Abstract
Digestibility of feeds is a commonly used nutritive parameter and can be estimated through several techniques. The objective of the present study was to compare the precision and accuracy of different IVDMD techniques used to estimate in vivo DM digestibility (IVdig) of tall wheatgrass hay and haylage (IVdig: 42.2 to 53.3%). Forages were conserved after 1 of 3 regrowth periods (66, 96, and 162 d), generating a representative range of digestibilities, and were fed ad libitum to steers. The study analyzed goodness-of-fit for predictions of in vivo digestibility using in vitro apparent DM digestibility from Tilley and Terry (T&Tdig) and a DaisyII Incubator (DAISYdig), and in vitro ruminal DM degradability using the gas-production technique (GASdeg). In addition, 2 predictive equations from the literature were tested, Van Soest (VSdig) and Rohweder (Rodig), based on fiber content of forage. The in vitro techniques showed higher correlations with IVdig (R2 = 0.97, 0.94, and 0.93, respectively) than VSdig and Rodig (R2 = 0.64 and 0.35, respectively). Biases were observed in all techniques, with correction factors of 0.34 for T&Tdig, 0.74 for GASdeg, and 0.88 for DAISYdig. As a consequence, DAISYdig showed the greatest concordance (ρc = 0.85) compared with T&Tdig and GASdeg (ρc 0.34 and 0.72, respectively), the predictive equations showed the poorest fits (ρc 0.21 and 0.33 for VSdig and Rodig, respectively). Therefore, the recommended techniques are DAISYdig or GASdeg, depending on requirements. However, all in vitro techniques showed biases, highlighting certain limitations for conserved forages.
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Claims 8
Claim · model-written summary
In vitro digestibility techniques correlated more highly with in vivo digestibility (R2 0.93 to 0.97) than the VSdig and Rodig predictive equations (R2 0.64 and 0.35).
- Taxon
- Thinopyrum ponticum
Thinopyrum obtusiflorumt0 - Outcome
- correlations with IVdige1
- Direction
- highere1
- Value
- R2 = 0.97, 0.94, and 0.93e1
- Qualifier
- R2 = 0.64 and 0.35, respectivelye1
- Comparator
- VSdig and Rodige1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Thinopyrum ponticum (Tall Wheatgrass) Hay and Haylage”
e1“The in vitro techniques showed higher correlations with IVdig (R2 = 0.97, 0.94, and 0.93, respectively) than VSdig and Rodig (R2 = 0.64 and 0.35, respectively)”
Claim · model-written summary
Biases were observed in all in vitro digestibility techniques.
- Taxon
- Thinopyrum ponticumThinopyrum obtusiflorumt0
- Outcome
- Biasese1
- Comparator
- all techniquese1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Thinopyrum ponticum (Tall Wheatgrass) Hay and Haylage”
e1“Biases were observed in all techniques”
Claim · model-written summary
The T&Tdig technique had a bias correction factor of 0.34.
- Taxon
- Thinopyrum ponticumThinopyrum obtusiflorumt0
- Outcome
- correction factorse1
- Value
- 0.34e1
- Qualifier
- for T&Tdige1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Thinopyrum ponticum (Tall Wheatgrass) Hay and Haylage”
e1“correction factors of 0.34 for T&Tdig, 0.74 for GASdeg, and 0.88 for DAISYdig”
Claim · model-written summary
The GASdeg technique had a bias correction factor of 0.74.
- Taxon
- Thinopyrum ponticumThinopyrum obtusiflorumt0
- Outcome
- correction factorse1
- Value
- 0.74e1
- Qualifier
- for GASdege1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Thinopyrum ponticum (Tall Wheatgrass) Hay and Haylage”
e1“correction factors of 0.34 for T&Tdig, 0.74 for GASdeg, and 0.88 for DAISYdig”
Claim · model-written summary
The DAISYdig technique had a bias correction factor of 0.88.
- Taxon
- Thinopyrum ponticumThinopyrum obtusiflorumt0
- Outcome
- correction factorse1
- Value
- 0.88e1
- Qualifier
- for DAISYdige1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Thinopyrum ponticum (Tall Wheatgrass) Hay and Haylage”
e1“correction factors of 0.34 for T&Tdig, 0.74 for GASdeg, and 0.88 for DAISYdig”
Claim · model-written summary
DAISYdig had the greatest concordance with in vivo digestibility (ρc = 0.85), above T&Tdig and GASdeg.
- Taxon
- Thinopyrum ponticumThinopyrum obtusiflorumt0
- Outcome
- concordancee1
- Value
- ρc = 0.85e1
- Qualifier
- ρc 0.34 and 0.72, respectivelye1
- Comparator
- T&Tdig and GASdege1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Thinopyrum ponticum (Tall Wheatgrass) Hay and Haylage”
e1“DAISYdig showed the greatest concordance (ρc = 0.85) compared with T&Tdig and GASdeg (ρc 0.34 and 0.72, respectively)”
Claim · model-written summary
The predictive equations VSdig and Rodig had the poorest concordance with in vivo digestibility (ρc 0.21 and 0.33).
- Taxon
- Thinopyrum ponticumThinopyrum obtusiflorumt0
- Outcome
- fitse1
- Direction
- pooreste1
- Value
- ρc 0.21 and 0.33e1
- Qualifier
- for VSdig and Rodige1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Thinopyrum ponticum (Tall Wheatgrass) Hay and Haylage”
e1“the predictive equations showed the poorest fits (ρc 0.21 and 0.33 for VSdig and Rodig, respectively)”
Claim · model-written summary
DAISYdig or GASdeg is recommended for estimating digestibility of tall wheatgrass forage, depending on requirements.
- Taxon
- Thinopyrum ponticumThinopyrum obtusiflorumt0
- Outcome
- recommended techniquese1
- Qualifier
- DAISYdig or GASdege1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Thinopyrum ponticum (Tall Wheatgrass) Hay and Haylage”
e1“the recommended techniques are DAISYdig or GASdeg, depending on requirements”