Grass-Legume pastures to increase economic and environmental sustainability of livestock production

Grass-Legume pastures to increase economic and environmental sustainability of livestock production

Summary

The objective was to determine the production, environmental and economic potential of grass-legume pastures in comparison to fertilized grass monocultures. However, the legumes in the grass-legume pastures died, and new pastures were re-established in 2011. We did collect a second year’s data on livestock intake and gains, fatty acid (FA) profiles, ruminal pH and ammonia, and forage production, comparing tall fescue with and without N-fertilizer to feedlot treatments. The results indicated that applying N fertilizer to tall fescue did not influence growth performance or carcass characteristics. However, the grazing steers carcasses had increases in human beneficial FA compared with feedlot steers.

Objectives/Performance Targets

Three objectives and accompanying performance targets are listed below.

Objective 1. Compare livestock performance, economics and subsequent carcass characteristics from beef grazing grass monocultures and low- and high-tannin grass-legume mixtures versus traditional feedlot-based finishing.

Year 1: Begin grazing (plots established in 2009); measure feed intake, body weight, dry matter and nutrient digestibility (crude protein and fiber); and determine feed efficiency and plasma urea nitrogen during growing and finishing periods.

Year 2: Collect second year data on feed intake, body weight and dry matter and nutrient digestibility; determine feed efficiency and plasma urea nitrogen during growing and finishing period; and develop fact sheets for use at pasture walks and field days.

Year 3: Conduct continuous culture study using feed samples collected from growing and finishing periods to investigate ruminal fermentation characteristics (ammonia-N, VFA, methane, microbial protein synthesis and digestibility); evaluate meat quality of steers slaughtered after the finishing period in year 1 and 2 (FA analysis, tenderness, sensory panel evaluation and lipid and color stability measurements); and revise fact sheets for symposium.

Year 4: Complete data analysis and prepare journal manuscript(s).

Objective 2. Determine best possible grass-legume mixtures and plant densities that maximize pasture productivity and nutritional quality.

Year 1: Plot establishment (seed plots and measure frequency of establishment).

Year 2: Begin grazing and collect first year of plot yield, nutritional quality and stand frequency; develop NIRS equation that separates species composition; and develop fact sheets for use at pasture walks and field days.

Year 3: Collect second year of plot yield, nutritional quality and stand frequency; and begin data analysis.

Year 4: Complete data analysis, revise fact sheet(s) and prepare journal manuscript.

Objective 3. Determine the effects of tannins on nutrient cycling in grazing systems.

Year 1: Pasture establishment, and collect baseline soil and leachate data.

Year 2: Begin grazing and collect first year of soil, plant and leachate data; sample analyses; and develop fact sheets for use at pasture walks and field days.

Year 3: Second year of collection of soil, plant, and leachate data; sample analyses; and begin data analysis.

Year 4: Complete data analysis, revise fact sheet(s) and prepare journal manuscript.

Accomplishments/Milestones

The research was initiated in 2011. It was discovered that legumes had died out of previously established pastures. These tall fescue-legume (alfalfa and birdsfoot trefoil) pastures were re-established in 2011. However, the graduate student on this project used the existing pastures to collect a second year’s data on livestock intake and gains, fatty acid profiles, ruminal pH and ammonia, and forage production and quality comparing tall fescue with and without N-fertilizer to feedlot treatments.

Twenty-seven Angus crossbred steers were assigned to the following three treatments: grazing on TF without N fertilizer (TF–NF), grazing on tall fescue with N fertilizer (TF+NF), and feeding TMR on feedlot (FLT). The pasture-finished steers grazed on replicated 0.47-ha paddocks from May through September 2010 for total of 16 weeks. After the completion of 16-week treatment, ultrasound measurements were performed to assess carcass characteristics. Adipose tissue biopsies were obtained on week 4, 12 and 16 to compare fatty acid (FA) profiles between grazing and feedlot steers. Pasture forages and diet ingredient samples were obtained at 28 day intervals to determine nutritive value and fatty acid composition. The results showed that DM intake averaged 7.51 kg/d throughout grazing, and it did not differ between treatments (P > 0.26). In response to N fertilization, BW and ADG of grazing steers also did not differ (P > 0.16). With progression of grazing season, ADG and G:F gradually declined regardless of treatments. Ruminal pH averaged 7.27, and it was similar between treatments. Concentration of ruminal ammonia-N was increased due to N fertilization (P < 0.01), indicating that there was an imbalance between dietary N and energy on TF+NF during the grazing season. Sizes of rump and rib fat, rib eye area and intramuscular fat percentage did not differ between grazing treatments. The adipose tissue linoleic acid, linolenic acid and CLA contents of TF-NF, TF+NF, and FLT were averaged of 1.14, 0.41, and 0.44%, 1.09, 0.41, and 0.47%, and 1.29, 0.19, and 0.25%, respectively. Fertilizing N on TF did not affect adipose tissue FA composition. Concentrations of C18:0, C18:3 n-3 and CLA were higher in grazing steers compared with those in FLT (14.11 vs. 9.57, 0.41 vs. 0.19, and 0.45 vs. 0.25 g/100 g FA, respectively; P < 0.01), whereas concentrations of C18:1 cis-9 were higher in FLT than grazing treatments (P < 0.05). Overall results of this grazing study showed that applying N fertilizer to TF did not influence growth performance and carcass characteristics of grazing beef steers. The results from this study also indicate that 4 weeks of grazing resulted in remarkable changes in adipose tissue FA profiles in beef steers, but N fertilization had minor impacts on the FA composition. Grazing beef steers elicited increases in human beneficial FA concentrations compared with steers fed FLT.

The DaisyII incubator batch culture system (ANKOM Technology, Macedon, NY) was used to examine the effect of N fertilizer on TF on in vitro degradability of NDF and ADF. Pasture samples for this study was taken every 4 weeks on each paddock from grazing study. Ruminal fluid used for in vitro inoculum was collected at 0800 h from three ruminally cannulated beef cows fed ad libitum grass hay. In vitro degradability data were collected at 12, 24, 36 and 48 hours of incubation. Degradabilities of NDF and ADF were higher on TF+NF compared with TF-NF at week 16 (25.9 vs. 24.0% and 23.8 vs. 21.1%, respectively; P < 0.05). The results indicate that N fertilization on TF can improve the forage quality at the end of grazing season, which is very important due to decreasing forage availability in that period.

In addition to these livestock performance studies, lysimeters were installed during the re-establishment of the tall fescue-legume pastures, which were used to determine the initial nitrogen in the leachate. These pastures will be grazed next year. The small plots of binary mixtures of five grasses (orchardgrass, tall fescue, meadow brome, timothy and perennial ryegrass) and three legumes (alfalfa, birdsfoot trefoil and cicer milkvetch) were established, and data collection was begun. Ratios in the mixtures included 0, 25, 50 and 75% legume composition.

The expected accomplishments for next year include collecting the first year data on animal performance when grazing tall fescue-legume mixed pastures (replanted in FY2011), collecting the second year’s data from small plots that are evaluating different species and percentages, developing an NIRS equation that can determine percent legume composition in mixed species samples, and beginning nitrogen leachate studies.

Impacts and Contributions/Outcomes

Results were presented at the Annual Meeting of Western Section, American Society of Animal Science in June 2011 and at the Joint Annual Meeting of ADSA-ASAS in July 2011, and indicated that applying N fertilizer to tall fescue did not influence growth performance or carcass characteristics.

Two scheduled field days – one at the Utah State University Pasture Research Center and a second hosted by the University of Idaho Extension at Richard Ward’s (Farmer Collaborator) were cancelled and will be held next year.

The following manuscripts were prepared and published.

Noviandi, C.T, J.-S. Eun, D.R. ZoBell, R.D. Stott, B.L. Waldron, M.D. Peel. 2011. Growth performance and carcass characteristics of beef steers grazing tall fescue without and with nitrogen fertilizer. WSASAS Proceedings Vol. 62:337-340.

Noviandi, C. T., R. E. Ward, J.-S. Eun, D. R. ZoBell, R. D. Stott, T. Astuti, B. L. Waldron, and M. D. Peel. 2011. Fatty acid profiles in adipose tissue of grazing and feedlot beef steers. J. Anim. Sci. 89 (E-Suppl. 1): 617 (Abstr.).

Noviandi, C. T., R.E. Ward, D.R. Zobell, R. D. Stott, B.L. Waldron, M.D. Peel, and J.S. Eun. 201x. Fatty acid composition in adipose tissue of pasture and feedlot-finished beef steers. Professional Animal Scientist. (Accepted 21 Dec 2011)

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