The objective of this study was to evaluate the effects of perennial mixtures (alfalfa, clover and tall fescue; control) seeded alone or with a companion forage [Sudangrass (SG), Sudangrass brown midrib (BMR) gene 12 (BSG), Sorghum-Sudangrass BMR gene 6 (BSSG) or oat] on forage yield, chemical composition and in vitro total tract NDF digestibility (TTNDFD]. Experimental plots (8 replicates/treatment) were harvested 60 d (1st cut) and 90 d (2nd cut) at bud stage of alfalfa. The TTNDFD was estimated from potentially digestible NDF (pdNDF), digestion rate and passage rate while forage indigestible NDF (iNDF) was calculated from 240 h in vitro incubation. Potentially degradable NDF was calculated by subtracting iNDF from total NDF whereas digestion rate was estimated by in vitro incubation at 24, 30 and 48 h. Data were analyzed as repeated measures using the MIXED procedure of SAS with fixed effects of treatment and cut. Results showed that total forage yield (2nd cut) was higher (P < 0.0001) for SG (6.8 T/ha), BSSG (6.7 T/ha) and BSG (6.3 T/ha) than control (4.1 T/ha). Oat produced 87% less forage yield in the second cut than first cut. Companion forages reduced (P < 0.0001) the yield of perennial legumes and weeds. Relative to control, companion forages reduced (P < 0.0001) lignin and crude protein but increased (P < 0.0001) NDF and ADF contents of harvested forages. Water-soluble carbohydrate concentration was highest with oat (12.4%), intermediate with SG (9.5%), BSG (9.1%) and BSSG (10.7%) and lowest with control (7.0%). Estimated milk yield was higher (P < 0.0001) for companion forages than control. The iNDF was lower (P < 0.0001) with BSSG than control and oat treatment. In vitro TTNDFD of second cut followed the order (P < 0.0001): BSG and BSSG (average 62.2%) > SG (58.5%) > oat (53.3%) > control (52.3%). It was concluded that establishing perennial forages with SG, BSG or BSSG may improve forage yields, nutritive value and fiber digestibility.
Key words: cows, forages, fiber digestibility.
Published in the proceedings of the Animal Nutrition Conference of Canada 2020. For information on the event, past and future editions, check out https://animalnutritionconference.ca/.