be more than £3/ton greater. The actual range of values taken for bean meals in this country is considerably wider than 300 kcal/lb. Bolton (1963) lists a value of 830 kcal/lb, whilst Bolton (1967) lists 1400 kcal/lb. Titus (1955) lists 610 and 640 kcal/lb though specifying that these values refer to navy beans and pinto beans respectively (both being Phaseolus vulgaris). Bletner, Chalhoub & Geff (1963) were unable to find any published value for ‘horse’ or ‘field’ beans as (i. e. Vicia faba), the type normally used for animal feeding in Britain.