Effect of maturity at harvest on yield, chemical composition, and in situ degradability for annual cereals used for swath grazing

Effect of dietary lipid inclusion from by-product-based pellets on dry matter intake, ruminal fermentation, and nutrient digestion in finishing beef heifers

This study was designed to evaluate dry matter intake (DMI), ruminal fermentation, ruminal digesta outflow, omasal flow of N constituents, and ruminal and total-tract digestibility in response to increasing dietary lipid content derived from high-lipid by-product-based pellets for finishing beef cattle. Five ruminally cannulated heifers were used in a 5 × 5 Latin square design. Dietary treatments were iso-nitrogenous with increasing ether extract (EE) concentrations resulting in dietary concentrations of 3.5%, 4.2%, 4.7%, 5.1%, and 5.9% of dry matter. Periods were 28 d in duration with the first 19 d used for dietary adaptation and the last 9 d for sample and data collection. Dry matter intake, ruminal pH, omasal flow of N constituents, and short-chain fatty acid concentrations were not affected by increasing dietary EE content (P ≥ 0.10). Increasing dietary EE content increased outflow of EE from the rumen (P < 0.001). Apparent ruminal and total-tract digestibility of EE increased linearly (P ≤ 0.03) with increasing dietary EE levels. Results indicate that increasing dietary EE content from 3.5% up to 5.9% of DM by including high-lipid by-product-based pellets does not alter site of nutrient digestibility with no negative effects on nutrient intake, ruminal fermentation, or apparent ruminal, and total-tract digestibility.

Use of barley silage or corn silage with dry-rolled barley, corn, or a blend of barley and corn on predicted nutrient total tract digestibility and growth performance of backgrounding steers

The objective of this study was to determine the effects of feeding barley silage (BS) or corn silage (CS) with dry-rolled barley (BG), dry-rolled corn (CG), or a blend of barley and corn grain (BCG), on growth performance and nutrient digestibility, the latter predicted using near-infrared spectroscopy for backgrounding cattle. Steers (n = 288) were stratified by body weight (BW) into 24 pens and pens were randomly assigned to one of six treatments (n = 4) in a 2 × 3 factorial design. Main factors included BS or CS in combination with BG, CG, or BCG. There were no silage × grain interactions. Dry matter intake (DMI; P = 0.018) and final BW (P = 0.004) were greater for steers fed CS than BS, but average daily gain (1.01 kg d−1) and gain-to-feed ratio (0.10 kg kg−1) were not affected by silage or grain source. Steers fed CS also had greater dry matter, organic matter, crude protein (CP), acid detergent fiber (ADF), starch, and gross energy digestibility values (P < 0.01) than BS. Feeding BG increased starch, neutral detergent fiber, ADF, and CP digestibility values (P ≤ 0.01) over CG and BCG. Relative to BS, feeding CS increased DMI, final BW, and nutrient digestibility, whereas dry-rolled BG improved nutrient digestibility when compared with CG and BCG in backgrounding diets.

In Vitro Assessment of Enteric Methane Emission Potential of Whole-Plant Barley, Oat, Triticale and Wheat

The study determined in vitro enteric methane (CH₄) emission potential of whole-plant cereal (WPC) forages in relationship to nutrient composition, degradability, and rumen fermentation. Two varieties of each WPC (barley, oat, triticale, and wheat) were harvested from two field replications in each of two locations in central Alberta, Canada, and an in vitro batch culture technique was used to characterize gas production (GP), fermentation, and degradability. Starch concentration (g/kg dry matter (DM)) was least (p < 0.001) for oat (147), greatest for wheat (274) and barley (229), and intermediate for triticale (194). The aNDF concentration was greater for oat versus the other cereals (531 vs. 421 g/kg DM, p < 0.01). The 48 h DM and aNDF degradabilities (DMD and aNDFD) differed (p < 0.001) among the WPCs. The DMD was greatest for barley, intermediate for wheat and triticale, and least for oat (719, 677, 663, and 566 g/kg DM, respectively). Cumulative CH₄ production (MP; mL) from 12 h to 48 h of incubation was less (p < 0.001) for oat than the other cereals, reflecting its lower DMD. However, CH₄ yield (MY; mg of CH₄/g DM degraded) of barley and oat grown at one location was less than that of wheat and triticale (28 vs. 31 mg CH₄/g DM degraded). Chemical composition failed to explain variation in MY (p = 0.35), but it explained 45% of the variation in MP (p = 0.02). Variation in the CH₄ emission potential of WPC was attributed to differences in DMD, aNDFD, and fermentation end-products (R² ≥ 0.88; p < 001). The results indicate that feeding whole-plant oat forage to ruminants may decrease CH₄ emissions, but animal performance may also be negatively affected due to lower degradability, whereas barley forage may ameliorate emissions without negative effects on animal performance.

Effect of stage of maturity at harvest for forage pea (Pisum sativum L.) on eating behavior, ruminal fermentation, and digestibility when fed as hay to yearling beef heifers

The objective of this study was to evaluate the stage of maturity at harvest for pea hay (Pisum sativum L., c.v. CDC Horizon) on dry matter intake (DMI), eating behavior, ruminal fermentation, and digestibility when fed to beef heifers. Pea hay was cut at EARLY (defined to occur when flat pods were on one or more nodes), MID (when seeds filled the pods at one or more nodes and the leaves were changing from green to gold), and LATE (yellow dry seeds filled pods on most or all of the nodes and the pods and leaves had a yellow color) phases, and was cured in the field and baled. Six ruminally-cannulated Speckle Park heifers were used in a replicated 3 × 3 Latin square design with three 18-d periods including 12 d for adaptation, 2 d for measurement of ruminal pool sizes, and 4 d for the collection of eating behavior, ruminal pH, ruminal digesta, and feces. For all treatments, the respective pea hay was included at 40% of the dietary DM. Stage of maturity at harvest for pea hay did not affect total DMI, pea hay DMI, or the total short-chain fatty acid concentration in ruminal fluid with averages of 8.6 kg/d, 3.2 kg/d, and 96.55 mM, respectively. The duration of time spent ruminating decreased with advancing pea hay maturity when reported as min/d, min/kg DMI, and min/kg neutral detergent fiber (NDF) (P ≤ 0.01). Mean ruminal pH also decreased with advancing pea maturity (P < 0.01). The ruminal DM and undigested NDF corrected for OM pools were not affected by stage of maturity (P ≥ 0.55) nor was the rate of digestion for NDF. However, NDF passage rate decreased by 0.21%/h with advancing pea hay maturity (P = 0.02). Apparent total tract digestibility of NDF (average = 16.30%, P = 0.41) was not affected, but starch digestibility decreased from 96.10% to 93.08% with advancing pea hay maturity (P = 0.07). Overall, stage of maturity at harvest for pea hay does not appear to affect DMI or NDF digestibililty but decreases chewing activity, apparent total tract starch digestibility, ruminal pH, and ruminal NDF passage rate.

Effect of feeding barley or corn silage with dry-rolled barley, corn, or a blend of barley and corn grain on rumen fermentation, total tract digestibility, and nitrogen balance for finishing beef heifers

Five ruminally cannulated heifers were used in an incomplete 6 × 6 Latin square design to determine the effects of cereal silage (barley vs. corn), cereal grain (barley vs. corn vs. a 50:50 blend of barley and corn), and their interaction (S × G) on dry matter intake, ruminal fermentation, total tract digestibility, nitrogen balance, and in situ degradation. Corn silage (CS) or barley silage (BS) was included at 8% of dietary dry matter (DM). Within each silage source, diets contained (DM basis) either dry-rolled barley (BG; 86%), dry-rolled corn (CG; 85%), or an equal blend of barley and corn (BLEND; 85%). Periods were 25 d, with 5 d of dietary transition, 13 d of dietary adaptation, and 7 d of data and sample collection. Samples collected included feed and refusals, total urine and feces, and ruminal fluid. All data were analyzed using the Mixed model of SAS with the fixed effects of silage, grain, and the S × G. Dry matter intake (P ≥ 0.19) and mean ruminal pH (P ≥ 0.096) were not affected by the silage, grain, or S × G. Total short-chain fatty acid concentrations were greater for BLEND than BG or CG (grain, P = 0.003) and for CS (silage, P = 0.009) relative to BS. The molar proportion of acetate was greater for BS-BG and BS-CG (S × G, P < 0.001), while molar proportion of propionate was greater for CS-BG (S × G, P < 0.001) relative to other silage and grain source combinations. Rumen ammonia-N concentration was greater for CG than BG, or BLEND (grain, P < 0.001), and greater for CS compared to BS (silage, P = 0.023). Apparent total tract digestibility of DM, organic matter, neutral detergent fiber, starch, and gross energy were greatest for BG (grain, P ≤ 0.035). Digestible energy content (Mcal/kg) was greater for BG (grain, P = 0.029) than CG and BLEND. Total nitrogen retention (g/d and % of intake) was greatest for CS-BG (S × G, P ≤ 0.033) relative to all other treatments. In situ degradation rates of DM, crude protein, and starch were greater for BG than CG (P ≤ 0.004). The potentially degradable fraction of DM, crude protein, and starch was greater for CG (P ≤ 0.031), while the undegradable fraction was greater for BG (P ≤ 0.046). For silage sources, CS had greater 24 h in situ DM digestibility (P = 0.009) and starch digestibility (24, 48, and 72 h incubations, P ≤ 0.034) relative to BS. Results suggest that while feeding a combination of CS and BG promotes propionate production and greater N retention; few other additive effects were observed.

Does pellet size affect the ability of beef heifers to consume a pelleted supplement in a simulated grazing model?

The objective was to evaluate pellet consumption and refusals as affected by pellet size. Six ruminally cannulated heifers were used in a replicated 3 × 3 Latin square. Heifers were individually housed and fed a diet of grass hay (57.5%), mineral and vitamin supplement (8.0%), and canola meal (11.9%) in a feed bunk, and their respective wheat- and wheat-middling-based treatment pellet (22.7%) on artificial turf. The artificial turf had a mean staple length of 5 cm and a blade density of 45 blades cm−2. The pellets were small (SM; 4 mm diameter), medium (MED; 11 mm diameter), or large (LG; 50 mm diameter) in size. Heifers fed LG had greater pellet intake than SM (2.24 vs. 2.06 kg; P = 0.035), with MED being intermediate (2.12 kg). Heifers fed LG tended to have less pellet waste than SM (P = 0.074). Heifers fed MED pellets had greater concentration of ruminal short-chain fatty acids than SM and LG (91.3 vs. 84.7 and 89.0 mmol L−1; P = 0.009). The results indicate that feeding a LG pellet may increase intake and reduce waste compared with SM, and that pellet size may also affect ruminal fermentation.

Effect of Harvest Time and Microbial Anaerobic Fermentation at Ruminal Degradability, In Vitro Digestibility to Milk Production and Milk Quality for Whole Plant Zhang Hybrid Millet in Dairy Cows

Simple Summary

With its drought tolerant and high productive characteristics, Zhang hybrid millet is becoming an important food source for both humans and animals. Whole plant Zhang hybrid millet has great potential in lowering feed cost while providing relatively high crude protein, vitamin, and mineral content. This study aimed to disclose whether harvest time and microbial anaerobic fermentation can improve ruminal degradability and intestinal digestibility of whole Zhang hybrid millet, and explore the effect of microbial anaerobic fermented whole Zhang hybrid millet as feedstuff on milk yield and milk quality. Results showed that the interaction effect of harvest time and microbial anaerobic fermentation had significant influence on the crude ash, Acid detergent fiber (ADF), water-soluble carbohydrate (WSC), and neutral detergent insoluble protein (NDIP) content and effective degradability of dry matter (EDDM) of whole Zhang hybrid millet. Early harvested whole Zhang hybrid millet with microbial anaerobic fermentation appeared to have a better chemical profile with lower content of crude ash, Neutral detergent fiber (NDF), ADF, and higher content of WSC, and a better ruminal degradability with lower EDDM, effective degradability of neutral crude protein EDCP, and effective degradability of neutral detergent fiber (EDNDF). Microbial anaerobic fermented whole Zhang hybrid millet as feedstuff did not significantly affect milk components, but significantly reduced somatic cell count ( SCC) compared with controls. Milk yield was numerically higher in whole Zhang hybrid millet groups. Collectively, harvest time and microbial anaerobic fermentation could further improve the nutritive value of whole Zhang hybrid millet. Microbial anaerobic fermented whole Zhang hybrid millet as an alternative feedstock for dairy diet was safe and feasible.

Abstract

This study assessed whether harvest time and microbial anaerobic fermentation could affect ruminal degradability and intestinal digestibility of whole Zhang hybrid millet, and estimate the effect of microbial anaerobic fermented whole Zhang hybrid millet as feedstuff on milk yield and milk quality. Protein degradation and intestinal digestion were determined using in situ nylon bag technique and three-step in vitro method, respectively. Results showed that harvest time, microbial anaerobic fermentation, or their interaction significantly affected EDDM, EDCP, and EDNDF (p < 0.05). In vitro fermentation was significantly influenced by harvest time. Early harvested samples appeared to have higher Total volatile fatty acid (TVFA) and lower acetate: propionate ratio than late harvested ones (p < 0.01). However, significant effect of harvest time and fermentation was failed to find in the estimation of rumen-undegradable protein (RUP) (p > 0.05). Microbial anaerobic fermented whole Zhang hybrid millet as feedstuff provided similar milk compositions compared with controls, and it significantly reduced SCC (p = 0.04). Milk yield was numerically higher in whole Zhang hybrid millet groups. In conclusion, harvest time and microbial anaerobic fermentation could further improve ruminal utilization of whole Zhang hybrid millet. Whole Zhang hybrid millet could be an alternative feedstock for dairy cows with acceptable safety profile and potential benefit in milk production.

Oversupplying metabolizable protein in late gestation for beef cattle: effects on prepartum BW, ruminal fermentation, nitrogen balance, and skeletal muscle catabolism

The objective of the study was to determine the effect of oversupplying MP during late gestation on maternal BW, ruminal fermentation, nitrogen balance, and skeletal muscle catabolism. Crossbred Hereford heifers (n = 24) were assigned to a control treatment designed to meet MP requirements (CON) or a treatment providing 133% of the MP requirement (HMP). Heifers were individually fed their treatment from day -55 ± 3 relative to parturition and DMI was summarized by week. BW was measured on day -55 ± 3, -41 ± 3, -27 ± 3, and -8 ± 3. Ruminal digesta samples were collected on day -34 ± 5 and -15 ± 4 for short-chain fatty acid and ammonia-N (NH3-N) concentration. Plasma was collected the day prior to ruminal digesta samples and analyzed for plasma urea-N. Nitrogen balance was measured over a 6-d period starting on day -34 ± 4 and -15 ± 4. Following completion of the N balance periods, muscle biopsies were collected from the longissimus dorsi and analyzed for abundance of proteins relating to skeletal muscle catabolism. Data were analyzed as a randomized complete block (date of parturition) design with repeated measures using the MIXED procedure of SAS. Heifers fed HMP increased conceptus-corrected BW by a greater magnitude than CON at day -8 relative to -55 and -41 (treatment × day, P < 0.01). DMI increased (P < 0.01) by 18% on week -2 compared to -8, but then decreased (P < 0.01) by 8.0% for week -1. N-intake, apparent N digestion, N excretion, and N retention (g/d) were all greater (P < 0.01) for HMP heifers than CON but did not differ when expressed as a proportion of N intake. Ruminal NH3-N decreased (treatment × day, P < 0.01) as parturition approached for HMP (10.1 to 8.6 mg/dL); whereas, NH3-N was not affected for CON (1.0 to 1.3 mg/dL). Consequently, plasma urea-N was greater (P < 0.01) for HMP heifers (15.0 vs. 7.5 mg/dL). Heifers fed HMP had improved (P < 0.01) DM, OM, and NDF digestibility relative to CON heifers. The abundance of calpastatin was greater (P = 0.03) and calpain tended to be greater (P = 0.085) for CON cows compared to HMP. Feeding greater quantities of MP during late gestation may improve ruminal fermentation, N balance, and improve BW gain prepartum.

High-fibre high-lipid by-product pellets containing calcium oxide-treated oat hulls as a partial replacement for barley grain in finishing diets for beef cattle

Two studies were conducted to evaluate the effects of treating oat hulls with calcium oxide (CaO) prior to inclusion in a high-lipid by-product pellet (HLP) on dry matter intake (DMI), ruminal fermentation, and total-tract digestibility (Study 1) and growth performance (Study 2). In Study 1, six ruminally cannulated heifers were used in a replicated 3 × 3 Latin square design. Study 2 used 210 steers in 21 pens in a 113 d finishing study. Dietary treatments for both studies included a barley-based control diet (CON), a diet where HLP partially replaced barley grain (NT-HLP), and a diet where HLP contained oat hulls treated with 7.5% CaO [dry matter (DM) basis; CaO-HLP]. For Study 1, DMI and ruminal pH were not affected. Apparent total-tract digestibility of DM and organic matter (OM) were greater (P < 0.05) for CON than NT-HLP and CaO-HLP. In Study 2, final body weight tended to be greater for NT-HLP and CaO-HLP than CON (P = 0.065). For CaO-HLP and NT-HLP, DMI was greater than CON (P < 0.01), but average daily gain (ADG) (2.0 kg d−1) and gain:feed (G:F) (0.16 kg kg−1) were not different. Thus, HLP can partially replace barley grain in finishing diets without negatively affecting ruminal fermentation or growth performance, but treatment with CaO has no effect.

Does the location of concentrate provision affect voluntary visits, and milk and milk component yield for cows in an automated milking system?

Eight Holstein cows were used in a cross-over design to test whether concentrate allocation in an automated milking system (AMS) affects dry matter intake (DMI) and milk production. Cows were fed a high-energy partial mixed ration (HE-PMR) with 0.5 kg of AMS concentrate or a low-energy PMR (LE-PMR) with 5.0 kg of AMS concentrate. The AMS concentrate intake was greater and PMR intake was reduced for LE-PMR than HE-PMR. Milk, fat, and protein yields were not affected by treatment. In a guided-traffic flow barn, providing a PMR with greater energy density increases DMI, but has no effect on milk and milk component yield.

Effect of variety and stage of maturity at harvest on nutrient and neutral detergent fiber digestibility of forage barley grown in western Canada

This study evaluated the effect of variety (V; CDC Cowboy, CDC Copeland, and Xena) and stage of harvest maturity (M; milk, early-, mid-, and hard-dough) on nutrient and neutral detergent fiber digestibility (NDFD) characteristics of barley forage using a randomized complete block design with 3 × 4 factorial treatment arrangement. Barley varieties had similar crude protein, but CDC Cowboy had greater (P < 0.01) acid detergent fiber (ADF), neutral detergent fiber (NDF), and lignin, and lower (P < 0.01) total digestible nutrient (TDN) content relative to Xena. Starch content of CDC Cowboy was lower (P < 0.01) than Xena at all stages of maturity with CDC Copeland intermediate at early- and mid-dough stages. Crude protein, ADF, NDF, and lignin content decreased (P < 0.01) while starch and TDN content increased (P < 0.01) with advancing maturity. Xena had greater (P < 0.01) NDFD, as determined by 6 h in vitro incubation using DaisyII system (NDFD6h), at milk, mid- and hard-dough stages of maturity than CDC Cowboy with CDC Copeland intermediate at mid-dough. However, CDC Cowboy had greater (P < 0.01) NDFD, as determined by 30 h in vitro incubation using DaisyII system (NDFD30h), at early-dough stage than Xena and greater NDFD30h at hard-dough stage than CDC Copeland. Xena had the lowest (P < 0.01) indigestible NDF based on 288 h ruminal in situ incubation (INDF288h), relative to CDC Copeland. These results indicate that to optimize NDFD30h, variety should be considered when deciding the timing of harvest.

Effect of dietary energy substrate and days on feed on apparent total tract digestibility, ruminal short-chain fatty acid absorption, acetate and glucose clearance, and insulin responsiveness in finishing feedlot cattle

The objective of this study was to determine the effect of dietary energy substrate and days on feed on apparent total tract digestibility, ruminal fermentation, short-chain fatty acid (SCFA) absorption, plasma glucose and acetate clearance rates, and insulin responsiveness. Eight ruminally cannulated, crossbred growing heifers were randomly allocated to 1 of 2 dietary treatments. The control (CON) diet consisted of 75.2% barley grain, 9.8% canola meal, 9% mineral and vitamin supplement, and 6% barley silage (DM basis). To evaluate the effect of energy source, a high-lipid, high-fiber byproduct pellet (HLHFP) was included in the diet by replacing 55% of the barley grain and 100% of canola meal. The study consisted of 4 consecutive 40-d periods (P1 to P4), with data and sample collection occurring in the last 12 d of each period. Dry matter intake tended ( = 0.10) to decrease by period and HLHFP-fed heifers tended to eat less ( = 0.09). The ADG of the CON was greater than that of the HLHFP during P1 and P4 (treatment × period, = 0.02). Heifers fed HLHFP tended to have greater mean ruminal pH (6.10 vs. 5.96; = 0.07) than heifers fed the CON, but pH was not affected by period. The CON heifers had a greater digestibility for DM, OM, CP, and NDF ( ≤ 0.03), and the digestibility for DM and OM linearly increased ( = 0.01) and for CP, NDF, and starch quadratically increased ( ≤ 0.04) with advancing period. Total SCFA concentration in the rumen was greater ( < 0.01) for the CON than for the HLHFP (141.6 vs. 128.1 m). The molar proportion of acetate and isobutyrate linearly increased and butyrate and valerate linearly decreased ( ≤ 0.05) with advancing periods. The rate of valerate absorption tended to increase (linear, = 0.06) and the ruminal liquid passage rate tended to decrease (linear, = 0.08) with advancing period. The arterial clearance rate of acetate tended to quadratically increase ( = 0.06) with period, whereas the clearance rate of glucose was not affected by treatment or period. Both fasting plasma insulin and the area under the insulin curve in response to glucose infusion linearly increased ( = 0.04) with period. These data suggest that partially replacing barley grain with HLHFP negatively affects total tract digestibility and performance. Moreover, with advancing days on feed, digestibility and insulin resistance increases without changes in ruminal pH and plasma metabolite clearance rates.

Defining risk for low reticuloruminal pH during the diet transition period in a commercial feedlot in western Canada

The objective of the current study was to measure reticuloruminal pH in cattle in a commercial feedlot setting to determine the incidence and extent of low reticuloruminal pH for steers and heifers as they transition to a high-concentrate finishing diet. Reticuloruminal pH was measured in 16 "mixed breed" steers (4 steers/pen with 4 pens) and 16 "mixed breed" heifers (4 heifers/pen with 4 pens) housed in commercial feedlot pens, with 227 ± 13 and 249 ± 6 cattle/pen cohort steers and heifers, respectively, for the diet transition period. Cattle were transitioned from a diet of 53.5% forage and 46.5% concentrate to a diet of 9.5% forage and 90.5% concentrate on a DM basis using a 40-d transition with 5 dietary steps with the diets containing 41.4, 44.8, 49.8, 52.5, 55.1, and 64.0% nonfibrous carbohydrate. In addition, wheat replaced barley as the grain source during the dietary transition. Reticuloruminal pH was measured using orally administered pH measurement devices that were retrieved at slaughter. Data were analyzed using a mixed model including the fixed effects of sex, diet, and the 2-way interaction to evaluate the effect of diet and sex and with the fixed effects of sex, diet, and day relative to each dietary change along with the 2- and 3-way interactions to evaluate temporal responses as a result of diet change. A repeated measures statement was included for the effect of day. Both the mean and minimum reticuloruminal pH values decreased as the proportion of concentrate in the diet increased ( < 0.001). The area and duration that pH was <5.6 increased with greater inclusion of concentrate in the diet ( < 0.001). The number of cattle experiencing low reticuloruminal pH, defined as pH < 5.6 for >180 min, increased with increasing concentrate, and by the end of the 40-d dietary transition, 83% of the cattle had experienced at least 1 bout of low reticuloruminal pH, with most experiencing between 1 and 3 bouts/diet. These data are interpreted to suggest that cattle are at high risk for experiencing low reticuloruminal pH during the dietary transition but that the extent of low reticuloruminal pH is mild. Moreover, the data suggest that the risk for low reticuloruminal pH increases with increasing proportion of concentrate in the diet. The results also suggest that susceptibility to low reticuloruminal pH may differ between steers and heifers.

Effect of including high-lipid by-product pellets in substitution for barley grain and canola meal in finishing diets for beef cattle on ruminal fermentation and nutrient digestibility

The objective was to determine the effect of replacing barley grain and canola meal with high-lipid by-product pellets (HLBP; 14.6% CP, 29.8% NDF, 9.0% fat, and 5.52 MJ NE/kg in DM) on DMI, ruminal fermentation, nutrient flow at the omasal canal, and nutrient digestibility. Four ruminally cannulated and ovariectomized Hereford × Gelbvieh heifers (initial BW of 631.9 ± 23.3 kg; mean ± SD) were used in a 4 × 4 Latin square design. Periods consisted of 28 d, including 10 d for diet transition, 11 d for dietary adaptation, and 7 d for measurements. Heifers were fed a typical finishing diet consisting of 89% of concentrate (barley grain and canola meal; CONT), 6% of barley silage, and 5% of mineral and vitamin supplement (on DM basis). Dietary treatments consisted of a CONT or diets where 30% (HLBP30), 60% (HLBP60), and 90% (HLBP90) of the barley grain and canola meal were replaced with HLBP. Dry matter intake was not affected by treatment ( > 0.10). Total short-chain fatty acid concentration and molar proportions of acetate, propionate, and butyrate ( > 0.10) among treatments and ruminal ammonia did not differ ( > 0.10) among treatments, and ruminal ammonia increased ( = 0.03) linearly with increasing HLBP inclusion rate in the diet. Mean and maximum pH increased, whereas the duration and area that pH was below 5.8, 5.5, and 5.2, thresholds used for mild, severe, and acute ruminal acidosis, respectively, decreased linearly ( ≤ 0.05) with increasing rates of inclusion of HLBP. Organic matter flow at the omasal canal increased linearly ( = 0.03) with increasing HLBP inclusion rate in the diet. However, OM digestibility coefficients and apparent ruminal NDF and ADF digestibility yielded negative values for some animals, especially those fed HLBP90, indicating that ruminal digestibility was underestimated. Total tract OM digestibility decreased linearly ( < 0.01) with increasing inclusion rates of HLBP. This study showed that HLBP inclusion in substitution for barley grain and canola meal linearly decreases the severity of ruminal acidosis in cattle fed a typical grain-based finishing diet. However, total tract nutrient digestibility was negatively affected.

Evaluation of a phase-feeding strategy utilizing high-lipid high-fibre byproduct pellets in diets for feedlot steers

Two studies were conducted to evaluate the provision of high-lipid high-fibre byproduct pellets when used as a partial replacement (60% in Study 1 and 30% in Study 2; HLP) for barley grain and canola meal in finishing diets (BAR). The HLP was fed for the last 49, 98, or 147 d (HLP49, HLP98, and HLP147, respectively) in Study 1, and for the last 60 or 120 d in Study 2 (HLP60 and HLP120, respectively) or the last 60 d with additional canola oil (HLP60CO). The statistical model included the fixed effects of diet, period, and the interaction. Steers fed BAR147 had the greatest average daily gain (ADG) (P < 0.01) and G:F (P = 0.01). The HLP147 had the greatest dry matter intake (DMI) during the first 49 d but least during the last 49 d of the finishing phase (treatment × period; P < 0.01). Hot carcass weight for BAR147 and HLP49 were the heaviest (P = 0.04). In Study 2, DMI and ADG were not affected (P > 0.05), but hot carcass weight was greater for BAR120 and HLP60 than HLP120 and HLP60CO. Inclusion of high-fibre high-lipid byproduct pellets in the latter part of the finishing period may improve carcass yield grade without affecting ADG and G:F.

Effect of maturity at harvest for whole-crop barley and oat on dry matter intake, sorting, and digestibility when fed to beef cattle

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.