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Herbage intake and N excretion by sheep grazing monocultures or a mixture of grass and white clover
Author(s) -
ORR R. J.,
PENNING P. D.,
PARSONS A. J.,
CHAMPION R. A.
Publication year - 1995
Publication title -
grass and forage science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.716
H-Index - 56
eISSN - 1365-2494
pISSN - 0142-5242
DOI - 10.1111/j.1365-2494.1995.tb02291.x
Subject(s) - grazing , zoology , feces , excretion , biology , agronomy , dry matter , ecology , endocrinology
In 1988 and 1989, swards of grass (G0), while clover (C0) and grass/white clover (GC0) receiving no N fertilizer, and a grass sward supplied with 420 kg N ha −1 (G420), were grazed by non‐lactating sheep to maintain a sward surface height of 6 cm. Herbage organic matter (OM) intakes averaged between 1200 and 1700 g OM ewe −1 d −1 . For treatments G0, C0, GC0 and G420 respectively, the ewes' live weight gain was 102, 112, 100 and 110 g d −1 and changes in body condition scores were +0·28, +0·52, +0·36 and +0·44 units season −1 . However, the effect of treatment was not significant for either variable. There were similar levels of output of faecal N ewe −1 but significantly more urinary N ewe −1 was excreted on treatments C0 and G420, where the concentrations of N in herbage laminae were also higher. For example, in 1989, total daily N excreted was 39·7, 64·4, 44·0 and 63·3 g N ewe −1 for G0, C0, GC0 and G420 respectively. Taking into account the mean daily stocking rates, which were 19·4, 26·6, 27·2 and 36·5 ewe ha −1 , the total faeces and urine returns over the season were 161, 358, 249 and 484 kg N ha −1 for each treatment respectively. The herbage OM intakes ewes −1 d −1 measured in September and October were similar for C0 and G420, and so the intake of herbage OM ha −1 d −1 was related to stocking rate, i. e. the estimated herbage intake ha −1 over the growing season for the white clover monoculture was 73% of that for N‐fertilized grass. Excretal nitrogen returns to the pasture from grazed mono‐cultures of clover were high, and similar to those from a grass sward receiving 420 kg fertilizer N ha −1 . Consequently potential losses of N to the environment are high under these management systems.