Fecal microbial gene transfer contributes to the high-grain diet-induced augmentation of aminoglycoside resistance in dairy cattle

A high-grain (HG) diet can rapidly lower the rumen pH and thus modify the gastrointestinal microbiome in dairy cattle. Although the prevalence of antibiotic resistance is strongly linked with the gut microbiome, the influences of HG diet on animals' gut resistome remain largely unexplored. Here, we examined the impact and mechanism of an HG diet on the fecal resistome in dairy cattle by metagenomically characterizing the gut microbiome. Eight lactating Holstein cattle were randomly allocated into two groups and fed either a conventional (CON) or HG diet for 3 weeks. The fecal microbiome and resistome were significantly altered in dairy cattle from HG, demonstrating an adaptive response that peaks at day 14 after the dietary transition. Importantly, we determined that feeding an HG diet specifically elevated the prevalence of resistance to aminoglycosides (0.11 vs 0.24 RPKG, P < 0.05). This diet-induced resistance increase is interrelated with the disproportional propagation of microbes in Lachnospiraceae, indicating a potential reservoir of aminoglycosides resistance. We further showed that the prevalence of acquired resistance genes was also modified by introducing a different diet, likely due to the augmented frequency of lateral gene transfer (LGT) in microbes (CON vs HG: 254 vs 287 taxa) such as Lachnospiraceae. Consequently, we present that diet transition is associated with fecal resistome modification in dairy cattle and an HG diet specifically enriched aminoglycosides resistance that is likely by stimulating microbial LGT.IMPORTANCEThe increasing prevalence of antimicrobial resistance is one of the most severe threats to public health, and developing novel mitigation strategies deserves our top priority. High-grain (HG) diet is commonly applied in dairy cattle to enhance animals' performance to produce more high-quality milk. We present that despite such benefits, the application of an HG diet is correlated with an elevated prevalence of resistance to aminoglycosides, and this is a combined effect of the expansion of antibiotic-resistant bacteria and increased frequency of lateral gene transfer in the fecal microbiome of dairy cattle. Our results provided new knowledge in a typically ignored area by showing an unexpected enrichment of antibiotic resistance under an HG diet. Importantly, our findings laid the foundation for designing potential dietary intervention strategies to lower the prevalence of antibiotic resistance in dairy production.

Effect of a molasses-based liquid supplement on gastrointestinal tract barrier function, inflammation, and performance of newly received feedlot cattle before and after a transport stress

The objective of this study was to determine the effect of a dry versus a molasses-based liquid supplement on ruminal butyrate concentration, gastrointestinal tract (GIT) barrier function, inflammatory status, and performance of newly received feedlot cattle. In experiment 1, 60 mixed breed steers (234 ± 2.1 kg) were weaned, held overnight at a sale barn, then transported 14 h to Purdue University. After arrival, steers were weighed, blocked by body weight, and allotted within block to treatments (six pens per treatment and five steers per pen). Diets consisted of 45% roughage and 55% concentrate (dry matter basis). Treatments differed in the supplement source as follows: DRY: 10% dry supplement or LIQUID: 10% liquid molasses-based supplement. Feed intake, average daily gain (ADG), and gain:feed were determined for the three 21-d periods and overall. In experiment 2, 16 crossbred heifers (246 ± 7.5 kg) were used (8 heifers per treatment). Diets were the same as in experiment 1 and were fed for 60 d. On d 56 ruminal fluid samples were collected at 0, 3, 6, and 9 h after feeding. To mimic a stress event, heifers were transported for 4 h on d 61, rested overnight, and transported 12 h on d 62. Blood was collected from heifers immediately prior to transport and immediately upon their return. Gut barrier function using a Cr-EDTA marker was determined after transportation. Data were analyzed using the GLIMMIX procedure of SAS. Steers fed the liquid supplement had greater (P ≤ 0.03) ADG through d 42 and overall compared to steers fed the dry supplement. Feed intake did not differ (P = 0.25) between treatments from d 0 to d 21. However, steers fed the liquid supplement showed greater (P < 0.001) dry matter intake after d 21 and overall compared to those fed the dry supplement. Steers fed the liquid supplement tended (P < 0.09) to have reduced serum haptoglobin and lipopolysaccharide-binding protein (LBP) compared to those fed the dry supplement. Heifers fed the liquid supplement had greater (P = 0.02) Cr in urine and tended (P = 0.07) to have lower serum LBP after transport compared to those fed the dry supplement. Heifers fed the liquid supplement had 72% lower serum haptoglobin before, but only a 19% lower serum haptoglobin after transport compared to animals fed the dry supplement (treatment × time; P = 0.07). Therefore, the liquid supplement altered GIT barrier function, and improved inflammatory status, resulting in increased growth of receiving cattle.

Granulated Cane Sugar as a Partial Replacement for Steam-Flaked Corn in Diets for Feedlot Cattle: Ruminal Fermentation and Microbial Protein Synthesis

The aim of this study was to evaluate the influence of supplemental granulated cane sugar (GCS) levels (0, 13.3, 26.6, and 39.9% on a dry matter basis) in a steam-flaked corn-based finishing diet on measures of ruminal fermentation and the site and extent of nutrient digestion. Four Holstein steers (251 ± 3.6 kg live weight) with “T” type cannulas in the rumen and proximal duodenum were used in a 4 × 4 Latin square experiment to evaluate the treatments. The experiment lasted 84 d. Replacing steam-flaked corn (SFC) with GCS linearly decreased the flow of ammonia-N (NH3-N) to the small intestine, increasing the flow of microbial nitrogen (MN; quadratic effect, p = 0.02), ruminal N efficiency (linear effect, p = 0.03) and MN efficiency (quadratic effect, p = 0.04). The ruminal digestion of starch and neutral detergent fiber (NDF) decreased (linear effect, p ≤ 0.02) as the level of GCS increased. The postruminal digestion of organic matter (OM), neutral detergent fiber (NDF), and starch were not affected by the GCS inclusion. However, postruminal N digestion decreased (linear effect, p = 0.02) as the level of GCS increased. There were no treatment effects on total tract OM digestion. However, total tract NDF and N digestion decreased (linear effect, p ≤ 0.02) as the level of GCS increased. The ruminal pH decreased (linear effect, p < 0.01) as the GCS increased in the diet. The ruminal acetate molar proportion decreased (linear effect, p = 0.02) and the ruminal valerate molar proportion tended to increase (linear effect, p = 0.08) as the level of GCS increased. It is concluded that replacing as much as 13% of SFC with GCS in a finishing diet will enhance the efficiency of N utilization (g non-ammonia-N entering the small intestine/g N intake) without detrimental effects on total tract OM digestion. The inclusion of GCS decreased the ruminal proportion of acetate linearly without an effect on the acetate-to-propionate ratio or estimated methane production. Some of the effects on N utilization at a high level of GCS inclusion (27 and 40%) can be magnified by the differences in the CP content between diets. A higher level of GCS supplementation in the diet decreased the ruminal pH below 5.5, increasing the risk of ruminal acidosis.

Dry malt extract from barley partially replacing ground corn in diets of dairy cows: Nutrient digestibility, ruminal fermentation, and milk composition

Dry malt extract (DME) has been used in animal nutrition as an alternative source of rapidly fermentable carbohydrate. An experiment was conducted to evaluate the partial replacement of ground corn with DME in diets of dairy cows on apparent digestibility, ruminal fermentation, predicted rumen microbial protein supply, N excretion, serum urea-N concentration, and milk yield and composition. Twenty-eight Holstein cows (35.3 ± 5.88 kg/d milk yield and 148 ± 78 d in milk), 4 of which were rumen cannulated, were blocked according to the presence of rumen cannulas, parity, milk yield, and days in milk and enrolled into a crossover design experiment. Experimental periods lasted 21 d, of which the first 14 d were allowed for treatment adaptation and 7 d were used for data collection and sampling. Treatment sequences were composed of control (CON) or DME from barley (Liotécnica Tecnologia em Alimentos) replacing ground corn at 7.62% diet dry matter (∼2 kg/d). Data were analyzed using the MIXED procedure of SAS (SAS Institute Inc.) modeling the fixed effects of treatment, period, and their interaction, in addition to the random effect of animal. Ruminal fermentation data were analyzed as repeated measures including time and its interaction with treatment in the previous model as fixed effects. Treatments did not affect nutrient intake or feed sorting. Dry malt extract increased apparent digestibility of CP. Feeding DME decreased ruminal pH and molar percentage of butyrate and increased molar percentage of acetate. No treatment effects were detected for predicted rumen microbial protein supply or N excretion. Cows fed DME had lower serum urea-N concentration than CON cows. Dry malt extract increased yields of actual milk, 3.5% fat-corrected milk, fat, and protein, and improved feed efficiency (fat-corrected milk ÷ dry matter intake). Cows fed DME had lower milk urea nitrogen content in comparison with CON cows. Dry malt extract can partially replace ground corn in the diet while improving milk yield and feed efficiency.

A review on the potentials of using feeds rich in water-soluble carbohydrates to enhance rumen health and sustainability of dairy cattle production

Cows are adapted to degrade structural plant carbohydrates (SC), such as cellulose and hemicelluloses, prevailing in grasses. Yet, the need for energy-dense diets in many intensive dairy production systems has shifted the dairy cattle's diet from SC-rich to high levels of starch. Feeding of starch-rich diets increases the risk of ruminal acidosis in cows, and feeding starch in the form of grains intensifies the competition over cereal grains and arable land among different livestock species, as well as between livestock and humans. Besides cellulose and hemicelluloses, grasses are also often rich in water-soluble carbohydrates (WSC), which comprise mono-, di-, oligo- and polysaccharides (fructans). Although the ruminal fermentation profile of mono- and disaccharides resembles that of starch, the degradation of oligo- and polysaccharides is slower, and their fermentation elicits a rather protecting effect on ruminal pH. When harvested in an early phase (i.e. ear emergence), grass hay and silages can reach WSC levels up to 150-200 g kg^-1 dry matter and energy levels close to starch-rich diets, allowing a significantly reduced inclusion of concentrate supplements. By doing so, this will enhance both rumen health and the sustainability of milk production. However, because the WSC are chemically very heterogeneous, the patterns and extent of their ruminal fermentation are difficult to predict without a clear analytical characterization. This review article aims to summarize both the benefits and potentials, as well as the challenges, with respect to using WSC-rich feedstuffs in the nutrition of dairy cattle and their effects on ruminal fermentation characteristics and milk production. © 2021 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Comparison of milk production, intake, and total-tract nutrient digestion in lactating dairy cattle fed diets containing either wheat middlings and urea, commercial fermentation by-product, or rumen-protected soybean meal

The objective of this study was to evaluate the effects of a commercially available fermentation by-product in a diet containing adequate rumen-degradable protein (RDP) on milk performance, intake, and total-tract nutrient digestion in lactating dairy cattle. Primiparous (n = 48) and multiparous (n = 144) lactating dairy cattle were stratified by milk production and randomly allocated into 12 pens containing 4 primiparous and 12 multiparous animals each. Cattle averaged 118 d in milk and 712 kg of body weight at trial start. Treatment diets, on a dry matter (DM) basis, consisted of 42% corn silage, 13% alfalfa hay and silage, 20% grain corn, and 25% protein premix containing either soybean meal, wheat middlings, and urea (SBM+U), soybean meal and fermentation by-product (SBM+F), or soybean meal and rumen-protected soybean meal (RP-SBM). All 3 diets provided a similar level (DM basis) of neutral detergent fiber analyzed using α-amylase and sodium sulfite and corrected for ash content (31%), crude protein (CP, 14.9%), starch (26%), and metabolizable energy (2.7 Mcal/kg), and differed in sources of RDP. The trial consisted of a 2-wk adaptation and covariate period during which all cows were fed the RP-SBM diet and covariate measurements were taken. Pens were then randomly allocated to treatments, and weekly measurements of milk production, intake, body weight, and condition score were taken for 10 wk. All data were analyzed using the Proc Mixed procedure in SAS (SAS Institute Inc., Cary, NC). Increased DM intake was observed for cows fed SBM+F compared with cows fed SBM+U and RP-SBM (28.3 vs. 26.9 and 26.7 kg/d, respectively). Cows fed SBM+F produced more energy-corrected milk (45.3 kg/d) compared with cows fed SBM+U and RP-SBM (43.6 and 43.7 kg/d, respectively). Milk protein yield was also increased in cows fed SBM+F. No differences were observed with body weight or condition score gain throughout the trial. Apparent total-tract digestibility of fiber was decreased in cows fed SBM+F, likely as a result of increased intake. Responses are consistent with previous research in our laboratory that demonstrated a decrease in ruminal CP degradation, leading to an increase in metabolizable protein supply in the small intestine. The fermentation by-product might be useful in diets containing adequate amounts of RDP from soybean meal or alfalfa. The results from this experiment demonstrate beneficial milk performance responses to fermentation by-product when fed with a source of RDP.

Contrasting effects of high-starch and high-sugar diets on ruminal function in cattle

The experiment reported in this research paper aimed to determine whether clinical and subclinical effects on cattle were similar if provided with isoenergetic and isonitrogenous challenge diets in which carbohydrate sources were predominantly starch or sugar. The study was a 3 × 3 Latin square using six adult Jersey cows with rumen cannulae, over 9 weeks. In the first 2 weeks of each 3 week experimental period cows were fed with a maintenance diet and, in the last week, each animal was assigned to one of three diets: a control diet (CON), being a continuation of the maintenance diet; a high starch (HSt) or a high sugar (HSu) diet. Reticuloruminal pH and motility were recorded throughout the study period. Blood and ruminal samples were taken on day-1 (TP-1), day-2 (TP-2) and day-7 (TP-7) of each challenge week. Four clinical variables were recorded daily: diarrhoea, inappetence, depression and ruminal tympany. The effects of treatment, hour of day and day after treatment on clinical parameters were analysed using linear mixed effects (LME) models. Although both challenge diets resulted in a decline in pH, an increase in the absolute pH residuals and an increase in the number of minutes per day under pH 5.8, systemic inflammation was only detected with the HSt diet. The challenge diets differentially modified amplitude and period of reticuloruminal contractions compared with CON diet and both were associated with an increased probability of diarrhoea. The HSu diet reduced the probability of an animal consuming its complete allocation. Because the challenge diets were derived from complex natural materials (barley and molasses respectively), it is not possible to assign all the differential effects to the difference in starch and sugar concentration: non-starch components of barley or non-sugar components of molasses might have contributed to some of the observations. In conclusion, substituting much of the starch with sugar caused no substantial reduction in the acidosis load, but inflammatory response was reduced while feed rejection was increased.

Effects of replacing starch with three sugars in a concentrate and forage diet on in vitro rumen fermentation, fatty acid composition and related bacteria

Context Replacing starch with sugar could maintain dietary energy density with reduced risks of rumen acidosis and milk fat depression, but the underlying mechanism is not well understood, and the effects of sugar feeding might vary among sugars. Aims Objectives of the present study were to evaluate the effects of replacing corn starch in a diet containing 40:60 forage-to-concentrate ratio (control) with 3%, 6% and 9% of sucrose, fructose and lactose on in vitro rumen fermentation, fatty acid (FA) composition and populations of bacteria involved in the production of trans-11 and trans-10 FA. Methods A 3 × 3 + 1 (control) factorial experimental design was used, and the pH, concentrations of volatile fatty acids (VFA) and ammonia-N, profiles of FA and the relative abundance of four trans-11-producing bacteria and two trans-10 FA-producing bacteria were measured after a 6-h incubation. Key results Replacing dietary corn starch with sucrose, fructose and lactose neither altered the concentration of total VFA after 6-h fermentation, nor decreased the pH, except for substitution with 9% sucrose. Increased butyrate proportions and decreased branched-chain VFA proportions were the common effects in sugar treatments, but the proportions of acetate and propionate varied among sugars. Lactose inclusion in the diet led to a higher pH, greater acetate and butyrate concentrations, and lower propionate concentrations than did sucrose inclusion. Sugar substitution decreased the concentrations of C18:1 trans-4 and most C18:2 isomers, but did not influence the major isomers related to trans-11 and trans-10 biohydrogenation pathways. Abundance of the four measured trans-11 FA-producing bacteria was increased by sugars, with sucrose showing a greater influence than did fructose and lactose. As to trans-10 FA-producing bacteria, only Megasphaera elsdenii populations were decreased by 3% and 6% fructose inclusion compared with the control. Dose-effect varied among sugars and the parameters measured, with sucrose having the most obvious dose effect among the three sugars; however, fructose affected mainly fermentation parameters, while lactose affected mainly C18 FA profiles. Conclusions Replacing corn starch in a high-concentrate diet with up to 9% of sucrose, fructose and lactose differentially affected rumen fermentation and rumen FA metabolism, by influencing the abundance of rumen bacteria involved in rumen FA biohydrogenation. Implications Lactose may be more efficient in increasing milk fat than are sucrose and fructose, and dose effect should be considered in the utilisation of sucrose.

Symposium review: Decomposing efficiency of milk production and maximizing profit

The dairy industry has focused on maximizing milk yield, as it is believed that this maximizes profit mainly through dilution of maintenance costs. Efficiency of milk production has received, until recently, considerably less attention. The most common method to determine biological efficiency of milk production is feed efficiency (FE), which is defined as the amount of milk produced relative to the amount of nutrients consumed. Economic efficiency is best measured as income over feed cost or gross margin obtained from feed investments. Feed efficiency is affected by a myriad of factors, but overall they could be clustered as follows: (1) physiological status of the cow (e.g., age, state of lactation, health, level of production, environmental conditions), (2) digestive function (e.g., feeding behavior, passage rate, rumen fermentation, rumen and hindgut microbiome), (3) metabolic partitioning (e.g., homeorhesis, insulin sensitivity, hormonal profile), (4) genetics (ultimately dictating the 2 previous aspects), and (5) nutrition (e.g., ration formulation, nutrient balance). Over the years, energy requirements for maintenance seem to have progressively increased, but efficiency of overall nutrient use for milk production has also increased due to dilution of nutrient requirements for maintenance. However, empirical evidence from the literature suggests that marginal increases in milk require progressively greater marginal increases in nutrient supply. Thus, the dilution of maintenance requirements associated with increases in production is partially overcome by a progressive diminishing marginal biological response to incremental energy and protein supplies. Because FE follows the law of diminishing returns, and because marginal feed costs increase progressively with milk production, profits associated with improving milk yield might, in some cases, be considerably lower than expected.

Mesquite pod meal as an additive increases milk total solids, lactose, fat and protein content in dairy cows

The objective was to evaluate the intake, digestibility, milk yield and composition of cows fed mesquite pod meal (MPM). Five crossbred dairy cows, with an average body weight of 450 ± 5 kg and producing 10 ± 1 kg of milk/day were distributed in a 5 × 5 Latin square arrangement with five periods of 20 days each, comprised of 15 days for adaptation to the experimental diets (T1 = 0%, T2 = 1.5%, T3 = 3.0%, T4 = 4.5% and T5 = 6.0% MPM) and 5 days for data collection. Variables were assessed by analysis of variance and regression at P < 0.01 and P < 0.05 of significance, using the Student's test. Animals were kept on pastures and the concentrates were provided at 6 kg/animal divided in two meals per day. The inclusion of 3.0% mesquite pod meal did not affect the intake, digestibility of nutrients and milk yield, but it changed milk composition. The dietary inclusion of 3.0% mesquite pod meal as a palatability enhancer increases the percentage of milk solids, lactose, fat and protein. Therefore, mesquite pod meal can be included in diets for dairy cows to improve the nutritive value of milk.

Nitrogen utilization, whole-body urea-nitrogen kinetics, omasal nutrient flow, and production performance in dairy cows fed lactose as a partial replacement for barley starch

The objective of this study was to determine whether the partial replacement of barley starch with lactose (fed as dried whey permeate; DWP) affects N utilization, whole-body urea kinetics, and production in dairy cows. Eight lactating Holstein cows were used in a replicated 4 × 4 Latin square design with 28-d periods. Four cows in one Latin square were ruminally cannulated and used to determine dietary effects on whole-body urea kinetics and N utilization. Cows were fed a barley-based diet that contained 3.6% (dry matter basis) total sugar (TSG; designated control), or diets that contained 6.6, 9.6, or 12.6% TSG. Dietary TSG content was increased by the replacement of barley grain with DWP (83% lactose). Diets were isonitrogenous (∼17.3% crude protein), and starch contents of the control, 6.6, 9.6, and 12.6% TSG diets were 24.3, 22.2, 21.2, and 19.1%, respectively. Whole-body urea kinetics were measured using 4-d infusions of [¹⁵N¹⁵N]-urea with concurrent total collections of feces and urine. Dry matter intake (mean = 26.7 kg/d), milk yield (mean = 34.9 kg/d), and milk protein and fat contents were unaffected by diet. Ruminal ammonia-N concentration decreased linearly as TSG content increased, whereas ruminal butyrate concentration increased linearly as TSG content increased. Urinary excretion of total N and urea-N changed quadratically, whereas urinary excretion of total N (% of N intake) tended to change quadratically as TSG content increased. Fecal N excretion linearly increased as TSG content increased. A quadratic response was observed for total N excretion as TSG content increased. Milk N and retained N were not affected by diet. As TSG content increased, we observed quadratic responses in the omasal flow of fluid-associated and total bacterial nonammonia N, endogenous production of urea-N, urea-N recycled to the gastrointestinal tract, and urea-N returned to the ornithine cycle. Dietary TSG content did not affect the anabolic utilization of recycled urea-N or the proportion of recycled urea-N that was used for bacterial growth. Our results indicate that feeding DWP did not influence dry matter intake, milk yield, or milk composition. Feeding DWP decreased ruminal ammonia-N concentration, but this did not result in positive responses in milk protein secretion or N balance. The quadratic response in omasal flow of total bacterial nonammonia N indicated that including TSG beyond 9.6% of diet dry matter might depress ruminal microbial protein synthesis.

Effect of inclusion rate of Fermenten on performance, carcass traits, and apparent total tract digestibility of growing Angus crossbred steers

In Phase 1 (days 0 to 56) of a two-phase experiment, 81 steers (initial BW = 189 ± 22 kg) were arranged in a generalized randomized block design, allocated to nine pens (nine steers per pen) and assigned to one of three dietary treatments. Treatments consisted of different inclusion rates of Fermenten (FER) in a backgrounding diet fed ad libitum, and were as follows: 0% (CON), 2%, or s FER in the diet DM. Steer was considered the experimental unit, and individual DMI was measured using the GrowSafe system. In Phase 2 (days 57 to 112), treatments were discontinued and steers were relocated to a paddock with free access to a common basal diet, to assess potential residual effects of FER. Effect of treatment was measured on performance, concentration of serum urea nitrogen (SUN), NEFA and glucose, and apparent total tract digestibility of nutrients. On day 56, steers fed 4% FER had lesser (P = 0.01) BW than 2% FER steers. Steers fed CON also tended (P = 0.08) to have greater BW than 4% FER steers. ADG was not different (P = 0.96) between CON and 2% FER steers, whereas steers in the 4% FER treatment had lesser (P ≤ 0.01) ADG than CON and 2% FER. Steers in the 4% FER treatment had lesser (P = 0.04) DMI than CON, and were less feed efficient (P ≤ 0.04) than 2% FER and CON steers. However, DMI as a percentage of the BW did not differ (P = 0.07) across treatments. A treatment effect was observed for final BW on day 112 (P = 0.05), where 4% FER tended (P = 0.07) to have lesser BW than CON. In Phase 2, ADG was not different (P = 0.18) among treatments. However, overall ADG (days 0 to 112) was lesser (P = 0.02) for steers fed 4% FER when compared with CON. There was no difference (P ≥ 0.12) in longissimus muscle area gain or 12th rib fat depth gain. There was a treatment × day interaction for serum concentrations of glucose (P < 0.001), NEFA (P < 0.001), and SUN (P < 0.001). Steers fed 4% FER had greater (P < 0.001) DM, OM, NDF, ADF, and CP apparent total tract digestibility than CON. Similarly, 4% FER steers had greater (P ≤ 0.02) DM, OM, NDF, and ADF digestibility than 2% FER. Results show that although inclusion of FER increased apparent total tract digestibility of nutrients, DMI and overall performance of growing beef cattle were negatively affected, mainly when FER was included at 4% of the diet DM.

Comparative assessment of probiotics and monensin in the prophylaxis of acute ruminal lactic acidosis in sheep

Background

Acute ruminal lactic acidosis (ARLA) is a major nutritional and metabolic disorder usually characterized by excessive or non-adapted intake of diets rich in nonstructural carbohydrates. Feed additives that regulate the ruminal environment have been used to prevent ARLA, such as ionophores and, more recently, yeast culture. Thus, we aimed to compare the efficacy of a yeast-based culture (Saccharomyces cerevisiae) with that of monensin sodium in the prevention of ARLA in sheep. Eighteen male, crossbred, rumen-cannulated sheep were randomly distributed into three groups of six animals: control, yeast culture and monensin. Thirty days after the start of supplementation with yeast culture (4 × 10⁹ cfu/animal/day of S. cerevisiae) and monensin (33 mg/kg of total dry matter intake), 15 g/kg BW of sucrose was administered directly into the rumen of the animals to induce ARLA. Samples of blood and ruminal fluid were collected at the following time points: at baseline (T0 h) immediately before the induction of ARLA; 6 h (T6 h); 12 h (T12 h); 18 h (T18 h); 24 h (T24 h); 36 h (T36 h); and 48 h (T48 h) after ARLA induction.

Results

Ruminal pH was higher in monensin group at T12 h and in yeast culture group at T36 h when compared to control group. Lower values of L-Lactate were found at yeast culture group at T24 h and T36 h. Monensin showed prophylactic effect by decreasing the rate of ruminal pH decline and occasionally reducing ruminal acidosis, whereas probiotics resulted in less accumulation of lactic acid in the rumen and a lower degree of systemic acidosis.

Conclusion

The use of yeast culture can be beneficial in the prevention and treatment of ARLA in sheep, because it can effectively reduce the accumulation of lactic acid, and thereby increase ruminal pH and reduce ruminal osmolarity. On the other hand, monensin showed prophylactic effect by decreasing the rate of ruminal pH decline and occasionally reducing ruminal acidosis, however, it did not directly prevent these conditions.

Partially replacing cornstarch in a high-concentrate diet with sucrose inhibited the ruminal trans-10 biohydrogenation pathway in vitro by changing populations of specific bacteria

Background

The positive influence of replacing dietary starch with sugar on milk fat production has been proposed to be partially attributed to the inhibition of the rumen trans-10 biohydrogenation pathway. However, whether and how sucrose inhibits the rumen trans-10 biohydrogenation pathway remains elusive.

Results

A batch in vitro incubation system was used to evaluate effects of replacing cornstarch in a high-concentrate diet (forage to concentrate ratio = 40:60) with 0 (control), 3, 6 and 9 % of sucrose on rumen fermentation pattern, fatty acid (FA) biohydrogenation pathways and bacterial populations relating to trans-11 to trans-10 biohydrogenation pathways. Replacing dietary cornstarch with sucrose did not alter rumen pH or concentrations of total volatile fatty acids (VFA) in comparison with the control but significantly influenced the profiles of individual VFA. The molar proportions of butyrate and valerate were linearly increased, while that of acetate was quadratically decreased and those of propionate, isobutyrate and isovalerate were linearly decreased with increasing concentrations of sucrose in the diet. Furthermore, replacing cornstarch with sucrose led to a linear decrease in C18:1 trans-10, linear increases in the proportions of C18:1 trans-11, C18:2n-6 and the ratio of trans-11 to trans-10, and linear decreases in biohydrogenation of C18:2n-6 and C18:3n-3. The abundance of Butyrivibrio fibrisolvens, a butyrate and CLA cis-9, trans-11 producer, was increased with the increasing inclusion of sucrose in the diet, while the population of Megasphaera elsdenii, a CLA trans-10, cis-12 producer, was significantly decreased by all levels of sucrose replacements.

Conclusions

These results indicate that replacing starch in a high-concentrate diet with sucrose increased butyrate production and inhibited the rumen trans-10 biohydrogenation pathway, which was at least partially due to increased abundance of Butyrivibrio fibrisolvens and decreased abundance of Megasphaera elsdenii.

Effects of partial replacement of dietary starch from barley or corn with lactose on ruminal function, short-chain fatty acid absorption, nitrogen utilization, and production performance of dairy cows

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.

Evaluation of ketogenic vs. glucogenic substrates as energy sources in starter diets for Holstein dairy calves

Beiranvand, H., Khorvash, M., Ghorbani, G. R., Homayouni, A., Bachmann, L. and Kargar, S. 2014. Evaluation of ketogenic vs. glucogenic substrates as energy sources in starter diets for Holstein dairy calves. Can. J. Anim. Sci. 94: 717–723. The objective of this study was to investigate the influence of the inclusion of granular sugar and sodium propionate as ketogenic and glucogenic substrates, respectively, in calf starter diets on the performance, weaning age, rumen fermentation characteristics and plasma β-hydroxybutyrate (βHBA). Twenty-one newborn male Holstein calves were housed in individual pens until 10 wk of age, receiving starter ad libitum, fresh water free choice, and fed four liters of pasteurized waste milk daily until weaning. Calves were randomly assigned to one of the following treatments: (1) no supplemental additive (Control); (2) granular sugar (5% of dietary DM; Sugar); and (3) sodium propionate (5% of dietary DM; Propionate). Overall, no differences were observed among treatments for starter intake, average daily gain, feed efficiency, day of weaning, body weight at weaning and at the end of the study. Body measurements including body length, hip height, hip width, and heart girth were remained unchanged among treatments. Ruminal fluid pH (5.36 to 5.58) and concentrations of total volatile fatty acids (93.1 to 101.6 mM), acetate (43.6 to 53.1 mM), propionate (30.5 to 35.1 mM), and ratio of acetate to propionate (1.42 to 1.89) were not affected by treatments over the experimental period. However, the concentration of butyrate was greater at 35 and 70 d of age in calves receiving Sugar compared with calves receiving Propionate, but not compared with the Control. Greater blood βHBA at 45, 60 and 70 d of age was noticed in calves fed Sugar compared with those fed Control and Propionate. In conclusion, according to the concentrations of supplemental ketogenic and glucogenic substrates used in the current experiment, sugar and sodium propionate in starter diets did not improve calf performance.

Microbial butyrate and its role for barrier function in the gastrointestinal tract

Butyrate production in the large intestine and ruminant forestomach depends on bacterial butyryl-CoA/acetate-CoA transferase activity and is highest when fermentable fiber and nonstructural carbohydrates are balanced. Gastrointestinal epithelia seem to use butyrate and butyrate-induced endocrine signals to adapt proliferation, apoptosis, and differentiation to the growth of the bacterial community. Butyrate has a potential clinical application in the treatment of inflammatory bowel disease (IBD; ulcerative colitis). Via inhibited release of tumor necrosis factor α and interleukin 13 and inhibition of histone deacetylase, butyrate may contribute to the restoration of the tight junction barrier in IBD by affecting the expression of claudin-2, occludin, cingulin, and zonula occludens poteins (ZO-1, ZO-2). Further evaluation of the molecular events that link butyrate to an improved tight junction structure will allow for the elucidation of the cofactors affecting the reliability of butyrate as a clinical treatment tool.

Effects of grain, fructose, and histidine on ruminal pH and fermentation products during an induced subacute acidosis protocol

The effects of grain, fructose, and histidine on ruminal pH and fermentation products were studied in dairy cattle during an induced subacute acidosis protocol. Thirty Holstein heifers were randomly allocated to 5 treatment groups: (1) control (no grain); (2) grain [fed at a crushed triticale dry matter intake (DMI) of 1.2% of body weight (BW)]; (3) grain (0.8% of BW DMI)+fructose (0.4% of BW DMI); (4) grain (1.2% of BW DMI)+histidine (6 g/head); and (5) grain (0.8% of BW DMI)+fructose (0.4% of BW DMI)+histidine (6 g/head) in a partial factorial arrangement. Heifers were fed 1 kg of grain daily with ad libitum access to ryegrass silage and alfalfa hay for 10 d. Feed was withheld for 14 h before challenge day, on which heifers were fed 200 g of alfalfa hay and then the treatment diets immediately thereafter. Rumen samples were collected 5 min after diet ingestion, 60 min later, and at 3 subsequent 50-min intervals. Grain decreased ruminal pH and increased ammonia, total volatile fatty acid (VFA), acetate, butyrate, propionate, and valerate concentrations compared with controls. The addition of grain had no effect on ruminal D- and L-lactate concentrations. Fructose markedly decreased ruminal pH and markedly increased D- and L-lactate concentrations. Fructose increased total VFA and butyrate and decreased valerate concentrations. Although histidine did not have a marked effect on ruminal fermentation, increased concentrations of histamine were observed following feeding. This study demonstrates that the substitution of some grain for fructose can lower ruminal pH and increase VFA and lactate concentrations, warranting further investigation into the role of sugars on the risk of acidosis in dairy cattle.

Distinct commensal bacteria associated with ingesta and mucosal epithelium in the gastrointestinal tracts of calves and chickens

The primary aim of this study was to determine whether distinct gastrointestinal tract (GIT) microbial communities are established within ingesta and on mucosal surfaces of dairy calves and chickens to evaluate whether the principle of microbial segregation is of broad biological significance. Multivariate analysis of the predominant bacterial PCR-denaturing gradient gel electrophoresis profiles and estimated bacterial populations were compared in rumen, jejunum, ileum, cecum, and colon ingesta and matching mucosal tissues. Samples collected from 3-week old (n = 8) and 6-month old (n = 8) calves revealed that the predominant mucosa-associated bacteria were distinct from those inhabiting ingesta, and bacterial diversity varied significantly among the GIT regions. The estimated bacterial populations displayed significant regional differences for bovine mucosal (P = 0.05) and for ingesta (P = 0.03) only at 6 months of age. This indicates an established segregation of the enteric bacterial population throughout the GIT in weaned calves. Analysis of ileal and cecal bacterial profiles in chickens confirmed that the segregation of commensal bacteria between ingesta and the mucosal tissue was a common biological phenomenon. Our study provides some fundamental understanding of the impact of sample type (mucosa vs. ingesta), region, and host age on commensal bacterial establishment and segregation throughout the GIT.

Corn grain and liquid feed as nonfiber carbohydrate sources in diets for lactating dairy cows

Interactions of sources and processing methods for nonstructural carbohydrates may affect the efficiency of animal production. Five rumen-cannulated cows in late lactation were placed in a 5 × 5 Latin square design and fed experimental diets for 2 wk. In the production trial, 54 cows were fed the experimental diets for 12 wk beginning at d 60 in milk. Diets contained 24% corn silage and 22% hay, averaging 20% alfalfa and 2% grass but being adjusted as needed to maintain dietary concentrations of 36% neutral detergent fiber. The control diet contained steam-flaked corn (SFC) and the other diets contained either finely (FGC; 0.8 mm) or coarsely ground corn (CGC; 1.9 mm), factorialized with or without 3.5% liquid feed (LF). The LF diets provided 1.03% of dietary dry matter as supplemental sugar. The FGC decreased rumen pH and concentration of NH(3)N compared with CGC. The SFC and FGC tended to increase the molar percentage of ruminal propionate and decrease the acetate:propionate ratio. The LF increased molar percentage of ruminal butyrate with FGC but not CGC. The LF tended to decrease starch digestibility with the CGC but not with the FGC. As expected, the SFC and FGC increased total tract starch digestibility. The DMI and milk yield were similar among dietary treatments. Compared with ground corn diets, the SFC tended to decrease milk fat percentage; thus, 3.5% fat-corrected milk and feed efficiency were decreased with SFC. The LF decreased milk protein percentage but had no effect on milk protein yield. The SFC compared with dry ground corn decreased the concentration of milk urea nitrogen. Sugar supplementation using LF appeared to be more beneficial with FGC than CGC. Increasing the surface area by finely grinding corn is important for starch digestibility and optimal utilization of nutrients.

Review: Effects of feeding sugars on productivity of lactating dairy cows

Oba, M. 2011. Review: Effects of feeding sugars on productivity of lactating dairy cows. Can. J. Anim. Sci. 91: 37–46. Sugars are water-soluble carbohydrates that are readily available in the rumen. Although sugars ferment faster than starch or fibre in the rumen, the rates of disaccharide hydrolysis and monosaccharide fermentation vary greatly depending on the type of sugar and rumen environment. Despite rapid fermentation in the rumen and their potential to provide greater fermentable energy to enhance microbial protein production, feeding sugars in place of dietary starch sources may not decrease rumen pH or improve N utilization efficiency and milk protein production in dairy cows. However, feeding high-sugar diets often increases dry matter intake, butyrate concentration in the rumen, and milk fat yield. These nutritional characteristics of sugars may allow us to use high-sugar feedstuffs as an alternative energy source for lactating dairy cows to increase dietary energy density with reduced risk of rumen acidosis, but there is little evidence in the literature to indicate that the synchrony of rumen fermentation would be enhanced by feeding high-sugar diets with high soluble protein. Greater butyrate production from feeding high-sugar diets is expected to enhance proliferation of gut tissues, but its physiological mechanisms and effects of butyrate metabolism on overall productivity of dairy cows warrant further investigations.

Effects of a molasses-coated cottonseed product on diet digestibility, performance, and milk fatty acid profile of lactating dairy cattle

An experiment was conducted to evaluate the effects of a molasses-coated cottonseed product on nutrient digestibility and milk fatty acid (FA) composition of lactating dairy cattle. The effect of a direct-fed microbial (DFM) product was also examined. Twelve Holstein cows (693+/-85kg of body weight, 127+/-39 d in milk, 2.08+/-0.29 lactations; mean +/- SD) were randomly assigned to sequence in a replicated 4 x 4 Latin square design balanced for carryover effects. Cows were fed 1 of 4 treatments during each of the four 14-d periods: a control diet including 11.4% (dry matter basis) reginned cottonseed (CON), a diet with 14.4% molasses-coated cottonseed to match the cottonseed inclusion rate of the control diet (TC), the control diet with the addition of a liquid form of the cotton coating used to produce molasses-coated cottonseed (LC), and the LC diet with the addition of a DFM (LC+DFM). Diets were formulated for equal concentrations of neutral detergent fiber, crude protein, ether extract, and macrominerals. Treatments had no effect on dry matter intake, apparent total-tract nutrient digestibility, or milk production. The molasses coat, in either form, tended to decrease concentrations of odd-chain FA (2.25 and 2.31 vs. 2.35 g/100g of FA for TC, LC, and CON, respectively) and unsaturated FA (31.4 and 31.1 vs. 32.1 g/100g of FA) in milk. This could be indicative of a mild shift in ruminal fermentation away from propionate-producing bacteria toward fiber-digesting bacteria responsible for biohydrogenation of FA. The form of the molasses coating had few effects, but LC significantly decreased concentrations of total trans-C18:1 (2.04 vs. 2.30+/-0.13 g/100g of FA) and polyunsaturated FA (4.81 vs. 5.01+/-0.17) compared with TC, implying that the liquid form slightly enhanced ruminal FA biohydrogenation. Furthermore, adding the DFM to the LC diet tended to increase the proportion of long-chain FA (FA >C16) and significantly increased the proportions of trans-C18:1 (2.22 vs. 2.04+/-0.13 g/100g of FA) and unsaturated FA (32.4 vs. 31.1+/-0.7 g/100g of FA), suggesting an inhibitory effect on ruminal biohydrogenation. Results suggest that coating cottonseed with a hardened molasses product does not significantly depress nutrient digestibility and may provide a convenient method of incorporating these ingredients into dairy rations.

Epithelial capacity for apical uptake of short chain fatty acids is a key determinant for intraruminal pH and the susceptibility to subacute ruminal acidosis in sheep

Subacute ruminal acidosis (SARA) is a common digestive disorder occurring in ruminants, with considerable variation in the severity of SARA observed among animals fed the same diet. Our aim in this study was to determine whether differences in the capacity of the ruminal epithelium for the apical uptake of acetate and butyrate (determined in Ussing chambers after slaughter) explains differences observed for the severity of a preceding episode of SARA in vivo. Adult sheep with an indwelling small ruminant ruminal pH measurement system (SRS) were randomly assigned to either a SARA induction treatment (oral drench containing 5 g glucose/kg body weight; n = 17) or a sham treatment (SHAM; n = 7; 12 mL water/kg body weight). Sheep receiving the glucose drench were further classified as nonresponders (NR; n = 7) or responders (RES; n = 7) according to their ruminal pH profile for the 3 h following the oral drench. Mean ruminal pH for the 3 h following the drench differed among groups (P < 0.001), with it being highest for SHAM (6.67 +/- 0.08), intermediate for NR (5.97 +/- 0.05), and lowest for RES (5.57 +/- 0.08) sheep. The apical uptake of acetate and butyrate did not differ between SHAM and RES sheep. However, NR sheep had greater in vitro apical uptake of acetate and butyrate and a higher plasma beta-hydroxybutyrate concentration than RES sheep, suggesting greater absorptive capacity for NR. Differences between NR and RES were attributed to greater bicarbonate-independent, nitrate-sensitive uptake of acetate (P = 0.007), a tendency for greater bicarbonate-dependent uptake of acetate (P = 0.071), and greater bicarbonate-independent uptake of butyrate (P = 0.022). These data indicate that differences in the rates and pathways for the uptake of acetate and butyrate explain a large proportion of the individual variation observed for the severity of SARA.