W.Z. Yang

SPECIAL TOPICS — Mitigation of methane and nitrous oxide emissions from animal operations: I. A review of enteric methane mitigation options

The goal of this review was to analyze published data related to mitigation of enteric methane (CH4) emissions from ruminant animals to document the most effective and sustainable strategies. Increasing forage digestibility and digestible forage intake was one of the major recommended CH4 mitigation practices. Although responses vary, CH4 emissions can be reduced when corn silage replaces grass silage in the diet. Feeding legume silages could also lower CH4 emissions compared to grass silage due to their lower fiber concentration. Dietary lipids can be effective in reducing CH4 emissions, but their applicability will depend on effects on feed intake, fiber digestibility, production, and milk composition. Inclusion of concentrate feeds in the diet of ruminants will likely decrease CH4 emission intensity (Ei; CH4 per unit animal product), particularly when inclusion is above 40% of dietary dry matter and rumen function is not impaired. Supplementation of diets containing medium to poor quality forages with small amounts of concentrate feed will typically decrease CH4 Ei. Nitrates show promise as CH4 mitigation agents, but more studies are needed to fully understand their impact on whole-farm greenhouse gas emissions, animal productivity, and animal health. Through their effect on feed efficiency and rumen stoichiometry, ionophores are likely to have a moderate CH4 mitigating effect in ruminants fed high-grain or mixed grain-forage diets. Tannins may also reduce CH4 emissions although in some situations intake and milk production may be compromised. Some direct-fed microbials, such as yeast-based products, might have a moderate CH4-mitigating effect through increasing animal productivity and feed efficiency, but the effect is likely to be inconsistent. Vaccines against rumen archaea may offer mitigation opportunities in the future although the extent of CH4 reduction is likely to be small and adaptation by ruminal microbes and persistence of the effect is unknown. Overall, improving forage quality and the overall efficiency of dietary nutrient use is an effective way of decreasing CH4 Ei. Several feed supplements have a potential to reduce CH4 emission from ruminants although their long-term effect has not been well established and some are toxic or may not be economically feasible.

Effects of an exogenous enzyme preparation on microbial protein synthesis, enzyme activity and attachment to feed in the Rumen Simulation Technique (Rusitec).

The effects of an exogenous enzyme preparation, the application method and feed type on ruminal fermentation and microbial protein synthesis were investigated using the rumen simulation technique (Rusitec). Steam-rolled barley grain and chopped alfalfa hay were sprayed with water (control, C), an enzyme preparation with a predominant xylanase activity (EF), or autoclaved enzyme (AEF) 24 h prior to feeding, or the enzyme was supplied in the buffer infused into the Rusitec (EI). Microbial N incorporation was measured using (15NH4)2SO4 in the buffer. Spent feed bags were pummelled mechanically in buffer to segregate the feed particle-associated (FPA) and feed particle-bound (FPB) bacterial fractions. Enzymes applied to feed reduced neutral-detergent fibre content, and increased the concentration of reducing sugars in barley grain, but not alfalfa hay. Ruminal cellulolytic bacteria were more numerous with EF than with C. Disappearance of DM from barley grain was higher with EF than with C, but alfalfa was unaffected by EF. Treatment EF increased incorporation of 15N into FPA and FPB fractions at 24 and 48 h. In contrast, AEF reduced the 24 h values, relative to C; AEF and C were similar at 48 h. Infused enzyme (EI) did not affect 15N incorporation. Xylanase activity in effluent was increased by EF and EI, compared to C, but not by AEF. Xylanase activity in FPA was higher at 48 h than at 24 h with all treatments; it was higher with EF than C at 24 and 48 h, but was not altered by AEF or EI. Applying enzymes onto feeds before feeding was more effective than dosing directly into the artificial rumen for increasing ruminal fibrolytic activity.

Effects of essential oils on proteolytic, deaminative and methanogenic activities of mixed ruminal bacteria

The objective of this study was to evaluate in vitro the effects of three essential oils (EO) [cinnamon leaf (250 mg L-1), garlic oil (100 and 250 mg L-1), and juniper berry oil (20 mg L-1)] and tw...

Cinnamaldehyde in feedlot cattle diets: Intake, growth performance, carcass characteristics, and blood metabolites

Cinnamaldehyde (CIN), a natural chemical compound found in the bark of cinnamon trees, can alter rumen fermentation by inhibiting selected ruminal microbes, and consequently, may improve growth performance and feed efficiency of animals. The objective of this study was to evaluate the effects of supplementing the diet of feedlot cattle with CIN on intake, growth performance, carcass characteristics, and blood metabolites. Seventy yearling steers (BW = 390 +/- 25.2 kg) were assigned to a randomized complete block design with 5 treatments: control (no additive), monensin (MO; 330 mg*steer(-1)*d(-1)), and 400, 800, or 1,600 mg of CIN*steer(-1)*d(-1). At the start of the experiment, steers were blocked according to BW and assigned to 14 blocks of 5 cattle, with cattle within block assigned to treatments. The diets consisted of 9% barley silage, 86% dry-rolled barley grain, and 5% supplement (DM basis). Dry matter intake responded quadratically (P = 0.03) to CIN supplementation with 13% more feed consumed for steers fed CIN (mean of 3 CIN levels) compared with those fed control during the first 28 d of the experiment, and with a tendency of 4% increase over the entire experiment. The ADG (kg/d) tended to respond quadratically (P = 0.08) to CIN supplementation during the first 28 d, but was not affected over the entire experiment (112 d). Feed efficiency (G:F) linearly declined (P = 0.03) during the first 28 d with CIN supplementation and was quadratically affected between d 29 to 56 and d 85 to 112 by CIN dose. Supplementation of MO did not affect (P > 0.15) DMI or growth performance at any time during the experiment. Serum NEFA concentrations were reduced (P = 0.05) by 35, 29, 30, and 22%, respectively, on d 56, 84, 112, and overall with CIN supplementation. Concentrations of serum amyloid A were reduced on d 28 by 56, 60, or 56% for 800 mg of CIN, 1,600 mg of CIN, and MO, respectively, compared with control. Plasma concentrations of lipopolysaccharide binding protein were linearly decreased (P = 0.05) with increasing CIN supplementation on d 28. Results indicate that supplementing a feedlot finishing diet with a small dose of CIN ameliorated feed intake during the initial month but had minimal effects on ADG, feed efficiency, and carcass traits over the entire experiment. Including CIN in the diet of feedlot cattle, particularly early in the feeding period, may help promote intake and reduce the effects of stress.

Mode of action of exogenous cell wall degrading enzymes for ruminants

Recent studies have shown that adding exogenous fibrolytic enzymes to ruminant diets can increase milk production of dairy cows and weight gain of growing beef cattle as a result of enhanced feed digestion. While much progress has been made in terms of advancing feed enzyme technology for ruminants, considerable research is still required to develop more effective enzyme products. The mode of action whereby exogenous enzymes improve digestion of plant cell wall is complex, and there is evidence for numerous potential modes of action suggesting they are interdependant. A mode of action that accounts for the most critical factors that explain the observed increases in feed digestion is presented. Adding exogenous enzymes to the diet increases the hydrolytic capacity of the rumen mainly due to increased bacterial attachment, stimulation of rumen microbial populations and synergistic effects with hydrolases of ruminal microorganisms. The net effect is increased enzymic activity within the rumen, which enhance...

Substitution of wheat dried distillers grains with solubles for barley grain or barley silage in feedlot cattle diets: Intake, digestibility, and ruminal fermentation1

The objective of this study was to evaluate the effects of substituting wheat dried distillers grains with solubles (DDGS) for barley grain and barley silage on intake, digestibility, and ruminal fermentation in feedlot beef cattle. Eight ruminally cannulated Angus heifers (initial BW 455 ± 10.8 kg) were assigned to a replicated 4 × 4 Latin square design with 4 treatments: control, low (25%), medium (30%), and high (35%) wheat DDGS (DM basis). The diets consisted of barley silage, barley concentrate, and wheat DDGS in ratios of 15:85:0 (CON), 10:65:25 (25DDGS), 5:65:30 (30DDGS), and 0:65:35 (35DDGS; DM basis), respectively. The diets were formulated such that wheat DDGS was substituted for both barley grain and barley silage to evaluate whether wheat DDGS can be fed as a source of both energy (grain) and fiber in feedlot finishing diets. Intakes (kg/d) of DM and OM were not different, whereas those of CP, NDF, ADF, and ether extract (EE) were greater (P < 0.01) and intake of starch was less (P < 0.01) for the 25DDGS compared with the CON diet. The digestibilities of CP, NDF, ADF, and EE in the total digestive tract were greater (P < 0.05) for 25DDGS vs. CON. Ruminal pH and total VFA concentrations were not different (P > 0.15) between 25DDGS and CON diets. Replacing barley silage with increasing amounts of wheat DDGS (i.e., from 25DDGS to 35DDGS) linearly reduced (P < 0.05) intakes of DM and other nutrients without altering (P=0.40) CP intake. In contrast, digestibilities of DM and other nutrients in the total digestive tract linearly increased (P < 0.05) with increasing wheat DDGS except for that of EE. Additionally, with increasing amounts of wheat DDGS, mean ruminal pH tended (P=0.10) to linearly decrease, and ruminal pH status decreased with longer (P=0.04) duration of pH <5.5 and <5.2, and greater (P=0.01) curve area under pH <5.8 and <5.5 without altering (P > 0.19) ruminal VFA and NH(3)-N concentrations. Results indicated that wheat DDGS can be effectively used to replace both barley grain and silage at a moderate amount to meet energy and fiber requirements of finishing cattle. However, when silage content of the diet is low (<10%), wheat DDGS is not an effective fiber source, so replacing forage fiber with wheat DDGS in finishing diets decreases overall ruminal pH status even though the rapidly fermentable starch content of the diet is considerably reduced.

Feeding barley grain steeped in lactic acid modulates rumen fermentation patterns and increases milk fat content in dairy cows

The objectives of the present in vivo and in situ trials were to evaluate whether feeding barley grain steeped in lactic acid (LA) would affect rumen fermentation patterns, in situ dry matter (DM) degradation kinetics, and milk production and composition in lactating dairy cows. The in vivo trial involved 8 rumen-fistulated Holstein cows fed once daily a total mixed ration containing rolled barley grain (27% in DM) steeped for 48 h in an equal quantity of tap water (CTR) or in 0.5% LA (TRT) in a 2 x 2 crossover design. The in situ trials consisted of incubation of untreated rolled barley grain in cows fed CTR or TRT diets and of incubation of 3 different substrates including CTR or barley grain steeped in 0.5% or 1.0% LA (TRT1 and TRT2, respectively) up to 72 h in the rumen. Results of the in vivo trial indicated that cows fed the TRT diet had greater rumen pH during most intensive fermentation phases at 10 and 12 h post-feeding. The latter effect was associated with a shorter duration in which rumen pH was below 5.8 for cows fed the TRT diet (2.4 h) compared with CTR diet (3.9 h). Furthermore, cows fed the TRT diet had lower concentrations of volatile fatty acids at 2 and 4 h post-feeding. In addition, concentrations of preprandial volatile fatty acids were lower in the rumen fluid of cows fed the TRT diet. Results also showed that molar proportion of acetate was lower, whereas propionate tended to increase by feeding cows the TRT diet. Cows fed the TRT diet demonstrated greater rumen in situ lag time of substrate DM degradation and a tendency to lower the fractional degradation rate. Other in situ results indicated a quadratic effect of LA on the effective rumen degradability of substrates whereby the latter variable was decreased from CTR to TRT1 but increased for TRT2 substrate. Although the diet did not affect actual milk yield, fat-corrected milk, percentages of milk protein, and lactose and concentration of milk urea nitrogen, cows fed the TRT diet increased milk fat content and tended to increase fat:protein ratio in the milk. In conclusion, results demonstrated that treatment of barley grain with LA lowered the risk of subacute rumen acidosis and maintained high milk fat content in late-lactating Holstein cows fed diets based on barley grain.

Increasing physically effective fiber content of dairy cow diets through forage proportion versus forage chop length: Chewing and ruminal pH

A study was conducted to evaluate whether the risk of acidosis in dairy cows can be lowered by increasing the physically effective fiber (peNDF) concentration of the diet, either through increased theoretical chop length of alfalfa silage or higher proportion of forage in the diet. The experiment was designed as a replicated 4 x 4 Latin square using 8 ruminally cannulated lactating dairy cows. Treatments were arranged in a 2 x 2 factorial design; 2 forage particle lengths (FPL) of alfalfa silage (short and long) were combined with low (35:65) and high (60:40) forage:concentrate (F:C) ratios [dry matter (DM) basis]. Dietary peNDF concentration (DM basis) was determined from the sum of the proportion of dietary DM retained either on the 2 sieves (8 and 19 mm) or on the 3 sieves (1.18, 8, and 19 mm) of the Penn State Particle Separator multiplied by the neutral detergent fiber concentration of the diet. The dietary peNDF concentrations were altered by changing the F:C or the FPL, and ranged from 10.7 to 17.5% using 2 sieves, or from 23.1 to 28.2% using 3 sieves. Intake of peNDF was increased by increasing FPL but not by increasing F:C ratio because of the reduction of DM intake at the higher F:C ratio. Chewing activity, including number of chews and chewing time, increased with increasing F:C ratio or FPL. Mean ruminal pH was elevated by 0.4 and 0.2 units with increasing F:C ratio and FPL, respectively. Lowering the F:C ratio decreased the duration that ruminal pH was below 5.8 (1.2 vs. 8 h/d). Increased F:C ratio or FPL reduced ruminal volatile fatty acids concentration from 137 to 122 or from 133 to 126 mM, respectively, whereas acetate:propionate ratio was increased from 2.55 to 3.46 with increasing F:C ratio. Dietary peNDF concentration measured using 2 sieves was correlated to chewing time (r = 0.57) and mean ruminal pH (r = 0.75), whereas dietary peNDF concentration measured using 3 sieves was correlated to mean ruminal pH (r = 0.83) and negatively correlated to the time that pH was below 5.8 (r = -0.78). This study shows that the risk of ruminal acidosis is high for cows fed a low F:C diet. Increasing the proportion of forage in the diet helps prevent ruminal acidosis through increased chewing time, a change in meal patterns, and decreased ruminal acid production. Increasing FPL elevates ruminal pH, but in low forage diets, increased FPL does not alleviate subacute acidosis because the fermentability of the diet is high and changes in chewing activity are marginal.

Dose response to cinnamaldehyde supplementation in growing beef heifers: ruminal and intestinal digestion.

The objective of this study was to determine if cinnamaldehyde (CIN) could be used to improve feed intake, digestion, and immune status in growing beef heifers fed high-concentrate diets. The experiment was designed as a 4 x 4 Latin square using 4 ruminally and duodenally cannulated beef heifers with 4 treatments: control (no CIN added), 400 mg/d of CIN (low), 800 mg/d of CIN (medium), and 1,600 mg/d of CIN (high), and four 21-d periods. Feed intake, rumen pH and fermentation characteristics, site and extent of digestion, microbial N synthesis, blood metabolites, and acute phase protein response were measured. The diets consisted of 15% barley silage, 80% dry-rolled barley grain, and 5% supplement (DM basis). Intakes (kg/d) of DM, OM, NDF, starch, and N were quadratically (P = 0.04) changed with increasing CIN supplementation. The amount of OM fermented in the rumen quadratically (P = 0.02) decreased with increasing CIN. Digestibilities (% of intake) of OM, NDF, and N in the rumen were not affected by supplementing with low and medium CIN, but they were reduced by 8% (P = 0.10), 31% (P = 0.05), and 17% (P = 0.05), respectively, with high CIN. Similarly, digestibilities of OM and NDF in the total tract also tended to be reduced by 7% (P = 0.10) and 20% (P = 0.10), respectively, with high CIN because supplementation of CIN had minimal effects on intestinal digestibility. Flows (g/d) of microbial N and other nutrients to the duodenum were not affected by CIN supplementation, even though the amount of ruminal fermented OM varied with level of CIN supplementation. Rumen pH, total VFA concentration, and molar proportions of individual VFA were not affected by CIN. Although concentrations of NEFA (P = 0.06) and triglyceride (P = 0.01) were quadratically changed with increasing CIN supplementation, blood concentrations of glucose and urea N, white blood cell counts, serum amyloid A, and lipopolysaccharide in plasma were not affected by CIN. Plasma haptoglobin numerically (P = 0.11) decreased with the medium dose of CIN fed compared with control. The results indicate that supplementation of a high-concentrate diet with a low dose of CIN resulted in small increases in nutrient availability in the rumen due to increased feed intake and greater ruminal digestion of OM. However, feed intake and ruminal digestion of feeds were adversely affected when a high dose of CIN was used.

Wheat distillers grains in feedlot cattle diets: Feeding behavior, growth performance, carcass characteristics, and blood metabolites

A study was conducted to evaluate feed intake, ADG, carcass quality, eating behavior, and blood metabolites in feedlot beef steers fed diets that varied in proportion of wheat dried distillers grains with solubles (DDGS) replacing barley grain or barley silage. Two hundred crossbred steers (BW = 489 ± 30 kg) were blocked by BW and randomly allotted to 20 pens (5 pens per treatment). Steers were fed 1 of 4 diets: control without DDGS (CON), 25% (25DDGS), 30% (30DDGS), or 35% (35DDGS) wheat DDGS (DM basis). The CON diet consisted of 15% barley silage and 85% barley-based concentrate; the 3 wheat DDGS diets were formulated by substituting 20% barley grain and 5, 10, or 15% silage, respectively, with 25, 30, or 35% wheat DDGS so that the 35DDGS diet contained no silage. The diets were formulated such that wheat DDGS was substituted for both barley grain and barley silage to evaluate whether wheat DDGS can be fed as a source of both energy and fiber in feedlot finishing diets. Dry matter intake of steers fed 25DDGS was greater (P < 0.01), but final BW, ADG, and G:F were not different compared with steers fed CON diet. Carcass characteristics and liver abscess score were not different between CON and 25DDGS. Steers fed 25DDGS had longer eating time (min/d; P < 0.01), greater meal frequency (P < 0.04), but a slower eating rate (P < 0.04). Replacing barley silage with increasing amounts of wheat DDGS (from 25DDGS to 35DDGS) linearly reduced (P < 0.01) DMI. Final BW, ADG, and G:F were not affected by increasing amounts of wheat DDGS. Carcass traits were not different, whereas liver abscess scores linearly (P < 0.01) increased as more barley silage was replaced by wheat DDGS. Eating time (min/d) and duration of each meal linearly (P < 0.02) decreased, whereas eating rate (min/g of DM) linearly (P < 0.01) increased with increasing replacement of barley silage. Blood urea N was doubled (P < 0.01) compared with CON by inclusion of wheat DDGS. Results indicate that wheat DDGS can be used effectively in feedlot diets, decreasing the need for barley grain or silage without negatively affecting growth performance and carcass characteristics. A reduction in the amount of roughage required to maintain growth performance is a potential advantage in feedlot operations because forage is costly and often of limited availability. Thus, DDGS can be a possible alternative as long as they are available and cost effective; however, increased incidence of liver abscess and increased N content of manure need to be considered when greater amounts of wheat DDGS are included in finishing diets.