ABSTRACT: The objective of this study was to evaluate the range of variation in feed quality characteristics available in barley from around the world. A sampling (1500 genotypes) from the World Barley Core Collection was planted in Bozeman in the spring of 1995. In situ DM digestibility after 3 h of incubation of 1480 genotypes was evaluated using 2 ruminally cannulated steers. Seventy-three genotypes were selected based on variation in DMD (highs and lows) and were planted in two field replications in Bozeman in the Spring of 1996. These 73 genotypes and 8 control varieties were evaluated for DM, starch, in situ DMD, ADF, in situ starch digestibility, digestible starch content, and particle size after dry rolling. The range in DMD in the World Core Collection was 15.6 to 62.1%, with a mean of 39.9% (SD = 7.42). The range, mean, and SD in starch, ADF, DMD, starch digestibility and particle size of the selected 73 genotypes was 36.2 to 58.1%, 51.8%, 4.31; .8 to 8.3%, 3.8%, 1.65; 11.9 to 63.5%, 38.6%, 18.24; 9.4 to 79.3%, 43.3%, 23.84; and 1037 to 1408 um, 1179 um, 76.03; respectively. Two-row head genotypes had higher (P < .10) starch content, higher (P < .001) DMD, higher (P < .001) starch digestibility, and lower (P < .001) ADF compared with 6-row head genotypes. There were no differences (P > .10) in feed quality measures between normal and dark colored aleurone genotypes, however, black genotypes (both the hull and aleurone were black) had lower (P < .01) starch, lower (P < .10) DMD, and lower (P < .05) starch digestibility than the normal or dark aleurone genotypes. There is substantial variation in the World Barley Core Collection for feed quality measures, and this variation could be exploited to design barley varieties specifically for feed quality.

Key Words: Barley, Feed Quality, Digestibility

Barley varieties are developed and selected based on agronomic characteristics. However, barley variety can affect rate of digestion (Surber and Bowman, 1994; Boss and Bowman, 1996b), feed value (Ovenell et al., 1993), and animal performance (Ovenell and Nelson, 1992; Boss and Bowman, 1996a). Some feed quality characteristics in barley, such as digestibility and particle size after processing, appear to be under genetic control (Bowman et al., 1996). If adequate variation in feed quality characteristics was available, barley varieties could be genetically selected for feed quality. The objective of this study was to determine the maximum range of variation available in feed quality characteristics in barley genotypes as represented in the World Barley Core Collection.

Fifteen hundred barley genotypes were selected from the World Barley Core Collection, and grown under irrigated conditions in Bozeman, MT during 1995. Grain was harvested from 1480 genotypes, cracked through a Buehler mill (to simulate dry rolling processing done prior to feeding barley), 5 g placed in 10 cm x 20 cm, 50 m pore size nylon bags (Ankom, Spencerport, NY) and incubated in the rumen of 2 cannulated steers for 3 h. Seventy-three genotypes selected based on variation in DMD (highs and lows) and eight control barley varieties were grown in two field replications in Bozeman in 1996.

Grain samples from the selected 73 genotypes grown in both 1995 and 1996 were analyzed for DM (AOAC, 1990), ADF (Van Soest et al., 1991), and starch content (Megazyme, Sidney, Australia). Dry matter digestibility was measured on the genotypes grown in 1996 using the same method described above. Residues in the nylon bags were analyzed for DM and starch content. In situ DM and starch digestibility were calculated. Mean particle size was determined on the cracked grain samples grown in both 1995 and 1996 by a dry sieving technique (Fisher et al., 1988).

The data were analyzed using the GLM procedure of SAS (1993) to test the effects of year, genotype, head, and hull. When a significant F-value was found (P < .05), the means were separated using LSD.

The range in DM digestibility in the 1480 genotypes from the World Barley Core Collection was 15.6 to 62.1%, with a mean of 39.9%. The 73 genotypes selected from this group had a range in DM digestibility of 11.9 to 63.5%, with a mean of 38.6%.

Population means, ranges, and coefficients of variation for the measured feed quality characteristics in the 73 genotypes grown in 1995 and 1996 are presented in Table 1. Substantial variation exists among barley genotypes for starch, ADF, particle size, and digestibility, as shown by the coefficient of variation values than range from 6.45 to 55.08.

Barley genotype affected (P < .001) starch content, ADF, particle size, and DM digestibility. No effect (P > .10) was seen in DM content due to barley genotype.

Six-row head morphology genotypes had lower (P <.001) starch content and DM digestibility, and higher (P < .001) ADF and particle size, compared with 2-row head types (Table 2). Two-row head types have been shown to exhibit higher animal performance compared with 6-row types, when fed in high concentrate diets (Boss and Bowman, 1996a).

Hulless genotypes had lower (P < .001) starch content and higher (P < .001) ADF than hulled genotypes. No differences (P > .10) were seen in particle size or DM digestibility between hulled and hulless types. Year affected (P < .001) DM content, ADF, starch, and particle size of the barley genotypes, but no effect (P > .10) was seen in DM digestibility due to year.

Substantial variation exists in barley genotypes selected from the World Barley Core Collection for starch, ADF, particle size, and DM digestibility. The potential exists to exploit this variation for the development of barley genotypes specifically designed for feed quality.

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