Nutritional evaluation of barley varieties grown for silage

Abstract Text:

This study evaluated the nutritional and neutral detergent fiber (NDF) digestibility characteristics of common barley varieties grown for silage by beef and dairy operations in western Canada. Of 135 silage samples collected over two crop years (2012 and 2013), 80 samples harvested at the mid-dough stage, representing seven varieties (Conlon, CDC Copeland, CDC Cowboy, Falcon, Legacy, AC Metcalfe and Xena) were selected for analysis. Chemical composition, NDF digestibility (NDFD) and indigestible NDF (INDF) content were analyzed as randomized complete block design with year as random blocking factor using mixed model procedure of SAS (9.4). Average pH and dry matter (DM) were 4.05 ± 0.17 and 36.8 ± 4.1, respectively. AC Metcalfe had higher (P<0.05) CP content relative to CDC Copeland and Xena with intermediate values for the other varieties. Acid detergent fiber (ADF) content was higher (P<0.05) for CDC Cowboy and AC Metcalfe relative to Conlon. Similarly, CDC Cowboy had a higher (P<0.05) NDF content relative to Conlon, Falcon and Legacy. AC Metcalfe had a higher (P<0.05) lignin content than CDC Copeland. Starch content of Legacy and Conlon was higher (P<0.05) than that of CDC Cowboy with intermediate values for the other varieties. Neutral detergent fiber digestibility (%NDF) after 6 (NDFD_6h) and 30-h (NDFD_30h) of incubation in an ANKOM Daisy^II system indicated that Legacy and Falcon had a higher (P<0.05) NDFD_6h relative to the other varieties; while CDC Cowboy had the highest (P<0.05) NDFD_30h followed by CDC Copeland, AC Metcalfe, Falcon and Conlon with Xena and Legacy being the lowest. Rumen in situ incubation for 288-h to determine the INDF (% NDF) content of barley varieties indicated that CDC Cowboy had a higher (P<0.05) potentially digestible NDF (pdNDF) content relative to AC Metcalfe with other varieties being intermediate. Silage fermentation parameters including VFA, lactate and ammonia concentrations did not differ among varieties. These results indicate that barley varieties grown for silage in western Canada vary with respect to chemical composition, NDFD and pdNDF content and suggest that nutritional as well as agronomic characteristics are important for producers to consider when selecting barley varieties for silage. Selection pressure by plant breeders for increased NDFD may help lead to new or improved forage barley varieties for ruminant production systems. 

Keywords: barley silage, variety, NDFD