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This article in AJ

  1. Vol. 66 No. 4, p. 510-513
     
    Received: Oct 17, 1973


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doi:10.2134/agronj1974.00021962006600040010x

Nutritive Characteristics of Kleingrass at Various Stages of Maturity. II. In vivo and In vitro Evaluations of Selected Varieties1

  1. F. M. Roquette,
  2. E. C. Holt and
  3. W. C. Ellis2

Abstract

Abstract

Recent studies hare shown that differences in neutral detergent fiber:neutral detergent solubles ratios (NDF:NDS) exist within experimental synthetic varieties of kleingrass (Panicum coloratum L.), and those varieties which had the highest NDF content were genetically closely related. This investigation was initiated to determine if selected varieties which differed in NDF:NDS also differed in in vitro and in vivo digestibility. The relationships between NDF, components of NDF, and various NDF component ratios vs. in vitro and in vivo digestibility were also studied using three synthetic varieties harvested at four stages of plant growth. Initial and subsequent regrowth forage was harvested as a certain percent of seed reached the soft dough stage, but before seed maturation had occurred. Cumulative growth forage was collected at the same chronological time as the final regrowth harvest date. At each harvest date, analyses were obtained for in vivo digestible dry matter (DDM), in vitro true digestible dry matter (IVDDM), neutral detergent fiber (NDF), digestibility of NDF (DNDF), and NDF components (hemicelluloses, cellulose, lignin, and ash). Percent DDM, IVDDM, and DNDF declined from 62, 74, and 60%, respectively, to 51, 65, and 47%, respectively, with plant maturity. NDF increased from 64% to 71% with plant age and accounted for approximately 92% (r = −0.96**) of the variability associated with DDM. The regression of DDM vs. DNDF resulted in a positive relationship (r = 0.99**). NDF vs. DNDF gave a highly significant negative relationship (r = −0.93**). Cellulose, lignin, and lignin:acid detergent fiber ratio were negatively related to DNDF; whereas, hemicellulose:NDF and hemicelluloses:cellulose ratios were positively related to DNDF. Regression with IVDDM and NDF components and component ratios were of the same magnitude as those relationships with DDM. The level of NDF showed a closer relationship to its digestibility than did any NDF component ratio with DNDF. NDF and DDM showed no difference between varieties, but the IVDMM analyses proved one of the varieties to be superior to the other two.

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