M.L. Eastridge

Interactions of monensin with dietary fat and carbohydrate components on ruminal fermentation and production responses by dairy cows1

Variation in milk fat percentage resulting from monensin supplementation to lactating dairy cows could be due to altered ruminal fermentation with interactions of monensin with ruminal biohydrogenation of fat and ruminal carbohydrate availability. The objective of the study was to determine the effects of feeding monensin as Rumensin (R) in diets differing in starch availability (ground or steam-flaked corn), effective fiber (long or short alfalfa hay, LAH or SAH), and 4% fat (F) from distillers grains, roasted soybeans, and an animal-vegetable blend on ruminal fermentation characteristics and milk production in lactating dairy cows. Six ruminally cannulated lactating Holstein cows were used in a balanced 6×6 Latin square design with 21-d periods. The cows were fed 6 diets: (1) C=control diet with ground corn and LAH, (2) CR=C plus R, (3) CRFL=CR plus F, (4) CRFS=ground corn, R, F, and SAH, (5) SRFL=steam-flaked corn, R, F, and LAH, and (6) SRFS=steam-flaked corn, R, F, and SAH. Mean particle size of LAH was 5.00 mm and 1.36 mm for SAH. All diets were formulated to have 21% forage NDF and 40% NFC. The R tended to decrease DMI, decreased milk fat yield, and numerically lowered milk fat percentage (3.41 vs. 2.98%). Addition of F to R diets did not affect milk fat percentage. By feeding diets containing R and F, SAH tended to increase milk fat percentage for the ground-corn diet, but SAH tended to decrease milk fat percentage with steam-flaked corn (CRFL+SRFS vs. CRFS+SRFL). The steam-flaked corn increased total-tract NDF digestibility (CRFL + CRFS vs. SRFL+SRFS; 51.1 vs. 56%). Addition of F with R decreased total VFA concentration and increased rumen pH. Fat addition with R decreased rumen NH3N and MUN (12.8 vs. 13.9 mg/dL), and SFC decreased NH3N concentration compared with ground corn. Although R caused milk fat depression, addition of F did not further exacerbate milk fat depression. Fatty acid analysis did not implicate any particular biohydrogenation intermediate as the causative factor for the milk fat depression.

Investigation of ruminal bacterial diversity in dairy cattle fed supplementary monensin alone and in combination with fat, using pyrosequencing analysis.

The objective of this study was to examine and compare the effects of monensin, both alone and together with dietary fat, on ruminal bacterial communities in dairy cattle fed the following 3 diets: a control diet, the control diet supplemented with monensin, and the control diet supplemented with both monensin and fat. Bacterial communities in the liquid and the adherent fractions of rumen content were analyzed using 454 pyrosequencing analysis of 16S rRNA gene amplicons. Most sequences were assigned to phyla Firmicutes and Bacteroidetes, irrespective of diets and fractions. Prevotella was the most dominant genus, but most sequences could not be classified at the genus level. The proportion of Gram-positive Firmicutes was reduced by 4.5% in response to monensin but increased by 12.8% by combination of monensin and fat, compared with the control diet. Some of the operational taxonomic units in Firmicutes and Bacteroidetes were also affected by monensin or by the combination of monensin with fat. The proportion of numerous bacteria potentially involved in lipolysis and (or) biohydrogenation was increased by both monensin and fat. The Shannon diversity index was decreased in the control diet supplemented with both monensin and fat, compared with the other 2 diet groups. Supplementary fats hinder bacterial attachment to plant particles and then result in decreased bacterial diversity in the rumen. The finding of this study may help in understanding the effect of monensin and fat on ruminant nutrition and the adverse effect of monensin and fat, such as milk fat depression and decreased feed digestibility.

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.

Interaction of unsaturated fat or coconut oil with monensin in lactating dairy cows fed 12 times daily. II. Fatty acid flow to the omasum and milk fatty acid profile1

Feeding animal-vegetable (AV) fat or medium-chain fatty acids (FA) to dairy cows can decrease ruminal protozoal counts. However, combining moderate to large amounts of AV fat with monensin (tradename: Rumensin, R) could increase the risk for milk fat depression (MFD), whereas it is not known if diets supplemented with coconut oil (CNO; rich in medium-chain FA) with R would cause MFD. In a 6 × 6 Latin square design with a 2 × 3 factorial arrangement of treatments, 6 rumen-cannulated cows were fed diets without or with R (12 g/909 kg) and either control (no fat), 5% AV fat, or 5% CNO. Diets were balanced to have 21.5% forage neutral detergent fiber, 16.8% crude protein, and 42% nonfiber carbohydrates. Omasal flows of FA were characterized by an increased percentage of trans 18:1 for AV fat and CNO diets compared with the control, a higher percentage of 12:0 and 14:0 for CNO, and higher cis 18:1 for AV fat. Milk FA composition reflected the changes observed for omasal FA digesta flow. The de novo FA synthesis in the mammary gland was decreased by the main effects of R compared without R (averaged over fat treatments) and for added fat (AV fat and CNO) versus control (averaged over R). The percentages of 6:0, 8:0, and 10:0 in milk fat were lower for R and for AV fat and CNO compared with the control. The percentage of trans 18:1 FA in milk fat also higher for AV fat and CNO compared with the control. Against our hypotheses, the feeding of CNO did not prevent MFD, and few interactions between R and fat source were detected. The feeding of CNO did compromise ruminal biohydrogenation, with accumulation of trans 18:1 in the rumen and in milk fat.

Feeding tallow triglycerides of different saturation and particle size to lactating dairy cows

Abstract Five multiparious Holstein cows, arranged in a 5×5 Latin square design, were fed a control diet (no supplemental fat) and diets containing 5% of the following fat supplements: flaked tallow with a low iodine value of 14.4 (FTL), prilled tallow with a low iodine value of 14.5 (PTL), prilled tallow with a medium iodine value of 25.8 (PTM) and fancy bleachable tallow with a high iodine value of 62 (BTH). Diets consisted of 50% forage and 50% concentrate and the fat supplements replaced corn in the control diet. Diets were isonitrogenous and blood meal was added to provide a similar concentration of rumen undegradable protein among diets. Each period consisted of 28 days; 14 days were for adaptation and 14 days were for data collection. Intake and milk yield were similar among cows fed the hydrogenated fat sources. Fatty acid digestibility appeared to be lowest for flaked tallow but similar between the prilled tallow supplements. The fancy bleachable tallow depressed dry matter intake and milk fat percentage. Total tract digestibility of neutral detergent fiber was lower for fancy bleachable tallow (32.8%) than for prilled tallow with low iodine value (50.2%). Feeding 5% tallow with an iodine value of 62 appeared to have caused detrimental effects on ruminal fermentation and resulted in poor performance by the dairy cows. The prilled and flaked tallow fed in this study appeared to be ruminally inert, but flaked tallow may be of low digestibility.

INVITED REVIEW: Carbohydrate and fat: Considerations for energy and more

ABSTRACT Historically, carbohydrates and fats were valued on their caloric contributions to diets. Feeding recommendations for these feed fractions now address inclusion levels as well as consideration of the positive and negative effects of specific types of these nutrients. Feed carbohydrate characterization has expanded beyond fiber and nonfiber carbohydrates. Fiber now encompasses ADF, NDF, physically effective fiber, and fiber digestibility to describe effects on diet composition, rumination, rumen fill, potential fermentability, and nutrient contribution. The nonfiber carbohydrates are now parsed into sugars and fructans (both in water-soluble carbohydrates), starch, pectins, and others, all of which can differ in their effects on rumen pH or support of microbial growth. Dietary fat has the advantage of providing energy without increasing the risk of ruminal acidosis. However, there are specific considerations for amounts and types fed in high-versus low-forage diets. Fats can affect ruminal fermentation, having the potential to depress fiber digestion or affect ruminal methane production. Considerable research in recent years has focused on providing specific dietary fatty acids to alter the metabolic function of specific tissues or to alter the fatty acid content of milk for nutraceutical purposes. Rising grain prices and diversion of fats for biofuel are driving livestock industries to seek alternative nutrient sources. Most of the nutritional research on which current recommendations are based involved use of traditional diets that tended to be rich in grains. Fat and carbohydrate feeding recommendations might need to change with diets high in low-starch by-products. We need to learn how diets with substantially more by-product feedstuffs ferment and pass from the rumen and how they affect nutrient supply and feed efficiency. We can then better predict digestion and the effects on metabolism and thus target supplementation to have the greatest positive effect on food-animal production.

Jersey calf performance in response to high-protein, high-fat liquid feeds with varied fatty acid profiles: Intake and performance1

The objective of this study was to determine whether altering the fatty acid (FA) profile of milk replacer (MR) with coconut oil, which contains a high concentration of medium-chain FA, to more closely match the FA profile typically found in whole milk from Jersey cows, would improve Jersey calf performance. Male (n=18) and female (n=32) Jersey calves were assigned at birth to 1 of 4 liquid diets: (1) pasteurized Jersey saleable whole milk [pSWM; 27.9% crude protein (CP) and 33.5% fat]; (2) 29.3% CP and 29.1% fat MR, containing 100% of fat as edible lard (100:00); (3) 28.2% CP and 28.0% fat MR, containing 80% of fat as lard and 20% as coconut oil (80:20); and (4) 28.2% CP and 28.3% fat MR, containing 60% of the fat as lard and 40% as coconut oil (60:40). Calves were fed their respective liquid diet twice daily during wk 1 through 7 and once daily until weaning (approximately wk 8). Calves had ad libitum access to grain and water, and calves were monitored 1 wk postweaning. Average daily gain and body weight did not differ by treatment. Calves fed pSWM tended to have greater hip height (HH) than calves fed 80:20 (80.5 vs. 79.7 cm). Coconut oil tended to have a quadratic effect on HH, with calves fed 100:00, 80:20, and 60:40 at 79.2, 79.7, and 78.5 cm, respectively. No difference was observed in withers height between pSWM and 80:20. Coconut oil had a quadratic effect on withers height, with calves fed 100:00, 80:20, and 60:40 at 76.6, 77.5, and 76.5 cm, respectively. Change in HH from birth to 9 wk tended to be greater for calves fed pSWM than calves fed 80:20 (0.218 vs. 0.194 cm/d). Calves fed pSWM had higher milk dry matter intake (DMI) than calves fed 80:20 (0.580 vs. 0.518 kg/d). No effect of coconut oil was observed on milk DMI. Grain DMI and total DMI did not differ among treatments. Calves fed pSWM had an increase in days with a fecal score >2 compared with calves fed 80:20 (4.24 vs. 2.00 d). Coconut oil had a quadratic effect on fecal score, with calves fed 100:00, 80:20, and 60:40 scoring 4.00, 2.00, and 3.63 d, respectively. Respiratory score did not differ among treatments. In conclusion, DMI and average daily gain were similar among treatments. However, differences among treatments in skeletal growth and fecal scores are indicative of some possible benefits of medium-chain FA on calf health and performance.

Effects of different sources of physically effective fiber on rumen microbial populations

Physically effective fiber is needed by dairy cattle to prevent ruminal acidosis. This study aimed to examine the effects of different sources of physically effective fiber on the populations of fibrolytic bacteria and methanogens. Five ruminally cannulated Holstein cows were each fed five diets differing in physically effective fiber sources over 15 weeks (21 days/period) in a Latin Square design: (1) 44.1% corn silage, (2) 34.0% corn silage plus 11.5% alfalfa hay, (3) 34.0% corn silage plus 5.1% wheat straw, (4) 36.1% corn silage plus 10.1% wheat straw, and (5) 34.0% corn silage plus 5.5% corn stover. The impact of the physically effective fiber sources on total bacteria and archaea were examined using denaturing gradient gel electrophoresis. Specific real-time PCR assays were used to quantify total bacteria, total archaea, the genus Butyrivibrio, Fibrobacter succinogenes, Ruminococcus albus, Ruminococcus flavefaciens and three uncultured rumen bacteria that were identified from adhering ruminal fractions in a previous study. No significant differences were observed among the different sources of physical effective fiber with respect to the microbial populations quantified. Any of the physically effective fiber sources may be fed to dairy cattle without negative impact on the ruminal microbial community.

Jersey calf performance in response to high-protein, high-fat liquid feeds with varied fatty acid profiles: Blood metabolites and liver gene expression

Most available Jersey calf milk replacers (CMR) use edible lard as the primary fat source, which lacks medium-chain fatty acids (MCFA). However, Jersey cow milk consists of over 10% MCFA. The objective of this trial was to determine whether altering the fatty acid profile of CMR by increasing the amount of MCFA would alter liver lipid infiltration, liver gene expression, and blood metabolites when fed to Jersey calves. Fifty Jersey calves were fed 1 of 4 diets: pasteurized saleable whole milk (pSWM) from Jersey cows [27.9% crude protein (CP), 33.5% fat, dry matter (DM) basis]; CMR containing 100% of fat as edible lard (100:00; 29.3% CP, 29.1% fat, DM basis); CMR containing 20% of fat as coconut oil (CO; 80:20; 28.2% CP, 28.0% fat); or CMR containing 40% of fat as CO (60:40; 28.2% CP, 28.3% fat). Liquid diet DM intake averaged 0.523, 0.500, 0.498, and 0.512 kg/d for pSWM, 100:00, 80:20, and 60:40, respectively. Calves were fed their assigned liquid diet daily at 0600 and 1800 h from 2 d of age until 7 wk of age, and once daily until 8 wk of age. Calves were taken off trial at 9 wk of age. Calves had access to water and grain (23.8% CP, 2.71% fat, DM basis). Grain DM intake averaged 0.386, 0.439, 0.472, and 0.454 kg/d for pSWM, 100:00, 80:20, and 60:40, respectively. Liver biopsy cores were obtained from 15 calves at 42 d of age (pSWM, n=4; 100:00, n=4; 80:20, n=3; 60:40, n=4) and from 4 baseline calves <2d of age. Liver biopsy cores were used for histological appraisal of lipid infiltration and gene expression analyses of short-, medium-, and long- chain acyl-coenzyme A dehydrogenases, sterol regulatory element binding transcription factor 1, acetyl coenzyme A carboxylase, and fatty acid synthase. Lipid infiltration and expression of selected genes were not different among diets. After an overnight fast, weekly blood samples were taken immediately before feeding at 0600 h via jugular venipuncture in all calves. Serum and plasma obtained from blood samples were used in the analyses of total protein, glucose, triglycerides, nonesterified fatty acids, and plasma urea nitrogen (PUN). Nonesterified fatty acids and PUN were the only blood metabolites affected solely by diet. Nonesterified fatty acids decreased in a linear manner with increased dietary CO inclusion. Calves fed pSWM had higher PUN than calves fed 80:20. In this trial, altering the fatty acid profile of CMR with the addition of medium-chain fatty acids from CO had minimal effects on liver lipid infiltration, liver gene expression, and blood metabolites when fed to Jersey calves.

Dairy nutrition management: Assessing a comprehensive continuing education program for veterinary practitioners

The purpose of this study was to assess the effectiveness of a team-based educational program designed to enhance the flow of applied, research-based, nutrition information to dairy veterinarians. A comprehensive dairy cattle nutrition curriculum was developed and participants from 11 veterinary practices located in 5 states (IN, NY, PA, NM, and OH), serving an estimated 186,150 dairy cattle in 469 herds, attended the 2 advanced nutrition modules (∼2.5 d each and ∼40 h of learning) held in 2009. Nutrients, feeding transition cows, calves, and heifers, dry matter intake, feed storage, metabolic diseases, evaluating cows (scoring body condition, manure, and lameness), metabolic blood profiles, and feeding behavior were discussed. Educational materials were delivered through in-class lectures, followed by case-based learning and group discussions. A farm visit and out-of-class assignments were also implemented. Attendees were assessed using pre- and post-tests of knowledge to determine the level of knowledge gained in both nutrition modules. Participants evaluated the program and provided feedback at the conclusion of each module. Veterinarians (100%) reported that the overall program, presentations, and discussions were useful. Attendees found the presented information relevant for their work (agree=60% and strongly agree=40%) and of great immediate use to them (neutral=6.5%, agree=56%, and strongly agree=37.5%). The presented materials and the implemented educational delivery methods substantially increased the knowledge level of the attendees (16.9% points increase from pre-test to post-test scores). Importance of feed particle size, ration evaluation, interpreting feed analysis, balancing carbohydrate components, and metabolic profiling in fresh cows were listed as learned concepts that participants could apply in their practices. Results suggested that both nutrition modules were relevant and effective, offering new information with immediate field application. This program has important implications for dairy veterinarians because they serve as a vital source of information for dairy producers.