Digestibility of western Canadian finishing beef cattle diets when short-season, high-moisture shelled corn and snaplage partially replace dry-rolled barley grain and barley silage

Abstract The objective of this study was to determine the effects of substituting barley grain with short-season, high-moisture shelled corn, and barley grain and barley silage with snaplage on ruminal fermentation and the site and extent of digestion in beef cattle fed finishing diets. Six ruminally and duodenally cannulated heifers (420 ± 16.4 kg body weight) were fed a barley grain and silage finishing diet (BG), a diet where half of the barley grain was replaced with high-moisture shelled corn (HC), or a diet where the barley silage and a portion of grain were replaced with snaplage (SN) in a replicated 3 × 3 Latin square design. While dry matter and starch intake were unaffected, feeding SN resulted in greater (P = 0.02) ruminal but not total tract starch digestibility than BG. Ruminal pH did not differ between HC and BG, but SN reduced (P = 0.02) minimum ruminal pH relative to BG. Feeding BG increased (P = 0.04) ruminal ammonia concentrations over HC. In conclusion, high-moisture shelled corn can partially replace barley grain with minimal impact on nutrient digestibility or ruminal fermentation, but replacement of barley silage and some barley grain with snaplage may increase the risk of ruminal acidosis.


Introduction
Corn production has increased 109% in the past 10 years in western Canada, with most being utilized for corn silage (Statistics Canada n.d.).Short-season corn varieties could be harvested for other high-moisture, more energy-dense products such as high-moisture shelled corn or snaplage for feedlot diets.Early frost is a concern when growing corn in western Canada, as frost can potentially terminate growth, resulting in a more immature corn crop that impacts the nutrient composition and digestibility of products (Aboagye et al. 2019;Horst et al. 2020).As corn matures, the proportion of kernel relative to the rest of the plant (stover) increases (Ferraretto et al. 2018).Regarding chemical composition, less mature plants are higher in crude protein (CP) and neutral detergent fiber (NDF) but have lower concentrations of starch than more mature plants, although the starch is more digestible (Bal et al. 1997).Therefore, we would expect an immature plant impacted by early frost to exhibit these characteristics.
High-moisture shelled corn consists of grain harvested with a combine at 68% to 75% kernel dry matter (DM), followed by rolling or grinding before ensiling (Seglar and Shaver 2014).Previous reviews summarizing studies conducted in warmer climates suggest high-moisture shelled corn has a greater rate of ruminal starch digestion when compared to dry-rolled barley grain (Huntington 1997) with similar metabolizable energy content (Owens et al. 1997).Corn generally has less CP than barley grain (NASEM 2016), although corn with growth terminated due to frost, as described above, as well as different hybrid varieties (Guyader et al. 2018), could differ in nutrient composition and digestibility.Alternatively, with a snapper header attached, a forage harvester can be used to remove and chop the ear of corn and process the kernels.The processed ear components can then be ensiled to create snaplage (Seglar and Shaver 2014).Because of the inclusion of the cob, husk, and shank as well as the grain, the NDF concentration of snaplage is typically greater than that of barley grain, but at the expense of starch suggesting that snaplage could be considered a highenergy forage source or a high-NDF grain source (NASEM 2016).Researchers have hypothesized that snaplage could be used as both an energy and roughage source in finishing cattle diets (Lardy and Anderson 2016;Godoi et al. 2021b), but we are unaware of peer-reviewed studies investigating the ‡ Dietary DM and nutrient composition were mathematically reconstituted from ingredient inclusion rate and the ingredient composition shown in Table 2. Limestone and urea were also included in diets but were not analyzed for nutrient composition.Limestone and urea DM were estimated as 99%.Limestone was estimated to contain 34.00% Ca, and urea was estimated to contain 281.0%crude protein.
§ Total digestible nutrients (TDN) were calculated using the equations of Weiss et al. (1992).Metabolizable energy (ME) was calculated using a conversion from 1 kg of TDN to 4.4 Mcal of digestible energy, then multiplying by 0.82 (NASEM 2016).Net energy for maintenance (NE m ) and net energy for gain (NE g ) were calculated using the equations based on ME (NASEM 2016).
replacement of barley grain and barley silage with snaplage in finishing diets.We hypothesized that partially replacing barley grain with high-moisture shelled corn from a short-season corn variety in finishing cattle diets would increase the extent of ruminal starch digestion and decrease mean ruminal pH while increasing the duration that ruminal pH is below 5.5.Additionally, completely replacing barley silage and a portion of the barley grain with snaplage would increase ruminal starch digestibility and the duration that ruminal pH is below 5.5 while decreasing mean ruminal pH and the extent of ruminal NDF digestibility.The objective of this study was to investigate the impact of replacing barley products with short-season, high-moisture shelled corn or snaplage in finishing cattle diets on ruminal fermentation and the site and extent of nutrient digestion.

Experimental design and dietary treatments
The experiment was designed as a replicated 3 × 3 Latin square balanced for carry-over and sequence effects by having differing treatment sequences in each square.Each period of the Latin square consisted of 25 days, allowing for 6 days of diet transition from the previous diet, 14 days of diet adaptation, and 5 days for data and sample collection.Dietary treatments (Table 1) were formulated to be isonitrogenous and to contain the same inclusion rates for limestone and the mineral and vitamin supplement.The supplement was manufactured in one batch (Canadian Feed Research Centre, North Battleford, SK, Canada) and included 45.8% ground wheat, 27.3% ground limestone, 9.1% dried molasses, 7.0% urea, 4.1% magnesium carbonate, 2.7% salt, 1.4% porcine tallow, 1.4% dicalcium phosphate, and less than 1.0% copper oxide, manganese oxide, zinc oxide, selenium yeast (SelenoSource AF † Total digestible nutrients (TDN) were calculated using the equations of Weiss et al. (1992).Metabolizable energy (ME) was calculated using a conversion from 1 kg of TDN to 4.4 Mcal of digestible energy, and then multiplying by 0.82 (NASEM 2016).Net energy for maintenance (NE m ) and net energy for gain (NE g ) were calculated using the equations based on ME (NASEM 2016).2000; Diamond V, Cedar Rapids, IA, USA), ethylenediamine dihydriodide, vitamin ADE blend, vitamin A, vitamin E, and monensin (Rumensin Premix; Elanco Canada Ltd., Guelph, ON, Canada) on a DM basis to provide 44 mg/kg Fe, 14 mg/kg Zn, 12.2 mg/kg Cu, 2.9 mg/kg Mn, 0.15 mg/kg I, 0.04 mg/kg Se, 0.01 mg/kg Co, 1635 IU/kg vitamin A, 265 IU/kg vitamin D, 42 IU/kg vitamin E, and 33 mg/kg monensin of diet DM.All diets were formulated to meet or exceed the energy, protein, vitamin, and mineral requirements of finishing heifers with an initial body weight (BW) of 435 kg, a final BW of 650 kg, a projected rate of gain of 1.9 kg/d, and an estimated DM intake of 8 kg/day as recommended by NASEM (2016).In addition to the limestone and mineral and vitamin supplements, the control diet (BG) contained barley grain that was dry rolled to a 65% processing index (PI), barley silage, and urea.The PI was measured by weighing 0.5 L samples of whole barley grain and 0.5 L samples of processed grain.The weight of the processed grain was divided by the weight of the original whole grain to determine the PI on an as-is basis (Beauchemin et al. 2001).The high-moisture shelled corn and snaplage used in this study were grown from a short-season hybrid seed (dent variety adapted to 2050 corn heat units, P7202AM; Pioneer brand Seeds, Corteva Agriscience, Saskatoon, SK, Canada) and harvested in November 2019.The first killing frost was on October 9, 2019, with a temperature of −6.3 • C. High-moisture shelled corn processed to a PI of 65% replaced 50% of the barley grain, relative to the BG treatment, for the high-moisture shelled corn treatment (HC).As the proportion of barley silage did not change, there was no attempt to balance NDF or starch when comparing BG and HC.Snaplage replaced 100% of the barley silage and 12.5% of the barley grain from the BG diet in the snaplage treatment (SN).The snaplage inclusion level was designed to maintain the NDF concentration of the diet when replacing barley silage and barley grain (Table 2).Urea was included or removed to help maintain dietary CP.

Animal management and facilities
Six Hereford × Angus × Charolais-cross beef heifers (average 420 ± 16.4 kg BW) were purchased from a local producer (Oleksyn Bros., Prince Albert, SK, Canada) and surgically fit with a 7.5 cm diameter, soft plastisol ruminal cannula (Bar Diamond Inc., Parma, ID, USA), and a custom-made closed T-shaped, stainless-steel duodenal cannula (University of Saskatchewan, Saskatoon, SK, Canada) based off of the design by Raggio et al. (2006) but shrunk in size by 20%.The intestinal cannula was placed 10 cm distal to the pylorus and proximal to the bile and pancreatic ducts by a trained surgeon (Department of Large Animal Clinical Sciences, Western College of Veterinary Medicine, Saskatoon, SK, Canada).After 2 weeks, the 7.5 cm diameter ruminal cannula was replaced with a 10 cm diameter cannula (Bar Diamond Inc.).Heifers were trained to be tethered, treated for parasites (Cyfluthrin, 0.26 μg/kg BW; CyLence Pour-On Insecticide, Elanco Canada Ltd., Guelph, ON, Canada), had body and tail hair clipped, and were transitioned to a highgrain diet before the start of the study.Before transition, heifers were fed a diet consisting of 10.0% barley grain, 88.2% barley silage, and 1.9% mineral and vitamin supplements on a DM basis.The first step during transition contained 25.0% barley grain, 73.2% chopped hay, and 1.9% mineral and vitamin supplements on a DM basis.Barley grain DM inclusion was increased at the expense of chopped hay over 5 steps over 20 d (25.0%, 40.0%, 55.0%, 70.0%, and 80.0% of DM) to reach a common finishing diet, BG, 2 days before starting the diet transition to experimental diets in period 1.Each heifer was housed in an individual tie stall (3.14 m 2 ) equipped with a water-filled, rubber mattress, an individual feed bunk, an automatic pressure-activated water bowl, and a 25.4 cm rubber ball on a rope (Jolly Pets, Streetsboro, OH, USA) for enrichment.Heifers could see each other, but physical contact was not possible.Minimal amounts of wood-shaving bedding were provided for additional comfort.Environmental temperature and humidity were maintained using water misters and cooling fans within the barn.Florescent lighting was timer-controlled and mimicked diurnal patterns, resulting in 15 h of light (0600 to 2100 h) and 9 h of darkness.Stalls were washed daily before feeding, and animals were allowed 2 h of exercise in a common outdoor pen when weather and sample collections permitted.Heifer BW was measured on two consecutive days prior to feeding at the beginning of each period.The average of these weights determined the initial feed offered on day 1 of each period.

Feeding management
Heifers were fed experimental diets (starting at 2.2% of BW as fed) to achieve ad libitum intake once daily at 1000 h.Refusals were measured daily to adjust feed delivery amounts to target 5% refusals on an as-fed basis.The amount of feed offered was increased or decreased by 0.5 kg (as fed) when refusals were less than 4.0% or greater than 7.5% of delivery, respectively, for two consecutive days.Refusals during the sampling period averaged 16.1 ± 15.02% relative to the amount of feed offered (as-is basis) with refusals during noncollection periods averaging 6.2 ± 9.56% of the feed offered.Barley grain and the mineral supplement were sampled once weekly, and high-moisture shelled corn, snaplage, and barley silage were sampled twice weekly for DM content.Each ingredient was sourced from a single lot over the duration of the experiment.

Dry matter intake and diet digestibility
External solid and liquid phase digesta markers, YbCl 3 (Siddons et al. 1985) and Cr-ethylenediaminetetraacetic acid (Udén et al. 1980) respectively, were infused directly into the rumen using a peristaltic pump (Watson and Marlow 205U; Watson and Marlow, Cornwall, UK) targeting a rate of 1 L/day to supply 2.8 g/day Yb and 2.8 g/day Cr.Infusions were initiated on day 19 following a 500 mL pulse dose to ensure steadystate conditions within the rumen.Solution containers were weighed daily to monitor infusion rates.A subsample (50 mL) of each infusate was collected from each period and batch and frozen at 20 • C for later analysis.
From day 21 through day 25, feed ingredients and feed refusals were sampled daily.From day 22 through day 25, whole duodenal digesta samples (300 g) were collected every 12 h within a day and every 15 h across days, resulting in eight samples representing every 3 h of a 24 h cycle over the 4-day sampling period.Samples of duodenal digesta were collected by diverting the passing digesta into plastic graduated cylinders using spatulas.Fecal samples (200 g) were collected at the same time as duodenal digesta sampling by directly stim-ulating the rectum.Feed ingredients were composited by ingredient within the period, and refusal, duodenal, and fecal samples were composited by animal within the period on an equal weight basis before drying.All samples were stored at −20 • C until analysis.
Ingredient, refusal, duodenal, and fecal samples were dried in a forced-air oven at 55 • C for 7 days, and ground through a 1 mm screen (Retsch ZM 200, Haan, Germany).DM content was calculated based on the difference between the weight of the sample before and after drying, and that value was divided by the original weight expressed as a percentage.Samples were analyzed for CP, NDF, ash, ether extract, starch, Ca, and P according to the methods described by Rosser et al. (2013) by Cumberland Valley Analytical Services (CVAS; Waynesboro, PA, USA), except the ash procedure used 1.5 g sample weight, 4 h ash time, and residues were weighed before cooling.Organic matter (OM) was calculated as 100 − ash content on a DM basis.Total digestible nutrients were calculated using the equations of Weiss et al. (1992).Metabolizable energy was calculated using a conversion from 1 kg of total digestible nutrients to 4.4 Mcal of digestible energy, subsequently multiplied by 0.82 (NASEM 2016).Net energy for maintenance and net energy for gain were calculated using the equations based on metabolizable energy (NASEM 2016).Diets were mathematically reconstituted by period by using the proportional inclusion of nutrients corresponding to the ingredient proportion in the formulated diet.Nutrient intake was determined as nutrient refused subtracted from nutrient fed.All nutrients were expressed on a DM basis and used to determine ruminal, intestinal, and apparent total tract digestibility.
Infusion solution, duodenal, and fecal samples were analyzed for Yb and Cr concentrations.Duodenal and fecal samples were digested using the methods of Lopez Molinero et al. (1988), where 1 mL of infusate was added to 15 mL of 1.5 mol/L HNO 3 with 2 g/L KCl and then diluted to 50 mL with double-distilled water.Digested samples were analyzed for Yb using flame atomic absorption spectroscopy (iCE 3000 series; Thermo Fisher Scientific Inc., Waltham, MA, USA) and for Cr using inductively coupled plasma mass spectrometry (Prairie Diagnostic Services, Saskatoon, SK, Canada).Marker dysfunction occurred for both Yb and Cr in duodenal samples, resulting in negative ruminal digestibility for all nutrients.As a result, to estimate duodenal flow, fecal output, and extent of digestibility, all feed, refusal, duodenal, and fecal samples were analyzed for the concentration of acid detergent lignin (ADL) by CVAS using the procedure described by Goering and Van Soest (1970) modified in the acid detergent fiber step using method 973.18 (AOAC 2000) with Whatman 934-AH glass microfiber filters with 1.5 μm particle retention (Cytiva, Marlborough, MA, USA) instead of fritted glass crucibles.
Apparent total tract digestibility of DM, OM, CP, ether extract, aNDFom, and starch were calculated as follows: 100-100 × ([ADL intake/ADL in feces] × [nutrient concentration in feces/nutrient concentration intake]), as described by Ovinge et al. (2018).Ruminal digestibility was calculated similarly using ADL and nutrient concentrations in the duodenum rather than the feces.The apparent total tract and ruminal di-gestibility were expressed as a percentage of DM intake.Duodenal flow of DM (DF) was calculated as follows: grams of ADL consumed/ADL concentration in the duodenum.The fecal output of DM was calculated in the same manner, except that the ADL concentration in feces was substituted for the ADL concentration in the duodenal digesta.Intestinal digestibility of a nutrient was calculated as follows: ((DF × nutrient concentration in duodenum) − (fecal output of DM × nutrient concentration in feces))/(DF × nutrient concentration in duodenum) and is expressed as a percentage of DF.

Ruminal fermentation parameters
Indwelling ruminal pH meters (Dascor, Escondido, CA, USA) were inserted into the ventral sac (Penner et al. 2006) on day 18, and ruminal pH was measured every 5 min from day 21 through day 24 of each period.Methods of standardization and threshold evaluation at pH 5.5 and 5.2 are described by Joy et al. (2021) and Penner et al. (2007), respectively.Duration below the threshold was calculated as the sum of the number of incidences multiplied by 5 min and divided by 60 min/h.The area under the threshold was calculated as the sum of the pH of each incidence subtracted from the threshold multiplied by the number of minutes under the threshold.Both duration and area were averaged over 4 days for each animal by period.Ruminal digesta samples (750 mL) were obtained from the caudal ventral, central, and cranial dorsal sacs at 0, 2, 4, 8, 12, and 24 h after feeding on day 21 and day 22.Contents were strained through two layers of cheesecloth, and two 10 mL subsamples of ruminal fluid were mixed with 2 mL of 1% (v/v) H 2 SO 4 for determination of NH 3 -N or 25% (w/v) metaphosphoric acid for determination of short-chain fatty acids (SCFA).Samples were stored at −20 • C until analysis.Ammonia concentrations were analyzed by a phenolhypochlorite assay (Broderick and Kang 1980) modified for a plate reader.Concentrations of SCFA were determined using gas chromatography (Agilent 6890, Mississauga, ON, Canada) according to the methods of Khorasani et al. (1996).

Statistical analysis
Data were analyzed using the MIXED procedure of SAS version 9.4 (SAS Institute, Cary, NC, USA) as a replicated 3 × 3 Latin square design.The fixed effects of the model included treatment, and the random effects included square, animal within square, and period.Denominator degrees of freedom were calculated using Satterthwaite approximation, and data were checked for normality using the Shapiro-Wilk test for normality.Repeated measures were applied to ruminal pH, SCFA, and ammonia concentrations, and the effect of time (h) and its interactions with treatment were also tested as fixed effects.Covariance structures were determined using the lowest Bayesian information criterion.No treatment × h responses were detected, and h effects were considered to have limited novelty, so only treatment means were reported.Contrast P-values comparing the means of BG with HC and BG with SN were presented, along with the largest SEM.Means were declared different when P ≤ 0.05, and tendencies were considered when 0.05 < P ≤ 0.10.

Results
Daily intakes (Table 3) of DM and OM did not differ between cattle fed BG and HC or BG and SN.Heifers fed SN tended to have greater (P ≤ 0.09) CP, NDF, and starch intake than those fed BG, but ether extract intake did not differ.When fed HC, heifers had a greater (P < 0.01) ether extract intake than heifers fed BG, but no differences were detected in CP, NDF, and starch intake.
There were no differences in the flow of nutrients to the duodenum for cattle fed BG compared to HC.The daily flow of NDF to the duodenum tended to be greater (P = 0.09) for SNfed cattle than BG-fed cattle, but the flow of other nutrients did not differ.Ruminal digestion of OM was greater (P < 0.01) for heifers fed HC than BG but did not differ for DM, CP, ether extract, NDF or starch.Heifers fed SN had greater (P ≤ 0.02) ruminal OM and starch digestibility than those fed BG.No differences were observed when comparing BG and HC for intestinal digestion of nutrients, while those fed SN tended to have lesser (P ≤ 0.10) intestinal digestibility of OM and starch as a percentage of the flow to the duodenum than those fed BG.Regarding apparent total tract digestibility, there were no differences for SN or HC relative to BG for DM, OM, CP, or starch digestibility.However, cattle fed SN and those fed HC had greater (P ≤ 0.05) ether extract digestibility than cattle fed BG, and cattle fed HC tended to have lesser (P = 0.06) NDF digestibility than those fed BG.
Mean and maximum ruminal pH did not differ (Table 4) between cattle fed BG and HC or SN, but cattle fed SN had a lower (P = 0.02) minimal ruminal pH than those fed BG.There were no differences detected between BG and HC or SN for duration that ruminal pH was below 5.2 or area that ruminal pH was below 5.2 or 5.5, but heifers fed SN tended to have a greater (P = 0.10) duration that ruminal pH was below 5.5 than those fed BG.
Heifers fed BG had greater (P = 0.04; Table 5) ruminal ammonia concentrations than those fed HC, but ruminal ammonia concentrations did not differ between BG and SN.There were no differences in total ruminal SCFA concentration, the molar proportions of individual SCFA, or the acetate: propionate ratio between heifers fed BG and HC or SN.

Discussion
It is important to note that the high-moisture corn products used in this study had greater protein content and lower starch content than average high-moisture shelled corn and snaplage (NASEM 2016).Short-season growing conditions coupled with a killing frost likely led to incomplete maturation and are the most likely reasons for the numerically greater CP and lesser starch (Horst et al. 2020).We are unaware of other research evaluating the use of high-moisture shelled corn or snaplage with short-season corn.However, research evaluating short-season corn silage (Johnson et al. 2020) or grain from short-season corn silage (Miorin et al. 2018) has reported similar trends of higher CP and lower starch content in short-season products relative to average values in NASEM (2016).

Replacing barley grain with high-moisture shelled corn
In this study, the hypothesis that partially replacing barley grain with short-season, high-moisture shelled corn in a finishing diet would negatively impact ruminal pH or increase ruminal starch digestion was not supported.In fact, we did not observe differences in the site or extent of starch digestion, and there were no differences in ruminal pH despite similar dry matter intake (DMI) between treatments.This may indicate that high-moisture shelled corn from shortseason corn can replace 50% of the barley grain without adverse effects on nutrient digestion or ruminal pH.However, it should be noted that DMI was lower than expected (NASEM 2016) without any clear cause for the low DMI.Other researchers have observed that intestinally cannulated cattle have lower DMI than predicted by intake models (Titgemeyer 1997;Koenig et al. 2004;Koenig and Beauchemin 2013).Additionally, it is possible that individual housing and lack of socialization during sampling times may have decreased DMI due to the absence of social facilitation from herd members (Broom and Fraiser 2007), as evident by numerically larger refusal rates during sampling times.
The hypothesis for this study was constructed on the basis that early termination of plant maturity would yield  corn with readily available starch and that ensiling may increase the rate of fermentation.As noted above, the maturation of high-moisture shelled corn used in this study was most likely arrested early due to frost preventing the maturity-dependent increases in starch accumulation, reductions in moisture, and reduced ruminal starch digestibility caused by increasing zein protein accumulation (Ahmed et al. 2014).Grinding and ensiling of high-moisture shelled corn increases both the rate and extent of ruminal starch fermentation compared to only mechanical processing of corn (Owens et al. 1997) and was anticipated to lead to greater rates of digestion when compared to dry-rolled barley.As starch intake, ruminal starch digestibility, ruminal pH, and ruminal SCFA concentrations did not differ, we speculate that the high-moisture shelled corn and barley grains may have had similar rates of ruminal starch digestion.While variance in our estimates of ruminal digestion approximated 17.8% of the average of the means, past studies have reported similar magnitudes of variation (Beauchemin et al. 2001(Beauchemin et al. , 2003)), and this could be expected given the use of a single passage flow marker (Owens and Hanson 1992).It may be possible that the aggressive degree of processing for barley (65% PI) to ensure adequate cereal grain processing (Jancewicz et al. 2017) led to the lack of differences.In fact, we observed ruminal, intestinal, and total tract starch digestibility of 81.95% and 82.93%, 92.68% and 92.67%, and 98.7% and 98.8% for the BG and HC treatments, respectively.Previous studies evaluating the ruminal starch digestibility of dry-rolled barley have utilized a PI as low as 67% (Wang et al. 2003), but most have utilized a PI no lower than 75% (Zhao et al. 2015(Zhao et al. , 2016;;Chibisa et al. 2020).A field-based study evaluating the PI of barley and its relation to fecal starch and gain-to-feed (G:F) reported a positive relationship among PI and fecal starch concentration and a negative relationship with G:F, suggesting a PI of 65% may be required for adequate starch utilization (Jancewicz et al. 2017).Other studies have also reported that increasing the degree of processing of barley has been shown to increase starch digestion (Beauchemin et al. 2001;Koenig et al. 2003).Also, it is possible that substituting a greater degree of processed high-moisture shelled corn for barley rolled to a lesser PI (e.g., 65% PI versus 75% PI, respectively) could adversely affect ruminal pH in comparison but may increase ruminal starch digestion (Dehghan-banadaky et al. 2007).Therefore, it is unclear how the maturation and degree of processing of short-season corn for high-moisture shelled corn would affect ruminal starch fermentation and total tract starch digestibility, and is an area for further research.
In this study, diets were formulated to be isonitrogenous with the addition of urea where needed.Because of the high protein content of the high-moisture shelled corn used, the addition of urea was necessary for the BG diet.Dietary urea addition most likely contributed to the greater ruminal ammonia concentrations in heifers fed the BG treatment over the HC treatment (NASEM 2016).Additionally, by study design, the HC diet contained greater amounts of ether extract due to the inclusion of high-moisture shelled corn, increasing ether extract intake.Linoleic acid (18:2n-6) is a major contributor to the fatty acid composition of short-season corn and is more abundant in corn than barley grain on a mg/g DM basis (Vahmani et al. 2021).Provision of additional 18:2n-6 could lead to more extensive biohydrogenation of 18:2n-6 (Doreau and Ferlay 1994).It is likely, given the lower ruminal pH and increased passage rates seen in finishing cattle, that a portion of 18:2n-6 is not completely biohydrogenated to 18:0 when it reaches the small intestine.Partially hydrogenated 18:1 isomers will form micelles more rapidly than completely saturated 18:0, increasing the rate of uptake by epithelial cells (Doreau and Ferlay 1994).This may help to explain the increased total tract ether extract digestibility with HC over BG.

Replacing barley silage and barley grain with snaplage
Most peer-reviewed in vivo snaplage research has been focused on dairy cattle starch digestion and lactation performance (Evans et al. 2013;Akins and Shaver 2014;Ferraretto et al. 2018), but recently, snaplage has garnered interest as a roughage and energy ingredient in Brazilian finishing diets (Daniel et al. 2019;Salvo et al. 2020;Godoi et al. 2021aGodoi et al. , 2021b;;Gusmão et al. 2021).Otherwise, data on snaplage for beef cattle has been limited to conference papers and extension reports (Akins et al. 2014;Lardy and Anderson 2016;Stateler 2018;Rusche 2020).This highlights the limited information available concerning snaplage under North American finishing conditions.
Considerations of both the grain and roughage properties of snaplage need to be assessed when including it in finishing diets.In this experiment, when replacing barley products with snaplage, the concentrations of starch, NDF, and CP were the main nutrients that were balanced among treatments.Snaplage has a greater concentration of starch and a lesser concentration of NDF than traditional corn silage because of the greater proportion of grain relative to other plant parts (Lardy and Anderson 2016).Snaplage is also greater in NDF compared with high-moisture shelled corn and barley grain due to the inclusion of the shank, husk, and cob but has lower concentrations of starch (Akins and Shaver 2014;NASEM 2016) Others have reported greater in vitro starch digestibility of snaplage over high-moisture shelled corn, attributing it to greater moisture content in snaplage, enabling more extensive fermentation during ensiling by increasing protease activity, resulting in the release of starch from the zein protein matrix in the kernel endosperm (Akins and Shaver 2014).When compared to other corn grain products as well as many barley products, snaplage is often lower in CP, so the addition of other protein sources to meet nutrient requirements, such as urea used in this study, needs to be considered (Lardy and Anderson 2016).
While this study did not confirm our hypothesis that replacing barley silage and a portion of barley grain with snaplage would decrease mean ruminal pH and the extent of ruminal NDF digestibility, we did confirm that snaplage, when substituted for barley silage and some of the barley grain, increased ruminal starch digestibility and decreased minimal ruminal pH.Our results indicate that the replacement of barley silage and some barley grain with snaplage increases ruminal starch digestion but also decreases minimal ruminal pH.It is surprising that the minimum pH was lower, but there were no differences in the duration or area below 5.5 or 5.2.In some studies, cattle preferentially sort feed to attenuate ruminal acidosis (DeVries et al. 2008(DeVries et al. , 2014)).Sorting behavior was not directly measured in this study, but heifers consuming snaplage tended to have greater NDF intake and duodenal flow than those consuming BG, even though both diets were balanced for NDF composition.When faced with low ruminal pH, heifers on SN may have selected fibrous components as a behavioral strategy to mitigate the duration and area that ruminal pH was below pH 5.5 and 5.2.
The reduction in minimum ruminal pH can be attributed to a reduction in physically effective NDF (peNDF) or undigestible NDF (uNDF; Spowart et al. 2022) or, more likely, increased ruminal starch digestion (Wiese et al. 2017).While not measured in this study, balancing finishing rations for peNDF (Mertens 1997) or uNDF (Ran et al. 2021) may be useful to attenuate the effects of acidosis by stimulating rumination or promoting ruminal motility and SCFA absorption.Therefore, future research into the fiber components of snaplage when used in finishing diets should include these measurements.Despite our lack of information about peNDF and uNDF, the increased NDF intake exhibited by SN heifers supports the suggestion that the 5.22% increase in starch digestibility over BG-fed heifers was most likely the driver of decreased minimal ruminal pH (DeVries et al. 2014).Previous researchers have shown that prolonged ruminal acidosis can negatively impact finishing cattle performance (Castillo-Lopez et al. 2014) as well as increase the risk of liver abscesses (Nagaraja and Lechtenberg 2007).Further investigation into the impact of barley silage and barley grain replacement with snaplage on feedlot performance and liver abscess prevalence and severity is of interest.
Contrary to our hypothesis, decreases in ruminal NDF digestibility were not observed.Subacute ruminal acidosis decreases in situ NDF ruminal digestibility in dairy cows (Krajcarski-Hunt et al. 2002), but the effect has not been replicated consistently in finishing cattle (Beauchemin et al. 2001(Beauchemin et al. , 2003;;Warner et al. 2020), most likely due to the smaller inclusion of NDF in finishing diets and increased passage rate of digesta to the small intestine (Voelker Linton and Allen 2007).The generally low ruminal pH of cattle in this study may have partially inhibited microbial attachment, limiting the detection of differences in NDF ruminal digestion (Sung et al. 2007).
In conclusion, this research indicates high-moisture shelled corn can replace 50% of the dry-rolled barley grain in finishing diets with no effects on the extent and site of starch digestion or ruminal pH.Additionally, when snaplage completely replaces barley silage and a portion of dry-rolled barley grain, more starch is degraded in the rumen, leading to a decreased minimal ruminal pH.Research into the effect of using snaplage as a substitute for barley grain and silage on digesta passage rate is warranted to further clarify NDF digestibility responses.

Table 1 .
Diet composition and nutrient concentrations of treatment diets fed to heifers * .

Table 2 .
Analyzed dry matter (DM) and nutrient concentrations of ingredients included in treatment diets fed to finishing heifers.

Table 3 .
Intake, duodenal flow, and nutrient digestibility of heifers fed a finishing diet consisting of barley grain or high-moisture corn and barley silage or snaplage * .Treatments consisted of diets with dry-rolled barley grain and barley silage (BG), dry-rolled barley grain and snaplage (SN), and dry-rolled barley grain, high-moisture corn, and barley silage (HC). *

Table 4 .
Ruminal pH of heifers fed a barley-based or high-moisture corn product-based finishing diet * .Treatments consisted of diets with dry-rolled barley grain and barley silage (BG), dry-rolled barley grain and snaplage (SN), and dry-rolled barley grain, high-moisture corn, and barley silage (HC). *

Table 5 .
Ruminal ammonia and short-chain fatty acid (SCFA) concentrations of heifers fed a barley-based or high-moisture corn product-based finishing diet * .Treatments consisted of diets with dry-rolled barley grain and barley silage (BG), dry-rolled barley grain and snaplage (SN), and dry-rolled barley grain, high-moisture corn, and barley silage (HC).