Effects of feeding hybrid rye grain as a replacement for barley grain on dry matter intake, ruminal fermentation, and the site and extent of nutrient digestion in finishing beef heifers.

The objective of this study was to evaluate effects of increasing the inclusion of dry-rolled hybrid rye (HR) as a replacement for dry-rolled barley grain (DRB) on feed intake, ruminal fermentation, and the site and extent of nutrient digestion for finishing cattle. Eight ruminally and duodenally cannulated Hereford-cross heifers were used in a replicated 4×4 Latin square design with 21-d periods including 15 d of dietary adaptation and 6 d of data and sample collection. Dietary treatments included a control diet with 10.00% grass hay, 85.21% DRB, 4.51% of a vitamin and mineral supplement, and 0.28% of urea on a dry matter (DM) basis. Hybrid rye grain replaced 33, 67, or 100% of the DRB. Feed ingredients, feed refusals, ruminal pH, ruminal fluid, duodenal digesta, and fecal samples were collected from d 18 to 21 in each period. Data were analyzed using the Proc Glimmix procedure of SAS 9.4 (SAS Inst. Inc., Cary, NC) to evaluate the linear, quadratic, and cubic effects of increasing HR inclusion. Increasing HR inclusion as a substitute for DRB linearly decreased (P < 0.01) DM intake, linearly decreased mean pH (P < 0.01), and increased the duration (P < 0.01) and area (P = 0.02) that pH was <5.5. There were no effects of HR inclusion on total short chain fatty acid and lactic acid concentrations. Likewise, the molar proportions of acetate and butyrate were not affected by HR inclusion. Propionate was cubically affected by HR inclusion (P = 0.02). Ruminal ash-free neutral detergent fiber (aNDFom) digestibility linearly increased (P = 0.03) with increasing HR, but there was no effect on ruminal starch digestibility averaging 71.1% (SEM = 3.611). Increasing HR inclusion linearly increased intestinal DM digestibility (% of flow to the duodenum; P = 0.03), tended to linearly increase intestinal digestibility of organic matter (P = 0.08), and tended to quadratically affect intestinal digestibility of aNDFom (P = 0.07). Increasing hybrid rye linearly increased apparent total tract DM, organic matter, crude protein, aNDFom, and starch digestibility (P ≤ 0.05). In addition, increasing HR inclusion linearly increased GE digestibility (P < 0.01) and DE concentration (P < 0.01). Increasing the inclusion rate of HR grain as a substitute for DRB in finishing diets may decrease DMI and increase risk for low ruminal pH, which may be influenced by greater digestible energy concentration arising from greater DM, OM, aNDFom, and starch digestibility.

Production and use of dry-rolled hybrid rye grain as a replacement for barley grain on growth performance and carcass quality of feedlot steers.

The objectives were to compare cereal grain and straw yield between barley and hybrid rye (HR) and to evaluate whether the inclusion of dry-rolled HR grain as a replacement for barley grain affected feed intake and growth for growing cattle, and feed intake, growth, and carcass characteristics for finishing cattle. Crop yield was measured by directly weighing harvested grain and straw bales (n = 3 plots/grain type). Three-hundred sixty steers with an initial body weight (BW) of 348 ±â€…40 kg were stratified by BW and randomly assigned to 1 of the 24 pens during the growing phase (n = 8; 65 d). The control diet (BCON) included 60.22% barley grain with HR included by replacing 50 (BMID) or 100% (BHIGH) of the barley grain on a dry matter (DM) basis. Steers were re-randomized for the finishing phase (n = 6; 118 d) and treatments included a control diet containing 88.60% barley grain (FCON) with HR replacing 33 (FLOW), 67 (FMED), or 100% (FHIGH) of the barley grain (DM basis). The grain yield was greater (P = 0.04) and straw yield tended (P = 0.06) to be less for HR than barley. There were no effects of HR inclusion on DM intake (DMI) or G:F during the growing phase, but average daily gain (ADG) responded quadratically (P = 0.02) with cattle fed 50% HR having the greatest gain. During finishing, DMI decreased linearly as HR grain inclusion increased (P < 0.01). ADG initially increased from FCON to FLOW followed by a decrease with increasing HR inclusion (quadratic, P < 0.01), but G:F was not affected. Hot carcass weight was greatest for FCON with the magnitude of difference between FCON and the HR treatments increasing with increasing inclusion of HR (quadratic, P = 0.02). There was a linear increase in dressing percentage (P = 0.02) and a linear reduction in back fat thickness (P = 0.04) with increasing inclusion of HR. Increasing the inclusion of HR during finishing cubically (P < 0.01) affected the proportion of minor and severe liver abscesses with an average of 34.60% severely abscessed livers when HR was included compared to 11.11% for BCON. HR may have greater grain yield than barley, and partial replacement of barley grain with HR may improve ADG without affecting DMI or G:F during the growing phase. However, replacing barley grain in finishing diets with HR decreases DMI, and increases the risk of minor and severe liver abscesses, but does not affect feed conversion, suggesting HR should not replace more than 33% of the barley grain to maintain ADG.