Abstract
ABSTRACT The objective of this study was to evaluate the apparent selectivity of sheep in marandu palisadegrass (Urochloa brizantha cv. Marandu) pastures with four heights at the beginning of the deferment period (15, 25, 35 and 45cm). The deferment period was 92 days and started on 03/21/2014. Evaluations occurred in the beginning (first week), middle (45th day) and end (92nd day) of the grazing period, in winter (06/21/2014 to 09/21/2014). Deferred pastures with 15 and 25cm presented lower forage mass (FM), but higher live leaf (LL) percentage in FM than deferred pastures with 35 and 45cm. The live stem percentage in the FM and the apparent selectivity index (ASI) of the LL were superior in the deferred pasture with 45cm. The dead stem (DS) percentage in the grazing simulation (GS) and the ASI of this morphological component were lower in the pasture with 15cm, compared to the deferred pasture with 45cm. The FM and the LL percentages in FM and in the GS sample decreased, while the DS percentages in FM and in GS sample increased with the grazing period. Marandu palisadegrass with 15cm at beginning of the deferment period improves the morphology of the deferred pasture. Selective grazing is difficult during the grazing period.
Highlights
Selectivity is an inherent characteristic of grazing animals and, in monoculture pastures, can be characterized by the preferential consumption of some plant parts, to the detriment of others
The live stem percentage in the forage mass (FM) and the apparent selectivity index (ASI) of the live leaf (LL) were superior in the deferred pasture with 45cm
The dead stem percentage in the grazing simulation (GS) and the ASI of this morphological component were lower (P
Summary
Selectivity is an inherent characteristic of grazing animals and, in monoculture pastures, can be characterized by the preferential consumption of some plant parts (live leaf), to the detriment of others (stem and dead material). When the deferment of pasture use occurs, it is possible to obtain high forage mass during winter, but with morphological composition generally unfavorable to animal consumption and performance, that is, with high stem and dead material percentages, but low live leaf percentage (Sousa et al, 2012; Vilela et al, 2012). If the morphology of deferred pasture is very unfavorable, the animal may find difficulty to select the live leaf and to reject the live stem and dead material (Santos et al, 2016) This scenario can occur from the beginning and, especially, at the end of the use period of deferred pasture, in late winter (Silva et al, 2016). The apparent selectivity of the sheep during the winter
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