ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1965.tb00388.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

Grazing management should be firmly based on knowledge derived from studies of both animal‐ and plant‐physiology. It is essential to understand both the nutritional needs of the animal and the effect of harvesting procedures on the growth rate of the plant.Animal performance, however, is not simply related to the mean nutritive value of the sward on offer; selective grazing can result in large differences between the latter and the value of the diet actually consumed. Thus it is possible to obtain similar animal growth rules on very different pastures, where grazing pressure is very low, or to obtain different animal performances on pastures which differ little in mean digestibility, but where the herbage is more, or less, ‘available’. It is therefore necessary to understand the relationship between the amounts of herbage on offer, removed and left behind in grazing, and the nutrient intake of the animal.To use biological criteria, such as the quantity of herbage present, in operating grazing methods it is essential that they are expressed in terms which are relevant theoretically and measurable in practice.The results of experimental comparisons of managements can not necessarily be used to judge the usefulness of physiological concepts, since the assumption that such concepts are embodied in the managements is often unjustified. There is, for example, little evidence that continuous and rotational grazing, under conditions of ‘correct’ stocking, result in different frequencies of defoliation of the individual plant uni

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1965.tb00389.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

A brief description of some physiological aspects concerning carbohydrate reserves is given. The concentration of these substances depends on rates of photosynthesis, respiration, translocation and synthesis of structural compounds. Immediately following severe defoliation, current photosynthesis and carbohydrate reserves cannot meet the demand for growth and other fractions (possibly protein) are remobilized. The amount of growth made during the first few days is related to amounts of carbohydrate present but over longer periods other factors dominate. Defoliation also results in large decreases in the rates of root extension and uptake of minerals.

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1965.tb00390.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

It has been found that the rate of herbage production from perennial grass swards, cut at a stage suitable for grazing, is lower in midsummer than in late spring. This occurs even with an abundant supply of water and fertilizer. The growth rate of green material was measured in swards differing in leaf area and light interception, Results did not suggest that higher growth rates could be obtained by attention to this relationship. Examination of the tiller population of grass swards showed that, in summer, herbage yields from cocksfoot and timothy were correlated with the average tiller size. This was not so in either of 2 varieties of perennial ryegrass. During May, June and July there were changes in the erectness of the swards as measured by the proportion of the crop which could be harvested with a mowing machine. This proportion was maximal when the highest rates of production of herbage were recorded. The importance is discussed of the change from a phase when mature tillers are forming inflorescences to one when herbage is derived from young, vegetative tillers formed in the same summer.

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1965.tb00391.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

Study of the growth of an undefoliated stand of Italian ryegrass showed that the yields of leaf blade, leaf sheath, and dead matter remained fairly constant for 10 weeks in winter, although individual tillers produced a new leaf every 16–19 days. From these data it is estimated that approximately 8 lb. of dry matter/acre/day was lost through the death and subsequent decomposition of plant tissue.Investigation of the recovery growth of a closely defoliated perennial ryegrass sward in summer showed that the yields of leaf blade and leaf sheath increased rapidly with time until there was sufficient foliage to intercept virtually all of the noon light and slowly thereafter; whereas the yield of senescent and dead material increased slowly at first and rapidly later. It is suggested that the rate at which dry matter accumulated beyond the stage of complete light interception depended to a large extent upon the rate of tissue decay.Determinations of the composition of the stubble of a perennial ryegrass sward which was leniently defoliated at weekly intervals in late summer showed that the proportion of leaf blade in the material necessary to intercept 90–95% of the noon light decreased with time, whilst the proportion of dead matter increased. It is pointed out that the rate of dry‐matter accumulation was probably affected throughout by factors which determined the rate of decomposition of dead material. The conclusion drawn is that pasture production is likely to be good only when grazing or cutting management ensures that dry‐matter losses by decay are kept to a minimum, whilst gains by photosynthesis continue at a high level. The results of some cutting trials are discussed in thes

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1965.tb00392.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

The effects of 4 levels of applied nitrogen, ranging from nil to a maximum of 417 lb N/ acre/annum, in all combinations with 3 frequencies of defoliation, ranging from 2 to a maximum of 10 cuts per annum, on herbage production from a perennial ryegrass/ timothy/meadow fescue/white clover sward were measured. These treatments were operative for 2J years, and in a subsequent year the residual effect of cutting frequency was tested. Dry‐matter yields of total herbage and of the clover fraction are quoted, together with N yields of total herbage. Yield response to N was higher than in some other experiments in the U. K. Cutting frequency had a very large effect and, in general, the longer the interval between cuts, the higher was the dry‐matter (though not the N) yield. There was a marked interaction between cutting frequency and level of N: at the high cutting frequency, dry‐matter yield increased linearly with increasing level of N; at the medium frequency, response tended to fall off at the highest level of N; at the low frequency, yield declined with increasing level of N beyond 139 lb N per acre per

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1965.tb00393.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

When the rate of dry‐matter production of a grass crop is determined only by the incoming light energy, it increases exponentially until a closed green surface is reached. Thereafter the production is linear for some time, but soon it decreases and finally drops to zero. This decrease is partly caused by an increase in the rate of respiration relative to photosynthesis. However, there are still unknown factors affecting the rate of production, especially in the second half of the season. When a sward receives an optimal supply of water and nutrients the organic plant constituents at a given growth stage remain fairly constant throughout the season. It would be advantageous, however, to harvest grass with a higher sugar and a lower protein content. This seems to give better rumen digestion and, besides, would improve the regrowth of the sward. Since plants with a high rate of dry‐matter production usually have a fairly low reserve level, it is unlikely that selection could provide a strain with both a high reserve level and a high rate of product

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1965.tb00394.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

The botanical changes in a wet (Molinia) and a drier (Nardtts) upland pasture that followed a single defoliation by a forage harvester are briefly described. Without fertilizer the bare and litter‐covered areas were soon recolonized by the original dominants; with lime and fertilizer the recolonization was mainly byAgrostisspp., even whenAgrostiswas a minor element in the original sward. These changes were markedly accelerated by the forage‐harvester treatment. The results of surface seeding after the forage‐harvester treatment are compared with those obtained after rotary cultivation. Contrasting moisture regimes and competitive thresholds led to considerable differences in sward balance and in establishment of sown species, and seeding was successful only on the wetter site. Too rapid regeneration of undesirable remnants was prevalent, but this and other hazards are related to the uneven deposit of litter left by the forage harvester; thick, slowly‐rotting accumulations inhibited the redevelopment of rapidly‐growing species and germination on see

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1965.tb00395.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

Trials are described in which the intake of silage of varying length was determined. The results indicate that a higher voluntary dry‐matter intake occurred as the length of the silage became progressively shorter, but this effect appeared to diminish when the silages were supplemented with concentrates. Data from one trial indicate that reducing the length of hay had no effect on voluntary intake when concentrates were fe

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1965.tb00396.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

The effects of wilting and of various chemical additives on the digestibility and palatability of wet legume silages are reported. These silages showed most of the characteristics associated with the ensiling of wet herbage with a low content of soluble carbohydrate. Digestibility of all silages by wether lambs was low and exhibited little difference that might be attributed to the treatments. The untreated silage or the one sprayed with valeric/isovaleric acid, just before feeding, were more palatable to dairy heifers. Silage consumption was sharply reduced when urea was added during ensiling.

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1965.tb00397.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY