Sward structural characteristics and ingestive behaviour of beef heifers in a Pearl Millet pasture

Denise Baptaglin Montagner,Marta Gomes Da Rocha,Teresa Cristina Moraes Genro,Dalton Roso,Juliano Roman,Fernando Luiz Ferreira De Quadros

doi:10.1590/s1516-35982009000900005

Denise Baptaglin Montagner, Marta Gomes Da Rocha + Show 4 more

Open Access

https://doi.org/10.1590/s1516-35982009000900005

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Abstract

Ingestive behaviour of beef heifers and sward structural characteristics of Pearl Millet (Pennisetum americanum (L.) Leeke) were evaluated. The experiment was carried out in a randomized complete design following a repeated measure arrangement (three experimental periods) with three replications of two leaf blade masses (600 and 1,000 kg/ha DM), which were maintained using continuous grazing with variable stocking rate. The variables measured were sward height, herbage mass, leaf blade and stem bulk density in sward vertical strata (sward structural characteristics), grazing, idling, rumination time and bite rate of heifers (ingestive behaviour). Bite rate was modified by pasture management and was lower when the leaf blade mass was 1,000 kg/ha DM. The daily grazing, rumination and idling time of beef heifers were similar for both leaf blade masses. Structural variation of the sward, during the experimental period, altered the grazing, rumination and idling time of heifers, and affected the bite rate. In Southern Brazil, the beef heifers concentrate their grazing activities in the 12 p.m. to 6:00 p.m. period, decreasing the grazing between 12 a.m. and 6:00 a.m., even in the hottest season of the year.

Highlights

Sward structural changes may be relevant to determine variations in forage intake and on animal grazing performance
The degree of animal selective grazing is influenced by the sward structural characteristics and the grazing efficiency determines the quantity of nutrients ingested (Carvalho et al, 2007)
Management with 1,000 kg/ha leaf blade DM, throughout the experimental period, resulted on the highest sward height and, within the 55-94 days of experimental period the greatest herbage mass (Table 1). These interactions showed that the use of herbage mass or sward height values as a criteria in order to keep the intended leaf blade masses (LBM) value might not be adequate because of changes in the leaf/stem ratio during the Pearl Millet cycle, which changed from 1.6 (1-26 days) to 0.6 (55-94 days)

Summary

Introduction

Sward structural changes may be relevant to determine variations in forage intake and on animal grazing performance. More than forage mass, is the adequate indicator for forage species management (Maraschin, 2000). This statement can have more influence on grasses that, under favorable environmental circumstances, present high herbage accumulation in a short period of time such as Pearl Millet (Pennisetum americanum (L.) Leeke). Knowledge of the interaction between plants and animals helps management decisions because the grazing behaviour is modified by sward structure, which is altered by the grazing process (Carvalho et al, 2001), and it may result in changes in tiller density and persistency (Hodgson, 1990)

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