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A mature dairy cow was transitioned from a high forage (100% forage) to a high-grain (79% grain) diet over seven days. Continuous ruminal pH recordings were utilized to diagnose the severity of ruminal acidosis. Additionally, blood and rumen papillae biopsies were collected to describe the structural and functional adaptations of the rumen epithelium. On the final day of the grain challenge, the daily mean ruminal pH was 5.41 ± 0.09 with a minimum of 4.89 and a maximum of 6.31. Ruminal pH was under 5.0 for 130 minutes (2.17 hours) which is characterized as the acute form of ruminal acidosis in cattle. The grain challenge increased blood beta-hydroxybutyrate by 1.8 times and rumen papillae mRNA expression of 3-hydroxy-3-methylglutaryl-coenzyme A synthase by 1.6 times. Ultrastructural and histological adaptations of the rumen epithelium were imaged by scanning electron and light microscopy. Rumen papillae from the high grain diet displayed extensive sloughing of the stratum corneum and compromised cell adhesion as large gaps were apparent between cells throughout the strata. This case report represents a rare documentation of how the rumen epithelium alters its function and structure during the initial stage of acute acidosis.

Fatty acid (FA) composition in beef is related to beef quality and human health. It was recently reported that feeding active dried yeast (ADY) in finishing bull altered some FA of longissimus muscle. The objective was to evaluate the effects of adding ruminally protected versus non-protected ADY on FA profiles of the pars costalis diaphragmatis (PCD) muscle of beef cattle. Seventy-five Angus steers (initial BW 448 kg) were assigned to a randomized complete block design with five treatments: control (no additives), antibiotics (ANT, 330 mg monensin + 110 mg tylosin/d), ADY (1.5 g/d), encapsulated ADY (EDY, 3 g/d) and combination of ADY and EDY (MDY). The encapsulated ADY consisted of 1.5 g ADY and 2 g capsule. Antibiotics, ADY and EDY were top-dressed to a diet containing 10% barley silage and 90% barley concentrate (DM basis). The PCD samples were collected from cattle at slaughter. Intakes (g/d) of total FA (144), saturated FA (SFA; 41), monounsaturated FA (MUFA, 16) and polyunsaturated FA (PUFA, 87) were not different among treatments. Proportion of SFA (49.0%) and MUFA (48.2%) in PCD did not differ among treatments, whereas the proportion of PUFA was greater (P < 0.05) with EDY (3.0%) and MDY (3.0%) than control (2.4%). The proportion of n-3 FA also tended (P < 0.06) to be greater with EDY (0.49%) and MDY (0.50%) than control (0.41%) and ADY (0.41%). Steers fed EDY and MDY enhanced (P < 0.05) the proportion of linoleic acid (LA n-6) and decosapentaenoic acid (DPA n-3) compared with control. These results indicated that feeding EDY and MDY increased amounts of PUFA, FA n-3, LA n-6 and DPA n-3. Inclusion of encapsulated yeasts to diet might increase the amount of bioactive yeasts reached intestines and result in better utilization of PUFA from the digesta and increase the accumulation in the intramuscular fat.

Fatty acid (FA) composition in beef is related to beef quality and human health. It was recently reported that feeding active dried yeast (ADY) in finishing bull altered some FA of longissimus muscle. The objective was to evaluate the effects of adding ruminally protected versus non-protected ADY on FA profiles of the pars costalis diaphragmatis (PCD) muscle of beef cattle. Seventy-five Angus steers (initial BW 448 kg) were assigned to a randomized complete block design with five treatments: control (no additives), antibiotics (ANT, 330 mg monensin + 110 mg tylosin/d), ADY (1.5 g/d), encapsulated ADY (EDY, 3 g/d) and combination of ADY and EDY (MDY). The encapsulated ADY consisted of 1.5 g ADY and 2 g capsule. Antibiotics, ADY and EDY were top-dressed to a diet containing 10% barley silage and 90% barley concentrate (DM basis). The PCD samples were collected from cattle at slaughter. Intakes (g/d) of total FA (144), saturated FA (SFA; 41), monounsaturated FA (MUFA, 16) and polyunsaturated FA (PUFA, 87) were not different among treatments. Proportion of SFA (49.0%) and MUFA (48.2%) in PCD did not differ among treatments, whereas the proportion of PUFA was greater (P < 0.05) with EDY (3.0%) and MDY (3.0%) than control (2.4%). The proportion of n-3 FA also tended (P < 0.06) to be greater with EDY (0.49%) and MDY (0.50%) than control (0.41%) and ADY (0.41%). Steers fed EDY and MDY enhanced (P < 0.05) the proportion of linoleic acid (LA n-6) and decosapentaenoic acid (DPA n-3) compared with control. These results indicated that feeding EDY and MDY increased amounts of PUFA, FA n-3, LA n-6 and DPA n-3. Inclusion of encapsulated yeasts to diet might increase the amount of bioactive yeasts reached intestines and result in better utilization of PUFA from the digesta and increase the accumulation in the intramuscular fat.

Abstract Our previous study suggested that supplementation of high-grain diets with ruminally protected and non-protected active dried yeast (ADY) may potentially reduce manure pathogen excretion by feedlot cattle. We hypothesized that feeding ruminally protected ADY might change the fecal bacterial community of finishing cattle. The objective of this study was to investigate the effects of feeding ruminally protected and non-protected ADY to finishing beef steers on their fecal bacterial community. Fresh fecal samples were collected on day 56 from 50 steers fed one of five treatments: 1) control (no monensin, tylosin, or ADY), 2) antibiotics (ANT, 330 mg monensin + 110 mg tylosin·steer−1d−1), 3) ADY (1.5 g·steer−1d−1), 4) encapsulated ADY (EDY; 3 g·steer−1d−1), and 5) a mixture of ADY and EDY (MDY; 1.5 g ADY + 3 g EDY·steer−1d−1). Bacterial DNA was extracted from fecal samples and sequenced using a MiSeq high-throughput sequencing platform. A total number of 2,128,772 high-quality V4 16S rRNA sequences from 50 fecal samples were analyzed, and 1,424 operational taxonomic units (OTU) were detected based on 97% nucleotide sequence identity among reads, with 769 OTU shared across the five treatments. Alpha diversity indices, including species observed, Chao estimate, abundance-based coverage estimator, Shannon, Simpson, and coverage, did not differ among treatments, and principal coordinate analysis revealed a high similarity among treatments without independent distribution. Bacteroidetes and Firmicutes were dominant phyla in the fecal bacterial community for all treatments, with a tendency (P < 0.10) for greater relative abundance of Bacteroidetes but lesser Firmicutes with ANT, EDY, and MDY compared with control steers. Prevotella was the dominant genus in all treatments and steers supplemented with ANT, EDY, and MDY had greater (P < 0.05) relative abundance of Prevotella than control steers, but lesser (P < 0.03) relative abundance of Oscillospira. No differences between ADY and control were observed for the aforementioned variables. Fecal starch contents were not different among treatments, but the relative abundance of Bacteroidetes, as well as Prevotella at genera level, tended (P < 0.06) to be positively correlated to fecal starch content. We conclude that supplementing ruminally protected or non-protected ADY or ANT had no effect on diversity and richness of fecal bacteria of finishing beef cattle, whereas feeding protected ADY or ANT to finishing beef steers altered the dominant fecal bacteria at phylum and genus levels. Therefore, supplementation of ruminally protected ADY may potentially improve intestinal health by stimulating the relative abundance of Prevotella.

The objective of this study was to evaluate the effects of supplementing the diet of finishing beef steers with active dried yeast (ADY) in ruminally protected and nonprotected forms on growth performance, carcass traits, and immune response. Seventy-five individually-fed Angus steers (initial body weight (BW) ± SD, 448 ± 8.4 kg) were assigned to a randomized complete design with 5 treatments: 1) control (no monensin, tylosin, or ADY), 2) antibiotics (ANT, 330 mg monensin + 110 mg tylosin·steer-1d-1), 3) ADY (1.5 g·steer-1d-1), 4) encapsulated ADY (EDY; 3 g·steer-1d-1), and 5) a mixture of ADY and EDY (MDY; 1.5 g ADY + 3 g EDY·steer-1d-1). Active dried yeast with 1.7 × 1010 cfu/g was encapsulated in equal amounts of ADY and capsule materials (stearic acid and palm oil). Steers were fed a total mixed ration containing 10% barley silage and 90% barley-based concentrate mix (dry matter [DM] basis). The ANT, ADY, and EDY were top-dressed daily to the diet at feeding. Intake of DM, final BW, averaged daily gain (ADG), and gain-to-feed ratio (G:F) were unaffected by ADY or EDY. Carcass traits including hot carcass weight (HCW), dressing percentage, marbling score and quality grade did not differ among treatments, although fewer severely abscessed livers were observed (P < 0.05) with ADY and MDY compared with the other treatments. Plasma urea N tended (P < 0.10) to be greater in steers fed ANT, ADY, or EDY on day 56 and 112, while glucose remained stable in all treatments except greater (P < 0.02) plasma glucose occurred in steers fed MDY on day 112. Serum nonestrified fatty acid (NEFA) was unaffected by ADY or EDY, but it was greater (P < 0.03) in steers fed ANT compared with control. Plasma haptoglobin (Hp) and serum amyloid A (SAA) were affected by yeast supplementation on day 112, with greater (P < 0. 01) Hp in steers fed ADY, EDY, or MDY and lesser (P < 0.01) SAA in steers fed EDY and MDY than control. Lipopolysaccharide binding protein concentrations were greater (P < 0.01) in steers fed EDY and MDY on day 56. Supplementing with ADY (protected or nonprotected) or ANT had no effect on fecal IgA contents on day 56 and 112. Steers fed yeast (EDY or MDY) tended (P < 0.10) to have fewer fecal Escherichia coli counts than the control and ANT on day 56 and 112. These results indicate that feeding ADY to feedlot cattle may exhibit antipathogenic activity that conferred health and food safety beneficial effects including reduced liver abscess and potentially pathogen excretion, thus yeast may be an alternative to in-feed antibiotics in natural beef cattle production systems.

The objective of this study was to evaluate the addition of active dry Saccharomyces cerevisiae (yeast) to the diet of steers during the late finishing phase on performance, rumen pH and mRNA expression of genes relating to barrier function and immune response. 54 steers were blocked by weight and randomly assigned to one of two treatments: control (CON; n = 27) or yeast (fed at 60B CFU/hd/d; VistaCell, AB Vista, YST; n = 24). The corn-based finisher (60% high moisture corn, 20% dried distillers grains, and 17% alfalfa haylage, DM basis) ration was fed for 55± 15.9 days until slaughter. Every 28 days, weight and ultrasound of back and rump fat depths were recorded. Three to five days before slaughter, blood was collected via jugular venipuncture for measures of circulating metabolites, serum amyloid-A, and haptoglobin. Reticulo-rumen pH was recorded using an in-dwelling probe for 4 weeks leading up to slaughter. Rumen papillae were obtained for histological measurements, and to assess mRNA expression of genes related to gut barrier function (OCLN, CLDN, ZO1, ZO2) and immune response (TLR2, TLR4, FCAR). Data were analyzed as a complete randomized block design using PROC GLIMMIX in SAS, with treatment as a fixed effect, and block as a random effect. Feeding yeast in the late finisher diet decreased dry matter intake (11.97 and 8.24 ± 0.507 kg/day for CON and YST, respectively; P < 0.001) while maintaining average daily gains (P = 0.50), therefore improving feed conversion (P < 0.001) for YST steers. No differences were found between CON and YST steers for blood metabolites, including immune response markers (P ≥ 0.13), rumen mRNA expression (P ≥ 0.07), and rumen pH (P ≥ 0.08). Yeast addition to the late finishing diet significantly improved feed conversion through the decrease in dry matter intake without impacts on carcass quality or animal performance.

Abstract The objective of this study was to evaluate the effects of supplementing ruminally protected and non-protected active dried yeast (ADY; AB Vista, UK) on fecal bacterial diversity of finishing beef steers. Seventy-five Angus steers (initial BW 448 kg) were randomly assigned to one of five treatments: control, antibiotics (ANT, 330 mg monensin + 110 mg tylosin/d), ADY (1.5 g/d), encapsulated ADY (EDY; 3 g/d), and mixture of ADY and EDY (MDY). The ADY (1.7×1010 cfu/g) was encapsulated with equal amount of ADY and capsule material. Steers were fed a diet containing 10% barley silage and 90% barley concentrate (DM basis), ANT, ADY, EDY and MDY were top-dressed at feeding. Fecal samples were rectally collected from 10 steers of each treatment on d 56 to determine fecal bacterial diversity using high throughput MiSeq sequencing. Alpha diversity indices were not different among treatments. Principal coordinate analysis revealed that samples were not clustered by treatments. Bacteroidetes and Firmicutes were dominant phyla in the fecal bacterial community for all treatments, with a tendency (P < 0.10) of ANT, EDY and MDY to have greater relative abundance of Bacteroidetes (averaged 51.3 vs 46.8%) but lesser Firmicutes (averaged 39.5 vs 47.9%) than control steers. About 50 to 61% of sequences remained unclassified and identified 32 genus, with Prevotella ranging from 15.8 to 25.5% as the dominant genus in all treatments. Notably, steers with ANT, EDY, MDY vs. control had greater (P < 0.05) relative abundance of Prevotella (averaged 23.5 vs 16.8%) but lesser (P < 0.03) Oscillospira (averaged 1.7 vs 2.8%). No differences between ADY and control were observed for aforementioned variables. The results indicate that supplementing ruminally protected or non-protected ADY have limited effect on diversity of fecal bacteria, whereas feeding protected ADY and ANT to finishing beef steers altered dominant fecal bacteria at phylum and genus level.

Abstract The objective of this study was to examine if a fibrolytic enzyme feed additive would improve animal performance and apparent total tract digestibility of fibre in feedlot rations. To meet these objectives 54 steers were assigned to one of three pens by weight and fed a corn-based grower (78.7% corn-silage and 20% dried distillers grains plus solubles, DM basis) diet for 80 days, followed by a finisher diet (60% high moisture corn, 20% DDGS, and 17% alfalfa haylage, DM basis) for 60 days. Steers were randomly assigned to control (CON; n = 27) or enzyme (ENZ; n = 27) treatments, with ENZ steers receiving 0.75 ml/kg DM of the enzyme additive. Every 28 days body weight, ultrasound measures of back and rump fat depths were recorded, and blood was collected via jugular venipuncture. Ruminal pH was monitored using a reticulo-ruminal in-dwelling probe and recorded at five minutes intervals over three weeks each in the grower phase and through the transition. Apparent total tract digestibility was measured using acid-insoluble ash as an internal marker. Data were analyzed as a complete randomized block design using PROC GLIMMIX in SAS, with treatment as a fixed effect, and block as a random effect. Adding ENZ during the grower and early finisher phases did not impact (P ≥ 0.05) animal performance traits (gains, feed intake, feed conversion), blood metabolites, or ruminal pH in grower or finisher periods. However, ENZ significantly (P ≤ 0.05) improved digestibility of dry matter, crude protein, sugar, and net energy of gains. This study has demonstrated that the use of this fibrolytic enzyme in a corn-based feedlot diet improved digestibility of some nutrients, but this did not result in improved steer performance.

The objective of this study was to evaluate the effects of supplementing the diet of finishing beef steers with active dried yeast (ADY) in ruminally protected and nonprotected forms on growth performance, carcass traits, and immune response. Seventyfive individually-fed Angus steers (initial body weight (BW) ± SD, 448 ± 8.4 kg) were assigned to a randomized complete design with 5 treatments: 1) control (no monensin, tylosin, or ADY), 2) antibiotics (ANT, 330 mg monensin + 110 mg tylosin·steer...1d...1), 3) ADY (1.5 g·steer...1d...1), 4) encapsulated ADY (EDY; 3 g·steer...1d...1), and 5) a mixture of ADY and EDY (MDY; 1.5 g ADY + 3 g EDY·steer...1d...1). Active dried yeast with 1.7 ... 1010 cfu/g was encapsulated in equal amounts of ADY and capsule materials (stearic acid and palm oil). Steers were fed a total mixed ration containing 10% barley silage and 90% barley-based concentrate mix (dry matter [DM] basis). The ANT, ADY, and EDY were top-dressed daily to the diet at feeding. Intake of DM, final BW, averaged daily gain (ADG), and gain-to-feed ratio (G:F) were unaffected by ADY or EDY. Carcass traits including hot carcass weight (HCW), dressing percentage, marbling score and quality grade did not differ among treatments, although fewer severely abscessed livers were observed (P < 0.05) with ADY and MDY compared with the other treatments. Plasma urea N tended (P < 0.10) to be greater in steers fed ANT, ADY, or EDY on day 56 and 112, while glucose remained stable in all treatments except greater (P < 0.02) plasma glucose occurred in steers fed MDY on day 112. Serum nonestrified fatty acid (NEFA) was unaffected by ADY or EDY, but it was greater (P < 0.03) in steers fed ANT compared with control. Plasma haptoglobin (Hp) and serum amyloid A (SAA) were affected by yeast supplementation on day 112, with greater (P < 0. 01) Hp in steers fed ADY, EDY, or MDY and lesser (P < 0.01) SAA in steers fed EDY and MDY than control. Lipopolysaccharide binding protein concentrations were greater (P < 0.01) in steers fed EDY and MDY on day 56. Supplementing with ADY (protected or nonprotected) or ANT had no effect on fecal IgA contents on day 56 and 112. Steers fed yeast (EDY or MDY) tended (P < 0.10) to have fewer fecal Escherichia coli counts than the control and ANT on day 56 and 112. These results indicate that feeding ADY to feedlot cattle may exhibit antipathogenic activity that conferred health and food safety beneficial effects including reduced liver abscess and potentially pathogen excretion, thus yeast may be an alternative to in-feed antibiotics in natural beef cattle production systems.