科研之友
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摘要
Two experiments were carried out to evaluate different dosing and sampling regimes for estimating the dry matter intake (DMI) of vegetation by grazing beef cattle. Experiment 1 compared the DMI of a perennial ryegrass pasture by 48 grazing beef cattle dosed with C-32 n-alkane and faecally sampled at different time intervals. The cattle, of dairy and suckler origin, were balanced by origin and allocated to one of three alkane-dosing treatments (n=16): T1, dosed once daily (10.30 h) with two 500 mg boluses of C-32 alkanes; T2, dosed twice daily (09.00 and 16.00 h) with a 500 mg bolus of C-32 n-alkane; and T3, dosed twice daily (07.00 and 19.00 h) with a 500 mg bolus of C-32 n-alkane. Faecal samples were collected concurrently with dosing in each treatment. Dosing interval had no effect on estimated DMI, when calculated using the n-alkane content of faeces sampled concurrently with dosing, suggesting that once-daily dosing with concurrent faecal sampling is adequate to estimate DMI by beef cattle. The objective of Expt 2 was to compare the accuracy of herbage DMI estimated using a once-daily C-32 alkane dosing regime and n-alkane concentrations in faeces sampled at 09.00, 13.00, 17.00 and 21.00 h, against DMI measured directly. Twelve Holstein-Friesian bulls (mean body weight 265 kg) were housed individually in digestibility stalls and offered harvested perennial ryegrass or harvested semi-natural upland vegetation, both ad libitum. The DMI estimated by once-daily dosing with n-alkane and concurrent per rectum faecal sampling did not differ significantly from the directly measured DMI for either herbage type. It is concluded that a once-daily alkane dosing and concurrent faecal sampling protocol is adequate to reliably estimate the DMI of both upland and lowland pasture vegetation by beef cattle.
- 出版日期2015-3
