Genetic background of methane emission by Dutch Holstein Friesian cows measured with infrared sensors in automatic milking systems

International environmental agreements have led to the need to reduce methane emission by dairy cows. Reduction could be achieved through selective breeding. The aim of this study was to quantify the genetic variation of methane emission by Dutch Holstein Friesian cows measured using infrared sensors installed in automatic milking systems (AMS). Measurements of CH₄ and CO₂ on 1,508 Dutch Holstein Friesian cows located on 11 commercial dairy farms were available. Phenotypes per AMS visit were the mean of CH₄, mean of CO₂, mean of CH₄ divided by mean of CO₂, and their log₁₀-transformations. The repeatabilities of the log₁₀-transformated methane phenotypes were 0.27 for CH₄, 0.31 for CO₂, and 0.14 for the ratio. The log₁₀-transformated heritabilities of these phenotypes were 0.11 for CH₄, 0.12 for CO₂, and 0.03 for the ratio. These results indicate that measurements taken using infrared sensors in AMS are repeatable and heritable and, thus, could be used for selection for lower CH₄ emission. Furthermore, it is important to account for farm, AMS, day of measurement, time of day, and lactation stage when estimating genetic parameters for methane phenotypes. Selection based on log₁₀-transformated CH₄ instead of the ratio would be expected to give a greater reduction of CH₄ emission by dairy cows.     

Prediction of methane emission from lactating dairy cows using milk fatty acids and mid‐infrared spectroscopy

Enteric methane (CH₄) production is among the main targets of greenhouse gas mitigation practices for the dairy industry. A simple, robust and inexpensive measurement technique applicable on a large scale to estimate CH₄ emission from dairy cattle would therefore be valuable. Milk fatty acids (MFA) are related to CH₄ production because of the common biochemical pathway between CH₄ and fatty acids in the rumen. A summary of studies that investigated the predictive power of MFA composition for CH₄ emission indicated good potential, with predictive power ranging between 47% and 95%. Until recently, gas chromatography (GC) was the principal method used to determine the MFA profile, but GC is unsuitable for routine analysis. This has led to the application of mid‐infrared (MIR) spectroscopy. The major advantages of using MIR spectroscopy to predict CH₄ emission include its simplicity and potential practical application at large scale. Disadvantages include the inability to predict important MFA for CH₄ prediction, and the moderate predictive power for CH₄ emission. It may not be sufficient to predict CH₄ emission based on MIR alone. Integration with other factors, like feed intake, nutrient composition of the feed, parity, and lactation stage may improve the prediction of CH₄ emission using MIR spectra. © 2016 Society of Chemical Industry     

Technical note: Near infrared reflectance spectroscopy to predict fecal indigestible neutral detergent fiber for dairy cows

In vitro and in situ procedures performed to estimate indigestible neutral detergent fiber (iNDF) in forage or fecal samples are time consuming, costly, and limited by intrinsic factors. In contrast, near infrared reflectance spectroscopy (NIRS) has become widely recognized as a valuable tool for accurately determining chemical composition and digestibility parameters of forages. The aim of this study was to build NIRS calibrations and equations for fecal iNDF. In total, 1,281 fecal samples were collected to build a calibration data set, but only 301 were used to develop equations. Once dried, samples were ground and chemically analyzed for crude protein, ash, amylase and sodium sulfite–treated NDF corrected for ash residue (aNDFom), acid detergent fiber, acid detergent lignin, and in vitro digestion at 240 h to estimate iNDF (uNDF240). Each fecal sample was scanned using a NIRSystem 6500 instrument (Perstorp Analytical Inc., Silver Spring, MD). Spectra selection was performed, resulting in 301 sample spectra used to develop regression equations with good accuracy and low standard error of prediction. The standard error of calibration (SEC), cross validation (SECV), and coefficients of determination for calibration (R²) and for cross validation (1 ? VR, where VR = variance ratio) were used to evaluate calibration and validation results. Moreover, the ratio performance deviation (RPD) and ratio of the range of the original data to SECV (range/SECV; range error ratio, RER) were also used to evaluate calibration and equation performance. Calibration data obtained on fiber fractions aNDFom (R² = 0.92, 1 ? VR = 0.87, SEC = 1.48, SECV = 1.89, RPD = 2.80, and RER = 20.19), uNDF240 (R² = 0.92, 1 ? VR = 0.86, SEC = 1.65, SECV = 2.24, RPD = 2.57, and RER = 14.30), and in vitro rumen aNDFom digestibility at 240 h (R² = 0.90, 1 ? VR = 0.85, SEC = 2.68, SECV = 3.43, RPD = 2.53, and RER = 14.0) indicated the predictive equations had good predictive value.     

Association between days open and milk spectral data in dairy cows

Data on 19,489 Brown Swiss cows reared in northeastern Italy were used to associate absorbances of individual wavenumbers within the mid-infrared range with days open (DO). Different postcalving days in milk (DIM) intervals were studied to determine the most informative milk sampling periods for predicting DO. Milk samples were analyzed using a MilkoScan (Foss Electric, Hillerød, Denmark) Fourier-transform infrared (FTIR) spectrometer for 1,060 wavenumbers (wn) ranging from 5,011 to 925 cm^?1. To determine DO, we considered an insemination to lead to conception when there was no return of heat (i.e., no successive insemination) and the cow had a subsequent calving date whereby gestation length was required to be within ±30 d of 290 d. Only milk records within the first 90 DIM were considered. Associations were inferred by (1) fitting linear regression models between the DO and each individual wavenumber or milk component, and (2) fitting a Bayesian regression model that included the complete FTIR spectral data. The effects of including systematic effects (parity number, year-season, herd) in the model on these associations were also studied. These analyses were performed for the complete data (5–90 DIM) and for data stratified by DIM period (5 to 30, 31 to 60, and 61 to 90 DIM). Overall, regions of wavenumbers of the milk FTIR spectra that were associated with DO included wn 2,973 to 2,830 cm^?1 [related to fat-B (C-H stretch)], wn 2,217 to 1,769 cm^?1 [related to fat-A (C = O stretch)], wn 1,546 cm^?1 (related to protein), wn 1,465 cm^?1 (related to urea and fat), wn 1,399 to 1,245 cm^?1 (related to acetone), and wn 1,110 cm^?1 (related to lactose). Estimated effects depended on the DIM period, with milk samples drawn during DIM intervals 31 to 60 d and 61 to 90 d being most strongly associated with DO. These DIM intervals are also typically most associated with negative energy balance and peak lactation.     

Patterns of Fourier-transform infrared estimated milk constituents in early lactation Holstein cows on a single New York State dairy

Cows undergo immense physiological stress to produce milk during early lactation. Monitoring early lactation milk through Fourier-transform infrared (FTIR) spectroscopy might offer an understanding of which cows transition successfully. Daily patterns of milk constituents in early lactation have yet to be reported continuously, and the study objective was to initially describe these patterns for cows of varying parity groups from 3 through 10 d postpartum, piloted on a single dairy. We enrolled 1,024 Holstein cows from a commercial dairy farm in Cayuga County, New York, in an observational study, with a total of 306 parity 1 cows, 274 parity 2 cows, and 444 parity ≥3 cows. Cows were sampled once daily, Monday through Friday, via proportional milk samplers, and milk was stored at 4°C until analysis using FTIR. Estimated constituents included anhydrous lactose, true protein, and fat (g/100 g of milk); relative % (rel%) of total fatty acids (FA) and concentration (g/100 g of milk) of de novo, mixed, and preformed FA; individual fatty acids C16:0, C18:0, and C18:1 cis-9 (g/100 g of milk); milk urea nitrogen (MUN; mg/100 g of milk); and milk acetone (mACE), milk β-hydroxybutyrate (mBHB), and milk-predicted blood nonesterified fatty acids (mpbNEFA) (all expressed in mmol/L). Differences between parity groups were assessed using repeated-measures ANOVA. Milk yield per milking differed over time between 3 and 10 DIM and averaged 8.7, 13.3, and 13.3 kg for parity 1, 2, and ≥3 cows, respectively. Parity differences were found for % anhydrous lactose, % fat, and preformed FA (g/100 g of milk). Parity differed across DIM for % true protein, de novo FA (rel% and g/100 g of milk), mixed FA (rel% and g/100 g of milk), preformed FA rel%, C16:0, C18:0, C18:1 cis-9, MUN, mACE, mBHB, and mpbNEFA. Parity 1 cows had less true protein and greater fat percentages than parity 2 and ≥3 cows (% true protein: 3.52, 3.76, 3.81; % fat: 5.55, 4.69, 4.95, for parity 1, 2, ≥3, respectively). De novo and mixed FA rel% were reduced and preformed FA rel% were increased in primiparous compared with parity 2 and ≥3 cows. The increase in preformed FA rel% in primiparous cows agreed with milk markers of energy deficit, such that mpbNEFA, mBHB, and mACE were greatest in parity 1 cows followed by parity ≥3 cows, with parity 2 cows having the lowest concentrations. When measuring milk constituents with FTIR, these results suggest it is critical to account for parity for the majority of estimated milk constituents. We acknowledge the limitation that this study was conducted on a single farm; however, if FTIR technology is to be used as a method of identifying cows maladapted to lactation, understanding variations in early lactation milk constituents is a crucial first step in the practical adoption of this technology.     

Genetic parameters for methane emission traits in Australian dairy cows

Methane is a greenhouse gas of high interest to the dairy industry, with 57% of Australia's dairy emissions attributed to enteric methane. Enteric methane emissions also constitute a loss of approximately 6.5% of ingested energy. Genetic selection offers a unique mitigation strategy to decrease the methane emissions of dairy cattle, while simultaneously improving their energy efficiency. Breeding objectives should focus on improving the overall sustainability of dairy cattle by reducing methane emissions without negatively affecting important economic traits. Common definitions for methane production, methane yield, and methane intensity are widely accepted, but there is not yet consensus for the most appropriate method to calculate residual methane production, as the different methods have not been compared. In this study, we examined 9 definitions of residual methane production. Records of individual cow methane, dry matter intake (DMI), and energy corrected milk (ECM) were obtained from 379 animals and measured over a 5-d period from 12 batches across 5 yr using the SF₆ tracer method and an electronic feed recording system, respectively. The 9 methods of calculating residual methane involved genetic and phenotypic regression of methane production on a combination of DMI and ECM corrected for days in milk, parity, and experimental batch using phenotypes or direct genomic values. As direct genomic values (DGV) for DMI are not routinely evaluated in Australia at this time, DGV for FeedSaved, which is derived from DGV for residual feed intake and estimated breeding value for bodyweight, were used. Heritability estimates were calculated using univariate models, and correlations were estimated using bivariate models corrected for the fixed effects of year-batch, days in milk, and lactation number, and fitted using a genomic relationship matrix. Residual methane production candidate traits had low to moderate heritability (0.10 ± 0.09 to 0.21 ± 0.10), with residual methane production corrected for ECM being the highest. All definitions of residual methane were highly correlated phenotypically (>0.87) and genetically (>0.79) with one another and moderately to highly with other methane candidate traits (>0.59), with high standard errors. The results suggest that direct selection for a residual methane production trait would result in indirect, favorable improvement in all other methane traits. The high standard errors highlight the importance of expanding data sets by measuring more animals for their methane emissions and DMI, or through exploration of proxy traits and combining data via international collaboration.     

Technical note: Evaluation of interval between measurements and calculation method for the quantification of enteric methane emissions measured by respiration chamber

Respiration chambers share one analyzer working in parallel, and methane (CH₄) concentrations have to be measured at certain intervals. The maximum and minimum values in the kinetics of CH₄ emissions can be missed during the interval between measurements, which may influence the quantification of CH₄ emissions. Chambers must be opened for morning feeding and cleaning, which causes a loss of CH₄ data. Calculation methods are needed to estimate the lost CH₄ emission data, which may influence the estimated amount of daily CH₄ emissions. In this study, we measured the CH₄ emissions of 10 growing Chinese Holstein dairy heifers in respiration chambers. Methane concentrations were measured every 0.5 min to obtain the 23-h kinetics of CH₄ emissions, which were further selected at different intervals between measurements (i.e., 5, 30, 60, 120, 180, and 240 min) to evaluate the effects of interval on quantification of CH₄ emissions. The missing 1-h kinetics of CH₄ emissions before feeding were not measured, and 2 calculation methods were used to estimate the missing 1-h kinetics of CH₄ emissions: mean value of measuring period (the mean method) and the nearest value of measurement just before chamber opening (the nearest method). The results showed that the rates of CH₄ emission from 10 heifers varied from 4.56 to 11.42 g/h. The increment of intervals decreased maximum rate of CH₄ emission and increased minimum rate of CH₄ emission. Interval caused less than 5% of the difference in measuring CH₄ emissions. Although the mean method had greater estimated daily CH₄ emission than the nearest method, the difference was within 3%. The interval between measurements (≤3 h) and calculation method had little influence on enteric CH₄ emission measurements.     

Long-term effects of feeding monensin on methane production in lactating dairy cows

The objective of this study was to determine the long-term effects of feeding monensin on methane (CH₄) production in lactating dairy cows. Twenty-four lactating Holstein dairy cows (1.46 ± 0.17 parity; 620 ± 5.9 kg of live weight; 92.5 ± 2.62 d in milk) housed in a tie-stall facility were used in the study. The study was conducted as paired comparisons in a completely randomized design with repeated measurements in a color-coded, double-blind experiment. The cows were paired by parity and days in milk and allocated to 1 of 2 treatments: 1) the regular milking cow total mixed ration (TMR) with a forage-to-concentrate ratio of 60:40 (control TMR; placebo premix) vs. a medicated TMR (monensin TMR; regular TMR + 24 mg of Rumensin Premix/kg of dry matter) fed ad libitum. The animals were fed and milked twice daily (feeding at 0830 and 1300 h; milking at 0500 and 1500 h) and CH₄ production was measured prior to introducing the treatments and monthly thereafter for 6 mo using an open-circuit indirect calorimetry system. Monensin reduced CH₄ production by 7% (expressed as grams per day) and by 9% (expressed as grams per kilogram of body weight), which were sustained for 6 mo (mean, 458.7 vs. 428.7 ± 7.75 g/d and 0.738 vs. 0.675 ± 0.0141, control vs. monensin, respectively). Monensin reduced milk fat percentage by 9% (3.90 vs. 3.53 ± 0.098%, control vs. monensin, respectively) and reduced milk protein by 4% (3.37 vs. 3.23 ± 0.031%, control vs. monensin, respectively). Monensin did not affect the dry matter intake or milk yield of the cows. These results suggest that medicating a 60:40 forage-to-concentrate TMR with 24 mg of Rumensin Premix/kg of dry matter is a viable strategy for reducing CH₄ production in lactating Holstein dairy cows.     

Diagnosing pregnancy status using infrared spectra and milk composition in dairy cows

Data on Holstein (16,890), Brown Swiss (31,441), Simmental (25,845), and Alpine Grey (12,535) cows reared in northeastern Italy were used to assess the ability of milk components (fat, protein, casein, and lactose) and Fourier transform infrared (FTIR) spectral data to diagnose pregnancy. Pregnancy status was defined as whether a pregnancy was confirmed by a subsequent calving and no other subsequent inseminations within 90 d of the breeding of specific interest. Milk samples were analyzed for components and FTIR full-spectrum data using a MilkoScan FT+ 6000 (Foss Electric, Hillerød, Denmark). The spectrum covered 1,060 wavenumbers (wn) from 5,010 to 925 cm^?1. Pregnancy status was predicted using generalized linear models with fat, protein, lactose, casein, and individual FTIR spectral bands or wavelengths as predictors. We also fitted a generalized linear model as a simultaneous function of all wavelengths (1,060 wn) with a Bayesian variable selection model using the BGLR R-package (https://r-forge.r-project.org/projects/bglr/). Prediction accuracy was determined using the area under a receiver operating characteristic curve based on a 10-fold cross-validation (CV-AUC) assessment based on sensitivities and specificities of phenotypic predictions. Overall, the best prediction accuracies were obtained for the model that included the complete FTIR spectral data. We observed similar patterns across breeds with small differences in prediction accuracy. The highest CV-AUC value was obtained for Alpine Grey cows (CV-AUC = 0.645), whereas Brown Swiss and Simmental cows had similar performance (CV-AUC = 0.630 and 0.628, respectively), followed by Holsteins (CV-AUC = 0.607). For single-wavelength analyses, important peaks were detected at wn 2,973 to 2,872 cm^?1 where Fat-B (C-H stretch) is usually filtered, wn 1,773 cm^?1 where Fat-A (C=O stretch) is filtered, wn 1,546 cm^?1 where protein is filtered, wn 1,468 cm^?1 associated with urea and fat, wn 1,399 and 1,245 cm^?1 associated with acetone, and wn 1,025 to 1,013 cm^?1 where lactose is filtered. In conclusion, this research provides new insight into alternative strategies for pregnancy screening of dairy cows.     

Performance and methane emissions in dairy cows fed oregano and green tea extracts as feed additives

Plant extracts have been proposed as substitutes for chemical feed additives due to their potential as rumen fermentation modifiers and because of their antimicrobial and antioxidant activities, possibly reducing methane emissions. This study aimed to evaluate the use of oregano (OR), green tea extracts (GT), and their association as feed additives on the performance and methane emissions from dairy between 28 and 87 d of lactation. Thirty-two lactating dairy cows, blocked into 2 genetic groups: 16 Holstein cows and 16 crossbred Holstein-Gir, with 522.6 ± 58.3 kg of body weight, 57.2 ± 20.9 d in lactation, producing 27.5 ± 5.0 kg/cow of milk and with 3.1 ± 1.8 lactations were evaluated (means ± standard error of the means). Cows were allocated into 4 treatments: control (CON), without plant extracts in the diet; oregano extract (OR), with the addition of 0.056% of oregano extract in the dry matter (DM) of the diet; green tea (GT), with the addition of 0.028% of green tea extract in the DM of the diet; and mixture, with the addition of 0.056% oregano extract and 0.028% green tea extract in the DM of the diet. The forage-to-concentrate ratio was 60:40. Forage was composed of corn silage (94%) and Tifton hay (6%); concentrate was based on ground corn and soybean meal. Plant extracts were supplied as powder, which was previously added and homogenized into 1 kg of concentrate in natural matter, top-dressed onto the total mixed diet. No treatment by day interaction was observed for any of the evaluated variables, but some block by treatment interactions were significant. In Holstein cows, the mixture treatment decreased gross energy and tended to decrease the total-tract apparent digestibility coefficient for crude protein and total digestible nutrients when compared with OR. During the gas measurement period, GT and OR increased the digestible fraction of the ingested DM and decreased CH₄ expressed in grams per kilogram of digestible DMI compared with CON. The use of extracts did not change rumen pH, total volatile fatty acid concentration, milk yield, or most milk traits. Compared with CON, oregano addition decreased fat concentration in milk. The use of plant extracts altered some milk fatty acids but did not change milk fatty acids grouped according to chain length (short or long), saturation (unsaturated or saturated), total conjugated linoleic acids, and n-3 and n-6 contents. Green tea and oregano fed separately reduced gas emission in cows during the first third of lactation and have potential to be used as feed additives for dairy cows.     

Persistency of methane mitigation by dietary nitrate supplementation in dairy cows

Feeding nitrate to dairy cows may lower ruminal methane production by competing for reducing equivalents with methanogenesis. Twenty lactating Holstein-Friesian dairy cows (33.2 ± 6.0 kg of milk/d; 104 ± 58 d in milk at the start of the experiment) were fed a total mixed ration (corn silage-based; forage to concentrate ratio 66:34), containing either a dietary urea or a dietary nitrate source [21 g of nitrate/kg of dry matter (DM)] during 4 successive 24-d periods, to assess the methane-mitigating potential of dietary nitrate and its persistency. The study was conducted as paired comparisons in a randomized design with repeated measurements. Cows were blocked by parity, lactation stage, and milk production at the start of the experiment. A 4-wk adaptation period allowed the rumen microbes to adapt to dietary urea and nitrate. Diets were isoenergetic and isonitrogenous. Methane production, energy balance, and diet digestibility were measured in open-circuit indirect calorimetry chambers. Cows were limit-fed during measurements. Nitrate persistently decreased methane production by 16%, whether expressed in grams per day, grams per kilogram of dry matter intake (DMI), or as percentage of gross energy intake, which was sustained for the full experimental period (mean 368 vs. 310 ± 12.5 g/d; 19.4 vs. 16.2 ± 0.47 g/kg of DMI; 5.9 vs.4.9 ± 0.15% of gross energy intake for urea vs. nitrate, respectively). This decrease was smaller than the stoichiometrical methane mitigation potential of nitrate (full potential = 28% methane reduction). The decreased energy loss from methane resulted in an improved conversion of dietary energy intake into metabolizable energy (57.3 vs. 58.6 ± 0.70%, urea vs. nitrate, respectively). Despite this, milk energy output or energy retention was not affected by dietary nitrate. Nitrate did not affect milk yield or apparent digestibility of crude fat, neutral detergent fiber, and starch. Milk protein content (3.21 vs. 3.05 ± 0.058%, urea vs. nitrate respectively) but not protein yield was lower for dietary nitrate. Hydrogen production between morning and afternoon milking was measured during the last experimental period. Cows fed nitrate emitted more hydrogen. Cows fed nitrate displayed higher blood methemoglobin levels (0.5 vs. 4.0 ± 1.07% of hemoglobin, urea vs. nitrate respectively) and lower hemoglobin levels (7.1 vs. 6.3 ± 0.11 mmol/L, urea vs. nitrate respectively). Dietary nitrate persistently decreased methane production from lactating dairy cows fed restricted amounts of feed, but the reduction in energy losses did not improve milk production or energy balance.     

Technical note: A simple back-mounted harness for grazing dairy cows to facilitate the sulfur hexafluoride tracer gas technique

We describe here a cattle harness to attach a gas collection vessel to facilitate the sulfur hexafluoride (SF₆) tracer gas technique. The harness consists of 2 major components: (1) a lightweight, robust body fabricated from an equine surcingle or lunge roller with padded thoracic trapezius pressure points, a bespoke shaping shaft for spine support, and adjustable buckles on both sides; and (2) an elastic flank-strap to prevent the harness from dislodging. The spine support consists of stainless steel laminated with carbon fiber. This support minimizes the contact area with the animal's skin, relieves the spine area of pressure, and creates free flow of ambient air below the platform, reducing sweat accumulation and hence preventing skin lesions. The harness weighs approximately 1.2 kg, allows for attachment of 2 gas collection vessels (animal and background sample), and is cost effective.     

Measurement of rumen dry matter and neutral detergent fiber degradability of feeds by Fourier-transform infrared spectroscopy

This study explored the potential of partial least squares (PLS) and Fourier-transform infrared spectroscopy (FTIR) to predict rumen dry matter (DM) and neutral detergent fiber (NDF) degradation parameters of a wide range of feeds for ruminants, as an alternative to the in situ method. In total, 663 samples comprising 80 different feed types were analyzed. In situ DM and NDF degradabilities were determined as follows: effective degradability (ED), rumen soluble fraction (A), degradable but not soluble fraction (B), rate of degradation of the B fraction (C), and indigestible NDF (iNDF). Infrared spectra of dry samples were collected by attenuated total reflectance from 600 to 4000 cm⁻¹. Feeds were randomly classified into 2 subsets of samples with representation of all feed types; one subset was used to develop regression models using partial least squares, and the second subset was used to conduct an external validation of the models. This study indicated that universal models containing all feed types and specific models containing concentrate feeds could provide only a relatively poor estimation of in situ DM degradation parameters because of compositional heterogeneity. More research, such as a particle size distribution analysis, is required to determine whether this lack of accuracy was due to limitations of the FTIR approach, or simply due to methodological error associated with the in situ method. This latter hypothesis may explain the low accuracy observed in the prediction of degradation rates if there was physical leakage of fine particles from the mesh bags used during in situ studies. In contrast, much better predictions were obtained when models were developed for forage feeds alone. Models for forages led to accurate predictions of DM_A, DM_B, NDF_ED, and NDF concentration (R² = 0.91, 0.89, 0.85, and 0.79, standard error = 4.34, 5.97, 4.59, and 4.41% of DM, respectively), and could be used for screening of DM_ED, NDF_C, and iNDF. These models relied on certain regions of the FTIR spectrum (900–1150 and 1500–1700 cm⁻¹), which are mainly compatible with absorption of plant cell wall components, such as cellulose, pectin, lignin, cutin, and suberin, but also with nonstructural carbohydrates and certain active compounds. In conclusion, FTIR spectroscopy could be considered a low-cost alternative to in situ measurements in feed evaluation.     

Method of diet delivery to dairy cows: Effects on nutrient digestion,rumen fermentation,methane emissions from enteric fermentation and stored manure,nitrogen excretion,and milk production

This study was conducted to examine the effect of method of diet delivery to dairy cows on enteric CH₄ emission, milk production, rumen fermentation, nutrient digestion, N excretion, and manure CH₄ production potential. Sixteen lactating cows were used in a crossover design (35-d period) and fed ad libitum twice daily a diet [52:48, forage:concentrate ratio; dry matter (DM) basis] provided as forages and concentrates separately (CF) or as a total mixed ration (TMR). For the CF treatment, concentrates were offered first followed by mixed forages 45 min afterward. Method of diet delivery had no effect on DM intake, but neutral detergent fiber (NDF) intake was greater when the diet was delivered as TMR as compared with CF. Apparent total-tract digestibility of DM, crude protein, and gross energy was slightly (1 percentage unit) lower when the diet was offered as TMR than when offered as CF. In contrast, NDF digestibility was greater when the cows were fed TMR versus CF. Although average daily ruminal pH was not affected by method of diet delivery, daily duration of ruminal pH <5.6 was less when the diet was delivered as TMR as compared with CF (0.9 h/d versus 3.7 h/d). Delivering the diet as TMR increased ruminal total volatile fatty acid and NH₃ concentrations, but had no effect on acetate, propionate, or branched-chain volatile fatty acid molar proportions. Yields of milk, milk fat, or milk protein, and milk production efficiency (kg of milk/kg of DM intake or g of N milk/g of N intake) were not affected by the method of diet delivery. Daily production (g/d), yield (% gross energy intake), and emission intensity (g/kg of energy-corrected milk) of enteric CH₄ averaged 420 g/d, 4.9%, and 9.6 g/kg and were not affected by diet delivery method. Fecal N output was greater when the diet was delivered as TMR versus CF, whereas urinary N excretion (g/d, % N intake) was not affected. Manure volatile solids excretion and maximal CH₄ production potential were not affected by method of diet delivery. Under the conditions of this study, delivering the diet as concentrates and forages separately versus a total mixed ration had no effect on milk production, enteric CH₄ energy losses, urinary N, or maximal manure CH₄ emission potential. However, feeding the diet as total mixed ration compared with feeding concentrates and forages separately attenuated the extent of postprandial decrease in ruminal pH, which has contributed to improving NDF digestibility.     

Supplementation with whole cottonseed causes long-term reduction of methane emissions from lactating dairy cows offered a forage and cereal grain diet

The objective of our work was to supplement a forage and cereal diet of lactating dairy cows with whole cottonseed (WCS) for 12 wk and to determine whether the expected reduction in CH₄ would persist. A secondary objective was to determine the effect of supplementing the diet with WCS on milk yield and rumen function over the 12-wk feeding period. Fifty lactating cows were randomly allocated to 1 of 2 diets (control or WCS). The 2 separate groups were each offered, on average, 4.2 kg of DM/cow per day of alfalfa hay (a.m.) and 6.6 kg of DM/cow per day of ryegrass silage (p.m.) on the ground in bare paddocks each day for 12 wk. Cows in each group were also individually offered dietary supplements for 12 wk in a feed trough at milking times of 5.4 kg of DM/cow per day of cracked wheat grain and 0.5 kg of DM/cow per day of cottonseed meal (control) or 2.8 kg of DM/cow per day of cracked wheat grain and 2.61 kg of DM/cow per day of WCS. The 2 diets were formulated to be similar in their concentrations of CP and ME, but the WCS diet was designed to have a higher fat concentration. Samples of rumen fluid were collected per fistula from the rumen approximately 4 h after grain feeding in the morning. Samples were taken from 8 cows (4 cows/diet) on 2 consecutive days in wk 2 of the covariate and wk 3, 6, 10, and 12 of treatment and analyzed for volatile fatty acids, ammonia-N, methanogens, and protozoa. The reduction in CH₄ emissions (g/d) because of WCS supplementation increased from 13% in wk 3 to 23% in wk 12 of treatment. Similarly, the reduction in CH₄ emissions (g/kg of DMI) increased from 5.1% in wk 3 to 14.5% in wk 12 of treatment. It was calculated that the average reduction in CH₄ emissions over the 12-wk period was 2.9% less CH₄ per 1% added fat, increasing from 1.5% in wk 3 to 4.4% less CH₄ in wk 12. There was no effect of WCS supplementation on rumen ammonia-N, rumen volatile fatty acids, rumen methanogens, and rumen protozoa. On average over the 12-wk period, supplementation with WCS decreased the yield of milk (10%), fat (11%), protein (14%), lactose (11%), and fat plus protein (12%) and BW gain (31%). The WCS supplementation had no effect on milk fat concentration but resulted in a decrease in concentration of protein (5%) and lactose (11%). The major finding from this study is that addition of WCS to the diet of lactating dairy cows resulted in a persistent reduction in CH₄ emissions (g of CH₄/kg of DMI) over a 12-wk period and that these reductions in CH₄ are consistent with previous work that has studied the addition of oilseeds to ruminant diets.     

Diet supplementation with canola meal improves milk production,reduces enteric methane emissions,and shifts nitrogen excretion from urine to feces in dairy cows

The objective of this study was to examine the effect of isonitrogenous substitution of solvent-extracted soybean meal (SBM) with solvent-extracted canola meal (CM) on enteric CH₄ production, ruminal fermentation characteristics (including protozoa), digestion (in situ and apparent total-tract digestibility), N excretion, and milk production of dairy cows. For this purpose, 16 lactating Holstein cows, of which 12 were ruminally cannulated, were used in a replicated 4 × 4 Latin square (35-d periods; 14-d adaptation). The cows averaged (mean ± SD) 116 ± 23 d in milk, 692 ± 60 kg of body weight, and 47.5 ± 4.9 kg/d of milk production. The experimental treatments were control diet (no CM; 0%CM) and diets supplemented [dry matter (DM) basis] with 7.9% CM (8%CM), 15.8% CM (16%CM), or 23.7% CM (24%CM) on a DM basis. The forage:concentrate ratio was 52:48 (DM basis) and was similar among the experimental diets. Canola meal was included in the diet at the expense of SBM and soybean hulls, whereas the percentages of the other diet ingredients were the same. Intake of DM increased linearly, whereas apparent total-tract digestibility of DM, crude protein, neutral detergent fiber, and gross energy (GE) declined linearly as CM inclusion in the diet increased. Total volatile fatty acids concentration and butyrate molar proportion decreased linearly, whereas molar proportion of propionate increased linearly, and that of acetate was unaffected by CM inclusion in the diet. Ruminal ammonia concentration was not affected by inclusion of CM in the diet. Energy-corrected milk (ECM) yield increased linearly (up to 2.2 kg/d) with increasing CM percentage in the diet, whereas milk production efficiency averaged 1.63 kg of ECM/kg of DM intake and was unaffected by CM inclusion in the diet. Daily CH₄ production decreased linearly with increasing CM percentage in the diet (489, 475, 463, and 461 g/d for 0%CM, 8%CM, 16%CM and 24%CM diets, respectively). As a consequence, CH₄ emission intensity (g of CH₄/kg of ECM) also declined linearly by up to 10% as the amount of CM increased in the diet. Methane production also decreased linearly when expressed relative to GE intake (5.7, 5.2, 5.1, and 4.9% for 0%CM, 8%CM, 16%CM and 24%CM diet, respectively). Quantity of manure N excretion was not affected by replacing SBM with CM; however, N excretion shifted from urine to feces as dietary percentage of CM increased, suggesting reduced potential for N volatilization. Results from this study show that replacing SBM with CM as a protein source in dairy cow diets reduced enteric CH₄ emissions (g/d, % of GE intake, and adjusted for milk production) and increased milk production. The study indicates that CM can successfully, partially or fully, replace SBM in lactating dairy cow diets, with positive effects on animal productivity and the environment (i.e., less enteric CH₄ emission and urinary N excreted). We conclude that compared with SBM, inclusion of CM meal in dairy cow diets can play a key role in reducing the environmental footprint of milk production.     

Technical note: Comparison of rectal and vaginal temperatures in lactating dairy cows

A method commonly used to identify illness in dairy cows is measuring body temperatures with a rectal thermometer, but vaginal measures are becoming common in research. The primary objective of this study was to validate vaginal measures of body temperature by comparing them with rectal temperatures. Data loggers used to collect vaginal temperatures can be programmed to collect many readings per day, providing an opportunity to interpret effects of health in relation to diurnal differences in temperatures. Thus, a secondary objective was to compare the diurnal pattern in body temperatures for cows with and without retained placenta (RP). Body temperature was monitored for 8 d in 29 cows that had recently calved (enrolled 2 d after calving; 7 of these cows were diagnosed with RP) and in 13 cows in peak lactation (98 ± 8 d in milk). Rectal temperatures were taken at 0630, 0930, 1230, 1530, 1830, and 2130 h (±30 min) with a digital thermometer for 8 d consecutively. During the same period, vaginal temperatures were measured every 10 min with a microprocessor-controlled data logger attached to a modified vaginal controlled internal drug release insert. Values from the vaginal loggers were averaged over 1 h and paired with the corresponding rectal temperature. There was a relationship between rectal and vaginal temperatures for fresh cows (n = 1,393; r = 0.81) and for peak-lactation cows (n = 556; r = 0.46). Cows with RP had higher body temperatures (39.2 ± 0.01) compared with healthy cows (39.1 ± 0.01). Body temperature was higher at night, and lower between 0800 to 1000 h for healthy cows (39.0 ± 0.02) and between 1100 to 1300 h for RP cows (39.1 ± 0.02). In summary, vaginal temperatures were associated with rectal measures, and provided the advantage of capturing dirurnal changes in body temperature.     

Short communication: Heritability of methane production and genetic correlations with milk yield and body weight in Holstein-Friesian dairy cows

Greenhouse gases originating from the dairy sector, including methane (CH₄), contribute to global warming. A possible strategy to reduce CH₄ production is to use genetic selection. This requires genetic parameters for CH₄ production and correlations with production traits. Data were available on 184 Holstein-Friesian cows. Methane production was measured in the milking robot during milking from December 2009 to April 2010. In total 2,456 observations for CH₄ production were available. Milk yield (MY) and body weight (BW) were obtained at every milking from November 2008 to October 2010. In total 4,567 observations for milk yield and 4,570 observations for BW were available. Restricted maximum likelihood, using random regression models, was used to analyze the data. Heritability (standard error given in parentheses) for CH₄ production ranged from 0.12 (0.16) to 0.45 (0.11), and genetic correlations with MY ranged from 0.49 (0.12) to 0.54 (0.26). The positive genetic correlation between CH₄ production and milk yield indicates that care needs to be taken when genetically selecting for lower CH₄ production, to avoid a decrease in MY at the animal level. However, this study shows that CH₄ production is moderately heritable and therefore progress through genetic selection is possible.     

Persistence of differences between dairy cows categorized as low or high methane emitters,as estimated from milk mid-infrared spectra and measured by GreenFeed

Currently, various attempts are being made to implement breeding schemes aimed at producing low methane (CH₄) emitting cows. We investigated the persistence of differences in CH₄ emission between groups of cows categorized as either low or high emitters over a 5-mo period. Two feeding regimens (pasture vs. indoors) were used. Early- to mid-lactation Holstein Friesian cows were categorized as low or high emitters (n = 10 each) retrospectively, using predictions from milk mid-infrared (MIR) spectra, before the start of the experiment. Data from MIR estimates and from measurements with the GreenFeed (GF; C-Lock Technology Inc., Rapid City, SD) system over the 5-mo experiment were combined into 7-, 14-, and 28-d periods. Feed intake, eating and ruminating behavior, and ruminal fluid traits were determined in two 7-d measurement periods in the grazing season. The CH₄ emission data were analyzed using a split-plot ANOVA, and the repeatability of each of the applied methods for determining CH₄ emission was calculated. Traits other than CH₄ emission were analyzed for differences between low and high emitters using a linear mixed model. The initial category-dependent differences in daily CH₄ production persisted over the subsequent 5 mo and across 2 feeding regimens with both methods. The repeatability analysis indicated that the biweekly milk control scheme, and even a monthly scheme as practiced on farms, might be sufficient for confirming category differences. However, the relationship between CH₄ data estimated by MIR and measured with GF for individual cows was weak (R² = 0.26). The categorization based on CH₄ production also generated differences in CH₄ emission per kilogram of milk; differentiation between cow categories was not persistent based on milk MIR spectra and GF. Compared with the high emitters, low emitters tended to show a lower acetate-to-propionate ratio in ruminal volatile fatty acids, whereas feed intake and ruminating time did not differ. Interestingly, the low emitters spent less time eating than the high emitters. In conclusion, the CH₄ estimation from analyzing the milk MIR spectra is an appropriate proxy to form and regularly control categories of cows with different CH₄ production levels. The categorization was also sufficient to secure similar and persistent differences in emission intensity when estimated by MIR spectra of the milk. Further studies are needed to determine whether MIR data from individual cows are sufficiently accurate for breeding.     

Short communication: early detection of mastitis using infrared thermography in dairy cows

Infrared thermography (IRT) absorbs infrared radiation and generates images based on the amount of heat generated. It has been used in human medicine for diagnosis of various cancers. This experiment was conducted to determine if IRT had merit for early detection of subclinical mastitis in dairy cows. Milk sample and skin surface temperature (SST) were simultaneously evaluated using the California Mastitis Test (CMT) and IRT for each quarter in 94 dairy cows (49 Brown Swiss and 45 Holstein). Average days in milk (DIM) and milk production were 93 ± 37 d and 16 ± 2.2 kg (mean ± SD) and their ages ranged from 4 to 8 yr. There was a strong correlation between SST and CMT score (r = 0.92). Average SST was 33.19, 34.08, 34.99, and 36.15°C for quarters with the CMT score of 0 (n = 156), +1 (n = 116), +2 (n = 80), and +3 (n = 24), respectively. This association was best described by a linear model as follows: y = 0.94x + 33.17, R² = 0.85, where y = SST and x = CMT score. Changes in rectal temperature (RT) due to the CMT score were minor (y = 0.09x + 38.39, R² = 0.07, where y = RT and x = average CMT score). In conclusion, RT may not confirm mastitis. However, IRT is sensitive enough to perceive changes in SST in response to varying degrees of severity of the mammary gland infection as reflected by the CMT score, suggesting that as a noninvasive tool, IRT can be employed for screening dairy cows for mastitis.