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Objective The objective was to examine the effects of feeding teff (cv. Moxie) hay harvested at either the early-heading (EH) or late-heading (LH) stage of maturity on nutrient intake and digestibility, ruminal fermentation characteristics, and growth performance in backgrounding cattle. Materials and Methods A total of 114 steers (initial BW ± SD = 258 kg ± 19.4) were used in a completely randomized design. The dietary treatments were backgrounding diets containing either EH or LH teff hay (65% of diet DM) as the only source of forage. Steers were fed over a 56-d period. Body weight was measured at the beginning and end of the trial, with ruminal fluid, fecal, and blood samples collected on d 21, 42, and 56 to quantify metabolites. Results and Discussion Dry matter and nitrogen (N) intake and apparent total-tract digestibility were greater for EH than LH steers. Although greater for steers fed the EH than LH teff diet on d 21 and 42, both total ruminal short-chain fatty acid and ammonia-N (NH3-N) concentrations did not differ across diets on d 56. These observations suggest greater nutrient supply for EH than LH steers, possibly accounting for the greater ADG. Implications and Applications Delaying harvest of teff from the EH to LH stage of maturity compromised DM and N intake and apparent total-tract digestibility, and ADG. Therefore, the stage of maturity at harvest must be considered when developing teff (cv. Moxie) grass-based feeding systems for growing calves.

Because of its high crude protein (CP) content, dietary inclusion of corn dried distillers’ grains with solubles (DDGS) in finishing cattle diets can increase the ruminal loss of ammonia-nitrogen (NH3-N), which ends up excreted as urine urea-N (UUN). Increasing dietary fermentable energy supply can enhance ruminal use of N; however, it could also lead to acidotic conditions that compromise digestive function and animal performance. We evaluated the effects of partially replacing dietary corn grain with 20% or 40% (dry matter [DM] basis) wheat grain in finishing diets containing 15% corn DDGS on N utilization, ruminal pH, and digestive function. Nutrient intake and digestion, ruminal fermentation characteristics, microbial protein synthesis, route of N excretion, and blood metabolites were measured. Six ruminally fistulated crossbred beef heifers (initial body weight ± SD; 797 ± 58.8 kg) were used in a replicated 3 × 3 Latin square design with 28-d periods. Dietary treatments were either corn (73% of diet DM; CON), 53:20 corn:wheat blend (20W), or 33:40 corn:wheat blend (40W) as the major fermentable energy source. Dry matter intake (DMI) tended to be lower for heifers fed the 40W than CON and 20W diets. Feeding diets containing wheat grain led to an increase (P = 0.04) in neutral detergent fiber (NDF) intake. However, there was no diet effect (P ≥ 0.60) on apparent total tract DM and NDF digestibility. Feeding wheat grain led to a decrease (P ≤ 0.03) in mean and minimum pH, an increase (P = 0.04) in pH < 5.8 duration, and a tendency for an increase in the area and acidosis index for pH < 5.8 and 5.5. Nitrogen intake, which was lower (P = 0.04) for 40W than 20W heifers did not differ between CON and 20W heifers. There was no diet effect (P = 0.80) on ruminal NH3-N concentration and estimated microbial N flow. However, feeding diets containing wheat grain led to a decrease (P = 0.045) in UUN excretion (% total urine N). Fecal and total N excretion (% of N intake) increased (P < 0.01) following the addition of wheat grain to the diet. Apparent N retention was lower (P = 0.03) for 40W than CON and 20W heifers. In summary, although it led to a desirable decrease in UUN excretion, feeding wheat grain in corn DDGS-containing diets increased acidotic conditions in the rumen, which possibly led to the tendency for a decrease in DMI. The negative apparent N retention at the 40% wheat grain inclusion also suggests a decrease in nutrient supply, which could compromise feedlot performance.

Our objective was to investigate the effects of administering the nonsteroidal anti-inflammatory drug meloxicam (MEL) before transport on various indicators of protein metabolism and growth performance over the first 96 h after transport in Jersey calves. Calves (age ± SD; 2 ± 1 d) sourced from a commercial farm were randomly administered, at 1 mg/kg of body weight, either meloxicam (MEL; n = 11) or a whey protein placebo (CON; n = 10) orally before transport to a calf facility (669 km; 8.5-h road trip). Calves were weighed and rectal temperature was recorded before departure (0 h), on arrival (8.5 h), and 96 h after arrival. Blood was collected at the same time as calves were weighed, and samples were analyzed for total protein (0-h sample), cortisol (0- and 8.5-h samples), haptoglobin (0- and 96-h samples), and amino acids, 3-methylhistidine, and urea-N (96 h). Milk replacer (MR) intake was recorded on arrival and over the next 4 d. Serum total protein concentration did not differ for CON and MEL calves. Plasma cortisol concentration was similar across treatments at 0 h; however, it was lower for CON than for MEL calves at 8.5 h. Although serum haptoglobin concentration tended to be greater for CON than MEL calves 96 h after transport, 3-methylhistidine and plasma urea-N concentrations did not differ across treatments. Plasma Asp, Asn, Glu, Lys, Met, Ser, and Trp were greater and plasma Arg, Gly, Pro, and Thr concentrations tended to be greater at 96 h after arrival for MEL compared with CON calves. Intake of MR and average daily gain were higher in MEL than in CON calves. In summary, although it had no effect on 3-methylhistidine or urea-N concentrations, administration of MEL before transport tended to reduce haptoglobin concentration, altered the amino acid profile, and was beneficial in preventing a decrease in MR intake and average daily gain in Jersey calves.

Because of its high content of polyphenolic compounds, the dietary inclusion of grape pomace (GP) in ruminant diets can reduce reactive nitrogen (N) and methane emissions and enhance the shelf life and beneficial fatty acids (FAs) content of meat. However, the dietary inclusion of GP beyond a threshold that is still to be determined for feedlot cattle can also compromise nutrient supply and, thus, growth performance. This study investigated the optimum proportion of GP in finishing cattle diets. Nutrient intake and apparent total tract digestion, ruminal pH and fermentation, estimated microbial protein synthesis, route of N excretion, and blood metabolites were measured. Six ruminally fistulated crossbred beef heifers (mean initial body weight ± SD: 714 ± 50.7 kg) were used in a replicated 3 × 3 Latin square with 21-d periods. Dietary treatments were 0%, 15%, and 30% of dietary dry matter (DM) as GP, with diets containing 84%, 69%, and 54% dry-rolled barley grain, respectively. There was a linear increase (P = 0.07) in DM intake and quadratic change (P ≤ 0.01) in neutral detergent fiber (NDF) intake. There was a quadratic change (P ≤ 0.04) in apparent total tract DM, NDF, and crude protein digestibility as dietary GP content increased. However, there were no treatment effects (P ≥ 0.18) on total ruminal short-chain FA concentration and duration and area pH < 6.2, 5.8, and 5.5. Although N intake did not differ (269, 262, 253 g/d; P = 0.33) across dietary treatments, feeding GP led to a tendency for a quadratic change (P ≤ 0.07) in ruminal ammonia-N and plasma urea-N concentrations. Total N excretion also changed (quadratic, P = 0.03) because of changes (quadratic, P = 0.02) in fecal N excretion as urinary excretion of N and urea-N did not differ (P ≥ 0.15) across treatments. Feeding GP led to quadratic changes (P ≤ 0.01) in fecal excretion of fiber-bound N. Microbial N flow and apparent N retention also changed (quadratic, P ≤ 0.04) as dietary GP proportion increased. In conclusion, responses to dietary GP proportion were mostly quadratic with indications that nutrient supply as reflected by changes in apparent total tract nutrient digestibility, microbial N supply, and apparent N retention could be compromised beyond a 15% dietary inclusion level.

Because of its content of polyphenolic compounds, feeding grape pomace (GP) could alter nitrogen (N) utilization in cattle in a manner that limits urinary N excretion and, thus, reactive N emissions. However, the preservation method used for GP, whose shelf-life is limited when fresh, could potentially cause changes in the bioactivity of the polyphenolic compounds. This study evaluated the effects of feeding either ensiled or sun-dried GP on ruminal ammonia-N (NH3-N) and plasma urea-N (PUN) concentrations, and route of N excretion in backgrounding cattle. Six ruminally-cannulated beef heifers were used in a replicated 3 × 3 Latin square design with 21-d periods. Dietary treatments were (DM basis): 1) a typical backgrounding diet (CON), 2) CON + 15% ensiled GP, and 3) CON + 15% sun-dried GP. Grape pomace partially replaced triticale silage in the diet. Ruminal fluid (d 19 at 3 h post-feeding), blood (d 21 at 3 h post-feeding), and fecal grab and spot urine samples (d 19 at 0900, 1500, and 2100; d 20 at 0300, 1200, and 1800 h; d 21 at 0000 and 0600 h) were collected and analyzed for metabolites. Data was analyzed using PROC MIXED in SAS. There was no diet effect (P ≥ 0.48) on N intake, and ruminal NH3-N and PUN concentrations. Urine N (g/d and % of N intake) and urea-N (g/d) output were lower (P < 0.01) for heifers fed GP-containing diets than the CON diet. However, fecal N excretion (g/d and % of N intake) was greater (P = 0.01) for heifers fed GP-containing diets than the CON diet. In summary, although there was no diet effect ruminal NH3-N and PUN concentrations, feeding GP irrespective of preservation method, was effective in changing the route of N excretion from urine to feces, which is beneficial from an environmental standpoint.

Feeding corn dried distillers grains with solubles (DDGS) in low crude protein (CP) diets could limit N waste in lactating cows. However, it also could possibly reduce metabolizable AA supply, especially Lys, and compromise milk production. Therefore, the objective of this study was to evaluate the effects of feeding supplemental blends of rumen undegradable protein (RUP) and rumen-protected (RP) AA in a low compared with high CP diet containing corn DDGS on milk production and selected measures of N utilization. Six multiparous Holstein cows (619.3 ± 49.8 kg of body weight; 26.8 ± 6.2 d in milk) were subjected to a split-plot, 3 × 3 Latin square design (21-d periods) with dietary CP content [low (14.6%; LP) or high (16.6%; HP)] as the whole-plot factor, and blend of RUP and RP-AA [control (CON), no supplement; blend A (0.11 kg/cow per d); or blend B (0.45 kg/cow per d)] as the sub-plot factor. All diets contained 10% corn DDGS; blends of RUP and RP-AA were top-dressed during morning feeding. There was no dietary CP content × supplemental blend interaction for all measured variables. Nutrient (dry matter, organic matter, neutral detergent fiber, acid detergent fiber, and CP), milk and milk component yields, and feed and apparent N efficiency did not differ for cows fed the low- compared with the high-protein diet. However, apparent total-tract CP digestibility, blood and milk urea-N concentrations, and urinary excretion (g/d) of N and urea-N were lower for cows fed the low-protein compared with the high-protein diet. There was no supplemental blend effect on nutrient intake and apparent total-tract digestibility, and milk and milk component yields. Except for a tendency for total urinary purine derivative excretion and microbial N flow to be lower for cows fed blend B compared with CON but not blend A, there was no supplemental blend effect on measures of N utilization. Both dietary CP content and supplemental blend of RUP and RP-AA had a marginal effect on the plasma free AA profile. In summary, reducing dietary CP content in diets containing corn DDGS had no effect on lactation performance, possibly accounting for the lack of a positive response following the provision of supplemental blends of RUP and RP-AA. However, reducing dietary CP content resulted in a decrease in blood and milk urea-N concentrations, and urinary excretion of N and urea-N, suggestive of an improvement in the efficiency of N use.

High grain diets are fed to finishing beef cattle to maximize animal performance in a cost-effective manner. However, a small amount of roughage is incorporated in finishing diets to help prevent ruminal acidosis, although few studies have examined optimum roughage inclusion level in barley-based diets. The objective of the study was to evaluate the effects of roughage proportion in barley-based finishing diets on growth performance, feeding behavior, and carcass traits of feedlot cattle. Crossbred beef steers (n = 160; mean body weight ± SD, 349.7 ± 21.4 kg) were allocated to 20 pens that were assigned randomly to four dietary treatments (five pens of eight steers per treatment). The treatment diets contained barley silage at 0%, 4%, 8%, and 12% of dietary dry matter (DM). The remainder of the diets (DM basis) consisted of 80%, 76%, 72%, and 68% barley grain, respectively, 15% corn dried distiller’s grains, 5% mineral and vitamin supplement, and 32 mg monensin/kg diet DM. The diets were fed as total mixed rations for ad libitum intake (minimum of 5% refusal) once per day. Cattle were weighed on 2 consecutive days at the start and end of the experiment and on 1 d every 3 wk throughout the experiment (124 d). Two pens for each treatment group were equipped with an electronic feeding system (GrowSafe Systems Ltd., Calgary, Alberta) to monitor feed intake and feeding behavior of individual cattle. The data for dry matter intake (DMI), average daily gain (ADG), gain:feed (G:F) ratio, and carcass traits were analyzed as a completely randomized design with fixed effect of barley silage proportion and pen replicate as experimental unit. Feeding behavior data were analyzed similarly, but with animal as experimental unit. Averaged over the study, DMI increased linearly (11.1, 11.3, 11.7, 11.8 kg/d; P = 0.001) as barley silage proportion increased from 0%, 4%, 8%, and 12% of DM, but ADG was not affected (carcass-adjusted,1.90, 1.85, 1.87, 1.89 kg/d; P ≥ 0.30). Consequently, G:F ratio decreased linearly (carcass-adjusted, 168.9, 163.8, 158.5, 160.6 g/kg DMI; P = 0.023). When averaged over the study, proportion of barley silage in the diet had no linear or quadratic effects (P > 0.10) on meal frequency, duration of meals, intermeal duration, or meal size, but eating rate decreased linearly with increasing silage proportion (P = 0.008). There was no diet effect on liver abscesses (P ≥ 0.92), and effects on carcass characteristics were minor or nonexistent. We conclude that increasing the proportion of barley silage in a feedlot finishing diet at the expense of barley grain to minimize the incidence of ruminal acidosis may decrease feed conversion efficiency.

Cattle need physically effective fiber to promote rumination and maintain rumen health, but economics favor the use of low-roughage feedlot diets. The study investigated the optimum barley silage proportion in barley-based finishing diets. Apparent total-tract digestibility (4-d total fecal collection), chewing behavior (6-d video recording), ruminal pH (6-d indwelling pH recording), and fermentation (1 day, sampling 0, 3, 6, 12, and 18 h postfeeding), short-chain fatty acid (SCFA) absorption (washed reticulo-rumen technique), gastrointestinal tract barrier function (marker infusion), and blood variables (catheters) were measured. Eight ruminally fistulated crossbred beef heifers (653 ± 44.2 kg; mean starting body weight [BW] ± SD) were used in a replicated 4 × 4 Latin square design with 28-d periods. Dietary treatments were 0%, 4%, 8%, and 12% of dietary dry matter (DM) as barley silage, with diets containing 80%, 76%, 72%, and 68% barley grain, respectively. Increasing silage proportion decreased dietary starch content from 49.0% to 43.1% DM, while neutral detergent content increased from 22.7% to 25.1% DM. Silage proportion had no effect on DM intake, but apparent DM digestibility decreased quadratically (86.0%, 82.1%, 81.1%, 79.5% for the four diets, respectively; P < 0.001). Although, silage proportion had no effect on eating activity, rumination time increased quadratically (246, 289, 302, 316 min/d; P = 0.04). Increased silage proportion increased minimum (5.07, 5.27, 5.29, 5.41; quadratic, P = 0.011) and mean (5.61, 5.87, 5.93, 5.95; quadratic, P = 0.007) ruminal pH, and there was a quadratic (P ≤ 0.047) decrease in duration and area under the pH acidosis threshold curves of 5.8, 5.5, and 5.2. Although increasing silage proportion decreased ruminal acidosis, it was not completely eliminated even with a diet containing 12% silage DM. SCFA concentration in ruminal fluid was not affected by diet, but silage proportion quadratically (P ≤ 0.088) increased ruminal acetate:propionate. There was no effect of diet on absolute or fractional rates of absorption of acetate, propionate, butyrate or total SCFA, and no effect on gastrointestinal barrier function or blood measurements. In conclusion, responses to roughage level were mostly quadratic with greatest improvements in acidosis variables between 0% and 4% barley silage, with incremental improvements with further increases in silage levels. The study showed a trade-off between maximizing digestibility and energy intake to promote animal performance and minimizing the risk of acidosis.

This study examined the effects of altering ruminal fermentable carbohydrate (RFC) supply by feeding different amounts of corn and wheat in finishing cattle diets containing 15% corn dried distillers grains [DDGS; dry matter (DM) basis] on ruminal fermentation characteristics and nitrogen (N) utilization. Six ruminally-cannulated crossbred heifers were used in a replicated 3 × 3 Latin square design with 28 d periods. Dietary treatments were either corn (73% of diet DM; CON), 53:20 corn:wheat blend (20W) or 33:40 corn:wheat blend (40W) as the major fermentable carbohydrate source. Diets were isonitrogenous (12% CP; DM basis). Feed intake was measured daily. Indwelling pH logger were used to measure ruminal pH (d 22 to 28) and ruminal fluid was collected from d 26 to 28 to determine fermentation characteristics, as were feces and urine to measure N excretion. Data was analyzed using PROC MIXED in SAS. Dry matter and N intake tended to be lower (P ≤ 0.07) for heifers fed the 40W compared to the CON and 20W diets. There was no diet effect (P = 0.15) on total VFA concentration; however, the duration and area for pH < 5.5 tended to be longer (P = 0.07) and greater (P = 0.096), respectively, for heifers fed the 20W and 40W compared to the CON diet. There was no diet effect (P ≥ 0.44) on ruminal ammonia concentration and total urine N excretion (g and % of N intake). However, urine urea N (UUN) excretion as a percentage of total urine N tended to be lower (P = 0.05) in heifers fed the 20W and 40W compared to the CON diet. In summary, although altering RFC supply by feeding increasing amounts of wheat resulted in a decrease in UUN excretion, it also caused a decrease in ruminal pH that possibly compromised DM intake.

Clinoptilolite (CLN), could potentially improve nitrogen (N) utilization when fed to beef cattle as it can bind ruminal-ammonia-N (NH3-N), limiting its loss and subsequent detoxification into urea-N, which is released into blood and is excreted in urine. However, the effectiveness of CLN is influenced by physical properties such as particle size. Although decreasing the particle size has been shown to increase the binding of ammonium in-vitro, this remains to be evaluated in vivo. Therefore, the objective of this study was to determine the effects of feeding CLN of two different particle sizes (30 and 400 µm) on ruminal NH3-N and plasma-urea-N (PUN) concentrations, ruminal pH, and nutrient intake and apparent total-tract digestibility. Six ruminally-cannulated beef heifers (mean initial BW± SD, 620.8 ± 30.15) were used in a replicated 3 × 3 Latin square design with 21 d periods (sample collection from d 15 to 21). Dietary treatments were: 1) finishing ration with no supplement (CON), 2) CON +30-µm CLN (CL-30), and 3) CON + 400-µm CLN (CL-400). Clinoptilolite was top-dressed (2.5% of diet DM) during morning feeding. Intake was measured daily. Ruminal fluid was collected on d 19 for NH3-N analysis and blood was collected 3 h post-feeding on d 21 for PUN analysis. Indwelling pH loggers were used to measure ruminal pH (d 15 to 21) and grab fecal samples were collected from d 19 to 21 to determine total-tract nutrient digestibility. Statistical analysis was conducted using PROC MIXED in SAS. There was no treatment effect (P ≥ 0.13) on ruminal NH3-N and PUN concentrations, ruminal pH, and nutrient (DM, OM, NDF, ADF and CP) intake and apparent total tract digestibility. In conclusion, feeding CLN to finishing heifers had no effect on measures of N utilization, ruminal pH and nutrient intake and apparent total-tract digestibility.

Sugar beet processing by-products can be used to increase nutrient supply in beef cattle fed low-quality forages. However, information on the effectiveness of the different byproducts on modulating ruminal fermentation is still limited. Our objective was to determine the effects of providing supplemental molasses, concentrated seperator by-product, liquid feed-grade (32% purity) and crystalline betaine (97%) on in vitro fermentation and dry matter digestibility (IVDMD). A batch culture system was used to evaluate volatile fatty acid (VFA) production (3 h), pH (24 and 48 h), and IVDMD (24 and 48 h). A low-quality hay (7.5% crude protein; 58% total digestible nutrients) was used as a substrate and the inclusion level was 10% (dry matter [DM] basis) for all by-products except for crystalline betaine. Because it is a solid, a solution of crystalline betaine was made such that the betaine inclusion level was similar to that of feed-grade betaine. Data was analyzed using PROC MIXED in SAS. Total VFA concentration was lower (P < 0.01) for crystalline and liquid betaine compared to molasses and concentrated seperator by-product. Molar proportion of propionate was lower for concentrated seperator by-product (P = 0.04) than for the other treatments whereas the molar proportion of butyrate was lower (P = 0.04) for crystal betaine compared to molasses and concentrated seperator by-product. However, although pH was lower (P < 0.01) at 48 than 24 h, whereas DMD was greater (P < 0.01) at 48 than 24 h, there was no treatment effect (P ≥ 0.18) on pH and in vitro dry matter digestibility (DMD) at both 24 and 48 h. In summary, although adding different by-products from sugar beet processing resulted in changes in the VFA profile at 3 h of in vitro incubation, it had no effect on 24 and 48 h pH and IVDMD.

Grazing could be used to control invasive grass species on rangeland. However, the characterization of the seasonal changes in the nutritive value of the invasive grass species will enable the development of targeted grazing strategies. Therefore, the objective of this study was to determine the in vitro fermentation characteristics of Cheatgrass (Bromus tectorum L.) and Medusahead (Taeniatherum caputmedusae L.) harvested on Idaho rangeland. Forage samples were collected from the Reynold Creek watershed (Owyhee county, ID) in summer (June 2018), fall (September 2018) and winter (January 2019). A batch culture system was then used to evaluate volatile fatty acid (VFA) production (6 h), and in vitro dry matter (IVDMD) and NDF digestibility (IVNDFD; 24 h and 48 h). All data was analyzed using the MIXED procedure of SAS. There was no season or grass species effect (P ≥ 0.24) on total VFA concentration and the molar proportion of acetate. However, there was a season × grass species interaction (P = 0.04) for the molar proportion of propionate; it was higher for cheatgrass than medusahead in summer, but not in winter and fall. Both season and grass species had no effect (P ≥ 0.11) on the molar proportions of butyrate, valerate, and total branch chain VFA. There was a season × grass species interaction for 24 and 48 h IVDMD and 24 h IVNDFD (Table 1). In addition, 48 h IVNDFD was greater (P < 0.01) when grasses were harvested during the summer compared to the fall and winter seasons. In summary, although there were no differences across invasive grass species when harvested during the fall and winter seasons, the molar proportion of propionate, 24 and 48 h IVDMD and 24 h IVNDFD were greater for cheatgrass compared to medusahead when harvested in summer.

Our objective was to determine the effects of feeding 0, 4, 8 or 12% barley silage (DM basis) in place of barley grain in finishing cattle diets containing 15% corn dried distillers grains (DDGS) on chewing behavior, and gastrointestinal digestive, absorptive and barrier functions. Crossbred heifers (n = 8; 653 ± 44.2 kg; mean BW ± SD) were used in a replicated 4 × 4 Latin square design with 28 d periods. The dietary treatments were 0, 4, 8 or 12% barley silage (DM basis); the remainder consisted of 80, 76, 72 or 68% barley grain, respectively, and 15% corn DDGS and 5% mineral/vitamin supplement. Feed intake was measured daily. A digital video recording system was used to monitor (d 10 to 16) chewing behavior. Ruminal pH was measured using indwelling loggers (d 16 to 22), and ruminal fluid was collected on d 17 to determine VFA concentration. To assess total tract barrier function, Cr-EDTA solution was dosed into the rumen on d 20 and urine was collected over the next 48 h and analyzed for Cr. On d 28, the temporarily isolated and washed reticulo-rumen technique was used to determine VFA absorption. All data were analyzed using PROC MIXED in SAS. Although there was no diet effect (P ≥ 0.05; Table 1) on ruminal total VFA and lactate concentrations, the duration pH < 5.5 and acidosis index were greater (quadratic; P ≤ 0.04), and total ruminating time was shorter (quadratic; P = 0.04) for cattle fed the 0% compared to the 4, 8 and 12% silage diets. However, there was no diet effect (P ≥ 0.17) on VFA absorption and barrier function. In summary, feeding at least 4% barley silage in finishing diets containing 15% corn DDGS increased ruminating time, which possibly reduced the severity of ruminal acidosis. [Image: see text]

Eragrostis tef (‘Moxie’ teff) could be a viable alternative forage for beef cattle. However, there is limited information on ruminal and total tract nutrient digestibility when teff hay harvested at different stages of maturity is fed to cattle. Therefore, our objective was to determine the effects of feeding teff hay harvested at the boot (BT), early-heading (EH), or late-heading (LH) stages of maturity on nutrient intake, ruminal digestion, omasal flow, and apparent total tract digestion in beef cattle. Six ruminally cannulated beef heifers (mean initial BW ± SD, 476 ± 32.6) were used in a replicated 3 × 3 Latin square with 28-d periods (18 d for adaptation). Dietary treatments were BT, EH, or LH teff hay, and DMI was measured daily. Omasal digesta was collected (d 26 to 28) for measurement of ruminal digestion and omasal nutrient flow, as were fecal samples for apparent total tract nutrient digestibility determination. Data was analyzed using PROC MIXED in SAS. The NDF and ADF content of teff did not change (P ≥ 0.29) with advancing maturity. Diet also had no effect (P ≥ 0.14) on intake, ruminal digestion, omasal flow and apparent total tract digestion of DM, NDF, and ADF. Crude protein content decreased (P < 0.01) with advancing maturity (18.7, 14.7, and 11.9%, respectively). Crude protein intake was lower (P < 0.01) for heifers fed EH and LH than BT hay. Although there was no diet effect (P > 0.23) on ruminal digestion and omasal flow, total tract digestion of CP was (P < 0.01) lower for heifers fed LH than BT hay (83.3 vs. 78.3%). In summary, delaying harvest of teff hay had no effect on NDF and ADF intake, digestibility and omasal flow. However, delaying harvest resulted in a decreased in CP content, intake and apparent total tract digestion.

Our objective was to investigate the effects of post weaning forage grazing on heifer development and fertility. Weaned (7.5 mo old) crossbred heifers (n = 139) were strip-grazed on alfalfa (A) or grass (G) pastures for 56 d with 2 replicates per treatment. Heifers were weighed every 2 wk and forage samples were collected on wk 1, 4, and 8. After grazing, all heifers were managed similarly. At 10 d before estrous synchronization, heifers weighed 381.7 ± 2.9 kg, and reproductive tract score (RTS) and antral follicle count (AFC) were determined by ultrasonography. Heifers were synchronized using the 14 d CIDR Split-Time AI protocol. Serum progesterone concentrations were determined at ultrasonography and synchronization. Heifers were considered pubertal when progesterone concentration was >1 ng/mL. A mixed model was used to determine effects of forage, wk, and their interaction on diet composition, and forage effects on heifer bodyweight at the end of treatment (BWT) and at ultrasonography (BWU), average daily gain (ADG), RTS and AFC. Correlations between variables were also tested. Crude protein was affected by forage and wk (P < 0.05), and averaged 15.5% of dry matter for A and 8.87% for G. There was a forage by wk interaction on acid detergent fiber (P < 0.02). Forage did not affect BWT or BWU, but A heifers gained more than G heifers (0.41 ± 0.03 vs. 0.20 ± 0.03 kg/d; P = 0.03). Both BWT and BWU were correlated with RTS, regardless of treatment (r = 0.40 and 0.40, respectively, P < 0.01). There was no effect of forage type on pubertal status (P= 0.85) or pregnancy rate (P = 0.67). In summary, replacement heifers were grazed on alfalfa or grass pastures after weaning, which resulted in different growth rates but did not compromise fertility measures.

The objective of this study was to determine the effects of pre-transport administration of Meloxicam (MEL) on protein metabolism in transported calves. Prior to transportation, Jersey bull calves (n = 20; 4 d old) were weighed, and body temperature was recorded before collection of blood samples. Calves were then administered either a whey protein placebo (CON; n =10) or MEL (1 mg/kg BW; n = 10) before transportation in a livestock trailer to a calf raising facility (8 h trip). Calves were weighed, body temperature recorded and blood samples collected on arrival, and at 96 h post-arrival. Milk replacer intake was also recorded during the first 96 h post-arrival. After the 96 h blood collection, calves were euthanized, and skeletal muscle (biceps femoris) samples were collected and used for measurement of mRNA abundance for mammalian target of rapamycin (mTOR) and ubiquitin conjugating enzyme 1 (UBE1). Blood samples were analyzed for cortisol, haptoglobin, urea N, 3-methylhistidine (3-MH) and AA. All data was analyzed using SAS. Body temperature, blood cortisol, haptoglobin, urea-N and 3-MH concentrations did not differ (P ≥ 0.17) between CON and MEL calves. Although milk replacer intake tended (P = 0.05) to be higher for MEL compared to CON calves (1.13 vs. 1.07 kg/d), there was no treatment effect on ADG (P = 0.81) and gain:feed (P = 0.58). Similarly, there were no differences (P ≥ 0.35) in mRNA abundance for mTOR or UBE2G1. However, plasma Asp concentration tended to be higher (7.87 vs. 5.47 µg/mL; P = 0.07) and Cit concentration was higher (19.2 vs. 15.2 µg/mL; P = 0.04) for MEL than CON calves. In summary, pre-transport administration of MEL had no effect on blood cortisol and most measures of protein metabolism including blood urea-N, 3-MH, and mRNA abundance for mTOR or UBE1.

Although it can be available for use in finishing cattle diets, there is still limited information on the effects of feeding grape pomace (GP) in place of barley grain on nutrient supply. Therefore, our objective was to determine the effects of feeding 0, 15, or 30% GP (DM basis) on nutrient intake, ruminal and apparent total tract nutrient digestibility, and nitrogen (N) excretion in beef cattle. Six ruminally-cannulated heifers (mean initial BW ± SD, 714 ± 50.7 kg) were used in a replicated 3 × 3 Latin square with 21-d periods (14 d for adaptation). Heifers were fed finishing diets containing 0, 15, or 30% GP (DM basis); GP partially replaced barley grain. Dry matter intake was measured daily. Ruminal fluid was collected (d 15) to determine fermentation characteristics. Feces and urine were collected (d 19 to 21) to measure apparent total tract nutrient digestibility and N excretion. Blood samples were collected 3 h post-feeding on d 21. Data was analyzed using PROC MIXED in SAS. Although it had no effect (P = 0.27) on DMI, increasing the amount of GP in the diet increased (P < 0.01) NDF and ADF intake. Apparent total tract DM, NDF, and ADF digestibility were lower (P < 0.01) in heifers fed the 30 than 0 and 15% GP diets. Although there was no diet effect (P ≥ 0.11) on the VFA profile, rumen NH(3)-N tended to be greater (P = 0.07), and BUN was greater (P = 0.04) for heifers fed the 30 than 0 and 15% GP diets. However, there was no treatment effect (P ≥ 0.33) on microbial N supply, urine N and urea-N excretion. In summary, feeding an increasing amount of GP in finishing diets reduced apparent total tract DM, NDF, and ADF digestion and did not improve N utilization.

Our objective was to determine the effects of feeding a high amount of grape pomace (GP) in finishing (FIN) cattle diets on product quality. A group of 24 cows (Jersey × Holstein crosses), were allotted to either a typical FIN diet (CON) or a FIN diet containing 58% GP (DM basis). The GP partially replaced some of the energy sources in the CON diet. After harvest (262 to 288 d on feed), carcasses were chilled for 24 h before collection of wholesale cuts (longissimus lumborum [strip loin]) that were vacuum-packed and aged for 14 d. Thereafter, 2.54 cm-thick steaks were cut from trimmed muscle for determination of fluid and cooking loss, tenderness (WBSF), color (Hunter Mini-Scan) and lipid oxidation (T-BARS) over 8-d of retail display, and fatty acid (FA) composition. Data was analyzed using PROC MIXED in SAS. Although it tended (P = 0.06) to reduce fluid loss (1.32 vs. 1.83%), feeding 58% GP had no effect (P ≥ 0.36) on cook loss and tenderness. However, there was a treatment × day interaction (P < 0.01) on lipid oxidation and color; feeding 58% GP compared to CON reduced lipid oxidation (d 4 to 8), and increased brightness (L*; all days except d 3 and 4) and redness (a*; all days except d 0, 3 and 3) of steaks during retail display. Although it had no effect (P ≥ 0.20) on total saturated and unsaturated FA, feeding 58% GP also reduced trans18:1 (1.36 vs. 4.35 % of total FA; P < 0.01) and increased CLA c9t11 (0.419 vs. 0.213 % of total FA; P < 0.01) concentration. In summary, feeding a high amount of GP in FIN diets resulted in a beneficial decrease in lipid oxidation, and an increase in the brightness and redness, and CLA c9t11 content of longissimus steaks.

This study evaluated the interaction between the stage of maturity of Eragrostis tef (teff) grass and supplemental energy source on ruminal fermentation characteristics and nitrogen (N) utilization. Six ruminally-fistulated beef heifers were used in a 3 × 3 split-plot design (21 d periods). The whole plot factor was stage of maturity of teff hay [early- (EH) or late-heading (LH)], and the subplot factor was supplemental energy source [no supplement (CON), rolled corn grain or beet pulp pellet (BP)] fed at 0.5% of body weight. Feed intake was measured daily. Indwelling pH loggers were used to measure ruminal pH (d 14 to 21) and ruminal fluid was collected from d 19 to 21 to determine fermentation characteristics, as were feces and urine to measure N excretion. Data was analyzed using PROC MIXED in SAS. There was no stage of maturity × supplement interaction for all measurements (P ≥ 0.17). Although dry matter intake (DMI) tended to be greater (P = 0.07) for heifers fed EH than LH hay, it did not differ (P = 0.88) across supplements. Ruminal acetate concentration tended (P = 0.098) to be greater for EH than LH heifers, whereas butyrate, isobutyrate, and isovalerate concentrations were greater (P ≤ 0.045) for BPP than CON heifers. However, the duration and area pH < 6.2 and 5.8 did not differ (P > 0.12) across treatments. Except for microbial N flow, which was greater (P < 0.01) for EH than LH heifers, there was no stage of maturity or supplement effect (P ≥ 0.14) on measures of N utilization. In summary, feeding teff hay harvested at the EH than LH stage of maturity increased DMI and microbial N supply, whereas feeding corn and BP as energy supplements to beef heifers had no effect on ruminal pH.

Teff (Eragrostis tef cv. Moxie), a warm-season annual grass, could be an excellent forage for beef cattle. However, there is limited information on its nutritive value to cattle when harvested at different stages of maturity. Thus, the objective of this research was to determine the effect of feeding teff hay harvested at the boot (BT), early-heading (EH), or late-heading (LH) stages of maturity on nutrient intake, ruminal fermentation characteristics, omasal nutrient flow, and N utilization in beef cattle. Six ruminally cannulated beef heifers (mean initial BW ± SD, 476 ± 32.6) were used in a replicated 3 × 3 Latin square design with 28-d periods (18 d for adaptation and 10 d for measurements). Dry matter intake was measured daily. Indwelling pH loggers were used to measure ruminal pH from days 21 to 28. Ruminal fluid and omasal digesta were collected from days 26 to 28 to determine fermentation characteristics and omasal nutrient flow. Fecal and urine samples to quantify N excretion were also collected (days 26 to 28). Blood samples for plasma urea-N (PUN) determination were collected 3 h post-feeding on day 28. There were no changes (P > 0.28) in the ADF or NDF content of teff with advancing maturity, but indigestible NDF increased (P < 0.01) with increasing maturity. Maturity had no effect (P ≥ 0.14) on DMI, and ruminal total short-chain fatty acid (SCFA) concentration, pH, digestibility, and outflow of DM, OM, NDF, ADF, and CP. However, the CP content of BT hay was greater (P < 0.01) than for EH and LH hay (18.1, 14.1, and 11.5%, respectively, DM basis), and this resulted in the higher CP intake (P < 0.01) for heifers fed the BT than the EH and LH hay. Consequently, ruminal ammonia-N (NH3-N) concentration was greater (P < 0.01) for heifers fed BT than EH and LH hay, thereby possibly explaining the tendency for a decrease (P = 0.08) in PUN concentration, and a decrease (P < 0.01) in the excretion of total N, urine N, and urea-N (UUN) with advancing maturity. However, fecal N excretion (g/d) did not differ (P = 0.76). In conclusion, despite a decrease in CP intake and ruminal NH3-N concentration, feeding beef heifers EH and LH compared to BT teff hay did not compromise ruminal digestion and outflow of DM, OM, NDF, ADF, and CP, and microbial protein synthesis. Advancing maturity in teff hay also resulted in a decrease in the excretion of total N and urine N and UUN when fed to cattle.

Video recordings of behavioral activities including eating, ruminating, drinking, standing, and lying were monitored to determine the minimum number of sampling days and sampling frequency required to obtain reliable estimates of these behaviors. Eight continental crossbred heifers, individually housed in a tie-stall barn with total mixed ration provided once per day, were divided by BW into two blocks and assigned to each of the two dietary treatments in a crossover design: high-forage diet (HF, forage:concentrate ratio 70:30) and low-forage diet (LF, forage:concentrate ratio 30:70). The cows were monitored continuously using a digital video recording system for 6 d in each of the two periods and a trained observer manually recorded the behavioral activities by minute. Mean time spent performing each behavior for 6 d with instantaneous samples of 1 min was compared with those obtained using fewer sampling days (1, 2, 3, 4, and 5 d) and less frequent scanning (2, 3, 4, 5, 10, 15, 30, and 60 min) using linear regression analysis, and the minimum number of sampling days or frequency was determined. Diet did not affect the accuracy and precision of predicting behavior from video recordings of the cows. When sampling days and scanning intervals were combined, the minimum recommended sampling frequency for accurately estimating a specific set of behaviors of beef heifers in tie stalls was: eating, 2 d with 4-min intervals; ruminating, 3 d with 4-min intervals; drinking, 2 d with 3-min intervals; and standing and lying, 2 d with 15-min intervals. Increasing sampling frequency beyond these minimums further enhanced the accuracy and precision of predictions. The total time of each behavioral activity was different between cows fed HF and LF diets with eating, ruminating, total chewing, and standing of heifers fed the HF diet greater (P < 0.01), but the lying (P < 0.01) and drinking time (P = 0.028) of heifers fed the LF diet greater. Meal patterns were different (P < 0.05) between the treatments except when meal size (kg) was expressed as DM or OM intake. For rumination patterns, the mean or maximum bout length (min/bout) was greater, but the maximum or minimum length of time heifers took to ruminate after eating was lower for the HF diet. From a practical standpoint, it is recommended to use 3 days of observations scanned at an interval of 4 min to reliably estimate the behavior of cows. If the focus is only lying and standing time, then 2 days with 15 min intervals can be used.

Although grape pomace (GP) is increasingly available for use as cattle feed, there is still limited information on its feeding value. Therefore, our objective was to determine the effects of feeding increasing amounts of GP in backgrounding cattle diets on nutrient intake and digestibility, ruminal fermentation, and nitrogen (N) excretion. Six ruminally-cannulated heifers (mean initial BW ± SD, 614 ± 49.5 kg) were used in a replicated 3 × 3 Latin square with 21-d periods (14 d for adaptation). Heifers were fed backgrounding diets containing 0, 15, or 30% GP (DM basis); GP partially replaced alfalfa silage. Dry matter intake was measured daily. Ruminal fluid was collected from d 19 to 21 to determine fermentation characteristics, as were feces and urine to measure apparent total tract nutrient digestibility and N excretion. Plasma was collected 3 h post-feeding on d 21. Data was analyzed using PROC MIXED in SAS. Dry matter intake tended (P = 0.07) to be greater, and ADF and CP intake were greater (P < 0.02) for heifers fed the 15 and 30 than 0 % GP diet. However, DM, OM, NDF, ADF, and CP digestibility decreased (P ≤ 0.01) as dietary GP content increased in the diet. Although there was no diet effect (P ≥ 0.33) on rumen NH(3)-N, plasma urea-N, and urine N and urea-N excretion, fecal N output was greatest (P < 0.01) for heifers fed 30% GP. Apparent N retention tended to be greater (P = 0.06) for heifers fed the 15% than 0 and 30% GP diet. In summary, although it increased intake, increasing the dietary inclusion level of GP reduced apparent total tract DM, ADF, and CP digestion. However, N retention tended to be greater for heifers fed the 15 than 0 and 30 % GP diets.

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.

In cows fed diets based on corn-alfalfa silage, replacing starch with sugar improves milk production. Although the rate of ruminal fermentation of sugar is more rapid than that of starch, evidence has been found that feeding sugar as a partial replacement for starch does not negatively affect ruminal pH despite increasing diet fermentability. The mechanism(s) for this desirable response are unknown. Our objective was to determine the effects of replacing barley or corn starch with lactose (as dried whey permeate; DWP) on ruminal function, short-chain fatty acid (SCFA) absorption, and nitrogen (N) utilization in dairy cows. Eight lactating cows were used in a replicated 4 × 4 Latin square design with 28-d periods and source of starch (barley vs. corn) and level of DWP (0 vs. 6%, DM basis) as treatment factors. Four cows in 1 Latin square were ruminally cannulated for the measurement of ruminal function, SCFA absorption, and N utilization. Dry matter intake and milk and milk component yields did not differ with diet. The dietary addition of DWP tended to increase ruminal butyrate concentration (13.6 vs. 12.2 mmol/L), and increased the Cl(-)-competitive absorption rates for acetate and propionate. There was no sugar effect on minimum ruminal pH, and the duration and area when ruminal pH was below 5.8. Minimum ruminal pH tended to be lower in cows fed barley compared with those fed corn (5.47 vs. 5.61). The duration when ruminal pH was below pH 5.8 tended to be shorter (186 vs. 235 min/d), whereas the area (pH × min/d) that pH was below 5.8 was smaller (47 vs. 111) on the corn than barley diets. Cows fed the high- compared with the low-sugar diet had lower ruminal NH3-N concentration. Feeding the high-sugar diet tended to increase apparent total-tract digestibility of dry matter and organic matters and increased apparent total-tract digestibility of fat. Apparent total-tract digestibility of N tended to be greater in cows fed barley compared with those fed corn, whereas apparent total-tract digestibility of acid-digestible fiber was greater in cows fed corn compared with those fed barley. In conclusion, partially replacing dietary corn or barley starch with sugar upregulated ruminal acetate and propionate absorption, suggesting that the mechanisms for the attenuation of ruminal acidosis when sugar is fed is partly mediated via increased SCFA absorption.

A study was conducted to determine the effects of including either wheat-based (W-DDGS) or corn-wheat blend (B-DDGS) dried distillers grains with solubles as the major protein source in low- or high-crude protein (CP) diets fed to dairy cows on ruminal function, microbial protein synthesis, omasal nutrient flows, urea-N recycling, and milk production. Eight lactating Holstein cows (768.5 ± 57.7 kg of body weight; 109.5 ± 40.0 d in milk) were used in a replicated 4 × 4 Latin square design with 28-d periods (18d of dietary adaptation and 10d of measurements) and a 2 × 2 factorial arrangement of dietary treatments. Four cows in one Latin square were ruminally cannulated for the measurement of ruminal fermentation characteristics, microbial protein synthesis, urea-N recycling kinetics, and omasal nutrient flow. The treatment factors were type of distillers co-product (W-DDGS vs. B-DDGS) and dietary CP content [15.2 vs. 17.3%; dry matter (DM) basis]. The B-DDGS was produced from a mixture of 15% wheat and 85% corn grain. All diets were formulated to contain 10% W-DDGS or B-DDGS on a DM basis. No diet effect was observed on DM intake. Yields of milk, fat, protein, and lactose, and plasma urea-N and milk urea-N concentrations were lower in cows fed the low-CP compared with those fed the high-CP diet. Although feeding B-DDGS tended to reduce ruminal ammonia-N (NH3-N) concentration compared with feeding W-DDGS (9.3 vs. 10.5mg/dL), no differences were observed in plasma urea-N and milk urea-N concentrations. Additionally, dietary inclusion of B-DDGS compared with W-DDGS did not affect rumen-degradable protein supply, omasal flows of total N, microbial nonammonia N (NAN), rumen-undegradable protein, and total NAN, or urea-N recycling kinetics and milk production. However, cows fed the low-CP diet had lower N intake, rumen-degradable protein supply, ruminal NH3-N concentration, and omasal flows of N, microbial NAN, and total NAN compared with those fed the high-CP diet. Feeding the low-CP compared with the high-CP diet also resulted in lower endogenous urea-N production, urea-N recycled to the gastrointestinal tract, and urea-N excretion in urine. In summary, our results indicate that both W-DDGS and B-DDGS can be included as the major protein sources in dairy cow diets without compromising nutrient supply and production performance. However, feeding the low-CP diet lowered omasal flows of microbial protein and metabolizable protein, which, in turn, resulted in lower milk production compared with feeding the high-CP diet.

Feces from cattle fed 65 different diets were used to develop near-infrared spectroscopy (NIRS) calibrations to predict fecal composition [organic matter (OM), starch, nitrogen (N), neutral deterge...

A study was conducted to determine the effects of replacing canola meal (CM) as the major protein source with wheat-based dried distillers grains with solubles (W-DDGS) on ruminal fermentation, microbial protein production, omasal nutrient flow and animal performance. Eight lactating dairy cows were fed in a replicated 4 × 4 Latin square design with 28-d periods (20 d of dietary adaptation and 8 d of measurements). Four cows in one Latin square were ruminally cannulated for measurements of ruminal fermentation characteristics and flow of nutrients at the omasal canal. Cows were fed either a standard barley silage-based total mixed ration containing CM as the major protein supplement (0% W-DDGS, control) or diets formulated to contain 10, 15, and 20% W-DDGS (dry matter basis), with W-DDGS replacing primarily CM. Diets were isonitrogenous (18.9% crude protein) and contained 3.0, 3.2, 3.5, and 3.7% ether extract for 0, 10, 15, and 20% W-DDGS, respectively. Diets contained 50% forage and 50% concentrate. Inclusion of W-DDGS linearly increased dry matter intake (29.5, 31.2, 30.2, and 31.9 kg/d for 0, 10, 15, and 20% W-DDGS, respectively). The addition of W-DDGS in place of CM resulted in a 1.2- to 1.8-kg increase in milk yield (42.9, 44.7, 44.1, and 44.5 kg/d for 0, 10, 15, and 20% W-DDGS); however, a quadratic change in feed efficiency (i.e., milk yield/DM intake) occurred as the dietary level of W-DDGS increased. Treatments did not differ for milk fat, protein, and lactose concentrations; however, quadratic changes were observed in milk yields of fat (1.48, 1.56, 1.62, and 1.55 kg/d for 0, 10, 15, and 20% W-DDGS, respectively), protein (1.44, 1.46, 1.49, and 1.42 kg/d) and lactose (1.96, 2.02, 2.09, and 1.93 kg/d). Ruminal fermentation characteristics did not change except that the inclusion of 20% W-DDGS resulted in a decrease and a tendency for a decrease in molar concentrations of isobutyrate and total volatile fatty acids, respectively. Omasal flow of total bacterial nonammonia N (NAN) and bacterial efficiency (g of total bacterial NAN flow/kg of organic matter truly digested in the rumen) were not different among diets; however, feeding W-DDGS resulted in a quadratic increase in nonammonia nonbacterial N flow at the omasal canal (271, 318, 336, and 311 g/d for 0, 10, 15, and 20% W-DDGS, respectively). These data indicate that W-DDGS can substitute for CM as the major protein source in dairy cow diets without negatively affecting ruminal fermentation, microbial protein production, and omasal nutrient flow, and can potentially increase dry matter intake and milk yield.

Limited research suggests that propylene glycol (PG) supplementation can have inhibitory effects on ruminal microbes. Our hypothesis was that PG supplementation would reduce microbial protein production. The objective of this study was to determine the effect of PG supplementation on microbial protein production in transition dairy cows. Sixteen pregnant cows (seven primiparous and nine multiparous) were paired based on expected calving dates and then randomly assigned within each pair to either a basal diet (control) or basal diet plus 624 g d-1 of PG. Diets were fed twice daily for ad libitum intake, and PG was fed in equal amounts as a top dress from day -7 to day 45 (transition period). Sample collection was carried out at three time intervals starting at day -14 ± 5, day 15 and day 38 relative to calving, with the first collection period (day -14 ± 5) being the pretreatment period. Propylene glycol supplementation had no effect on total urine purine derivatives (PD; allantoin + uric acid) excretion; consequently, microbial N supply, estimated using total urinary PD excretion, was not affected by PG supplementation. There was an increase in urine total PD excretion and, thus, estimated microbial N supply, with time relative to calving. Microbial efficiency did not change with time relative to calving and, therefore, the increase in dry matter intake during the post-partum period led to the increase in estimated microbial N supply. Results from this study indicate that supplementing PG over the transition period had no effect on microbial protein production in the rumen.Key words: Transition dairy cow, propylene glycol, microbial protein production

Early-lactating dairy cows mobilize body protein to provide amino acids that are directed toward gluconeogenesis and milk protein synthesis. Propylene glycol (PG) is a precursor of ruminal propionate, and feeding PG has been reported to improve energy supply by increasing blood glucose. Our hypothesis was that feeding PG could spare body protein by providing an alternative source of carbon for gluconeogenesis. The major objectives of this study were 1) to delineate the effects of pre- and postpartum PG supplementation in transition dairy cows on whole-body nitrogen balance, urinary 3-methylhistidine (3-MH) excretion, body composition, and gene expression profiles for the major protein degradation pathways in skeletal muscle; and 2) to characterize the changes in body protein metabolism during the periparturient period. Sixteen pregnant cows (7 primiparous and 9 multiparous) were paired based on expected calving dates and then randomly assigned within each pair to either a basal diet (control) or basal diet plus 600 mL/d of PG. Diets were fed twice daily for ad libitum intake, and PG was fed in equal amounts as a top dress from d -7 to d 45. All measurements were conducted at 3 time intervals starting at d -14 +/- 5, d 15, and d 38 relative to calving. Propylene glycol had no effect on whole-body N balance, urinary 3-MH excretion, or body composition. However, N balance was lower at d 15 and 38, compared with d -14. Urinary excretion of 3-MH was lower at d -14 than at d 15 and 38. Supplemental PG had no effect on body weight (BW) and all components of empty BW. On average, cows fed both diets mobilized 19 kg of body fat and 14 kg of body protein between d -14 and d 38. Supplemental PG had no effect on mRNA abundance in skeletal muscle for m-calpain, and the 14-kDa ubiquitin-carrier protein E2 (14-kDa E2) and proteasome 26S subunit-ATPase components of the ubiquitin-mediated proteolytic pathway; however, PG supplementation downregulated mRNA expression for mu-calpain at d 15, and tended to downregulate mRNA expression for ubiquitin at d 15 and 38. Relative to calving, mRNA abundance for m- and mu-calpain, ubiquitin, and 14-kDa E2 were greater at d 15 compared with d -14 and d 38. In summary, these results indicate that transitional effects on whole-body metabolism and gene expression for the Ca(2+)-dependent and ubiquitin-mediated proteolytic pathways in skeletal muscle were more pronounced than those elicited by PG supplementation.