Recipient Organization
UNIVERSITY OF FLORIDA
G022 MCCARTY HALL
GAINESVILLE,FL 32611
Performing Department
NFREC
Non Technical Summary
As we move toward the next couple of decades, the world's agriculture will face one of the greatest challenges of all time: to produce enough food to feed the 9 billion people the earth will hold by 2050. Without question, this will demand the concerted efforts of producers, researchers, and policymakers to provide the experience, technology, and legal framework necessary to accomplish such a difficult endeavor. Among the different sources of animal protein, beef is the most nutrient dense on a per calorie basis, supplying several of the essential vitamins and minerals with a relatively low caloric intake per serving.Ruminants such as cattle, sheep, and goats have a unique advantage over non-ruminants in terms of nutritional physiology, because they carry microorganisms in their gastrointestinal tract (GIT) that hold the key to the digestion of fiber. Fiber is present in forages in the form of cellulose and is the most abundant complex carbohydrate on earth. By harboring microorganisms in their GIT, ruminants can take advantage of fiber digestion by creating a symbiotic relationship between the microbes and the ruminant host. The microbes digest the fiber and produce by-products known as volatile fatty acids, which are in turn used by the ruminant animal as an energy source. In return, the ruminant host provides a good environment for the microorganisms and plenty of feed to sustain their growth. For this reason, cattle, sheep, and goats can thrive in environments where no other type of production system can take place.Non-ruminants, such as poultry and swine, do not have the ability to digest fiber and rely on the use of grain and protein supplements to achieve high production levels, competing directly with humans for the type of feed used (i.e., plant proteins and cereal grains). Thus, ruminants grazing in areas where no crops can be grown and no other livestock species can survive represent an excellent opportunity to maximize land use, and provide nutrient recycling in the form of manure.Around the world, the initial phases of the beef production cycle (cow/calf and stocking segments) are almost entirely reliant on the use of forages or fibrous by-products, and this often takes place on land where no other production system can thrive. In particular, the cow/calf segment in Florida takes place mostly under native vegetation and range conditions, which provide wildlife habitat for endangered and non-endangered species. This contribution of beef cattle systems in the form of ecosystem services is often overlooked. Additionally, beef and dairy cattle are particularly efficient at recycling by-products of agriculture industries that are not suitable for consumption by other livestock species. Examples include the use of citrus by-products, distillers grains (by-product from ethanol), and corn gluten feed (residue from wet milling of corn to produce high fructose corn syrup).Unfortunately, this advantage by ruminants in terms of their ability to digest fiber comes at a cost. The production of greenhouse gases such as carbon dioxide and methane is a result of the enteric fermentation of feedstuffs, and those greenhouse gases are released by cattle as a necessary byproduct of their fermentation of fibrous feeds. The "greenhouse effect" of certain gases refers to their ability to "trap" the heat that is generated when the sun radiation bounces back after hitting the earth's surface. That radiation cannot escape, and thus increases the atmospheric temperature, affecting biological processes in diverse manners. Those gases with such capacity to retain heat are called Greenhouse Gases (GHG), and the three most common gases are carbon dioxide, methane, and nitrous oxide.The ability to produce methane, the main contributor of the GHG emitted by cattle, is much greater in animals consuming forage than those consuming a high-grain diet. Thus, segments of beef production chain that involve the use of forages as the main resource are greater contributors in terms of GHG emissions. In the southeastern United States, where approximately 1/3 of U.S. cowherd resides, forages are the main feed resource used in cow/calf and stocker production systems. Despite the significance of the SE United States in terms of beef cattle numbers, very little research efforts have been devoted to mitigate methane emissions in forage-based systems.The use of diets with high concentrations of sulfate or nitrate can be alternatives to decrease methane emissions as it has been evidenced in some previous studies, some of those conducted in our laboratory. Both nitrate and sulfate are chemical entities that can outcompete the process that leads to the formation of methane, in a chemical phenomenon called reduction. However, excess sulfur in the diets can lead to poor absorption of some of the minerals that are essential to maintain cattle health and reproductive ability. If cattle were able to receive a diet high in sulfates, and at the same time mitigate the effects that high-sulfur has on mineral availability, the use of high sulfur diets could be an alternative to mitigate methane emissions. Fortunately, some forages grown in the southeastern U.S. can be quite high in sulfur, naturally providing an alternative to decrease methane emissions. Our laboratory has investigated the effects of bismuth subsalicylate as a feed additive to bind excess dietary sulfur and mitigate the negative effects on cattle, obtaining some promising in vitro results. In addition, the same in vitro results were used to test the potential of nitrates to mitigate enteric methane emissions, while providing a source of protein to the animal. This is possible because nitrate can be used by the ruminal microorganisms to synthesize protein that in turn is used by the ruminant to meet their growth and maintenance needs. However, the effects of nitrates and bismuth subsalicylate combined has never been studied in vivo in beef cattle.Thus, the specific objectives of this study are:To determine the effects of BSS in combination with nitrate on in vivo ruminal fermentation, metabolism, microbial ecosystem, and enteric CH4 production when feeding a low-quality forage diet. We hypothesize that feeding BSS and nitrates may reduce enteric H2S and CH4 production without negatively affecting ruminal fermentation and metabolism.Assess the effect of BSS in combination with nitrate on performance of growing cattle consuming a low-quality, high-S, forage-based diet. We hypothesize that cattle consuming low-quality, high-S diets supplemented with BSS and nitrates will present greater performance and improved mineral status than those without BSS and nitrates.Assess the effect of BSS in combination with nitrate on performance of feedlot cattle consuming a high-grain diet with inclusion of high-sulfur byproducts. We hypothesize that feedlot cattle consuming a high-grain diet supplemented with BSS and nitrates will present greater performance than those without BSS and nitrates.The expected results from this study are that nitrate and bismuth subsalicylate may provide an alternative to decrease greenhouse gas emissions by cattle consuming high-forage diets. Additionally, the inclusion of nitrates as a supplement would improve the nutritional status of cattle by increasing the protein supply, resulting in increased growth performance.The anticipated impact of this project is evidenced by the potential of decreasing the negative effects of high sulfur diets, which has been estimated to cost the U.S. beef industry an annual $7.4 million, considering only the effects on high-grain diets. Because methane is both an environmental pollutant and an energy loss to cattle, mitigating methane emissions should enhance the production efficiency of ruminants, leading to improvements in the efficiency of conversion of grass or fibrous byproducts into animal protein.
Animal Health Component
40%
Research Effort Categories
Basic
60%
Applied
40%
Developmental
(N/A)
Goals / Objectives
High S concentrations in various byproducts fed to cattle can limit cattle production and adversely affect their health. In addition, low-protein warm-season forages like those found in the southeast U.S. can limit the productivity of beef/forage systems by decreasing ruminal digestibility and overall animal performance. Because nearly 70% of the energy requirements for cattle are used prior to weaning, when the main dietary component is forage strategies need to concentrate on the improvement of production efficiency in high-forage systems. Enteric methane production by ruminants is an important net energy loss and also an environmental pollutant. Modifying the ruminal microbial ecosystem to reduce enteric H2S and CH4 production without negatively impacting animal productivity, could allow for feeding of diets with increased S, while reducing the carbon footprint of beef production. Increasing beef production efficiency and providing low-cost, high-nutrition rations for cattle, while decreasing the environmental impact, will be an important factor for a global plan to provide rich protein sources for an ever-growing population. This is particularly important because the human population is increasing at a greater rate than our current food supply. Furthermore, increasing temperatures due to elevated greenhouse gas (GHG) production could further limit food supply in the future. Therefore, it is critical to increase our knowledge about ruminal fermentation and the potential of manipulating the ruminal environment to develop strategies to increase production efficiency while decreasing the carbon footprint of beef production.In the rumen, anaerobic fermentation of feed occurs as different microorganisms use components of feed (e.g. hemicellulose, cellulose, starch, etc.) to yield a variety of products, such as volatile fatty acids (VFA), methane (CH4), carbon dioxide (CO2) and hydrogen sulfide (H2S). By decreasing CH4 production in ruminants, without changing gross energy (GE) intake or diet digestibility, metabolizable energy (ME) could be increased, providing more potential for milk or meat production. Nitrates can decrease CH4 production when provided to cattle; additionally, nitrates can be reduced to NH3 by ruminal microorganisms to provide a source of non-protein nitrogen (NPN). Currently, urea is a popular and efficient source of NPN; however, as other options of NPN sources arise, such as nitrates, competition in the market may occur, lowering prices and providing opportunities for producers.Many available byproducts for cattle feeding in the U.S. (distillers grains [DGS], corn gluten feed, molasses, etc.) contain high concentrations of S, which can be a limiting factor related to its effects on feed intake, trace mineral absorption, and increased incidence of polioencephalomalacia (PEM), and subsequent animal performance, related to elevated H2S production in the rumen. In non-ruminants, H2S has been reported to cause ulcerative colitis. To combat this, bismuth compounds (bismuth subsalicylate; BSS) have been used to reduce H2S production in humans and rodents. What is yet to be elucidated is if BSS can be provided to ruminants to reduce H2S production along with the CH4 mitigating effects of nitrates while consuming low-quality forages. This knowledge gap is critical, considering that more than two-thirds of energy requirements of the beef herd are used prior to weaning, when forage is the primary feedstuff.Understanding how the ruminal microbial ecosystem and fermentation are affected by various feed products and compounds may assist us in identifying protocols and strategies for providing high-quality animal protein at a lower environmental cost. The overall objective of this study, which is the next step toward the attainment of our long-term goal, is to explore efforts to mitigate S toxicity and CH4 production. We hypothesize that providing BSS and nitrates will increase efficiency of cattle by allowing a diet with increased S levels to be fed and granting a reduction in enteric CH4 production while reducing the need for urea as NPN.Specific Objectives:Objective #1: Determine the effects of BSS in combination with nitrate on in vivo ruminal fermentation, metabolism, microbial ecosystem, and enteric CH4 production when feeding a low-quality forage diet. We hypothesize that feeding BSS and nitrates may reduce enteric H2S and CH4 production without negatively affecting ruminal fermentation and metabolism.Objective #2: Assess the effect of BSS in combination with nitrate on performance of growing cattle consuming a low-quality, high-S, forage-based diet. We hypothesize that cattle consuming low-quality, high-S diets supplemented with BSS and nitrates will present greater performance and improved mineral status than those without BSS and nitrates.Objective #3: Assess the effect of BSS in combination with nitrate on performance of feedlot cattle consuming a high-grain diet with inclusion of high-sulfur byproducts. We hypothesize that feedlot cattle consuming a high-grain diet supplemented with BSS and nitrates will present greater performance than those without BSS and nitrates.
Project Methods
Exp. 1:Ten ruminally cannulated Angus crossbred steers, from the NFREC herd in Marianna, FL, will be used in a duplicated 5 × 5 Latin square design with 5 periods and a 2 × 2 + 1 factorial arrangement of treatments. Factors will include two doses of BSS (0.0 and 0.33%) and two doses of nitrate (0.0 and 1.2%). Dietary treatments within the factorial arrangement will be formulated to contain the same amount of RDP, based on the NPN provided by 1.2% nitrate inclusion in the diet DM, but using urea instead, while the negative control will have no NPN added. Each of the five periods will be 22 days in length and from day 0 to 13, steers on the nitrate treatment will be adapted to the nitrates as described by Newbold et al. (2014).Steers will be housed in the NFREC Feed Efficiency Facility (FEF) and will have access to water and bahiagrass hay ad libitum and 2.27 kg of a molasses with added S (CaSO4) to meet a dietary S concentration of 0.35%. The liquid supplement molasses will also be used as a carrier for the treatments (BSS and nitrates). Intake of hay will be recorded using the GrowSafe (GrowSafe Systems Ltd., Airdrie, Alberta, Canada) individual feed intake system, while liquid supplementation molasses will be weighed and provided separately.Ruminal gas cap H2S concentration will be measured on day 0, prior to feeding the liquid supplement (0 hour) and every 3 hours post-feeding for 12 hours. A subsequent collection will occur, prior to feeding, on day 1, 2, 3, and 14. To collect gas from the gas cap, a septum will be fitted into the plug of the cannula so that a 1 in, 16 gauge needle can be inserted into the ruminal gas cap without contaminating it with air.Microbial crude protein synthesis: To determine the effects of NPN supplementation and urea vs. nitrate as NPN source on microbial crude protein synthesis, the omasal sampling technique will be conducted, as described by Ahvenjärvi et al. (2003), and Harvatine and Allen (2006). Omasal samples will be collected four times daily, from d 16 to 18 of each period. A total of 12 samples per animal/period will be collected, representing the 24 h-period at sampling intervals of 2 h each. Omasal spot samples will be analyzed for chromic oxide (external marker), indigestible NDF (iNDF, internal marker), and nutrient fractions. Purine concentrations in the omasal and ruminal digesta will be used as microbial protein marker.Laboratory analysis: Concentrations of NH3-N in the incubation fluid will be determined following the phenol-hypochlorite technique (Broderick and Kang, 1980).Volatile fatty acids of the samples will be determined using a gas chromatograph equipped with a flame ionization detector and a capillary column (CP-WAX 58 FFAP 25 m 0.53 mm, Varian CP7767). To extract genomic DNA of ruminal bacteria from ruminal contents, the PowerSoil DNA Isolation Kit (MoBio Laboratories, Carlsbad, CA) will be used. The analysis of 454 pyrosequencing will be carried out on 454 FLX Titanium (454 Life Sciences - a Roche Company, Branford, CT, USA). Procedures for pyrotag handling and data analysis will be as described by Hong et al. (2011). Plasma will be analyzed for blood urea N (BUN) using a quantitative colorimetric kit. To determine H2S production, a 5-mL sample from the ruminal gas cap will be analyzed colorimetrically as described by Smith et al. (2010). Total N and S will be determined using a Vario Micro-Cube Elemental Analyzer (Vario, Elementar Americas Inc., Mt. Laurel, NJ). For NDF analysis, an Ankom200 Fiber Analyzer will be used, adding heat-stable α-amylase and sodium sulfite. Subsequent ADF analysis will be performed (Van Soest et al., 1991).Concentration of iNDF in hay and fecal samples will be determined as proposed by Cole et al. (2011) with modifications by Krizsan and Huhtanen (2013). Total purines will be analyzed according to the method of Zinn and Owens (1986). Chromium concentration in digesta samples will be analyzed by atomic absorption spectrophotometry as described by Henry et al. (2015).Exp. 2:Animals, diets and treatments: Twenty-five Angus crossbred heifers, from the NFREC herd in Marianna, FL, will be used in a randomized complete block design with a 2 × 2 + 1 factorial arrangement of treatments and two experimental periods (n = 10/treatment). Factors will be the same as in Exp. 1.Methane and Hydrogen sulfide emissions: In vivo CH4 and H2S emissions will be measured using the SF6 tracer technique (Johnson et al., 1994). Continuous collection of breath samples for analysis of CH4, H2S, and SF6 will be taken for five continuous days (day 15 to day 19).Apparent total tract digestibility of nutrients: Feed (hay and liquid) and fecal samples will be collected daily for four consecutive days. Fecal samples will be taken twice daily at 0800 h and 1600 h via rectal grab. Feed and fecal samples will be composited within heifer for further analysis of nutrient content and digestibility marker concentration. Indigestible NDF will be used as an internal indigestible marker.Laboratory analysis: Crude protein of hay and fecal samples will be determined by rapid combustion using a Micro-Cube Elemental N Analyzer (Vario, Elementar Americas Inc.). Concentration of iNDF and NDF will be determined in hay and fecal samples as described in Exp. 1. A gas chromatograph will be used with a flame ionization detector for CH4, an electron capture detector for SF6 and H2S, and a capillary column (Plot Fused Silica 25 m × 0.32 mm, Coating Molsieve 5A, Varian CP7536).Exp. 3: Methane emissions by hay-fed cattle supplemented with nitrates and bismuth subsalicylate Experimental design, animals, diet and treatments: To determine performance of growing cattle consuming a low-quality, high-S, forage-based diet, a randomized complete block design with a 2 × 2 + 1 factorial arrangement of treatments will be used. Factors will be inclusion of BSS and nitrate at the same doses as for Exp. 1 and 2. This experiment will be conducted over two consecutive years using 20 pastures (1.32 ha pasture-1) of 5 growing steers each.Performance data collection: Cattle will be weighed at the beginning of the experimental period (days -1 and 0), to determine initial BW, and again every 14 d until the end of the experimental period (d 69 and 70), to determine ADG and final BW. On days 0 and 70, ultrasonography will be performed to determine LM area and fat thickness.Liver and plasma mineral concentration: Blood will be collected from a sub-sample of the cattle (1 animal per pen will be randomly selected). Liver biopsies will be conducted from the same sub-sample as described by Engle and Spears (2000). Liver and plasma Cu, Zn, and Mn concentrations will be analyzed according to the methods of Pogge et al. (2014).Exp. 4: Effect of BSS and nitrate on performance of feedlot cattle fed a high-grain based diet with inclusion of high-sulfur byproducts.Experimental design, animals, diet and treatments: Ninety six Angus crossbred steers (320 kg of initial BW, approx.) will be used each year over two consecutive years (yr 3 and 4 of this project) in a randomized block design with a 2 × 2 factorial arrangement of treatments. Factors will be inclusion or not of BSS and nitrate at the same inclusion rates used in all previous objectives. Each year, steers will be blocked by weight and randomly assigned to 1 of 16 pens (6 steers/pen) for a total of 4 pen replicates per treatment per yr. Diets will be comprised of (DM basis): 54% dry-rolled corn, 30% DDGS, 10% bermudagrass hay, 1% limestone, and 5% of molasses-based supplement that will be used to deliver the treatments (BSS or nitrate).After a 14-d adaptation steers will be weighed every 28 d. Growth performance parameters such as ADG, feed efficiency and feed intake will be reported. On d 0 and 140, carcass ultrasound will be performed to assess Longissimus muscle area and fat thickness at the 12th rib.