Feeding value of pastures for ruminants

Perennial ryegrass is the primary forage component of ruminant diets in New Zealand. It is persistent and palatable, and immature ryegrass has a high nutritive value (NV). However, seedhead development substantially lowers its feeding value (FV) as fibre concentration increases, the rate and extent of digestibility decreases, and voluntary intake declines. Ryegrass pastures are susceptible to accumulation of endophytic and saprophytic fungi in dead material at the base of the sward, especially when mature and laxly grazed. Feeding forage legumes to ruminants grazing grass-dominant pastures will improve animal performance and lessen the reliance on a single species to meet all nutritional requirements. The FV of forage is a function of intake and NV, measured by chemical analyses and animal feeding trials. Performance of individual animals grazing forages is usually limited by energy intake because structural fibre can slow digestion and clearance from the rumen and because of competition between individuals for available feed. The use of metabolisable energy (ME) content of forage to signify FV can give a reasonable indication of animal performance, but it should be used in conjunction with chemical analyses to improve the accuracy of predictions. The relationship between FV, pasture production, animal performance and profitability is complex. The importance of skilled management to maintain pasture quality and optimise animal performance under inconsistent climatic conditions should not be underestimated. Acceptable animal performance with minimal veterinary intervention requires good nutrition, but the genetic potential of livestock in New Zealand cannot be met solely by grazing pasture, especially when a high utilisation of pasture is required to maintain quality and profitability. Producers are responding to industry demands to reduce the seasonality in supply of milk and meat by changing lambing and calving dates, and extending lactation length in dairy cows. Social changes include adoption of once-daily milking in the dairy industry. Some changes have necessitated increased use of supplements and others can be met by feeding forages with a higher FV than ryegrass, all of which require an improved knowledge of feed quality. This information is available through rapid and inexpensive near infrared spectroscopy (NIRS) analysis, enabling animal nutritional needs to be balanced by appropriate nutrient supply. It is essential that producers continue to improve animal welfare, limit excessive use of fertilisers and meet the demands of overseas consumers. Good nutrition, with an increased use of legumes and other forages to complement ryegrass pastures, will enable these objectives to be achieved.     

Feeding value of pastures for horses

The feeding value of fresh pasture grazed in situ is determined by animal performance or productivity and could be relatively easily established for growing and lactating horses. Despite this, there is a lack of published information on the relative feeding value of different pastures and forages grazed by horses in New Zealand and the world. In addition, for adult breeding or non-breeding and young or adult sport or performance horses, the definition of feeding value and its determination remain problematic.

Limited information suggests that the feeding value of perennial ryegrass-based pasture in New Zealand for young growing horses is high, and growth rates for Thoroughbred horses fed solely on pasture in New Zealand are similar to those reported from the Northern Hemisphere where grain-based supplements are fed in addition to pasture or other forages. Attempts to assess the ability of fresh pastures to meet the nutrient requirements of horses are hampered by problems associated with determination of feed intake by grazing horses and lack of knowledge of the digestibility and utilisation of digested nutrients, including the relative bio availability of macro- and micro-minerals in pasture. A further challenge for future research is to determine the effect of herbage allowance and grazing behaviour, including pasture species preferences, on voluntary feed intake by grazing horses.

Grazing pasture has benefits for equine health and well-being including reduced risk of some nutrition-related disorders and reduced prevalence of stereotypic behaviour. Pastured horses have greater freedom for expression of natural behaviours including social interaction and exercise. However, grazing pasture is also associated with animal health problems, particularly parasitism and diseases related to pasture-associated toxins.     

Feeding value of pastures for horses

The feeding value of fresh pasture grazed in situ is determined by animal performance or productivity and could be relatively easily established for growing and lactating horses. Despite this, there is a lack of published information on the relative feeding value of different pastures and forages grazed by horses in New Zealand and the world. In addition, for adult breeding or non-breeding and young or adult sport or performance horses, the definition of feeding value and its determination remain problematic. Limited information suggests that the feeding value of perennial ryegrass-based pasture in New Zealand for young growing horses is high, and growth rates for Thoroughbred horses fed solely on pasture in New Zealand are similar to those reported from the Northern Hemisphere where grain-based supplements are fed in addition to pasture or other forages. Attempts to assess the ability of fresh pastures to meet the nutrient requirements of horses are hampered by problems associated with determination of feed intake by grazing horses and lack of knowledge of the digestibility and utilisation of digested nutrients, including the relative bioavailability of macro- and micro-minerals in pasture. A further challenge for future research is to determine the effect of herbage allowance and grazing behaviour, including pasture species preferences, on voluntary feed intake by grazing horses. Grazing pasture has benefits for equine health and well-being including reduced risk of some nutrition-related disorders and reduced prevalence of stereotypic behaviour. Pastured horses have greater freedom for expression of natural behaviours including social interaction and exercise. However, grazing pasture is also associated with animal health problems, particularly parasitism and diseases related to pasture-associated toxins.     

Steers performance in dwarf elephant grass pastures alone or mixed with Arachis pintoi

The inclusion of legumes in pasture reduces the need for mineral nitrogen applications and the pollution of groundwater; however, the agronomic and animal husbandry advantages with tropical legumes are still little known. The objective of this study was to quantify the effect of the use of forage peanut (Arachis pintoi cv. Amarillo) in dwarf elephant grass pastures (Pennisetum purpureum cv. BRS Kurumi) on forage intake and animal performance. The experimental treatments were dwarf elephant grass fertilized with 200 kg?N/ha, and dwarf elephant grass mixed with forage peanut without mineral fertilizers. The animals used for the experiment were 12 Charolais steers (body weight (BW)?=?288?±?5.2 kg) divided into four lots (two per treatment). Pastures were managed under intermittent stocking with an herbage allowance of 5.4 kg dry matter of green leaves/100 kg BW. Dry matter intake (mean?=?2.44 % BW), the average daily gain (mean?=?0.76 kg), and the stocking rate (mean?=?3.8 AU/ha) were similar between the studied pastures, but decreased drastically in last grazing cycle with the same herbage allowance. The presence of peanut in dwarf elephant grass pastures was enough to sustain the stocking rate, but did not allow increasing forage intake and animal performance.     

Intensifying Beef Production on Utah Private Land: Productivity,Profitability, and Risk

It is hypothesized that Utah beef producers in certain locations could intensify private land use via improved forages and irrigation. Although intensification could increase ranch productivity and help compensate for any future restrictions in public grazing, is the approach profitable and sustainable in a dynamic environment? We investigated the efficacy of intensification using linear programming for three size-classes of model ranches. Model solutions maximize returns net of forage costs; outputs include brood-herd dynamics, optimal forage mixes, and net returns. The model is driven by 11-year risk scenarios combining high or low precipitation with high or low beef prices. We then consider current or no access to public grazing—a policy uncertainty. In general, results support the idea that intensification could be profitable, sustainable, and strategically useful under several sets of conditions. Modeled brood-herds expand and contract in response to precipitation. Optimal forage use is dominated by reliance on treated, improved, and irrigated forages. Critical irrigated forages include alfalfa hay and improved pasture. Profitability generally increases with operation size, but when public grazing is eliminated, herd sizes and profitability drop. Small and medium-sized operations respond to loss of public grazing by using more irrigated pasture and alfalfa hay, while larger operations use a wider variety of irrigated and nonirrigated forages. Sensitivity analysis indicates that optimal forage mixes for all operations remain stable even when input costs for fossil fuels double. Further increases in fuel costs, however, begin to reduce the contributions from irrigated pasture and alfalfa hay. Low precipitation (drought) has very large and negative effects on profitability in general. When drought combines with restricted access to public grazing, profitability of small and medium-sized operations drops further while profitability of large operations increases. Empirical research is needed to test model results and examine what the limiting assumptions reveal about real-world production constraints.     

Energy intake and requirement of dairy cows during the whole year

It is argued that in view of the many new methods in dairy farming an economic model of the dairy farm should be available to improve advisory work. Some quantitative data concerning the dairy cow needed for such a model are given. They deal with a net energy feeding value of grass, hay, silage, artificially dried grass and concentrates estimated with a feed evaluation system based on results obtained with lactating cows. Also data on the requirements for net energy and for long forage dry matter are given, again obtained with such cows. Finally information is given on voluntary intake of forage dry matter at pasture, from fresh grass fed indoors, from various preserved forages including forage pellets, as influenced by milk yield and condition of the cow and by kind of forage and level of concentrates fed. Special attention has been paid to the precision of the information. These data are used to predict both the maximal and minimal amounts of long forage which can be fed in the stall period without loss of production, and the additional quantities of concentrates needed. For the grazing cow the problem of the adjustment of voluntary intake of grass to milk yield and amount of concentrates fed is studied. It is concluded that the information is sufficient to develop an economic model of a dairy farm. For its development grassland research should supply data on pasture yield in terms of digestible organic matter when the forage is fed to sheep at the maintenance level, and the economists should add data on costs of food and labour.     

Advances in pasture management for animal productivity and health

A wide range of management techniques is available to enhance quantity and quality of forage supply to grazing animals throughout the annual production cycle. Within broad limits, dry matter (DM) production is relatively insensitive to management of defoliation frequency, severity and duration. However defoliation management has effects on feed quality which can be enhanced, in particular, by control of pasture growth in the spring through maintenance of relatively low average pasture masses. Treading damage can have significant immediate and ongoing effects on pasture production and farmers can use a range of management techniques to minimise these.

Fertiliser application practices have a potent influence on pasture production and seasonality of that production. Available soil nitrogen is the primary nutrient deficiency limiting production in New Zealand's characteristically grass-dominant pastures. Nitrogen fertiliser usage has increased markedly in recent years, particularly to grow substantially greater amounts of forage during the cool season, and this trend looks set to continue. However, the use of nitrogen fertiliser has important environmental implications.

Pasture renewal and forage crop use has also increased in recent years. Care needs to be taken in conducting cost-benefit analyses, selecting the options that best meet the needs, and in establishment and subsequent management practices. Ryegrass (perennial and hybrids) and white clover remain the primary choice for permanent pasture renewal, the availability of safe endophytes having largely alleviated effects of endophyte toxicosis. Special-purpose mixtures are used, especially in dry environments. Italian ryegrasses, brassicas and chicory are common choices for forage crops. A range of management techniques can be used to alleviate deleterious effects of some forages, including ryegrass endophyte toxicosis, facial eczema, and toxins associated with Fusarium fungi. Generally these techniques are not totally effective. More research is required to increase our understanding of these disorders, and in order to develop more effective and reliable management practices.     

Novel forages for growth and health in farmed deer

AIMS: This paper reviews recent research on the use of new forages in deer farming that may be useful for increasing growth in weaner deer for venison production, increasing the trace element status of deer, and for developing systems less reliant on chemical inputs, notably of anthelmintics used to control internal parasites. GROWTH: Grazing on pure swards of red clover (Trifolium pratense) or chicory (Chicorium intybus) increased weaner growth during autumn by 26-47% and during spring by 10-14%, relative to red deer (Cervus elaphus) grazed on perennial ryegrass (Lolium perenne) /white clover (Trifolium repens) pasture (0.8/0.2). Pre-weaning growth during lactation was increased by approximately 20%. These increases were due to increased rate of degradation of feed particles in the rumen, leading to higher digestibility and higher voluntary feed intakes (VFI). Red clover and chicory produce a greater proportion of their total dry matter (DM) during late summer and autumn than perennial ryegrass/white clover pastures, and are therefore better aligned with the seasonal feed requirements of deer. Grazing on the legume, sulla (Hedysarum coronarium), in autumn and spring increased the growth of weaner deer by 33% and 10%, respectively, relative to pasture-fed animals. PARASITES: Plants containing substantial concentrations of secondary compounds such as condensed tannins (CT) show promise for reducing problems caused by internal parasites. CT present in some legumes and the presence of low concentrations of both CT and sesquiterpene lactones in chicory are reviewed. Feeding sulla containing 35g CT /kg DM reduced abomasal nematode establishment and tended to reduce lungworm (Dictyocaulis eckerti) larval counts in faeces. Relative to weaner deer grazing pasture, weaner deer grazing chicory during autumn required fewer anthelmintic treatments without depressing growth rates. CT extracted from a range of legumes, and CT and sesquiterpene lactones extracted from chicory reduced the in vitro motility of both lungworm and gastrointestinal nematode larvae. The beneficial effects of CT-containing forages on the ability of young deer to manage internal parasite infections could be due to: indirect effects of CT resulting in increased amino-acid absorption, better meeting demands of the immune system; direct inhibitory effects of CT on parasite larvae and; taller plant morphology, reducing the ingestion of infective larvae. The effects of CT depend upon both their structure and CT Condensed tannins DM Dry matter L1 First-stage larvae L3 Infective third-stage larvae LWG Liveweight gain ME Metabolisable energy OM Organic matter OMD Organic matter digestibility VFIVoluntary food intake concentration in the plant, which vary between growing conditions, plant varieties and species. TRACE ELEMENTS: Chicory contained higher concentrations of copper and cobalt than perennial ryegrass/white clover pasture grown on the same farm, and deer grazing chicory had higher liver concentrations of both copper and vitamin B12. These forages may contribute to maintaining adequate trace element status in deer. CONCLUSIONS: Grazing systems that include legumes and herbs such as sulla, red clover and chicory can be used to substantially increase the growth of weaner deer for venison production whilst maintaining deer health and reducing requirements for chemical inputs. For maximum plant persistence and animal responses, these plants should be grown and managed as special-purpose forages and not used in seed mixtures with perennial grasses.     

ASAS Centennial Paper: utilization of pasture and forages by ruminants: a historical perspective

Pastures, forages, and grasslands dominate the landscape across the United States and support a large ruminant population that supplies the nation with value-added animal products. A historical perspective is presented of the innovations as they occurred in the Journal of Animal Science over the past 100 yr in pasture and forage research. Consideration was given to both animal and pasture perspectives. Areas given consideration from the animal perspective were schemes for feedstuff analysis, experimental design and statistics, forage sample preservation, indirect methods of measuring intake and digestion, TDN and energy, nutritive value, harvested forage, and innovations in the grazing environment. Areas given consideration from the forage perspective were a framework for forage-animal interface research, determining pasture yield, choice of stocking method, grazing management, partitioning of forage DM, near-infrared reflectance spectroscopy technology, antiquality constituents, and forage sample preservation. Finally, the importance was discussed of applying research results from the forage-animal interface to general ruminant nutrition research beyond the interface that is focused on altered diets.     

Grazing management as it affects nutrition, animal production and economics of beef production

Until recently, the nutritional fate of the grazing animal has been largely ignored by both animal and range scientists despite the economic dependence of the extensive livestock industry on nutrition from grass. Of the three factors that can be manipulated to improve profit gross margin per animal, is one that is directly affected by nutrition and, hence, grazing management. The relationship between economics and grazing management may be summarized as: Gross margin = f(Animal Performance); Animal Performance = f(nutrition); Nutrition = f(grazing). Economical beef production must consider the needs of the animal and the forage plant at the same time. The health of the sward must be maintained while improving individual animal performance and simultaneously increasing stocking rate. Generally, plants that have been defoliated require a period of recovery before again being grazed. A sward is kept in a vigorous state by preventing repetitive defoliation at the one extreme, and avoiding excessive shading (mature growth) of photosynthetic material at the other. This state is best achieved where livestock grazing is controlled. For any individual paddock, periods of grazing are followed by periods that allow adequate physiologic recovery of the plants. A grazing regimen that keeps the plant in a healthy state is fortuitously also well suited to the nutritional requirements of the animal. Animals on overgrazed pastures are likely to suffer from inadequate feed intake because of deficiencies in feed quantity. Conversely, on over-rested pastures, intake deficiency results from paucity in feed quality. On most unmanaged ranges, overgrazed and over-rested plants are likely to be found side by side. By controlling duration of the rest period as well as duration of the grazing period through pasture subdivision, requirements of both the plant and the animal can be met. With artificially high economic demands placed on animal production, some form of supplementation is required in most modern livestock situations. Whereas energy is frequently the nutrient limiting production it is seldom economically feasible to supplement the grazing animal directly with energy. Protein supplementation to increase forage intake, and thus indirectly energy intake, has become standard practice in many grazing situations. When there is adequate forage with a low crude protein content (less than or equal to 7%), microbially degradable protein is the preferred choice. However, when the animals are in an energy deficient state, either through a shortage of available forage or because their requirements exceed energy intake levels, by-pass protein is required.     

Effects of legume forages on ovine gastrointestinal parasite development, migration and survival

Lambs grazing certain legumes have reduced parasite intensities compared to lambs grazing ryegrass swards. Eighteen replicates of white clover (cv. AberHerald), lucerne (cv. Luzelle), red clover (cv. Merviot) and perennial ryegrass (cv. Abersilo) were sown at equivalent field rates in 25 cm diameter PVC pots and maintained outside for 6 months. On day 0, forage in each pot was cut to 50 mm from soil level and the pots were placed in a glasshouse (at 19-25 degrees C and 70% humidity) in a randomised block design. Ten grams sheep faeces containing 2,133 Haemonchus contortus eggs per gram were placed on the soil in each pot. Six replicates of each forage were destructively sampled on days 14, 21 and 29. Forage samples were cut at 50 mm from the soil surface and at the soil surface to give two samples per pot. The number of nematodes was determined by a modification of the Whitehead tray method. The ratio of free-living to infective-stage larvae was determined from at least 10% of the larvae. The number of H. contortus larvae kgdrymatter(-1) (DM) forage was calculated and the data rank transformed prior to analysis by ANOVA. There were fewer larvae on legumes compared with ryegrass on samples from forage above 50 mm (P<0.001) but there was no forage effect on larvae below this height. The sum of larvae present on all forage per kilogram DM showed fewer larvae on red clover compared with ryegrass on day 21 (P<0.05). There was an effect of day on the total number of larvae on forage (P<0.001) but there were no foragexday interactions. Analysis of the data according to the leaf area above 50 mm from the soil surface confirmed these results, that there were fewer larvae on legume forages than ryegrass above this height (P<0.01). Overall, red clover affected the development of H. contortus and all legumes affected larval migration above 50 mm compared with ryegrass but survival of larvae was similar on all forages. Further work is needed to determine if these effects of legume forages would reduce the number of parasitic larvae ingested by livestock under field conditions.     

Advances in pasture management for animal productivity and health

A wide range of management techniques is available to enhance quantity and quality of forage supply to grazing animals throughout the annual production cycle. Within broad limits, dry matter (DM) production is relatively insensitive to management of defoliation frequency, severity and duration. However defoliation management has effects on feed quality which can be enhanced, in particular, by control of pasture growth in the spring through maintenance of relatively low average pasture masses. Treading damage can have significant immediate and ongoing effects on pasture production and farmers can use a range of management techniques to minimise these. Fertiliser application practices have a potent influence on pasture production and seasonality of that production. Available soil nitrogen is the primary nutrient deficiency limiting production in New Zealand's characteristically grass-dominant pastures. Nitrogen fertiliser usage has increased markedly in recent years, particularly to grow substantially greater amounts of forage during the cool season, and this trend looks set to continue. However, the use of nitrogen fertiliser has important environmental implications. Pasture renewal and forage crop use has also increased in recent years. Care needs to be taken in conducting cost-benefit analyses, selecting the options that best meet the needs, and in establishment and subsequent management practices. Ryegrass (perennial and hybrids) and white clover remain the primary choice for permanent pasture renewal, the availability of safe endophytes having largely alleviated effects of endophyte toxicosis. Special-purpose mixtures are used, especially in dry environments. Italian ryegrasses, brassicas and chicory are common choices for forage crops. A range of management techniques can be used to alleviate deleterious effects of some forages, including ryegrass endophyte toxicosis, facial eczema, and toxins associated with Fusarium fungi. Generally these techniques are not totally effective. More research is required to increase our understanding of these disorders, and in order to develop more effective and reliable management practices.     

草地施肥对牧草和放牧贵州半细毛羊的影响

为评价草地施肥对放牧贵州半细毛羊的影响,在威宁县凉水沟退化人工草地上进行了(NH₄)₂SO₄和NH₄NO₃施肥和放牧试验。结果表明,草地施肥极显著增加牧草氮(N)含量,但各施肥处理之间没有显著差异。(NH₄)₂SO₄施肥极显著增加牧草S、Mn和Zn含量,减少牧草Se含量。试验结束时,施(NH₄)₂SO₄草地半细毛羊血液中Cu、Fe和Se含量极显著低于施NH₄NO₃草地和对照草地,家畜血液Mn、Zn和S含量极显著高于NH₄NO₃施肥牧场和对照牧场。(NH₄)₂SO₄施肥牧场贵州半细毛羊血红蛋白(Hb)和红细胞压积容量(PCV)以及血清Cp含量、血清SOD活力、血清GSH-PX活力和血清CAT活力极显著低于NH₄NO₃施肥牧场和对照牧场,血液其他矿质元素和血液指标及血清生化值在2个施肥处理和对照之间均差异不显著。因此得出结论,威宁县凉水沟天然草地不适合用(NH₄)₂SO₄施肥。     

Performance and dietary preferences of white‐tailed deer grazing chicory,birdsfoot trefoil or alfalfa in north central Alberta

Little information exists on the performance of deer on alternative forage species in northern temperate environments during summer and fall, the period of inherent maximum growth in deer. In performance and choice experiments, we compared live weight gain (g/kg^0.75/day), absolute [kg/ha dry matter (DM)] and relative (% DM) herbage utilization, relative preference index (RPI) as well as plant community visitation of white‐tailed deer grazing alfalfa (Medicago sativa), birdsfoot trefoil (Lotus corniculatus) or chicory (Cichorium intybus) in north central Alberta, Canada. Herbage phytomass and quality was also measured on the grazed pastures. Alfalfa had higher dry matter yields and crude protein concentrations than chicory and trefoil. Chicory had lower neutral detergent fiber concentrations than the other forages. Tannin concentrations were greatest in birds foot trefoil (nearly 55 g/kg DM), well above those in the other forages (<5 g/kg DM). Live weight gain was similar among deer feeding within the paddocks seeded to birds foot trefoil and chicory, and more than two times higher (p < 0.05) than deer feeding in paddocks seeded to alfalfa. Deer spent more grazing time (about 40%) on chicory pastures than on alfalfa and birds foot trefoil pastures. RPI values were greatest for birds foot trefoil at 2.11, intermediate for chicory at 1.40, and lowest for alfalfa at <0.60. Absolute herbage utilization remained similar (p > 0.05) among the three forage species. In contrast, relative herbage utilization was greater from birds foot trefoil (52% DM) than chicory (40% DM) or alfalfa (25% DM). These results suggest that the use of alfalfa with other alternative forages may prove beneficial to deer production, rather than using alfalfa pasture alone.     

Effect of cereal-based concentrates on productivity of Holstein–Friesian cows grazing short-rotation ryegrass (Lolium multiflorum) or kikuyu (Pennesitum clandestinum) pastures

In this study, the effect of increasing the proportion of concentrate in the diet, on efficiency of feed utilisation, was determined when Holstein–Friesian cows grazed short-rotation ryegrass (Lolium multiflorum) or kikuyu (Pennisetum clandestinum) pastures. The concentrates were energy-dense dairy pellets fed twice-a-day at milking and the roughage component was lucerne hay and the pasture.When cows grazed ryegrass, there was no effect on animal performance as the proportion of concentrate in the diet increased from 0.23 to 0.35 (4.75 to 7.50 kg concentrate/cow/day). The substitution rate of concentrates for pasture for the first 1.57 kg concentrate/cow/day fed was 0.58 but rose to 1.18 for the next 1.28 kg concentrate/cow/day.When cows grazed kikuyu, there was also no effect of increasing the proportion of concentrate in the diet on total dry matter intake (DMI) or milk production. However, there was a substantial increase in the in vivo digestibility of whole diet, pasture and acid detergent fibre (ADF) was observed when the proportion of concentrate in the diet increased from 0.08 to 0.25. However, there was a marked decline in pasture digestibility (72% to 64%), and more so in ADF digestibility (61.3% to 48.4%), as the proportion of concentrate in the diet increased further to 0.29 (5.52 kg/cow/day). The intake of kikuyu, when determined by difference between pre- and post-grazing pasture mass, was substantially underestimated compared to the use of the n-alkane technique, and this discrepancy increased as the pasture on offer increased.On both pasture types, the neutral detergent fibre intake, as a % of bodyweight varying from 1.6% to 2.2% for kikuyu and 1.5% to 1.6% for ryegrass was far above the values claimed of 1.2% to restrict intake.The results of this study highlight the limits to the amount of concentrate that can be fed on a typical Australian dairy farm where concentrates can only be fed twice-a-day at milking. The results also provide a more appropriate benchmark for fibre limitation in the ration when cows graze pasture, particularly poorer quality tropical grasses, and this value is well above that found in more intense feeding situations.     

The effect of dietary forage on the development and survival of helminth parasites in ovine faeces

Studies in New Zealand and the UK have shown that lambs grazing birdsfoot trefoil (Lotus corniculatus) or chicory (Cichorium intybus) have reduced parasite intensities compared to lambs grazing ryegrass swards. However, data in the literature on the influence of forages on helminth parasites is equivocal and the underlying mechanisms by which different forage diets may affect these parasites have not been fully determined. The aim of the experiments reported here was to investigate the hypothesis that the consumption of these forages does not affect the hatching and development of helminth eggs in the faeces subsequently produced by the host animal. Lambs grazed monoculture swards of birdsfoot trefoil, chicory, Italian ryegrass (Lolium multiflorum)/red clover (Trifolium pratense) or perennial ryegrass (Lolium perenne)/white clover (Trifolium repens) for 5 weeks and faecal samples collected on days 14, 21, 28 and 35 directly from the rectum of each lamb were used to prepare replicate cultures for each forage type on each occasion. The experiment was repeated over two consecutive years but ryegrass/red clover was not included in Year 2. The dry matter of all faeces was made constant and the faeces were cultured at 27 degrees C for 7 days, before larvae were extracted, counted and identified according to genus or, where possible, species. Overall, the results showed that forage diet had no effect on egg hatchability but significantly affected the development/survival of infective helminth larvae in the faeces of the host animal. Furthermore, feeding birdsfoot trefoil to lambs was found to increase the percentage of helminth parasites that reached the infective stage in the subsequent faeces compared to other forages. Further work is needed to assess whether this would increase the number of larvae on birdsfoot trefoil swards overall under field conditions and to understand the implications of these findings in an applied farming system.     

Enhancing the profitability of pasture-based dairy production in the humid tropics through improved nutrition

Dairy production in the tropics represents a major challenge, especially when reliant on grazed forages, because of the conflicting factors of a high nutritional demand to sustain lactation on the one hand, and the relatively low quality of tropical grasses and a stressful environment, on the other. This paper focuses primarily on those tropical situations where grazed pasture is the cheapest feed resource. Effective management of the pasture as well as the animals that graze it is required in order to maximize economic viability of the farming enterprise. Feed planning helps to ensure that pasture use is maximized, either directly by grazing or, where profitable, indirectly by cutting for conservation. High rates of pasture utilization at each grazing minimize pasture senescence and decay and ensure that pasture remains in a vegetative state of the highest possible nutritional quality. Total annual feed requirements of the grazing herd must therefore be matched as closely as possible to the total annual pasture production on the farm. Stocking rate is critical in this regard, and is the single most important determinant of productivity in pastoral farming. Periods of pasture surplus or deficit will inevitably arise, but can be minimized by matching the monthly feed requirements of the herd as closely as possible to the monthly feed production on the farm. Herd requirements can be influenced, for example, through altering calving patterns and drying off dates. Even with good pasture management practices, it is highly likely that tropical pasture quality will be low for part of the year. Utilization of low-quality forages can be improved through the appropriate use of feed supplements, and the key principles are discussed. Firstly, conditions for optimum fermentative digestion in the rumen must be promoted through adequate provision of fermentable energy and nitrogen as well as essential minerals, such as phosphorus and sulfur. Further supplementation with metabolizable energy or protein, depending on what limits animal production, may be profitable. Various practical supplementation strategies for tropical forages are discussed. Finally, some suggestions for future research and development for enhancing the profitability of pasture-based dairy production in the humid tropics are made.     

Dairy cows fed on tropical legume forages: effects on milk yield,nutrients use efficiency and profitability

Two trials with multiparous dairy cows were conducted. Experiment 1 tested the effects of increasing forage proportion in the diet (500, 600, and 700 g/kg DM) when a mixed sorghum (Sorghum bicolor) and jackbean (Cannavalia ensiformis) silage was used as forage. Experiment 2 studied the substitution of sorghum silage and soybean meal by jackbean silage or fresh cowpea (Vigna unguiculata) forage in the diet. All diets were iso-energetic and iso-proteic. In each experiment, 30 cows were used and separated into three groups. In experiment 1, there were no differences in dry matter intake (DMI), milk yield (MY), or apparent total tract digestibility (aTTd) among the three diets, but milk fat content increased with increasing forage proportion, even though the similar neutral detergent fiber of all diets. Nitrogen use efficiency was highest in the diet containing 600 g forage/kg DM, and some evidence was observed for a better profitability with this forage proportion. In experiment 2, feeding legumes increased DMI despite no effects on aTTd. Milk yield increased in line with DMI, with a larger increase for the fresh cowpea. Nitrogen use efficiency and milk composition were not affected by the diets. The increased MY and lower feed costs increased the economic benefits when feeding legumes, particularly when feeding fresh cowpea. Feeding fresh cowpea or jackbean silage to dairy cows appears to be an alternative to soybean as protein source, ideally at a forage proportions of 600 g/kg DM, without altering milk yield and quality and increasing the farm profitability.     

The effect of birdsfoot trefoil (Lotus corniculatus) and chicory (Cichorium intybus) on parasite intensities and performance of lambs naturally infected with helminth parasites

Conventionally, farmers rely upon the routine use of anthelmintics to control helminth parasites and their use has proved highly cost-effective. However, several factors, including the emergence of helminths resistant to pharmaceutical anthelmintics, are forcing farmers to seek alternative approaches to parasite control. Studies in New Zealand have shown that some alternative forages may reduce parasitic infestation in sheep. In the current study, it was found that under UK environmental conditions lambs with naturally acquired helminth infections grazing chicory (Cichorium intybus) and birdsfoot trefoil (Lotus corniculatus) had fewer helminth parasites than sheep grazing ryegrass/white clover (Lolium perenne/Trifolium repens). Twelve pure-bred Lleyn male lambs grazed replicated 0.5ha plots of birdsfoot trefoil, chicory or ryegrass/white clover for 5 weeks. Liveweight and faecal egg counts (FECs) were determined weekly and eight lambs per forage were slaughtered at the end of the trial to determine total helminth intensities. Lambs grazing birdsfoot trefoil had a lower FEC on day 7 (P<0.05) and fewer total adult helminths than those grazing the other forages on day 35 (P<0.01). Lambs grazing chicory did not have significantly lower FEC than lambs grazing other forages but these lambs were found to have fewer total adult abomasal helminths than lambs grazing ryegrass/white clover (P<0.001). As the performance of grazing lambs is inversely correlated with the intensity of helminth parasites, these alternative forages could be used to improve the liveweight gain of lambs produced in the UK. Overall, the results support the contention that alternative forages could have a positive role in the control of helminth parasites in sheep, subject to successful agronomic development and integration of these forages into whole farm systems.     

The evaluation of endophyte toxin residues in sheep fat

Abstract

AIM: To monitor changes in concentrations of lolitrem B and epoxy-janthitrems in the fat of sheep grazing perennial ryegrass infected with wild-type- and AR37-endophyte, respectively, during the time of year when ryegrass staggers would be expected to be observed.

METHODS: Ten 5-month-old lambs with no previous exposure to endophytes were grazed on either wild-type (containing lolitrem B, n = 5) or AR37 (containing epoxy-janthitrems, n = 5) endophyte-infected perennial ryegrass (Lolium perenne L.) pastures between October 2008 and June 2009. Animals were regularly assessed for ryegrass staggers using the Keogh scale (0 = no signs, 5 = severe tremors). When a score of > 3.5 was observed animals were removed from the treatment pastures for 1 month. Fat biopsy samples were taken from each animal at approximately monthly intervals and analysed for endophyte metabolites using high performance liquid chromatography (HPLC) methods developed during this study. Regular herbage samples were also taken and concentrations of endophyte metabolites measured.

RESULTS: Efficient and reproducible methods to analyse both lolitrem B and epoxy-janthitrems in fat were developed. Concentrations of lolitrem B and epoxy-janthitrems in herbage and in sheep fat increased from late November to peak in mid-February. Ryegrass staggers was observed in both groups of sheep at this time. Following 1 month of grazing non-infected pasture mean concentrations in fat of lolitrem B decreased by 43% from 61.8 to 35.3 ppb, and of epoxy-janthitrems by 38% from 1032.0 to 639.5 ppb. Maximum concentrations in herbage of epoxy-janthitrems (35.7 ppm) were higher than of lolitrem B (3.4 ppm), but signs of staggers were less severe in sheep grazing pasture containing the former compared with the latter (median Keogh scores in late February were 2 and 3, respectively), consistent with epoxy-janthitrems being low potency toxins.

CONCLUSION: This study demonstrated that concentrations of epoxy-janthitrems and lolitrem B in sheep fat increased quickly during the initial phase of the study when concentrations in pasture increased, and decreased when animals were removed from pastures containing these compounds. These data will be used in the risk assessment of the endophyte metabolites.