Invited review: Beef-on-dairy—The generation of crossbred beef × dairy cattle

peer-reviewedBecause a growing proportion of the beef output in many countries originates from dairy herds, the most critical decisions about the genetic merit of most carcasses harvested are being made by dairy producers. Interest in the generation of more valuable calves from dairy females is intensifying, and the most likely vehicle is the use of appropriately selected beef bulls for mating to the dairy females. This is especially true given the growing potential to undertake more beef × dairy matings as herd metrics improve (e.g., reproductive performance) and technological advances are more widely adopted (e.g., sexed semen). Clear breed differences (among beef breeds but also compared with dairy breeds) exist for a whole plethora of performance traits, but considerable within-breed variability has also been demonstrated. Although such variability has implications for the choice of bull to mate to dairy females, the fact that dairy females themselves exhibit such genetic variability implies that “one size fits all” may not be appropriate for bull selection. Although differences in a whole series of key performance indicators have been documented between beef and beef-on-dairy animals, of particular note is the reported lower environmental hoofprint associated with beef-on-dairy production systems if the environmental overhead of the mature cow is attributed to the milk she eventually produces. Despite the known contribution of beef (i.e., both surplus calves and cull cows) to the overall gross output of most dairy herds globally, and the fact that each dairy female contributes half her genetic merit to her progeny, proxies for meat yield (i.e., veal or beef) are not directly considered in the vast majority of dairy cow breeding objectives. Breeding objectives to identify beef bulls suitable for dairy production systems are now being developed and validated, demonstrating the financial benefit of using such breeding objectives over and above a focus on dairy bulls or easy-calving, short-gestation beef bulls. When this approach is complemented by management-based decision-support tools, considerable potential exists to improve the profitability and sustainability of modern dairy production systems by exploiting beef-on-dairy breeding strategies using the most appropriate beef bulls

Using fatty acid contents in milk to improve fertility of dairy cows?

Improving dairy cow fertility by means of genetic selection has become increasingly important over the last years in order to overcome the declining cow fertility. This study investigated whether the fatty acids profile in milk could be used as an early predictor of genetic merit for fertility. Genetic covariances among 17 fatty acid contents in milk and the number of days from calving to conception were estimated from 29,792 first-parity Holstein cows. Results substantiated the unfavorable relationship among fertility and body fat mobilization in early lactation. Also, about 75% of the genetic variability of fertility was explained by the variability in milk fatty acids profile over the lactation indicating that these traits could be used to supplement genetic evaluations for fertility

Short communication: The beef merit of the sire mated to a dairy female affects her subsequent performance

peer-reviewedMuch of the research to date on dairy × beef matings has focused only on the greater revenue attainable from these beef-cross calves. The objective of the present study was to quantify the mean effect on cow performance following the birth of calves differing in beef merit; all calves were born without calving assistance. Beef merit in the present study was based on the breed of the sire but also its genetic merit for carcass weight and conformation. The cross-sectional study used up to 346,765 calving events from 230,255 Holstein-Friesian cows in 3,604 herds. Performance traits of interest were those associated with milk production, including somatic cell count, as well as female reproductive performance. Sire breed was associated with all yield traits, somatic cell count, and both pregnancy rate and the interval from calving to first service; no association existed with either submission rate or number of services. Relative to a Holstein-Friesian sire, the mean 305-d milk yield (in kg) was 45.22 (standard error, SE = 4.0), 62.0 (SE = 36.8), 65.4 (SE = 9.6), 101.1 (SE = 31.6), 36.7 (SE = 4.9), 51.5 (SE = 10.7), 53.3 (SE = 31.5), and 43.3 (SE = 23.4) less for cows that gave birth to Angus-, Aubrac-, Beligan Blue-, Charolais-, Hereford-, Limousin-, Saler-, or Simmental-sired calves, respectively. Service sire accounted for only 1% of the phenotypic variation in all 3 milk production traits when fitted as a random effect in the model. The regression coefficients of phenotypic milk, fat, and protein yields on sire (of calf) predicted transmitting ability for carcass weight were −1.84 (SE = 0.17), −0.10 (SE = 0.01), and −0.08 kg (SE = 0.01), respectively. The respective regression coefficients on sire (of calf) predicted transmitting ability for carcass conformation (scale of 1 to 15; 1 = poor and 15 = excellent) were −23.46 (SE = 1.81), −1.20 (SE = 0.08), and −1.05 units (SE = 0.06). The biological significance of the sire breed effects or the measure of sire genetic merit on the reproductive traits was either not different from zero or biologically small. Although statistically significant associations existed between sire beef merit and both milk and reproductive performance of the mate, the actual size of the associations was biologically small

The potential of Fourier transform infrared spectroscopy of milk samples to predict energy intake and efficiency in dairy cows

peer-reviewedKnowledge of animal-level and herd-level energy intake, energy balance, and feed efficiency affect day-to-day herd management strategies; information on these traits at an individual animal level is also useful in animal breeding programs. A paucity of data (especially at the individual cow level), of feed intake in particular, hinders the inclusion of such attributes in herd management decision-support tools and breeding programs. Dairy producers have access to an individual cow milk sample at least once daily during lactation, and consequently any low-cost phenotyping strategy should consider exploiting measureable properties in this biological sample, reflecting the physiological status and performance of the cow. Infrared spectroscopy is the study of the interaction of an electromagnetic wave with matter and it is used globally to predict milk quality parameters on routinely acquired individual cow milk samples and bulk tank samples. Thus, exploiting infrared spectroscopy in next-generation phenotyping will ensure potentially rapid application globally with a negligible additional implementation cost as the infrastructure already exists. Fourier-transform infrared spectroscopy (FTIRS) analysis is already used to predict milk fat and protein concentrations, the ratio of which has been proposed as an indicator of energy balance. Milk FTIRS is also able to predict the concentration of various fatty acids in milk, the composition of which is known to change when body tissue is mobilized; that is, when the cow is in negative energy balance. Energy balance is mathematically very similar to residual energy intake (REI), a suggested measure of feed efficiency. Therefore, the prediction of energy intake, energy balance, and feed efficiency (i.e., REI) from milk FTIRS seems logical. In fact, the accuracy of predicting (i.e., correlation between predicted and actual values; root mean square error in parentheses) energy intake, energy balance, and REI from milk FTIRS in dairy cows was 0.88 (20.0 MJ), 0.78 (18.6 MJ), and 0.63 (22.0 MJ), respectively, based on cross-validation. These studies, however, are limited to results from one research group based on data from 2 contrasting production systems in the United Kingdom and Ireland and would need to be replicated, especially in a range of production systems because the prediction equations are not accurate when the variability used in validation is not represented in the calibration data set. Heritable genetic variation exists for all predicted traits. Phenotypic differences in energy intake also exists among animals stratified based on genetic merit for energy intake predicted from milk FTIRS, substantiating the usefulness of such FTIR-predicted phenotypes not only for day-to-day herd management, but also as part of a breeding strategy to improve cow performance.the Irish Department of Agriculture, Food and the Marin

Short communication: Differences in genetic merit for visually-assessed body condition score materialises as phenotypic differences in tactile-based body condition score in commercial dairy cows

peer-reviewedBody condition score (BCS) is a known risk factor for cow health and well-being. Many different BCS scales and systems for assessment exist;while the scales used for assessing BCS vary, differences in how BCS is assessed (i.e., visual versus visual plus tactile) and the extent of training and experience of the assessor (i.e., professional linear classifiers versus producers) also contributes to the underlying variability. Registered dairy cows globally are routinely assessed for linear type traits which describe biological extremes in the morphological attributes; BCS and a correlated trait angularity are within this suite of traits assessed. These linear-type data are used to generate estimates of genetic merit (predicted transmitting ability), but how these estimates manifest themselves as phenotypic differences when assessed by producers on commercial multiparous cows has never been quantified. To evaluate this, 58440 phenotypic BCS records from 48823 lactations in 38608 cows were used. Associations were undertaken using linear mixed models relating phenotypic BCS to genetic merit after accounting for nuisance factors. Differences in genetic merit for either BCS or angularity (assessed visually by professionals on a 1 to 9 scale just once during lactation in primiparous registered cows) translated to phenotypic difference in BCS (assessed by producers using both tactile and visual assessment on a 1 to 5 scale across lactation in commercial dairy cows). The partial correlation between test phenotypic BCS and genetic merit for either BCS or angularity was 0.13 and 0.10, respectively. Based on the model coefficients estimated in the present study, the mean expected difference in phenotypic BCS on a 1 to 5 scale between the top and bottom 10% on genetic merit for BCS or angularity was 0.28 and 0.31 units, respectively. Results from the present study clearly provide confidence that genetic merit for BCS or angularity based on a single visual assessment in primiparous cows is useful to breed for cows of better body condition, irrespective of stage of lactation or parity

Short communication: Animal-level factors associated with whether a dairy female is mated to a dairy or beef bull

peer-reviewedWhen serving a female, the producer must decide whether to mate her to a dairy or beef bull. Tools assisting in this decision could be a useful component of the decision process. A database of 2,283,100 artificial inseminations from 806,725 dairy females was used to investigate what factors were associated with servicing a given female to a beef bull. The probability of being inseminated with a beef bull increased with each service and as the breeding season progressed. An older cow had greater odds of being served with a beef bull, as did cows that calved later in the year, had recently experienced dystocia, were a longer time calved, or were of a poor overall genetic merit compared with herdmates. Cows with low somatic cell count in the previous lactation compared with herdmates were less likely to be mated to a beef bull, as were cows that yielded relatively higher milk solids in the previous lactation. Relative to a first-parity cow, the odds of a fifth-parity cow being mated to a beef bull were 1.35, whereas those of a tenth-parity cow were 2.11. The odds of a female in the worst 10% for total genetic merit being mated to a beef bull were 2.90 times those of a female in the top 10%. Although dystocia was associated with the likelihood of being mated to a beef bull, the actual likelihood did not vary much by level of dystocia experienced. Relative to the first service, the odds of the third and fifth services being to a beef bull were 2.23 and 3.71, respectively. These probability estimates can form the back-end system supporting decisions on mating type for a female within a sire mating advice system but also in risk analysis of farm management

The use of mid-infrared spectrometry to predict body energy status of Holstein cows

Energy balance, especially in early lactation, is known to be associated with subsequent health and fertility in dairy cows. However, its inclusion in routine management decisions or breeding programs is hindered by the lack of quick, easy, and inexpensive measures of energy balance. The objective of this study was to evaluate the potential of mid-infrared (MIR) analysis of milk, routinely available from all milk samples taken as part of large-scale milk recording and milk payment operations, to predict body energy status and related traits in lactating dairy cows. The body energy status traits investigated included energy balance and body energy content. The related traits of body condition score and energy intake were also considered. Measurements on these traits along with milk MIR spectral data were available on 17 different test days from 268 cows (418 lactations) and were used to develop the prediction equations using partial least squares regression. Predictions were externally validated on different independent subsets of the data and the results averaged. The average accuracy of predicting body energy status from MIR spectral data was as high as 75% when energy balance was measured across lactation. These predictions of body energy status were considerably more accurate than predictions obtained from the sometimes proposed fat-to-protein ratio in milk. It is not known whether the prediction generated from MIR data are a better reflection of the true (unknown) energy status than the actual energy status measures used in this study. However, results indicate that the approach described may be a viable method of predicting individual cow energy status for a large scale of application

Linear type trait genetic trends in Irish Holstein-Friesian dairy animals

peer-reviewedThe objective of the present study was to investigate the genetic trends of 18 subjectively scored linear type traits describing animal morphology, as well as udder, teat, feet and leg conformation. The analysis was undertaken using 2,932,700 Holstein-Friesian females born in the Republic of Ireland between the years 2000 and 2020, inclusive. The results indicate that Holstein-Friesian females have progressively become shorter in stature as well as shallower (i.e. body depth) and less angular. The reduction in genetic merit for stature score since the year 2004 was, however, only observed in non-herdbook-registered heifers. Furthermore, the reducing score in body depth (i.e. narrower) and angularity (i.e. less angular) was approximately twice as fast in non-herdbook-registered heifers as it was in herdbook-registered heifers. Differences in the genetic merit of the body-related traits for calves born versus those that became cows only existed prior to 2010 with little biological differences thereafter; this observation was common across most of the linear type traits. Genetic merit for locomotion in non-herdbook-registered animals has deteriorated over the 20-yr period, while the foot angle over that period is becoming lower; no such trends were observed for the herdbook-registered animals. Large differences not only in the trends themselves, but also in the mean genetic merit for udder traits existed when comparing herdbook-registered calves versus non-registered calves. In conclusion, genetic merit for many of the traits evaluated has trended relatively consistent in a given direction, albeit the cumulative change in genetic s.d. units per traits over the 20-yr period was very small