This study investigated the effects of, and interactions between, dietary grain source and marginal changes in alfalfa hay (AH) particle size (PS) on digestive processes of dairy cows. A total of eight Holstein dairy cows (175 days in milk) were allocated in a replicated 4 3 4 Latin square design with four 21-day periods. The experiment was a 2 3 2 factorial arrangement with two levels of theoretical PS of AH (fine 5 15 mm or long 5 30 mm) each combined with two different sources of cereal grains (barley grain alone or barley plus corn grain in a 50 : 50 ratio). Results showed that cows consuming diets supplemented with corn had greater dry matter and nutrient intakes (P , 0.01), independent of forage PS. In addition, the apparent digestibility of fiber fractions was greater for diets supplemented with corn (P 5 0.01). The feeding of barley grain-based diets was associated with greater apparent digestibility of non-fiber carbohydrates, and this variable was even greater when long AH was fed (P 5 0.04). Moreover, the feeding of long AH resulted in longer time spent eating (P 5 0.03) and higher pH (P , 0.01), as well as a tendency for higher acetate-to-propionate ratio in the rumen fluid (P 5 0.06) at 3 h post feeding. In conclusion, the results indicated that the marginal increase of PS of AH may prolong eating time and improve rumen fermentation, particularly in diets based on barley grain. Partial substitution of barley grain by corn can improve feed intake and fiber digestibility in mid-lactation dairy cows.Keywords: physically effective NDF, hay particle size, barley, corn ImplicationsThis study tested the hypothesis that grain fermentability and particle size (PS) of alfalfa hay have the potential to modify rumen conditions, digestion and performance of mid-lactation dairy cows. Indeed, the results showed an improved rumen environment and nutrient digestibility in cows fed a diet containing corn grain and long forage PS, respectively.

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Association mapping identifies quantitative trait loci (QTLs) by examining the marker-trait associations that can be attributed to the strength of linkage disequilibrium between markers and functional polymorphisms across a set of diverse germplasm. In this study, association mapping was performed to detect QTL-linked and genome wide SSR markers linked to phenolic compounds of extraction meal in a population of 49 genetically diverse oilseed rape cultivars of dark-seeded, wintertype oilseed rape accessions. Correction for population structure was performed using 559 genome wide SSR markers. Results showed that seed colour is an important contributor to seed meal quality. Totally, 52 SSR markers linked to phenolic compounds were detected, five of them being QTL linked markers. Some of these markers were already mapped on Brassica napus chromosomes that contain known QTL controlling oilseed rape meal quality traits. Our results demonstrate that association mapping is a useful approach to complement and enhance previous QTL information for marker-assisted selection.

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