Forage Production and Nutritive Value of Oat in Autumn ... - CiteSeerX

Published online October 2, 2006

Forage Production and Nutritive Value of Oat in Autumn and Early Summer Francisco E. Contreras-Govea and Kenneth A. Albrecht* position of oat also is affected by temperature. A change from warm to cold increases stem proportion but delays oat maturity, and a change from cold to warm promotes earlier anthesis (Smith, 1974). Higher forage digestibility and WSC concentration are associated with cool temperature (Smith, 1975). Recent research has shown that oat crowns accumulate greater amounts of fructans when exposed to low temperature, and this response was different between oat cultivars (Livingston and Premakumar, 2002). This information indicates that in addition of affecting maturity, fiber, WSC, and CP concentrations of oat are influenced by temperature. To our knowledge, no studies have made direct comparisons of yield and nutritive value of oat forage harvested in early summer vs. early autumn. Therefore, this research was conducted to determine whether there are differences in forage yield and nutritive value of oat harvested in early summer vs. autumn, and to determine whether response to season differs among oat cultivars.

Reproduced from Crop Science. Published by Crop Science Society of America. All copyrights reserved.

ABSTRACT Oat (Avena sativa L.) grown for forage in the northern USA usually is sown in spring and harvested in early summer, with rapid decline in quality after boot stage. This study was conducted to determine if there are differences in forage yield and forage quality between summer sown–autumn harvested and spring sown–early summer harvested oat, and to determine whether seasonal effect is similar among oat cultivars that vary in maturity classification. Oat was sown in summer 2001 and spring 2002 at two locations in Wisconsin and harvested in autumn and early summer, respectively. Oat sown in August produced 6.7 Mg ha21 of forage when harvested 77 d later, about 1.0 Mg ha21 less than that obtained from spring sown oat harvested 77 d after sowing. Autumn forage yield was similar among oat cultivars due to decreasing daylength and temperature. Maturation of summer-sown oat was delayed, resulting in 10 to 15% less neutral detergent fiber (NDF), 18% greater digestibility, and 250% greater water soluble carbohydrate (WSC) concentration than spring-sown oat. High WSC levels are of particular importance since oat forage harvested in autumn will likely be stored as silage due to poor drying conditions in autumn. Differences in forage quality among cultivars and between spring and autumn oat forage are associated with maturity differences. Oat sown in late summer, and especially the leafy, late maturing cultivar ForagePlus, can supplement high quality forage production in autumn.

I

MATERIALS AND METHODS A field experiment was conducted at University of Wisconsin Agricultural Research Stations near Arlington (438189 N, 898219 W) on Plano silt loam soil (fine-silty, mixed, mesic, Typic Arguidoll) with pH 5.7 and 3.4% organic matter, and near Lancaster (428509 N, 908479 W) on Rozetta silt loam soil (fine-silty, mixed, mesic, Typic Hapludalf) with pH 6.3 and 2.6% organic matter. Soil P and K were maintained at a “high” level, based on soil test recommendations for oat at those locations (Kelling et al., 1991). Arlington soil was fertilized with 70 kg ha21 N but no N fertilizer was applied at Lancaster because alfalfa was previously cultivated there. Jim, Gem, and ForagePlus oat cultivars were sown at 100 kg ha21 7 Aug. (Arlington) and 9 Aug. (Lancaster) 2001, and 14 Apr. (Arlington) and 15 Apr. (Lancaster) 2002. Maturity classification for Jim is early, for Gem is intermediate, and for ForagePlus is late. Oat was sown in 3.0 by 6.0 m plots with 0.17-m row spacing. A split-block design with oat varieties and season (autumn or summer harvest) arranged in strips with four replicates was used. Maturity at harvest was determined using Zadoks’ scale (Zadoks et al., 1974). The late October harvest was taken just before a killing frost, 77 d after sowing. The early summer harvest was also made 77 d after sowing. Harvests were taken in early morning to minimize the impact of diurnal fluctuations in nonstructural carbohydrates (Owens et al., 1999). A 400-g subsample was oven-dried at 608C for dry matter determination and ground to pass a 1.0-mm screen with a laboratory mill. An additional 300-g sample was placed in an ice-filled cooler and transported to the laboratory for separation into stem (stem 1 sheath) and leaf components. Plant parts were lyophilized, ground, and stored at 2208C. Whole plant, stem, and leaf were analyzed for N by a rapid combustion method (LECO Model FP-528; LECO Corp., St.

N THE NORTH-CENTRAL

USA oat for forage is sown in spring, usually as a companion crop for alfalfa (Medicago sativa L.) establishment, and harvested in early summer at boot stage maturity for silage. Although forage yield nearly doubles from the boot to hard dough stage (Cherney and Marten, 1982a), NDF rapidly increases to greater than 500 g kg21 and digestibility declines to less than 600 g kg21 (Cherney and Marten, 1982b). In Wisconsin, summer-sown oat harvested in autumn produced 3.5 Mg ha21 with a relatively low NDF concentration (Maloney et al., 1999). Autumn oat forage production has received little attention in the north, but is an intriguing management opportunity. Previous results suggest that forage quality could be improved by growing small grains under cooler conditions (Maloney et al., 1999). They reported NDF and acid detergent fiber (ADF) concentrations of 441 and 239 g kg21 respectively in oat harvested in autumn 70 d after sowing. In 11 temperate grasses, high temperature was related to lower in vitro dry matter digestibility and greater crude protein (CP) and acid detergent lignin (Ford et al., 1979). Like other grasses, development and comDep. of Agronomy, Univ. of Wisconsin-Madison, 1575 Linden Dr., Madison, WI 53706. Funding has been partially provided for this research and publication from the USDA Cooperative State Research, Education and Extension Service (CSREES) Hatch Project WIS04802. Received 7 Dec. 2005. *Corresponding author ([email protected]). Published in Crop Sci. 46:2382–2386 (2006). Forage & Grazinglands doi:10.2135/cropsci2005.12.0458 ª Crop Science Society of America 677 S. Segoe Rd., Madison, WI 53711 USA

Abbreviations: ADF, acid detergent fiber; CP, crude protein; IVTD, in vitro true digestibility; NDF, neutral detergent fiber; NDFd, neutral detergent fiber digestibility; WSC, water soluble carbohydrates.

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Joseph, MI) and CP was estimated by multiplying total N by 6.25. Neutral detergent fiber and ADF were determined by the batch procedures outlined by ANKOM Technology Corp. (Fairport, NY). In vitro true digestibility was determined using the Daisy II system (ANKOM Technology Corp., Fairport, NY). Lyophilized stem and leaf samples were analyzed for WSC by a modification of the procedure of Li et al. (1996) using fructose as a standard. Anthrone reagent was added to an aliquot containing 200-mg WSC, and the mixture was vortexed and boiled for 8 min, after which light absorbance was read at 625 nm with a spectrophotometer. Dry matter yield, CP, IVTD, NDF, ADF, and WSC data were analyzed by the Proc Mixed Procedure of SAS (SAS Institute, 2001). Season and oat cultivar were considered fixed effects and replicates within location were considered random effects. When treatment effect was significant, means were separated using LSMEANS comparison (SAS Institute, 2001) with the PDIFF option.

RESULTS AND DISCUSSION Precipitation was near normal, based on the 30-yr mean, at both locations and soil moisture was not limiting in either autumn or summer. As expected, contrasting temperature patterns were observed between autumn and summer (Fig. 1). Averaged over locations, mean daily temperature declined from 238C at planting in August to 108C at harvest in October, and increased from 78C at planting in April to 218C at harvest in July.

Forage Yield and Plant Maturity Oat maturity 77 d after sowing was different between seasons and among cultivars (P , 0.05) (Table 1). In autumn, average maturity was midboot (Z46), while in early summer average maturity was midmilk (Z75). Among cultivars, averaged over location and season, Jim was the most mature (anthesis, Z66), ForagePlus was the least mature (inflorescence emergence, Z56) and Gem was intermediate (beginning of anthesis Z60). Likewise, within season, ForagePlus was the least mature and Jim was the most mature at both autumn (Z37 vs. Z55) and early summer (Z71 vs. Z77) harvests. Maturity differences among the three cultivars were much greater in autumn than in early summer. These results agree with those of Smith (1974) who found that a change from warm to cool temperature delayed panicle emergence in oat, while a change from cool to warm decreased time to reach this maturity stage. Yield differences among cultivars were not detected in autumn or early summer (P . 0.05). In autumn, oat forage yield was 1.0 Mg ha21 less than in early summer (P , 0.05) (Table 1). Chapko et al. (1991) reported that early summer forage yields were greater for late than early maturing oat lines harvested at the early heading stage, however in the current study all lines were harvested 77 d after sowing, not at a uniform maturity stage. Oat forage yield obtained during autumn was 40% greater than that reported by Maloney et al. (1999). Maloney planted 1 wk later than in the current study, and this could account for his lower yields. Early summer oat forage yield was similar to those reported in Table 1. Maturity stage and dry matter (DM) yield of three oat cultivars in autumn 2001 and early summer 2002. Values are pooled over two locations. Treatment

Maturity†

DM yield 21

Mg ha Jim Gem ForagePlus Mean Jim Gem ForagePlus Mean Jim Gem ForagePlus Season (S) Cultivars (CV) S 3 CV

Fig. 1. Maximum, average, and minimum temperatures during oat forage growth periods. Values are 15-d means from Arlington and Lancaster through the period August to October 2001 and April to July 2002.

Autumn 55c‡ 44d 37e 46 Early summer 77a 77a 71b 75 Cultivar means 66 60 56 Analysis of variance *** *** ***

6.7 6.8 6.7 6.7b 7.9 7.7 7.6 7.7a 7.3 7.3 7.1 * NS§ NS

* Significant at P 5 0.05. *** Significant at P 5 0.001. † Decimal code for maturity stages: 30–39, stem elongation; 40–49, boot; 50–58, inflorescence emergence; 60–68, anthesis; 70–77, milk development (Zadoks et al., 1974). ‡ Within each main effect (season or cultivar), means within a column followed by different letters are significantly different at P 5 0.05 based on LSMEANS comparisons (SAS Institute, 2001). When S 3 CV interaction is significant, values across season and cultivar within a column followed by different letters are different at P 5 0.05. § NS, not significant.

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other studies harvested at comparable maturity (Edmisten et al., 1998a; Folkins and Kaufmann, 1974; Stuthman and Marten, 1972; Cherney and Marten, 1982a).

Table 3. Water-soluble carbohydrates (WSC) and crude protein (CP) of three oat cultivars in autumn 2001 and early summer 2002. Values are pooled over two locations. WSC Treatment


Forage Quality

Table 2. Neutral detergent fiber (NDF) and acid detergent fiber (ADF) of three oat cultivars in autumn 2001 and early summer 2002. Values are pooled over two locations. NDF Whole plant

Leaf

ADF Stem

Whole plant

Leaf

Stem

225 233 250 236b

342 337 301 326b

270 269 291 276a

469 452 421 447a

247b 251b 270a

406a 394a 361b

*** *** NS

*** *** NS

21

Jim Gem ForagePlus Mean

554b‡ 529c 478d 521


573bc 595b 619a 596

Jim Gem ForagePlus

564 562 549

Season (S) Cultivars (CV) S 3 CV

*** * ***

Stem

CP Whole plant

Leaf

Stem

243 251 234 243a

99 112 135 115a

207 228 224 220b

74 93 105 90b

225 239 229

87c 102b 120a

*** NS§ NS

*** *** NS

21

Neutral detergent fiber and ADF concentrations of whole plant, leaf, and stem were greater in early summer than in autumn (P , 0.05) (Table 2). These differences are associated with more advanced maturity in the summerharvested compared to autumn-harvested oat (Table 1). Cherney and Marten (1982b) and Edmisten et al. (1998b) also reported that NDF and ADF concentrations of oat increased as maturity advanced in early summer. The season 3 cultivar interactions for whole plant NDF and ADF concentrations were significant; NDF and ADF in ForagePlus and Gem were lower in autumn than early summer, while in Jim whole plant NDFand ADF were the same in both seasons (Table 2). This is likely a result of much smaller maturity differences between autumn and summer for the early maturing Jim than for the other cultivars. The relative immaturity of ForagePlus likely contributed to lower stem NDF and ADF accumulation than Jim and Gem. Maloney et al. (1999) also found that when harvesting in autumn, mid- and late-maturity oat cultivars had lower NDF and ADF concentrations than early maturity cultivars. Leaf and stem WSC concentrations were 1.5 to 3.3 times greater in autumn than in early summer (P , 0.05) (Table 3). Smith (1975) reported that WSC concentrations in oat increased when temperature shifted from warm to

Treatment

Leaf

g kg DM† Autumn 421 599d 313cd 422 581d 302d 433 517e 277e 426b 565 297 Early summer 463 733a 340bc 466 711b 352ab 475 675c 358a 468a 707 350 Cultivar means 442 666 327 444 642 327 454 596 318 Analysis of variance *** *** *** NS§ *** NS NS * ***

* Significant at P 5 0.05. *** Significant at P 5 0.001. † DM, dry matter. ‡ Within each main effect (season or cultivar), means within a column followed by different letters are significantly different at P 5 0.05 based on LSMEANS comparisons (SAS Institute, 2001). When S 3 CV interaction is significant, values across season and cultivar within a column followed by different letters are different at P 5 0.05. § NS, not significant.


104 109 96 103a


76 65 50 64b

Jim Gem ForagePlus

90a 87a 73b


*** ** NS

g kg DM† Autumn 203b‡ 161c 211b 176b 250a 205a 221 180 Early summer 66c 120f 68c 134e 66c 150d 67 135 Cultivar means 134 141 140 155 158 177 Analysis of variance *** *** ** *** ** *

* Significant at P 5 0.05. ** Significant at P 5 0.01. *** Significant at P 5 0.001. † DM, dry matter. ‡ Within each main effect (season or cultivar), means within a column followed by different letters are significantly different at P 5 0.05 based on LSMEANS comparisons (SAS Institute, 2001). When S 3 CV interaction is significant, values across season and cultivar within a column followed by different letters are different at P 5 0.05. § NS, not significant.

cool, as a natural response to cold adaptation. Among cultivars, leaf WSC concentrations were greater in Jim and Gem than in ForagePlus (P , 0.05), but stem WSC concentrations were greater in ForagePlus (P , 0.05). The elevated sugar concentrations in oat during cool conditions were reported as a mechanism to protect tissues from freeze damage (Livingston and Premakumar, 2002). The season 3 cultivar interaction for stem WSC concentration (Table 3) occurred because in autumn, stem WSC concentrations were 15% higher in ForagePlus than in Jim or Gem, but differences among cultivars were not observed in early summer. The slow change in maturity in autumn and the leafy characteristic of ForagePlus resulted in WSC produced in leaves being stored in the stem rather than used for stem growth; while in early summer, oat maturity advanced normally and the WSC produced in leaves were transported to the stem and utilized for stem growth. Whole plant CP concentrations were higher in autumn than in early summer (P , 0.05) (Table 3). Less advanced maturity of oat cultivars in autumn than in summer (boot vs. milk) could explain a higher CP concentration during autumn. Previous reports also found that CP in oat decreased with an increase in maturity (Cherney and Marten, 1982b; Edmisten et al., 1998b). Among cultivars, whole plant and stem CP were higher in ForagePlus than in Jim and Gem, with no differences in leaf CP. The greater maturity of Jim and Gem could explain lower CP concentration compared to ForagePlus. These results agree with those of Peterson and Schrader (1974) who found higher N concentrations in


CONTRERAS-GOVEA & ALBRECHT: OAT FOR FORAGE

late maturity than in early and midmaturity oat cultivars harvested at panicle emergence. Overall, leaf CP did not differ significantly between seasons and among cultivars, indicating that leaf CP was less sensitive to seasonal effects than stem CP. In vitro true digestibility of whole plant and stem was greater in autumn than in early summer (P , 0.05), with no seasonal differences in leaf IVTD (P . 0.05) (Table 4). The greater whole plant and stem digestibility in autumn than in summer is not a surprise because lower NDF and ADF and greater WSC concentrations in autumn than in summer would result in higher digestibility. Among oat cultivars, ForagePlus had greater whole plant and stem IVTD than Gem and Jim in both seasons (P , 0.05). In autumn, ForagePlus was much less mature than Jim and Gem, explaining its greater digestibility, while in early summer, ForagePlus was about 8 d delayed in maturity (Z71) compared to Jim and Gem (Z77). Leaf IVTD was greater than 900 g kg21 for all cultivars in both seasons, indicating that leaf IVTD is less sensitive to the effect of season and maturity than stem. Neutral detergent fiber digestibility (NDFd) of whole plant and stem (Table 4) were affected by season and cultivar, and there was no season 3 cultivar interaction. Neutral detergent fiber digestibility of whole plant was 38% greater in autumn than early summer harvested oat (P , 0.05). Digestibility of stem NDF was 64% greater in autumn than summer (P , 0.05) but season had no effect on leaf NDFd. Among cultivars, whole plant and stem NDFd were greater in ForagePlus, parallel to trends in maturity ranking (Table 1). In addition to Table 4. In vitro true digestibility (IVTD) and neutral detergent fiber digestibility (NDFd) of three oat cultivars in autumn 2001 and early summer 2002. Values are pooled over two locations. IVTD Treatment

Whole plant

Leaf

NDFd Stem

Whole plant

Leaf

Stem

767 833 825 808

569 615 732 638a

793 811 809 804

337 374 457 389b

780b 822a 817a

453c 494b 594a

NS *** NS

*** *** NS

21


755 776 856 796a‡


641 657 713 671b

Jim Gem ForagePlus

698c 717b 785a


*** *** NS

g kg DM† Autumn 901 742 558 929 776 577 924 861 701 918 793a 612a Early summer 904 514 373 912 555 424 909 633 536 908 567b 445b Cultivar means 902b 628c 466c 921a 665b 501b 917a 747a 619a Analysis of variance NS§ *** *** * *** *** NS NS NS

* Significant at P 5 0.05. *** Significant at P 5 0.001. † DM, dry matter. ‡ Within each main effect (season or cultivar), means within a column followed by different letters are significantly different at P 5 0.05 based on LSMEANS comparisons (SAS Institute, 2001). When S 3 CV interaction is significant, values across season and cultivar within a column followed by different letters are different at P 5 0.05. § NS, not significant.

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lower NDF concentration in oat forage produced in autumn, NDFd is remarkably high compared to oat forage produced in early summer.

CONCLUSIONS Oat, sown in spring and harvested in early summer, has been used by livestock producers in the northern USA for years as hay, silage, and pasture. The relatively low nutritive value and especially the high NDF concentrations of oat forage make it difficult to utilize in rations of livestock requiring high levels digestible dry matter intake, such as lactating dairy cows. Our results show that oat forage produced in autumn with cooler temperature and shorter days has substantially greater nutritive value than oat produced in early summer. Neutral detergent fiber concentrations are lower and NDFd is remarkably greater in late season compared to early season oat forage. Furthermore, very high WSC concentrations will likely aid fermentation of oat forage harvested in autumn and preserved as silage. Autumn forage yield was not different among the cultivars evaluated, but ForagePlus, which is unusually leafy and late maturing, had much greater nutritive value, so is the cultivar of choice for autumn forage production. The extreme differences discovered between early and late season oat forage warrant further testing in livestock feeding trials. REFERENCES Chapko, L.B., M.A. Brinkman, and K.A. Albrecht. 1991. Genetic variation for forage yield and quality among grain oat genotypes harvested at early heading. Crop Sci. 31:874–878. Cherney, J.H., and G.C. Marten. 1982a. Small grain crop forage potential: I. Biological and chemical determinants of quality, and yield. Crop Sci. 22:227–231. Cherney, J.H., and G.C. Marten. 1982b. Small grain crop forage potential: II. Interrelationships among biological, chemical, morphological, and anatomical determinants of quality. Crop Sci. 22:240–245. Edmisten, K.L., J.T. Green, Jr., J.P. Mueller, and J.C. Burns. 1998a. Winter annual small grain forage potential. I. Dry matter yield in relation to morphological characteristics of four small grain species at six growth stages. Commun. Soil Sci. Plant Anal. 29:867–879. Edmisten, K.L., J.T. Green, Jr., J.P. Mueller, and J.C. Burns. 1998b. Winter annual small grain forage potential. II. Quantification of nutritive characteristics of four small grain species at six growth stages. Commun. Soil Sci. Plant Anal. 29:881–899. Folkins, L.P., and M.L. Kaufmann. 1974. Yield and morphological studies with oats for forage and grain production. Can. J. Plant Sci. 54:617–620. Ford, C.W., I.M. Morrison, and J.R. Wilson. 1979. Temperature effects on lignin, hemicellulose and cellulose in tropical and temperate grasses. Aust. J. Agric. Res. 30:621–633. Kelling, K.A., E.E. Schulte, L.G. Bundy, S.M. Combs, and J.P. Peters. 1991. Soil test recommendations for field, vegetable and fruit crops. Univ. of Wisconsin Ext. Bull. A2809. Univ. of Wisconsin Coop. Ext. Serv., Madison. Li, R., J.J. Volenec, B.C. Joern, and S.M. Cunningham. 1996. Seasonal changes in nonstructural carbohydrates, protein, and macronutrients in roots of alfalfa, red clover, sweetclover, and birdsfoot trefoil. Crop Sci. 36:617–623. Livingston, D.P., III, and R. Premakumar. 2002. Apoplastic carbohydrates do not account for differences in freezing tolerance of two winter-oat cultivars that have been second phase cold-hardened. Cereal Res. Commun. 30:375–381. Maloney, T.S., E.S. Oplinger, and K.A. Albrecht. 1999. Small grains for fall and spring forage. J. Prod. Agric. 12:488–494.

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