Relationship between chemical composition of native forage and nutrient digestibility by Tibetan sheep on the Qinghai–Tibetan Plateau
Date
2018-04-02
Journal Title
Journal ISSN
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Publisher
Oxford University Press
Abstract
To better utilize native pasture at the
high altitude region, three-consecutive-year feeding
experiments and a total of seven metabolism trials
were conducted to evaluate the impact of three forage
stages of maturity on the chemical composition,
nutrient digestibility, and energy metabolism of native
forage in Tibetan sheep on the Qinghai–Tibetan
Plateau (QTP). Forages were harvested from June to
July, August to October, and November to December
of 2011 to 2013, corresponding to the vegetative,
bloom, and senescent stages of the annual forages.
Twenty male Tibetan sheep were selected for each
study and fed native forage ad libitum. The digestibility
of DM, OM, CP, NDF, ADF, DE, DE/GE, and
ME/GE were greatest (P < 0.01) from the vegetative
stage, intermediate (P < 0.01) from the bloom stage,
and least (P < 0.01) from the senescent stage. Nutrient
digestibility and energy parameters correlated positively
(linear, 0.422 to 0.778; quadratic, 0.568 to
0.815; P < 0.01) with the CP content of forage but
correlated negatively with the content of NDF (linear,
0.343 to 0.689; quadratic, 0.444 to 0.777; P ≤ 0.02),
ADF (linear, 0.563 to 0.766; quadratic, 0.582 to 0.770;
P < 0.01), and ether extract (EE, linear, 0.283 to 0.574;
quadratic, 0.366 to 0.718; P ≤ 0.04) of forage. For each
predicted variable, the prediction of DMI expressed
as grams per kilogram of BW (g/kg BW·d) yielded
a greater R2 value (0.677 to 0.761 vs. 0.616 to 0.711)
compared with the equations of DMI expressed
as g/kg metabolic BW by step-wise regression. The
results suggest that parameters of forage CP, NDF,
and ADF content were most closely related to nutrient
digestibility. Contrary to previous studies, in this
study, ADF content had a greater linear relationship
(0.766 vs. 0.563 to 0.732) with OM digestibility than
the other parameters of nutrient digestibility. The
quadratic relationship between forage CP content and
CP digestibility indicates that when forage CP content
exceeds the peak point (9.7% DM in the present
study), increasing forage CP content could decrease
CP digestibility when Tibetan sheep were offered
native forage alone on the QTP. Additionally, using
the forage CP, EE, NDF, and ADF content to predict
DMI (g/kg BW·d) yielded the best fit equation
for Tibetan sheep living in the northeast portion of
the QTP
Description
Publication history: Accepted - 06 March 2018; Published - 02 april 2018.
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Article
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Keywords
chemical composition, correlation analysis, digestibility, native forage, sheep
Citation
Yang, C., Gao, P., Hou, F., Yan, T., Chang, S., Chen, X. and Wang, Z. (2018) ‘Relationship between chemical composition of native forage and nutrient digestibility by Tibetan sheep on the Qinghai–Tibetan Plateau’, Journal of Animal Science, 96(3), pp. 1140–1149. doi: 10.1093/jas/sky002.