262. Animal Performance and Herbage Responses of Palisade Grass Submitted to Nitrogen Fertilizer Rates Under Grazing.

Abstract

The effects of increasing the N fertilizer application rate on marandu palisade grass [Urochloa brizantha (Hochst. ex A. Rich.) R.D. Webster] on forage accumulation rates (FAR), herbage mass, sward structure, nutritive value, nutrient intake, and individual and per area animal performance were investigated using a meta-analytical approach. The dataset included a five-year-long grazing experiment conducted in a completely randomized design with four levels of N (0, 90, 180, and 270 kg N/ha as urea) and three replicates. This study was conducted in a continuously stocked pasture during the forage growing season (December to April) using 72 young Nellore bulls (average 334 kg of body weight) in a tropical region. In addition to the field study, a comprehensive literature search was conducted across the Web of Science, Scopus, SciELO, and Google Scholar databases to identify papers investigating the effects of marandu palisade grass N fertilization rates on herbage responses and animal performance, with only mineral supplementation, published between 1985 and 2025. Surprisingly, we found only 7 papers evaluating the searchable variables under grazing. Increasing N fertilizer rate application increased FAR increased from 31 to 89 kg/dry matter/ha/day (P < 0.001), herbage mass responded quadratically to N doses (equation, P < 0.01), the proportion of green leaves increased from 33.1 to 45.4% (P = 0.03), while dead material decreased from 27.1 to 23.2% (P = 0.02), crude protein increased from 9.5 to 17.3% (P < 0.001), and neutral detergent fiber decreased from 63.1 to 55.6% (P = 0.036), no effect was observed on acid detergent fiber (P = 0.16) averaged 27.3%. Increasing the N fertilizer rate did not affect dry matter, organic matter, neutral detergent fiber, or acid detergent fiber intake, but it increased crude protein intake linearly (p < 0.01). Individual animal performance did not respond to increasing N fertilizer rate, whereas animal performance per area increased linearly (p < 0.001). stocking rate from 1.75 animal unit (AU = 450 kg)/ha to 6.55 AU/ha. In summary, N fertilization can be used to increase forage accumulation, crude protein, and animal performance per area. However, there are a limited number of studies evaluating the effects of N fertilization on these variables above under grazing. Marandu palisade grass, with an estimated 90 million hectares under cultivation, is among the most widely cultivated warm-season grasses worldwide. Lack of proper N fertilization is a major limiting factor for herbage production and pasture persistence. Variation in soil characteristics, sunlight, and precipitation patterns is known to affect herbage response to fertilization. Different interactions between these variables and herbage responses and animal performance are expected. Further studies under grazing are needed to fill this knowledge gap.