Comparison of feed intake,body weight gain,enteric methane emission and relative abundance of rumen microbes in steers fed sainfoin and lucerne silages under western Canadian conditions

Beef cattle are major contributors of enteric methane (CH₄) emissions in Canada. Feeding forages containing condensed tannins (CT) has been suggested as a means of reducing enteric CH₄ emissions and improving production efficiency. Sainfoin (Onobrychis viciifolia) is one of the CT‐containing legumes, which has also been recognized to have several additional beneficial properties. This study compared sainfoin silage (SS) and lucerne (Medicago sativa) silage (LS) with respect to animal performance, enteric CH₄ production, abundance of selected rumen microbes and selected serum parameters in yearling steers during a Canadian winter. Sainfoin silage in our study contained approximately 12 g CT kg^?1 dry matter (DM), a level which did not adversely affect silage palatability as steers fed SS experienced higher DM intake. However, animals fed LS and SS had similar body weight gain over the course of the trial. Feeding SS resulted in lower blood urea nitrogen concentrations and relative abundance of methanogenic archaea in rumen fluid. Yet, microbial population shifts fell short of exerting significant influence on enteric CH₄ emissions. This study suggests that under western Canadian growing and animal‐rearing conditions, sainfoin is not yet competitive with lucerne forage with respect to enteric CH₄ emissions or animal productivity warranting further research and development.     

Fermentation and chemical composition of high‐moisture lucerne leaf and stem silages harvested at different stages of development using a leaf stripper

Lucerne (Medicago sativa L.) requires four or more cuttings at early bud stage per growing season to optimize the amount of crude protein and digestible fibre for feeding high‐producing dairy cows. However, there is potential to generate a nutrient‐dense feed from lucerne regardless of developmental stage by harvesting its protein‐rich leaves separate from its fibrous stems. In order to determine whether fractionated lucerne can be effectively ensiled under high‐moisture conditions and be nutritionally competitive with wilted whole‐plant silage, leaf and stem fractions, harvested at three developmental stages (early bud, 10%–20% bloom and >50% bloom), were directly ensiled in mini‐silos. At day 0, 1, 3, 21 and 140 of ensiling, silages were analysed for protein and non‐protein nitrogen fractions as well as their fermentation products and carbohydrate composition. Silages from unwilted leaves and stems were more heterofermentative than wilted whole‐plant silages; their fermentation shifted from primarily lactic acid to acetic acid production after 21 days. In leaf silages, the high degree of protein degradation into non‐protein nitrogen (~55%) was most likely due to fermentation quality. Nevertheless, at 140 days of ensiling, leaf silages had 21%–25% higher (p < 0.01) available protein (peptide amino acids, soluble and insoluble protein) content than wilted whole‐plant silages, regardless of developmental stage. Achievement of a more rapid pH decline and improved fractionation may further increase the nutritional value of leaf silages.     

Effect of stage of maturity of whole-crop barley on intake and liveweight gain by dairy steers differing in initial live weight

The effect of maturity at harvest of whole-crop barley for ensiling on intake and liveweight gain of dairy steers differing in initial live weight (LW) was evaluated in an experiment over two years. Light (104–120 kg) and heavy (402–419 kg) dairy steers were fed diets containing predominantly whole-crop barley silage harvested at the milk stage [dry matter (DM) content of 284 g kg⁻¹ and neutral-detergent fibre (NDF) concentration of 526 g kg⁻¹ DM] or the dough stage of maturity (DM content of 328 g kg⁻¹ and NDF concentration of 445 g kg⁻¹ DM) and supplemented with up to 1 kg of concentrate. Dry matter intake (g kg⁻¹ LW) was higher for whole-crop barley harvested at the dough stage than at the milk stage of maturity and the difference was greater in heavy than in light steers ( P <  0·001). Liveweight gain was higher and feed conversion ratio was lower for dough-stage compared with milk-stage silage ( P  <   0·05) but there was no interaction with size of steer. Whole-crop barley harvested at the dough stage of maturity promoted higher liveweight gains in dairy steers compared with whole-crop barley harvested at the milk stage due to a higher DM intake.     

Effectiveness of chopped lucerne hay as a moisture absorbent for low dry‐matter maize silage: Effluent reduction,fermentation quality and intake by sheep

This study determined effects of addition of lucerne hay (LH) as moisture absorbent on effluent reduction, fermentation and subsequent intake of maize (corn) silage by sheep. Treatments included maize forage ensiled without LH (LH0), with 50 g/kg LH (LH5) and with 100 g/kg LH (LH10) on a fresh weight basis. Silages were made in 150‐kg bags in triplicate. Upon opening, representative samples from each bag were taken twice weekly during a feeding trial and used for laboratory analyses in a completely randomized design. Silages were fed ad libitum to six ewes in a duplicated 3 × 3 Latin square design with 21‐day periods for intake and digestibility determination. Lucerne hay incorporation linearly increased DM, ash, water‐soluble carbohydrates, buffering capacity and pH of silages, while it linearly decreased ammonia nitrogen, acetic acid and ethanol concentrations (p < .05). Effluent volume linearly decreased from 33 ml/kg in LH0 to 0.8 ml/kg in LH10. Addition of LH resulted in a linear increase in intakes of organic matter and fibre in ewes, while digestibilities of these nutrients linearly decreased (p < .05). Lucerne hay addition improved fermentation parameters and resulted in increased intake of maize silage without having negative impact on aerobic stability.     

Fermentation dynamics and bacterial diversity of mixed lucerne and sweet corn stalk silage ensiled at six ratios

The fermentation dynamics and bacterial diversity of mixed lucerne (LU) and sweet corn stalk (SS) silage ensiled at six ratios were evaluated. LU and SS, harvested at 187 and 222 g/kg dry matter, respectively, were chopped to a length of about 1 cm and mixed in the fresh weight proportions of 10:0, 8:2 (Mix 1), 6:4 (Mix 2), 4:6 (Mix 3), 2:8 (Mix 4) and 0:10. Silos of each ratio were prepared in triplicate and stored at ambient conditions for 5, 10, 15, 30 and 65 days. The fermentation profile of silage during storage was determined at each point, and the bacterial diversity of silage stored for 65 days was analysed by high‐throughput sequencing. The silages with more SS inclusion in the forage mixtures were higher in lactic acid and lower in butyric acid and ammonia N, regardless of storage time. After 65 days of storage, Lactobacillus (relative abundance, 91.36%–95.86%) dominated the bacterial community in Mix 3, Mix 4 and SS silages, whereas the community composition in LU, Mix 1 and Mix 2 silages was complex, mainly consisting of Lactobacillus (45.48%–61.01%), Enterobacter (11.09%–19.57%) and Weissella (10.44%–14.13%). Inclusion of SS significantly enhanced the fermentation characteristics, and remarkably improved the bacterial community structure, reflected by increasing the relative abundance of Lactobacillus and reducing the relative abundance of Enterobacter and Pantoea. The fermentation quality was better when LU was ensiled in a mixture with ≥ 40% SS.     

The liveweight gain of Limousin × Friesian heifers grazing perennial ryegrass/white clover swards of different clover content and the effects of their grazing on sward botanical composition

An experiment was carried out in 1992 and 1993 to examine the effect of white clover content of perennial ryegrass/white clover swards on the performance of Limousin × Friesian heifers. Swards with low (L), medium (M) and high (H) white clover contents were established and managed by continuous variable stocking. A compressed sward height of 5·5 cm was maintained using a buffer fence to vary plot areas, with herbage surplus to grazing requirements cut, removed and yields measured. The mean white clover proportions for treatments L, M and H were 0·02, 0·19 and 0·18 in 1992 and 0·13, 0·16 and 0·31 in 1993 respectively. White clover contents of the swards reached a maximum in August and September, and differences between treatments diminished. There was no significant difference between treatments in the content of white clover in the swards in autumn 1993.
Liveweight gains of heifers increased asymptotically with increasing white clover content of the sward. Below a white clover herbage mass of 300 kg DM ha^–1, there was little effect on liveweight gain, which was 0·70 kg day^–1 over the grazing season. Between 400 and 450 kg DM ha^–1 white clover, liveweight gains were 0·85–0·90 kg day^–1. While clover content of the sward did not significantly affect utilized metabolizable energy output; the mean output over the grazing season in the two years from liveweight gain and herbage yield was 78 GJ ha^–1. It is suggested that, using this grazing system, white clover reached an equilibrium with a mean herbage mass of about 400 kg DM ha^–1 over the grazing season.     

Effects of feeding clover silages on feed intake, milk production and digestion in dairy cows

Silages were made from pure crops of perennial ryegrass, red clover and white clover over 2 years. In all but one case the silage was stored as bales. A silage additive specially adapted for bales (Kofasil Ultra^TM) was used for all silages and they were all of good hygienic quality. The additive contained sodium nitrite, hexamethylene, tetraamine sodium bensoate and sodium propionate. The silages were offered ad libitum, either pure or mixed [grass/clover 0·50/0·50 on a dry‐matter (DM) basis] with a fixed amount (8 kg) of concentrate. Two experiments, one in each year, were performed with high‐yielding multiparous dairy cows in mid‐lactation, and both rumen‐cannulated and intact cows were used. The experiments were carried out using an incomplete changeover design with fifteen cows and five treatments each year. The cows consumed large quantities of these silages (12·7–16·3 kg DM per cow per day). The highest intakes were obtained when the red clover and the 0·50 red clover:0·50 perennial ryegrass silage diets were offered. However, there was a difference between years. In year 1, 0·50 red clover:0·50 perennial ryegrass and 0·50 white clover:0·50 perennial ryegrass silage diets showed the highest intakes while pure perennial ryegrass and white clover silage diets gave lower intakes. In year 2 the highest intake of silage was obtained when the diet containing silage from red clover from a second cut was offered, while the silage from red clover from a first cut gave the lowest intake. The voluntary intakes of silages from white clover and perennial ryegrass were intermediate. No cases of bloat or other digestive disturbances were observed. Milk yield was significantly lower for the perennial ryegrass silage diet compared with all other diets in year 1. In year 2 milk yield was highest for the white clover silage diets and lowest for the red clover silage diets from both cuts. In year 1 there were relatively small differences in milk composition while in year 2 milk fat content was significantly lower with white clover silage diet and milk protein content was significantly higher with the perennial ryegrass diet. The overall conclusion from these experiments was that cows were able to consume large quantities of pure legume silage without serious disturbance to their metabolism. Differences in measurements of rumen metabolism were found between diets and especially between years. Milk production differences appears to be coupled to both differences in rumen physical characteristics, such as passage rate and particle size as well as differences in volatile fatty acid production in the rumen.     

Proteolysis and in situ ruminal degradation of lucerne ensiled with Cistus ladanifer tannins

The effects of ensiling lucerne with graded inclusion of Cistus ladanifer condensed tannins (CT) on in silo fermentative parameters, in vitro organic matter digestibility (IVOMD) and on in situ rumen degradability of dry matter (DM) and crude protein (CP) were studied. Lucerne forage ( Medicago sativa subsp. sativa ) was sprayed with different solutions of C. ladanifer CT extract in 60 ml of water in order for dose 0 (control), 40 (L40), 80 (L80) and 120 (L120) g of CT per kg of lucerne DM and was ensiled in lab‐scale silos. After 35 days, the silages were analysed for chemical composition, and the in situ ruminal degradability was determined in rams. The inclusion of CT in the silages caused an important dose‐dependent reduction in soluble‐N, NH₃‐N and a large increase in true protein content and N bound with neutral detergent fibre (NDF‐N), which indicates an effective proteolysis reduction during ensiling. Also, the rumen undegradable protein (RUP) increased linearly (P < 0.01) with CT inclusion. However, a linear decrease (P < 0.02) of 5%, 13% and 22% of IVOMD was observed for the silages L40, L80 and L120 respectively. The results obtained suggest that C. ladanifer CT can be used as silage additives to reduce proteolysis of high‐protein forages during ensiling. A level of CT of 40 g/kg DM seems to be the best compromise between the gains achieved by the protection of CP degradation in silo and in the rumen and the losses associated with the depression of the digestion and absorption.     

Effects of two mixtures of perennial ryegrass cultivars with contrasting heading dates, and differing in spring-grazing frequency and silage harvest date, on characteristics of silage from first-cut swards

This experiment quantified the effects of: (i) heading date of perennial ryegrass, (ii) grazing frequency in spring and (iii) date of silage harvest, on the ensilability of herbages harvested for silage, and on the conservation and estimated nutritive value of the resultant silages. Replicated field plots with two perennial ryegrass mixtures (intermediate‐ and late‐heading cultivars) were subjected to three spring‐grazing regimes (no grazing, grazing in late March and grazing in both late March and late April) and were harvested on four first‐cut harvest dates between 20 May and 21 June. Herbage from each of the four replicates of these 24 treatments was precision‐chopped and ensiled unwilted and with no additive in laboratory silos. Herbage from the sward with the intermediate‐heading cultivar had a higher (P < 0·001) dry‐matter (DM) content and buffering capacity than that from the late‐heading cultivar, whereas water‐soluble carbohydrate concentrations increased (P < 0·001) with more frequent grazing in spring. Later harvesting enhanced herbage ensilability through an increased (P < 0·001) DM content and reduced (P < 0·001) buffering capacity and pH. Fermentation profiles of the silage were not markedly influenced by the cultivar mixture used but grazing in both late March and late April resulted in a more extensive fermentation with the acids produced increasingly dominated by lactic acid. The concentrations of acetic acid, and to a lesser extent, ethanol declined as silage harvest date was delayed. Overall, the relative effects of grass cultivar mixture were smaller than those of spring‐grazing treatment or silage‐harvesting date although on any given harvest date the herbage from the intermediate‐heading cultivar mixture was easier to preserve as silage than herbage from the late‐heading cultivar mixture. Delaying the harvesting of the late‐heading swards by 8 d removed the differences related to growth stage in buffering capacity, pH and DM content.     

Intake characteristics of perennial ryegrass varieties when grazed by yearling beef cattle under rotational grazing management

Four intermediate‐heading perennial ryegrass (Lolium perenne L.) varieties, which in previous studies had been associated with high‐ or low‐intake characteristics when swards containing them had been continuously stocked with sheep, were sown as monocultures. They were rotationally grazed, using 1‐d paddocks, with core groups of four yearling Simmental × Holstein beef heifers in 2002 and 2003 and ingestive and ruminative behaviour, and sward factors, were measured. There were two diploid (Belramo and Glen) and one tetraploid (Rosalin) perennial ryegrass varieties and one tetraploid hybrid (Lolium × boucheanum Kunth) (AberExcel) variety. Intake rate (IR) was significantly higher in August 2003 for heifers grazing Glen than those grazing Belramo [27·5 vs. 20·6 g dry matter (DM) min^?1; P = 0·019], but there were no significant differences between varieties in two other measurement periods. This is in contrast to previous results with sheep when IR were significantly higher for Glen than Belramo and for AberExcel than Rosalin. Total jaw movement rates during grazing were significantly higher for heifers on the tetraploid swards than those on the diploid swards (87·7 vs. 83·6 jaw movements min^?1; P = 0·023) in September 2002. Ruminating time was significantly lower for heifers on the tetraploid swards than those on the diploid swards (453 vs. 519 min 24 h^?1; P = 0·012) in July 2002. Digestibility of grass snips was significantly higher on the tetraploid than the diploid swards [697 vs. 680 g digestible organic matter (DOM) kg^?1 DM; P = 0·042] in September 2003 and, within diploids, was significantly higher for Glen than Belramo (696 vs. 663 g DOM kg^?1 DM; P = 0·014). There were significant differences in sheath tube and leaf lengths and in the population density of tillers between and within ploidies, which might have been expected to have influenced intake characteristics, but this was not generally found under rotational grazing with cattle. In order to separate the effects of defoliation interval from those of grazing style of the different ruminant species, it is suggested that grass variety evaluations using continuously stocked cattle swards are required.     

The effect of stage of perennial ryegrass maturity at harvesting, fermentation characteristics and concentrate supplementation, on the quality and intake of grass silage by beef cattle

Abstract Two experiments were carried out in consecutive years to examine the influence of cutting date and restricting fermentation by carboxylic acid treatment on the nutrient intake from grass silage by beef cattle. In year 1, four cutting dates during July and August after a primary growth harvest and, in year 2, five cutting dates of primary growth between mid‐May and early July were examined. Herbage was ensiled either untreated or treated with high levels of acid additive (‘Maxgrass’, mean 8·6 l t^?1). Ninety‐six (year 1) or forty‐eight (year 2) continental cross steers were used in partially balanced changeover design experiments with each silage type either unsupplemented or supplemented with 4·5 (year 1) or 5·5 (year 2) kg concentrates head^?1 d^?1. Silage digestibility declined significantly between initial and final harvest dates (P < 0·001), whereas silage dry‐matter (DM) and digestible energy (DE) intakes were significantly higher in the initial compared with final harvest dates in both years of the study (P < 0·01). Similarly, silage DM and DE intakes, and total DM intakes, of acid‐treated and unsupplemented silages were greater than those of untreated and concentrate supplemented silages, respectively (P < 0·001). The results indicate that earlier cutting dates, and addition of acid to herbage before ensiling, can increase silage DM intake by beef cattle.     

Species composition of ryegrass (Lolium perenne) and tall fescue (Festuca arundinacea) mixtures using various combinations of n-alkanes

This study was conducted to evaluate the reliability of the n‐alkane technique for estimating the species composition of Lolium perenne (ryegrass, L) and Festuca arundinacea (tall fescue, F) mixtures. Samples of L and F were collected in May (period 1) and June 2003 (period 2) on mono‐specific swards that were maintained at a height of 9 cm. Seven sets of mixtures containing controlled proportions of L and F were then prepared: 1·00:0, 0·80:0·20, 0·60:0·40, 0·50:0·50, 0·40:0·60, 0·20:0·80 and 0:1·00 of L:F, respectively, in the mixture. The proportion of each species in the mixtures was estimated from measured n‐alkane concentrations, and then compared with the actual known proportion. Various n‐alkane combinations were tested and compared to establish which combination gave the best estimate. Total n‐alkane concentrations, and especially C₂₉‐ and C₃₁‐alkane concentrations, were higher in period 1 than in period 2 for both species. The best n‐alkane combination varied between periods, as did the effectiveness of C₂₉‐alkane in discriminating between L and F. The species composition of the mixtures was satisfactorily estimated for the majority of n‐alkane combinations, providing the combination included n‐alkanes with contrasting profiles between both species. A systematic overestimation of the proportion of ryegrass was observed for the 0·50:0·50 mixture.     

Amount and quality of grass harvested for first-cut silage for differing spring-grazing frequencies of two mixtures of perennial ryegrass cultivars with contrasting heading date

There are potential advantages and disadvantages associated with grazing spring perennial ryegrass swards designated for first‐cut silage. These may differ for intermediate‐heading (0·50 ear emergence in the second half of May) and late‐heading (0·50 ear emergence in the first half of June) cultivars. The interactions between cultivar type, spring‐grazing frequency, silage‐harvest date and year were examined in an experiment with a randomized complete block (n = 4) design with a factorial arrangement of treatments, conducted in Ireland. The factors were (i) two perennial ryegrass mixtures: intermediate‐ vs. late‐heading cultivars, (ii) three spring‐grazing regimes: no grazing, grazing in mid‐March or grazing in both mid‐March and mid‐April, (iii) four first‐cut silage‐harvest dates that were at c. 10‐d intervals from 19 May and (iv) 2 years (1998 and 1999). The effects of cultivar mixture on herbage mass of the swards in spring were small and not statistically significant. The late‐heading cultivars provided lower amounts of herbage dry matter for harvesting for first‐cut silage but herbage with higher in vitro organic digestibility values compared with intermediate‐heading cultivars. To achieve the same amount of herbage for silage, the late‐heading cultivars needed to be harvested 8 d later than the intermediate‐heading cultivars. Even with this delay in harvest date, the late‐heading cultivars had higher in vitro organic digestibility values than the intermediate‐heading cultivars. The late‐heading cultivars could be harvested up to 30 d later and produce a higher amount of herbage for first‐cut silage with similar digestibility values compared with the intermediate‐heading cultivars.     

Effect of long-term changes in relative resource availability on dietary preference of grazing sheep for perennial ryegrass and white clover

Three replicate paddocks, each of 0·235 ha, containing adjacent monocultures of perennial ryegrass or white clover [50:50 by ground area, 6 cm sward surface height (SSH) at start of experiment] were continuously stocked with three yearling and four mature non-lactating, non-pregnant Scottish halfbred ewes for 12 weeks. Herbage intake, grazing behaviour and dietary selection were measured on seven occasions. Clover SSH declined rapidly over the first 5 weeks then stabilized at 1·2–1·6 cm, whereas perennial ryegrass SSH rose slightly initially, then declined gradually. Animals initially included proportionately c . 0·6 white clover in their diet but, by the end of the experiment, this had fallen to 0·3. Total daily herbage intake declined over the 12 weeks from 1·8 kg dry matter (DM) day^–1 at the start to 1·0 kg DM day^–1. Total grazing time increased from 561 min day^–1 to 649 min day^–1 at the end of the experiment. The results suggest that, despite overall herbage depletion and a greater depletion of white clover than perennial ryegrass as a result of the initial partial preference for white clover, the animals traded-off a reduced total intake and an increased grazing time in an attempt to maintain their initial preferred dietary composition.     

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.     

Apparent digestibility and nitrogen utilization of diets based on maize silage harvested at three stages of maturity and fed to steers

Advancing maize crop maturity is associated with changes in ear‐to‐stover ratio which may have consequences for the digestibility of the ensiled crop. The apparent digestibility and nitrogen retention of three diets (Early, Mid and Late) containing maize silages made from maize of advancing harvest date [dry matter (DM) contents of the maize silages were 273, 314 and 367 g kg^?1 for the silages in the Early, Mid and Late diets respectively], together with a protein supplement offered in sufficient quantities to make the diets isonitrogenous, were measured in six Holstein–Friesian steers in an incomplete Latin square design with four periods. Dry‐matter intake of maize silage tended to be least for the Early diet and greatest for the Medium diet (P = 0·182). Apparent digestibility of DM and organic matter did not differ between diets. Apparent digestibility of energy was lowest in the Late diet (P = 0·057) and the metabolizable energy concentrations of the three silages were calculated as 11·0, 11·1 and 10·6 MJ kg^?1 DM for the Early, Medium and Late diets respectively (P = 0·068). No differences were detected between diets in starch digestibility but the number of undamaged grains present in the faeces of animals fed the Late diet was significantly higher than with the Early and Mid diets (P = 0·006). The apparent digestibility of neutral‐detergent fibre of the diets reduced significantly as silage DM content increased (P = 0·012) with a similar trend for the apparent digestibility of acid‐detergent fibre (P = 0·078). Apparent digestibility of nitrogen (N) was similar for the Early and Mid diets, both being greater than the Late diet (P = 0·035). Nitrogen retention did not differ between diets. It was concluded that delaying harvest until the DM content is above 300 g kg^?1 can negatively affect the nutritive value of maize silage in the UK.     

Optimal harvest timing vs. harvesting for animal forage supply: Impacts on production and quality of lucerne on the Loess Plateau,China

The current promotion of larger areas of lucerne (Medicago sativa) production on the Loess Plateau in China prompted this study, which investigated lucerne harvesting practices by farmers and the scope for improved harvest yield and quality by optimizing harvest date, interval and height above ground. On-farm surveys were conducted to document the dominant harvesting practices used by farmers and their perceptions of barriers to adoption of alternative harvesting practices. In districts with less emphasis on livestock, less labour and inadequate facilities to store conserved lucerne, smaller areas of lucerne are grown and it is often harvested daily to meet demand from penned livestock. The consequence is that much of the lucerne is harvested either before or after flowering, resulting in suboptimal yield of biomass and crude protein. Field experiments conducted at low and high rainfall locations on the Loess Plateau over three seasons showed that delaying the start to harvest until after mid-June (the date of first flowering), while not affecting total biomass harvested for the season, does reduce leaf biomass harvested and hence crude protein concentration and yield. Lower crude protein is a consequence of a decline in both leaf percentage in harvested biomass and stem nitrogen concentration. Commencing harvests well before flowering with short (3 week) harvest intervals also penalized total and leaf biomass harvested. Raising cutting height from ground level (current farmer practice) to 50 mm (likely with the advent of mechanized harvesting) did not penalize harvested total or leaf biomass.     

Influence of herbage species, cultivar and cutting date on fatty acid composition of herbage and lipid metabolism during ensiling

The fatty acid (FA) concentration of herbage and lipid metabolism in silage, mainly oxidation and lipolysis, of different species (perennial ryegrass, red clover and white clover) and three cultivars of white and red clover at three cutting dates in the growing season (April, July and October) were studied. FA concentration and composition was strongly affected by species and cutting date. Perennial ryegrass had lower concentrations of C16:1, C18:0, C18:1 and C18:2 than red and white clover. Within red and white clover, the effect of cultivar was small. Oxidation of C18:3 during wilting was different between species and cutting date despite similar wilting conditions. Lipolysis in silage was also influenced by cutting date, species and to some extent by cultivar. Furthermore, in some cuts silages of red and white clover displayed a lower lipolysis than silage of perennial ryegrass. On average, over the three cutting dates proportionately 0·903, 0·864 and 0·857 of the membrane lipids in perennial ryegrass, red clover and white clover were hydrolysed during ensiling. In red clover this could be due to the lipid-protecting properties of polyphenol oxidase (PPO) activity. This was not observed in perennial ryegrass or white clover. Nevertheless, differences in lipolysis in silage between cultivars of red clover were not correlated with PPO activity.     

Fermentation characteristics and aerobic stability of grass silage inoculated with Lactobacillus buchneri, with or without homofermentative lactic acid bacteria

Aerobic spoilage by yeasts and moulds is a major cause of reduced nutritional value of silage and increases the risk of potential pathogenic microorganisms. Recent studies have shown that inoculation with Lactobacillus buchneri inhibits yeast growth and reduces the susceptibility to aerobic spoilage of various ensiled forages. The aim of this study was to determine whether these effects are retained when L. buchneri is added in combination with homofermentative lactic acid bacteria. In three experiments, silages were produced from perennial ryegrass [240–421 g kg⁻¹ dry matter (DM)] inoculated with L. buchneri or L. buchneri plus a mixture of Pediococcus pentosaceus and Lactobacillus plantarum (inoculant PL). Uninoculated silage and silage inoculated with PL alone served as controls. Silages were examined for pH and DM loss in the course of ensilage and chemical and microbiological composition and aerobic stability after 3–4 months. L. buchneri plus PL and PL alone increased the initial rate of pH decline. L. buchneri alone and L. buchneri plus PL enhanced aerobic stability and, in general, reduced yeast and mould counts. In addition, these inoculants increased the final pH and DM loss and the concentrations of acetic acid and 1,2-propanediol (or propionic acid and 1-propanol instead of 1,2-propanediol), and decreased the concentration of lactic acid. The effects of L. buchneri on fermentation products increased with decreasing DM content. In silages of less than 270 g kg⁻¹ DM, L. buchneri increased the ammonia-N concentration. It is suggested that this was associated with the relatively high final pH resulting from the high metabolic activity of L. buchneri in these silages.     

Effect of sowing ratio and stage of maturity at harvest on yield, persistency and chemical composition of fresh and ensiled red clover/lucerne bi-crops

Two experiments investigated (1) the effect of stage of maturity at harvest in the first year on yield and persistency of red clover and lucerne when grown as monocultures and bi‐crops, and (2) the effect of ensiling differing ratios of red clover and lucerne on forage quality and degree of proteolysis. Red clover (cv. Milvus) and lucerne (cv. Vertus) were established in triplicate plots at five sowing ratios:1·00 red clover, 0·75 red clover:0·25 lucerne, 0·50 red clover:0·50 lucerne, 0·25 red clover:0·75 lucerne and 1·00 lucerne. In year 1, plots were harvested in three strips, at different stages of plant maturity, either 11 (early), 13 (mid) or 15 (late) weeks after sowing. In years 2 and 3, the whole plot was harvested at each of four harvests taken during the growing season. The DM yield of lucerne in years 2 and 3 was higher than that of red clover, leading to increased yields from bi‐crops with increasing proportions of lucerne. Strips harvested at the mid‐stage of maturity in the first year on the 0·25 red clover:0·75 lucerne plots produced the highest DM yields overall. Ensiling red clover and lucerne bi‐crops was found to combine the improved wilting properties of lucerne and the reduced proteolysis of ensiled red clover.