Estudo meta-analítico dos efeitos dos ciclos e intervalos de pastejo sobre as características de rendimento e qualidade forrageira do Capim elefante (Pennisetum purpureum Schumach cv. Napier), Tifton 85 (Cynodon spp.), Coast-cross (Cynodon dactylon (L.) Pers) e Tanzânia (Panicum maximum Jacq) para produção de leite a pasto

Abstract

The objective of this work was to analyze, through a meta-analytical study, the effects of cycles and grazing intervals on the characteristics of yield and forage quality of elephant grass (Pennisetum purpureum Schumach cv. Napier), Tifton 85 (Cynodon spp.), Coast -Cross (Cynodon dactylon (L.) Pers) and Tanzania (Panicum maximum Jacq) for milk production on pasture. A total of 7890 publications were found in the 8 databases searched (Google Scholar, Scopus, Web of Science, Pubmed, Scielo, Periódico Capes, Microsoft Academi and Word Wise Science). After applying the exclusion criteria resulted in 31 articles that made up the systematic review. For the meta-analysis, 15 articles were selected, and another 16 were excluded from the statistical analysis due to data inconsistency. The variables Forage Mass, Crude Protein (CP), Neutral Detergent Fiber (NDF), Acid Detergent Fiber (ADF), Dry Matter Percentage (%DM) and Milk Production (kg/cow/day) were analyzed) for Napier grass. For Coast-cross, Tifton 85 and Tanzania grass, forage mass production and Crude Protein levels were analyzed. These selected studies were submitted to statistical analysis of a Linear Mixed Model for each of the characteristics analyzed, with fixed effects of cycles and grazing intervals with their interactions. For Napier elephant grass, forage production had a significant effect with a minimum value of 1191kg/DM/ha in the 7th cycle and a more pronounced production of 5987 kg/DM/ha in the 12th cycle, evidencing a strong seasonality of Napier grass. The PB grazing cycles determined a linear growth from the 4th cycle (15.6%), where it remained constant until the 8th cycle, showing a decrease in subsequent cycles (11.4%). DM% and NDF contents did not differ statistically and ADF obtained decreasing values as the grazing cycles increased. For milk production, the daily values decreased as the cycles and grazing intervals increased, obtaining production from 9.27 kg/cow/day to 12.32 kg/cow/day of milk under rotational grazing. For the forage mass in Coast-cross grass, the means presented for the effect of the cycle showed variations between 2,516 Kg/DM/ha and 4,300 Kg/DM/ha. The 19-day interval between grazing presented an average of 3,593 Kg/DM/ha, while, in 20 days, its average decreased to 2,931 Kg/DM/ha. The CP contents decreased with the advance of the pasture utilization period in the cycles, ranging from 14 to 18% CP, and for grazing intervals of 19, 20 and 26 days, it presented variations from 14.5% to 17.6 % CP. The production of forage mass of Tifton 85 grass continued to grow until the 6th grazing cycle (7407 kg/DM/ha), for grazing intervals there was a growth of forage mass up to 28 days of interval (10047 kg/DM /there is). Crude protein averages ranged from 12.8% to 15.0% during the grazing cycles, for the grazing intervals Tifton 85 grass maintained levels of 13% CP for 28 and 30 days. As for the Tanzânia grass, the forage mass production in the grazing cycles remained between 3329 and 4921 kg/DM/ha, for grazing intervals with 48 days the production increased to 5674 kg/DM/ha. For CP, Tanzania grass maintained levels of 12% with a grazing interval of 30 days.