Grass Forage Sci. 2020;75:153-158. wileyonlinelibrary.com/journal/gfs | 153

Basic management practices, including ideal seeding rates, are still lacking for black oat (Avena strigosa Schreb.) in the southeastern United States. This study evaluated the performance of five seeding rates (15, 30, 60, 120, and 240 lb acre −1 ) on 'Legend 567' oat (Avena sativa L.) and 'UF-10' black oat at three harvest dates (early, mid-season, and late) per year. Seeding rates of 60, 120, and 240 lb acre −1 tended (P = .07) to increase total herbage accumulation [4,760 lb dry matter (DM) acre −1 ] compared with 15 lb acre −1 (3,945 lb DM acre −1 ). Tiller density was usually greater for black oat than for oat. Seeding rate was positively associated with tiller density and explained 84 to 98% and 96 to 98% of the variation for black oat and oat, respectively. Tiller mass was greater for oat (0.045 oz tiller −1 ) than black oat (0.034 oz tiller −1 ), and greater for the mid-season harvest (0.043 oz tiller −1 ), compared with the early and late harvests (0.037 oz tiller −1 on average). There was a negative effect (P < .001) of seeding rate on tiller mass. Increasing the seeding rate had a negative effect on leaf length at the early and middle harvests (P < .05), and decreased leaf width from 0.56 to 0.39 inches in oat, and from 0.32 to 0.29 inches in black oat when changing from 15 to 240 lb acre −1 . To maximize herbage accumulation at a lower seeding rate, we recommend 60 lb acre −1 for both oat and black oat for multiple harvests.

Stable isotopes are useful for estimating livestock diet selection. The objective was to compare δ13C and δ15N to estimate diet proportion of C3–C4 forages when steers (Bos spp.) were fed quantities of rhizoma peanut (Arachisglabrata; RP; C3) and bahiagrass (Paspalumnotatum; C4).Treatments were proportions of RP with bahiagrass hay: 100% bahiagrass (0%RP); 25% RP + 75% bahiagrass (25%RP); 50% RP + 50% bahiagrass (50%RP); 75% RP + 25% bahiagrass (75%RP); and 100% RP (100% RP). Feces, plasma, red blood cell (RBC), and hair were collected at 8-days intervals, for 32 days. Two-pool mixing model was utilized to back-calculate the proportion of RP based on the sample and forage δ13C or δ15N. Feces showed changes using δ13C by 8 days, and adj. R2 between predicted and observed RP proportion was 0.81 by 8 days. Plasma, hair, and RBC required beyond 32-days to reach equilibrium, therefore were not useful predictors of diet composition during the study. Diets were best represented using fecal δ13C at both 8-days and 32-days. By 32-days, fecal δ15N showed promise (R2 = 0.71) for predicting diet composition in C3–C4 diets. Further studies are warranted to further corroborate fecal δ15N as a predictor of diet composition in cattle.

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Limpograss [Hemarthria altissima (Poir.) Stapf and C. E. Hubb.] has been gaining ground in beef cattle production as a stockpiling option. This study evaluated canopy characteristics of stockpiled pastures of limpograss cultivar Floralta over two cool seasons. Treatments included canopy layers (upper third, middle, lower third) and plant fractions (leaf and stem) arranged in a randomized split block design. There were 12 paddocks (blocks) with 1.2 ha each. Response variables included forage mass, canopy height and density, proportion of leaf and stem, and leaf and stem nutritive value within each layer. Forage mass fluctuated throughout the season, varying from 4,410 kg dry matter (DM) ha -1 in December to 7,220 kg DM ha -1 in October.Canopy bulk density was greater in February compared with November and December (290 vs. 145 kg ha -1 cm -1 ), and similar to October and January (200 kg ha -1 cm -1 , on average). The lower canopy layer had the greatest proportion of stem whereas the upper layer had greatest proportion of leaves. Leaf had greater in vitro digestible organic matter (IVDOM) (700 g kg -1 ) compared with stem (600 g kg -1 ). Leaf/stem ratio was greater in the upper layer (1.12), but similar between the middle and lower layers (0.4, on average). Leaf crude protein (CP) was greater than stem CP 70 vs. 20 g kg -1 ), with no differences between stem CP across evaluation dates. Stockpiled limpograss maintained leaf and stem digestibility and can be used as an alternative to reduce feeding costs in North Florida during the cool season. INTRODUCTIONSeasonality in forage production is a major challenge to develop pasture-based cattle production systems around the world. In central and southern Florida, limitation in forage