Produtividade, composicao bromatologica e degradabilidade ruminal de cultivares de alfafa (Medicago sativa L.)

Abstract

The present work was conducted at the department ofAnimal Science - UFLA with the objective of evaluating alfalfe cultivars by their adaptation, yield, bromatologic composition and ruminal degradability in two growing seasons. Dry matter and crude protein yield of35 cultivars ofalfalfa andbromatolgic composition and ruminal degradability of the 15 most adapted ones were evahiated. The randomized blockdesignin three replicates was utUized. The datawere submitted to the variance analysis and means comparison by Scott-Knott test at 5%. Concerning the dry matter and crude protein yield kg/ha, the cultivars Crioula and P 30 stood out,with yields of1,754 and 1,632 kg/ha and408and376 kg/ha, respectivery. Forali the cultivars studied, yields in the rainy period were higher than those of the dry period except forthecultivar Crioula, which stood outwith51.92% oftheyield inthe dryperiod. Effect (PO.01) ofcultivars forNDF was found, standing outwith lower contents, me cultivars: Alto; Victoria SP INTA; P 30; P 205; MH 15 and BR 1. Interactions (PO.01) among cultivars andperiod were found for ADF, mean of the rainy period of 29.28% and dry period of26.86%, standing out the cultivars: Alia (24.57; 30.04); Victoria SP INTA (25.71; 29.73); P 205 (24.76; 27.65); Florida 77 (25.85; 30.52); BR 1 (26.36; 30.53) e BR 2 (26.06; 29.33) for dryperiod andrainy period, respectivery. For the variable MM, lower contents were obtained with the cultivars Alfe 200 (7.74); P 30 (8.06); Crioula (8.06%). For lignin content, the cultivars Alto, Semitt 711 and P 205 stood out with lower values (4.83; 4.62 and 4.59%, respectively). With the purpose of evaluating ruminal degradability, 3 Holstein cows fitted with permanent cannulas in the rumenwereused. The incubated material was previously dried at 65° Cin air-forced oven for 72 hours, the samples of the cultivars were processed in mill fitted with a 5mmmesh sieve, e remained in the rumen for 0, 6, 12, 24, 48, 72 e 96 hours ofincubation. The data obtained from disappearance of the nutriente DM, CP, NDF, ADF in the incubation times were submitted to the Gauss-Newton non-linear regression (Neter, Wasswrman and Kutner, 1985). For the determination of the degradability ofDM, CP,NDF,ADFof each cultivar theequation proposed byOrskov and McDonald (1979): Deg = a+b(le0*1) was used. lhe means were comparable by the Scott Knott test at the 5% levei of probability. No efifects (P>0.05) for DE of the DM of cultivars and periods were verified. Greater values of DE of the CP were observed in the rainy period. Variations among SF, IF ofthe CP ofcultivars and period were verified. For the fractionatíng ofNDF, variations were noticedin the ED, SF and DR analyzed in the rainy period. But for ADF, variations in ali the parameters evaluated in the rainy period as well as variations in PD, ED, UDF, IF andDR evaluated in the dry period were observed. The cultivars which stood out with the highest values ofED ofthe CP, NDF and AFD, regardless ofthe periodwere:P 205, Crioula, P 30, Florida77 e BR2.