| Livestock Research for Rural Development 19 (3) 2007 | Guide for preparation of papers | LRRD News | Citation of this paper |
Organic livestock farming system are rising in many countries including developing countries due to increased consumers' demand of organic products and environmental concerns. However, organic farmers face challenges for prevention and control of diseases in farm animals and enhanced production because of banning of use of chemical drugs and feed additives. Nevertheless, nutritional technologies are valuable to combat some of the diseases and disorders and for improved health and welfare of the animals.
Parasitic management program in organic farming could be practiced through improved nutrition, and pasture and grazing management in combination. Supplementation of high amount of dietary protein in the form of undegradable protein, minerals such as zinc, molybdenum, copper and phosphorus, vitamins such as vitamin A, E and B12 have shown fruitful for resistance, resilience and expression of immunity against nematode infections. Pasture and grazing management, fungal feed additives and botanical dewormers might be of particular interest to decrease the prevalence of nematode infections in animals as well as pastures. Many minerals (iron, zinc, manganese, selenium and copper), vitamins (carotenoids, vitamins E and C), probiotics and pre-biotics have been identified as important for normal immune function and disease resistance in farm animals. Saponins, tannins, essential oils and many other plant secondary metabolites appear to be future potential feed additives to improve ruminant production in organic livestock production system.
Nutritional management plays a bigger role to control and prevent many economically important diseases, better health and enhanced performance of animals in sustainable organic animal farming as compared to conventional farming systems.
Keywords: GI nematodes, health, nutrition, organic livestock farming, plant secondary metabolites
In recent years, organic farming is of growing importance over
conventional farming in several countries worldwide (Thamsborg et
al 1999) including developing countries like India possibly due to
increased demand for consumer's organic products. Concerns about
risk of chemical drug residues, transfer of antibiotic resistance
from animal to human through animal derived foods, animal welfare
associated with conventional farming system, environmental effects
and improved food quality in pasture based organic livestock
farming have perhaps led consumers to organic food (Sundrum 2001).
However, the process of conversion from conventional to organic
farming faces several problems mainly due to inadequate technical
knowledge and value-added activities at farm or regional level with
poorly organized marketing (Nardone et al 2004). Breed selection,
sound animal husbandry practices and nutritional management
appropriate to a particular environment are the essential keys to
improve animal welfare and health and therefore successful
livestock organic farming. These necessitate considerable
management skills of the farmers and throw challenges to livestock
advisors, nutritionists including veterinary surgeons and research
scientists. Farming animals under an organic system requires an
even greater standard of management than under conventional
systems. Therefore, a central task for the future is to identify
and to transfer knowledge for good manufacturing organic practices
because many health problems can be resolved with good management
and nutrition (Schumucher 2004). This paper focuses some of the key
issues related to nutrition to improve animal health and production
for sustainable organic livestock farming.
Gastrointestinal parasitic infection is probably one of the most economic and production losses in livestock worldwide (Coop and Holmes 1996; Waller 2006). Nematode infections decrease feed intake, utilization of feed, body weight gain, milk production and reproductive performance. It is also important in respect of development of resistant strain of gastrointestinal parasites to broad spectrum anthelmintics. It is perhaps more challenges for livestock organic farming because of the more reliant on the pastures and banning the use of any chemical drugs. Grazing management combined with nutritional supplementation with concentrates and/or forage was the most frequently reported anti-parasite strategy in organic livestock farming (Svensson et al 2000). The sustainable nematode control strategies should entail a greater variety of control measures in combination (Waller 2006).
Many research studies have reported that protein supplementation either in the form of by-pass protein or higher dietary protein improves resilience and expression of immunity to gastrointestinal parasites (Coop and Holmes 1996; Coop and Kyriazakis 2001). Protein supplementation in the form of rumen undegradable protein has been shown to increase the resistance of sheep to Haemonchus contortus (Wallace et al 1996). When animals, which were infected with gastrointestinal nematodes such as Trichostrongylus colubriformis, were fed with increased amount of rumen undegradable protein in the form of fish meal, animals decreased less body weight than those animals that were not fed the increased level of rumen undegradable protein (van Houtert et al 1995). Buttler et al (1999) also reported that animals parasitized with Trichostrongylus colubriformis and fed with 22% protein diet achieved growth rates similar to those uninfected low protein diets as evidenced by reduced fecal egg counts. Improved host nutrition primarily by-pass protein increases the rate of rejection of adult parasites without affecting the rate of establishment of infective larvae (van Houtert and Sykes 1996). However, the potential of metabolisable protein to enhance resistance to nematode infection is dependent on the requirement relative to its supply in the diet and demand for other competing physiological functions (Kahn et al 2000). Genetic resistance to nematodes to animals is only expressed in the presence of improved metabolizable protein supply.
In a field survey in Sweden, Svensson et al (2000) noted that in the autumn 60% and 52% and in the spring 48% and 29% of the organic and conventional farmers, respectively used nutritional supplementation in the spring, as methods to restrict parasite problems in their calves.
Because of the dependence of home grown feeds and forages in principles of organic livestock farming and minerals deficiency in pastures characteristics of area specific, minerals deficiency in animals could be more prevalent in organic animal farming. Zinc plays an important role to build up a successful immune response against gastrointestinal nematodes. Iron had presumably no direct effect on parasitic control; however, iron supplementation improves host performance because it restores iron status in the body which is lost through blood during gastrointestinal parasitic infections (Koshi and Scott 2003). In certain areas deficient in Mo in soil and pasture, supplementation of Mo equivalent to feeding a diet containing 4-8 mg/kg DM in sheep reduces worm burden (McClure et al 1999). Suttle et al (1992a,b) noted 78% and 23% reduction of Haemonchus contortus and Trichostrongylus vitrinus population in sheep with the supplementation of 0.05 mmol Mo/kg DM of feed. However, extreme of these both limits can increase the infection. Cu acts as both anti-parasitic and host immunity boosting to some nematodes in goat, sheep and chicken. Bang et al (1990) reported that Cu oxides particle (5 g) decreased the establishment rate of T. circumcina and Haemonchus contortus by 56 and 96%, respectively; but not of Trichostrongylus colubriformis in lamb. Excess Mn may increase more infection as parasites need it and perhaps toxic to immunity response (Koski and Scott 2003). Coop and Field (1983) reported that the phosphorus level of the diet at a level of 0.28% DM increased weight gain of lambs and decreased worm burden and fecal eggs counts infected with Trichostrongylus vitrinus over those lambs fed a low (0.19%) phosphorus level diet.
Deficiency of vitamin A, B12 (or cobalt), E (or selenium) have shown to delay the adult worm expulsion, more parasitic eggs in feces and increased fecundity due to changes in host intestinal physiology that promote host protection. Vellema et al (1996) noted that vitamin B12 deficient lambs had higher faecal egg counts than vitamin B12 supplemented one after natural infection with gastrointestinal nematodes.
Feeding of fungi such as Duddingtonia flagrans, Harposporrium anguillulae and Arthrobotrys spp. as a feed additive during the time when the parasite infestation is expected to high have the potential to control gastrointestinal parasite in the pasture (Waller and Larsen 1993; Thamsborg et al 1999). Feeding of these nematode-destroying fungi which survived in the gastro-intestinal tract have reported to reduce the infectivity of herbage and also reduced worm burdens in grazing animals (Larsen et al 1997). Terril et al (2004) noted that feeding of different doses of Duddingtonia flagrans spores mixed with complete diet to the does reduced the infective larvae with the increased doses of spores, and feeding daily was more effective than intermittent feeding. It can not control the parasites when these are in vegetation from feces. However, a number of key issues such as appropriate delivery system, long term efficacy and potential long term environmental effects need to be resolved (Thamsborg et al 1999; Scossa et al 2004).
Many studies have shown that use of tree leaves as ingredient of concentrate mixtures in the diets of ruminant could be particularly important in small ruminants for improved utilization of cereal straws (Patra et al 2003). This is also beneficial for control of internal parasites as tree leaves contain many polyphenolic compounds which are inhibitory to gastrointestinal nematodes (Lorimer et al 1996). In a study by Kahiya et al (2003), inclusion of dried leaves of Acacia karoo in their basal diet at a rate of 40% dry matter and infected with Haemonchus contortus significantly decreased in the faecal egg counts, and worm burdens were reduced by 34%, which is attributed the presence of tannins in tree leaves.
Bioactive forages have shown to reduce the parasite infestation and improve the performance of the animals grazing these forages. Some legume forages such as sulla (Hedysarium coronarium), sainfoin (Onobrychis viciifolia), birdsfoot trefoil (Lotus corniculatus), maku (Lotus pedunculatus) and Serecea lespedeza reduce parasitic infections as measured by reduced parasitic egg excretion, egg hatching, total worm burden and rate of larval development of parasites specific to different parts of gastrointestinal tract (Min and Hart 2003; Ramirez-Restrepo et al 2005a). Niezen et al (1995) reported that lambs grazed on Hedysariumcoronarium, which contains condensed tannins, had lower faecal egg counts and lower Trichostrongylus spp. burdens than those grazed on Medicago sativa, which does not contain condensed tannins. Min et al (2003) noted that Angora goats grazing on Lespedeza cuneata (5.2% condensed tannins/kg DM) had a reduction of 76% in total worm burdens, 94% Haemonchus, 100% Teladorsagia spp and Trichostrongylus compared to goats on crabgrass/tall fescue (0.2% condensed tannins/kg DM). However, Pomroy and Adlington (2006) observed that short period of feeding of sulla did not affect the mature and immature worm burden of mixed nematode infection. Tzamaloukas et al (2005) noted that lambs grazing chicory (Cichoriumintybus) had the lowest adult worm burdens compared to those grazing on grass/clover, Hedysarium coronarium and Lotus pedunculatus for a short term period. Similarly, in vitro experiment with condensed tannins extracted from range of forages showed that antiparasitic effect of condensed tannins was dependent on developmental stages of parasites and types of condensed tannins with sulla tannins having least effect (Molan et al 2000). Niezen et al (2002) noted that feeding sulla to young lamb resulted in lower Trychostrongylus circumcinacta burden but not in Trychostrongylus colubriformis. One common characteristic of these legume forages is the presence of medium to high content of condensed tannins. Effects of tannins on worm biology such as direct anthelmintic properties as indicated by larval development in the absence of host immunity and/or indirectly on improved protein nutrition and thereby host immunity against parasite are explained for the mechanism of action of these plants. However, the effect of condensed tannins containing forages on gastrointestinal parasitic infection is dependent upon the period of feeding, types of parasitic infections and levels and types of condensed tannins present in forages. These "anthelmintic pastures", therefore, represent most promising solution to control of nematode infections and their use is compatible to principles of organic farming.
Plaughing a pasture to break up the dung can spread the parasitic eggs and larvae which makes difficult for the animals to selectively graze away from infected area. Harrowing a pasture before dry period may be valuable when pasture gets rest for long time. This prevents the animals from grazing in the same field or paddock. Because freezing temperatures or droughts eliminate some infectious larvae, cold or dry periods can be relied upon to reduce or extend rest periods. A three-year rest period (short rotation) is required for a complete cleaning.
Mixed grazing of a pasture by different species such as cattle and sheep (but not sheep and goat) together may reduce the infection as a very little cross infection of parasites occurs between animal species. There are even certain species of worms that affect only a particular ruminant species.
Controlled grazing methods permit pastures to rest and soil life to function well, and contamination can be reduced. If pastures remain ungrazed for more than one year, it could be a clean pasture in which there will have been no contamination of worm larvae. However, a three-year rest period is required for complete cleaning from the parasite contamination in the pastures. This decrease occurs because soil organisms, including earthworms, dung beetles, and nematophagous fungi destroy parasite eggs and larvae.
The height of the pasture sward can affect parasites. The majority of worm larvae live in the first one to two inch from the ground onto vegetations, so not allowing animals to graze below that point can reduce a lot of infestation.
Alternate grazing of two or more ruminant species has been shown to be of value in controlling some species of parasites (Thamsborg et al 1999). For example, cattle, sheep and goats seldom compete for the same type of grazing because the species prefer different types of length of forages. Running cattle in pastures that have had sheep grazing on them helps break up the life cycle of sheep parasites, since sheep and cattle do not have the same species of worms infesting them. This affects parasites loads of each grazing species as transmission is dependent on ingesting the parasite larvae on certain parts of the forage. If the cattle are allowed to graze the grass down to 3 to 5 cm from the ground, many parasites will be killed off from exposure to the sun.
This has also been found to be effective for reducing the burden of parasites in ruminants (Thamsborg et al 1999). A successful approach could be adopted in which pastures are subdivided and the animals are intensively grazed for short period at higher stocking density when the forage is at the young, active growing stage. If this type of rotation is carefully planned, the animals can be returned to the original pasture which could be nutritious. Svensson et al (2000) reported that 27% of organic farmers follow rotational grazing as compared to 3% in conventional farming as a control measures for nematode infections. The producers gained from improved nutrition through decreased parasites loads and reduce drug cost.
Stocking rate management is practiced by many organic farmers to control parasite infection (Thamsborg et al 1999). Thamsborg et al (1996; 1998) noted positive relationship between stocking rate of lambs and pasture infectivity. Similarly, Kristensen et al (2006) low stocking as compared to high stocking rate reduced nematode infection in heifer and steers grazing in wet marginal grasslands. Low stocking rate reduces parasite infestations as pastures get less contaminated and sward height remains high to be eaten lower part of the sward which is mostly contaminated by parasite larvae.
Parasitic infestation becomes more prevalent in some seasons of the year depending upon the climatic condition, nematode species infection and length of the grazing season. Therefore, the animals should ideally be put in a new pasture when infection is expected to high. It is preferable to restrict grazing in highly contaminated fields during infection season. And also, risk of infection is lowered by allowing the grazing after the dew has dried or pasture has dried out after rain. This forces the larvae to stay at ground level and they are less likely consumed by animals. Githigia et al (2001) reported that weaning the lambs at the beginning of July and moving them before the expected mid-summer rise in herbage infection to a clean pasture may prevent parasitic gastroenteritis and achieve good production in Denmark.
Young animals are most susceptible to parasitic infestation than mature animals due to less immunity to parasites at that time. Therefore, the access of clean ungrazed pasture first to young animals such as lamb, calf or kid may reduce the risk of parasite infection (Thamsborg et al 1999). In a survey of Hertzberg et al (2004), it has been shown that adoption of grazing management strategies reduced parasitic infections considerably. Svensson et al (2000) noted that the most common procedure practiced by organic farmers (40% vs. 3%) was to rotate calves on pastures not grazed by any cattle in the current or previous grazing seasons.
Current standard of organic farming recommend use of
phytotherapeutic and homeopathic treatment in some countries;
however, efficacy and experts in this field are limited. There are
several plants, not common feeds that have been used sporadically
for controlling internal parasites in ruminants but there is no
much data available on the efficacy and optimum dose for their
uses. Most of this information is anecdotal and needs further
verification if these plants/herbs are to be used effectively. Many
botanical dewormers that could be added in animal feed includes
garlic, pumpkin seed, worm wood (Artemisia spp.), neem seed,
tansy (Tanacetum vulgare), wild gingers
(Asarum canadense), mustard, common juniper
(Juniperus communis), male fern radishes, raw grated
turnips or horseradish, pyrethrum (Chrysanthemum
cinerariifolium) and could be effective against
gastrointestinal, lung and liver parasites. Common juniper has
deworming properties, notably against liver fluke. Blackberries,
raspberries and young ash and elder shoots are other plant species
with deworming properties that could be available in pastures. Some
plants such as fennel (Ferula spp.), carrots and wild
parsnips that found abundantly alongside fields and roads could
probably be used to graze to control some parasites. In a study,
Bennet-Jenkins and Bryant (1996) reported 91% reduction of
Haemonchus contortus infection in goats fed
Eucalyptus grandis as sole feed for 7 days. However, overall
scientific evidences of use of these anthelmintic plants are
limited which needs more research before they could be used in
organic farming.
Organic livestock production standards considerably restrict on the use of many animal health inputs that are routinely used in conventional production systems Hence, there is much more growing significance to boost immunity to animals in different micro-organisms in organic farming as compared to conventional livestock farming. The immune system is designed to resist the infectious bacteria, virus, fungi, and protozoa. This utilizes a diverse cell populations and acts through highly developed mechanism to ward off infectious diseases. The significance of nutritional status and the ability of the animals to defend against infectious organisms are well established. However, recently several trace minerals, vitamins and other nutrients have been recognized as essential factors for proper functioning of immune system.
Minerals deficiencies may be more prone in organic farming as farmer's are to fed mostly home grown pasture and feeds where soil may be deficient in minerals. There is need to ensure that organically produced feeds are sufficient in any nutrients to keep the animals in full health and vigor at all stages of their productive life. Sub-clinical or marginal trace mineral deficiencies occur more frequently and major problem than acute mineral deficiencies, because characteristics symptoms are not evident to allow the producer to recognize the deficiency. Instead, the animals grow or reproduce at a reduced rate, use feed less efficiently and operate with a depressed immune system. Identifying the mineral deficient pasture and feed and correction of it is important to boost the immunity of animals associated with the minerals.
Trace minerals that have been identified as important for normal immune function and disease resistance are zinc, manganese, selenium and copper in many field conditions (Galyean et al 1999). Zn and Mn are essential for the integrity of the epithelial tissue such as gastrointestinal, urinary, reproductory and respiratory tract thereby reduce infiltration of pathogen through these epithelial lining and protect. Copper and zinc are important for both cell and humoral mediated immunity through many molecular functions such as production of antibodies, neutrophils and lymphocytes replication, and antioxidant enzyme production. They have shown to enhance recovery rate in bacterial and viral diseases including mammary gland infection during lactation. Chirase et al (1991) noted that Zn supplementation in the form of zinc-methionine (89 ppm) or zinc oxide (90 ppm) enhanced the recovery rate from challenged infection of bovine rhinotracaeitis virus as compared to control (31-35 ppm) in cattle. Organic Zn supplementation (Zn-proteinate) also decreased infections of the mammary gland during lactation in dairy cows (Spain 1993). Cu supplementation (20 ppm) has shown to reduce severity of udder infection challenged with Escherechia coli than control (6.5 ppm) in dairy heifer (Scaletti et al 2003). There is positive relationship between selenium status in conjunction with vitamin E and resistance against infections. Smith et al (1985) noted that supplementation of selenium in first lactation dairy cattle reduced the incidence and severity of clinical symptoms of mastitis. Selenium alone reduced the duration of clinical symptoms of mastitis by 46%, vitamin E alone by 44% and in combination of Se and vitamin E by 62%. Chromium supplementation may effectively defend against infectious diseases in face of infectious microbial challenges and reduce morbidity rate in stressed cows probably by reducing the cortisol level in plasma and thereby increasing immunoglobulin level. Burton et al (1993) noted greater humoral and cell mediated immunity in cattle supplemented with 0.5 ppm chelated Cr than in unsupplemented cattle during peripaturient and early lactation when animals appear to be in stress. He suggested that Cr supplementation could be beneficial to resist important production diseases such as mastitis in dairy cows and bovine respiratory disease complex in feeder cattle. However, the results of Cr supplementation on immune response are not always consistent.
Many researchers currently assume that many trace minerals are required at higher levels for normal functioning of immune system to resist infections than that required for normal growth, feed efficiency, gestation and lactation. It indicates that higher nutrient levels than those recommended by different agencies may be needed for maximum productivity and health of the animals.
Carotenoids (beta-carotene and lycopene), vitamin A, E and C are naturally-occurring antioxidant nutrients that scavenge detrimental free radicals produced through normal cellular activity and from various stressors (Bendich 1993) and appear to be important for animal health. The antioxidant function of these micronutrients could enhance immunity by maintaining the functional and structural integrity of important immune cells. Both in vitro and in vivo studies showed that these antioxidant vitamins generally enhance different aspects of cell mediated and humoral immunity. A compromised immune system will result in increased susceptibility to diseases, thereby leading to increased animal morbidity and mortality, and reduced animal production efficiency. Galyean et al (1999) in a review suggested that vitamin E supplementation greater than 400 IU could be beneficial to decrease morbidity to infectious diseases such as bovine rhinotraceitis and weight gain. These vitamins like trace minerals may be required greater amount for normal immunity than recommended by different agencies for normal growth and milk production.
A number of studies support the use of probiotics (lactic acid bacteria, such as lactobacilli and bifidobacteria, and yeast culture such as saccharomyces spp, and other beneficial bacteria) to prevent and treat many infectious diseases, particularly of the intestine such as diarrhoea in young animals besides many other health benefits and animal performance. Probiotic supplementation of the intestinal microflora enhances defense, primarily by preventing colonization by pathogens and offering a greater stability of the intestinal ecosystem, and by an indirect, adjuvant-like stimulation of innate and acquired immune functions of intestine (Fuller 1989). The responses are usually expected when animals are under stress and unwanted microbial populations in the intestine are high (Fuller 1989). Besides the health benefits of probiotics, it improves growth rate and feed conversion efficiency in calves (Ramaswami et al 2005), microbial protein flow (El Hassan et al 1996) and DM intake (Putnam et al 1997) particularly in poor managemental conditions.
A range of non-digestible dietary supplements (lactulose,
lactilol, a variety of oligosaccharides and inulin) have now been
identified that modify the balance of the intestinal microflora,
stimulating the growth and/or activity of beneficial organisms such
as bifidobacteria and lactobacilii and suppressing potentially
deleterious bacteria (Gibson 1998). Prebiotics have shown promise
in the prevention and control of exogenous and endogenous
intestinal infections and good health of the animals (Grizard and
Barthomeuf 1999).
Many disorders and diseases in farm animals are related to nutritional imbalances of minerals, vitamins, protein and energy. However, some nutritional disorders are sometimes encountered in the organic livestock farming system.
Although organic livestock farming are based on grazing and feeding of high amount of roughages, sometimes fattening of animals are practiced which may result in metabolic disorders due to sudden changes in the feed ration when changing from high roughage to high cereal content (Nielsen and Thamsborg 2005). Subacute ruminal acidosis is a common and economically important metabolic disorder. A common factor associated with rumen acidosis is large amounts of starch or other highly fermentable carbohydrates sources such as barley and wheat in the ration. Acidosis frequently occurs after a sudden diet change, especially a switch from a forage based diet to a concentrate based diet or following a feed deprivation when animals consume excessive amount of concentrate. Processing of grains increases starch availability and promotes in acidosis (Owens et al 1998). Sometimes, rumen acidosis is associated with alfalfa hay that is too low in ADF and NDF. Forage fiber is essential to maintain good rumen health and to maximize rumen microbial efficiency. NRC (1989) recommends that the dry matter of dairy cow diets should contain at least 25% neutral detergent fiber (NDF) and that three quarters of the NDF should come from forages. Occasionally, over processing of the total mixed ration even further reduces the effectiveness of the fiber. There is decrease of rumen pH because of increased production of VFA and lactic acid and less buffering activity in the rumen fluid (Owens et al 1998). Fortunately, this is perhaps less common in organic farming due to more dependence on pastures. Fiber digestion, milk fat, milk production and feed intake are reduced when rumen pH drops below 6.0. Lower rumen pH (< 5.5) for extended periods of time predisposes to damage of rumen wall, diarrhoea, laminitis ruminal stasis and bacterial liver abscesses. Acute and clinical signs of acidosis will occur if rumen pH drops below 5.0.
Milk fever or hypocalcaemia is sometime more in organic farming than conventional farming, although milk production is less in organic farming and no inorganic fertilizer supplementation in the pasture such as K is used. It is perhaps due to higher age animals which are more likely prone to milk fever. Although high milk yielding animals fed a diet low in calcium (Ca) are more at risk from hypocalcaemia, the most important predisposing factors are physical or nutritional stresses to which the animals cannot respond quickly enough to replenish from body reserve. Where Ca levels provided in the diet are sufficient, hypocalcaemia may even occur because of a sudden demand for calcium through physical exertion such as high Ca secretion through colostrums and milk immediately after calving. This is because the mobilization of Ca from body reserves such as bone or absorption of Ca does not respond physiologically promptly to meet with requirements depending upon the previous Ca status during dry period. Recent theories suggest that acid-base status of animals determines predispose to hypocalcaemia. The feeding of a diet high in cations especially in K and Na in dry period tends to increase incidence of milk fever (Goff et al 2004). Whereas, feeding cows with diet relatively high in anion, primarily Cl and SO4 may help to prevent milk fever. The model of Charbonneau et al (2006) from 22 published studies predicted that lowering dietary cation-anion balance [(Na + K) - (Cl + 0.6 S)] from 300 to 0 mEq/kg reduced risk for clinical milk fever from 16.4 to 3.2%. Vitamin D, Ca: P ratio and protein content in the diets may affect the absorption and its subsequent deposition in the bone even though Ca content in the diet is adequate. A ratio between 1: 1 and 2: 1 of Ca to P would appear to be most satisfactory, providing the overall levels of each element are within the normally accepted range. Hypocalcaemia often occurs following sudden change in feed which results in the animals going off their feed for a few days. Therefore, vigilant nutritional management of animals is important to prevent milk fever.
Bloat is often brought on by a rapid intake of immature, highly nutritious green legumes (alfalfa or clovers). These plants contain high levels of rapidly ruminally degradable protein and carbohydrates in their vegetative state, and contribute to the production of froth, and subsequently, bloat.
Bloat seems to become a less of a challenge for organic farmers than their conventional counterparts. Successful organic farmers suggest that as the soil health improves bloat becomes less of a challenge. Animals should not be held off pasture for too long time. This will prevent gorging when they start grazing, and will also benefit digestion. Drenching animals with sunflower, canola or paraffin oil and/or spraying the pasture with seaweed can be used as prevention under an organic system. There are some legumes that are considered to be less of a bloat problem than others. Lotus corniculatus (Birdsfoot trefoil) is less likely to cause bloat than alfalfa and many types of clovers, because it reduces the rate of digestion considerably in the rumen. Also, grasses do not usually cause bloat, because the protein content is lower than legumes. Another option would be to incorporate a legume known to be a non-bloating species. Condensed tannins have the possible to decrease bloat by altering ruminal gas production and soluble protein digestibility from wheat forage (Min et al 2005).
Antibiotics and growth promoting hormones and other chemical rumen manipulators are restricted in organic farming. Therefore, recently alternative nutritional technologies emerge out to cope up with the situation. Naturally occurring many plant secondary metabolites have shown potential to improve rumen fermentation favorably and to increase feed efficiency, live weight gain. These can be used in environmentally friendly animal production. Unlike chemical feed additives, these plant feed additives could pass easily many of the regulatory hurdles for use in organic farming. Therefore, for the future, feeding with high bioactive forage content could be one way of improving livestock production and the product quality of organic farming (Nielsen and Thamsborg 2005).
Saponins are the naturally occurring secondary compounds present in many plants and of high molecular weight glycosides in which sugars are linked to a triterpene or steroidal aglycone moiety. Saponins (Yucca schidigera and Quillaja saponaria) or saponin containing forage (Enterolobium cyclocarpum, Sesbania sesban) and fruits (Sapindus saponaria, Sapindus rarak) are toxic to rumen protozoa which could be beneficial for improved ruminant productivity depending on the diets and the saponins involved. Similarly methanol extract of pods of Acacia concinna and ethanol extract of Sapindus mukorossi tropical plants, have been shown to inhibit rumen protozoa in vitro (Patra et al 2006a; Agarwal et al 2006) which is attributed to the presence of saponins. Supplementation of pericarp of the fruit of Sapindus saponaria in sheep inhibited rumen protozoa and stimulated bacterial and fungal counts, and dry matter degradation (Diaz et al 1994). Ciliate protozoa are primarily responsible for the substantial turnover of bacterial protein. As a consequence nitrogen retention is improved by defaunation. It is generally agreed that removing or suppressing protozoa would result in increased ruminant performance, particularly on low-protein diet. Similarly, use of essential oil as feed additive in the diet of ruminants could be beneficial by modifying the protein digestion in the rumen.
In some animal feeding trials, the efficiency of microbial protein synthesis receiving alfalfa saponins in sheep and Yucca schidigera in cattle was decreased, because the growth of bacteria and protozoa was depressed (Lu and Jorgensen 1987; Goetsch and Owen 1985). It seems that effect of saponins is diet dependant. Gas and total VFA production from barley grain were increased by Yucca schidigera; whereas, those were reduced from alfalfa hay (Wang et al 2000a, b). In this experiment, yucca extract reduced acetate to propionate ratio and ammonia concentrations irrespective of the substrate. Inclusion of Enterolobium cyclocarpum increased the rate of body weight gain in sheep by 24% (Leng et al 1992) and 44% (Navas-Camacho et al 1993) and wool growth by 27% (Leng et al 1992) which was attributed due to a decrease in protozoal numbers. However, water washings of mahua (Bassia latifolium), which almost completely removed saponins, in the diet of crossbred calves did not affect the growth and nutrient utilization (Joshi et al 1989). It appears that various saponins have different responses. Therefore, there is need to identify the saponins that would be beneficial for ruminal manipulation and hence ruminant production.
Tannins are the polyphenolic polymers distributed widely in many plants. A number of forages such as sainfoin (Onobrychis viciifolia), Lotus pedunculatus (lotus) and Lotus corniculatus (Birdsfoot trefoil) contain condensed tannins which are beneficial for the rumen fermentation when they are present in moderate quantity (4 to 6% of the total) in the diets. However, high dietary concentrations (6-12% DM) may depress voluntary feed intake, digestive efficiency and animal productivity. Animals grazed in these pasture gives better overall performances such as higher growth, improved reproductive performance wool production and higher milk yield with increased milk protein in addition to reduced gastrointestinal parasites burden. Min et al (2003) reported in their review that dietary concentration of condensed tannins, ranging from 2 to 4.5% of total dry matter, improved efficiency of N use and increased daily weight gain in lambs on temperate fresh forages like Lotus corniculatus. However, a decrease of dry matter intake, diet digestibility and growth rate was obtained in sheep fed forages containing greater than 5.5% of DM of condensed tannins. Wang et al (1996a) reported that lambs grazing Lolium corniculatus had better wool growth and carcass gain than grazing lucerne which was attributed to the presence of condensed tannins (3.4%) in the diets. Similarly, Lolium corniculatus fed to lactating ewes increased the secretion rates of whole milk, lactose and protein by 21, 12 and 14%, respectively, during mid and late lactation (Wang et al 1996b). Similar experiment with dairy cows were conducted by Woodward et al (1999) and they reported that cows fed on Lolium corniculaus had 42% higher milk yields than those fed on Lolium corniculatus + PEG, ryegrass, ryegrass + PEG, indicating that condensed tannins in Lolium corniculatus caused an increase in milk yield. It also responsible for 57% increase in the milk protein of cows fed on Lolium corniculatus. Feeding of 7.5% tamarind seed husk, a tannin rich by-product to cross-bred dairy cows also resulted in increased body weight gain and milk protein content in mid lactation (Bhatta et al 2000). Ramirez-Restrepo et al (2005a,b) reported higher growth, reduced parasites burden, improved reproductive performance and wool production in lambs grazing Lolium corniculatus than perennial ryegrass (Lolium perenne)/white clover (Trifoliumrepens) pasture. One of the reasons for these effects could be possibly due to increased metabolizable protein supply, from the protein binding action of condensed tannins in the rumen when animals are fed a diet with highly degradable protein.
Besides, tannins have found to decrease methane inhibition which is beneficial for sparing of energy loss as methane. Many types of forage known to contain condensed tannins have been shown to decrease methane production both in vivo and vitro. Tannins present in Callindra calothyrus reduced nutrient degradation and methane release per gram of organic matter degraded in in vitro experiments with rumen simulation technique (RUSITEC) apparatus (Hess et al 2003). Reduced methane production was also observed in RUSITEC as the proportion of Onobrychis viciifolia) incubated were increased (McMahon et al 1999). Woodward et al (2002) investigated the feeding of sulla (Hedysarium coronarium) on methane emission and milk yield in Friesian and Jersey dairy cows. Cows grazing on sulla had higher daily dry matter intake (13.1 vs. 10.7 kg DM) and daily milk solid production (1.07 vs. 0.81 kg) than grazing perennial ryegrass pasture. Total daily methane emission was similar (253.9 vs. 260 g). However, cows fed sulla produced less methane per kg DM intake (19.5 vs. 24.6 g) and per kg milk solid yield (243.3 vs. 327.8 g). Similar trends in methane emission and milk production have been observed in sheep fed lotus silage (Woodward et al 2001). There was also a 16% reduction in methane production in lambs fed on Lolium pedunculatus, which is due to condensed tannins present in it (Waghorn et al 2002). Another condensed tannins containing forage peSericea lesdeza (17.7% CT) decreased methane emission (7.4 vs. 10.6 g/d and 6.9 vs. 16.2 g/kg DMI for Sericea lespedeza and crabgrass/tall fescue, respectively) in Angora goats (Puchala et al 2005). Dry matter intake (1.11 vs. 0.67 kg/d) and digestible DMI (0.71 vs. 0.51 kg/d) were greater for Sericea lespedeza than for crabgrass/tall fescue in this study. Methanol extract of seed pulp of Terminalia chebula which contains a substantial amount of phenolic compounds reduced methane production and inhibit rumen protozoa (Patra et al 2006a). Similarly, methanol extract of Populus deltoids leaves decreased methane production in vitro (Patra et al 2006c). Tavendale et al (2005) studied the mechanism of inhibitory effects of extractable condensed tannin fractions from Lotus pedunculatus on the common rumen methanogens Methanobrevibacter ruminantium, strains YLM-1 and DSM1093. Oligomeric CT fractions were inactive against both strains, as determined by methane production measurements. The polymeric fraction completely inhibited methane production. Inhibitory effects in broth culture for strain YLM-1 were bacteriostatic, while strain DSM1093 did not recover growth, as indicated by methane production, even upon prolonged incubation. Results indicate that CT action on methanogenesis can be attributed to indirect effects via reduced hydrogen production (and presumably reduced forage digestibility) and via direct inhibitory effects on methanogens.
There are many plant secondary metabolites such as that present
in garlic (Patra et al 2006b), flavonoids (Broudiscou et al 2000)
and essential oils (Wallace et al 2002) which could have also
potential to improve ruminant fermentations such decreased methane
production and hence improve energy utilization and protein
economy.
· A good accomplishment in organic livestock farming system stands upon the nutritional management of the animals for better performance and animal health. Nutrition plays a key role to prevent nematode infections, to provide wellbeing to the animals through better immunity and to improve animal production.
· Bioactive plant secondary metabolites in forages and as feed supplements could have the potential to improve future organic livestock farming.
· A comprehensive understanding of the peculiarities of different production system is a prerequisite for integrating the knowledge and skill required to provide high quality health management and production under sustainable organic system.
· Roles of nutritionists and veterinarians are more important in organic system than conventional system which needs improved nutritional management and efficient surveillances of diseases and organisms that are economically important.
·Many nutritional technologies emerged out in the area of
prevention and treatment of gastrointestinal parasite infections,
boosting immunity and enhancing production to solve the situations
faced in organic livestock production entail more systematic
research.
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Received 31 December 2006; Accepted 7 February 2007; Published 1 March 2007