Current Feeding Systems Research Articles

EMC Problems caused by Combinations of EHV Transmission Lines and Electrified Railway Lines

The percentage of electricity produced by renewable energy sources grows rapidly during last years. But high-power renewable energy sources like offshore or onshore wind farms in coastal regions are located very often far from consumers. The task of the energy transport over long distances becomes more and more important. Due to the difficulties finding new corridors for the extra high voltage (EHV) transmission lines in densely populated countries with developed infrastructure is often recommended to combine the new transmission line with other infrastructure objects like railways, highways and other transmission lines. One of theoretical possibilities is the use of common pylons for the installation of a new EHV transmission line together with catenary of electrified railway lines. Another one is the laying of HVDC cable parallel to the rail line. The proximity of different current feeding systems causes the electromagnetic interaction between transmission line and catenary. These interferences can disturb the operation of both systems. On the base of mathematical modelling of electromagnetic interferences between transmission lines and catenary the interaction between both systems is considered in the offered paper.

A revised model of energy transactions and body composition in sheep.

A mechanistic, dynamic model was developed to calculate body composition in growing lambs by calculating heat production (HP) internally from energy transactions within the body. The model has a fat pool (f) and three protein pools: visceral (v), nonvisceral (m), and wool (w). Heat production is calculated as the sum of fasting heat production, heat of product formation (HrE), and heat associated with feeding (HAF). Fasting heat production is represented as a function of visceral and nonvisceral protein mass. Heat associated with feeding (HAF) is calculated as ((1 - km) x MEI), where km is partial efficiency of ME use for maintenance, and MEI = metabolizable energy intake) applies at all levels above and below maintenance. The value of km derived from data where lambs were fed above maintenance was 0.7. Protein change (dp/dt) is the sum of change in the m, v, and w pools, and change in fat is equal to net energy available for gain minus dp/dt. Heat associated with a change in body composition (HrE) is calculated from the change in protein and fat with estimated partial efficiencies of energy use of 0.4 and 0.7 for protein and fat, respectively. The model allows for individuals to gain protein while losing fat or vice versa. When evaluated with independent data, the model performed better than the current Australian feeding standards (Freer etal., 2007) for predicting protein gain in the empty body but did not perform as well as for gain of fat and fleece-free empty body weight. Models performed similarly for predicting clean wool growth. By explicit representation of the major energy using processes in the body, and through simplification of the way body composition is computed in growing animals, the model is more transparent than current feeding systems while achieving similar performance. An advantage of this approach is that the model has the potential for wider applicability across different growth trajectories and can explicitly account for the effects of systematic changes on energy transactions, such as the effects of selective breeding, growth manipulation, or environmental changes.

Energy: Protein Ratio in Ruminants: Insights from the Intragastric Infusion Technique.

Simple SummaryOne key question that has confounded nutritional scientists for years is how the ruminant responds metabolically with respect to energy and nitrogen utilisation when no exogenous energy is consumed. Fasting metabolism studies using the intragastric infusion technique (IIT) showed this to be a glucose-deficient state characterised by elevated nitrogen excretion and heat production. However, modern feeding systems continue to adopt fasting as the basis for measuring utilisation efficiency of nutritionally balanced diets, giving rise to the false concept of greater feed utilisation below than above energy maintenance. Another IIT finding was that given the animal’s genetic capacity for protein accretion and provided a rumen undegradable protein is fed, ruminants do not catabolise amino acids as an energy source but instead retain these to attain substantial gains in tissue protein deposition, fuelled by endogenous energy reserves. This suggests that endogenous fat reserves could be used to retain body protein when feed supplies are scarce or of poor nutritive value and questions the need to use high-energy diets in the finishing pre-slaughter period. Moreover, body protein and body fat deposition were also shown to be negatively correlated, contradicting current feeding systems which assume that nitrogen retention is always negative in an underfeeding situation.Studies on energy:protein ratio in ruminants are constrained by rumen fermentation since it governs nutrient metabolism and the ratio of energy:protein yielding nutrients available for absorption. By circumventing rumen fermentation, the total intragastric infusion technique (IIT) allowed objective quantification of maintenance energy and protein requirements, volatile fatty acid utilisation efficiency, efficiency of energy utilisation for maintenance (Km) and growth (Kf) and the origin of N retention responses to independent variation of energy and protein intake. This review outlines the key IIT findings and whether they are reflected in current feeding systems with implications for different production systems worldwide. Maintenance energy requirements are similar to those derived from comparative slaughter but maintenance N requirements are significantly lower. No differences in utilisation efficiency exist between acetic, propionic and butyric acids. At low energy intakes, endogenous energy reserves are utilised to retain amino acids and fuel substantial tissue protein gains. The use of fasting metabolism to measure the utilisation of nutritionally balanced diets is questioned since it is a glucose-deficient state. Inter-species differences in glucose metabolism appear to exist, suggesting that glucose requirements may be higher in cattle than sheep. The difficulty in predicting nutrient requirements, particularly protein, with any one technique is highlighted.

Estimating degradation of individual essential amino acids in fish meal and blood meal by rumen microbes in a dual-flow continuous-culture system

Current feeding systems are based on the assumption that the AA profile of rumen undegraded protein is similar to that of the original feed. The objective of this experiment was to determine rumen bacterial degradation of individual essential AA in fish meal (FM) and blood meal (BM). Eight dual-flow continuous-culture fermentors were used in a completely randomized block design with a factorial arrangement of treatments and 3 replicated periods. Fermentors were supplied with 95 g of dry matter/d of isonitrogenous diets. Treatments contained a nonprotein N source (urea and tryptone) that was substituted with increasing proportions of FM or BM (0, 33, 67, or 100%). Diets consisted of 22.0% crude protein, 35.2% neutral detergent fiber, 34.6% nonfiber carbohydrates, 2.0% ether extract, and 9.2% ash. We hypothesized that the increase in the flow of individual AA would be attributed to the increase in the supply of the AA from each protein supplement. True organic matter degradation was decreased by increasing levels of FM or BM, but did not affect degradation of neutral detergent fiber and acid detergent fiber, total volatile fatty acids (VFA) concentration, or the molar proportion of propionate. There was a substrate by level of inclusion interaction in acetate molar proportion and branched-chain VFA. Butyrate concentration decreased linearly with increasing levels of FM and BM in treatment. Changes in branched-chain VFA reflected differences in content of branched-chain AA between supplements and the level of inclusion, although the quadratic effect suggests that other factors were involved. Ammonia-N concentration showed a substrate by level of inclusion interaction. Total dietary N and AA flows increased with increasing levels of FM or BM in treatment. The efficiency of bacterial crude protein synthesis was not affected by treatment, but the flow of bacterial N decreased in FM diets as the level of FM increased. Flows of AA increased linearly with increasing levels of the respective AA from supplements. Arginine, Ile, Met and Phe were more degradable, while His was more resistant to bacterial degradation. Results suggest that the resistance to rumen bacterial degradation of individual AA varies within FM and BM protein and may affect the estimates of dietary supply of individual AA to the small intestine.

The Weight Gain and Growth of Crossbred Bulls Fed Locally Inspired Supplements Compared with Current Feeding Systems in Village Smallholdings in Malang, East Java

Growth rates of cattle in village smallholder farms are often low (0,2-0,5 kg/d) due to the ration formulation not meeting the nutrient requirements for cattle to achieve their potential live weight gain. This experiment aims to determine the growth of crossbred bulls fed a range of supplemented diets using local products comparing them to current traditional feeding system. This village was conducted in Kucur village, Dau sub-district, Malang. Fifyt cross bred aged between 1.5-2 years were allocated into five treatments; cassava-based diet by recent ACIAR-UB experiment (T1), commercial concentrate (T2), YaYa diet (T3), Santos diet (T4) and current feeding system (CFS) by smallholder farmers (T0) as the control. Cassava-based diet (T1) consisted of 50% cassava, 25% copra meal (CM) and 25% palm kernel cake (PKC). Local concentrate (T2) was bought from local cooperative in Malang. Yaya diet (T2) consisted of 30% cassava, 20% corn cob, 20% copra meal, 20% palm kernel cake and 10% rice bran. Santos diet (T4) consisted of 40 % corn cob, 20% palm kernel cake 20% rice bran, and 20% wheat pollard. Control treatment (T0) was 1 kg wheat pollard a day which was the general current feeding system by local smallholders. The experiment found that cassava-based diet (T1) supplementation showed the highest body growth compared to the other diets.

The use of insect meal as a sustainable feeding alternative in aquaculture: Current situation, Spanish consumers’ perceptions and willingness to pay

The growth of aquaculture and the increasing demand of farmed fish have led to a rise in the price of fishmeal and fish oil used in fish feeding during the last years. The experimental use of insect meal as a sustainable alternative to fish meal has recently grown. Insects are easy to rear, have a small ecological impact and have high protein content. The present work analyzes through a Discrete Choice Experiment method, the preferences and willingness to pay of Spanish consumers towards an aquaculture production system based on this protein source as ingredient in aquafeed, using the gilthead seabream as a case study. It also analyzes the information level of consumers about aquaculture and their perceptions towards its environmental impact compared to other animal production systems. This study also summarizes research advances regarding the insect meals as substitutes or complements for fish meals focusing on fish species of interest in Spain and Europe. Special emphasis was made on the limitation of their use, its impact towards the conversion feed ratio and its main nutritional problems for fish feeding, such as fatty acids and chitin. The studies showed that the use of insect meal, in particular, from the black soldier fly (Hermetia illucens), the common housefly (Musca domestica) and the mealworm (Tenebrio molitor) as an alternative of feeding in aquaculture seems to be promising both at technical-productive level and at consumer acceptance level. Results showed that Spanish consumers were willing to pay a premium for this type of fish compared to fish produced with the current feeding systems. Furthermore, the gilthead sea bream fed with insect meal was the most valued regarding its environmental impact compared to the current fish feeding systems. However, taste expectation for this fish type still low, highlighting the importance of including hedonic evaluation studies for further research.

Comparative aspects of plant tannins on digestive physiology, nutrition and microbial community changes in sheep and goats: A review.

Comparative aspects of plant tannins on digestive physiology, nutrition and microbial community in sheep and goats are discussed in the context of differences due to feed intake, digestibility, utilization of nutrients and microbial community. The purpose of this review was to present an overview of the potential benefits of tannin-containing diets for sheep and goats and specie differences in their response to tannins. It is well established that moderate level of tannins in the diet (3%-4% tannins DM) can precipitate with soluble proteins and increase protein supply to the sheep, but comparative aspects of tannin-containing diets in sheep and goats on animal performance, digestive physiology, rumen microbial changes and potential benefits to sustainable animal production by those compounds have received little attention. In addition, developing plant-based tannin-containing diets for control of rumen microbiota and rumen fermentation (e.g., methane gas) would be expected to have a greater impact on the ruminant health, productivity and emission of greenhouse gasses. The positive impacts of the plant tannin compounds mainly depend on their influence on the gut microbiome diversity and ability to generate fermentation end products (short-chain fatty acids) that have diverse biological roles. Diets which contain optimal levels of tannins have potential benefits for sustainability of small ruminant production systems. However, there is a need for an improved understanding of the utilization of tannin-containing forages to improve their management. This implies investigations of animal responses to tannin-containing forages or browse species and, in particular, a better understanding of the interactions that can arise between sheep and goats on digestion, DMD, rumen fermentation and microbial community changes. This knowledge could help to improve current feeding systems in terms of efficiency of feed use and environmental impacts (reduce methane gas production) and thus contribute to the development of a sustainable sheep and goat production.

Net energy and protein requirements for pregnancy differ between goats and sheep1

Current feeding systems for goats estimate the energy and protein requirements for pregnancy using data from sheep. The objective of this study was to predict the NE and net protein requirements for pregnancy in goats carrying single and twin fetuses and to compare these requirements with those of sheep. Data were compiled from 2 studies with dairy goats and 3 studies with sheep. These studies measured the energy content (EC) and protein content (PC) of the gravid uterus and of the mammary gland using the comparative slaughter technique. The current study was performed as a meta-analysis using an exponential model, comparing species (sheep versus goats) and litter size (single versus twin) from 50 to 140 d of pregnancy. Total EC and total PC in the gravid uterus were similar in goats and sheep carrying a single fetus. Energy and protein contents of the gravid uterus of sheep carrying twins were, on average, 29% greater than that of goats with twins from 80 to 140 d of pregnancy. During pregnancy, EC and PC of the mammary gland in goats carrying singles and twins were, on average, greater than those of sheep by 9 and 24%, respectively, for EC and by 25% for PC for both litter sizes. In conclusion, the gravid uterus and the mammary gland of goats and sheep require different amounts of energy and protein. Sheep carrying twins have the greatest daily NE and net protein requirements for pregnancy followed by goats carrying twins and both species carrying a single fetus. Therefore, it is inappropriate to adopt data from sheep to predict the net pregnancy requirements of goats, and the results found in this study could be relevant to the nutritional management of dairy goats.

Is a 10-sow unit economically sustainable? A profitability assessment of productivity amongst small-holder pig farmers, Mpumalanga, South Africa

The majority of small-holder pig farmers in Mpumalanga had between 1- and 10-sow herds. The main aim of this study is to evaluate the current government agricultural intervention (supply of 10 sows and a boar) in terms of technical and economic feasibilities and ascertain whether the small-scale pig value chain system alleviates poverty. Data were obtained from 220 randomly selected small-holder pig farmers using a semi-structured questionnaire. The results showed that 58% farrowed ≤ 10 piglets/born/sow/litter, 44.2% practiced no weaning method and many fed swill and leftovers alone (41.6%). Pair-wise association revealed that the feeding of commercial feeds had a relationship with pigs in relatively good to very good body condition. Pigs in poor body condition were positively correlated with the feeding of swill alone. The economic models for the 10-sow unit proved that pig farming is unprofitable if the current management and feeding systems that operate in the commercial industry are utilised. However, only through a combination of cooperative systems, benefits of economies of scale, reduction of preweaning mortalities and structured government inputs can pig production be profitable at this scale of production.

Protein requirements for growth in male and female Saanen goats

The objective of this study was to determine the protein requirements for the growth of intact male, female, and castrated male Saanen goats weighing 30 to 45 kg of body weight (BW) and to compare estimates of the protein requirements for maintenance (NPm) by the comparative slaughter and nitrogen balance techniques. To determine the maintenance requirements, 55 goats were assigned in a split-plot design using a 3 × 3 factorial arrangement (three sexes and three dry matter intake (DMI) levels). A linear regression of retained N (as measured by the slaughter technique and estimated from the nitrogen balance) on N intake on a daily basis was used to calculate the net protein for maintenance. The net protein requirement for weight gain (NPg) was obtained using 65 goats fed ad libitum in a completely randomized design. The first derivative of the allometric equation of protein content in the empty BW with respect to the empty BW yielded estimates of the NPg. According to the comparative slaughter technique, the estimated NPm was 1.46 g/kg of metabolic weight, which is 50% lower than the estimate from the nitrogen balance technique. When evaluating the variance of the error, the nitrogen balance also showed greater values, indicating less precision compared with that of the comparative slaughter technique. The daily NPg ranged from 155.7±10.9 to 153.4±13.5 g/kg of EBW gain for growing Saanen goats. The protein requirements (NPm and NPg) of intact male, female, and castrated male Saanen goats are similar, from 30 to 45 kg BW, in accordance with current feeding systems. Moreover, the results of the present study indicate that the estimate of NPm using the comparative slaughter technique is more precise and lower than that using the N balance technique.

Effects of diet forage proportion on maintenance energy requirement and the efficiency of metabolizable energy use for lactation by lactating dairy cows

The objective of the present study was to examine the effect of dietary forage proportion (FP) on metabolizable energy (ME) requirement for maintenance (MEm) and the efficiency of ME use for lactation (kl) in lactating dairy cows. Data used were derived from 32 calorimetric chamber experiments undertaken at our institute between 1992 and 2010, including data from 818 Holstein-Friesian cows (HF), 50 Norwegian Red cows, and 62 crossbred cows (Jersey × HF or Norwegian Red × HF). Animals were offered forage-only rations (n=66) or forage and concentrate rations (n=864) with FP ranging from 18 to 100% (dry matter basis). The effect of FP was evaluated by dividing the whole data set into 4 groups according to the FP ranges, categorized as FP <30%, FP=30 to 59%, FP=60 to 99%, and FP=100%. The MEm for individual cows was calculated from heat production minus energy losses from inefficiencies of ME use for lactation, energy retention and pregnancy, and kl was obtained from milk energy output adjusted to zero energy balance (El(0)) divided by ME available for production. Increasing FP significantly reduced ME intake and milk energy output, although the differences between the 2 low FP groups were not significant. However, increasing FP significantly increased the ratio of heat production over ME intake and MEm (MJ/kg0.75), with the exception that the increases did not reach significance in heat production/ME intake between FP <30% and FP=30 to 59%, or in MEm between FP=60 to 99% and FP=100%. However, the FP had no significant effect on the kl values, which were similar among the 4 groups of cows. The effect of FP was also evaluated using the linear mixed regression technique relating El(0) to ME intake. The results demonstrated that with a common regression coefficient (slope), the regression constants (intercepts) taken as net energy requirement for maintenance significantly increased with increasing FP. However, the increase between the 2 high FP groups did not research significance. It is concluded that increasing diet FP had no effects on kl but significantly increased maintenance energy requirement (MJ/kg0.75). These results indicate that using the current energy feeding systems to ration dairy cows managed under low input systems may underestimate their nutrient requirements, because the majority of feeding systems adopted globally do not differentiate the maintenance energy requirements between low and high forage input systems.

Maintenance energy requirements of young Holstein cattle from calorimetric measurements at 6, 12, 18, and 22 months of age

Twenty five-month old Holstein cattle (10 steers and 10 heifers) were used in a four-period (28d/period) study with measurements made at the age of 6, 12, 18, and 22 months, to evaluate effects of gender on energy utilization efficiency and maintenance energy requirement. Cattle were offered perennial ryegrass silage mixed with concentrates. In each period, the cattle were housed together in a cubicle accommodation for the first 20d, individually in metabolism units for the next 3d, and then in indirect open-circuit respiration calorimeter chambers for the final 5d with feed intake, feces and urine outputs, and gaseous exchange measured during the final 4d. There was no difference (P>0.05) in any period between gender groups in terms of growth performance, energy intake, energy output, or energetic efficiency, with the exception of period three when the steers had a greater (P<0.05) feed and energy intake than heifers. Data from the two groups were therefore pooled to develop relationships between metabolizable energy (ME) intake and retained energy (RE) for each measurement period and for the whole experimental period. Retained energy was strongly related to ME intake (P<0.001), with R2 values ranging from 0.85 to 0.93. Net energy (NE) and ME requirements for maintenance (NEm and MEm) derived from these relationships were greater for cattle at the age of 6 months than those at 12, 18, and 22 months (NEm=0.57, 0.48, 0.47, and 0.41MJ/kg0.75; and MEm=0.78, 0.62, 0.59, and 0.63MJ/kg0.75, respectively). These maintenance energy requirements were greater than those recommended in energy feeding systems currently used in Europe, North America, and Australia. The results indicate that current feeding systems may underestimate maintenance requirements for young dairy cattle, resulting in a reduced estimate of the efficiency of production.

Evaluation of food industry by-products as feed in semi-arid dairy farming systems: the case of Jordan

Dairy feeding systems in many semi-arid countries are based on imported concentrates and forages. This has economic and ecological implications given the increase in global feed prices and greenhouse gas (GHG) emissions from land use change. This paper aims to explore alternative dairy feeding systems under semi-arid conditions, using Jordan as an example. The feedings systems under investigation vary in their share of food industry by-products (replacing concentrates in the diet) and are compared against the current concentrate-based feeding systems. The systems are evaluated against three criteria: their nutritional value, their impact on the cost of milk production, and their GHG mitigation potential. Feed samples from eleven food industry by-products and ten conventional feeds were collected from food factories and from three typical dairy farms, representing the typical large-, medium- and small-scale farm types, respectively. Feed samples were analysed for their chemical composition and metabolisable energy contents. In addition, economic and production farm data were collected and entered into a model for GHGs calculation and economic evaluation. The results suggest that inclusion of locally available food industry by-products in the rations of milk cows in semi-arid production systems can be instrumental in reducing production costs and mitigating GHG emissions. Cost of milk production in the model farms can be lowered by up to 14 %; mitigation of CO2 eq. emission ranged between 70 and 290 g CO2 eq./kg milk. The degree to which these benefits can be reaped is positively related to the level of inclusion of by-product feeds in lactating cows’ diets.

Characterizing feeds and feed availability in Sud-Kivu province, DR Congo

Animal husbandry in the Sud-Kivu province of the Democratic Republic of the Congo is gradually moving towards stall feeding, due to demographic pressure (Battistin et al. 2009) and scarcity of collectable forages (DSRP-RDC 2005). Therefore, lack of available feed is considered one of the main constraints faced by livestock production, especially in the dry season (Katunga et al. 2011; Maass et al. 2012). Unaffordable, fluctuating prices and scarcity of feed concentrates and the lack of improved forages adapted to marginal conditions, making them non-competitive with food crops, further exacerbate the livestock feeding situation. This study aimed to assess specific constraints and opportunities in the current feeding systems, as well as feed availability in this area.

New Methodologies for Integrating Algae with CO2 Capture

It is generally recognized, that algae could be an interesting option for reducing CO2 emissions. Based on light and CO2, algae can be used for the production various economically interesting products. Current algae cultivation techniques, however, still present a number of limitations. Efficient feeding of CO2, especially on a large scale, is one of them. Current methods for CO2 feeding to algae cultures rely on the sparging pure CO2 or directly from flue gas. The limiting factor in this system is the solubility of CO2in water, which demands a considerable amount of energy for an effective gas to liquid transfer and leads to losses to the atmosphere. Due to the current ineffective methods for CO2 introduction into algae ponds very large surface areas would be required for enough ponds to capture a considerable amount of the CO2. At TNO, an amine-based method have been developed for algae production utilization of CO2 where algae is used as photochemical desorber of CO2 from an absorption liquid. This methods brings the advantage of higher CO2 removal efficiencies compared to current CO2 feeding systems for algae and lower operational cost compared to both conventional CO2 removal using amines and conventional autotrophic algae cultivation.

Reliability Modeling of Direct Current Power Feeding Systems for Green Data Center

Data center is an information hub and resource for information-centric society. Since data center houses hundreds to ten thousands servers, networking and communication equipment, and supporting systems energy saving is one of the hottest issues for green data center. Among several solutions for green data center this paper introduces higher voltage direct current (DC) power feeding system. Contrary to legacy alternating current (AC) power feeding system equipped with Uninterruptible Power Supply (UPS), higher voltage DC power feeding system is reported to be a more energy efficient and reliable solution for green data center thanks to less AC/DC and DC/AC conversions. Main focus of this paper is on reliability issue for reliable and continuous operation of higher voltage DC power feeding system. We present different types of configuration of the power feeding systems according to the level of reliability. We analyze the reliability of the power feeding systems based on M/M/1/N+1/N+1 queueing model. Operation of the power feeding system in case of failure is also presented.

New Methodologies for the Integration of Power Plants with Algae Ponds

It is generally recognized that algae could be an interesting option for reducing CO2 emissions. Based on light and CO2, algae can be used for the production various economically interesting products. Current algae cultivation techniques, however, still present a number of limitations. Efficient feeding of CO2, especially on a large scale, is one of them. At TNO, two novel methods have been developed for the integration of flue-gas from power plants with algae production for the capture and utilization of CO2. The first method can be described as being amine based whilst the second is carbonate based. Both methods have in common that algae is used as photochemical desorber of CO2 from absorption liquid. The advantages of these methods is that they are easy to scale-up, would lead to higher CO2 removal efficiencies compared to current CO2 feeding systems for algae, and lower operational cost compared to both conventional CO2 removal using amines and conventional autotrophic algae cultivation. The impact of the new strategies for integrating power plants with algae are described in order to provide more information on their novel aspects and their potential for CO2 mitigation.

Measurement and mitigation of methane emissions from beef cattle in tropical grazing systems: a perspective from Australia and Brazil

The growing global demand for food of animal origin will be the incentive for countries such as Australia and Brazil to increase their beef production and international exports. This increased supply of beef is expected to occur primarily through on-farm productivity increases. The strategies for reducing resultant greenhouse gas (GHG) emissions should be evaluated in the context of the production system and should encompass a broader analysis, which would include the emissions of methane (CH4) and nitrous oxide (N2O) and carbon sequestration. This paper provides an insight into CH4 measurement techniques applicable to grazing environments and proposed mitigation strategies, with relevance to the production systems that are predominant in grazing systems of Australia and Brazil. Research and technology investment in both Australia and Brazil is aimed at developing measurement techniques and increasing the efficiency of cattle production by improving herd genetics, utilization of the seasonal feed-base and reducing the proportion of metabolizable energy lost as CH4. Concerted efforts in these areas can be expected to reduce the number of unproductive animals, reduce age at slaughter and inevitably reduce emission intensity (EI) from beef production systems. Improving efficiency of livestock production systems in tropical grazing systems for Australia and Brazil will be based on cultivated and existing native pastures and the use of additives and by-products from other agricultural sectors. This approach spares grain-based feed reserves typically used for human consumption, but potentially incurs a heavier EI than current intensive feeding systems. The determination of GHG emissions and the value of mitigation outcomes for entire beef production systems in the extensive grazing systems is complex and require a multidisciplinary approach. It is fortunate that governments in both Australia and Brazil are supporting ongoing research activities. Nevertheless, to achieve an outcome that feeds a growing population while reducing emissions on a global scale continues to be a monumental challenge for ruminant nutritionists.

Indicadores do ambiente ruminal e suas relações com a composição do leite e células somáticas em diferentes períodos da primeira fase da lactação em vacas de alta produção

No atual sistema internacional de pagamento do leite por qualidade, têm-se valorizado dois aspectos fundamentais: a contagem de células somáticas (CCS) e o conteúdo de sólidos totais. O primeiro fator depende da saúde da glândula mamária e o segundo, de maior importância econômica para os laticínios, está relacionado com o manejo alimentar e a raça dos animais. O ambiente ruminal pode modificar a composição do leite, em especial o teor de gordura. A fonte principal de proteína nos ruminantes depende da síntese de proteína no rúmen. Os atuais sistemas de alimentação, usados em vacas de alta produção, predispõem os animais à apresentação de síndromes metabólicas o que direta ou indiretamente afeta a produção de leite. Objetivou-se, com o presente trabalho, relacionar indicadores do ambiente ruminal (tempo de redução com azul de metileno e pH) e o pH da urina com a composição do leite (sólidos totais) e a CCS. Não foi encontrada associação estatística entre os parâmetros avaliados. Os valores médios dos sólidos não-gordurosos analisados no estudo foram inferiores ao limite estabelecido pela norma oficial do Brasil.

Quantitative aspects of ruminant predicting animal performance

AbstractRations for dairy cattle are currently balanced to meet needs for energy, protein, vitamins, and minerals. While individual vitamins and minerals are considered, energy and protein are generally treated in aggregate even though entities within those aggregates can affect milk yield and composition. Significant efforts have been undertaken to describe ruminal metabolism in detail, but descriptions of post-absorptive metabolism assume constant fractional conversions of energy and protein to milk. A quantitative understanding of nutrient metabolism by the post-absorptive tissues is required, and the splanchnic tissues are critical components of the post-absorptive system as they mediate absorption of nutrients and play a rôle in regulation of metabolite availability.Glucogenic precursor supply can significantly affect endocrine status as well as splanchnic release of glucose, acetate, lactate, ketones, and the non-essential amino acids. Although the relative affinities of the splanchnic tissues for the essential amino acids (AA) are low as compared with the udder, net clearance on a daily basis represents approximately 2/3 of the net supply to the animal due largely to recycling of AA back to the tissue bed. This could be significantly reduced by stimulating removal and use by the udder as splanchnic affinities are much lower than mammary affinities. Additionally, the essential AA composition of absorbed protein is significantly modified by these tissues due to differing affinities for each of the AA. The extent of that modification is not a fixed constant but rather a function of several factors including milk yield. The accuracy of our current feeding systems could be improved if such variable rates of substrate removal replaced current static estimates.