Published and unpublished results for apparent nitrogen digestibility from 107 digestibility trials with Zebu (Africander, Brahman and their crosses with British cattle) and British breeds of cattle were analysed by regression analyses to determine its relationship with dry matter intake and dietary nitrogen content.

The linear regression of apparent nitrogen digestibility on the reciprocal of dietary nitrogen content was an adequate mathematical description of the relation (r = 0·92) and the addition of the reciprocal of nitrogen intake as an independent variable improved the description (r = 0·95) particularly for diets with a low nitrogen content. Both these equations have a physiological basis.

Estimates of the true nitrogen digestibility and metabolic faecal nitrogen from the linear regression of apparent nitrogen digestibility on the reciprocal of dietary nitrogen content were 86·8% and 0·49 g/100 g dry-matter intake. Independent estimates of these parameters from a multiple regression of total faecal nitrogen on dry-matter intake and nitrogen intake were 88·7% and 0·46 g/100 g dry-matter intake. The analyses on the breeds suggested that the Zebu cattle may have a higher true digestibility and a lower metabolic faecal nitrogen than the British cattle, although the differences were small and could not be subjected to statistical tests.

Soya beans grown on land planted the previous year with inoculated soya beans produced more nodules, lodging, seed yield, 1000 seed weight, and protein content and less seed oil concentration as compared to those grown on land that was planted with non-inoculated soya beans. Nitrogen fertilization (120kg N/ha) reduced the total number of nodules per plant. Increasing inoculation rates of the seed increased the dry weight of nodules per plant. Location, nitrogen fertilization, and inoculation increased or decreased the levels of certain amino acids but had no significant effect on the sulphur amino acids, cystine and methionine.

Six fertilizer–nitrogen sources, each at three levels, together with a control of no fertilizer–nitrogen were compared in field trials in two consecutive crop seasons on a sandy soil comparatively deficient in nitrogen at Patna, Bihar. Four mathematical models were fitted to the potato yield data in order to evaluate the relative availability indices of the individual fertilizers. Data collected on final stand and ‘emergence rate’ index (Bartlett) showed that while urea applications gave rise to a comparatively low speed of emergence, with observed shoot injuries, nitrate of soda caused poor final stands. The other fertilizers had no effect on either the final stand or the speed of emergence.

Sulphate of ammonia was chosen as the standard fertilizer for the present study. Ammonium sulphate nitrate was as good as or even slightly better, while ammonium chloride and calcium ammonium nitrate were of intermediate efficiency, in that order. Urea and nitrate of soda were decidedly poor as nitrogen sources for potatoes under the conditions of the study. The concurrent Mitscherlich curves model was found to represent the behaviour of these fertilizers with a good measure of fit.

The performance of the six fertilizers is discussed in the light of the availability of NH4+ and NO3-, the phytotoxicity of urea and nitrate of soda, and the harmful effects of Cl-. It is concluded that ammonium sulphate nitrate is the best carrier of nitrogen among those studied for potatoes under the conditions set forth.

A hand injector was used to inject ammonia into soils in pots in which ryegrass was subsequently grown and under grass in the field; the spacing was varied.

Injecting ammonia or applying ammonium nitrate at one point or three points in the middle of a clay-loam and a sandy-loam soil in pots did not affect the growth of grass or its uptake of N. Grass with ammonium nitrate grew slightly better than with ammonia on the sandy loam and slightly worse on the clay loam.

Best yields of dry matter and most uptake of N were obtained from grass swards having ammonia injected in lines 23 and 30 cm apart and the injection points from onequarter to one-half of the distance between rows. Increasing the distance between lines from 30 to 45 cm diminished total yield and uptake because the strip 15·2 to 22·8 cm from the line of injection grew less than grass nearer to the line of injection.

With grass grown in rows 12·1 cm apart, yields were greatest with the lines of injection perpendicular to the rows of grass and least with the ammonia injected along and into the rows. The yield of dry matter of the row with ammonia injected into it was usually less than of the adjacent row and the percentage N in the grass was usually more, so that the weight of N in the grass sometimes increased and sometimes decreased with distance from the line of injection depending on the relative changes in yield of dry matter and of percentage N.

Milk yields determined by a lamb-suckling and an oxytocin technique were compared using a control group of four ewes. Both methods showed a similar linear decrease in yield with advancing lactation, but the oxytocin method gave 23% more milk presumably because residual milk was included.

When the diet of lactating ewes was changed so that the amounts of hay and commercial concentrates were reduced in favour of flaked maize, such severe acidosis developed when 39·5% of this food was introduced abruptly or 53% more gradually over one week, that the trials were discontinued.

Rolled barley, which probably ferments more slowly, was therefore used instead of flaked maize. Levels up to 62·9%, gradually introduced over a period of 3 weeks, also produced acidosis whose severity varied greatly in individual ewes.

Milk yield was also determined by the oxytocin technique for ewes receiving normal diets followed by those rich in rolled barley, and the milk was analysed for fat, protein and lactose. The composition of the milk was extremely variable during rolled barley feeding, but there was an indication of an increase in the percentage of crude protein and also fat, after a marked fall in the latter in the milk of two ewes with the change to the low-fibre diet.

Diet had little effect on yields of milk and its components but, on the rolled barley diets, the rate of decrease of these yields was arrested (or even reversed in the case of fat), with a high degree of significance (milk yield P < 0·05, fat yield P < 0·01, protein yield P < 0·01). These observations are discussed, in the light of knowledge on the effect of diet on molar proportions of volatile fatty acids in the rumen.

The effects of seed size and spacing on growth, development and yield of lesser yam and the relationship between growth, development and yield in this yam variety were investigated in the 1967 and 1968 growing seasons. Larger seeds outyielded smaller ones both in the total and ware tuber yields. The seed size effect was associated with a difference in tuber number, leaf area duration and bulking rate. Mean tuber weight at harvest, decreased with the decrease in seed size. Total and ware tuber yields increased with the decrease in spacing distance. The spacing effect was associated with differences in leaf area duration and bulking rate per unit area. Final total dry matter produced per plant increased with the increase in both seed size and spacing distance but the dry matter produced per unit area decreased with the increase in spacing distance. Leaf area index and leaf area duration increased with an increase in seed size and decreased with increase in spacing distance. There was a greater positive relationship between total tuber yield and leaf area duration between tuber initiation and the final sampling period than that between it and absolute leaf area duration.

Live weights of 8764 calves born in seven herds in Cuba during the years 1966–8 were measured at birth and at approximately 3 months of age. Over 2600 were pure bred: Zebu (2002), Santa Gertrudis (435) and Charolais (212); the remainder were crossbred Holstein x Zebu (4955) and Brown Swiss x Zebu (1160).

Year, season of birth, herd and sex were associated with variation in mean birth weight in all breeds and crosses except Charolais in which no seasonal effect was apparent and in Brown Swiss x Zebu cross-breeds in which herd and sex effects were absent.

At 90 days there was a general tendency for calves born in late spring and summer to be heavier than those bom at other times. By this age, herd variation had subsided among Brown Swiss x Zebu cross-breds, and variation due to sex had ceased to be important among Charolais calves.

Estimates of heritability of birth weight ranged from 0·09 in Holstein crosses to 0·62 in Brown Swiss crosses, and of weight at 90 days from 0·05 in Brown Swiss crosses to 0·44 in the Charolais breed. Phenotypic correlations between birth and 90 days weights were of the order of + 0·25 while genetic correlations were positive for pure breeds and negative for cross-breeds.

During the period 1968–71, 417 ewes of various breeds were radiographed for pregnancy diagnosis during the period 60–95 days of gestation.

Pregnancy per se was diagnosed by observing the presence or absence of a definite uterine outline with accuracies of 77, 97 and 100% of the period 60–70, 71–80 and 81 + days of gestation. During the periods 60–70, 71–80, 81–90 and 91 + days of gestation foetal numbers were diagnosed with an accuracy of 88, 94, 99 and 99 % respectively. Breed, size of ewe and number of foetuses carried did not affect the accuracy of diagnosis.

Two fistulated rams were infused through the rumen cannulae with acetic acid or sodium acetate for 4 consecutive days. This infusion has caused a significant drop in the daily feed intake and in the concentrations of rumen ciliate protozoa. The holotrich protozoa were the most susceptible, whereas entodinia were the least sensitive, to the reducing effect of acetic acid or sodium acetate. Decreasing the daily feed intake by 30% has caused little or no change in the concentrations of rumen ciliate protozoa. The in vitro incubation of sodium acetate and rumen contents has resulted in a remarkable depression in the protozoal numbers. Most of this decrease occurred after 5 h of incubation. The addition of acetic acid or sodium acetate to washed suspensions of mixed populations of rumen ciliate protozoa has decreased the in vitro volatile fatty acid production. It is suggested that both the low pH and acetate, ion were responsible for the reduction in the protozoal numbers in the rumen of rams infused with acetic acid or sodium acetate. The effect of acetate on the ciliate protozoa could be an explanation of the diurnal changes in the concentrations of various protozoal groups usually observed in the rumen of the host animal.

Groups of mature Merino ewes selected on the basis of either large or small bodysize were differentially fed during a pre-experimental period to produce subgroups of high and low body condition. These levels of body condition were maintained for 2 weeks before mating and for the first 5 weeks of gestation. Thereafter, the four subgroups grazed together until lambing.

Big ewes had more multiple ovulations than small ewes (14/41 υ 6/53; P < 0·01), and there was a significant linear regression of ovulation rate on body size. Body condition was positively related to the incidence of multiple ovulations, but the regression of ovulation rate on body condition at mating failed to reach significance. Body weight was significantly related to both ovulation rate and the incidence of multiple ovulations, and proved to be a more effective predictor of ovulation rate than either body size or condition.

These results make it clear that size and condition, the two components of body weight, each have a considerable independent influence on some aspects of reproduction, and that the precision of some experiments and the effectiveness of some production routines could be improved by considering them separately.

Two inbred diploid lines of Secale cereale L. and their derived tetraploids were grown together with a commercial diploid and tetraploid in all possible pair combinations in a pot experiment. Comparisons between lines and varieties were made in respect to dry weight measured at 30 weeks.

The competitive effects within mixtures were not compensatory, the commercial varieties tending to increase in dry weight more than the homozygous inbred lines decreased. This gave rise to mixture means which tended to exceed their mid-constituent values.

The analysis of reciprocal differences in dry weight showed that the effects of competition between any one genotype and its associate in mixtures were constant (alpha competition), the sign and magnitude of the alpha effect being related to the pure stand values of the genotype.

The mean effect of competition was to increase the difference in dry weight between genotypes by 2·108 g for each gram by which the genotypes differed when grown alone. In each case the values for genotypes with the higher dry weight increased in mixture whereas the values for those with lower dry weights decreased.

Not surprisingly, the commercial varieties were found to be better competitors than the inbred lines, but of more interest was the ineffectiveness of chromosome doubling on competitive ability. Under the conditions of density and fertility reported here, the tetraploid inbred lines could not be distinguished from their diploid progenitors either in their competitive ability or in their reaction to increased density when grown in mixtures. The same is true for the tetraploid and diploid commercial varieties.

Three hundred and seventy-six isolates, or about 9% of the cultures collected in 1967 and 1968 from soil of permanent pasture, that, prior to 1883, supported mixed conifer and deciduous forest, were cultivated in the laboratory. Antibiotic production was detected in 27% of the cultures. Similarly, 329 isolates, or 9% of those collected in the same period from soil of permanent pasture reclaimed from tidal marsh, were grown in the laboratory and antibiotics detected in 30%. The forest soil, because it was already known to have a denser fungal population, thus had a greater antibiotic production potential than the marshland soil. There was a small increase in the number of isolates from the forest soil that produced antibiotics when those obtained in the spring were compared to those collected in the autumn. The opposite relationship was found when the marshland isolates from the two seasons were similarly compared. The results are consistent with the hypothesis that the fungal populations of these soils are a parameter in the aetiology of the ill-thrift that is found in ruminants at Nappan, Nova Scotia.

The amino acid composition of barley grain was studied during the maturation of the grain and during germination of the mature grain. Samples of the variety Proctor, grown at two nitrogen levels in each of the years 1969 and 1970, were analysed together with one sample of Sultan grown in 1970. It was found that during maturation the proportions of glutamic acid and proline increased and that the levels of these amino acids were highest in those samples with the highest total protein content. During ripening the proportions of lysine, alanine, aspartic acid, threonine and glycine decreased. On germination the proportions of glutamic acid and proline rapidly decreased whilst aspartic acid, lysine, alanine and glycine increased.

The nutritive value of ripe barley grain is limited by its low lysine content. Whilst the germination process increases the level of lysine it is suggested that this does not increase the nutritional value of the grain due to the low level of cystine in the germinated grain.

A total number of 5949 birth records collected over a period of 9 years from a crossbreeding experiment at Sakha Animal Research Station were used in this study. The following breeding groups were included: Fleisch Merino (M), native Ossimi (0) and Barki (B) breeds, MO, MB, ¾M ¼ O, ¾ M ¾ B and the inter se mating groups of the backcrosses (’¾ M ¼O’ and ‘¾ M ¼B’). Productive traits studied were birth, 4-month and yearling weight, lamb liveability at 4 months of age; and first fleece weight (at 10 months of age).

Generally, the cross-bred lambs were heavier in body weights and sheared more wool than the pure breds, with the differences being almost significant. In liveability, native breeds showed significantly higher estimates than the cross-breds where the Merino breed was the poorest in this respect.

Merino × Ossimi first cross was the best breed group showing a high heterosis estimate of 0·9, 5·2, 10·3, 7·6, 0·9 and 0·7 kg in birth, 4-month, yearling males and females body weights and first fleece weight, respectively. They were followed by ¾ M ¼ O with a corresponding heterosis value of 0·8, 3·9, 7·4, 4·2, 0·5 and 0·5 kg respectively. Merino x Barki and their backcrosses to Merino are ranked second to the Ossimi crosses. Heterosis in the Barki backcross was 0·8, 2·9, 4·8, 2·1, 0·4 and 0·4 kg compared with 0·5, 2·5, 3·1, 2·7, 0·5, 0·4 kg for MB, on different traits, respectively. The interbreeding of the backcrosses caused a diminishing in hybrid vigour. Heterosis estimates in ‘¾ M ¼ O’ were 0·3, 0·9, 4·6, 2·3, 0·3 and 0·3 kg, whereas it was 0·1, 0·3, –0·1, –0·3, 0·0 and 0·1 kg for ‘¾ M ¼B’, in different traits respectively. All cross-breds showed negligible or/and negative heterosis in lamb liveability up to 4 months.

The effects of breed group, year of birth, age of dam, sex and type of birth were found to be highly significant on all traits except the effect of type of birth on lamb liveability.

A detailed study was made of the tillering of barley plants grown at densities which ranged from 50 to 1600 plants m–2. Throughout the season the initiation of tiller buds and their growth in length and leaf number were followed, and measurements were made of leaf sheath and lamina length and lamina width. A proportion of tillers died and their positions and times of death are given.

Three phases of tillering were recognized. The first, tiller bud initiation, was little affected directly by density. During the second phase, buds did not grow or did grow and emerge from the subtending leaf sheath. If they grew, there was no difference in growth rate of tillers at different densities. At the higher densities fewer buds developed, and the morphology of those tillers which did grow was affected by density. This suggests that the growth of the tiller bud may be controlled by levels of endogenous gibberellin, while in the final stage, growth after emergence from the subtending leaf sheath, competition for light appears to be the factor which determines whether a tiller survives to produce an ear. The data are discussed in relation to the practical importance of tillering.

Four experiments are described in which the response of sugar beet to irrigation was measured over a range of approximately 30000–150000 plants per hectare, and one experiment where the effects of plant population and spatial arrangement were studied. The experiments were carried out on a sandy soil in the south-east of England and extended from 1960 to 1965. The response of sugar beet to irrigation was affected by plant density. It is suggested that some explanation for the modified responses may be provided by considering effects of plant population on (i) the rate at which the soil surface is covered by leaves, and (ii) effects on the volume of soil exploited for water.

The balance between heat production and heat loss and the partition of heat exchanges of cattle in relation to air humidity has been studied at two different air temperatures using a direct (gradient-layer) calorimeter.

Increasing humidity at 35 °C air temperature caused no significant change in heat production or in the level of total heat loss finally attained, but body temperature and respiratory activity were both increased.

Increasing humidity at 15 °C air temperature caused a small reduction in heat loss by evaporation but had no effect on sensible heat loss, body temperature or respiratory frequency.

Heat loss by evaporation amounted to 18% of the total heat loss at 15 °C and to 84% at 35 °C.

Heat loss by respiratory evaporation amounted to 54% of the total evaporative heat loss at 15 °C and to 38% at 35 °C.

Maize or lucerne silages were fed to two groups of cows in a large dairy herd. Metabolic profile tests carried out during the trial showed that abnormal blood chemistry such as might lead to production disease did not occur in either group.

The results of feed analysis and digestibility trials showed that the two silages provided equal quantities of digestible energy but that the lucerne silage provided more digestible protein than the maize silage. Blood glucose concentrations were similar in both groups of cows but serum urea and albumin concentrations were significantly higher in the cows fed lucerne silage than in those fed maize silage. There was also evidence that lucerne silage provided slightly less available phosphorus but more calcium than the maize silage.

It is concluded that maize silage, as used in these experiments, showed no tendency to lead to production disease, and furthermore the metabolic profile test provided additional information to feed analysis in making this assessment.

Two experiments carried out in 1968 and 1969 are described which examined, through growth and yield analysis, the effect of nitrogen on the growth of oilseed rape. The results of the second experiment, when 0, 105·5 and 211·0 kg N/ha were compared, are presented and discussed. The application of nitrogen increased the yields of seed and oil, principally through increased production of seeds by a larger number of pods. However, the application of nitrogen had little effect on average pod weight or average seed weight. Crop growth rates were increased by the application of nitrogen and reached their highest levels during the period of pod development when the leaf areas had declined to very low levels. The order of effects of nitrogen (N 2 > Nl > NO) was similar for LAI, number of pods per plant and number of seeds per pod and it is likely that the effect of nitrogen was achieved indirectly through an increase in the supply of assimilates to the flowers and young pods. This suggests that the maintenance of a large and photosynthetically efficient leaf area during the period of flowering is necessary for high yields in this crop.

The results also suggest that once pods are macroscopic they produce much of the assimilates needed for their own growth.

The implications of these findings with regard to both practice and further research are discussed.

The phenological development from sowing to flowering of the eaxly maize hybrid INRA 200 is related to the weather conditions. Plot trial data from Wytham, near Oxford, England, and weather information from that and nearby sites formed the basic data.

The mean rate of development per day from sowing to emergence is related by linear correlation analysis to the mean values of soil temperature at 5 cm depth and soil moisture deficit. A range of temperature thresholds for emergence development exist, which depend upon the soil moisture, and which differ from the true physiological threshold.

Between omergence and flowering the mean rate of development per day is related by linear correlation analysis to mean air temperature, solar radiation and potential transpiration estimated from weather data. All correlations are significant, but the parameters which combine radiation and temperature are statistically better.