FORAGE YIELD, ELONGATION RATE AND BOTANICAL COMPOSITION OF Lolium multiflorum LAMB. IN RESPONSE TO DIFFERENT GRAZING INTERVALS AND INTEN

Abstract

Background. The intensity and grazing interval are two very important factors in the management of grasslands that can affect the morphological and productive behavior of the forage species. Due to its productivity and persistence to grazing, ryegrass (Lolium multiflorum Lamb.) is the main source of pasture for backgrounding cattle during winter-spring in northwestern México. Therefore, it is important to generate knowledge of established pasture with grasses to generate information that will serve producers to improve the economic profitability of livestock activities. Objective. The objective of this study was to evaluate the influence of grazing intensity (GI) and grazing interval (GIv) on forage yield, elongation rate and botanical composition of ryegrass, under ambient conditions of this arid region. Hypothesis. It is evident to observe that GIv and GI modify the forage yield, elongation rate and botanical composition of L. multiflorum established in irrigated grassland in temperate climate zones. Methodology. The study involved 1008 crossed bull calves (Bos indicus ˣ Bos taurus) of 16 months of age. Calves were distributed in a 3 ˣ 2 factorial arrangement in an RCB design, with three repetitions. Three GIv (21, 28 and 35-d) and two GI (grazed to 4 to 6 cm vs 10 to 12 cm) were evaluated. This 105-d trial was initiated on January 16, 2019, 90 days post-planting and finished on May 01, 2019, using an intensive grazing system with stocking rate of 56 calves per ha. The main effects of grazing interval were evaluated by means of orthogonal polynomials. Results. Forage yield increased linearly (P<0.01) with increasing GIv; whereas with GIv of 28 and 35 days, yield increased with increased GI (interaction, P< 0.01). Stem contribution to yield increased linearly (P<.01) with increasing GIv. Forage lef to stem ratio decreased with increasing GIv and GI; however, at 28-d GIv, GI did not affect this ratio. Implications. The results of the present study contribute to know the productive parameters of an established L. multiflorum meadow in zones of arid climates under two intensities and three grazing intervals. Conclusions. In conclusion, both grazing intensity and grazing interval are effective management tools to modify ryegrass performance during the hot ambient conditions of the Sonoran Desert region, associated with late-spring grazing period.