Effect of wheat middling incorporation into wet corn distillers grains with solubles on apparent diet digestibility and ruminal fermentation characteristics in growing and finishing diets.

Two separate cross-over experiments were conducted to evaluate the effects of incorporating wheat middlings into wet corn distillers grains with solubles (WDGS) on apparent diet digestibility and ruminal fermentation characteristics in growing and finishing diets. In experiment 1, four ruminally cannulated heifers (313 ±â€…42.9 kg) were limit fed a high-energy growing diet that included WDGS (CON) or WDGS + wheat middlings (CON + WM) at 40% of diet dry matter (DM). The diet also contained (DM basis) 39.5% dry-rolled corn, 7.5% supplement, and 13% warm-season grass hay. In experiment 2, four ruminally cannulated Holstein steers (321 ±â€…17.4 kg) were fed a finishing diet that included WDGS (CON) or WDGS + wheat middlings (CON + WM) at 30% of diet DM. The diet also contained (DM basis) 60.3% dry-rolled corn, 2.7% supplement, and 7.0% warm-season grass hay. Experiments consisted of two 15-d periods that were conducted concurrently. Each period included 10 d of diet adaptation, 4 d of fecal collection, and 1 d of ruminal fluid collection. Fecal samples were collected on days 11 to 14 of each period and composite samples were analyzed for chromium to estimate apparent diet digestibility. On day 15, ruminal fluid samples were collected prior to feeding and again at 2, 4, 6, 8, 12, 18, and 24-h post-feeding. In experiment 1, DM, organic matter (OM), neutral detergent fiber (NDF), and acid detergent fiber (ADF) intake did not differ (P ≥ 0.11) between diets; however, starch intake was greater (P = 0.03) for heifers fed CON + WM compared with CON. Apparent DM, OM, NDF, and starch digestibilities were similar between diets (P ≥ 0.13), but feeding CON + WM tended to lead to lesser (P = 0.06) apparent ADF digestibility. Ruminal pH and total volatile fatty acid concentrations did not differ between diets (P ≥ 0.16); however, ruminal ammonia concentrations tended to be less (P = 0.09) for CON + WM compared with CON. In experiment 2, DM intake did not differ (P = 0.65) between diets. Apparent DM digestibility was greater (P = 0.01) for CON + WM compared with CON but the difference was small. Intake and apparent digestibility of OM, NDF, ADF, and starch did not differ (P ≥ 0.25) between diets. Ruminal ammonia concentrations were lesser (P = 0.03) while ruminal pH was greater (P = 0.02) for CON + WM compared with CON. Overall, incorporation of wheat middlings into WDGS had minimal impacts on feed intake, apparent diet digestibility, and ruminal fermentation characteristics when fed to growing and finishing cattle.

Impact of corn silage or corn silage plus protein supplementation on the ingestive and rumination behaviours, ruminal fermentation characteristics and efficiency of grazing dairy cows.

This study's objective was to compare two options of pasture supplementation: corn silage (CS) alone or corn silage mixed with protein concentrate. The experiment was conducted with 18 lactating Holstein cows in mid-lactation in a crossover design that included three treatments and three data collection periods. All cows had access to pasture for 17 h/day with an average herbage allowance of 16 kg dry matter (DM)/cow/day and were offered in-barn corn silage, corn silage mixed with protein concentrate, or no supplementation. Cows were equipped with pH sensors residing in the reticulum and, during the 7-day data collection periods, with a jaw movement recorder. Nonsupplemented cows produced 21.3 kg energy-corrected milk (ECM) and ate 13.3 kg DM herbage at pasture. Cows supplemented with corn silage and corn silage plus protein produced 2.5 and 4.5 kg/day more ECM, respectively, consumed 3.4 and 3.3 kg/day more DM in total, respectively, ate for a shorter period of time, and ruminated longer than their nonsupplemented peers. Supplemented cows were almost able to cover their energy requirements and mobilised less body mass in contrast to the nonsupplemented cows. Cows offered corn silage plus protein showed increased ECM production, increased milk urea content and lower nitrogen use efficiency (NUE) compared to cows supplemented with corn silage only. Nonsupplemented dairy cows had the highest milk urea content and performed worst in terms of NUE. The best feed conversion efficiency resulted from the nonsupplemented dairy cows and those supplemented with corn silage plus protein. In nonsupplemented cows, the high feed conversion efficiency seemed to be due to the increased mobilisation of body mass. As a result of the starch-rich supplementations, the ruminal acetic:propionic acid ratio became smaller, and the proportions of n-butyric acid increased. The mean reticular pH values did not substantially vary across the three feeding treatments. For the choice of a supplementation option, herbage allowance and cost of supplement will have to be considered, but aspects of feed-food competition as well as animal welfare should not be ignored.

Effects of supplemental zinc on growth, carcass characteristics, and liver abscess formation in steers with experimentally induced ruminal acidosis challenge.

The study's aim was to evaluate the effect of dietary Zn supplementation on steer performance, biomarkers of inflammation and metabolism, and liver abscess formation in response to a mild acidosis challenge. Forty-two steers (417 ± 3.99 kg; n = 6/pen) were housed in pens with bunks designed to measure individual dry matter intake (DMI) and fed one of two diets containing either 0 (CON; n = 18) or 90 mg Zn/kg from a Zn-amino acid complex (Zn-AA; n = 18; AvailaZn; Zinpro) for 109 d. Six additional steers were fed the CON diet and did not undergo the acidosis challenge (NON; n = 6). The acidosis challenge included restricting steers to 50% of the previous 7 d daily DMI on days 46 and 47, steers were individually provided 10% of DMI as cracked corn (as-fed) at 0800 h followed by ad libitum feed access 2 h post-grain consumption. Steer was the experimental unit, and two contrasts were constructed: NON vs. CON and CON vs. Zn-AA. Blood samples were collected on days 40, 48, 53, 69, 80, and 108 and analyzed as repeated measures. Final body weight and overall average daily gain (2.29, 2.30, and 2.31 ± 0.920 kg/d for CON, Zn-AA, and NON, respectively) were not different (P ≥ 0.74) between treatments. By design, DMI was greater (P < 0.01) for NON compared to CON on day 46 but was not different (P ≥ 0.41) for the rest of the experiment. While hot carcass weight (423, 428, and 424 ± 7.9 kg for CON, Zn-AA, and NON, respectively) and ribeye area were not different (P ≥ 0.53) due to treatment, marbling score tended (P = 0.06) to be greater in CON compared to Zn-AA. The 12th rib backfat thickness was greater (P = 0.05) in NON vs. CON steers. Liver abscess incidence tended to be greater (P = 0.12) in CON (24% abscesses) vs. Zn-AA (6% abscesses). NON had a greater incidence (P = 0.05; 50% abscesses) compared to CON. Overall, blood fibrinogen and leukocyte counts were not different between treatments (P ≥ 0.67); however, neutrophil-to-lymphocyte ratio tended to be greater in NON vs. CON (P = 0.08). Serum aspartate aminotransferase and gamma-glutamyl transferase concentrations were greater in NON vs. CON (P ≤ 0.02), and serum alkaline phosphatase concentration was lesser in CON vs. Zn-AA (P < 0.01). Overall, dietary Zn supplementation tended to lessen incidence of liver abscesses with limited impacts on overall cattle performance. Shifts in liver enzymes may represent opportunities to identify cattle with liver abscesses earlier in the feeding period.

The effects of antibiotic-free supplementation on the ruminal pH variability and methane emissions of beef cattle under the challenge of subacute ruminal acidosis (SARA).

Subacute ruminal acidosis (SARA) in feedlot cattle during the feed transition to grain-based diets is a significant constraint to animal health and productivity. This experiment assessed an antibiotic-free supplement (ProTect®) effects on ruminal pH variability and methane (CH4) emissions of cattle during the challenge of SARA. Ten 18-month-old Angus steers (472 ± 4.8 kg) were randomly allocated into monensin (n = 5) and ProTect® groups (n = 5) and progressively introduced to grain diets incorporating monensin or ProTect® for 36 days of the experiment [starter (7 days; 45% grain), T1 (7 days; 56% grain), T2 (7 days; 67% grain), finisher (15 days; 78% grain)]. The pH variability on the finisher period was reduced by the ProTect® supplement (6.6% vs. 5.2%; P < 0.01), with CH4 emissions being significantly higher relative to the monensin group [88.2 g/day (9.3 g CH4/kg DMI) vs. 133.7 g/day (14.1 g CH4/kg DMI); P < 0.01]. There was no difference between treatments in the time spent on the ruminal pH < 5.6 or < 5.8 (P > 0.05). The model evaluation for the ruminal pH variation indicated that the mean absolute error (MAE) proportion for both groups was good within the same range [4.05% (monensin) vs. 4.25% (ProTect®)] with identical root mean square prediction error (RMSPE) (0.34). It is concluded that the ProTect® supplement is an effective alternative to monensin for preventing SARA in feedlot cattle by managing ruminal pH variation during the transition to high-grain diets. Both monensin and ProTect® supplemented cattle exhibited lower CH4 yield compared to cattle fed forages and low-concentrate diets.

Systematic review of the relationship between rumen acidosis and laminitis in cattle.

Laminitis is usually considered a consequence of digestive disorders that reduce ruminal pH. However, it is still not clear the direct relation between low ruminal pH provoked by excessive fast-digesting carbohydrate ingestion and laminitis, considering indicators, signs, and diagnosis aspects. This study aimed to clarify the association between different clinical presentations of laminitis with ruminal acidosis provoked by diet using the systematic review methodology. Three electronic databases were used: ISI Web of Science, PubMed, and Scopus. A total of 339 manuscripts were identified and only 16 were included. Manuscripts were published between 2000 and 2021 in 11 different peer-reviewed journals. Fifteen studies confirmed the occurrence of ruminal acidosis. The main indicators used were ruminal pH and clinical signs, such as anorexia, depression, discomfort and diarrhea. Two of the studies that administered oligofructose to induce acidosis and acute laminitis did not observe clinical signs of laminitis, using lameness score or hooves' sensitivity as an indicator. Various diagnostic methods were used to describe laminitis, like thermography, hoof biopsy, sensitivity test, and visual inspection. Although the variety of laminitis indicators used in the included studies, we evidence the existence of an association between diet (high level of fast-digesting carbohydrates), ruminal acidosis, and acute laminitis, mostly in the short-term acidosis' induction protocols, but the mechanism of action is still not clear.

Nutrient intake, digestibility and ruminal characteristics of lambs supplemented with probiotic.

The aim of this study was to evaluate the inclusion of different levels of probiotic in the diets of lambs, on ruminal characteristics, intake and digestibility of nutrients. The treatments were 0 (control group), 2, 4 and 6 g/day of probiotic doses, supplied orally and individually to the lambs. Four crossbred Santa Inês X Texel lambs were used, and the experimental design was a Latin square, with four treatments and four periods. Samples of diet, orts, feces, and ruminal fluid were collected from each animal. Intake and apparent digestibility variables were not different (p > 0.05) among the levels of probiotic evaluated. The average daily feed intake of lambs ranged from 1.27 to 1.28 kg of DM/day, and no significant differences (p > 0.05) were obtained between the levels of probiotics used in the diet. The percentage distribution of protozoa was not significant according to the different doses of probiotics used. A positive linear effect was obtained between the pH of the rumen fluid and the probiotic used, indicating that the highest pH values were obtained when the animals received the higher dose of 6 g probiotic; indicative that its use provides a ruminal environment closer to neutrality. The methylene blue reduction test in ruminal fluid samples did not differ between the different doses of probiotics used. The increasing levels of the probiotic in the diet of lambs are related to an increase in ruminal pH, without changing the levels of intake and digestibility of nutrients.

Tropical grass silages with spineless cactus in diets of Holstein × Zebu heifers in the semiarid region of Brazil.

One of the factors that limit ruminant production in the semiarid region is the lack of roughage in the dry season. The management of forage plants adapted to edaphoclimatic conditions is a strategy to improve animal production. This study was conducted to examine the effects of biomass sorghum silage (BSS; Sorghum bicolor (L.) Moench) and BRS capiaçu grass silage (CGS; Pennisetum purpureum Schum) with or without spineless cactus (Opuntia spp.) in crossbred Holstein × Zebu heifers' diets on the intake, apparent digestibility of the nutrients and animal performance (e.g., final weight, daily weight gain) (experiment 1). Also, to evaluate the ruminal kinetics of dry matter (DM) and neutral detergent fiber (NDF) of roughages used in diets using two animals cannulated in the rumen (experiment 2). In experiment 1, ten heifers with an initial body weight of 200 ± 2.74 kg (mean ± standard deviation) and a mean age of 10 months were used. The animals were distributed in an experimental design in two simultaneous 5 × 5 Latin squares. Five experimental diets were used: diet 1, Volumax sorghum silage (VSS); diet 2, biomass sorghum silage (BSS); diet 3, BRS capiaçu silage (CGS); diet 4, biomass sorghum silage (60%) with spineless cactus (40%) (BSS + SC); and diet 5, BRS capiaçu grass silage (60%) with spineless cactus (40%) (CGS + SC). The diets were formulated with sorghum silage or BRS capiaçu grass silage with or without spineless cactus (roughage) and a maize- and soybean-based concentrate (75:25 roughage-to-concentrate ratio) on DM basis. The experiment lasted 105 days, divided into five periods of 21 days (17 days for the adaptation of the animals to the diets and management and 4 for data collection and samples). The diets containing CGS and CGS + SC resulted in lower dry matter intake (DMI; 5.61 kg day-1; P < 0.01), which was 19.4% lower than the diets with VSS, BSS, and BSS + SC (7.00 kg day-1). The BSS + SC and CGS + SC diets showed higher crude protein digestibility (P < 0.01) at 21.9% than the other treatments (Volumax, BSS, CGS). The different diets did not change the final weight or the daily weight gain of the heifers. The BRS 716 biomass sorghum silage and BRS capiaçu grass combined with spineless cactus increased (P < 0.05) the intake of nonfibrous carbohydrates and did not interfere (P > 0.05) with the final weight or average daily gain of the crossbred Holstein × Zebu heifers. The standardized potentially degradable fraction (Bp) of the NDF was 13.91% higher (P < 0.01) for BSS and BSS + SC (61.6%) compared to the others (53.0%). A diet based on BSS + SC is recommended for feeding crossbred heifers in the growing phase.

Parturition and postpartum dietary change altered ruminal pH and the predicted functions of rumen bacterial communities but did not alter the bacterial composition in Holstein cows.

We investigated the temporal dynamics of ruminal pH and the composition and predicted functions of the rumen bacterial community in Holstein cows during the periparturient period. Eight multiparous Holstein cows (body weight; 707.4 ± 29.9 kg, parity; 3.6 ± 0.6) were used for continuous reticulo-ruminal pH measurement, among which five were also used for bacterial community analysis. Rumen fluid samples were collected at 3 weeks before and 2 and 6 weeks after parturition, and blood samples were collected 3 weeks before and 0, 2, 4, and 6 weeks after parturition. After the parturition, reduction in the 1-h mean reticulo-ruminal pH was associated with a significant (P < 0.05) increase in total volatile fatty acid concentration. However, with the exception of a significant change in an unclassified genus of Prevotellaceae (P < 0.05), we detected no significant changes in the compositions of major bacterial phyla or genera or diversity indices during the periparturient period. On the basis of predicted functional analysis, we identified a total of 53 MetaCyc pathways (45 upregulated), 200 enzyme commissions (184 upregulated), and 714 Kyoto Encyclopedia of Genes and Genomes orthologs (667 upregulated) at 6 weeks postpartum that were significantly (P < 0.05) different to those at 3 weeks prepartum. Among the 14 MetaCyc pathways (P < 0.05) in which pyruvate is an end product, PWY-3661 [log2-fold change (FC) = 5.49, false discovery rate (FDR) corrected P < 0.001] was the most highly upregulated pyruvate-producing pathway. In addition, P381-PWY [adenosylcobalamin biosynthesis II (aerobic); FC = 5.48, FDR corrected P < 0.001] was the second most upregulated adenosylcobalamin (Vitamin B12)-producing pathway. In contrast, PWY-2221 (FC = -4.54, FDR corrected P = 0.003), predominantly found in pectinolytic bacteria, was the most downregulated pathway. Our findings indicate that changes in rumen bacterial community structure are not strictly associated with transitions in parturition or diet; however, we did observe changes in reticulo-ruminal pH and the metabolic adaptation of predicted functional pathways. Consequently, predictive analysis of postpartum functional pathways may enable us to gain insights into the underlying functional adaptations of bacterial communities in Holstein cows during the periparturient period.

Paraclinical Changes Occurring in Dairy Cows with Spontaneous Subacute Ruminal Acidosis under Field Conditions.

This study was undertaken to investigate the changes in the blood and milk biochemical parameters found in naturally occurring and long-lasting spontaneous subacute ruminal acidosis (SARA), with the aim of identifying the patterns of paraclinical changes and providing valuable data for more accurately identifying SARA in cows under field conditions. The study was conducted on a dairy herd with a history of the occurrence of SARA-associated clinical signs. Twelve cows, between 20 and 150 days in milk, were randomly selected and subsequently subjected to venous blood, milk, and ruminal fluid collection. The mean pH value of the ruminal fluid was 5.56 ± 0.32, and 58% (7/12) of the tested cows were SARA positive (ruminal pH ≤ 5.5). The albumin, calcium, and phosphorus serum concentration values were significantly lower (p < 0.05) in the SARA group than in the group of healthy cows. Serum aspartate aminotransferase (AST) and glutamate dehydrogenase (GLDH) activity were significantly higher in the SARA cows (p < 0.05) than in the group of healthy cows. The mean values of milk fat, milk protein content, and milk fat-to-protein ratio were significantly lower (p < 0.05) in the tested cows of the SARA group than in the healthy group of cows. In conclusion, the results of the current study indicate that long-term SARA triggered by a high-concentrate diet is associated with clinically significant changes in both the blood composition (hypoalbuminemia, hypocalcemia, and increased serum AST and GLDH activity) and the milk composition (decreased fat and protein percentage and milk fat-to-protein ratio). Altogether, the obtained results provide a more reliable pattern of paraclinical changes and useful insights for detecting SARA in dairy cows under field conditions.

Whole or coarsely broken açai seed as a source of roughage in the diet of feedlot cattle: intake, digestibility, and ruminal parameters.

This study was conducted to evaluate the effects of two methods of provision of açai seed (AS) as a fiber source (coarsely broken or whole) for feedlot beef cattle on the intake, digestibility, and ruminal parameters. Four bulls (male, non-castrated, and rumen fistulated), with an average body weight of 340 ± 31 kg, distributed in two simultaneous 2 × 2 Latin squares, were used. The treatments were two methods of processing of the açai seed, as follows: whole açai seed (WAS), and coarsely broken açai seed (CBAS). The dry matter (DM), crude protein (CP), and neutral detergent fiber (NDF) intake were higher (P < 0.10) with the use of CBAS. The digestibility of DM and nutrients was not affected (P > 0.10) by AS processing. Acetate and total volatile fatty acids concentrations, and acetate:propionate ratio were higher with the CBAS diet, whereas the pH was higher with the WAS diet. The concentrations of propionate, butyrate, and ruminal ammonia nitrogen (NH3) did not change with AS processing. Thus, coarsely broken açai seed increases the intake of DM and nutrients without altering the digestibility. Furthermore, it increases the concentrations of total fatty acids and acetate.

Impacts of added roughage on growth performance, digestibility, ruminal fermentation, and ruminal pH of feedlot steers fed wheat-based feedlot diets containing 30% modified distillers grains with solubles.

Two experiments were conducted to evaluate the inclusion rate roughage in wheat-based diets containing modified distillers grains with solubles (MDGS) on feedlot performance (Feedlot Experiment), as well as digestibility, ruminal pH, and ruminal fermentation characteristics (Digestibility Experiment). The feedlot experiment utilized 72 Angus steers (392 ± 46.3 kg initial body weight) which were randomly assigned to 1 of 12 pens, 3 pens per treatment, to evaluate feedlot performance and carcass characteristics. Dietary treatments were 1) control; 10% roughage, 2) 12% roughage, 3) 14% roughage, and 4) 16% roughage. The digestibility experiment used four ruminally and duodenally cannulated steers (393 ± 33.0 kg) in a 4 × 4 Latin Square with either 10%, 12%, 14%, or 16% roughage as in the feedlot experiment. However, dietary roughage source was different between these two experiments and included a combination of grass hay and wheat straw (Feedlot Experiment), and corn silage (Digestibility Experiment). All data were analyzed with the Mixed Procedures of SAS. Feed intake was recorded, with duodenal and fecal output calculated using chromic oxide. Ruminal pH and fermentation were assessed. Growth performance and most carcass characteristics were not affected by increasing roughage (P ≥ 0.11). Marbling tended to decrease linearly (P = 0.10) with increasing roughage inclusion. Increasing dietary roughage content had no effect on organic matter intake (P = 0.60) in the digestibility experiment. Intake, duodenal flow, and digestibility of neutral detergent fiber and acid detergent fiber were not affected by treatment (P ≥ 0.16). Ruminal pH increased linearly (P < 0.01) as rate of roughage inclusion increased. Ruminal concentrations of acetate and butyrate increased, and propionate decreased in a linear fashion (P < 0.01) thereby increasing (P < 0.01) acetate and butyrate to propionate ratio with increasing dietary roughage. Our data indicate that increasing roughage inclusion in wheat-based diets including 30% MDGS increased ruminal pH and shifted ruminal fermentation patterns. Additionally, increasing roughage inclusion did not affect feedlot performance in steers fed wheat at 36% to 42% of dietary dry matter in combination with 30% MDGS.

Interaction of replacing corn silage with soyhulls as a roughage source with or without 3% added wheat straw in the diet: impacts on intake, digestibility, and ruminal fermentation in steers fed high-concentrate diets.

Six ruminally cannulated steers [475.0 ± 49.6 kg initial body weight (BW)] were used in a 6 × 3 incomplete Latin square design (six treatments and three periods), to evaluate the impacts replacing of corn silage with pelleted soyhulls as roughage in high-concentrate finishing diets containing 30% modified distillers grains with solubles. Treatments were based on increasing dietary inclusion of soyhulls and consisted of: (1) Control (0), roughage supplied by dietary inclusion of 20% corn silage [dry matter (DM) basis]; (2) 50% replacement of corn silage with soyhulls (50); (3) 100% replacement of corn silage with soyhulls (100), and the same three treatments repeated with 3% added wheat straw (DM basis) replacing corn in the diet (0S, 50S, and 100S, respectively). Absolute dry matter intake (DMI; kg/d basis) tended to decrease both linearly and quadratically (P ≤ 0.09) and proportional DMI (% of BW) decreased linearly (P = 0.04) with increasing soyhull inclusion but was not affected by the addition of straw in the diet (P = 0.68). Total tract digestibility of organic matter and crude protein were not affected by soyhull inclusion or added straw (P ≥ 0.32). Ruminal pH did not differ (P = 0.65) with increasing soyhull inclusion but increased with the addition of straw (P < 0.01; 5.9 vs. 6.1 for no straw and straw, respectively). Molar proportions of acetate and butyrate decreased while propionate increased with increased soyhull inclusion (P ≤ 0.03; linearly and quadratically, respectively). Ruminal fluid kinetics were unaffected by either rate of replacement of corn silage with soyhulls or wheat straw inclusion (P ≥ 0.13). Decreases in DMI observed in this study would likely decrease finishing cattle performance and underscores the need for additional research before recommending this practice to cattle feeders.

Influence of feeding Saccharomyces cerevisiae on the heat load responses of lactating dairy cows during summer.

The objective of this study was to evaluate the influence of supplementing lactating dairy cows with Saccharomyces cerevisiae on milk production and composition, cow behavior, and physiological responses during summer. Twenty primiparous cows were used and two treatments were imposed: (1) control (CON); and (2) probiotic supplementation (PRO; S. cerevisiae, providing 1010 colony forming units (CFU) per day). Rumen temperature (TRUM, °C) and pH were obtained via rumen boluses. Rumen temperatures were obtained from all cows (n = 20) at 10-min intervals and ruminal pH were obtained from five cow pairs (n = 10) at 10-min intervals. Ambient temperature (TA; °C), relative humidity (RH; %), wind speed (WS; m/s), and solar radiation (SR; W/m2) were recorded at 10-min intervals. The temperature humidity index (THI) was calculated using TA and RH. Cows were milked twice daily. Milk fat (%), protein (%), lactose (%), and somatic cell count (SCC, '000) were evaluated on 16 occasions. Cows were observed three times (0800 h; 1200 h; and 1400 h) daily for panting score (PS); respiration rate (RR); posture (standing/lying); shade utilization; and cow activity (eating/drinking/ruminating). Individual PS were used to calculate a mean panting score (MPS) for CON and PRO treatments for each observation. S. cerevisiae did not influence milk yield (P = 0.87), fat (P = 0.82), protein (P = 0.26) or SCC (P = 0.19), although there was a tendency for PRO cows to have higher lactose (P = 0.06). Probiotics did not influence the proportion of cows utilizing shade (P = 0.42); standing (P = 0.41); ruminating (P = 0.72); or drinking (P = 0.40). All cows exhibited an increase in RR (> 24 bpm) at 1200 h and RR showed a steady increase as THI increased (P < 0.0001), regardless of treatment (P = 0.96). Both CON (35.8%) and PRO (40.2%) exhibited an increase in MPS as THI increased from thermoneutral (THI ≤ 74) to very hot (THI ≥ 84.1; P < 0.001). However, PRO cows had lower (2.19 ± 0.09; P < 0.0001) MPS compared with CON (2.54 ± 0.22) cows when THI was categorized as very hot (THI ≥ 84.1). Rumen pH were not influenced by treatment (P = 0.38), however TRUM of PRO cows were 0.2 °C lower across days (P < 0.0001) and hours (P < 0.0001). These results suggest that supplementing cows with S. cerevisiae may support thermoregulation via decreased TRUM and MPS; however, further studies are required.

A comparative analysis of rumen pH, milk production characteristics, and blood metabolites of Holstein cattle fed different forage levels for the establishment of objective indicators of the animal welfare certification standard.

OBJECTIVE: This study was conducted to obtain an objective index that can be quantified and used for establishing an animal welfare certification standard in Korea. For this purpose rumen pH, ruminating time, milk yield, milk quality, and blood components of cows reared in farms feeding high forage level (90%) and farms feeding low forage level (40%) were compared. METHODS: Data on rumen pH, rumination time, milk yield, milk fat ratio, milk protein ratio, and blood metabolism were collected from 12 heads from a welfare farm (forage rate 88.5%) and 13 heads from a conventional farm (forage rate 34.5%) for three days in October 2019. RESULTS: The rumination time was longer in cattle on the welfare farm than on the conventional farm (p<0.01), but ruminal pH fluctuation was greater in the cattle on conventional farm than the welfare farm (p<0.01). Conventional farms with a high ratio of concentrated feed were higher in average daily milk yield than welfare farms, but milk fat and milk production efficiency (milk fat and milk protein corrected milk/total digestible nutrients) was higher in cattle on welfare farms. Blood test results showed a normal range for both farm types, but concentrations of total cholesterol and non-esterified fatty acid were significantly higher in cows from conventional farms with a high milk yield (p<0.01). CONCLUSION: The results of this study confirmed that cows on the animal welfare farm with a high percentage of grass feed had higher milk production efficiency with healthier rumen pH and blood metabolism parameters compared to those on the conventional farm.

Effect of Mineral Salt Blocks Containing Sodium Bicarbonate or Selenium on Ruminal pH, Rumen Fermentation and Milk Production and Composition in Crossbred Dairy Cows.

Ruminal pH is an important physiological parameter that regulates microbe activity; optimizing ruminal pH may improve rumen fermentation and milk production. The purpose of this experiment was to determine the effect of sodium bicarbonate (NaHCO3) or selenium (Se) in mineral salt block (MSB) supplementation on ruminal pH, rumen fermentation, milk yield and composition in Holstein Friesian crossbred dairy cows. Four crossbred dairy cows with an initial weight of 456 ± 6 kg in mid-lactation were assigned at random using a 4 × 4 Latin square design. The experiments were divided into four periods, each lasting 21 days. Each cow was fed a basal diet supplemented with a different type of mineral salt block: a control with no MSB supplementation, and MSB groups with MSB containing NaHCO3 (MSB-Na), MSB containing Se (MSB-Se), and conventional commercial MSB (MSB-Com). MSB-Na contained NaHCO3 (500 g/kg) to prevent acidosis, MSB-Se contained organic Se (15 mg/kg) as an antioxidant, and MSB-Com was a positive control mineral salt block. The results show that there was no significant difference in feed intake between treatments, but there was a significant difference in mineral salt intake between treatments (p < 0.05). Supplementing mineral blocks had no effect on nutrient intake or apparent digestibility (p > 0.05). Ruminal pH was not different between treatments at 0 and 1 h post-feeding, but at 2 and 4 h post-feeding, ruminal pH in cows fed MSB-Na and MSB-Se was significantly higher (p < 0.05) than it was in cows fed MSB-Com and the control. Total volatile fatty acid (VFA), acetic, propionic, butyric, and ammonia nitrogen and blood urea nitrogen were not influenced by mineral blocks supplementation. Milk yield, milk composition and energy-corrected milk (ECM) were not affected by supplementing mineral blocks. However, compared with the control, the somatic cell count (SCC) in the milk was reduced (p < 0.05) by supplementation with the mineral salt block. Based on the results of the experiments, it was concluded that MSB-Na or MSB-Se supplementation improved ruminal pH while having no effect on feed intake, rumen fermentation, milk yield, or composition, though it did reduce SCC in milk. However, additional research should be conducted to investigate the effect of MSB on rumen ecology and milk production in dairy cows fed a high-concentrate diet.

Pellets Inoculated with Bacillus amyloliquefaciens H57 Modulates Diet Preference and Rumen Factors Associated with Appetite Regulation in Steers.

This study examined whether the probiotic Bacillus amyloliquefaciens strain H57 (H57) affects ruminal fermentation parameters that exercise post-ingestive feedback appetite control mechanisms. A 4 × 4 Latin square design was used to separate pre- and post-ingestive effects of H57 in four rumen-fistulated steers. The steers were offered a set amount of feedlot pellets, inoculated with H57 or without H57 (control, C). Half of the total amount of pellets fed were introduced intra-ruminally (r), and then the remaining pellets were orally consumed (o) to make four feeding treatments: H57r/H57o, H57r/Co, Cr/H57o and Cr/Co. Rumen fluid was sampled at 2, 4 and 6 h after feeding. Preference behaviour was tested immediately after the 6 h rumen fluid sampling by simultaneously offering the steers 4 kg of each of H57 and C pellets in adjacent troughs for 5 min. Steers preferred the pellets with added H57 over the C pellets (56:44; p < 0.001) and their preferences were not affected by the treatment protocol imposed to separate post- from pre-ingestive effects (p > 0.05). Steers fed H57 pellets had higher ruminal pH, molar proportions of iso-butyrate and iso-valerate (p < 0.05) and tended to have greater ruminal ammonia concentrations compared to those fed C pellets (p < 0.1). However, post-ingestive signals did not affect diet preference more than pre-ingestive signals.

Prior Forage Type Influences Ruminal Responses to a Wheat Grain Challenge in Lactating Dairy Cows.

To increase the dry matter and metabolisable energy intake of cows, dairy farmers often supplement pasture with concentrates and conserved fodder. Feeding large amounts of highly fermentable concentrates to cows can result in metabolic issues, such as ruminal acidosis, and thus safer but more efficient introduction strategies are desirable. We assessed the role that forages play in ruminal, behavioural and production responses to a wheat grain challenge in dairy cows with no previous wheat adaptation. Multiparous lactating Holstein dairy cows (n = 16) were fed a forage-only diet of either lucerne (Medicago sativa) hay, perennial ryegrass (Lolium perenne L.) hay or one of two cultivars of zero-grazing fresh perennial ryegrass herbage (Bealey or Base), for 3 weeks. The forage diet was then supplemented with crushed wheat grain at 8 kg dry matter/cow day-1, with no adaptation period. Wheat comprised between 32 and 43% of total dry matter intake. Cows fed hay maintained a higher mean ruminal fluid pH than those fed herbage, on both the forage-only diet (6.43 vs. 6.17) and the forage plus wheat diet (6.03 vs. 5.58). Following supplementation of wheat, cows fed herbage exhibited minimum ruminal fluid pH levels indicative of acute ruminal acidosis, at 5.15 and 5.06 for cultivars Bealey and Base, respectively. Furthermore, for both herbage cultivars, adding wheat resulted in a ruminal fluid pH under 6 for >20 h/day. The ruminal environment of cows fed lucerne hay remained most stable throughout the grain challenge, spending the least amount of time below pH 6.0 (9.0 h/day). Hay created a ruminal environment that was better able to cope with the accumulation of acid as wheat was digested. A combination of increased ruminating time and a slower rate of fermentation, due to higher neutral detergent fiber and lower metabolisable energy concentrations in the hays, is likely responsible for the higher ruminal fluid pH values. Forage plays a critical role in wheat introduction strategies; aggressive adaptation strategies could be implemented when a hay such as lucerne is used as the base forage.

Diurnal Ruminal pH and Temperature Patterns of Steers Fed Corn or Barley-Based Finishing Diets.

This study evaluated the effects of corn or barley finishing diets on ruminal pH and temperature and their relationship to feed intake events using continuous reticulorumen monitoring of feedlot steers. Average daily ruminal pH and temperature were not impacted (p ≥ 0.17) by diet. However, diet did affect daily variation of ruminal pH and temperature (p < 0.01). Average hourly ruminal pH displayed a diet by hour post-feeding interaction (p < 0.01), where barley-fed steers had greater (p < 0.01) ruminal pH than corn-fed steers at 0, 1, 18, 19, 20, 21, 22 and 23 h post feeding, but had lower (p ≤ 0.05) ruminal pH than corn-fed steers at 6, 7, and 8 h post-feeding. Variation in ruminal pH hour post-feeding also displayed a diet by hour post-feeding interaction (p < 0.01), where barley-fed steers had greater (p ≤ 0.03) variation in ruminal pH at hours 1-17 post-feeding but did not differ (p ≥ 0.16) at 0, 18, 19, 20, 21, 22 and 23 h post-feeding. Additionally, average hourly ruminal temperature exhibited a diet by hour post-feeding interaction (p < 0.01). In summary, basal grain interacted with time post-feeding influencing ruminal pH and temperature in feedlot steers.

Increasing dietary proportion of wheat grain in finishing diets containing distillers' grains: impact on nitrogen utilization, ruminal pH, and digestive function.

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.

Technical Note: The comparison of pH and redox potential in different locations in the reticulo-rumen of growing beef steers supplemented with different levels of quebracho extract.

Rumen acidosis is a common metabolic disorder occurring when organic acid production exceeds clearance capacity, reducing ruminal pH. The occurrence of acidosis has been directly correlated to the ratio of concentrate to forage in the diet. However, rates of substrate fermentation and acid absorption vary at different locations in the reticulo-rumen. The objective of this study was to determine the pH and redox potential (Eh) in different locations of the reticulo-rumen using 16 ruminally cannulated steers (309 ± 43 kg) receiving different supplementation levels of quebracho extract (QT; Schinopsis balansae) within a grower type diet (CP: 13.4%; total digestible nutrients [TDN]: 70.4%; and ME: 2.55 Mcal/kg, dry matter [DM] basis). Animals were randomly assigned to one of four dietary treatments: QT at 0%, 1%, 2%, and 3% of DM (QT0, QT1, QT2, and QT3, respectively), containing about 0%, 0.7%, 1.4%, and 2.1% of condensed tannins (CT), DM basis, respectively. Animals were adapted to the basal diet for 12 d before being introduced to predetermined treatments for 4 weeks (wk), with diets provided twice daily to allow ad libitum intake. Weekly measurements of ruminal fluid pH and Eh were taken 4 h post-feeding using a portable pH meter with two probes (pH and redox) in four locations of the reticulo-rumen (reticulum, cranial sac, dorsal sac, and ventral sac). Data were analyzed using a random coefficients model with the pen as a random effect and wk as repeated measures, with DM intake included as a covariate. There was no interaction among treatments, location, and wk (P ≥ 0.882) on reticulo-ruminal pH. Overall, ruminal pH was lower for QT0 and QT1 compared to QT3 (P < 0.001). The pH in the reticulum was greater than those of the ventral and dorsal sacs (6.05 vs. 5.94, 5.89, respectively; P ≤ 0.001) but similar to cranial sac (6.00). Reticular pH was positively correlated with the ruminal locations (≥0.78; P < 0.001). The linear equation to estimate ruminal mean pH using reticulum pH had an intercept and slope different from zero (P ≤ 0.04), but CT (% DM) was not different from zero (P = 0.15), root mean square error of 0.15, and R2 of 0.778: 0.723 (±0.36) + 0.857 (±0.059) × reticulum pH + 0.033 (±0.023) × CT. The Eh was lower for QT0 in week 1 than all other treatments (P < 0.001). We concluded that reticulo-ruminal pH differs among locations in the rumen regardless of QT supplementation level and days on feed, with reticular pH being the highest.