Sheep prepared either with a rumen cannula, or with a rumen cannula plus re-entrant cannulae in the duodenum and ileum were fed fresh ‘Ruanui’ perennial ryegrass (R), ‘Manawa’ short rotation ryegrass (M) and white clover (C) at dry-matter intakes ranging from 450 to 1000 g/24 h. Paper impregnated with chromic oxide was given once daily via the rumen fistula as a marker.

Amounts of non-ammonia-nitrogen (NAN) entering and leaving the small intestine and nitrogen (N) excreted in the faeces were regressed against the intake of N for each sheep and these equations (all significant P < 0·05) were used to calculate the extent of digestion in the stomach, the small intestine and the large intestine at two levels of OM intake (500 and 800 g daily). Amino acid analyses of feed and digesta samples are also presented together with calculations of the apparent absorptions of individual amino acids from the small intestine.

At an intake of 500 g OM amounts of NAN entering the small intestine were significantly greater (P < 0·05) in sheep given M than in sheep given R or C. At an intake of 800 g OM amounts in sheep given M were significantly greater (P < 0·01) than in sheep given R. NAN leaving the small intestine and N excreted in the faeces were similar for all three diets.

At an intake of 800 g OM apparent absorptions of NAN from the small intestine of sheep given M (0·47 × N intake + 2·8 g/24 h) and sheep given C (0·51 × N intake – 1·3 g/24 h) were significantly greater (P < 0·01 and P < 0·05 respectively) than of sheep given R (0·41 × N intake – 0·5 g/24 h). As intake of herbage was increased the partition of digestion altered.

Only small differences between herbages were found in the amino acid composition (g amino acid/100 g protein) of either duodenal or ileal digesta, but because of the large differences in the flows of NAN, the apparent absorptions of individual amino acids from the small intestine were much higher in sheep given M than in sheep given the other two species.

The results are discussed in the light of available information on sites of digestion of herbage diets in sheep.

Blood samples, taken from each of 231 calves on three occasions at 9,10 and 11 weeks of age, were analysed for packed cell volume, blood glucose and Hb; and serum albumin, urea nitrogen, total protein, Ca, inorganic phosphate, Mg, K, Na and Cu. Differences in the blood composition for individual calves were demonstrated for all blood constituents (P < 0·01) with variations among calves proportionally largest for albumin and smallest for sodium. Concentrations of glucose, Hb and K were inherited (heritability estimates > 0·4).

There were significant correlations (P < 0·001) between the calves' growth rates from 1 to 12 weeks and the concentrations of each of the blood constituents, glucose Hb, K, Na, albumin and inorganic phosphate; in the cases of Na and albumin, comparison of the blood analysis at 9–11 weeks with body weights at 6 and 9 months showed that these correlations persisted, and that by 9 months differences in concentrations of Na and albumin among individuals were associated with an average difference of as much as 55 kg in body weight.

The evidence that concentrations of certain blood constituents are both inherited and related to growth rate suggests that not only might calves be screened early in life for indications of rapid growth rate, but also that animals might be bred to have the blood characteristics indicative of this quality.

The growth and development of two semi-dwarf winter wheat varieties, of two taller varieties, and of random selections from two crosses between semi-dwarf and taller varieties were compared over 2 years. Changes with time of crop dry weight/m2, leaf area index and ear size were expressed as orthogonal polynomial regression coefficients. Significant correlations were obtained between yield, the polynomial coefficients and growth measurements relating to number of tillers and flag leaf area duration, but many of these variables were significantly correlated with each other. Multiple regression equations were therefore calculated expressing yield in terms of the variables. These showed flag leaf area duration and rate of ear growth to be the most important characters determining crop yield. The greatest reduction in total yield variance was obtained by the simultaneous consideration of characters relating to photosynthetic capacity and ear development. The significance of this finding in relation to the relative importance of ‘apos;source’ and ‘sink’ in determining grain yield are discussed.

The largest yields of potatoes in the Woburn Reference Experiment were obtained by giving both farmyard manure (FYM) and fertilizers, rather than fertilizers alone; an explanation was sought in experiments made on the coarse sandy loam there from 1968–71. Each year, single and double amounts of NPK fertilizer (supplying 250 or 500 kg N/ha plus P and K) were incorporated, either deeply or shallowly, into the seed bed. From 1969, FYM also was tested at rates giving the same amounts of N, similar amounts of K, but more P than the fertilizers; it was tested both alone and with fertilizers.

FYM was less effective than fertilizer when given alone. The combination of FYM and fertilizer gave a larger yield than the single amount of fertilizer and a larger yield than the double amount of fertilizer incorporated shallowly, but a smaller yield than the double amount of fertilizer incorporated deeply, which gave the largest yield each year.

The NPK contents of the potato tubers were used to construct nutrient balance sheets; large residues of N, P and K remained in the soil after harvest. Winter wheat was grown to value these in 1971 and 1972. Fertilizer residues increased only straw yields, but FYM residues increased yields of both grain and straw. Both kinds of residues were less effective than freshly applied N, so most of the N leached during winter.

The yield of saleable tubers was increased, not decreased, by the double amount of fertilizer.

Sheep prepared either with a rumen cannula, or with a rumen cannula plus re-entrant cannulae in the duodenum and ileum were fed fresh ‘Ruanui’ perennial ryegrass (R), ‘Manawa’ short-rotation ryegrass (M) and white clover (C) at dry-matter intakes ranging from 450 to 1000 g/24 h. Paper impregnated with chromic oxide was given once daily via the rumen fistula as a marker.

Amounts of Mg, Ca, P, K and Na entering and leaving the small intestine and excreted in the faeces were regressed against the intake of each element for each sheep and these equations (all, other than the faecal excretion of Na, significant (P < 0·05)) were used to calculate the extent of apparent absorption or secretion in the stomach, the small intestine and the large intestine at two levels of OM intake (500 and 800 g daily).

Quantities of Mg (at high intake), Ca and K (except sheep fed M) leaving the stomach were significantly lower (P < 0·05), while the amounts of P and Na were significantly higher (P < 0·01) than the amounts consumed. Quantities of Mg (at high intakes) and Ca leaving the small intestine were significantly higher (P < 0·05) while amounts of P, K and Na (at high intakes) were significantly lower (P < 0·05) than the corresponding quantities entering the small intestine. At both intakes in the case of Na and at the higher intakes in the case of the other mineral elements, quantities of Mg, Ca (except sheep fed C), P, K and Na excreted in the faeces were significantly less (P < 0·05) than the amounts entering the large intestine.

Thus at the higher intakes there were net absorptions of Mg, Ca and K (except sheep fed M) from, and net secretions of P and Na into, the stomach. The small intestine was the major site of net absorption for P and K and a minor site for Na, while a net secretion of Mg and Ca occurred into this region. Net absorption of Mg, Ca, P, K and Na occurred from the large intestine at the higher intakes.

The retention of Mg, Ca and P is discussed in relation to the animals' minimal daily requirements of these elements.

Three factorial experiments made in 1969 on Northern Ireland pastures to measure effects upon yield and mineral content of 0, 180 and 360 kg N, 0, 30 or 60 kg P and 0, 150 or 300 kg K/ha/year, both with and without 1380001 slurry/ha, were continued on the same sites with the same treatments in 1970 and two of them were continued again in 1971.

Responses to nitrogen in the second and third seasons were similar to those of the first season. There was no evidence that large nitrogen dressings plus slurry were causing nitrogen to accumulate in the soil.

Repeated cutting of herbage given neither fertilizer potassium nor slurry was beginning to reduce both yield and the potassium content of the herbage in the second and third years. Giving fertilizer potassium prevented these losses, but the potassium in the slurries was less effective because it did not maintain the potassium content of the herbage. Reasons for, and implications of this effect are discussed.

There was no evidence that soil phosphorus reserves were becoming depleted, when judged by the % P in herbage receiving neither fertilizer nor slurry even after the herbage had been cut and removed for two or three years. As there was no immediate need for fertilizer phosphorus, the P in the slurries, even though slower acting than that in mineral fertilizers, seemed suitable for maintaining the phosphorus status of these pasture soils.

This article attempts to discuss the relations between the nitrogen sources in data from a large field experiment in which various levels of fertilizer nitrogen were applied to various grass mixtures in the presence and absence of white clover. It was seen that a number of effects occurred, among them the strong depression of clover nitrogen by fertilizer nitrogen (to the extent that equations predicting their contribution to grass nitrogen could not be produced directly by multiple regression but had to be constructed separately), a further apparent depression of clover nitrogen transfer effectiveness, a more significant relationship between grass nitrogen increase and the previous year's clover nitrogen than the current year's clover nitrogen, and apparent competition between grass and clover despite the latter's contribution to increased grass yield.

As some of the effects are counteractive, in each comparison made a balance appears to exist. This varies between sites and years in such a way that although the variation in grass nitrogen is always largely dependent on the clover and fertilizer nitrogen the relations are not consistent as shown by the mathematical equation representing them, and cannot be extrapolated or predicted for other sites. It is suggested that a mathematical model be constructed to simulate such an interactive system and that predictions when necessary be made using this, rather than using simple equations.

A series of stocking rate trials running for differing periods between 1961 and 1972 are summarized. Weight gains of steers grazed at 2·4, 1·2, 0·8 and 0·6 ha/300 kg animal on Cymbopogon/Hyparrhenia/Themeda pasture are detailed. Subtreatments included continuous and rotational grazing and the removal of the unpalatable Cymbopogon afronardus.

Weight gains at 0·6 ha/animal were higher than a linear relationship between stocking rate expressed as animals/ha and weight gain would predict. This was ascribed to the dominance of the high quality grass Brachiaria decumbens at this grazing pressure.

Rotational grazing was less productive than continuous grazing, because C. afronardus increased more rapidly under this management, but there was less soil erosion. Removal of C. afronardus increased cattle growth rates and gains/ha by over 40% at 0·6 ha/animal. The cost of clearing this weed should be recovered in 2 years from a commercial cattle ranch. A grazing pressure of ca. 0·8 ha/animal is expected to maximize long-term profits on C. afronardus-free Ankole rangeland and in 3 years in this trial average gains of 0·29 kg/day/animal were achieved. This was an annual production level of 131 kg/ha/annum, which compared with 53 kg/ha at 2·4 ha/animal and 143 kg/ha at 0·6 ha/animal.

Leaf burn and gradual death were the characteristic symptoms of injury in P. vulgaris sown on a sodic soil. Plant growth, total leaf area per plant, number of stomata and epidermal cells per unit leaf area, and relative water content were drastically reduced in injured plants; these were associated with large sodium accumulation in the shoot resulting in cation imbalance.

Botanical analyses of trials grazed at 3·6, 2·4, 1·2, 0·8 and 0·6 ha/300 kg animal for 4 years are detailed. The two heaviest grazing pressures encouraged Brachiaria decumbens, a high quality grass, at the expense of Themeda triandra and Hyparrhenia filipendula. Rotational grazing allowed the weed grass Cymbopogon afronardus to regenerate after clearing more rapidly than did continuous grazing.

Bullocks with oesophageal fistulas sampled pastures grazed at 2·4, 1·2 and 0·6 ha/animal at 4-weekly intervals for 12 months. The 0·6 ha/animal treatment was repeated on pasture cleared of the weed grass Cymbopogon afronardus. Cattle growth rates, both long term and at the time of sampling, were recorded.

Cattle growth rates were greatest at 2·4 ha/animal but fistula sampling demonstrated that the diet was significantly lower in CP and higher in CF than the more heavily stocked treatments, which is contrary to the normal pattern. It is concluded that the differences in cattle growth rates at the different stocking rates were due to differences in dry-matter intake rather than the recorded differences in diet quality. The higher CP in the diet at the heavier stocking rates is ascribed to the increase of B. decumbens in the diet.

An unexplained ceiling to cattle growth rates of ca. 0·5 kg/day, and a calculated drymatter intake of < 2·1% body weight/day, in the presence of unlimited forage of 10% CP and 55% apparent digestibility, makes it more economic to stock for maximum production per ha than per animal.

Observations on the time of development of the permanent anterior teeth in a herd of Friesian female cattle (heifers + cows) are described. The animals were examined at approximately monthly intervals. A modified longitudinal survey method was employed. A table is presented of the maximum and minimum (i.e. the range), mean and median ages for the stages of development for each permanent pair of teeth. The stages were defined as: one of permanent pair present and/or one/both temporary teeth absent, both permanent teeth emerging, ¼ up, ½ up, ¾ up and fully up. A large amount of variation was found in the ages for each stage of development in individual animals. Tables are included for the time taken for a pair of permanent teeth to pass from first to complete emergence, the time a pair of teeth were fully up before any further development was observed and the time taken between a tooth being at one stage in one pair of teeth to the same stage in the succeeding pair of teeth.

Field experiments were conducted on clay and sandy clay-loam soils to investigate the effects of sowing date on the incidence of plant losses. Early sowing dates from 2 to 23 September resulted in very low seed yield (360 kg/ha) mainly because fewer plants survived. High air temperature increased the rate of plant death which was highly correlated with degree days, r = +0·95.

Number of plants/m2 was the predominant factor determining seed yield and number of pods/plant could not compensate for loss of plants.

Samples of monogerm sugar-beet seed which had been cleaned but not processed, contained fruits weighing 2–27 mg and true seeds weighing 0·2–5·0 mg with seed weight averaging about 20% of fruit weight. Increasing fruit size by round hole sieving resulted in progressively greater percentage emergence. Radiography revealed that one reason for this improvement was that more locules were completely filled, and fewer contained shrivelled seeds or were empty. Commercial processing of one seed lot eliminated some but not all of the empty fruits or those containing poorly developed seeds.

In the field, seedling size and root:shoot ratio increased with increasing seed size. Thus at equivalent plant densities, sugar yields were less from the smallest seed than from other grades because of the combined effects of less total growth and a less efficient partitioning of assimilates. Although improvements in establishment with increasing size grading were progressive, sugar yield at comparable plant densities was greater only from medium grades relative to the smallest grades, whilst yields from large and medium grades were similar. This difference was maintained irrespective of length of growing season or plant density.

Three experiments studied the behaviour of pigs which were brought together for brief periods of observation on successive days. Two distinct patterns of aggressive behaviour were observed, one involving biting and the other involving butting. Biting was common when the pigs first met, and butting seemed to replace biting in some cases. Pairs of pigs which had no previous contact frequently showed a straight forward type of dominance with one pig performing almost all the biting and butting; among well-acquainted pairs, however, the relationships were frequently more complex.

Of all the experimental manipulations, familiarity between two animals had the most profound effect on the behaviour. Biting, but not butting, was reduced if the pigs were housed in neighbouring pens, or if they had previously shared the same pen. Biting was almost eliminated, and butting was reduced, if the pigs lived together throughout the time of the observations. There were no differences between females and castrated males, or between individually-housed and group-housed animals in either type of behaviour.

Pigs which were subjected to repeated biting generally became less active, refraining from some social and non-social activities. Butting did not appear to have similar effects on the recipient animals.

The experiments illustrated some complex social interactions involving a large number of distinct social activities. In this light, the usefulness of such broad terms as ‘aggression’ and ‘dominance’ is discussed.

Body weights at birth, weaning, yearling and 2 years of age were studied on 710 lambs born from 1956 to 1967 and representing Barki, Merino and their F1 and backcross. Body weights ofthe lambs of the two cross-bred groups were intermediate between those of the two pure-breds at birth and exceeded them at weaning. Merino lambs were 0·61 kg heavier than Barki lambs at birth and maintained that advantage throughout the study.

Age of dam, type of birth, sex, and year of birth were significant sources of variation on the weights studied. The effect of age of dam and type of birth declined after weaning while that of sex increased.

When one or two leaves were removed out of the three or sometimes four present on each tiller of five genotypes of perennial ryegrass grown in nutrient solution, it was found that the relative growth rate (RGR) was not much less than that of untreated plants. The removal of lower leaves had no effect on RGR. Removal of all leaf blades depressed RGR. It is suggested that the results obtained indicate that the plant has the capacity to compensate for loss of leaf tissue by increased activity in the remaining leaves. Leaf appearance rate and tiller production were found to be the attributes most sensitive to the defoliation treatments imposed, and the degree to which leaf appearance rates were affected by defoliation was found to be a good indicator of the regrowth capacity of the different genotypes. Evidence was obtained linking high regrowth potential with high relative increases in the proportion of plant material allocated to new shoot growth.

Fourth and fifth generation inbred lines of horse and tick spring beans were used for pollination studies.

Treatments included tripping; emasculation followed by self- or cross-pollination at both the bud and mature flower stage; self-pollen rubbed on to the stigma; and the flower truss left undisturbed. Treatment means showed that there was no significant difference between leaving the flower truss undisturbed and tripping, but all other treatments differed significantly (P = 0·01) from these two. There was no difference in number of seeds set per flower between self- or cross-pollination following emasculation.

Tick inbred lines set more seeds per flower over all treatments than horse inbreds. Differences were seen between tick and horse inbreds when the flower truss was left undisturbed; some tick inbreds set seed, but no seed was set on the horse inbreds. An association between seed size and autofertility is suggested.

Results from the horse inbreds were in agreement with previous pollination studies on inbred lines of winter beans. The implications of these studies to plant breeding are discussed.

The relationships between mid-silking date, mid-maturity date, spread of silking and spread of maturity were studied in four maize hybrids. Mid-maturity date and spread of maturity were positively related to mid-silking date. The spread of silking ranged from 13 to 18 days and the spread of maturity from 34 to 47 days in different hybrids. Grain moisture content at mid-maturity ranged from 40 to 35%. It was concluded that the common practice of harvesting grain crops at 40% dry matter is likely to result in appreciable loss of yield: variation in the proportion of mature kernels when the grain has reached 40% moisture may account for the large season to season variation in yield observed in commercial crops. The potential benefits of early flowering hybrids are briefly discussed.

A study was made of the effect on body composition of growing Angus steers from 300 to 440 kg at three different rates. The rates were: High (H) 0·8 kg/day, Low (L) 0·4 kg/day and High-Maintenance (HM) 0·8 kg/day followed by a period during which body weight was maintained constant.

The animals were individually penned and the different growth rates were achieved by controlling intakes of a pelleted feed. Two animals (part of H treatment) were killed at 300 kg and the remaining 27 animals (nine in each treatment), were killed at common body weights of 330, 363, 400 and 440 kg.

Analyses of covariance were used to compare linear regression equations representing results from each treatment. In order to do this, the logarithmic transformation of the allometric equation, y = axb, was used. As a proportion of empty body weight (EBW), hot carcass weight (HCW) was greater in both the HM and L groups than in the H group, indicating a greater offal component of EBW in the H animals. The loss in weight of the dressed carcass during storage at 2 °C for 24 h was similar in all three groups and was 0·98% of HCW. The proportions of HCW in the fore- and hind-quarters were similar in each group.

At the same dissected side weight (DSW), the weight of bone was significantly greater in both the HM and L groups than in the H group indicating that bone development was related to both age and carcass weight. There were no significant differences between the groups in the proportions of either muscle or total fat. However, the proportion of kidney and channel fat in the H group was greater than in the HM and L groups and the proportion of subcutaneous fat was also greater in the H than in the L group. The amount of connective tissue in the three groups followed, in general, group differences in bone. Analyses of the dissected components of the separate fore- and hind-quarters showed that the difference between the H and L groups in the proportion of subcutaneous fat in the DSW was due to a relatively greater development of this fat in the fore-quarter of the H animals.

No differences were found between treatments in the proportion of ‘expensive muscles’ relative to total side muscle (TSM). However, there were treatment effects on the proportions of TSM formed by certain groups of muscles; two examples are: the proportion of group 4 muscles (abdominal muscles) was higher and the proportion of group 6 muscles (distal muscles of the fore-leg) was lower in the H than in the L treatments. Bone weight distribution was similar in all treatments.

There were differences between the H and HM groups in the relative growth ratios for all fat tissues (subcutaneous, intermuscular and kidney and channel fat) compared with total side fat. However, in the H and L groups, the relative growth ratios for corresponding fat categories were similar. The weight of kidney and channel fat in the left side of the carcass was significantly greater than in the right side of the carcass in all treatments.

As an indication of heritable variation between genotypes, the response of diploid and autotetraploid homozygous inbred lines of rye to varying applications of inorganic nutrients and to temperature ‘shocks’ during growth was studied. The results indicated first that developmental differences occur between lines and between diploids and tetraploids under comparable conditions of growth. Secondly, the consequences of altering growing conditions can differ between lines and between diploids and tetraploids. Thirdly, the effect of polyploidy upon the response to these treatments was shown to vary between lines. It is concluded that an assessment of plant growth and development must take into consideration the genie, chromosomal and environmental interactions.