Production, Management, and the Environment 3

摘要

The objective of this study was to evaluate the effects of a mixture ofperennial forages (alfalfa, clover and tall fescue) seeded alone (control)or with different annual companion forages [sudangrass (SG), sudangrassbrown midrib (BMR) gene 12 (BSG) or sorghum-sudangrass BMR gene6 (BSSG)] on ensiling characteristics, and chemical composition and invitro total-tract NDF digestibility (IVTTNDFD) of experimental silages.Experimental plots (8 replicates per treatments) were harvested at 60 d(1st cut) and 90 d (2nd cut) at the bud stage of alfalfa. Harvested foragesat 90 d were ensiled in laboratory silos for 42 d. Forage indigestibleNDF (iNDF) was calculated by in vitro incubation at 240 h whereaspotentially degradable NDF (pdNDF) was calculated by subtractingiNDF from total NDF. Digestion rate (kd) of pdNDF was estimated byin vitro incubation at 24, 30 and 48 h. Data were analyzed as repeatedmeasures using the MIXED procedure of SAS with fixed effects oftreatment and cut. Chemical analysis of experimental silages showedthat companion forages reduced (P < 0.0001) lignin and crude protein(P = 0.0006) concentrations but increased (P < 0.0001) NDF and ADFcontents compared with the control. Neutral detergent insoluble protein(NDICP), water soluble carbohydrates, total digestible nutrients, andnet energy of lactation were similar in all treatments whereas acid detergentinsoluble protein (ADICP) was higher (P < 0.0001) for controlthan other treatments. In vitro TTNDFD followed the order (P < 0.0001):BSG and BSSG (average 64.7%) > SG (62.8%) > control (56.4%). Evidently,iNDF values were lower (P = 0.002) for SG, BSG and BSSG(average 19.5%) than control (28.9%). Digestion rate of potentially digestibleNDF was higher (P < 0.0001) with companion forages than control.In conclusion, seeding perennial forages with SG, BSG or BSSGmay improve chemical composition and NDF digestibility of silages.