摘要:

AbstractA perennial ryegrass sward was managed by continuous stocking with sheep (April–September) for 4 successive years after sowing. The sward was grazed to maintain a leaf (lamina) area index (LAI) close to 1.0. Areas of the sward were released from grazing on three occasions: once during summer in the third year after sowing, and twice during spring and summer in the fourth year after sowing. There were marked changes in the structure and physiology of the continuously stocked sward following release from grazing. After several successive years of continuous stocking, the sward comprised a large population of small tillers and the small LAI resulted in consistently low rates of photosynthesis. Following release from grazing, photosynthesis increased markedly as the LAI increased but this change was associated with the loss of a large proportion of the population of tillers. There were seasonal differences in the pattern of changes in photosynthesis and tiller numbers following release from grazing which were not apparent under continuous stocking. The changes in the structure and physiology of the sward following release from grazing suggest that the net accumulation of herbage in areas of sward from which the animals are excluded, for instance using cages, may be an unreliable estimate of production under continuous stockin

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1984.tb01658.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractAmmonia and sodium hydroxide (NaOH) have been used to improve the dry matter (DM) digestibility of roughages or to conserve them. These treatments have had incidental effects on pH alone or both the pH and nitrogen contents of the roughages. in the present study, the effects of pH and NH4OH on thein vitrodry‐matter digestibility (IVDMD) of eight roughages—four legumes and four grasses—were investigated. The pH levels of approximately 5, 7, 9 and 12 were achieved by adding appropriate amounts of NH4OH or NaOH and H2SO4. Nitrogen levels of approximately 20, 30, 40 and 50 g kg−1on a DM basis were obtained by adding NH4OH. Results of a multiple regression showed that increasing the pH caused a linear increment in IVDMD and that the added NH4OH reduced the increment of IVDMD. The effects of both pH and N on IVDMD were found to be specific to the individual roughage; the response of grasses to both pH and NH3was greater than that of

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1984.tb01659.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractThe results or estimations ofin vitrodigestibility of three standard herbage samples, analysed weekly over about 48 weeks per year, have been examined using time‐series methods of Box and Jenkins to separate seasonal and non‐seasonal trends. The study includes data from March 1971 to February 1981. The dominant feature of variability is the seasonal component with a cycle of 52 weeks; no other significant cycles of longer periods were detected. The model of Box and Jenkins (1976) was found to be the most appropriate in describing the three series. A decrease in thein vitrodigestibility of the low standard, which is 10 years old, occurred over the last year or so, although the reasons for this apparent storage effect are unkn

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1984.tb01660.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractMasham ewes were stocked at 12(L), 16(M) or 20 (H) ewes ha−1, with 1·8 lambs per ewe on average, on two blocks (A and B) in both 1976 and 1977. Silage was offered at pasture to the ewes in early lactation and as stocking rate increased from 12 to 16 and then 20 ewes ha−1, 47, 73 and 100 kg DM per ewe was consumed respectively. Silage was cut mainly in the autumn and 179, 100 and 9 kg per ewe was made for L, M and H respectively. More variation between treatments was measured in net herbage accumulation in summer than spring and 11·4, 10·0 and 9·7t DM ha−1was grown over the whole season for L, M and H respectively as a mean of both years.High intakes of herbage OM were measured with values up to 40 g per kg live weight for BL lambs in 1976. Rapid lamb growth was achieved. There were effects of stocking rate on lamb performance and for L, M and H the respective growth rates to 4 weeks were 266, 248 and 247 g d−1; growth rates to sale were 274, 263 and 252 g d−1; days to sale were 124, 126 and 129; mean carcass weights were 17·7, 17·1 and 16·7 kg. Most ewes lost weight in early lactation, especially AH and BH in 1976, but there were no stocking rate effects on ewe weigh

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1984.tb01661.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractA randomized block experiment was conducted to compare unwilted and wilted grass silages and the effects of the feed additive monensin sodium on the silage intake and performance of finishing beef cattle. Two regrowths from a predominantly perennial ryegrass (cv. S24) sward were ensiled either without wilting or after field wilting for 3 d (dry matter (DM) concentrations 161 and 266 g kg−1respectively). Both silages were treated with formic acid (2·6 and 30 litre t−1respectively) and were well preserved. The silages were offeredad libitumto forty‐eight Charolais‐cross cattle (thirty‐two steers and sixteen heifers, mean initial live weight 351 kg) for 145 d. All animals received 2·2 kg concentrates per head daily and half of those on each silage treatment received in addition 200 mg monensin sodium per head daily. Silage DM intake was 5.04, 504. 5·48, 5·63 ± 0.134 kg d−l; fasted liveweight gain was 0·69, 0·77. 0·64 and 0·73 ± 0.033 kg d−land carcass gain was 0·47, 0·50, 0·40 and 0·45 ± 0·020 kg d−1for the unwilted silage without and with monensin and the wilted silage without and with monensin respectively. It is concluded that wilting grass of low DM concentration for 3 d prior to ensiling reduced the performance of finishing beef cattle below that obtained from well‐preserved unwilted silage in spite of a higher DM intake being achieved with the wilted silage. The inclusion of monensin sodium in a silage‐based diet increased performance without

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1984.tb01662.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractIn view of the revived interest in sainfoin, an economic assessment of the prospects for an expansion of its area in Britain has been attempted. It is estimated that potentially it could be grown on 950 × 103ha of the agricultural area of England and Wales, though it is unlikely in the near future that it would exceed 20 × 103ha, even if economic conditions were favourable. Comparison of the energy and protein yields of sainfoin, red clover and lucerne under conservation management indicates that one of the attractions of sainfoin is its high protein content. However, an assessment of the costs of production and utilization of sainfoin indicate that, for it to be a more widely used legume, sustainable dry matter (DM) yields would need to be increased by 35% to about 11.5 × 103kg DM ha−1. At the same time, although growing sainfoin as a mixture with grass appears to improve the economic attractiveness of the crop, silage production costs (kg DM)−1are still about 15% lower on pure grass swards. However, trials in the UK, Canada and Rumania have shown that, compared to current UK levels, sainfoin yields can be significantly inc

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1984.tb01663.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractSalts of formic, acetic and propionic acids and glutaraldehyde were subjected to an assay with representatives of the major groups of silage micro‐organisms at pH 4·0, 4·5, 5·0 and 6·0. The antimicrobial spectra of the salts suggested that they are most effective against the least desirable components of the bacterial flora of silage, coliforms, Clostridia and bacilli, and would create conditions for a desirable fermentation in practice. In many instances the activity of the salts was better than the corresponding free acid and it was postulated that, if supplemented with acid, aerobic stability of silage might also be improved. Glutaraldehyde, whilst being less selective as an antimicrobial agent, possesses properties which would encourage a lactic‐acid fermentation in

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1984.tb01664.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractTwo experiments are described in which twenty‐four spring‐calving Dutch Friesian cows were allocated between six grazing treatments (two levels of daily herbage allowance × three levels of daily concentrate intake) in a 2 × 3 factorial design. The swards consisted predominantly of perennial ryegrass. A two‐machine sward‐cutting technique (with correction for herbage accumulation during grazing) was used for estimating herbage intake by cows which grazed swards for 3 or 4d. Experiment 1 was carried out for 16 weeks of the grazing season of 1981 and experiment 2 for 18 weeks in 1982.Daily herbage OM allowances in both experiments were 16 and 24 kg per cow above 4 cm cutting height. Daily concentrate OM intake ranged from 0.8 to 5.6 kg per cow. The effect of concentrates on herbage intake differed significantly between allowances. At the low allowance level and at daily concentrate OM intakes of 0.8, 3.2 and 5.6 kg per cow daily herbage OM intake was 10.9, 10.6 and 10.4 kg per cow respectively and the mean substitution rate of herbage by concentrates was only 0.1. At the high allowance level and at daily concentrate OM intakes of 0.8, 3.2 and 5.6 kg per cow daily herbage OM intake was 14.8, 13.6 and 12.4 kg per cow respectively and mean substitution rate was 0.5 kg herbage OM (kg concentr

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1984.tb01665.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractPrevious results with red clover (Trifolium pratense) leaflets, leaf petioles and stems indicated that the epidermis continued to impose a barrier to water loss at low water contents. Further experiments with red clover leaf petioles and stems suggest that cuticular wax is the epidermal component concerned and that treatments which remove or merely modify this will also increase drying rate. However, when treatments to reduce epidermal resistance were applied to pseudostems and flowering stems of Italian ryegrass (Lolium multiflorum) the initial increase in drying rate produced was not sustained at low water contents. The pseudostems consisted of three layers of leaf material rolled one within the other and the true flowering stems were surrounded by one leaf sheath. Their pattern of response to treatments suggested that these affected only the outer sheath, which produced an initial acceleration in drying rate, but that this was not sustained after the outer sheath was dry because the lower untreated layers dried in a similar way to untreated controls.The results suggest the possibility of devising practical treatments to increase drying rate at low water contents with crops containing a high proportion of leaf or stem not surrounded by leaf sheath. Devising such treatments for crops with a high proportion of grass pseudostem or flowering stem surrounded by leaf sheath will be considerably more difficult.

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1984.tb01666.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractFormic acid, sodium diacetate, propionic acid and two of its ammonium salts, ammonium isobutyrate and tributyl phosphate, were examined for their antimicrobial effects with cultures of micro‐organisms typical of the microflora of moist hay. The assays, which were conducted at pH 5, 6, 7 and 8, revealed that all potential preservatives discriminated against actinomycetes in particular and were least effective against fungi. In addition, it was apparent that antimicrobial properties were enhanced under slightly acid conditions and for this reason the use of mixtures of organic acids and salts in commercial hay preservatives is justified. Tributyl phosphate not only had the strongest antimicrobial properties of the compounds tested but was also the least affected by p

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1984.tb01667.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY