THE INFLUENCE OF THE QUANTITY OF HERBAGE OFFERED AND ITS DIGESTIBILITY ON THE AMOUNT EATEN BY GRAZING CATTLE

Six calves, six heifers and six dry cows grazed a mature sward (treatments A and B) and a leafy aftermath (treatment C) in succession. The yields of herbage on the two swards were 7100 lb and 1950 lb DM per acre (7950 kg and 2180 kg per ha), respectively. The amounts of herbage offered daily were 47 lb (21–5 kg) DM per head (treatment A), 70 lb (32 kg) (treatment B), and 60 lb (27 kg) (treatment C), Two estimates of herbage organic–matter intake (O,M,I,) were made on each treatment; records of grazing behaviour were made on treatments B and C, The digestibility of the diet selected on treatment C was higher than that selected on treatments A and B, and the animals ate significantly more O,M, on treatment C, The total grazing times on treatments B and C were similar, but the animals found it more difficult to graze on treatment B
Herbage O.M.I. increased significantly from treatment A to treatment B, even though the quantity of herbage offered per day on treatment A greatly exceeded the amount eaten. The increase in O,M,I, was found to be associated with an increase in faecal 0,M, output, but the digestibility of the diet did not change.     

THE INFLUENCE OF GRAZING "IMMUNE COWS" ON THE LEVEL OF DICTYOCAULUS VIVIPARUS INFECTION ON PASTURE

At the Agricultural Research Institute, Hillsborough, Northern Ireland, during September and October, 1958, a field which was naturally infected with Dictyocaulus viviparus (lungworm) larvae was divided and one part was intensively grazed by cows which were not excreting lungworm larvae while the other part remained unstocked. Records were kept of the available herbage, total dry matter and the numbers of larvae on both areas. Grazing resulted in a marked reducuon of the larval numbers which was greater, in proportion, than that of the amount or herbage. Although severe grazing did not remove the infection, it so accelerated the decline in numbers that an infection level of one larva per lb. herbage was reached 7 weeks earlier on the grazed than on the ungrazed area. The herbage in both areas showed no larvae about 4 months after infected faeces were last voided on to it.     

THE EFFECT OF NITROGEN, STOCKING RATE AND FREQUENCY OF GRAZING BY BEEF CATTLE ON THE OUTPUT OF PASTURE

Two successive grazing experiments were conducted over 12 weeks on perennial ryegrass pastures with 50 and 44 young cattle to study the effect of N fertilizer when applied at a daily rate of 1 or 3 kg N/ha. At each level of N two stocking rates differing hy 20% were imposed. At the liigher N level and stocking rate, three frequencies of grazing were imposed. At the stocking rates imposed N tended to reduce the daily liveweight gain per head, but increased the total liveweight gain per ha by from 0.79 to 1.58 kg/kg N. A 20% increase in stocking rate depressed gain per head in both years. In the first year it did not improve gain/ha, hut in the second year gain/ha was increased by 12–17%. There was a tendency for performance per animal and per ha to increase as the grazing cycle was lengthened. In 1969 the highest yield in the whole season was 1880 grazing days and 1260 kg gain/ha. The overall response to N fertilizer was similar to that recorded in other reports, but it is possible that a lack of K had limited pasture growth.     

THE INFLUENCE OF SUPPLEMENTARY FEEDING ON THE HERBAGE INTAKE AND GRAZING BEHAVIOUR OF DRY COWS

The herbage intake and grazing behaviour of 4 dry cows on autumn grass receiving 2, 4, 6 or 8 kg concentrates/day, was assessed in a 4×4 Latin Square experiment. Total OM intake increased from 11±5 kg/day with 2 kg concentrates to 13±6 kg/day with 8 kg concentrates. The average supplementary effect was 0±46 kg increase in OM intake/kg OM fed as concentrates. Minutes per day spent grazing decreased from 495 with 2 kg concentrates to 359 with 8 kg. The mean decline was 22 min./kg concentrates or 28 min./kg OM in concentrates eaten. Herbage was eaten at an average rate of 47 min./kg OM.     

THE INFLUENCE OF SAMPLE SIZE AND NUMBER ON THE PRECISION OF ESTIMATES OF HERBAGE PRODUCTION AND CONSUMPTION IN TWO GRAZING EXPERIMENTS

Estimates of forage production and consumption were made, using dry-weight differences between samples from protected and grazed areas. Two sizes of cage for protecting areas from grazing were compared in four forages: brome grass (Bromus inermis Leyss.)/Iucerne (Medicago sativa L.); crested wbeatgrass (Agropyron crista-tum L.)/lucerne; intermediate wbeatgrass (A. intermedium (Host.) Beauv.)/Iucerne; and Russian wild-rye (Elymus junceus Fisch.). Production, over a three-year period, ranged from 1985 to 6286 kg/ha when estimated from 0.84 m² cages. Consumption ranged from 1584 to 5878 kg/ha. Yield estimates wben using 2.51 m² cages averaged 8% less than estimates from 0.84 m² cages. The number of caged sites needed in each plot to estimate a 95% confidence interval for annual production were 14 for four replicates, and over 30 for fewer replicates. Requirements for consumption estimates were similar. To estimate production within a 90% confidence interval 19, 10 and 4 caged sites were required from two, three, and four replicates, respectively. Consumption estimates within tbis confidence interval required 22, 10, and 5 samples from two, tbree, and four replicates, respectively. Caging requirements were tbe same for all combinations of plot size and forage species. Large cages increased precision sligbtly wben used on Russian wild-rye, probably because the forage was in rows 0.91 m apart.     

THE EFFECT OF NITROGEN, STOCKING RATE AND GRAZING METHOD ON THE OUTPUT OF PASTURE GRAZED BY BEEF CATTLE

An experiment was conducted in 1971 and 1972 to study the effects of two levels of fertilizer N (50 and 504 kg/ha) on the productivity of pastures grazed by young beef cattle. Two stocking rates were imposed at the lower N level and three at the higher. In addition to rotational grazing, set-stocking and an integrated grazing-conservation system were included. The responses/kg N were approximately 1 kg live-weight gain, 19–24 Meal ME and 8–9 kg DM. Maximum yields of 1200–1300 kg live-weight gain/ha and 25,000–27,000 Meal ME/ha were recorded. Productivity of set-stocked pasture was similar to rotational grazing at the high N level, but lower at low N. The integrated system yielded comparable results to high-N rotational grazing. Performances and herbage intakes per animal reflected the stocking rates imposed.     

INFLUENCE OF NITROGENOUS AND PHOSPHATIC FERTILIZERS ON SETARIA SPHACELATA IN SOUTH AFRICA

In an experiment in which three levels of P and five levels of N fertilizer were applied, it was found that at the highest levels of fertilization the hay yields were increased fourfold, the percentage of crude protein was doubled, the crude-protein yield increased sevenfold, and the P uptake increased five times over those of the control. This increased production was mainly a result of the use of N fertilizer, although significant PxN interactions were obtained at the higher levels of N fertilizer. By itself, P fertilizer had little effect on any of the above increased yields. It would appear that very much higher production, especially of CP and P, might be attained, if even higher levels of fertilizer were applied.
Basing income on hay yields and expenditure on fertilizer costs, the greatest profit was obtained from the higher levels of fertilization. This applied especially to N fertilizer.     

THE INFLUENCE OF SEVERAL FACTORS IN DETERMINING THE GRAZING BEHAVIOUR OF BORDER LEICESTER × MERINO SHEEP

Over a period of 20 months twenty continuous, 24-hour, observations were made on the grazing behaviour of Border Leicester × Merino sheep. Distinct seasonal changes were found in the pattern of grazing. Grazing usually began during the dawn period and decreased at dusk. In spring and summer there were two peaks of grazing, but there was only one peak in autumn and winter. The percentage of grazing taking place between 6 a.m. and 6 p.m. varied with season, and was highest in spring and early summer. These seasonal changes in the pattern of grazing appeared to be independent of grazing pressure, or of the nutritional requirements of the sheep.
The mean grazing time, for all observations, was 8·2 hours with a standard deviation of 0·97. Decreasing pasture availability increased grazing time, as shown by an increased intensity of grazing.
Ruminating times were found to be considerably lower than have been reported for cattle. There was a significant negative correlation between ruminating time and the nitrogen content of available pasture.
There was no clear evidence that the number of lambs carried before parturition, or suckled after parturition, had any effect on grazing time.
There was no evidence that the behaviour of one sheep influenced that of another, even of a twin, grazing nearby.
Consistent differences between sheep were found for ruminating time. The variation in grazing time between sheep, at any one time, was considerably greater than previously reported and differences between sheep were not consistent.
Variation in grazing time appeared to be less in flocks of less than 6 sheep than in flocks of 6 to 12 sheep.     

THE INFLUENCE OF TYPE AND LEVEL OF SUPPLEMENTARY FEED ON INTAKE AND PERFORMANCE OF BEEF CATTLE ON PASTURE

Two experiments, each of 6 weeks dehydration, were conducted in 1972. In Expt 1, 24 cattle were grazed in individnal paddocks during July and August and received one of 4 treatments over a 6-weeks period: no supplements; straw ad lib; 3.3 kgj. day sugar-beet pulp; 4.0 kg/day molasses. Mean daily live weight gains were significantly increased by the sugar-beet pulp and molasses supplements; which also increased OM and DOM intake significantly. The increase in total OM intake per kg OM in the supplement was 0.48 for sugar-beet pulp and 0.67 for molasses. In Expt 2, 18 cattle grazed in groups of 3 during November and December. Two groups each received 0.5, 3.5 or 6.5 kg/day sugar-beet pulp over a 6–weeks period. There was no significant difference in live weight gain between treatments, and no significant difference in total intake. Intake from pasture declined with increasing level of supplement, so that the average increase in OM intake per kg OM in the supplement was 0.28. Hie results are discussed in relation to availability of pasture and the effects of the supplements on intake.     

STUDIES ON THE EXTENSION OF THE GRAZING SEASON

In a small plot trial good yields of foggage of satisfactory botanical composition with cocksfoot dominant were produced from a mixed-species pasture after it had been cut for silage in spring and again in summer. Production in the following year was satisfactory. The advantages of using ordinary pastures for winter grazing, especially if this occurs only during their last winter before ploughing, are discussed. From a study of various autumn treatments it is concluded that the optimum management for foggage production in the north-east of Scotland is to close fields on or near 10 August when 3 cwt. nitro-chalk per ac. should be applied; a higher rate (6 cwt. per ac), though it increased yields and percentage crude protein immediately, and also during the subsequent summer, conferred no benefits of practical importance. Effects of K fertilizer applications were negligible. Closing as late as the beginning of September gave smaller but useful yields of a higher protein foggage and the sward was less cocksfoot-dominant. Autumn closing and fertilizer treatments did not affect foggage wastage during winter, which averaged 14 per cent of the initial organic-matter yield; the percentage of crude protein in standing foggage rose.     

STUDIES ON THE EXTENSION OF THE GRAZING SEASON

Foggage grazing trials with beef-store cattle and in-calf dairy heifers during four successive winters in Aberdeenshire are described. Many of the animals received only very small quantities of supplementary fodders, but their performance was satisfactory in all cases. During the last two winters, silage and oat straw contributed 40–50% of total food dry-matter intake. It is suggested that this level of supplementary feeding would be satisfactory in practice.
In a comparison of store-feeding systems, four in-wintered (housed) steers were 110 1b. per head heavier than their out-wintered monozygous twins at the end of the winter-feeding period. Live-weight differences averaged 27 1b. per head one month later and were negligible at the end of summer. From the results of a metabolism trial it was concluded that the spring weight-loss suffered by the housed cattle was due mainly to a reduction in the weight of gut contents.     

A NOTE ON THE LIVEWEIGHT CHANGE OF SHEEP GRAZING AT THREE STOCKING RATES AND TWO LEVELS OF NITROGENOUS FERTILIZER

The liveweight changes of sheep grazing at 3 stocking rates and 2 levels of N fertilizer were recorded. The results are discussed in relation to the model proposed by Owen and Ridgman (1) for short–term periods of grazing.     

STUDIES ON SHEEP GRAZING IN THE NORTHERN PENNINES

The sheep grazing intensity and herbage intake on 3 high-level grasslands above 2250 ft were investigated. The seasonal intake, which varied from 450 to 700 lb dry matter/acre, was obtained by the yield-difference method, using cages moved monthly.     

EFFECTS OF COW SLURRY ON HERBAGE PRODUCTION, INTAKE BY CATTLE AND GRAZING BEHAVIOUR

Grassland plots were dressed with different amounts of cow slurry in January or March and grazed by dairy heifers at intervals from late April to August. In the first experiment slurry was applied at levels up to 56 tonnes/ha (22±4 tons/ac) in March. Total herbage DM production was directly proportional to the amount of slurry applied. There was no effect of treatment on percentage herbage utilization. In the second experiment slurry was applied at levels up to 100 t/ha (40 tons/ac) in January or in March. There was no significant effect of time or level of slurry application on herbage production or on animal intake, but the behaviour of the heifers was modified during the first eight weeks after plots had been dressed with 75 or 100 t/ha (30 or 40 tons/ac).     

THE RELATIONSHIP BETWEEN INTENSITY OF GRAZING AND THE HERBAGE CONSUMPTION AND GROWTH OF CALVES

Experiments were conducted in 1967 and 1968 in which HerefordXFriesian (Experiment 1) and Friesian (Experiment 2) steer calves horn in April were turned out to graze at one week or 3 months of age, respectively, and maintained at three stocking densities in the ratio 1:2:3 animals per unit area. The calves grazed paddocks of S23 perennial ryegrass in rotation, and were moved when the height of grazed stubble at the medium stocking density was reduced to 8 cm. The rate of liveweight gain and herbage intake per head declined as stocking rate increased. When the results of the two experiments were compared, the weight gain of the calves was more closely related to the weight of herbage residues than to the height of the grazed sward. The rate of liveweight gain was depressed when the amount of herhage left after grazing fell helow 2000–2500 kg OM/ha (1800–2250 Ib/ac).     

THE INFLUENCE OF VARIOUS FORMS OF NITROGENOUS FERTILIZER ON THE GROWTH OF A PERENNIAL RYEGRASS / WHITE CLOVER SWARD IN EARLY SPRING

The effect of 4 or 5 forms of nitrogenous fertilizer on the yield and botanical composition of a perennial ryegrass/white clover sward was examined in 3 different years. The uptake of N by the grass was also estimated. Ammonium nitrate (as Nitro-Chalk), ammonium sulphate and urea gave similar yield increases, although in one year, when high rainfall followed the application of fertilizer, urea was slightly inferior. Gas liquor gave variable responses in the 3 years. Nitroform, a urea-formaldehyde, was generally less effective than the other forms of fertilizer. The uptake of N from Nitro-Chalk, sulphate of ammonia and urea did not vary greatly from year to year although the uptake of soil N by the untreated control did.
Response to N in the yield of dry-matter varied from year to year. This variation was due partly to differences in the amount of clover present and partly to differences in the extent to which N taken up by the grass was used for the synthesis of dry-matter.
The white clover content of the sward was not greatly reduced in spring by the application of the fertilizer, and there were no consistent differences between the effects on clover of the forms of the fertilizer. A reduction was apparent in the summer but not in the autumn.
It may be necessary to increase replication above the level of 3 to 6 which is frequently employed in field experiments if more precise quantitative estimates of response and of the relative efficiency of various forms of nitrogenous fertilizer are required.     

NAA和2,4-D对脱毒马铃薯扦插苗生长及产量的影响

本文研究了不同浓度NAA和2,4-D配合使用对马铃薯扦插苗的生根、生长及产量的影响。结果表明,6种处理中,其中浓度为NAA5mg／l,2,4－Dlmg／l的处理扦插苗生根数多,成活率高,植株长势强,产量最高。     

FURTHER STUDIES ON SHEEP GRAZING IN THE NORTHERN PENNINES

The grazing of 3 relatively productive grasslands ( Festucaf Agrostis ) by hill sheep was examined in relation to herbage consumption, grazing pressure, dung deposition and the number of sheep in the area. Herbage intake ranged from 400 Ib/ac/annum (dry weight) on the highest (2450 ft O. D.) and most exposed grassland to 800 Ib/ac/annum on a grassland (1700 ft O. D.) adjacent to extensive heather moorland on blanket bog. The highest pressure (5·5 sheep/ac) was also found on grassland surrounded by blanket bog (1 sheep/14 ac).