On three occasions in May—July one half of a ryegrass pasture was grazed intensively by cattle and the other was mown. In August and September these areas, designated fouled (F) and clean (C) respectively, were each strip-grazed by two groups of five cows. One group on each area had a herbage allowance of 11·4 kg dry matter per cow per day (C11 and F11) and the other 20·4 kg (C20 and F20).

Before the August-September grazing the fouled area had 2·8% of its surface covered by faeces. After this grazing 23 % of the F n area and 34 % of the F20 area were classified as having been rejected by the cows. However, the upper parts of the sward on these rejected areas were in fact grazed. There were only small differences in N and soluble-carbohydrate contents between the herbages offered and rejected.

Organic-matter digestibility (%) and intake (kg/cow per day) for the four groups were: C11, 73·0 and 10·5; C20, 74·9 and 11·7; F11 , 74·4 and 9·6; F20, 77·0 and 10·6. The C11 cows consumed all the herbage allowed to them, but the F11 rejected 13%. Digestible organic matter intake was affected more by grazing intensity than by fouling; this was the case also for milk yield, milk composition and the live-weight change of the cows.

Yields of maize and cotton given N, and sometimes K but no P, were related to equilibrium values of the monocalcium phosphate potential (½pCa+pH2PO4)eq', at which P is neither lost nor gained by the soil. The responses to phosphate fertilizer were not clearly related to phosphate potentials though small responses at large values of (½pCa+pH2PO4)eq were sometimes explained by very small values of δI/δQ (the rate of change of ½pCa+pH2PO4with change in the amount of P on the soil) or by soil reaction. In only one set of maize experiments, response to P was related to δI/δQ. (½pCa+pH2PO4)0 and (pH2PO4)0', determined without adding P to the solution, were equally useful and both were just as well related to yields without P as (½pCa+pH2PO4)eq' (pH2PO4)0 appeared more useful than the logarithm of the total P concentration measured without added P. It wa not necessary to find the equilibrium phosphate potential, or to measure Ca concentration, but correcting the phosphate concentration for pH (so that only H2PO4-ions were taken into account)was worth while.

Three varieties of Avena byzantina C. Koch., Sierra, Avon and Anita, originating respectively in California, Australia and South Africa, together with the Dutch variety Condor (A. sativa L.) were used as ‘subject’ varieties in crosses with a range of nine tester varieties of mainly north-west European origin. The results of a yield trial of spaced F1 transplants and a drilled F2 trial are presented.

In the F1 trial there was marked heterosis for grain yield, the thirty-six crosses yielding, on average, 109 % of the higher yielding parent, with individual cross values ranging from 68 to 139%. Heterosis was more marked in sativa × byzantina crosses than in sativa × sativa crosses and the variety Sierra showed particularly high general combining ability. In the F2 trial, heterosis was considerably reduced and the thirty-six crosses yielded, on average, only 96% of the higher yielding parent. In some F1 crosses, heterosis for grain yield was accompanied by transgression of the higher yielding parent in number of panicles per unit area. The number of grains per panicle was positively correlated with grain yield in the F2 trial but no heterosis was observed for this component. Grain size was negatively correlated with yield in the F2 trial and heterosis for this component was observed in a few crosses in which yield heterosis occurred.

Straw height was positively correlated with grain yield in the F1 trial but negatively correlated in the F2 trial. Crosses showing heterosis for yield exceeded the mid-parent but not the taller parent in straw height. The ratio of grain yield to straw yield was higher for the progenies of the byzantina varieties Sierra and Avon than for the progenies of the sativa subject Condor. Grain yield was positively correlated with number of days to 50% panicle emergence in both trials.

It is concluded that the A. byzantina varieties Sierra and Avon could, with advantage, be used for hybridization with adapted genotypes of A. sativa, thereby enlarging the gene pool available to oat breeders in north-west Europe.

Eighty Friesian heifers were used to study the effect on milk production of two fixed levels of intake at two stages of the lactation. The rations were estimated to contain 7·9 and 6·2 kg starch equivalent per day, with adequate protein content. The heifers were allocated at random to these two levels of intake for weeks 1·9 of lactation and re-allocated at random to them for weeks 10–18 of lactation. Apart from minor variation the heifers were all fed alike for the remainder of the lactation.

The higher level of feeding increased yields of milk and milk solids and solids-not-fat content in each period but had a smaller effect in mid- than in early lactation, a trend which was shown to continue further into later lactation. It also conserved body reserves.

There was a residual effect in weeks 10–18 from the level of feeding in weeks 1–9 of lactation. This was directly additive to the effects of the current level of feeding. Those animals which had received the higher level of feeding in weeks 1–9 yielded more milk of higher solids-not-fat content than those which had had the lower level of feeding in weeks 1–9. The former group gained less live weight. The effect on milk production over the full lactation from additional feeding in early lactation was three times that observed in early lactation itself. Additional feeding in mid-lactation did not have a residual effect.

The absolute output of milk per unit of food over the 18-week period was greatest for that group which had received the lower level of feeding throughout, followed by the group which received the higher level of feeding in weeks 1–9 only. This superiority was achieved at the expense of body reserves. There was a negative regression of live-weight change on milk production.

Estimated intakes of metabolizable energy agreed closely with requirements for milk production as indicated by the Agricultural Research Council (1965).

The concentration of copper in the blood of more than 300 sheep of a grassland flock was determined on each of five occasions between May 1965 and June 1966. Six breed classes, Scottish Blackface, Cheviot and Welsh Mountain, and the three crosses among these breeds, were involved.

Breeds differed significantly in blood copper concentration with the Blackface having consistently the lowest and the Welsh the highest values. Crossbred sheep showed marked heterosis. Their levels were mostly at or near to the concentration of the parental breed with the higher value. Within breeds there was a positive regression of blood copper level on live weight of ewe.

Ewes which had produced lambs affected by swayback in 1964 had lower levels of copper in their blood than ewes which had produced normal lambs. The difference was significant and most marked in winter.

Ewes which were barren had, subsequently, higher blood copper concentrations than ewes with lambs. Ewes with single lambs had on average slightly higher levels than those with twins (but not significantly so), however, the effect differed among the breeds. Blood copper levels differed significantly on most occasions with the week in which ewes lambed in relation to the date of bleeding. Age of ewe had significant effects on copper concentration only at one bleeding (January 1966).

There was an indication that classes low in copper concentration, notably Blackfaces and mothers of swayback lambs, showed a relatively steeper decline in copper levels during the winter than did other sheep.

Records have been analysed from a small herd in which early weaning was practised. Piglets were weaned when average weight was 7–8 kg, at about 30 days old. Decreased feeding of sows, followed by a short period of fasting, was practised at weaning.

Mean duration of suckling was 31·5 days and mean interval from weaning to oestrus 6·0 days. 93% of sows conceived to service at the first or second heat period. Mean farrowing interval for all sows was 159·7 days (151·9 days for those holding to the first service). Corresponding annual farrowing frequencies, calculated from these figures, are 2·29 and 2·40.

Litter sizes at birth and at weaning were 10·7 and 9·3; corresponding weights of piglets were 1·74 and 7·99 kg. With increase of litter sequence there was a significant decrease of weaning weights; however, there was also an increase in size of litter weaned. Seasonal changes of piglet weight were also found. Early weaning can be considered a useful way to increase production.

Two field experiments have been conducted to investigate the pattern of tillering, ear emergence and survival of the component tillers of three barley varieties, representing old and new varieties. The varieties were grown under contrasting nitrogen fertilizer levels and plant spacings. The results reported are for the variety means and variety x nitrogen and variety x spacing interactions. After the main stem (M) the most frequently occurring tiller was the tiller appearing in the axil of the first true leaf (T2), followed by the coleoptile node tiller (T1) and the tiller in the axil of the second true leaf (T3). The T1 tiller occurred most frequently in the newest variety, Deba Abed, and least in the oldest one, Spratt Archer. Survival rates of the shoots were highest in M, followed by T2, T1 and T3. Higher-order tillers occurred relatively infrequently and had low survival rates. M contributed the largest percentage of the grain yield, followed by T2, T1 and T3. The 13% grain yield advantage of Deba Abed over Spratt Archer was mainly accounted for by the difference in production by the T1 tiller. The results are discussed in. relation to the only other known paper on component tillers in barley.

Milk yield data obtained by the lamb-suckling technique on twenty-four ewes over a period of 5 consecutive days in the second and third week of their lactation have been related to lamb body weights and lamb body-weight changes over the same period. The regression equation obtained was

The equation was used to estimate the milk consumption of lambs over the range of lamb body weights and lamb body-weight changes studied. The standard errors of these estimates have been computed for comparison with those obtained directly from the lamb suckling technique.

The role of the prediction equation in estimating daily milk consumption of lambs is discussed.

Individually-penned adult Merino wethers were fed for 16 weeks on a basal diet of ground, pelleted oat straw or Phalaris straw. Urea was supplied either in a salt-urea block containing 30% urea, or as crystalline urea incorporated into the pellets. A commercial mineral supplement was given during the first 8 weeks, but this was replaced with a laboratory-prepared mineral mix during the second 8 weeks.

Urea supplementation significantly reduced live-weight loss. Over the 16 weeks control sheep lost a mean of 14·5 kg, and supplemented sheep 8·7 kg body weight. Most of this response to urea occurred during the second half of the experimental period.

Food intakes of all sheep increased over the first 2 weeks and then fell. In the unsupplemented groups, levels of intake then remained fairly low, whereas in the sheep fed urea food intakes rose over the final 6 weeks of the experiment. There was a significant linear regression of live-weight change on food intake only with the urea-fed sheep. Intakes of urea-N from the blocks were extremely variable between individual sheep and between periods within sheep; in most cases, however, they appeared to be adequate, as this type of supplementation gave results similar to those obtained by mixing urea throughout the roughage.

There was no significant effect of urea on total wool growth during the experimental period, although wool growth in the supplemented shepp showed a rise towards the end of the experiment. Wool growth in any 4-weekly period was closely related to food intake and live-weight change during that period.

Controlled-environment experiments showed that development of the coleoptile node tiller (T1) was suppressed much more than that of the tiller appearing in the axil of the first true leaf (T2) by high temperature (24/15 °C; 19/10 °C; 10/6 °C), by reduced photoperiod (16 h; 12·5 h) or by low light intensity (1100 ft-c; 1000 ft-c), but minimally in the newest variety, Deba Abed. Unlike previous field experiments, the T1 tiller appeared on more Spratt Archer than Maris Badger plants. Maris Badger plants produced more T1 tillers in a high-low temperature regime (19/10 °C; 10/6 °C) than in continuous low temperature (10/6 °C). In a field experiment T1 tiller number (and yield), but not the number of other major shoots, were severely reduced by late sowing of Spratt Archer, progressively reduced in Maris Badger, but minimally in Deba Abed. This seemed to be associated with higher temperatures at later sowings.

Adult Merino wethers were fed for 16 weeks on diets of oat straw mixed with urea and pelleted (A); oat straw pellets, with access to a salt block (B); oat straw pellets, with access to a salt-urea block (C); Phalaris straw mixed with urea and pelleted (D); and Phalaris straw pellets (E). A commercial mineral supplement was given during the first 8 weeks, and a laboratory-prepared complete mineral supplement supplied during the second 8 weeks. During the fifth to eighth weeks (period I), and the thirteenth to sixteenth weeks (period II), digestibility and balance studies were conducted on sheep from each treatment.

Digestibilities of organic matter (O.M.) and cellulose were generally increased by the addition of urea, but only in one comparison, between diets A and B, was the difference significant. Urea did not significantly affect water intake in relation to food intake.

Urea increased nitrogen (N) intake, faecal and urinary N excretion, and N balance, these effects being more pronounced in period II. All sheep were in negative N status in period I; five of the 12 urea-fed sheep were in positive N status in period II. In diets B and C water intake and urine output were positively related to salt intake, but in no diet was there a significant relation between urinary N excretion and total output of urine.

Sulphur balances (excluding wool) were generally positive and did not improve significantly in period II despite higher sulphur intakes. However, a corresponding increase in the intake of phosphorus, from 0·5 g/day to about 2·0 g/day, brought nearly all sheep from negative to positive phosphorus balance. With the urea diets there was a significant, negative relation between urinary N excretion and phosphorus balance.

Intakes of sodium, potassium, calcium and magnesium appeared to be sufficient in both periods.

It seems likely that the improved response to urea which occurred during the experiment was due to the change in mineral supplementation rather than to adaptation to urea.

The effect of nitrogen fertilizer and irrigation treatments on the leaf-area index (L) and net assimilation rate (E) of a monthly cut sward of Italian ryegrass (Lolium multifolium) is considered.

Response to nitrogen was due to increase in both L and E, whereas response to irrigation was largely due to increase in L.

The data show little evidence of a seasonal decline in E. This may have been due to the mid-season replacement of old tillers by new, and by the encouragement to new leaf production caused by periodic harvesting.

Two experiments with sugar-beet seed crops at Dunholme Field Station Lincolnshire,1955–7, one at Broom's Barn, Suffolk, 1963–4, and two in Bedfordshire 1965–7, compared transplanting with various direct.drilling techniques. The early experiments were made with multigerm varieties and the 1965–7 experiments with genetic monogerm varieties.

At Dunholme direct drilling under a barley cover crop controlled virus yellows and yielded more multigerm seed suitable for processing than did transplanting. In later experiments transplanting gave variable yields; pests damaged plots transplanted in autumn and those transplanted in spring were susceptible to drought. Many transplants lodged and ripened late and direct drillings produced seed that germinated better.

Direct drilling during July with no cover crop consistently yielded better than undersowing or open drilling in August. To establish a regular, dense stand of plants, which is essential for large yields of seed of good germination was more difficult with than without cover crops. The time the cover crop was removed did not consistently affect yield. Crops sown in summer without cover yield most seed but are most susceptible to disease and are unsuitable for areas with a disease risk.

Twenty-seven ewes in various states of fatness, and either non-pregnant or between 72 and 144 days pregnant, were slaughtered and the volumes of digesta and abdominal organs were measured. There was a significant negative relationship between the volume of rumen contents and the volume of uterus plus abdominal fat plus other abdominal organs.

Fifty-nine Mutton Merino and cross-bred 2-year-old and older ewes were allotted to two groups according to age, weight and breeding performance in the preceding 1966/67 in-season. In the experimental ewes the treatment started on 22 March 1967 and consisted of vaginal sponges (Syncro-Mate) inserted for 17 days and 750 i.u./ewe of P.M.S. injected on the day of the removal of the sponges.

As from 1 March, all the ewes were ‘teased’ daily but hand service commenced on 20 April, to coincide with the 13th day after the removal of the sponges.

At the time of sponge insertion, approximately a third of the ewes, in each group, were already cycling. The treatment advanced the average post-treatment oestrus by 8 days, out of a possible 15 days, synchronized it in 70% of ewes and shortened the tupping season in 97% of treated ewes to 9 days (23 days in controls), but otherwise the performance of the treated ewes (and their offspring) did not differ from that of the controls. In both groups forty ewes lambed (68%) and fifty lambs were born (85%). Out of nineteen dry ewes, five were in anoestrus and in at least nine, an early death of the embryo could be suspected. Among the reproductive activities during the preceding in-season, date of weaning, days of suckling and barrenness may be implicated in the failure to breed in the spring.

The competitive ability of two natural populations of Dactylis glomerata, one from Norway and the other from Portugal, was investigated by growing them in monoculture and together in a mixed sward under different temperature and light regimes. At 7 °C and 8 h photoperiod, the performance of the prostrate Norwegian population grown in mixture with the erect Portuguese population was suppressed as compared with its performance in monoculture. However, at 30 °C and 16 h photoperiod, when the growth habits of these two populations were reversed in comparison to those at 7 °C, the dry weight per plant of the erect Norwegian population was significantly greater in the mixed sward than in monoculture. The dry weight per plant of the Portuguese population did not differ significantly in the two types of sward at either temperature. The results are discussed in relation to competition for light.

Subjectively assessed body condition scores, determined on the live animal, were related to the percentages of chemical fat in the fleece-free empty bodies of 30 adult Scottish Blackface ewes. The results show that body condition scores can provide an acceptable and useful estimate of the proportion of fat in the live animal, and that the level of prediction is superior to that afforded by live weight.

Various rates of nitrogen fertilizer were applied in early and late spring to two densities of winter wheat to examine their effects on grain yield and its components. A severe attack of ‘sharp eyespot’ (Rhizoctonia solani) allowed an assessment of the effects of the treatments on the incidence of this disease.

The disease level was much higher where nitrogen was applied early and increased with increase in nitrogen up to 120 units applied; it was slightly higher at the higher density. Grain yield was slightly greater where nitrogen was applied late; early application gave more, but smaller, ears. Main shoots produced at least 70% of the grain in the high-density plots but less than 50% at the low density. Tillers appearing after early March contributed little to grain yield at the higher density but substantially at the lower one. Tillers produced after early April died without heading. In general, the chances of survival of a tiller diminished with delay in the time of its appearance, but some early tillers died while later ones survived and produced ears. The chances of survival of later tillers were greater at low density and high rates of nitrogen.

A radiographic study was made of the skeleton of eighty-three foetuses from twenty-four litters killed between the 37th and 112th day of gestation. Measurements were taken, from radiographs, of the length and depth of the skull and the length of the diaphyses of the humerus, radius, ulna, metacarpus, ilium, ischium, femur, tibia, fibula, calcaneum and metatarsus. Skull length, humerus and metatarsus were selected for statistical analysis. The litter mean lengths of the diaphyses were studied in relation to age, weight, and age and weight jointly. Within-litter differences in bone measure-ments were closely associated with foetal weight differences.

The relationships of litter mean log. lengths of the skull, humerus and metatarsus upon age were best fitted by a quadratic regression, and with mean log. foetal weight by linear function regressions. A joint regression incorporating both age and weight of the foetuses fitted the data significantly better than equations based on weight or age alone. Skull length was found to have a growth coefficient between the 51st and 112th day of gestation significantly lower than that of the other bones examined. The age at which the primary and secondary ossification centres appear was studied.

Calcium metabolism in dairy cows has been studied at three periods, namely 2 weeks before and 2 weeks after parturition, and also at peak lactation. Of the four parameters studied—percentage absorption from the diet, endogenous excretion, exchangeable pool size and bone accretion rate—only the last showed significant changes, falling at parturition and rising to pre-calving levels subsequently. There was no increase in the percentage absorption of calcium from the diet after calving but total calcium absorption rose because of increased dietary intake.