Dynamic role of single-celled fungi in ruminal microbial ecology and activities

In ruminants, high fermentation capacity is necessary to develop more efficient ruminant production systems. Greater level of production depends on the ability of the microbial ecosystem to convert organic matter into precursors of milk and meat. This has led to increased interest by animal nutritionists, biochemists and microbiologists in evaluating different strategies to manipulate the rumen biota to improve animal performance, production efficiency and animal health. One of such strategies is the use of natural feed additives such as single-celled fungi yeast. The main objectives of using yeasts as natural additives in ruminant diets include; (i) to prevent rumen microflora disorders, (ii) to improve and sustain higher production of milk and meat, (iii) to reduce rumen acidosis and bloat which adversely affect animal health and performance, (iv) to decrease the risk of ruminant-associated human pathogens and (v) to reduce the excretion of nitrogenous-based compounds, carbon dioxide and methane. Yeast, a natural feed additive, has the potential to enhance feed degradation by increasing the concentration of volatile fatty acids during fermentation processes. In addition, microbial growth in the rumen is enhanced in the presence of yeast leading to the delivery of a greater amount of microbial protein to the duodenum and high nitrogen retention. Single-celled fungi yeast has demonstrated its ability to increase fibre digestibility and lower faecal output of organic matter due to improved digestion of organic matter, which subsequently improves animal productivity. Yeast also has the ability to alter the fermentation process in the rumen in a way that reduces methane formation. Furthermore, yeast inclusion in ruminant diets has been reported to decrease toxins absorption such as mycotoxins and promote epithelial cell integrity. This review article provides information on the impact of single-celled fungi yeast as a feed supplement on ruminal microbiota and its function to improve the health and productive longevity of ruminants.     

Strategies for optimizing nitrogen use by ruminants

The efficiency of N utilization in ruminants is typically low (around 25%) and highly variable (10% to 40%) compared with the higher efficiency of other production animals. The low efficiency has implications for the production performance and environment. Many efforts have been devoted to improving the efficiency of N utilization in ruminants, and while major improvements in our understanding of N requirements and metabolism have been achieved, the overall efficiency remains low. In general, maximal efficiency of N utilization will only occur at the expense of some losses in production performance. However, optimal production and N utilization may be achieved through the understanding of the key mechanisms involved in the control of N metabolism. Key factors in the rumen include the efficiency of N capture in the rumen (grams of bacterial N per grams of rumen available N) and the modification of protein degradation. Traditionally, protein degradation has been modulated by modifying the feed (physical and chemical treatments). Modifying the rumen microflora involved in peptide degradation and amino acid deamination offers an alternative approach that needs to be addressed. Current evidence indicates that in typical feeding conditions there is limited net recycling of N into the rumen (blood urea-N uptake minus ammonia-N absorption), but understanding the factors controlling urea transport across the rumen wall may reverse the balance to take advantage of the recycling capabilities of ruminants. Finally, there is considerable metabolism of amino acids (AA) in the portal-drained viscera (PDV) and liver. However, most of this process occurs through the uptake of AA from the arterial blood and not during the 'absorptive' process. Therefore, AA are available to the peripheral circulation and to the mammary gland before being used by PDV and the liver. In these conditions, the mammary gland plays a key role in determining the efficiency of N utilization because the PDV and liver will use AA in excess of those required by the mammary gland. Protein synthesis in the mammary gland appears to be tightly regulated by local and systemic signals. The understanding of factors regulating AA supply and absorption in the mammary gland, and the synthesis of milk protein should allow the formulation of diets that increase total AA uptake by the mammary gland and thus reduce AA utilization by PDV and the liver. A better understanding of these key processes should allow the development of strategies to improve the efficiency of N utilization in ruminants.     

Lifetime productivity of dairy cows in smallholder farming systems of the Central highlands of Kenya

Evaluation of lifetime productivity is sensible to target interventions for improving productivity of smallholder dairy systems in the highlands of East Africa, because cows are normally not disposed of based on productive reasons. Feeding strategies and involuntary culling may have long-term effects on productive (and therefore economic) performance of dairy systems. Because of the temporal scale needed to evaluate lifetime productivity, experimentation with feedstuffs in single lactations is not enough to assess improvements in productivity. A dynamic modelling approach was used to explore the effect of feeding strategies on the lifetime productivity of dairy cattle. We used LIVSIM (LIVestock SIMulator), an individual-based, dynamic model in which performance depends on genetic potential of the breed and feeding. We tested the model for the highlands of Central Kenya, and simulated individual animals throughout their lifetime using scenarios with different diets based on common feedstuffs used in these systems (Napier grass, maize stover and dairy concentrates), with and without imposing random mortality on different age classes. The simulations showed that it is possible to maximise lifetime productivity by supplementing concentrates to meet the nutrient requirements of cattle during lactation, and during early development to reduce age at first calving and extend productive life. Avoiding undernutrition during the dry period by supplementing the diet with 0.5 kg of concentrates per day helped to increase productivity and productive life, but in practice farmers may not perceive the immediate economic benefits because the results of this practice are manifested through a cumulative, long-term effect. Survival analyses indicated that unsupplemented diets prolong calving intervals and therefore, reduce lifetime productivity. The simulations with imposed random mortality showed a reduction of 43% to 65% in all productivity indicators. Milk production may be increased on average by 1400 kg per lactation by supplementing the diet with 5 kg of concentrates during early lactation and 1 kg during late lactation, although the optimal supplementation may change according to milk and concentrate prices. Reducing involuntary culling must be included as a key goal when designing interventions to improve productivity and sustainability of smallholder dairy systems, because increasing lifetime productivity may have a larger impact on smallholders’ income than interventions targeted to only improving daily milk yields through feeding strategies.     

Reducing dietary protein in dairy cow diets: implications for nitrogen utilization,milk production,welfare and fertility

In light of increasing global protein prices and with the need to reduce environmental impact of contemporary systems of milk production, the current review seeks to assess the feasibility of reducing levels of dietary CP in dairy cow diets. At CP levels between 140 and 220 g/kg DM there is a strong positive relationship between CP concentration and dry matter intake (DMI). However, such effects are modest and reductions in DMI when dietary CP is below 180 g/kg DM can be at least partially offset by improving the digestibility and amino acid profile of the undegradable protein (UDP) component of the diet or by increasing rumen fermentable energy. Level and balance of intestinally absorbable amino acids, in particular methionine and lysine, may become limiting at lower CP concentrations. In general the amino acid composition of microbial protein is superior to that of UDP, so that dietary strategies that aim to promote microbial protein synthesis in the rumen may go some way to correcting for amino acid imbalances in low CP diets. For example, reducing the level of NDF, while increasing the proportion of starch, can lead to improvements in nitrogen (N) utilisation as great as that achieved by reducing dietary CP to below 150 g/kg. A systematic review and meta-analysis of responses to rumen protected forms of methionine and lysine was conducted for early/mid lactation cows fed diets containing ⩽150 g CP/kg DM. This analysis revealed a small but significant (P=0.002) increase in milk protein yield when cows were supplemented with these rumen protected amino acids. Variation in milk and milk protein yield responses between studies was not random but due to differences in diet composition between studies. Cows fed low CP diets can respond to supplemental methionine and lysine so long as DMI is not limiting, metabolisable protein (MP) is not grossly deficient and other amino acids such as histidine and leucine do not become rate limiting. Whereas excess dietary protein can impair reproduction and can contribute to lameness, there is no evidence to indicate that reducing dietary CP levels to around 140 to 150 g CP/kg DM will have any detrimental effect on either cow fertility or health. Contemporary models that estimate MP requirements of dairy cows may require refinement and further validation in order to predict responses with low CP diets.     

丁酸调控幼龄反刍动物瘤胃上皮发育研究进展

瘤胃是反刍动物营养物质消化吸收和代谢的重要器官,其发育状态直接影响反刍动物生产性能和健康。初生犊牛和羔羊,瘤胃功能尚未发育完全,不能够充分消化和吸收固体饲料。因此,在幼龄时期,通过营养调控手段促进反刍动物的瘤胃发育对维持动物健康及提高生产性能具有重要意义。丁酸是瘤胃微生物降解植物性饲料的主要产物,也是瘤胃上皮及宿主的重要能量来源。丁酸调控幼龄反刍动物瘤胃上皮发育是一个历久弥新的话题。主要介绍了幼龄反刍动物瘤胃上皮形态及功能的发育以及丁酸调控幼龄反刍动物瘤胃上皮发育的研究进展。     

Effects of lowering crude protein supply alone or in a combination with essential oils on productivity,rumen function and nutrient utilization in dairy cows

Lowering dietary protein concentration is known to decrease urinary nitrogen (N) losses and increase milk N efficiency in dairy cows, but it may negatively affect animal productivity. Plant-derived essential oils (EO) may alleviate these negative effects by improving the efficiency of rumen fermentation in cows fed reduced feed protein diets. The experiment was conducted to investigate the effects of lowering crude protein (CP) supply alone or in a combination with an EO product on feed intake, milk production and composition, rumen fermentation, total tract digestibility and N utilization in dairy cows. Twenty-one Holstein cows were used in a replicated 3 × 3 Latin square design experiment. Each period consisted of 14 days for adaptation and 14 days for data collection and sampling. Cows were randomly assigned to one of three experimental diets: a 165 g/kg CP diet (control), a 155 g/kg CP diet (LCP) and LCP supplemented with 35 g/day per cow EO (LCPEO). The dry matter (DM) intake was decreased by LCP and LCPEO compared with the control; there was no effect of EO on DM intake. Milk yield and composition and feed efficiency were similar among treatments. Ruminal pH, lactate, ammonia and volatile fatty acids concentrations were not affected by treatment, except increased valerate concentration by LCPEO compared with LCP. The supplementation of EO tended to decrease protozoal counts. The LCP and LCPEO increased total tract digestibility of DM and organic matter and decreased CP digestibility compared with the control. Supplementation with EO did not affect total tract digestibility of dietary nutrients compared with the control or LCP. The LCP and LCPEO decreased urinary and fecal N excretions and increased milk N efficiency; nitrogen losses were not affected by EO. In this study, lowering dietary CP by 10 g/kg decreased urinary and fecal N excretion without affecting productivity. The supplementation of EO to LCP had only minor effects on rumen fermentation and did not affect productivity, digestibility and N excretion in lactating dairy cows.     

The rumen: a unique source of enzymes for enhancing livestock production

Increasing competition in the livestock industry has forced producers to cut costs by adopting new technologies aimed at increasing production efficiency. One particularly promising technology is feeding enzymes as supplements for animal diets. Supplementation of diets for non-ruminants (e.g., swine and poultry) with fibrolytic enzymes, such as cellulases, xylanases and beta-glucanases, increases the feed conversion efficiency and growth rate of the animals. Enzymatic hydrolysis of plant cell wall polymers (e.g., cellulose, xylan, beta-glucans) releases glucose and xylose and eliminates the antinutritional effects of beta-glucans and arabinoxylans. Enzyme supplementation of diets for ruminants has also been shown to improve growth performance, even though the rumen itself represents the most potent fibrolytic fermentation system known. Implementation of this technology in the livestock industry has been limited largely because of the cost of development and production of enzymes. Over the last decade, however, developments in recombinant DNA technology have increased the efficiency of existing microbial production systems and facilitated exploitation of alternative sources of industrial enzymes. The ruminal ecosystem is among the novel enzyme sources currently being explored. Understanding the role of enzymes in feed digestion through characterization of the enzymology and genetics involved in digestion of feedstuffs by ruminants will provide insight required to improve the products currently available to producers. Characterization of genes encoding a variety of hydrolytic enzymes, such as cellulases, xylanases, beta-glucanases, amylases, pectinases, proteases, phytases and tannases, will foster the development of more efficacious enzyme supplements and enzyme expression systems for enhancing nutrient utilization by domestic animals. Characteristics of the original source organism need no longer restrict the production of a useful enzyme. Recent reports of transgenic plants expressing fibrolytic or phytase activity and of transgenic mice able to produce endoglucanase in the pancreas speak to the feasibility of improving feed digestion through genetic modification of the feedstuffs and the animals.     

Effects of dehydrated lucerne and soya bean meal on milk production and composition,nutrient digestion,and methane and nitrogen losses in dairy cows receiving two different forages

Dehydrated lucerne is used as a protein source in dairy cow rations, but little is known about the effects of lucerne on greenhouse gas production by animals. Eight Holstein dairy cows (average weight: 582 kg) were used in a replicated 4×4 Latin square design. They received diets based on either maize silage (M) or grass silage (G) (45% of diet on dry matter (DM) basis), with either soya bean meal (15% of diet DM) completed with beet pulp (15% of diet DM) (SP) or dehydrated lucerne (L) (30% of diet DM) as protein sources; MSP, ML, GSP and GL diets were calculated to meet energy requirements for milk production by dairy cows and degradable protein for rumen microbes. Dry matter intake (DMI) did not differ among diets (18.0 kg/day DMI); milk production was higher with SP diets than with L diets (26.0 v. 24.1 kg/day), but milk production did not vary with forage type. Milk fatty-acid (FA) composition was modified by both forage and protein sources: L and G diets resulted in less saturated FA, less linoleic acid, more trans-monounsaturated FA, and more linolenic acid than SP and M diets, respectively. Enteric methane (CH₄) production, measured by the SF₆ tracer method, was higher for G diets than for M diets, but did not differ with protein source. The same effects were observed when CH₄ was expressed per kg milk. Minor effects of diets on rumen fermentation pattern were observed. Manure CH₄ emissions estimated from faecal organic matter were negatively related to diet digestibility and were thus higher for L than SP diets, and higher for M than G diets; the resulting difference in total CH₄ production was small. Owing to diet formulation constraints, N intake was higher for SP than for L diets; interaction between forage type and protein source was significant for N intake. The same statistical effects were found for N in milk. Faecal and urinary N losses were determined from total faeces and urine collection. Faecal N output was lower for M than for G diets but did not differ between protein sources. Urinary N output did not differ between forage types, but was lower for cows fed L diets than for cows fed SP diets, potentially resulting in lower ammonia emissions with L diets. Replacing soya bean meal plus beet pulp with dehydrated lucerne did not change CH₄ production, but resulted in more N in faeces and less N in urine.     

Review: Authentication of grass-fed meat and dairy products from cattle and sheep

Meat and dairy products derived from grassland carry premium values and sensory and nutritional qualities that aroused much interest for authentication methods to guarantee grassland origin claims. This article reviews the current state of knowledge on the authentication of meat and dairy of grassland origin from food analysis in both cattle and sheep. A range of methods alone or combined, involving analysis of elemental or molecular constituents of food product and fingerprinting profiling combined with chemometrics, have been developed and proved useful to differentiate contrasted feeding regimes and authenticate grass-fed meat and dairy. Their robustness and discriminatory reliability in more complex feeding conditions, such as in the case of dietary switches or when grass only makes up part of the animal’s diet, are under active investigation. Our review highlights the possibilities and limitations of these methods, the latter being chiefly posed by variations in the quantity, characteristics and composition of grassland feedstuffs consumed by animals, which are nevertheless inherent to grassland-based production systems, variations in animal responses within and across breeds, and difficulties in detecting the consumption of non-grass feedstuffs by the animal. It also highlights a number of issues for consideration, points of caution and caveats in applying these methods. Scientists agree that much of the research carried out so far has been a ‘proof of concept’ type and that efforts should be made in the future to develop more databases to help gain genericity and robustness.     

Relationship between efficiency of nitrogen utilization and isotopic nitrogen fractionation in dairy cows: contribution of digestion v. metabolism?

Animal tissues are naturally ¹⁵N enriched relative to their diet and the extent of this difference (Δ¹⁵N_animal-diet) has been correlated to the efficiency of N assimilation in different species. The rationale is that transamination and deamination enzymes, involved in amino acid metabolism are likely to preferentially convert amino groups containing ¹⁴N over ¹⁵N. However, in ruminants the contribution of rumen bacterial metabolism relative to animal tissues metabolism to naturally enrich animal proteins in terms of ¹⁵N has been not assessed yet. The objective of this study was to assess the impact of rumen and digestion processes on the relationship between Δ¹⁵N_animal-diet and efficiency of N utilization for milk protein yield (milk N efficiency (MNE); milk N yield/N intake) as well as the relationship between the ¹⁵N natural abundance of rumen bacteria and the efficiency of N use at the rumen level. Solid- and liquid-associated rumen bacteria, duodenal digesta, feces and plasma proteins were obtained (n=16) from four lactating Holstein cows fed four different diets formulated at two metabolizable protein supplies (80% v. 110% of protein requirements) crossed by two different dietary energy source (diets rich in starch v. fiber). We measured the isotopic N fractionation between animal and diet (Δ¹⁵N_animal-diet) in these different body pools. The Δ¹⁵N_animal-diet was negatively correlated with MNE when measured in solid-associated rumen bacteria, duodenal digesta, feces and plasma proteins, with the strongest correlation found for the latter. However, our results showed a very weak ¹⁵N enrichment of duodenal digesta (Δ¹⁵N_{duodenal digesta-diet} mean value=0.42) compared with that observed in plasma proteins (Δ¹⁵N_{plasma protein-diet} mean value=2.41). These data support the idea that most of the isotopic N fractionation observed in ruminant proteins (Δ¹⁵N_{plasma protein-diet}) has a metabolic origin with very little direct impact of the overall digestion process on the existing relationship between Δ¹⁵N_{plasma protein-diet} and MNE. The ¹⁵N natural abundance of rumen bacteria was not related to either rumen N efficiency (microbial N/available N) or digestive N efficiency (metabolizable protein supply/CP intake), but showing a modest positive correlation with rumen ammonia concentration. When using diets not exceeding recommended protein levels, the contribution of rumen bacteria and digestion to the isotopic N fractionation between animal proteins and diet is low. In our conditions, most of the isotopic N fractionation (Δ¹⁵N_{plasma protein-diet}) could have a metabolic origin, but more studies are warranted to confirm this point with different diets and approaches.     

Effects of faba bean,blue lupin and rapeseed meal supplementation on nitrogen digestion and utilization of dairy cows fed grass silage-based diets

There is increasing interest in using locally produced protein supplements in dairy cow feeding. The objective of this experiment was to compare rapeseed meal (RSM), faba beans (FBs) and blue lupin seeds (BL) at isonitrogenous amounts as supplements of grass silage and cereal based diets. A control diet (CON) without protein supplement was included in the experiment. Four lactating Nordic Red cows were used in a 4 × 4 Latin Square design with four 21 d periods. The milk production increased with protein supplementation but when expressed as energy corrected milk, the response disappeared due to substantially higher milk fat concentration with CON compared to protein supplemented diets. Milk protein output increased by 8.5, 4.4 and 2.7% when RSM, FB and BL were compared to CON. The main changes in rumen fermentation were the higher propionate and lower butyrate proportion of total rumen volatile fatty acids when the protein supplemented diets were compared to CON. Protein supplementation also clearly increased the ruminal ammonia N concentration. Protein supplementation improved diet organic matter and NDF digestibility but efficiency of microbial protein synthesis per kg organic matter truly digested was not affected. Flow of microbial N was greater when FB compared to BL was fed. All protein supplements decreased the efficiency of nitrogen use in milk production. The marginal efficiency (amount of additional feed protein captured in milk protein) was 0.110, 0.062 and 0.045 for RSM, FB and BL, respectively. The current study supports the evidence that RSM is a good protein supplement for dairy cows, and this effect was at least partly mediated by the lower rumen degradability of RSM protein compared to FB and BL. The relatively small production responses to protein supplementation with simultaneous decrease in nitrogen use efficiency in milk production suggest that economic and environmental consequences of protein feeding need to be carefully considered.     

Diet-induced bacterial immunogens in the gastrointestinal tract of dairy cows: Impacts on immunity and metabolism

Dairy cows are often fed high grain diets to meet the energy demand for high milk production or simply due to a lack of forages at times. As a result, ruminal acidosis, especially subacute ruminal acidosis (SARA), occurs frequently in practical dairy production. When SARA occurs, bacterial endotoxin (or lipopolysaccharide, LPS) is released in the rumen and the large intestine in a large amount. Many other bacterial immunogens may also be released in the digestive tract following feeding dairy cows diets containing high proportions of grain. LPS can be translocated into the bloodstream across the epithelium of the digestive tract, especially the lower tract, due to possible alterations of permeability and injuries of the epithelial tissue. As a result, the concentration of blood LPS increases. Immune responses are subsequently caused by circulating LPS, and the systemic effects include increases in concentrations of neutrophils and the acute phase proteins such as serum amyloid-A (SAA), haptoglobin (Hp), LPS binding protein (LBP), and C-reactive protein (CRP) in blood. Entry of LPS into blood can also result in metabolic alterations. Blood glucose and nonesterified fatty acid concentrations are enhanced accompanying an increase of blood LPS after increasing the amount of grain in the diet, which adversely affects feed intake of dairy cows. As the proportions of grain in the diet increase, patterns of plasma β-hydoxybutyric acid, cholesterol, and minerals (Ca, Fe, and Zn) are also perturbed. The bacterial immunogens can also lead to reduced supply of nutrients for synthesis of milk components and depressed functions of the epithelial cells in the mammary gland. The immune responses and metabolic alterations caused by circulating bacterial immunogens will exert an effect on milk production. It has been demonstrated that increases in concentrations of ruminal LPS and plasma acute phase proteins (CRP, SAA, and LBP) are associated with declines in milk fat content, milk fat yield, 3.5% fat-corrected milk yield, as well as milk energy efficiency.     

Rumen fungi: morphological types from Georgia cattle and the attack on forage cell walls

Fungal colonies developing in anaerobic media from zoospores in rumen fluid from cows eating Cynodon dactylon or Medicago sativa included types showing monocentric and polycentric growth. High energy supplements added to diets of Sorghum bicolor silage increased fungal numbers in the rumen, but increases were also affected by the history and predisposition of the animal. Mixed fungal types in rumen fluid and pure cultures of isolates showing monocentric and polycentric growth degraded and weakened lignocellulosic tissues and penetrated the cuticle of C. dactylon leaf blades. By weakening or degrading recalcitrant structures in forages, rumen fungi may alter physical parameters of plants that influence utilization of fibre by ruminants.     

Combinations of non-invasive indicators to detect dairy cows submitted to high-starch-diet challenge

High-starch diets (HSDs) fed to high-producing ruminants are often responsible for rumen dysfunction and could impair animal health and production. Feeding HSDs are often characterized by transient rumen pH depression, accurate monitoring of which requires costly or invasive methods. Numerous clinical signs can be followed to monitor such diet changes but no specific indicator is able to make a statement at animal level on-farm. The aim of this pilot study was to assess a combination of non-invasive indicators in dairy cows able to monitor a HSD in experimental conditions. A longitudinal study was conducted in 11 primiparous dairy cows fed with two different diets during three successive periods: a 4-week control period (P1) with a low-starch diet (LSD; 13% starch), a 4-week period with an HSD (P2, 35% starch) and a 3-week recovery period (P3) again with the LSD. Animal behaviour was monitored throughout the experiment, and faeces, urine, saliva, milk and blood were sampled simultaneously in each animal at least once a week for analysis. A total of 136 variables were screened by successive statistical approaches including: partial least squares-discriminant analysis, multivariate analysis and mixed-effect models. Finally, 16 indicators were selected as the most representative of a HSD challenge. A generalized linear mixed model analysis was applied to highlight parsimonious combinations of indicators able to identify animals under our experimental conditions. Eighteen models were established and the combination of milk urea nitrogen, blood bicarbonate and feed intake was the best to detect the different periods of the challenge with both 100% of specificity and sensitivity. Other indicators such as the number of drinking acts, fat:protein ratio in milk, urine, and faecal pH, were the most frequently used in the proposed models. Finally, the established models highlight the necessity for animals to have more than 1 week of recovery diet to return to their initial control state after a HSD challenge. This pilot study demonstrates the interest of using combinations of non-invasive indicators to monitor feed changes from a LSD to a HSD to dairy cows in order to improve prevention of rumen dysfunction on-farm. However, the adjustment and robustness of the proposed combinations of indicators need to be challenged using a greater number of animals as well as different acidogenic conditions before being applied on-farm.     

Comparative Metabolite Fingerprinting of the Rumen System during Colonisation of Three Forage Grass (Lolium perenne L.) Varieties

The rumen microbiota enable ruminants to degrade complex ligno-cellulosic compounds to produce high quality protein for human consumption. However, enteric fermentation by domestic ruminants generates negative by-products: greenhouse gases (methane) and environmental nitrogen pollution. The current lack of cultured isolates representative of the totality of rumen microbial species creates an information gap about the in vivo function of the rumen microbiota and limits our ability to apply predictive biology for improvement of feed for ruminants. In this work we took a whole ecosystem approach to understanding how the metabolism of the microbial population responds to introduction of its substrate. Fourier Transform Infra Red (FTIR) spectroscopy-based metabolite fingerprinting was used to discriminate differences in the plant-microbial interactome of the rumen when using three forage grass varieties (Lolium perenne L. cv AberDart, AberMagic and Premium) as substrates for microbial colonisation and fermentation. Specific examination of spectral regions associated with fatty acids, amides, sugars and alkanes indicated that although the three forages were apparently similar by traditional nutritional analysis, patterns of metabolite flux within the plant-microbial interactome were distinct and plant genotype dependent. Thus, the utilisation pattern of forage nutrients by the rumen microbiota can be influenced by subtleties determined by forage genotypes. These data suggest that our interactomic approach represents an important means to improve forages and ultimately the livestock environment.     

Polyunsaturated fatty acids and choline in dairy goats nutrition: Production and health benefits

The potential to modify milk fatty acid composition and milk production by dietary administration of marine oils rich in n-3 PUFAs in goats diets is reviewed. Moreover animal and human health implications are considered. Role of nutrition in dairy goats for enhancing content of CLA in milk fat is also discussed. At last, rumen protected choline supplementation is evaluated to improve productive performance and metabolic health. While the effects of n-3 PUFAs administration on goat productive performance seem to depend on many factors, fish oil administration has been extensively shown to lower average concentration of C18:0 and saturated fatty acids, with a relative increase of C16:1, C18:3 n-3 and very long-chain n-3 PUFAs. Positive results have been evidenced in animals health following administration of EPA and DHA from fish oil, leading to increased phagocytic activity with no effects on extracellular ROS production in incubated goats cells. The nutritional and health properties of goat's milk could be further improved by increasing the content of CLA in milk fat. Provision of PUFAs from fresh pasture and plant lipids, mainly C18:2 n-6 and C18-3 n3 which serve as precursor for trans C18:1 formation in the rumen, have proved to enhance content of CLA in goat milk fat. Marine oils rich in n-3 PUFAs have been shown to be very effective at increasing CLA content in bovine milk, but very scarce data are available on dairy goats.Rumen protected choline has been show to increase productive performance, particularly milk production, fat percentage, and fat and protein yield without detrimental effects on methyl groups, thus reducing BHBA plasma content and hepatocellular lipid accumulation around transition.However the magnitude of the production response seems to be affected by the composition of the diet, and other factors as already reported for n-3 PUFAs administration.     

Effects of partial replacement of soybean meal with other protein sources in diets of lactating cows

The protein nutrition of dairy cows is of great importance because of its direct influence on milk production, reproductive efficiency, and feeding cost. Eight first-lactation Holstein cows were randomly assigned to two contemporary 4 × 4 Latin squares in a 2 × 2 factorial design to evaluate the effects of replacing soybean meal with yeast-derived microbial protein (YMP) as a protein source (0% or 1.5% of dry matter (DM)) and its combination with slow-release urea (SRU; 0% or 0.75% of DM) on DM intake and milk production and composition, as well as blood parameters and nitrogen balance. Each experimental period lasted 28 days, with 21 days of adaptation and 7 days of data collection. The diets were formulated to attend the nutritional recommendations of the National Research Council and consisted of 49% forage (47% corn silage and 2% Tifton hay) and 51% concentrate, with 16.8% CP and 1.6 Mcal net energy for lactation/kg DM. For diets without YMP, the inclusion of SRU decreased DM intake, milk production as well as N intake and balance, but did not affect efficiency of production, milk composition or most of blood parameters. On the contrary, for diets with YMP, DM intake and milk production were increased by inclusion of SRU, while minor effects were observed for milk efficiency and composition, blood parameters as well as N intake, excretion and balance. When diets with SRU were compared, the inclusion of YMP increased DM intake, 4% fat-corrected milk, and N intake and balance (P<0.05), with no differences in milk production (kg/day), milk energy, efficiency of milk production or most of the blood parameters. For diets without SRU, YMP inclusion decreased DM intake, milk production, milk energy, N intake, fecal N and N balance (P<0.05), with no effects on milk efficiency and composition, or most of blood parameters. In conclusion, the use of YMP, SRU or both as partial substitutes of soybean meal in the diet of lactating cows has no negative effects on productivity parameters.     

Evaluating model predictions of partitioning nitrogen excretion using the dairy cow model, Molly

Computer models of dairy cow digestion and metabolism are useful tools to evaluate rations and estimate nitrogen (N) excretion. Using models, different management strategies and/or feeding practices can be evaluated and their impact on N excretion explored before implementation. Critical parameters for developing nutrient management plans can be identified to help reduce the impact of animal manure. However, before a model is implemented, errors associated with predictions and limitations of the model must be known. Otherwise, proposed management and feeding changes may not result in effective measures to optimally manage N excretion. The objective of this research effort was to determine whether or not Molly, a dynamic model of dairy cow digestion and metabolism [Baldwin, R.L., 1995. Modeling Ruminant Digestion and Metabolism. Chapman & Hall, UK], could be used to predict N excretion. In Molly, predictions of N excretion are based on level of milk production (ucells) and rate of insoluble protein hydrolysis (KPiAa). Accurate estimation of N excretion patterns would indicate that understanding of N metabolism as represented in Molly is adequate. Failures indicate that more research is needed. To examine estimates of N excretion, N balance data from 18 publications in the Journals of Dairy and Animal Science were simulated using Molly. Input data required included diet composition (N intake), initial bodyweight, days in milk, dry matter intake and milk production. A total of 73 different simulations (73 different diets) with N intakes ranging from 0.19 to 0.78 kg/d and crude proteins of 106–206 g/kg were run. Model outputs of milk, milk protein, faecal N, urinary N and milk N were compared to observed data. Overall, the model simulated reality well. Mean bias are less than 11% for milk yield, milk protein, faecal N, urinary N and milk N with coefficients of determination of 0.94, 0.73, 0.70, 0.80 and 0.88, respectively. Mean absolute errors and root mean square prediction errors are also low compared with observed mean milk, milk protein, faecal N, urinary N and milk N. N excretion losses due to volatilisation were not included in model estimates of faecal N and urinary N. Predicted rates of insoluble protein hydrolysis (KPiAa) from estimating N excretion indicated that current estimates of fractions of undegraded protein for individual feedstuffs in Rumen Nitrogen Usage [National Research Council (NRC), 1985. Ruminant Nitrogen Usage. National Academy Press, Washington, DC] are not adequate.     

Milk: the new white gold? Milk production options for smallholder farmers in Southern Mali

Until the turn of the century, farmers in West Africa considered cotton to be the ‘white gold’ for their livelihoods. Large fluctuations in cotton prices have led farmers to innovate into other business including dairy. Yet the productivity of cows fed traditional diets is very poor, especially during the long dry season. This study combines earlier published results of farmer participatory experiments with simulation modelling to evaluate the lifetime productivity of cows under varying feeding strategies and the resulting economic performance at farm level. We compared the profitability of cotton production to the innovation of dairy. The results show that milk production of the West African Méré breed could be expanded if cows are supplemented and kept stall-fed during the dry season. This option seems to be profitable for better-off farmers, but whether dairy will replace (some of) the role of cotton as the white gold for these smallholder farmers will depend on the cross price elasticity of cotton and milk. Farmers may (partly) replace cotton production for fodder production to produce milk if the price of cotton remains poor (below US$0.35/kg) and the milk price relatively strong (higher than US$0.38/kg). Price ratios need to remain stable over several seasons given the investments required for a change in production strategy. Furthermore, farmers will only seize the opportunity to engage in dairy if marketing infrastructure and milk markets are further developed.