摘要:

AbstractHerbage intake is usually depressed when beef cattle grazing abundant pastures are supplemented with energy‐rich feedstuffs but relatively little is known about the effects of supplementation on the components of ingestive behaviour. An experiment was conducted to establish the effect of ground corn (Zea maysL.) on the ingestive behaviour of yearling Angus and Angus × Hereford steers (Bos taurus) (mean live weight (LW) of 323 kg) grazing autumn stockpiled Boone cocksfoot (Dactylis glomerataL.) using a tethered grazing system in which the experimental unit was the tethered steer and its grazing area (45 m2) for one grazing session. Herbage dry matter (DM) mass was 1662 kg ha−1and herbage DM allowance was 7–5 kg steer−1for each grazing session. Herbage DM intake was measured as the difference between herbage DM mass offered and refused. Grazing took place during two daily sessions each of about 2 h duration commencing at 08.00 and 14.00 h for 9 days. Ground corn (0, 1·5, 3·0 and 4·5 kg steer−1) was fed each day at 12.00 h and had no significant (P<0·05) effect on rate of DM intake, rate of biting or DM intake per bite. Mean DM intake was 6 2 kg steer−1d−1(87 mg (kg LW)−1min−1). Steers averaged 4832 bites per grazing session, with a mean DM intake per bite of 644 mg (2·0 mg (kg LW)−1) and a mean rate of 44 bites min−1. Data obtained at the beginning and end of each grazing period on ingestive behaviour of one group of four steers (mean LW of 306 kg) fitted with oesophageal fistulae supported data for the two groups of normal steers and showed no response to supplementation. Mean values for rate of DM intake, DM intake per bite and rate of biting established for the fistulated cattle were 73 mg (kg LW)−1min−1, 521 mg bite−1(1·7 mg (kg LW)

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1988.tb01890.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractApplications of N fertilizer (0.40, 80, 120 and 240 kg N ha−1year−1in dressings of 40 or 80 kg N ha−1) were made to a perennial ryegrass/white clover (Lolium perenneL.Trifolium repensL.) pasture growing on a humus iron podzol reclaimed from heather (Calluna vulgarisL.) moor in 1982 and 1983. Where no N was applied, estimates of Ni fixation and mineralization were almost equal, being approximately 50 kg N ha−1year−1from each source. Apparent efficiencies of fertilizer use were generally low; for each dressing they ranged between –0·7 and 25·5 kg dry matter (DM)kgN−1. Also, responses to N fertilizer were affected by previous dressings. The net N recovery in harvested herbage from application of 120 kg N ha−1year−1was

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1988.tb01891.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractIn plots of perennial ryegrass and white clover, regular treatment with chlorpyrifos and methiocarb more than trebled the clover content of the sward, compared with untreated plots, in just over 2 years from sowing. Chlorpyrifos alone accounted for most of the effect, which was attributed mainly to the control ofSitona lepidus.Combined treatment increased total herbage dry matter yield by 4·24 t ha−1during this period but had little effect on grass‐only plots. Methiocarb appeared to have contributed by assisting earlier establishment of clover, but otherwise had little effect until slugs, which were initially uncommon, became more abundant in the later stages of the experiment. The effect of slug control was most noticeable in a cultivar of low cyanogenic potential. This factor did not influence the effect of chlorpyr

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1988.tb01892.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractThe effects of fasting on feeding behaviour, intake rates, and diet quality were studied with steers grazing vegetativeLolium multiflorumswards. Fasting interrupted the normal alternation of grazing and rumination and led to longer grazing times (0·65vs.0·45 of observed time), shorter rumination times (0·15vs.0·30 of observed time), and higher total dry matter (DM) intakes (6200 g DMvs.3750 g DM d−1)‐Fasting did not affect prehended bite size which averaged 047 g DM bite−1. Declining bite size within a day was explicable by changes in herbage mass. Biting rate (38.9 bites min−1) and instantaneous intake rate (2675 g DM min−1) of fasted animals were considerably higher than non‐fasting animals in the mornings, but neutral detergent fibre (NDF) concentration of the diet (0 742 of organic matter) was generally not depressed by fasting. Consequently, non‐fasted animals appeared to be feeding suboptimally since their nutrient intake rates were considerably lower than that which they are capable of exhibiting. Mastication rates per unit NDF intake were considerably lower in the morning for fasted animals (0·78 chews g−1NDF intake) which suggested that their intake rates may have led to larger ingested particle size. Therefore, onLolium multifiorumswards, the steers attained a higher intake rate by masticating the forage less while main

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1988.tb01893.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractA series of laboratory experiments is described to investigate the susceptibility of grass forage to losses during mechanical field conservation operations in relation to dry matter content. Losses were measured during a simulated manual ‘tedding’ treatment carried out on grass samples being dried on a laboratory thin‐layer drying rig. Values of loss per successive treatment remained at a near constant low level at low dry matter (DM) contents, except for a somewhat higher loss level from the first treatment. As DM content rose above about 60%, the level of loss per treatment rose rapidly with increase in DM content. A relationship between loss per treatment and DM content was derived from the data by a bilinear regression analysis, and this will be incorporated into an Operational Research model of forage conservation sy

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1988.tb01894.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractSpring‐seeded rape requires approximately two‐thirds of the growing season in the north‐cast USA, to reach physiological maturity. Harvest frequency studies were conducted with rapes and rape hybrids in Pennsylvania to determine whether forage yields and/or quality can be improved with multiple harvests, and whether cultivars respond similarly to harvest management. Nitrogen was applied at 75 kg ha−1at seeding and 75 kg ha−170 d after seeding. Additional fertilizer was applied according to soil test results. A split‐split‐block design was used. Harvest frequencies of 180, 90, 60, or 30 d were randomly assigned to blocks. Cultivars were randomized within each harvest frequency, with four replicates. Amount of regrowth of all cultivars after mid‐August was highly variable, depending on weather. Foliar diseases and aphids lowered yields in different years. Cultivars differed in susceptibility to diseases and aphids as well as in morphology. Forage yields and crude protein yields of rape generally were highest with the 90‐d harvest frequency, whereas crude protein concentration was highest with the 30‐d frequency. Meanin vitrodry matter digestibility (IVDMD) values were high regardless of harvest frequency, cuttivar, or sampling date. Yield differences between cultivars generally were greatest with one harvest at 180 d; mean yield was highest for forage rapes, intermediate for winter oil rapes, and lowest for rape x Chinese cabbage hybrids. Under frequent harvesting, BLE rape and the rape x Chinese cabbage hybrid performances were exceptional as regards forag

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1988.tb01895.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractIn laboratory experiments to clarify earlier field observations,Sitona lepiduslarvae caused significant damage to established clover plants at infestations of approximately 1–2 per plant. When eggs were placed on the soil, cultivars of differing cyanogenic capacity were damaged equally. The plants did not recover when larval feeding ended.Leatherjackets, slugs and ‘lucerne flea’ fed most on the least cyanogenic cultivars, even where no choice was offered. Plants ultimately recovered from damage by leatherjackets.Deroceras reticulatumcaused more damage than didArion fasciatus.The proportion of leaves damaged by lucerne fiea was highest in the least cyanogenic eultivar but also tended to increase in the most cyanogenic cultivar, confirming a field observation. At high population densities lucerne flea was capable of killing some seedlings but was not tested against established p

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1988.tb01896.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractPhalaris, subterranean clover and white clover were grown together in binary, diallel replacement series mixtures at (day/night) 15/10 or 24/19°C under long‐day conditions, and cut at 2‐ or 4‐weekly intervals. Analysis of white clover mixtures was confined to 15/10°C due to losses of seedlings prior to imposition of treatments at 24/19°C.With white clover at 15/10°X, seedling losses occurred after the first harvest, the greater losses occurring in mixtures where subterranean clover was the major component. The de Wit analyses showed that subterranean clover excluded its companions, whereas phalaris and white clover competed for slightly different niches resulting in over‐yielding. Gleeson McGilchrist analyses showed that subterranean clover and phalaris were more aggressive than white clover under infrequent cutting, but that white clover was more aggressive as a major than as a minor component of a mixture under frequent cutting. Between phalaris and subterranean clover [he pattern of competition at 24/19°C differed from that at 15/10°C only in the more rapid development of subterranean clover and consequent swing to phalaris dominance.We conclude that the seedlings of white clover and subterranean clover are suited to combination with phalaris because phalaris is not too aggressive towards white clover, and is tolerant of the aggressiveness of subterranean clover. The survival of only a few seedlings of white clover in mixtures with subterranean clover may be sufficient for long‐term growth provided some perennation occurs after the senescence of subt

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1988.tb01897.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractTwo experiments investigating the effects of simulated continuous defoliation on white clover development and senescence are described. Stolons growing in boxes in a glasshouse were defoliated repeatedly by hand to simulate different intensities of continuous grazing by sheep. The experiments continued in both instances until eleven leaves had been produced on stolons in the most favourable treatment.It was found that leaf dry matter production was reduced in proportion to the leaf complement of the stolon. Reduction of the leaf complement from two leaves to one leaf led to a reduction in subsidiary branch production of about 25% and an increase in percentage dead stolon from 33 to 44%, If no fully expanded leaves were retained branch production fell to 40% or less of that observed when two leaves were retained.Stolons growing in swards continuously grazed by sheep usually have a green leaf complement varying between zero and two leaves per growing point. The consequences of maintaining different leaf complements in this range are discussed in the light of the current experiments.

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1988.tb01898.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractTwelve cows were used in a cyclic changeover design experiment to examine the effects of feeding fodder beet (variety Kyros) at three levels (0, 2 and 4 kg dry matter (DM) d−1) with two levels of concentrate feeding (4 and 8 kg DM−1). Silage was offeredad libitum.At the start of the experiment the mean number of days after calving was 46 and the mean live weight 516 kg. The experiment consisted of four 3‐week periods with intake and performance measurements during the last week of each period.Anin vitroanalysis of the feeds for the silage, fodder beet and concentrate respectively was: DM (g kg‐−1) 189, 163, 860; crude protein (g kg DM−1) 143,76,201; metabolizable energy (MJ kg DM−1) 104, 133, 13–5.Silage DM intake decreased but total DM intake increased when fodder beet was fed. The DM intakes (kg d−1) for treatments (fodder beet/ concentrate) 0/4, 2/4, 4/4, 0/8, 2/8, 4/8 respectively were: silage DM 91, 79, 78, 83, 70 and 68 (s.e.d. =0.31); and total DM 130, 138, 156, 162, 166, 183 (s.e.d. = 0.36). Feeding fodder beet had no significant effects on milk yield or milk composition, but there was a significant increase in milk protein yield when fodder beet was included in the ration. There were no significant interactions between level of fodder beet feeding and concentrate level. Increasing the level of concentrate feeding led to a highly significant increase in milk yield, milk protein content and yield of milk constituents. The yields for treatments 0/4, 2/4,4/4,0/8, 2/8,4/8 respectively were: milk yield (kg d−1) 206, 204,21 8, 241,235, 244 (s.e.d. = 0–58); fat yield (g d−1) 827, 793, 885, 954, 936, 954 (s.e.d. = 394); and protein yield (g d−1) 622, 628, 679, 774, 777, 814 (s.e.d. = 179). There were no significant differences in milk yield and milk composition when fodder beet was included in the diet which may have been due to the low crude pr

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1988.tb01899.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY