Influencia del sistema de pastoreo con pequeños rumiantes en un agostadero del semiárido Zacatecano. I Vegetación nativa

Abstract

The objective of this study was to measure growth, covering and chemical composition of native vegetation under two grazing systems. Goats and sheep with an esophageal fistula were used to collect forage intake samples under rotational and continuous grazing systems. Changes in dry matter, vegetation cover and botanical composition were monitored. Dry matter values changed from 30 to 471 kg ha-1 in continuous grazing and from 101 to 1,151 kg ha-1 in rotational grazing. Such behavior was partially due to a higher annual rainfall during the study period (600 mm) than the mean annual rainfall (400 mm). Vegetation cover under rotational grazing was 60 % against 35 % found in continuous grazing. Crude protein values did not show differences between both grazing systems. However, protein values showed differences between seasons and animal species (P<0.01). Goats collected more protein than sheep, with higher values in summer (12.0 %) and lower in winter and spring (5.3 and 4.3 %, respectively). Ashes, acid detergent fiber and neutral detergent fiber were also evaluated. Diet protein content was not affected for the big difference in plant species number between both grazing systems. It is concluded that the small ruminant grazing selectivity played an important role in this matter.