Agriculture is an important component of the Montana economy. Each year we produce around 1,000,000 calves, and over 90% of these are shipped shortly after weaning to feedlots for fattening and slaughter. If it were economically feasible to retain calves within the state for a longer period of time, we could increase the amount of revenue flowing into the ranching sector, morbidity and mortality of calves would likely be reduced, and if the calves were fed locally grown barley our transportation costs for barley would be reduced. Dr. Jan Bowman, our ruminant nutritionist, and I started working on determining whether we could make locally grown barley a more competitive feed component in 1992. Our initial efforts were supported by the Montana Wheat and Barley Committee, and the North American Barley Genome Mapping Project. This seed capital helped us to establish the likely success of a feed barley improvement program, which led to significant investment in feed barley improvement through the CSREES-supported 'Feed Barley for Rangeland Cattle' project.
Our first priority was to determine whether variation existed among barley varieties for feedlot performance. We've published two manuscripts detailing our determination that significant variation can be found among normal barley variaties for feedlot performance. The first of these evaluated the European 2-rowed variety 'Gundhilde', the Canadian 2-rowed malting barley variety 'Harrington' and a blend of the two varieties against maize (see paper #1). A more reasoned selection of barley lines contrasted the two-rowed varieties, 'Baronesse' and 'Lewis', along with the 6-rowed malting standard 'Morex' and the 6-rowed feed barley variety, 'Steptoe' (see paper#2). This second paper confirmed the empirical observation of many feedlot operators: Steptoe is a poor feed barley. Morex proved to be the best variety of the group, with the two 2-rowed varieties intermediate. This experiment was also utilized to determine whether the two feedlots and whether barley grown at two locations provided comparable results. This paper demonstrates that varietal effect is an important determinant of animal performance, even with the variables of growout site and feedlot included.
Steptoe and Morex are parents of the best-characterized set of progeny lines currently available in all of the major crop plants. The Steptoe/Morex doubled haploid line population is the most commonly used population for barley genetics experiments. It's fortunate that the parents of this population differ so markedly for feedlot performance. The 150 Steptoe/Morex doubled haploids provided us with an easy and meaningful set of lines to evaluate the heritability of characters that might be associated with feed quality, and (if heritability was significant) to actually map the positions of relevant genes. We measured grain composition (starch, protein, ADF and other characters), and the amount of digestibility occurring over varying time periods in the rumen (Dry matter digestibility: DMD). We estimated heritabilities (highly significant for many characters) and mapped the locations of genes contributing to heritable variation (QTL). We then published this paper.
Since Montana is primarily a 2-rowed barley producing state, we developed a set of lines derived from a cross between Lewis and Baronesse, hoping to find significant transgressive segregation for feedlot performance. We measured agronomic performance, mapped a couple of hundred markers, anchored them to the published maps with our sequence-tagged-site markers, and identified three genes with large impact on grain yield . We selected eight lines with the appropriate high-yield genes which varied dramatically for dry matter digestibility. One manuscript detailed the performance of six of these , while another provided a more detailed look at the two most promising lines. One of these varieties, LB30, became the variety 'Valier' (PI610264) .
Our feedlot trial-derived evidence so far suggests that barley varieties can perform as well as corn in the feedlot. Several characters, including starch content, ADF content and rate of rumenal degradation play pivotal roles in feed barley value. Further, these traits appear to be heritable, mappable and manipulable. The question we then asked was, 'how far can low ADF, high starch content and slow rumenal fermentation be pushed?'
We accessed the USDA world collection of barley's spring core collection,
1500 lines which have been selected to span most of the variation available
in barley. We hand-harvested these 1500 rows, and processed the grain
for both compositional analysis. We evaluated grain digestibility
in both cattle (calf trial paper here ) and in
rats using a selected subsample of lines (rat feeding
trial here ). Surprisingly, these two experiments showed highly
significant correlations with one another. This suggests that some of the
characteristics which contribute to slow fermentation in cattle also contribute
to incomplete digestion in the rat.