Crude Protein and Nitrate Concentrations of Fall Forage for Stocker Cattle: Wheat vs. Perennial Cool‐Season Grasses

Abstract

Winter wheat (Triticum aestivum L.) pastures are a primary source of cool‐season forage used by stocker cattle (Bos taurus L.) in the southern Great Plains. Replacing some wheat pasture with perennial cool‐season grasses (PCSGs) could reduce uncertainties of sufficient fall forage and annual tillage operations. Wheat forage is capable of producing stocker weight gains >1.4 kg d−1, but wheat can accumulate nitrate that poses a health risk to stockers. Levels of crude protein (CP) and nitrate in fall forage clipped 4 yr (2002–2005), from replicated pastures of winter wheat and two PCSG pastures established in 2001 (‘Jose’ tall wheatgrass [Thinopyrum ponticum (Podp.) Z.‐W. Liu & R.‐C. Wang], ‘Manska’ intermediate wheatgrass [Thinopyrum intermedium (Host) Barkworth & D.R. Dewey], and one PCSG pasture established in 2002 [‘Lincoln’ smooth bromegrass (Bromus inermis Leyss)], were compared. Forage levels of CP in PCSGs were >148 g kg−1 dry wt., but were 21 to 37% less than that of wheat (244 ± 3 g kg−1). Mean nitrate‐N levels of wheat were 400, 1400, 4600, and 840 mg kg−1 in 2002 through 2005, respectively. Among the PCSGs, nitrate‐N did not exceed 660 mg kg−1 The CP levels of PCSGs were often substantially less than that of wheat, but were sufficient for growth of stocker calves. Nitrate risks that sometimes occurred with wheat would make PCSGs a safer choice for pasture.

Perennial cereal rye performance and comparisons with winter annual cereal forages in the semiarid, subtropical southwestern United States

“…MacKown and Northup (2010) found that CP of perennial cool-season grasses was 21 to 37% that of small grain forage in the autumn when all species would have been vegetative. The P-CR CP in the present study was 40 to 50% less than CP of the annuals (Table 2), but all species had lower CP concentrations than those measured by MacKown and Northup (2010), likely due to harvest maturity differences (Coleman et al, 2010). Rao et al (2000) attributed lower N concentrations in annual cereals compared with perennial wheat to dilution by greater yield; Marsalis et al (2008) made the same observation among annual cereals within and across species.…”

“…Although ACE-1 P-CR did not perennate in these semiarid, subtropical environments, even with irrigation, opportunities may exist for breeding programs in these regions for that purpose. Varieties of perennial cereals for semiarid, subtropical environments must have tolerance to water deficit and poor soil conditions (Larkin et al, 2014;MacKown & Northup, 2010), as well as heat tolerance, because perennial cereals, at least wheat, apparently do not express summer dormancy (Larkin et al, 2014).…”

“…Annual crops are, globally, the most widely used for forage (Newell & Hayes, 2017). Winter annual cereal forages are a significant component of livestock operations in the southwestern United States for backgrounding stocker cattle (Bos taurus) in either grazeout or graze-grain systems (Coleman, Rao, Volesky, & Phillips, 2010;Lauriault & Kirksey, 2004;MacKown & Northup, 2010;Marsalis, Lauriault, & VanLeeuwen, 2008) and other regions (Beck et al, 2008;Entz et al, 2002) where they are used to supplement native rangeland (Entz et al, 2002). Currently, autumn through spring forage gaps are filled with winter wheat (Triticum aestivum L.; WW) (Beck et al, 2008;Coleman et al, 2010;Lauriault & Kirksey, 2004;Marsalis et al, 2008), cereal rye (Secale cereale L. × S. montanum Guss.)…”

“…ex A. Camus (Secale × Triticum)] (Griggs, 2006;Lauriault & Kirksey, 2004;Marsalis et al, 2008), barley (Hordeum vulgare L.) (Acharya, 2006;Griggs, 2006;Lauriault & Kirksey, 2004), and oat (Avena sativa L.) (Lauriault & Kirksey, 2004;Marsalis et al, 2008), all of which are annual species. Winter wheat is the primary species used in the southern Great Plains (MacKown & Northup, 2010;Rao, Coleman, & Volesky, 2000). Historically, almost two-thirds of the WW planted in eastern New Mexico of the US Southwest under dryland and irrigated conditions are not harvested for grain, even when grain prices are high (NM AgStats, 2015) because it is planted for winter forage and grazed out.…”

“…Continued use of annual crops has led to environmental degradation in many regions (Cox et al, 2002;Newell & Hayes, 2017;Reimann-Philipp, 1995). Declining water for irrigation, annual establishment costs, and the push to maintain living cover without tillage are prompting growers in those regions and globally to seek alternative forage crops, particularly perennials (Beck et al, 2008;Bell, Wade, & Ewing, 2010;Coleman et al, 2010;MacKown & Northup, 2010) for use as hay or pasture, particularly during the autumn through spring growing season. The irrigation requirement for growing winter cereals is less than that for growing summer annuals to be harvested as hay for winter feeding (Griggs, 2006), and grazing is the most economical forage harvesting method (Entz et al, 2002;Rao et al, 2000).…”