Is rumination time an indicator of methane production in dairy cows?

As long as large-scale recording of expensive-to-measure and labor-consuming traits, such as dry matter intake (DMI) and CH4 production (CH4P), continues to be challenging in practical conditions, alternative traits that are already routinely recorded in dairy herds should be investigated. An ideal indicator trait must, in addition to expressing genetic variation, have a strong correlation with the trait of interest. Our aim was to estimate individual level and phenotypic correlations between rumination time (RT), CH4P, and DMI to determine if RT could be used as an indicator trait for CH4P and DMI. Data from 343 Danish Holstein cows were collected at the Danish Cattle Research Centre for a period of approximately 3 yr. The data set consisted of 14,890 records for DMI, 15,835 for RT, and 6,693 for CH4P. Data were divided in primiparous cows only (PC) and all cows (MC), and then divided in lactation stage (early, mid, late, and whole lactation) to analyze the changes over lactation. Linear mixed models, including an animal effect but no pedigree, were used to estimate the correlations among traits. Phenotypic and individual level correlations between RT and both CH4P and DMI were close to zero, regardless of lactation stage and data set (PC or MC). However, CH4P and DMI were highly correlated, both across lactation stages and data sets. In conclusion, RT is unsuitable to be used as an indicator trait for either CH4P or DMI. Our study failed to validate RT as a useful indicator trait for both CH4P and DMI, but more studies with novel phenotypes can offer different approaches to select and incorporate important yet difficult to record traits into breeding goals and selection indexes.

Genetic parameters of rumination time and feed efficiency traits in primiparous Holstein cows under research and commercial conditions.

Feed efficiency has the potential to be improved both through feeding, management, and breeding. Including feed efficiency in a selection index is limited by the fact that dry matter intake (DMI) recording is only feasible under research facilities, resulting in small data sets and, consequently, uncertain genetic parameter estimates. As a result, the need to record DMI indicator traits on a larger scale exists. Rumination time (RT), which is already recorded in commercial dairy herds by a sensor-based system, has been suggested as a potential DMI indicator. However, RT can only be a DMI indicator if it is heritable, correlates with DMI, and if the genetic parameters of RT in commercial herd settings are similar to those in research facilities. Therefore, the objective of our study was to estimate genetic parameters for RT and the related traits of DMI in primiparous Holstein cows, and to compare genetic parameters of rumination data between a research herd and 72 commercial herds. The estimated heritability values were all moderate for DMI (0.32-0.49), residual feed intake (0.23-0.36), energy-corrected milk (ECM) yield (0.49-0.70), and RT (0.14-0.44) found in the research herd. The estimated heritability values for ECM were lower for the commercial herds (0.08-0.35) than that for the research herd. The estimated heritability values for RT were similar for the 2 herd types (0.28-0.32). For the research herd, we found negative individual level correlations between RT and DMI (-0.24 to -0.09) and between RT and RFI (-0.34 to -0.03), and we found both positive and negative correlations between RT and ECM (-0.08 to 0.09). For the commercial herds, genetic correlations between RT and ECM were both positive and negative (-0.27 to 0.10). In conclusion, RT was not found to be a suitable indicator trait for feed intake and only a weak indicator of feed efficiency.

Variations in automatically recorded rumination time as explained by variations in intake of dietary fractions and milk production, and between-cow variation.

Individual recording of rumination time (RT) is now possible in commercial dairy herds, through development of a microphone-based sensor, which is able to record RT by the sound of rumination activity. The objectives of this study were to examine the relationship between daily RT and intakes of different dietary fractions, the relationship between RT in minutes per kilogram of dry matter intake (DMI) and milk production, and to examine the variation in RT within and between mid-lactating dairy cows. Data from 3 production trials were used in which a total of 27 different diets were fed. The data contained 761, 290, and 203 daily recordings of RT, milk yield, milk components, DMI, and intake of dietary fractions recorded on 29, 26, and 24 Holstein and Swedish Red cows from trials 1, 2, and 3, respectively. The dietary fractions included forage neutral detergent fiber (NDF), concentrate NDF, crude protein, sugar, starch, and the remaining fraction represented by organic matter--(forage NDF+concentrate NDF+crude protein+sugar+starch). The relationship between the dietary fractions and RT was analyzed in 2 steps. In step 1, the dietary fractions, which were significantly related to RT, were selected and simultaneously checked for multicollinearity between the dietary components; in step 2, a multivariate model, including the effect of repeated measurements, the main effect of the selected dietary fractions from step 1, random effects of cow(trial) and trial, and information on breed, days in milk, and parity was used to analyze the relationship between RT and the selected dietary fractions. Relationships between RT in minutes per kilogram of DMI and milk yield and milk components were analyzed, using the same multivariate model as in step 2. Approximately 32% of the variation in daily RT could be explained by variations in intakes of the dietary fractions, whereas 48% of the total variation in RT was accounted for by individual variations between cows. Intakes of forage NDF and starch were positively related to daily RT, whereas intakes of sugar and the remaining fraction were negatively related to daily RT. Rumination time in minutes per kilogram of DMI was negatively related to milk yield and protein percentage, but positively related to milk fat percentage.

Evaluation of physical structure value in spring-harvested grass/clover silage and hay fed to heifers.

The physical structure value of conserved grass/clover forages of spring harvest was evaluated by assessing effects of harvest time, conservation method, iNDF/NDF ratio and NDF intake (NDFI) per kg BW on chewing activity and fecal particle size in dairy heifers. A mixed sward consisting of ryegrass (Lolium perenne), red clover (Trifolium pratense) and white clover (Trifolium repens) was harvested in 2009 on May 9 (early) and 25 (late), and both cuts were conserved as silage and hay. The early silage, early hay, late silage and late hay contained dry matter (DM) of 454, 842, 250 and 828 g/kg, and NDF of 315, 436, 414 and 503 g/kg DM, respectively. Forages were fed as sole feed to four Jersey heifers of 435±30 kg BW in a 4×4 Latin square experiment. Feeding level was 90% of individual ad libitum intake, divided equally across two daily meals offered at 0800 and 1530 h. Chewing activity was estimated from recorded jaw movements (JM) oscillations continuously logged for 96 h and summarized per 24 h as mean effective rumination time and eating time. Eating behavior was further observed during four 20-min test meals. Weight proportion of large feces particles (>1.0 mm) and geometric mean fecal particle size (GPS) were calculated. Potentially indigestible NDF (iNDF) was estimated by incubation for 288 h in situ. The daily DM intake (DMI) decreased with progressing maturity at harvest (P<0.001) while daily NDFI was unaffected by harvest time (P>0.05). Earlier harvest led to less rumination per kg NDFI (P<0.01), similar eating time per kg NDFI (P>0.05) and similar proportion of large particles (P>0.01) compared with later harvest. Rumination time per kg NDFI decreased with higher NDFI per kg BW (P<0.001) and with lower iNDF/NDF ratio (P<0.01). Content and potential digestibility of NDF was greater in hay than in silage from the same harvest probably due to field loss and therefore confounded effects of conservation method. This study of high digestibility grass/clover silage and hay showed that NDF content and NDFI per kg BW affect fecal particle size and rumination time per kg NDF, and suggests implementation of NDFI per kg BW in systems evaluating physical structure in diets.

Recording rumination time by a rumination monitoring system in Jersey heifers fed grass/clover silage and hay at three feeding levels.

This study was conducted with the objective to validate a rumination monitoring system (RMS). The RMS was developed by SCR Engineers Ltd. (Netanya, Israel) to record individual rumination times in commercial dairy herds. Four heifers were fed 4 forage types at 3 feeding levels in 4 periods in a Latin square design. The forage types were spring growth of grass/clover harvested early (May 9) and late (May 25) conserved as silage and hay, creating 4 forage types: early harvest silage (ES), early harvest hay (EH), late harvest silage (LS), and late harvest hay (LH). Feeding levels were ad libitum, 90% of ad libitum, and 60% of ad libitum. Data were collected for 24 h at ad libitum feeding level, for 96 h at 90% of ad libitum, and for 24 h at 60% of ad libitum. Rumination time was recorded by the RMS in minutes per 2-h interval (RT(RMS2_i)) and per 24-h interval (RT(RMS24)). As a reference method, rumination time was recorded by chewing halters identifying rumination time by jaw movements (JM) and was accumulated into minutes per 2-h interval (RT(JM2_i)) and per 24-h interval (RT(JM24)) over the same time intervals as RT(RMS2_i) and RT(RMS24). Differences between RT(RMS2_i) and RT(JM2_i) were observed for EH, LS, and LH, with differences of 3.4 (P < 0.001), 1.1 (P = 0.03), and 3.3 (P < 0.001) min per 2-h interval. In addition, feeding restrictively at 90% and 60% of ad libitum resulted in greater rumination time recorded by the RMS compared to JM, with differences of 2.6 min per 2-h interval (P < 0.001) for 90% of ad libitum and 1.6 min per 2-h interval (P = 0.01) for 60% of ad libitum. Further, the differences between rumination times recorded by the RMS compared to JM were different among the 4 heifers. Despite these effects, rumination time recorded by the RMS correlated well with rumination time recorded by JM with correlation between RT(RMS2_i) and RT(JM2_i) of r = 0.91 (P < 0.001) and between RT(RMS24) and RT(JM24) of r = 0.79 (P < 0.001).