Short communication: Analytical method and amount of preservative added to milk samples may alter milk urea nitrogen measurements.

Milk urea N (MUN) is used by dairy nutritionists and producers to monitor dietary protein intake and is indicative of N utilization in lactating dairy cows. Two experiments were conducted to explore discrepancies in MUN results provided by 3 milk processing laboratories using different methods. An additional experiment was conducted to evaluate the effect of 2-bromo-2-nitropropane-1, 3-diol (bronopol) on MUN analysis.

Short communication: Preference for flavored concentrate premixes by dairy cows.

Flavor preferences may be used to stimulate feed intake in dairy cows, which may improve use of robotic milking systems and increase feed intake of sick cows. A cafeteria-design experiment was used to determine if dairy cows have flavor preferences. Sixteen lactating Holstein cows averaging 197±32d in milk, 1.

Short communication: Comparison of the GreenFeed system with the sulfur hexafluoride tracer technique for measuring enteric methane emissions from dairy cows.

The objective of this study was to compare 2 commonly used techniques for measuring methane emissions from ruminant animals: the GreenFeed (GF) system and the sulfur hexafluoride (SF6) technique. The study was part of a larger experiment in which a methane inhibitor, 3-nitrooxypropanol, fed at 4 application rates (0, 40, 60, and 80 mg/kg of feed dry matter) decreased enteric methane emission by an average of 30% (measured by both GF and SF6) in a 12-wk experiment with 48 lactating Holstein cows fed a total mixed ration. The larger experiment used a randomized block design and was conducted in 2 phases (February to May, phase 1, and June to August, phase 2), with 2 sets of 24 cows in each phase.

Effect of 3-nitrooxypropanol on methane and hydrogen emissions, methane isotopic signature, and ruminal fermentation in dairy cows.

The objective of this crossover experiment was to investigate the effect of a methane inhibitor, 3-nitrooxypropanol (3NOP), on enteric methane emission, methane isotopic composition, and rumen fermentation and microbial profile in lactating dairy cows. The experiment involved 6 ruminally cannulated late-lactation Holstein cows assigned to 2 treatments: control and 3NOP (60 mg/kg of feed dry matter). Compared with the control, 3NOP decreased methane emission by 31% and increased hydrogen emission from undetectable to 1.

Effects of rumen-protected methionine, lysine, and histidine on lactation performance of dairy cows.

The objective of this study was to evaluate the effects of supplementing a metabolizable protein (MP)-deficient diet with rumen-protected (RP) Met, Lys, and His, individually or combined, on the performance of lactating dairy cows. The experiment was a 9-wk randomized complete block design with 72 Holstein cows. Following a 2-wk covariate period, cows were blocked by days in milk, milk yield, and parity, and randomly assigned to 1 of the following 6 treatments: (1) MP-adequate diet [MPA; +243g/d MP balance, according to the National Research Council (2001) requirements]; (2) MP-deficient diet (MPD; -54g/d MP balance); (3) MPD supplemented with RPMet (MPDM); (4) MPD supplemented with RPLys (MPDL); (5) MPD supplemented with RPHis (MPDH); and (6) MPD supplemented with RPMet, RPLys, and RPHis (MPDMLH).

Extruded soybean meal increased feed intake and milk production in dairy cows.

The objective of this study was to assess the effects of 2 extruded soybean meals (ESBM) processed at 2 extruder temperatures, 149°C (LTM) and 171°C (HTM), on performance, nutrient digestibility, milk fatty acid and plasma amino acid profiles, and rumen fermentation in lactating dairy cows. Nine multiparous Holstein cows were included in a replicated 3×3 Latin square design experiment with three 28-d periods. The control diet contained 13% solvent-extracted soybean meal (SSBM; 53.

Effects of dietary Capsicum oleoresin on productivity and immune responses in lactating dairy cows.

This study investigated the effect of Capsicum oleoresin in granular form (CAP) on nutrient digestibility, immune responses, oxidative stress markers, blood chemistry, rumen fermentation, rumen bacterial populations, and productivity of lactating dairy cows. Eight multiparous Holstein cows, including 3 ruminally cannulated, were used in a replicated 4×4 Latin square design experiment. Experimental periods were 25 d in duration, including a 14-d adaptation and an 11-d data collection and sampling period.

Effect of technical cashew nut shell liquid on rumen methane emission and lactation performance of dairy cows.

Technical-grade cashew nut shell liquid (TCNSL) is a by-product of the cashew nut industry in tropical countries, and is known to exhibit a wide range of biological activities, including inhibitory effect against gram-positive bacteria. This study was conducted to investigate the effects of TCNSL (73.3% cardanol, 16.

Effects of slow-release urea and rumen-protected methionine and histidine on performance of dairy cows.

This experiment was conducted with the objective to investigate the effects of slow-release urea and rumen-protected (RP) Met and His supplementation of a metabolizable protein (MP)-deficient diet (according to NRC, 2001) on lactation performance of dairy cows. Sixty lactating Holstein cows were used in a 10-wk randomized complete block-design trial. Cows were fed a covariate diet for 2 wk and then assigned to one of the following treatments for an 8-wk experimental period: (1) MP-adequate diet [AMP; 107% of MP requirements, based on the National Research Council (NRC, 2001)]; (2) MP-deficient diet (DMP; 95% of MP requirements); (3) DMP supplemented with slow-release urea (DMPU); (4) DMPU supplemented with RPMet (DMPUM); and (5) DMPUM supplemented with RPHis (DMPUMH).

Effect of dietary protein level and rumen-protected amino acid supplementation on amino acid utilization for milk protein in lactating dairy cows.

This study investigated the effect of metabolizable protein (MP) supply and rumen-protected (RP) Lys and Met supplementation on productivity, nutrient digestibility, urinary N losses, apparent total-tract digestibility of dietary AA, and the efficiency of AA utilization for milk protein synthesis in dairy cows. The experiment was conducted with 8 ruminally cannulated Holstein cows in a replicated 4×4 Latin square design trial with 21-d periods. Treatments were (1) MP-adequate diet (AMP; MP balance of -24 g/d); (2) MP-deficient diet (DMP; MP balance of -281 g/d); (3) DMP supplemented with 100 g of RPLys/cow per day (estimated digestible Lys supply=24 g/d; DMPL; MP balance of -305g/d); and (4) DMPL supplemented with 24 g of RPMet/cow per day (estimated digestible Met supply=15 g/d; DMPLM; MP balance of -256g/d).

Effect of 2-hydroxy-4-methylthio-butanoic acid on ruminal fermentation, bacterial distribution, digestibility, and performance of lactating dairy cows.

The objective of this experiment was to test the effect of a Met analog, 2-hydroxy-4-methylthio-butanoic acid (HMTBa), on ruminal fermentation and microbial protein synthesis, nutrient digestibility, urinary N losses, and performance of dairy cows. Eight multiparous lactating Holstein dairy cows were assigned to 4 levels of HMTBa [0 (control), 0.05, 0.

Short communication: Comparison of 3 solid digesta passage markers in dairy cows.

This study investigated the usefulness of acid-detergent fiber-bound (15)N [acid detergent insoluble (ADI)-(15)N] as a solid digesta passage marker in dairy cows compared with chromium (Cr) and ytterbium (Yb) (as labeled fiber or forage, respectively). Intrinsically (ADI-(15)N) or extrinsically (Cr, Yb) labeled alfalfa hay was pulse-dosed intraruminally to 7 lactating dairy cows. Following marker administration, spot fecal samples were collected for up to 72 h for marker analyses.

A meta-analysis of variability in continuous-culture ruminal fermentation and digestibility data.

A meta-analysis was conducted to compare ruminal fermentation and digestibility data and variability between continuous-culture (CC) experiments and in vivo data. One hundred eighty CC studies representing 1,074 individual treatments, published in refereed journals between 1980 and 2010 were used in this analysis. Studies were classified into 2 groups based on the type of CC used: CC systems specified as rumen simulation techniques (RUSITEC) and non-RUSITEC CC systems (non-RUSITEC).

Effects of metabolizable protein supply and amino acid supplementation on nitrogen utilization, milk production, and ammonia emissions from manure in dairy cows.

Two experiments were conducted with the objective of investigating the effects of rumen-protected methionine (RPMet) supplementation of metabolizable protein (MP)-deficient or MP-adequate but Met-deficient diets on dairy cow performance. Experiment (Exp.) 1 utilized 36 Holstein dairy cows blocked in 12 blocks of 3 cows each.