Characteristics of Manure Harvested from Beef Cattle Feedlots

Open lot cattle production systems present unique challenges for nutrient planning processes. Previous estimates of quantities and characteristics of harvested manure from this type of facility are based upon data from the early 1970s. In addition, harvested manure is impacted by weather, feeding program, season, and pen management decisions. The objectives of this study are to characterize under commercial conditions for open lot beef systems: 1) harvested manure quantities and characteristics; 2) impact of factors such as feeding program, season, and management on harvested manure; and 3) mass balance for nitrogen (N) and phosphorus (P). Data from six commercial feedlots (representing 6,366 head of cattle) suggest that 33% of excreted N (65 g/hd/d) and 91% of excreted P (32 g/hd/d) are harvested as manure on average and that current standard estimates published by ASAE (2005) and NRCS (1992a) overestimate harvested manure N and P. Additionally, significant variation was observed among feedlots. This variation is driven by ration nutrient concentration (P only), pen conditions prior to and during manure harvest (N and P), and management choices relative to use of manure in lot maintenance (N and P). The variation would suggest that nutrient planning estimates for open lots would need to be based upon farm specific data as opposed to typical or standard values. Finally, a pen-based mass nutrient balance for a beef cattle feedlot suggests that pen outputs as finished animal, harvested manure, and nutrient losses represent 31%, 23%, and 47%, respectively, of all pen N inputs and 38%, 57%, and 5%, respectively, of all pen P inputs. Inputs include nutrient content of all animals and feed entering a feedlot pen over a grow-out period

Syndecan-4 Is Essential for Development of Concentric Myocardial Hypertrophy via Stretch-Induced Activation of the Calcineurin-NFAT Pathway

Sustained pressure overload leads to compensatory myocardial hypertrophy and subsequent heart failure, a leading cause of morbidity and mortality. Further unraveling of the cellular processes involved is essential for development of new treatment strategies. We have investigated the hypothesis that the transmembrane Z-disc proteoglycan syndecan-4, a co-receptor for integrins, connecting extracellular matrix proteins to the cytoskeleton, is an important signal transducer in cardiomyocytes during development of concentric myocardial hypertrophy following pressure overload. Echocardiographic, histochemical and cardiomyocyte size measurements showed that syndecan-4−/− mice did not develop concentric myocardial hypertrophy as found in wild-type mice, but rather left ventricular dilatation and dysfunction following pressure overload. Protein and gene expression analyses revealed diminished activation of the central, pro-hypertrophic calcineurin-nuclear factor of activated T-cell (NFAT) signaling pathway. Cardiomyocytes from syndecan-4−/−-NFAT-luciferase reporter mice subjected to cyclic mechanical stretch, a hypertrophic stimulus, showed minimal activation of NFAT (1.6-fold) compared to 5.8-fold increase in NFAT-luciferase control cardiomyocytes. Accordingly, overexpression of syndecan-4 or introducing a cell-permeable membrane-targeted syndecan-4 polypeptide (gain of function) activated NFATc4 in vitro. Pull-down experiments demonstrated a direct intracellular syndecan-4-calcineurin interaction. This interaction and activation of NFAT were increased by dephosphorylation of serine 179 (pS179) in syndecan-4. During pressure overload, phosphorylation of syndecan-4 was decreased, and association between syndecan-4, calcineurin and its co-activator calmodulin increased. Moreover, calcineurin dephosphorylated pS179, indicating that calcineurin regulates its own binding and activation. Finally, patients with hypertrophic myocardium due to aortic stenosis had increased syndecan-4 levels with decreased pS179 which was associated with increased NFAT activation. In conclusion, our data show that syndecan-4 is essential for compensatory hypertrophy in the pressure overloaded heart. Specifically, syndecan-4 regulates stretch-induced activation of the calcineurin-NFAT pathway in cardiomyocytes. Thus, our data suggest that manipulation of syndecan-4 may provide an option for therapeutic modulation of calcineurin-NFAT signaling

Summary of Manure Amounts, Characteristics, and Nitrogen Mass Balance for Open Feedlot Pens in Summer Compared to Winter

Data from 18 experiments (244 pen means) over a 10-year period were summarized in order to make a long term comparison between seasons dealing with nutrient mass balance studies and characteristics and amount of manure from open feedlot pens. The amount of manure DM increased from 10.6 lb to 20.0 lb/head finished/day from summer (May to September) to winter (November to May). Quantities of OM, ash, and N (lb/head finished/day) increased from 2.5 lb OM, 8.1 lb ash, and 0.13 lb N to 4.8 lb OM, 15.2 lb ash, and 0.22 lb N/ head finished/day from summer to winter, respectively. Summer pens averaged 2.7% of N excretion in pen runoff N, and 6.2% of OM excretion in pen runoff, while winter pens averaged 1.8% of N excretion in pen runoff N, and 1.9% of OM excretion in pen runoff. Average N volatilization was higher for summer feeding pens (69%) compared to winter (47%). The implications, which can be used in individualized NMPs, are more total manure and manure N must be handled, but less volatilization of N and less N runoff occur in the winter compared to the summer feeding period

Managing Phosphorus in Beef Feeding Operations

A commercial feedlot study was conducted to determine manure nutrient flow in six feedlots representing 6,366 cattle. On average, cattle involved in this summary were yearlings (BW = 353 kg) and gained 183 kg over 123 d. It was calculated that 11.5% of the feed nitrogen and 16.9% of the feed phosphorus was retained by the animal with the remaining nutrients excreted. On average, 25.6 kg of N and 4.1 kg of P (DM basis) were excreted per fed beef animal. On average, 887 kg total manure (solids and water) were removed per finished animal (7.2 kg/animal/d) averaging 73% total solids. Approximately 28% of the total solids are volatile solids with a wide range of observed volatile solids levels (9 to 63%). Based upon these data, 30.7% of the excreted nitrogen or (7.8 kg/animal fed) and 90.2% of the excreted phosphorus (or 3.7 kg/animal fed) were removed in manure at cleaning. These data suggest there is variation in the amount of P harvested from beef feedlots, reflecting the variation between feedlots as a result of individual pen conditions, and requirements for use and handling of the manure in the pen prior to harvesting. These data suggest that estimates based on the references (ASAE, 2000; USDA, 1992) of P removed in manure are too high, and indicate that acres required for distribution of manure P in NMPs should be 50% of the acres predicted by those references

Managing Phosphorus in Beef Feedlot Operations

A commercial feedlot study determined manure nutrient flow in six feedlots using a corn and by-product based diet with an average P content of 0.39% (DM basis), and a range of 0.34 to 0.48%. Mass balances for N and P were conducted on each pen. The average feed nutrient intake was 0.52 lb N/head/day (64.0 + 7.6 lb/animal fed) and 0.09 lb P/head/day (10.9 + 2.2 lb/animal fed). Based upon averages from the 6,366 head of cattle, 11.5% of the feed nitrogen and 16.9% of the feed phosphorus were retained by the animal with the remaining nutrients excreted. The harvested manure averaged 73% dry matter and 28% organic matter. A wide range of observed organic matter levels (9 to 63%), reflected soil being hauled out of pens along with the manure solids. Based upon these data, 31% of the excreted nitrogen or (17.2 lb/animal fed) and 90% of the excreted phosphorus (or 8.1 lb/animal fed) were removed in manure at cleaning

Economics of Manure Phosphorus Distribution from Beef Feeding Operations

An economic model was developed to evaluate cost and value of manure distribution. Feedlots ranging in size from 2,500 head to 25,000 head one-time capacities were used as case studies to calculate excretion amounts from cattle fed diets with a range of phosphorus. Diet P and subsequent costs of distributing the manure were used to analyze the corresponding costs of manure distribution, in addition to determining the required available land needed to be in compliance with a nutrient management plan based on utilization of manure P by the crops grown. The model illustrated when animals are fed diets of increasing P concentration, total distribution cost increased, ranging from $2.10 -$6.70/hd finished/yr, as did application time (186-2810 hrs) and required spreadable hectares (130-2520 ha), but the agronomic and market value of manure produced increased at a rate faster than the rate of increasing costs of distribution for feedlots ranging in size from 2,500 to 25,000 head capacity, and land availability as low as 50%