Effect of Grains Differing in Expected Ruminal Fermentability on the Productivity of Lactating Dairy Cows

Symposium review: Effects of carbohydrate digestion on feed intake and fuel supply

Carbohydrates are the primary energy source for lactating dairy cows, and dairy diets are usually formulated for certain concentrations of forage neutral detergent fiber (NDF) and starch due to their direct effects on dry matter intake and milk production. Forage NDF exerts greater filling effects in the rumen than other dietary components and can limit maximum voluntary feed intake of lactating dairy cows. Since an analytical method for NDF was developed more than a half century ago, it has been used widely to characterize forages and diets for dairy cows. However, because NDF is a chemical measurement varying in its digestibility, in vitro digestibility measurements were developed as a biological approach to assess forage quality. Research efforts over the last several decades led to the development of forage cultivars or hybrids with enhanced in vitro NDF digestibility, such as brown midrib, and management practices considering differences in NDF digestibility of forages. In addition, in vitro NDF digestibility and undigested NDF are commonly measured in commercial labs, and estimated rates of digestion are used in dynamic models in an effort to improve the accuracy and precision of diet formulation. Starch digestion in the rumen also varies among starch sources, being affected by grain type, extent of processing, and conservation method. The site and rate of starch digestion affect dry matter intake and nutrient partitioning in dairy cows by modifying temporal supply of fuel. In addition, dietary starch content and its fermentability can affect digestion rates of starch itself and NDF in the rumen. Previous research has increased our understanding of dietary carbohydrates, but its application for diet formulations requires integrated approaches accounting for factors affecting the filling effects of forage NDF, starch digestion, and temporal fuel supply.

Evaluation of dehydrated corn silage as the primary forage for lactating dairy cows

The objective was to compare productivity of lactating dairy cows fed dehydrated corn silage with those fed whole-crop barley silage. Twelve multiparous Holstein cows in mid lactation were fed diets containing dehydrated corn silage (DCS) or barley silage with additional grain (BSHG) or without (BSLG) in a 3 × 3 Latin square design, with 21-d periods, balanced for carryover effects. The dietary starch content was similar for DCS and BSHG diets, and dietary forage content was similar for DCS and BSLG diets. Experimental diets did not affect dry matter intake, but cows fed DCS diet decreased milk yield compared with those fed barley silage regardless of the dietary starch content. Apparent total-tract digestibility of starch and crude protein was also lower for cows fed DCS compared with those fed barley silage, and milk urea N content was lowest for cows fed DCS diet, indicating that DCS likely had less protein degradation in the rumen than barley silage. Milk fat content and yield, energy-corrected milk yield, and feed efficiency were not different between cows fed BSHG and DCS diets, but higher for cows fed BSLG than those fed BSHG or DCS diet, which can be attributed to the difference in dietary starch content. Feeding DCS in place of barley silage did not improve productivity of lactating dairy cows in the current study, and further research is warranted to optimize its utilization in dairy diets.

Effects of varying proportions of corn grain to barley grain in corn silage-based diet on feed sorting behaviour and productivity of dairy cows

Context Although several studies investigated the dairy cow performance in response to varying ratios of corn to barley grain, little attention has been paid to the forage component of the diet. We hypothesised that a diet based on corn silage with coarse particles might promote chewing and saliva secretion, neutralising acids produced during excess fermentation of high-barley diet and, thus, improve dairy cow productivity. Aims Feed sorting behaviour, nutrient digestibility, rumen fermentation, and milk production were recorded in Holstein cows offered a corn silage-based diet in which corn grain was incrementally substituted with barley grain. Methods Eight multiparous cows, averaging 189 ± 24 days in milk, 577 ± 47 kg bodyweight and 33 ± 5 kg/day milk yield, were distributed according to two 4 × 4 Latin squares. Four total mixed rations were designed, differing in corn to barley ratios as follows: (1) 100:0, (2) 67:33, (3) 33:67 and (4) 0:100. Corn silage and alfalfa hay constituted 31.0% and 9.0% of diet DM respectively. Key results Although no treatment difference existed on sorting of long, medium or fine particles, the extent of sorting for 1.18-mm particles tended to increase linearly as corn to barley ratio decreased. The ruminal pH declined linearly from 5.90 to 5.60 as the barley grain proportion increased from 0 to 100. Acetate to propionate ratio decreased linearly (P < 0.01) as the barley grain proportion increased. No differences were seen in feed consumption and organic matter, crude protein, neutral detergent fibre and fat digestion in total tract. However, non-fibre carbohydrate digestibility tended to increase linearly (P = 0.07) as the ratio of corn to barley grain decreased. Time spent eating, ruminating and chewing remained largely unaffected by treatment. Treatments had no effect on fat-corrected milk production and milk composition, with the exception that actual milk production tended to increase linearly as the corn to barley ratio decreased. Feed efficiency (milk production/DM intake (DMI)) increased linearly from 1.22 to 1.32 as the barley grain proportion increased from 0 to 100. Conclusions Although the differences in feeding behaviour, DMI, and milk production and composition were negligible among experimental diets, cows consuming a corn silage-based diet with incremental substitution of corn grain with barley grain produced more milk per kilogram of DMI. Implications Increased proportion of barley grain in replacement of corn grain in corn silage-based diet might be advised as it increased the efficiency of feed conversion to milk.

Effects of substitution of beet pulp for barley or corn in the diet of high-producing dairy cows on feeding behavior, performance, and ruminal fermentation

This study investigated the effects of substituting beet pulp (BP) for different grains (barley or corn) in the diet of high-producing dairy cows on intake, feeding behavior, nutrient digestibility, ruminal fermentation, milk production, and feed conversion efficiency. Eight second-parity Holstein cows (62 ± 2 d in milk; milk yield = 54 ± 1.2 kg/d; body weight = 624 ± 26; all mean ± SE) were used in a replicated 4 × 4 Latin square design during 4 periods of 21 d. Cows were randomly assigned to 1 of 4 treatments that were a 2 × 2 factorial arrangement of 2 grain sources (corn or barley) and 2 levels of BP inclusion [5 or 15% of dry matter (DM)] in the diet: (1) barley-based diet with BP at 5% of dietary DM; (2) barley-based diet with BP at 15% of dietary DM; (3) corn-based diet with BP at 5% of dietary DM; and (4) corn-based diet with BP at 15% of dietary DM. The increasing amount of BP in the diet was at the expense of decreasing an equal proportion of grain (barley or corn). All diets were high in concentrates (65% of diet DM) and formulated to have similar concentrations of energy and protein. The portion of feedstuffs that is potentially able to be consumed by humans is known as human edible. Accordingly, human-edible protein (HEP) and human-edible energy (HEE) inputs were calculated according to the recommended potential human-edible fraction of each dietary ingredient, and HEP and HEE outputs were determined as the amount of gross energy and true protein in the milk. Feed conversion efficiency (FCE) for HEP and HEE were expressed as output per input of each variable, whereas FCE for the production of fat-corrected milk (FCM) and energy-corrected milk (ECM) were expressed as the amount of each variable per DM intake. Results showed that substituting BP for grain did not affect DM intake, crude protein intake, or nutrient digestibility, whereas starch intake (5.70 vs. 7.43 kg/d for the low-BP vs. high-BP diets, respectively), HEP (2.34 and 1.92 kg/d), and HEE (186 and 147 MJ of gross energy/d) decreased. Treatments did not affect sorting and chewing activities, but increasing BP in the diet increased ruminal pH at 4 h after feeding (6.20 vs. 6.39) and milk fat content (2.92 vs. 3.15%). Similarly, FCE for ECM production (1.44 vs. 1.54) as well as FCE for HEE (0.653 vs. 0.851) and HEP (0.629 vs. 0.702) were greater in high-BP diets compared with low-BP diets. The interaction of BP and grain sources significantly affected FCE for ECM production, where improvements were more evident when BP was substituted for barley than for corn. The improvement in FCE for HEE was greater when BP was substituted for barley (0.236) rather than corn (0.161). In conclusion, the substitution of BP for barley or corn grains in high-concentrate diets of high-producing cows decreased starch intake, increased ruminal pH at 4 h after feeding, and improved FCE for FCM production. Substitution for barley, rather than for corn, promoted greater FCE for ECM production and HEE.

Transcriptome analysis of rumen epithelium and meta-transcriptome analysis of rumen epimural microbial community in young calves with feed induced acidosis

Many common management practices used to raise dairy calves while on milk and during weaning can cause rumen acidosis. Ruminal pH has long been used to identify ruminal acidosis. However, few attempts were undertaken to understand the role of prolonged ruminal acidosis on rumen microbial community or host health in young calves long after weaning. Thus, the molecular changes associated with prolonged rumen acidosis in post weaning young calves are largely unknown. In this study, we induced ruminal acidosis by feeding a highly processed, starch-rich diet to calves starting from one week of age through 16 weeks. Rumen epithelial tissues were collected at necropsy at 17 weeks of age. Transcriptome analyses on the rumen epithelium and meta-transcriptome analysis of rumen epimural microbial communities were carried out. Calves with induced ruminal acidosis showed significantly less weight gain over the course of the experiment, in addition to substantially lower ruminal pH in comparison to the control group. For rumen epithelial transcriptome, a total of 672 genes (fold-change, FC ≥ 1.5; adjusted-p ≤ 0.05) showed significant differential expression in comparison to control. Biological pathways impacted by these differentially expressed genes included cell signaling and morphogenesis, indicating the impact of ruminal acidosis on rumen epithelium development. rRNA read-based microbial classification indicated significant increase in abundance of several genera in calves with induced acidosis. Our study provides insight into host rumen transcriptome changes associated with prolonged acidosis in post weaning calves. Shifts in microbial species abundance are promising for microbial species-based biomarker development and artificial manipulation. Such knowledge provides a foundation for future more precise diagnosis and preventative management of rumen acidosis in dairy calves.

Response of lactating dairy cows to degree of steam-flaked barley grain in low-forage diets

This study was conducted to investigate the effects of processing method (grinding vs. steam flaking) and increasing densities of steam-flaked barley grain on dry matter intake (DMI), rumen pH and fermentation characteristics, digestibility of dry matter in the total digestive tract (DDTT), and milk production of dairy cows. Eight multiparous mid-lactation Holstein cows averaging 103 ± 24 DIM, 44.5 ± 4.7 kg milk/day and weighing 611 ± 43 kg at the start of the experiment were used in a replicated 4 × 4 Latin square design with 21-day periods. Cows were fed diets consisting of (DM basis) 23.8% corn silage, 13.5% chopped alfalfa hay and 62.7% concentrate. The dietary treatments were either ground barley (GB) using a hammer mill or steam-flaked barley (SFB) - varying density at 390, 340 or 290 g/l. Processing method (GB vs. SFB) did not affect DMI (23.6 kg/day on average), DDTT (71.0% on average), milk yield (43.4 kg/day on average), milk components, rumen pH and molar proportions of acetate, propionate, butyrate and sorting activity. Ruminal isovalerate concentration tended (p = 0.06) to be higher for cows fed GB than those fed SFB-based diets. Decreasing the density of SFB from 390, 340 to 290 g/l tended to linearly increase DMI (p = 0.09), decrease total solids percentage of milk (p = 0.10) and linearly decreased milk urea nitrogen (12.8, 12.4 and 12.1 mg/dl; p = 0.04); also, the sorting index (SI) of the particles retained on the 19.0-mm sieve without affecting the SI of the particles retained on 8.0-mm, 1.18-mm or passed through 1.18-mm sieve (p = 0.05). These results indicated the limited effects of processing method (grinding vs. steam flaking) and densities of SFB (390, 290 or 290 g/l) on cows' performance and feed utilization for dairy cows fed low-forage diets. Therefore, both processing methods could be recommended under current feeding conditions of dairy cows.

Long-term reticuloruminal pH dynamics and markers of liver health in early-lactating cows of various parities fed diets differing in grain processing

The present study aimed to investigate the long-term effect of feeding barley grain steeped in lactic acid (La) with or without thermal treatment on reticuloruminal pH dynamics and metabolic activity of the liver in 12 primiparous and 18 multiparous early-lactating dairy cows. All cows were included on d 21 postpartum and sampled until d 90 postpartum. Cows were fed a diet based on differently processed ground barley grain: untreated grain (control diet, CON), or grain treated with 1% La alone for 24 h before feeding (La), or with an additional oven-heating at 55°C for 12 h (LaH). The reticuloruminal pH and temperature were measured via indwelling sensors that allowed for continuous (every 10min) and long-term measurement from d 21 to 80 postpartum. Blood samples were taken on d 21, 40, and 90 of lactation and analyzed for liver enzymes aspartate aminotransferase (AST), gamma-glutamyltransferase, and glutamate dehydrogenase, as well as bilirubin, bile acids, and serum amyloid A. Dry matter intake was higher in multiparous cows (20.7±0.27 kg/d) compared with primiparous cows (18.2±0.33 kg/d), but was not affected by dietary treatment. Overall, the relatively short duration (51±5min/d) of reticuloruminal pH <5.8 suggests low risk of subacute ruminal acidosis throughout the experiment. Results indicated that La treatment of barley, with or without heat, lowered the time duration of pH <5.8 compared with CON, but only in primiparous cows (from 118±13 to 46±11 and 25±11min/d for CON, La, and LaH, respectively). In multiparous cows, the opposite effect of feeding the La-treated barley on time duration of pH <5.8 (11±8 vs. 46±9 vs. 57±9min/d for CON, La, and LaH, respectively) was observed. Multiparous cows generally showed higher pH readings and shorter periods in which the ruminal pH dropped below the threshold of pH 5.8. The reticuloruminal temperature was not affected by dietary treatment, whereas parity affected the time duration of reticuloruminal temperature >39.5°C, being 60±19min/d shorter in primiparous cows. The measured activities of the liver enzymes AST, gamma-glutamyltransferase, and glutamate dehydrogenase, as well as bilirubin, bile acids, and the acute phase protein serum amyloid A, were not affected by grain feeding. Additionally, only one small effect of parity on investigated serum variables was noticed, showing slightly but significantly higher values of AST in multiparous (80.5±1.4 U/L) compared with primiparous cows (76.0±1.7 U/L). In conclusion, our results indicate greater risk for primiparous cows to develop subacute ruminal acidosis-like conditions during early lactation than multiparous cows. The study also suggests limited benefits of feeding processed barley grain with La with or without thermal treatment to modulate ruminal tolerance of grain feeding, whereby differing effects in primiparous cows were observed compared with multiparous cows.

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.

Effects of dietary starch content and rate of fermentation on methane production in lactating dairy cows

The objective of this study was to investigate the effects of starch varying in rate of fermentation and level of inclusion in the diet in exchange for fiber on methane (CH4) production of dairy cows. Forty Holstein-Friesian lactating dairy cows of which 16 were rumen cannulated were grouped in 10 blocks of 4 cows each. Cows received diets consisting of 60% grass silage and 40% concentrate (dry matter basis). Cows within block were randomly assigned to 1 of 4 different diets composed of concentrates that varied in rate of starch fermentation [slowly (S) vs. rapidly (R) rumen fermentable; native vs. gelatinized corn grain] and level of starch (low vs. high; 270 vs. 530g/kg of concentrate dry matter). Results of rumen in situ incubations confirmed that the fractional rate of degradation of starch was higher for R than S starch. Effective rumen degradability of organic matter was higher for high than low starch and also higher for R than S starch. Increased level of starch, but not starch fermentability, decreased dry matter intake and daily CH4 production. Milk yield (mean 24.0±1.02kg/d), milk fat content (mean 5.05±0.16%), and milk protein content (mean 3.64±0.05%) did not differ between diets. Methane expressed per kilogram of fat- and protein-corrected milk, per kilogram of dry matter intake, or as a fraction of gross energy intake did not differ between diets. Methane expressed per kilogram of estimated rumen-fermentable organic matter (eRFOM) was higher for S than R starch-based diets (47.4 vs. 42.6g/kg of eRFOM) and for low than high starch-based diets (46.9 vs. 43.1g/kg of eRFOM). Apparent total-tract digestibility of neutral detergent fiber and crude protein were not affected by diets, but starch digestibility was higher for diets based on R starch (97.2%) compared with S starch (95.5%). Both total volatile fatty acid concentration (109.2 vs. 97.5mM) and propionate proportion (16.5 vs. 15.8mol/100mol) were higher for R starch- compared with S starch-based diets but unaffected by the level of starch. Total N excretion in feces plus urine and N retained were unaffected by dietary treatments, and similarly energy intake and output of energy in milk expressed per unit of metabolic body weight were not affected by treatments. In conclusion, an increased rate of starch fermentation and increased level of starch in the diet of dairy cattle reduced CH4 produced per unit of eRFOM but did not affect CH4 production per unit of feed dry matter intake or per unit of milk produced.

Precision processing barley grain did not affect productivity of lactating dairy cows

Schlau, N., Duineveld, L., Yang, W. Z., McAllister, T. A. and Oba, M. 2013. Precision processing barley grain did not affect productivity of lactating dairy cows. Can. J. Anim. Sci. 93: 261–268. This study evaluated the effects of precision processing (PP; processing based on kernel size) barley grain on ruminal fermentation and productivity of lactating dairy cows. Twenty multiparous Holstein cows, including eight ruminally cannulated cows, were used in a replicated 4×4 Latin square design with 21-d periods. Diets contained light barley grain processed precisely using a narrow roller setting (LB), heavy barley processed precisely using a wide roller setting (HB), processed HB and LB mixed at equal proportions (PP), or equal parts of light and heavy barley grain processed at a single narrow roller setting (CON). All diets consisted of 40% barley grain, 40% barley silage, and 20% of a supplement premix. Comparisons were made between LB and HB to evaluate the effect of barley quality, and between PP and CON to evaluate the effect of precision processing. Dry matter intake, sorting index, ruminal fermentation characteristics, and nutrient digestibility were not affected by diet. In addition, milk yield and concentrations of milk fat, protein, and lactose were not different, although milk urea nitrogen concentration was greater for PP vs. CON and for LB vs. HB. These results suggest that precision processing barley grain based on kernel size may not drastically affect ruminal fermentation and milk production in lactating dairy cows.

Effects of feeding a calf starter on molecular adaptations in the ruminal epithelium and liver of Holstein dairy calves

The objective of this study was to elucidate the effect of feeding a calf starter on the volatile fatty acid (VFA) profile in the rumen and on expression of genes involved in epithelial intracellular pH regulation, butyrate metabolism, and hepatic urea cycle during the weaning transition. Twenty Holstein bull calves were fed either milk replacer and hay (MR) or milk replacer, hay, and a commercial texturized calf starter (MR+S) in a randomized complete block design. All calves were fed 750 g/d of milk replacer as the basal diet. Calves on the MR+S treatment were also fed starter ad libitum, and the energy intake of calves within blocks was maintained by supplementing the MR group with extra milk replacer that was equivalent to the energy intake from calf starter. Calves were killed 3 d after they consumed 680 g/d of calf starter for 3 consecutive days. Calves fed MR+S had higher VFA concentrations in the rumen (99.1±8.1 vs. 64.6±8.6 mM) and a higher molar proportion of butyrate (15.6±1.7 vs. 7.9±1.9%) than calves fed MR. Relative abundance of mRNA for monocarboxylate transporter isoform 1 was higher (1.45 vs. 0.53), and that of Na(+)/H(+) exchanger isoform 3 (0.37 vs. 0.82) and 3-hydroxy-3-methylglutaryl synthase isoform 1 (0.40 vs. 0.94) lower for the MR+S treatment compared with the MR treatment. In the liver, relative mRNA abundances of argininosuccinate synthetase isoform 1 (2.67 vs. 1.56), argininosuccinate lyase (1.44 vs. 0.99), and arginase isoform 1 (3.21 vs. 1.74) were greater for MR+S than for MR calves. Calf starter consumption appeared to increase fermentation in the rumen and affected expression of genes involved in cholesterol synthesis and intracellular pH regulation in ruminal epithelium, and those involved in urea cycle in the liver.

Invited review: Role of physically effective fiber and estimation of dietary fiber adequacy in high-producing dairy cattle

Highly fermentable diets require the inclusion of adequate amounts of fiber to reduce the risk of subacute rumen acidosis (SARA). To assess the adequacy of dietary fiber in dairy cattle, the concept of physically effective neutral detergent fiber (peNDF) has received increasing attention because it amalgamates information on both chemical fiber content and particle size (PS) of the feedstuffs. The nutritional effects of dietary PS and peNDF are complex and involve feed intake behavior (absolute intake and sorting behavior), ruminal mat formation, rumination and salivation, and ruminal motility. Other effects include fermentation characteristics, digesta passage, and nutrient intake and absorption. Moreover, peNDF requirements depend on the fermentability of the starch source (i.e., starch type and endosperm structure). To date, the incomplete understanding of these complex interactions has prevented the establishment of peNDF as a routine method to determine dietary fiber adequacy so far. Therefore, this review is intended to analyze the quantitative effects of and interactions among forage PS, peNDF, and diet fermentability with regard to rumen metabolism and prevention of SARA, and aims to give an overview of the latest achievements in the estimation of dietary fiber adequacy in high-producing dairy cattle. Recently developed models that synthesize the effects of both peNDF and fermentable starch on rumen metabolism appear to provide an appropriate basis for estimation of dietary fiber adequacy in high-producing dairy cows. Data suggest that a period lasting more than 5 to 6h/d during which ruminal pH is <5.8 should be avoided to minimize health disturbances due to SARA. The knowledge generated from these modeling approaches recommends that average amounts of 31.2% peNDF inclusive particles >1.18mm (i.e., peNDF(>1.18)) or 18.5% peNDF inclusive particles >8mm (i.e., peNDF(>8)) in the diet (DM basis) are required. However, inclusion of a concentration of peNDF(>8) in the diet beyond 14.9% of diet DM may lower DM intake level. As such, more research is warranted to develop efficient feeding strategies that encourage inclusion of energy-dense diets without the need to increase their content in peNDF above the threshold that leads to lower DM intake. The latter would require strategies that modulate the fermentability characteristics of the diet and promote absorption and metabolic capacity of ruminal epithelia of dairy cows.

Barley grain for ruminants: A global treasure or tragedy

Barley grain (Hordeum vulgare L.) is characterized by a thick fibrous coat, a high level of ß-glucans and simply-arranged starch granules. World production of barley is about 30 % of that of corn. In comparison with corn, barley has more protein, methionine, lysine, cysteine and tryptophan. For ruminants, barley is the third most readily degradable cereal behind oats and wheat. Due to its more rapid starch fermentation rate compared with corn, barley also provides a more synchronous release of energy and nitrogen, thereby improving microbial nutrient assimilation. As a result, feeding barley can reduce the need for feeding protected protein sources. However, this benefit is only realized if rumen acidity is maintained within an optimal range (e.g., > 5.8 to 6.0); below this range, microbial maintenance requirements and wastage increase. With a low pH, microbial endotoxines cause pro-inflammatory responses that can weaken immunity and shorten animal longevity. Thus, mismanagement in barley processing and feeding may make a tragedy from this treasure or pearl of cereal grains. Steam-rolling of barley may improve feed efficiency and post-rumen starch digestion. However, it is doubtful if such processing can improve milk production and feed intake. Due to the need to process barley less extensively than other cereals (as long as the pericarp is broken), consistent and global standards for feeding and processing barley could be feasibly established. In high-starch diets, barley feeding reduces the need for capacious small intestinal starch assimilation, subsequently reducing hindgut starch use and fecal nutrient loss. With its nutritional exclusivities underlined, barley use will be a factual art that can either matchlessly profit or harm rumen microbes, cattle production, farm economics and the environment.

Fenugreek (Trigonella foenum-graecum L.) as an alternative forage for dairy cows

Fenugreek is a novel forage crop in Canada that is generating interest as an alternative to alfalfa for dairy cows. To evaluate the value of fenugreek haylage relative to alfalfa haylage, six, second lactation Holstein cows (56 ± 8 days in milk), which were fitted with rumen cannulas (10 cm i.d., Bar Diamond Inc., Parma, ID, USA) were used in a replicated three × three Latin square design with 18-day periods. Diets consisting of 400 g/kg haylage, 100 g/kg barley silage and 500 g/kg concentrate on a dry matter (DM) basis were fed once daily for ad libitum intake. The haylage component constituted the dietary treatments: (i) Agriculture and Agri-Food Canada F70 fenugreek (F70), (ii) Crop Development Center Quatro fenugreek (QUAT) and (iii) alfalfa (ALF). DM intake (DMI), milk yield and milk protein and lactose yields were higher (P < 0.001) for cows fed ALF than fenugreek (FEN, average of F70 and QUAT). Milk fat of cows fed FEN contained lower concentrations of saturated, medium-chain and hypercholestrolemic fatty acids (FAs; P < 0.05) than that of cows fed ALF. Apparent total tract digestibility of DM and nutrients was not affected by treatments. Similarly, individual ruminal volatile FA concentrations and rumen pH (5.9) were not affected by treatments. Rumen ammonia-N concentration was higher for FEN than ALF (P < 0.001). Estimates of neutral detergent fiber (NDF) passage rate (P < 0.05) and NDF turnover rate (P < 0.001) in the rumen were higher for ALF than FEN. Our results suggest that although the digestibility of the FEN diets was not different from that of the ALF diet, fenugreek haylage has a lower feeding value than ALF for lactating dairy cows due in part to lower DMI and subsequently lower milk yield.

Effect of replacing corn with brown rice in a total, mixed, ration silage on milk production, ruminal fermentation and nitrogen balance in lactating dairy cows

Nine multiparous Holstein cows were used in a replicated 3 × 3 Latin square design to determine the effects of substituting corn grain with brown rice (BR) grain in total mixed ration (TMR) silage on milk yield, ruminal fermentation and nitrogen (N) balance. The TMR silages were made from the ensiling of TMR containing (dry matter basis) 50.1% forage in rice silage and corn silage combination, and 49.9% concentrate. The grain portion of the diets contained 31.2% steam-flaked corn, 31.2% steam-flaked BR or an equal mixture of corn and BR. Dietary treatments did not affect dry matter intake, milk yield and milk fat, protein and lactose yields. The ruminal pH and total volatile fatty acid concentrations were not affected by dietary treatment. The urinary N excretion decreased linearly (P < 0.01) in response to increased levels of BR, with no dietary effect on N intake, N secretion in milk and fecal N excretion. Our results indicate that steam-flaked BR is a suitable replacement for steam-flaked corn in dairy cow diets, and that it can be included in rations to a level of at least 31.2% of dry matter without adverse effects on milk production, when cows were fed rice silage and corn silage-based diets.

Selection of barley grain affects ruminal fermentation, starch digestibility, and productivity of lactating dairy cows

The objective of this study was to evaluate the effects of 2 lots of barley grain cultivars differing in expected ruminal starch degradation on dry matter (DM) intake, ruminal fermentation, ruminal and total tract digestibility, and milk production of dairy cows when provided at 2 concentrations in the diet. Four primiparous ruminally cannulated (123 +/- 69 d in milk; mean +/- SD) and 4 multiparous ruminally and duodenally cannulated (46 +/- 14 d in milk) cows were used in a 4 x 4 Latin Square design with a 2 x 2 factorial arrangement of treatments with 16-d periods. Primiparous and multiparous cows were assigned to different squares. Treatments were 2 dietary starch concentrations (30 vs. 23% of dietary DM) and 2 lots of barley grain cultivars (Xena vs. Dillon) differing in expected ruminal starch degradation. Xena had higher starch concentration (58.7 vs. 50.0%) and greater in vitro 6-h starch digestibility (78.0 vs. 73.5%) compared with Dillon. All experimental diets were formulated to supply 18.3% crude protein and 20.0% forage neutral detergent fiber. Dry matter intake and milk yield were not affected by treatment. Milk fat concentration (3.55 vs. 3.29%) was greater for cows fed Dillon compared with Xena, but was not affected by dietary starch concentration. Ruminal starch digestion was greater for cows fed high-starch diets compared with those fed low-starch diets (4.55 vs. 2.49 kg/d), and tended to be greater for cows fed Xena compared with those fed Dillon (3.85 vs. 3.19 kg/d). Ruminal acetate concentration was lower, and propionate concentration was greater, for cows fed Xena or high-starch diets compared with cows fed Dillon or low-starch diets, respectively. Furthermore, cows fed Xena or high-starch diets had longer duration that ruminal pH was below 5.8 (6.6 vs. 4.0 and 6.4 vs. 4.2 h/d) and greater total tract starch digestibility (94.3 vs. 93.0 and 94.3 vs. 93.0%) compared with cows fed Dillon or low-starch diets, respectively. These results demonstrate that selection of barley grain can affect milk fat production and rumen fermentation to an extent at least as great as changes in dietary starch concentration.