Research Accomplishment Reports 2007

Animal Health and Grazing Systems

L.P. Bush, L. Harrison
Department of Plant and Soil Sciences

 

Project Description

Ten Angus steers with ruminal and abomasal infusion cannulae were assigned to treatments in a replicated 5 x 5 Latin Square design experiment. Animals were housed individually in pens in an environmentally controlled room (21C). Steers were fed cubed alfalfa hay (approximately 17% CP, 60% TDN) at 1.5 times their maintenance energy requirements 12 times daily. Carbohydrate infusion treatments were arranged as a 2x2 factorial structure plus a control. Factors included site (ruminal versus abomasal) and amount (to provide 10 or 20% of total ME intake) of starch hydrolysate (SH) infusion. Thus, the 5 treatments included: control (water), 10% ME intake ruminal SH, 20% ME intake ruminal SH, 10% ME intake abomasal SH and 20% ME intake abomasal SH. Given the initial body weights of the steers in the experiment, these infusion rates equated to approximately 400 and 800 g/d. The SH was used to precisely simulate the amounts of available carbohydrate supplied to the rumen, and potentially to the intestine, of cattle supplemented with typical amounts of corn. Starch hydrolysate was chosen over raw corn starch as a non-structural carbohydrate source because: 1) it has greater small intestinal digestibility, 2) its digestion characteristics are similar to native starch, 3) it provides a better suspension, and 4) it has little or no free glucose. Ruminal and abomasal infusions were accomplished with a peristaltic pump synchronized to deliver 250 mL/h, which approximates 10% of intestinal flow. Steers were continuously infused for 22 h/d to allow 2 h/d for replenishment of infusates, maintenance of equipment, and provision of exercise for animals. Infusion periods were 21 d in length, with the amount of SH infused increased incrementally over the initial 6 d to achieve 100% of the infusion level of SH by d 7. The total volume infused was equalized across treatments and site by infusion of water. On d 15 to 21 of each period, fecal and urine measurements were taken every 24 h. In order to determine the quantitative relationships between the amount and site of carbohydrate infusion and whole body urea-N kinetics, steers were infused with 15,15N-urea during d 2 through 4 of the N balance trial. Samples of urine and feces from the first 24 h of the balance trial were sub-sampled to establish background 15N enrichments. Starting on day 2, steers were fitted with jugular catheters for intravenous infusion of 15,15N-urea and collection of jugular blood samples (blood background sample taken prior to infusion). Urea was infused in sterile physiological saline at 85 mL/h to supply approximately 0.14 mmol of urea N/h using a peristaltic pump. Urine and fecal samples were collected every 2 h during h 49-61 of infusion to ensure equilibration of infused 15,15 N-urea. Urea-N isotopomers (14, 14N-, 14, 15 N- and 15, 15 N-) in the urine samples were quantified and fitted to a model to determine the urea-N entry rate (UER; total body production of urea), urinary urea-N excretion rate, gastrointestinal urea-N entry rate (GER; amount of urea entering gut), and fractions of GER contributing to anabolism, the ornithine cycle, and fecal N excretion.

Impact

Livestock grazing high quality forages excrete substantial amounts of N into the environment, where it is susceptible to leaching into groundwater or volatilization into the atmosphere. Urea kinetic data will be used in conjunction with data from other experiments to 1) provide inputs for refinement of current prediction models and development of novel models and to define the putative mechanisms limiting whole body nitrogen utilization in ruminants consuming high quality forages. In turn, this will provide opportunities to manipulate N utilization efficiency in order to minimize N excretion into the environment and maximize incorporation into animal products. Opportunities to alter the excretion of nitrogen by grazing animals are largely limited by our understanding of the factors that affect the efficiency of N use by the animals.

This study demonstrated that, through nutritional manipulation, even in situations in which we don't alter the total N excretion we can divert N excretion from the urine to the feces. This has importance from an environmental standpoint because the forms of N in the urine are subject to more rapid leaching and volatilization that N excreted in the feces. Metabolic studies with lambs indicated that they will adapt to toxic tall fescue and that short-term bioassays may result in equivocal data. Our understanding of the factors affecting the efficiency of N use by ruminant animals is limited. The isotope dilution procedures used in the present experiment have only recently been applied to ruminant animals, and offer greater insight into the quantitative fluxes of N in ruminant animals. Results from this study will be used to enhance current metabolic models, thus increasing our ability to predict responses in N dynamics to changes in dietary inputs.

Molecular phylogenetics of red clover indicates a Mediterranean origin of Trifolium and a single origin for all North and South American species. Importantly the ancestral state of Trifolium is annual and perennial habit is associated with polyploidy. Information obtained will allow DNA barcoding of nrDNA and cpDNA to identify the 255 species within the genus. Sufficient information is lacking in most of the world's genera to do such. Shortened internodes in red clover is a recessive trait with normal-sized leaflets. The trait is a single recessive gene. Multiple-leaflet red clover has 0 to 10 multiple leaflets leaves depending upon the size and number of leaves per plant. Main impact probably will be on ornamental plantings. Normalized difference vegetative index (NDVI) has been proven to be an excellent management tool. Data on biomass may be determined availability is readily obtained from ground instrumentation and has potential to be obtained from high aerial instrumentation.

Publications

Han, K. J., M. Collins, E. S. Vanzant, and C. T. Dougherty. 2006. Characteristics of baled silage made from first and second harvests of wilted and severely wilted forages. Grass and Forage Sci. 61:22-31.

Flynn, E.S., Dougherty, C. T., and Koostra, B. K. 2006. GPS-enabled rising plate meter with data logging capability. Online. Forage and Grazinglands doi:10.1094/FG-2006-0825-01-BR.

Hancock, D.W., and C.T. Dougherty. 2006. Response of alfalfa to potassium nutrition and subsurface irrigation during a drought year. pp. 167-171. In: Proceedings of the 2006 Conference of the American Forage and Grassland Council, March10-14, 2006, in San Antonio, Texas.

Hancock, D.W., and C.T. Dougherty. 2006. Measuring variation in alfalfa yield and stand using conventional remote sensing techniques. pp. 240-244. In: Proceedings of the 2006 Conference of the American Forage and Grassland Council, March10-14, 2006, in San Antonio, Texas.

Taylor, N.L. and G.L. Olson. 2004. Registration of short internode red clover genetic stock. Crop Science 44:1504.

Taylor, N.L. and G.L. Olson. 2005. Registration of Lucky multiple-leaflet red clover. Crop Science 45:2657.

Ellison, N.W., A. Liston, J.J. Steiner, W.M. Williams and N.L. Taylor. 2006. Molecular phylogenetics of the clover genus (Trifolium-Leguminosae). Molecular Phylogenetics and Evolution 39:688-705.

Zinner, R.A., D.g. Ely, D.K. Aaron, L.P. Bush, A.K. Lunsford, M.L. Mallory. 2006. Adaptation of lambs toan endophyte-infected fescue seed diet. J. Anim. Sci. 84:Suppl. 2. p5

Flynn, E.S., C.T. Dougherty, G.J. Schwab, G.E. Aiken, and E. Vanzant. 2005. Determining biomass with NDVI in Grasslands. ASA-CSSA-SSSA International Annual Meetings. Salt Lake City, UT. November 6-10, 2005.

Flynn, E.S., C.T. Dougherty, and O. Wendroth. 2006. Using NDVI as a pasture management tool. 8th International Conference on Precision Agriculture. Sioux Falls, SD.

Flynn, E.S., C.T. Dougherty, and O. Wendroth. 2006. Using NDVI as a pasture management tool. ASA-CSSA-SSSA International Annual Meetings. Indianapolis, IN. November 5-9, 2006

Hancock, D.W., and C.T. Dougherty 2006. Measuring variation in alfalfa yield and stand using conventional remote sensing techniques. pp. 59. In: Proceedings of the 2006 Conference of the American Forage and Grassland Council, March 10-14, 2006, in San Antonio, Texas.

Hancock, D.W., and C.T. Dougherty. 2006. Response of alfalfa to potassium nutrition and subsurface irrigation during a drought year. pp. 35. In: Proceedings of the 2006 Conference of the American Forage and Grassland Council, March 10-14, 2006, in San Antonio, Texas.