Herbage availability, intake and nutritive value were recorded on swards of S. 59 red fescue (Festuca rvbra L.) and S. 23 perennial ryegrass (Lolium perenne L.), with and without S. 184 white clover (Trifolium repens L.), and correlated with animal performance. Intake of dry matter was similar on all treatments. Animal live-weight gains during 1969 were positively correlated with digestible organic matter intake (DOMI).

Poor animal performance from red fescue swards in mid-summer was attributed to the rapid fall in digestibility at this time which affected DOMI.

Differences between treatments in efficiency of conversion of DOMI into live-weight gains were observed. Superior conversion ratios in swards containing clover could not be related to any of the herbage quality measurements recorded.

Better animal productivity from red fescue swards in early spring and in late autumn were related to the longer growing season of this grass.

The merits and demerits of red fescue as a grass for hill conditions and the possibility of reducing its limitations by breeding are discussed.

Prenatal mortality was examined in 74 primiparous Merino ewes which, after hand mating to fertile rams on the second oestrus following synchronization, were allocated to two groups. One group of 38 ewes was confined to yards and restricted to approximately 30% of their maintenance requirement for 14 days while the other group of 36 remained at pasture. The degree and timing of prenatal loss was assessed by corpora lutea counts, pregnancy diagnosis about day 40, returns to service and lambing records.

The mean ovulation rate was 1·06 and the 19-day non-return rate was 87·8%. Pregnancy failed in a higher proportion of the underfed ewes (45·0%) than in the control ewes (30·8%) but this difference did not reach significance. Of the ewes returning to service, significantly more did so with cycles longer than 19 days in the underfed group (9/12) than in the control group (2/8), indicating that in the latter stages, the treatment may have been detrimental to embryo survival.

In a second experiment, ovulation rate and prenatal mortality, assessed as in the first experiment, were studied in 85 mature Merino ewes subjected to the following nutritional treatments: HH, control; HL, 30% submaintenance feeding for 14 days following mating; LH, 15% submaintenance feeding for 7 days prior to mating; LL, both submaintenance treatments.

Acute undernutrition prior to mating (LH) had no effect on ovulation rate or prenatal mortality. Ovulation rates were low over all groups (mean 1·09) and thus precluded any valid examination of ovulation rate and body weight relationships. The right ovary was significantly more active in producing ova than the left in all groups (P < 0·05). Although ova wastage was apparently higher in. the post-mating undernutrition groups (HL, 44%; LL, 48%; LH, 50%) than in the control group (HH, 35%), the differences were not significant. An increased incidence of extended (> 19 days) first-return cycle lengths in group LL provided some evidence of induced prenatal mortality.

In so far as the experiments can be considered together, they indicate that if body weights are comparable, primiparous 1½-year-old ewes are not necessarily more susceptible than mature ewes to prenatal mortality induced by severe short-term undernutrition.

Oestrus, ovulation rate and prenatal mortality were studied in 114 mature Merino ewes of high and low body weight at mating. Three nutritional treatments were imposed over 8 weeks prior to hand mating to fertile rams; high plane (HH), low plane (LL) and 7 weeks of high plane followed by 1 week of fasting immediately prior to mating (HL). Ovarian activity, ovulation rate and the extent and timing of prenatal loss were assessed by the appropriate use of direct ovarian observations, pregnancy diagnosis, returns to service and lambing records.

While both prolonged undernutrition (LL) and acute nutritional restriction (HL) were associated with some suppression of behavioural oestrus, neither had any appreciable effect on ovulation rate or prenatal mortality. In all groups the right ovary was more active in producing ova than the left, and the HH group had more ovarian follicles (≥ 4 mm diameter) than the other two groups. Large unruptured ovarian follicles (6—15 mm diameter) were observed in nine ewes. Significantly more ova shed in multiple ovulations were lost, and multiple-ovulating ewes were more likely to suffer complete rather than partial loss of both embryos. Impaired fertility was evident when ewes that returned to service at an extended cycle length were re-mated.

March-born non-cyclic Suffolk × Galway ewe lambs were treated with progestagen pessaries while being either fed fresh-cut grass ad libitum, or restricted to 50% of appetite and at pessary removal half of the animals on each nutritional treatment received either 600 i.u. or 300 i.u. PMS. Averaged over both levels of PMS, 97·5% of the lambs showed oestrus when fed ad libitum but only 67·5% of those on restricted feeding responded. When feed intake was not restricted there were no differences due to PMS level but when feed intake was restricted the higher dose level of PMS resulted in a greater percentage showing oestrus and a significantly higher ovulation rate. The dose level of PMS had no effect on the time of oestrous onset but restricted feeding resulted in delayed onset and poor synchronization of oestrus. Duration of oestrus was greatest for lambs fed ad libitum given 600 i.u. PMS and least for those on restricted feeding given 300 i.u. PMS but the difference was not significant. A minority of lambs showed broken oestrous periods.

Two surveys, involving 288 lambs, were carried out on the effects of system of production on the melting (slip) point, iodine value, and fatty acid composition of perinephric and subcutaneous carcass fat. The systems studied were:

A, early Spring lambs fattened indoors on concentrates;

B, early Spring lambs off grass;

C, early Summer lambs off grass;

D, Autumn lambs off grass, and

E, Winter hoggets.

The melting point of both perinephric and subcutaneous fat increased progressively during the season from mean values of 41 and 32°C respectively in group A to mean values of 48 and 42°C respectively in group E. Discolouration of the surface fat was associated with the low melting points of group A.

Mean iodine values of both fats decreased progressively from group A to group E and this change was associated with a decrease in levels of oleic and palmitoleic acid and a corresponding increase in the level of stearic acid. In the fat, levels of myristic acid were highest in grass fed lambs while levels of linoleic acid were highest in the concentrate-fed lambs.

Within each group, perinephric fat contained more stearic and less oleic, palmitoleic, palmitic and myristic acid than subcutaneous fat.

Within animals, the levels between perinephric and subcutaneous fat of melting point, iodine value and most of the individual fatty acids were highly correlated.

Within animals also, the melting point of perinephric fat was correlated in decreasing order of significance with stearic acid, oleic acid, iodine value, linoleic acid and palmitoleic acid, while melting point of subcutaneous fat was correlated in decreasing order of significance with stearic acid, oleic acid, palmitoleic acid, iodine value, linoleic acid and total branched-chain fatty acids.

Four groups of six store lambs were offered ad libitum a concentrate barley-based diet, supplemented with either 8% casein or 2% urea, each contributing the same level of nitrogen to the diet and each fed with or without a supplement of 5·8% sunflower oil. Daily food intake was significantly affected by treatment but there was no significant treatment effect on live-weight gain or food conversion efficiency. In rumen fluid the casein supplement resulted in more total volatile fatty acids and a greater proportion of valeric acid, while the sunflower oil supplement significantly increased the proportion of propionic acid. Sunflower oil supplementation decreased the melting point of perinephric fat by about 3 °C, associated with an increase in the proportions of palmitoleic, oleic, linoleic and linolenic acids and a decrease in the proportions of palmitic and stearic acids. Sunflower oil resulted in a smaller and nonsignificant decrease in the melting point of subcutaneous fat which was associated with an increase in the proportions of linoleic and linolenic acid and a decrease in the proportion of palmitic acid. Melting point of both fats was not affected by source of dietary nitrogen supplementation but in subcutaneous fat the urea supplement resulted in a small increase in the proportion of oleic acid and a decrease in the proportions of palmitic and palmitoleic acids. The proportions of branched-chain and oddnumbered n-acids in both fats were not affected by treatment.

Soils from long-term experiments at Rothamsted and Woburn were cropped for very long periods (up to 5½ years) with ryegrass in pots. Measurements of the potassium taken up by the ryegrass that was not exchangeable to ammonium acetate and the kinetics of its release both suggested two categories of non-exchangeable K. Of these, the first to be released was closely related to the initial exchangeable K, whilst the second, though partly related to the initial exchangeable K was also influenced by the clay percentage. Release of both categories may have been controlled by diffusion, because both showed good relationships between the quantity released and time. It is suggested that the first category may be K ‘trapped’ when K fertilizer added in the field decreased the interlamellar spaces of vermiculite layers in clay particles, whilst the second may simply be the ‘native’ K (described by others) present in clay and other minerals in the soil.

Resowing the soils (without drying them) during the later stages of K. uptake suggested that the ability of the old ryegrass to absorb K was not a factor limiting K uptake even after long growth.

When the ryegrass ceased to grow, the mean K potentials in the exhausted soils were close to the ‘uptake potential’ for ryegrass derived earlier by considering K uptakes from soils in relation to the quantity/potential relationships of the soils. Drying and rewetting the exhausted soils released K; the amount was influenced in one group of soils by the exchangeable K in the moist exhausted soil and in another group by the clay percentage.

Six herbage samples (ranging from poor quality hill herbages to high quality ryegrass and clover) were analysed for soluble carbohydrate, total and soluble nitrogen (N), cell-wall carbohydrates and in vitro digestibility. Changes during freezing and thawing processes were measured. Invertase activity occurred in all frozen and thawed samples. Although the total N content of all samples remained constant throughout, the soluble-N contents of the four better quality herbages were considerably reduced on freezing and thawing. Cell-wall carbohydrates and in vitro digestibility measurements were unaffected by freezing and thawing.

The sprout inhibitor Chlorpropham (CIPC) [isopropyl N-(3 chlorophenyl) carbamate] was found to be an effective sprout inhibitor in stored swedes (Brassica napus L.) under certain conditions. It was ineffective and unnecessary in swedes stored from November to April but necessary for those stored in clamps from March to July. CIPC did not, however, prevent rotting nor arrest normal chemical changes. Rotting developed because of the restricted ventilation necessary for successful use of CIPC and was more severe in mechanically than in hand-harvested roots. The main advantage of using CIPC to extend the storage and feeding life of swedes is that the absence of sprouts makes the handling of the roots much easier.

Friesian bulls fed swedes preserved with CIPC and supplemented with 50% conconcentrates gave satisfactory growth compared with similar bulls offered a diet containing only barley.

The upgrading programme of. the Local Indian Dairy cattle in Malaysia to the Red Sindhi over a period of 21 years is evaluated. Heterosis was not observed among the Fx cross-breds for milk yield and related traits. The attempt to upgrade local dairy cattle using Red Sindhi however resulted in deterioration of performance.

Seeds of Amaranthus, melon, cowpea and tomato were planted in moist soil at 1, 4 or 7·5 cm depth and subjected to a heat stress of 45 °C for 10 h on the day of sowing (day 0), 1 day after sowing or 2 days after sowing. Seedling emergence was retarded by heat stress, the most drastic retardation being due to heat stress on day 1 for cowpea and tomato, day 2 for melon, and day 0 for Amaranthus. Emergence also decreased with increasing depth of sowing. The interaction of depth and heat stress was also significant in all cases, such that the delay in emergence due to heat stress tended to be greater with increasing depth of sowing. The agronomic significance of the results is discussed.

One pot and five field experiments were made to study different aspects of the competition between R. exaltata and maize.

The growth of young maize plants was not inhibited by being grown together in pots with young R. exaltata plants. In the field the soil tended to be somewhat wetter when the two species were grown together than when maize was grown alone, and was wettest with R. exaltata grown alone. Maize grain and total yield decreased and shoot yield of R. exaltata increased with R. exaltata plant density on both irrigated and unirrigated blocks of land, but yields were not much affected on either block by increase in plant density of maize or in nitrogen supply; maize yield was increased by irrigation but that of R. exaltata was not. Maize plant arrangement did not greatly affect maize grain and total yield or R. exaltata shoot yield, nor did arrangement of R. exaltata plants have much influence on their depression of maize yield, but R. exaltata caused a greater decrease in the grain yield of a short than of a tall maize cultivar.

R. exaltata plants germinating at the same time as the crop plants did not have much effect on maize grain yield if they were removed by 8 weeks after the seedlings emerged, but decreased it considerably if allowed to remain for 12 weeks or more; weeds sown 2 or more weeks after the maize emerged hardly grew and had little effect on maize yield. When maize and R. exaltata were grown together leaf area of the maize was little affected up to the time of flowering, but was decreased after flowering, while leaf area of the weed was greatly depressed. Up to 7–8 weeks after seedling emergence more of the ground area was covered by foliage when maize was grown with R. exaltata than when it was grown alone, but later the ground was completely covered by foliage in both cases. Dry weight of grain and shoot of maize increased and that of shoot of R. exaltata decreased when the weed plants were shortened with growth regulators.

Experiments made at Shika, Nigeria, over a period of 3 years showed that the drymatter response of Andropogon gayanus to applied N was curvilinear over the range 0–896 kg N/ha, with maximum yields being obtained at an application rate of about 500 kg N/ha. However, the highest return of dry matter per unit of fertilizer applied (14·4 kg D.M./kg N) occurred at 28 kg N/ha and there was only a modest increase in crude-protein content as N was increased, reaching a maximum of 10·5% at the highest level of N. Also, at both high and intermediate levels of N, A. gayanus was replaced by less desirable grasses.

May, the beginning of the rainy season, was found to be the most efficient time to apply N, although reasonable dry-matter responses were obtained by applying N in the dry season. ‘Nitro-chalk’ and calcium nitrate were more efficient sources of N than urea, sodium nitrate and, in the long term, ammonium sulphate.

The fertility, especially potassium status, of the Barming series in East Kent was studied by laboratory and pot test procedures to determine the effect of indigenous glauconite. Half of 12 otherwise similar soils contained appreciable glauconite.

Glauconite contributed positively to the potassium status of the soils, especially the B horizons (45–65 cm), and was associated with higher values of exchangeable potassium, cation exchange capacity, nitric acid soluble potassium and intensity of potassium supply as measured by ΔḠ. More potassium was taken up and more released from initially non-exchangeable sources to ryegrass from the glauconitic soils. The available magnesium content of the soils was also positively correlated with glauconite content but available phosphate was not.

Bean plants (Phaseolus vulgaris L.) were grown in field plots with the objective of comparing the effect of some soil amendments on sodium uptake and translocation at three levels of salinity in the soil.

Gypsum and wheat straw mulch treatments reduced the translocation of sodium from the roots to the stems and leaves at the higher external sodium level. Incorporation of animal manure with the soil had little effect on translocation at the higher level but may have promoted sodium translocation to the stems at the lower level.

Plant growth and survival were negatively correlated with the sodium content in the plant, particularly with that of the stems.

Twelve stagnogley soils of the Denchworth series from East Kent were studied to determine the effect of indigenous glauconite on their fertility. The presence or absence of glauconite was not the major factor controlling the potassium or magnesium status which was largely determined by the nature of the < 2 μm clay. Glauconitic soils had much higher levels of available phosphate than corresponding non-glauconitic soils due to calcium phosphate associated with the glauconite in the parent material. Weathering has partially converted this to aluminium and iron phosphates which were the main forms of phosphate present, especially in the A (0–15 cm) horizons.

The milk intakes of single-born Texel x Blackface and of pure-bred Blackface lambs suckling Blackface ewes was measured using a lamb-suckling technique. The shapes of the lactation curves were similar but the mean milk intake of the Texel x Blackface lambs was substantially greater than that of the pure-bred lambs at all points on the lactation curve. The Texel x Blackface lambs attained a mean maximum daily milk intake of 2418 g and the pure-breds 2075 g; mean total milk intakes during an 84-day period were 157 and 128 kg, respectively. Mean birth weights were 5·08 and 4·98 kg and the subsequent mean daily live-weight gains were 364 and 344 g, respectively, for the Texel x Blackface and pure-bred lambs. It is concluded that lamb genotype had a substantial and significant influence on the milk production of the ewes.

Seven hundred and twenty-five adult ewes of six breeds, namely Marwari, Chokla, Magra, Pugal, Jaisalmeri and Russian Merino x Marwari (F1) were typed for blood potassium, haemoglobin and erythrocyte-reduced glutathione (GSH) types. The nature of the association between each polymorphic trait and wool production efficiency (wool yield per kg body weight) in these breeds has been examined.

GSHh animals were predominant in all the breeds. A negative correlation was observed between wool production per kg body weight and erythrocyte glutathione level. In general, mean wool production per kg body weight was found to be more in animals of Hb type A than in other Hb type animals. No significant correlation between blood potassium level and wool production per kg body weight was found in any of these breeds.

Tetraploid lines were produced from colchicine treatments of European multigerm diploid material, and seeded in polycross plots. The same lines were crossed with European multigerm diploids to give anisoploid varieties, and also used as pollinators of American male-sterile diploids to yield monogerm and multigerm triploid varieties. Bigerm triploids were obtained from male-sterile hybrids heterozygous for the monogerm character, using European multigerm O-types in the grandparental generation. Double-cross monogerm triploids were obtained by crossing male-sterile diploids with non-equivalent O-types to provide male-sterile hybrids, and pollinating these with outbred tetraploids.

Results from 35 root-yield trials showed that the sugar yields of the anisoploids and triploids were similar to those of contemporary commercial varieties, but that outbred tetraploids were slightly, and inbred tetraploids considerably, less productive. Changes induced in characters other than root weight by chromosome-doubling of diploid material were sometimes important, but not consistent in magnitude or direction. It is suggested that these changes result from selection and random drift rather than the ploidy change.

A seed-yield trial demonstrated advantages of using hybrid seed-parents for triploid seed production. Problems of seed quality are discussed with particular reference to triploid varieties.

It is concluded that the main importance of multigerm anisoploid varieties was in their combination of good sugar yield with near-monogerm fruit clusters at a time when commercial monogerm varieties were deficient in yield; the chief value of triploidy lay in its application to the short-term improvement of genetic monogerm varieties. The development of monogerm anisoploids is considered unlikely; but some advantages of deriving monogerm triploid varieties from tetraploid seed-parents are indicated, and it is suggested that these may become increasingly important in the future.

Estimates have been made of the amount of energy fermented and the amounts of microbial protein and total fatty acids synthesized in the rumen of sheep given various rations of hay and concentrates. The sheep had re-entrant cannulas in the proximal duodenum. The amount of protein synthesized was calculated from the flow of RNA-N at the duodenum. The change in the amount of total fatty acids between the food and the proximal duodenum was also measured.

In Expt 1, six sheep were given a low-protein basal diet and the same diet supplemented with a vegetable protein concentrate with or without tannin treatment. Some 72% of the digestible energy was apparently digested in the rumen and an estimated 150–170 g microbial protein were synthesized per kg organic matter apparently digested in the rumen. Differences due to the dietary treatments in the amount of energy digested and the amount of microbial protein synthesized were small and non-significant.

In Expt 2, the effect of a supplement of 20 g/day of cod-liver oil (CLO) on digestion of a mixed diet of hay and concentrates was examined in five sheep. Despite a marked fall in the ratio of acetic acid to propionic acid in the rumen volatile fatty acids when CLO was added, there were no clear differences in the amount of energy fermented in the rumen, which averaged 64% of the digestible energy, or in the efficiency of microbial protein synthesis, which averaged 200 g/kg organic matter apparently digested in the rumen. On the basal diet an increase of 6·7 g total fatty acid/day occurred in the stomach. This was presumably synthesized in the rumen. However when CLO was added to the diet, a decrease of 4·1 g total fatty acid/day was measured.