Estimation of the ruminal degradation of forage rape after incubation in nylon bags in the rumen of sheep

The nylon bag technique was used to measure the disappearance of dry matter, nitrogen and non–nitrogenous dry matter from samples of forage rape leaf and stem incubated in the rumen of sheep. Samples were either hand–harvested and chopped or obtained using Iambs with oesophageal fistulae.
Differences were observed in the dry matter and nitrogen contents of oesopha1 fistulae extrusa and cut samples; calculations are presented to suggest that these differences were not due to salivary contamination. Compared with cut samples, oesophageal fistulae extrusa had significantly higher initial disappearance, fractional rate of disappearance and predicted disappearance of both dry matter and nitrogen. Observed disappearances from leaf and stem extrusa after 24 h incubation were: dry matter from leaf 0·898 and from stem 0·832; nitrogen from leaf 0·942 and from stem 0·910. Corresponding values for cut leaf and stem were 0·817, 0·726, 0·883 and 0·849, respectively.
The rumen degradation of protein (nitrogen × 6·25) was computed for all combinations of leaf, stem, cut and extrusa samples for rumen fractional outflow rates ranging from 0·02 to 0·09. Degradation levels computed from cut samples were much less than those based on oesophageal fistulae extrusa and are suggested to be underestimates. Rumen degradation levels for forage rape leaf and stem were very similar and ranged from 0·83 to 0·75 over the above range of fractional outflow rates.     

A COMPARISON OF LUCERNE VARIETIES IN SOUTH-WEST SCOTLAND

Five early, three mid-season and two late varieties of lucerne were grown in drills in a replicated plot experiment at the Hannah Dairy Research Institute in south-west Scotland in the period 1956–59, inclusive. The lucerne was cut three times each year after the year of establishment (1956).
Average yields were 10,200 lb. of dry matter and 1970 lb. of crude protein per acre in the first harvest year, but declined rapidly to 6290 lb. of dry matter and 1190 lb. of crude protein per acre in the third year. On average, the early types of lucerne gave the highest yields of dry matter and crude protein. Over the three harvest years of the experiment, Flandria was the highest yielding variety and New Zealand B the lowest. The distribution of dry-matter yields averaged over all varieties was 44, 29 and 27% for cuts 1, 2 and 3, respectively.
The crude-protein content of the herbage from all the varieties was high, 63% of the values being greater than 19%. Grimm, a late variety, had the highest crude-protein content.
With all varieties tiller density declined rapidly from the first to the second harvest year, but increased again at the third harvest year.
11–34% of the total yield of dry matter in the second harvest year consisted of weed grasses, but this was reduced in the following year by spraying the plots with Dowpon, a selective herbicide.     

LUCERNE STRAIN TRIAL

French, Canadian, U.S.A., German and New-Zealand lucerne strains were compared in a trial under four different cutting treatments from 1951 to 1955 in north-west Norfolk. The French strains W.268 and Du Puits produced the highest yields of dry matter and crude protein, followed by Ile de France, Provence, New Zealand's Marlborough and Germany's Old Franconian Blue and Old Franconian Motley. Rhizoma was the only Canadian strain which produced a high yield of crude protein. The rest of the Canadian and all the U.S.A. strains were inferior yielders compared with those from France. W.268 and Du Puits gave the best relative distribution of dry-matter yield over the season. The highest yield of crude protein and the best distribution of dry-matter and crude-protein yields over the season was given when the first cut was taken at the bud stage and the second cut at 25% flower stage. Cutting treatments with the first cuts taken at the bud stage (early) depressed the growth of weeds more efficiently than cutting treatments with the first cuts taken at the 25% flower stage. Yearly fluctuations in yields over the period of four years were moderate; the majority of strains maintained a high yield into the fifth year.     

PRODUCTIVITY, PERSISTENCE AND RESPONSE TO NITROGEN OF ITALIAN RYEGRASS VARIETIES

The production of six varieties of Italian ryegrass was compared for three years by cutting 5 or 6 times during the growing season. All varieties showed falls in production of dry matter at high and low levels of N fertilization, but New Zealand HI and New Zealand Italian ryegrass showed significantly lower falls and gave top yields over the three years, in spite of severe frost damage in the first two. Crude protein and nitrogen absorption remained high at the lower level of fertilization (174–209 lb N/acre) and showed a fall only in the third year at the high level of N fertilization (348–418 lb N/acre).
The significance of the high response of the New Zealand varieties is discussed.     

SEASONAL PATTERNS OF DIGESTIBLE ORGANIC MATTER AND PROTEIN PRODUCTION FROM GRASSES IN THE NORTH PENNINES

The seasonal pattern of digestible organic matter (DOM) and crude-protein production of Lolium perenne, Cynosurus cristatus, Anthoxanthum odoratum, Festuca ovina and Agrostis stolonifera cut to 3 cm at 6-week intervals was studied at five sites ranging from 49 to 303 m above sea level in north-west Lancashire for the years 1969–70. DOM production declined from 482 g/m² on the lowest site to 220 g/m² on the highest; similarly protein production declined from 142 g/m² to 73 g/m². Small but significant differences in the percentage of crude protein occurred only ia 1970, whereas DOM as a percentage of DM in the various species differed considerably between sites in both years. The significance of the results and the seasonal fluctuations in production are discussed.     

密度和施氮量对雅玉8号青贮玉米产量和品质的影响

研究不同种植密度和施氮水平对雅玉8号产量及品质的影响。结果表明,雅玉8号在四川资阳地区适宜种植密度为90 000株/hm2,最佳施氮量为200 kg/hm2,其地上干物质产量高达23 345 kg/hm2,果穗率为59.93%,粗蛋白含量为75.5 g/kg,粗纤维仅为124 g/kg,粗脂肪、粗灰分、无氮浸出物和钙含量分别为34.6、62.0、598和4.0 g/kg。种植密度和施氮水平对青贮玉米的地上干物质含量、粗蛋白产量及果穗率和粗纤维含量的影响均呈显著水平。     

Degradation of nitrogenous compounds in conserved forages in the rumen of dairy cows

Degradation in the rumen of dairy cows of nitrogenous compounds in 35 grass silages and 12 grass hays was studied by means of the nylon bag incubation technique. Silages varied in dry matter content, crude protein content and date of harvesting; hays varied mainly in crude protein content. Measurements in both forages were washable (W), degradable (D) and undegradable fraction (U) and rate of degradation (ks) of D. W and U were measured as the residue after washing without incubating (W) or after 336 h in the rumen (U). N escape (E) was calculated from these data, assuming a ruminal passage rate of 4·5% per hour.
E (N escape from the rumen) in hays was substantially higher than in silages, mainly because a large proportion of N compounds in silage became soluble during the ensiling process. Of the total variation in E, around 80% could be explained in both forages. In silage, E was positively influenced by dry matter content, negatively by crude protein content and positively by the number of days elapsed since 1 April. This effect of day of harvesting was mainly through an increase of U and may not be beneficial to the animal. In hays crude protein content was the major factor explaining variation in E.     

A COMPARISON OF THE EFFECT OF ITALIAN RYEGRASS AND TALL FESCUE MIXTURES ON THE FOLLOWING CROPS OF KALE AND BARLEY

The effects of preeropping with Italian ryegrass and tall fescue mixtures on marrow-stem kale (1st test crop) and barley (2nd test crop) were measured. Application of N to the grass/clover swards reduced the yield of DM, P, K, Na, Mg, crude protein and also the percentage crude protein in the kale test-crop. Following the tall fescue swards, the yield of DM, P, Na, Ca, Mg and E, crude protein and percentage crude protein in the kale were lower than after the Italian ryegrass swards. These effects were particularly evident in the kale stem. Interactions occurred which involved the method used to establish the herbage mixtures, the application of N to the swards and of fertilizers to the kale. These effects were complex, but the method of sward establishment could clearly affect the following kale crop grown several years later. The influence of grass swards on the second test-crop (spring barley) was much smaller than on kale. Precropping with Italian ryegrass or using a cover crop during grassland establishment reduced 1000-grain weight of barley. The crude protein percentage in barley grain was reduced by the compound fertilizer applied to the previous kale crop, particularly when no cover crop had been used during establishment of the herbage mixtures. The converse of these effects was recorded in the crude-protein percentage of the straw of the barley test-crop.     

Prediction of the nutrient content of botanical fractions from annual legumes by near-infrared reflectance spectroscopy

Procedures used to determine chemical composition and digestible organic matter in dry matter (DOMD) are slow and expensive. The possibility of using near-infrared reflectance spectroscopy (NIRS) as an alternative procedure was investigated with annual legumes. Material from cultivars of Medicago murex, Trifolium balansae, T. resupinatum and T. subterraneum was harvested soon after plants had matured. Samples were sorted into stem, leaf and burr fractions and analysed chemically and by NIRS. Data were then sorted into two similar sets, one of which was for calibration and the other for validation. Data for each chemical fraction, in samples used for calibration, were regressed sequentially against the corresponding reflectance spectral data, the log of there reciprocal of which was transformed to first or second derivatives. Equations of best fit were then used to predict the composition of samples in the validation set.
Standard errors of calibration and validation respectively, expressed as percentages of the mean, were 0·5 and 0·6 for dry matter (DM), 2·0 and 2·6 for organic matter (OM), 4·8 and 4·3 for DOMD, 6·0 and 7·2 for crude protein, 4·1 and 4·4 for acid-detergent fibre (ADF), 2·5 and 3·1 for neutral-detergent fibre (NDF) and 8·9 and 10·9 for lignin.     

A comparison of methods of establishing perennial and Italian ryegrasses

An experiment extending over a 2½-year period from June 1976 to October 1978 assessed the effect on herbage yield of method of establishment, species and level of N application.
Perennial ryegrass cv. Gremie and Italian ryegrass cv. RvP were established by broadcasting or drilling into cultivated ground or by direct-drilling, using a Howard Rotaseeder, into paraquat-sprayed but uncultivated ground. These treatments were combined with annual rates of N application of 0, 120, 240 or 360 kg ha^-1.
Over the experiment drilling into cultivated ground gave the highest yield—3·6 and 4·8% higher than the broadcast and direct-drilled treatments, respectively. Italian ryegrass consistently outyielded perennial ryegrass, with an overall mean dry matter yield advantage of 23·7%. There was no significant interaction between sowing method and species; direct-drilled Italian ryegrass produced a mean yield 17·3% higher than that of drilled perennial ryegrass.     

A comparison of quadrat, capacitance meter, HFRO sward stick, and rising plate for estimating herbage mass in a smooth-stalked, meadowgrass-dominant white clover sward

A single-probe capacitance meter (Pasture Probe), the Hill Farm Research Organization (HFRO) sward stick, a rising-plate meter, and cut quadrats were used to estimate herbage mass of swards that were rotationally grazed by cattle, cattle followed by topping, cattle followed by sheep, or sheep alone during 1989 and 1990 grazing seasons. Mean target pre- and post-grazing herbage masses were 2200 and 1100 kg dry matter (DM) ha⁻¹ respectively. Linear regressions, correlations and scatterplots were calculated relating meter and sward stick readings to herbage mass on an ash-free organic matter basis measured by cutting quadrats of herbage at ground level.
Mean coefficients of variation for quadrat, capacitance meter, sward stick and rising plate were 28·8, 15·5, 27·2 and 27·9% respectively for pre-grazing herbage mass measurements, and 20·2, 10·1, 21·4, and 18·4% respectively for post-grazing measurements. These coefficients indicate that the capacitance meter varied less in estimating pre- and postgrazing herbage mass than the other three methods.
Correlation coefficients relating cut quadrats to capacitance meter, sward stick and rising plate readings were 0·65, 0·70 and 0·72 for pre-grazing, and 0·36, 0·31 and 0·05 for post-grazing herbage mass measurements respectively.
The non-destructive methods provided quick herbage mass estimates at a level of precision adequate for making day-to-day grazing management decisions on farms.     

Effect of supplementation on production by spring-calving dairy cows grazing swards of differing clover content

An experiment was carried out to examine the effect of supplementation on the performance of spring-calving dairy cows grazing swards of differing perennial ryegrass and white clover content. Seventeen heifers and sixty-four Friesian cows in their third to ninth week of lactation were turned out onto one of three pastures with different proportions of perennial ryegrass and white clover. Nine animals on each pasture received either 0, 2 or 4 kg d⁻¹ of a concentrate with a crude protein concentration of 180 g kg⁻¹ dry matter (DM). Prior to grazing, swards contained proportionately 0·01 (L), 0·15 (M) and 0·20 (H) of total DM as clover. During the experiment, grazing pressures were adjusted by movement of buffer fences to maintain compressed sward heights at 6 cm. Samples taken 26 and 68 d after the start of grazing showed little change in the proportion of clover in sward L (< 0·01 and 0·02 respectively), but convergence in the proportion of clover in swards M and L (0·08-0·16 and 0·10-0·15 respectively). Mean daily yields of milk, fat, protein and lactose increased significantly with increased clover content and, even without supplementation, daily yields were 25·4, 0·98, 0·73 and 1·09 kg respectively on sward H. Of the milk components, only protein was significantly increased by increasing sward clover content. The response in milk yield to supplementation was greater on sward L than on swards M and H.     

The effect of defoliation practice in Western Australia on tiller development of annual ryegrass (Lolium rigidum) and Italian ryegrass (Lolium multiflorum) and its association with forage quality

The effect of defoliation on the vegetative, early reproductive and inflorescence stages of tiller development, changes in the dry‐matter yield of leaf, stem and inflorescence and the associated changes in forage quality was determined on plants of annual ryegrass (Lolium rigidum Gaud.) and Italian ryegrass (L. multiflorum Lam.). The field study comprised seventy‐two plots of 1 m × 2 m, sown with one annual ryegrass and seven Italian ryegrass cultivars with a range of heading dates from early to late; defoliation commenced 6 weeks after germination. During the vegetative stage of growth, plots were defoliated when the tillers had three fully expanded leaves (three‐leaf stage). During the early reproductive stage of growth, to simulate a cut for silage, plots were defoliated 6–7 weeks after 0·10 of the tillers displayed nodal development. The subsequent regrowth was defoliated every 3 weeks. Assessments of changes in tiller density, yield and quality were made in the growth cycle that followed three contrasting cutting treatments during the winter–spring period (from 10 July). In treatment 1, this growth cycle (following closing‐up before a subsequent conservation cut) commenced on 7 August following two defoliations each taken when the tillers were at the three‐leaf stage. In treatment 2, the growth cycle commenced on 16 October following: for early‐maturing cultivars, two cuts at the three‐leaf stage, a cut for silage and an additional regrowth cut; for medium‐maturing cultivars three cuts at the three‐leaf stage and a cut for silage; and late‐maturing cultivars, five cuts at the three‐leaf stage. In treatment 3, defoliation up to 16 October was as for treatment 2, but the growth cycle studied started on 27 November following two additional regrowth cuts for early‐ and medium‐maturing cultivars and cut for silage for the late‐maturing cultivars. Tiller development for all cultivars was classified into three stages; vegetative, early reproductive and inflorescence. In treatment 1, in vitro dry‐matter digestibility (IVDMD) and crude protein (CP) content were negatively associated with maturation of tillers. IVDMD ranged from 0·85 to 0·60 and CP ranged from 200 to less than 100 g kg^–1 dry matter (DM) during the vegetative and inflorescence stages respectively. This large reduction in forage quality was due to an increase in the proportion of stem, inflorescence and dead material, combined with a reduction in the IVDMD and CP content of the stem. A high level of forage quality was retained for longer with later‐maturing cultivars, and/or when vegetative tillers were initiated from the defoliation of early reproductive tillers (treatments 2 and 3). However, 15 weeks after the closing‐up date in treatment 1, defoliation significantly reduced the density of inflorescences with means (±pooled s.e_m.) of 1560, 1178 and 299 ± 108 tillers m^–2, and DM yield of inflorescence with means of 3·0, 0·6 and 0·1 ± 0·15 t ha^–1 for treatments 1, 2 and 3 respectively. This study supports the recommendation that annual and Italian ryegrass cultivars should be classified according to maturity date based on the onset of inflorescence emergence, and that the judicious defoliation of early reproductive tillers can be used to promote the initiation of new vegetative tillers which in turn will retain forage quality for longer.     

Preferences of lambs offered Italian ryegrass (Lolium multiflorum L.) and barley (Hordeum vulgare L.) herbage as choices

Partial preference for feeds in ruminants is a well-documented phenomenon although their explanation can be elusive. The hypothesis was tested that sheep offered herbage of two annual grass species differing in chemical composition free-choice would select a diet that would maximize the nutritive value of the diet compared with sheep offered each herbage separately through a greater nutrient balance and synchronization of nutrient release for efficient ruminal microbial function. Fifteen male lambs were placed into metabolic cages, and randomly assigned to three treatments ( n  = 5): Italian ryegrass fresh herbage (treatment R), barley fresh herbage (treatment B) or free-choice Italian ryegrass and barley fresh herbage (treatment RB). Both herbages had similar crude protein concentrations but Italian ryegrass herbage had higher concentration of water-soluble carbohydrates and lower concentration of fibre than barley herbage. Lambs were exposed to the treatments for 15 d. Lambs on treatment RB showed a partial preference of 0·82 (s.e. 0·031) for Italian ryegrass. Lambs on treatment RB had higher intakes of digestible dry matter and higher values for nitrogen retention than lambs on treatment B although similar to that of lambs on treatment R. The results for the dietary choices were not always consistent with maximizing the nutritive value of the diet. Other explanations, such as lambs needed to sample and track the nutritive value of dietary options or there was the development of transient food aversions, were also possible.     

THE RELATION BETWEEN THE CRUDE PROTEIN CONTENT AND THE DIGESTIBLE CRUDE PROTEIN CONTENT OF TROPICAL PASTURE PLANTS

The digestible crude protein percentage (DCP) of 218 different feeds derived from 16 tropical grasses and 8 tropical legumes containing 2·2 to 25·3% crude protein (CP) was Treasured with sheep. DCP was closely related to CP (r =· 0·979) and could be predicted from the equation DCP=O·899 CP-3·25 (SE estimate · 0·84). Predicted values for tropical grasses and legumes were similar to, but more variable than, those calculated from a similar equation derived from temperate pasture species. It was suggested that CP per se is a useful criterion for selecting tropical pasture plants when direct in vivo measurements of DCP cannot be obtained.     

Seasonal changes in the crude protein concentration of mixed swards of white clover/perennial ryegrass grown without fertilizer N in an organic farming system in the United Kingdom

Changes in the crude protein (CP) concentration of white clover and perennial ryegrass herbage from a mixed sward were determined on six sampling dates from May to October in each of 2 years. The swards were grown without fertilizer N in an organic farming system and continuously grazed by dairy cows during the grazing season. The annual mean contents of white clover in the dry matter (DM) of the sward were 272·3 and 307·0 g kg⁻¹ in Years 1 and 2. The mean CP concentrations of the white clover and perennial ryegrass herbage were 251·6 and 151·9 g kg⁻¹ DM in Year 1 and 271·9 and 174·0 g kg⁻¹ DM in Year 2 respectively. The CP concentration of the white clover increased significantly during the grazing season from 220·0 to 284·1 g kg⁻¹ DM in Year 1 and from 269·0 to 315·5 g kg⁻¹ DM in Year 2. In the perennial ryegrass herbage the CP concentration increased from 112·2 to 172·6 g kg⁻¹ DM in Year 1 and from 142·7 to 239·5 g kg⁻¹ DM in Year 2. The rate of increase during the season in the CP concentration of the perennial ryegrass herbage was similar to the rate of increase recorded in the white clover herbage.     

Herbage potassium levels in a permanent pasture under grazing

Herbage potassium levels were measured in 1986 in a permanent pasture under continuous grazing with cattle and receiving 200 kg N ha⁻¹. In April, before grazing started, K concentration in the herbage was relatively uniform across the pasture, with a value of 1·9 ± 0·038% K in the herbage dry matter. In July, a significantly lower concentration of herbage K was found in the grazed areas of the pasture (1·8 ± 0·10%) compared with the level (2·4 ± 0·088%) found in the rejected areas of the sward. The difference between the grazed and rejected areas was similar in September, with 1·6 ± 0·087% and 2·2 ± 0·172% K, respectively, in the herbage dry matter. This result suggests that herbage growth in the grazed areas might have been limited by K supply and highlights the need for more information on the K requirements of grazed grassland.     

How does protein supplementation affect the selectivity and performance of Charolais cows on extensively grazed pastures in late autumn?

Management of beef cows grazing extensively grazed semi-natural pastures in temperate regions in late autumn can require supplements to be offered. The effects of supplementation with soya bean meal on the diet selected by Charolais cows and on their subsequent performance were examined for an 8-week period in late autumn in 2 years. Three groups of eight cows were compared: non-supplemented dry cows (D), non-supplemented (L) and supplemented (LS) lactating cows. The amount of soya bean meal supplement offered per cow was 250 g d⁻¹ in year 1 and 800 g d⁻¹ in year 2. Dietary choices were measured by direct observations and herbage intake was estimated in year 2. Supplementation affected neither diet selection (L: 0·42 vs. LS: 0·43 for the proportion of bites on green patches in year 1; 0·24 vs. 0·22 in year 2) nor daily organic matter intake of herbage (L: 15·6 vs. LS: 15·9 kg d⁻¹), which may have resulted from an adequate crude protein concentration of herbage. The higher total dry matter intake by cows offered the supplement reduced losses in live weight (L: −1212 vs. LS: −828 g d⁻¹; P  < 0·01) rather than increased milk production (L: 5·1 vs. LS: 5·0 kg d⁻¹). This may be linked to the low milk yield potential of the Charolais cows. The use of lactating cows rather than dry cows for pasture management in late autumn would increase the utilization of herbage but a reduction in liveweight losses of cows by supplementation is unlikely to be economic.     

THE EFFECT OF PRE-WILTING HERBAGE ON THE COMPOSITION OF SILAGE AND ITS INTAKE BY COWS

Lucerne was ensiled at various dry matter contents, within the range of 19·8% to 39·6%. An increase was found in lactic acid production, with a consequent decrease in volatile acid and volatile base content, up to the level of 33·9% dry matter.
The dry matter intake of cows was increased by feeding silage with a high dry matter content.     

Identifying suitable temperate grass species and cultural practices for herbage production in the mountain regions of North Vietnam

In North Vietnam, during winter, shortage of herbage constrains the profitability of dairy farming. The first objective of this study was to evaluate the potential of alternative temperate (C₃) forage species, namely common oat ( Avena sativa L.), lop-sided oat ( Avena strigosa Schreb.), Italian ryegrass ( Lolium multiflorum L.) and a commercial forage mixture (Avex), to address the shortage of herbage during winter in the mountain regions of North Vietnam. The second objective was to measure the effects of cultural practices (sowing rate, harvest interval and irrigation level) on yield of dry matter (DM), chemical composition, digestibility of DM and metabolizable energy (ME) concentration of herbage from the best adapted C₃ species previously tested (lop-sided oat). Four experiments were conducted. Oat species proved to be the best adapted species and produced the highest annual yield of herbage (7600 kg DM ha⁻¹) with a high nutritive value. Yields of DM of lop-sided oat were not affected by sowing rate of seed but increased as the length of harvest intervals increased from 30 to 45 and 60 d ( P  <   0·001). Crude protein concentration, digestibility of DM and ME concentration decreased as the harvest interval increased ( P  <   0·01). Irrigation increased the yields of DM of lop-sided oats by 1·3 ( P  <   0·05) but had no effect on the nutritive value of herbage. It is concluded that both common oat and lop-sided oat are suitable species to provide herbage in the winter for the mountain regions of North Vietnam.