title: Effect of maturity at harvest for whole-crop barley and oat on dry matter intake, sorting, and digestibility when fed to beef cattle.
abstract: The objectives were to evaluate the effect of harvest maturity of whole-crop oat (Study 1) and whole-crop barley (Study 2) on forage intake and sorting, ruminal fermentation, ruminal digestibility, and total tract digestibility when fed to beef heifers. In Study 1, 3 ruminally cannulated heifers (417 ± 5 kg) were used in a 3 × 3 Latin square design with 24-d periods. Whole-crop oat forage harvested at the late milk (LMILK), hard dough (HD), or ripe (RP) stages was fed for ad libitum intake and heifers were supplemented (1% of BW) with alfalfa pellets, barley grain, canola meal, and a mineral and vitamin pellet. Maturity at harvest for whole-crop oat did not affect ( ≥ 0.058) forage intake, DE intake, amount of forage refused, ruminal short-chain fatty acid concentration, or digestibility of DM, OM, NDF, and ADF. Ruminal starch digestibility decreased ( < 0.001) from 92.6% at the LMILK stage to 90.0% at the RP stage, with total tract starch digestibility decreasing ( = 0.043) from 95.8% at the LMILK stage to 94.8% at the RP stage. Ruminal CP digestibility was reduced at the HD stage compared with the LMILK and RP stages ( < 0.001). Mean ruminal pH was greatest for the LMILK stage (6.36; = 0.003) compared with the HD and RP stages (6.30 and 6.28, respectively). In Study 2, 6 ruminally cannulated heifers (273 ± 16 kg) were used in a replicated 3 × 3 Latin square design with 24-d periods. Dietary treatments included ad libitum access to whole-crop barley harvested at the LMILK, HD, or RP stage and a constant rate (0.8% BW) of supplement containing alfalfa pellets, barley grain, canola meal, and a mineral and vitamin pellet. Dry matter intake, ruminal content mass, and feeding behavior were not affected by harvest maturity ( ≥ 0.16). There was a decrease in total tract digestibility of DM, OM, and NDF observed at the HD stage compared with the LMILK and RP stages ( ≤ 0.004). Ruminal NDF digestibility decreased from 69.7% at the LMILK stage to 54.4% at the HD stage and 54.9% at the RP stage ( = 0.001), whereas ruminal ADF digestibility decreased from 70.0% at the LMILK stage to 44.4% at the HD stage and 42.5% at the RP stage ( = 0.002). Minimum and mean ruminal pH were least for the LMILK stage, intermediate at the RP stage, and greatest at the HD stage ( = 0.016 and = 0.031, respectively). These data suggest that despite reductions in ruminal digestibility of NDF and ADF with advancing maturity, harvesting whole-crop oat and barley forage at the HD and RP stages of maturity did not negatively affect DMI, fermentation characteristics, or DE relative to whole-crop cereal forage harvested at the LMILK stage.
authors.forename: C L
authors.initials: CL
authors.lastname: Rosser
authors.forename: A D
authors.initials: AD
authors.lastname: Beattie
authors.forename: H C
authors.initials: HC
authors.lastname: Block
authors.forename: J J
authors.initials: JJ
authors.lastname: McKinnon
authors.forename: H A
authors.initials: HA
authors.lastname: Lardner
authors.forename: P
authors.initials: P
authors.lastname: Górka
authors.forename: G B
authors.initials: GB
authors.lastname: Penner
mesh_terms: D000821:Animal Feed / Q000032:analysis; D000818:Animals; D018554:Avena / Q000737:chemistry*; D002417:Cattle / Q000502:physiology*; D004032:Diet / Q000662:veterinary; D019587:Dietary Supplements; D004063:Digestion / Q000187:drug effects*; D004435:Eating; D005232:Fatty Acids, Volatile / Q000378:metabolism; D005247:Feeding Behavior; D005260:Female; D005285:Fermentation; D001467:Hordeum / Q000737:chemistry*; D008903:Minerals / Q000378:metabolism; D013213:Starch / Q000378:metabolism
chemical_list: D005232:Fatty Acids, Volatile; D008903:Minerals; D013213:Starch