Derivation of economic values for German dairy breeds by means of a bio-economic model—with special emphasis on functional traits

To assess the economic importance of breeding traits, economic values (EV) were derived for 3 German dairy cattle breeds: German Holstein (HOL), Angler (ANG), and Red and White Dual-Purpose (RDN). For that purpose, the stochastic bio-economic model SimHerd (SimHerd A/S, Viborg, Denmark) was used, which simulates the expected monetary gain in dairy herds. The EV was calculated as the alteration in average net return of the herd responding to a marginal change in the trait of interest. When deriving EV using SimHerd, economic consequences resulting from changes in the age structure of a dairy herd (i.e., structural herd effects) are considered. However, this requires the simulation of relationships between traits in the bio-economic model. To avoid double counting, the EV of a trait was corrected for effects from alterations in correlated traits using multiple regression analysis. The EV were derived for 23 traits in terms of production, conformation and workability, dairy health, calf survival, and reproduction performance. Furthermore, the relative economic importance of the breeding traits was calculated. Relative emphasis on production was between 39.9 and 44.4% in the breeds studied. Total costs per case of ketosis and metritis ranged from €167 to €196 and €173 to €182, respectively. Highest marginal EV of direct health traits were found for mastitis (€257 to €271 per case) and lameness (€270 to €310 per case). Consequently, relative emphasis on direct health traits was between 15.7 and 17.9%. The EV of reproduction performance showed largest differences among the cattle breeds. Overall relative emphasis on reproduction was 10.5% in HOL, 10.8% in ANG, and 6.5% in RDN. The relative economic importance of cow mortality ranged from 15.5 to 16.0% across the breeds. Collectively, the study showed the high economic importance of functional traits in the cattle breeds studied.     

Oxylipids are associated with higher disease risk in postpartum cows

Postpartum diseases are a major animal welfare and economic concern for dairy producers. Dysregulated inflammation, which may begin as soon as the cessation of lactation, contributes to the development of postpartum diseases. The ability to regulate inflammation and mitigate postpartum health diseases relies, in part, on the production of inflammatory mediators known as oxylipids. The objective of this study was to examine associations between oxylipids and postpartum diseases. Plasma samples were collected from 16 cattle via coccygeal venipuncture at the following time points: 6 d before dry-off; dry-off (d 0); 1, 2, 6, and 12 d after dry-off; 14 ± 3 d before the expected calving date; and 7 ± 2 d after calving. After calving, cows were grouped according to if clinical disease was undetected throughout the sampling period (n = 7) or if they developed a disease postpartum (n = 9). Liquid chromatography-tandem mass spectrometry was used to analyze plasma concentrations of 63 oxylipid species. Of the 32 oxylipids detected, concentrations of 7 differed between cows with no detected disease and diseased cows throughout the sampling period. Thus, a variable oxylipid profile was demonstrated through 2 major physiological transitions of a lactation cycle. Further, the information gained from this pilot study using a small number of animals with diverse diseases from a single herd suggests that it may be possible to use oxylipids at early mammary involution to alert dairy producers of cows at risk for disease after calving. Future studies should be performed in larger populations of animals, including cows from diverse geographies and dairying styles, and focus on specific diseases to evaluate the utility of oxylipids as biomarkers. Furthermore, it is important to determine the clinical implications of variable oxylipid concentrations throughout the lactation cycle and if the oxylipid profile can be modulated to improve inflammatory outcomes.     

Comparison of feed evaluation models on predictions of milk protein yield on Québec commercial dairy farms

Feed evaluation models (FEM) are a core part in dairy cow feeding. As these models are developed using different biological and mathematical approaches mainly tested in a research context, their abilities to predict production in commercial farms need to be validated, even more so when they are used outside the context of their development. Four FEM—National Research Council, 2001 (NRC_2001); Cornell Net Carbohydrate and Protein System, 2015 (CNCPS); NorFor, 2011; and INRA, 2018 (INRA_2018)—were evaluated on their abilities to predict daily milk protein yield (MPY) of 541 cows from 23 dairy herds in the province of Québec, Canada. The effects of cow and diet characteristics were tested on the residuals of MPY. Sensitivity and uncertainty analyses were then performed to evaluate the influence of the uncertainty of the main characteristics of cows and feed ingredients measured on the farm and used in the 4 FEM on the predictions of metabolizable protein (MP) supply and MPY. The 4 models had acceptable predictions of MPY, with concordance correlation coefficients (CCC) ranging from 0.75 to 0.82 and total bias ranging from 12.8% to 19.3% of the observed mean. The Scandinavian model NorFor had the best predictions with a CCC of 0.82, whereas the 3 other models had similar CCC at 0.75 to 0.76. The INRA_2018 and NRC_2001 models presented strong central tendency biases. Removing herd effect put the 4 FEM at the same level of performance, with 11.9 to 12.4% error. Analyzing model behavior within a herd seems to partly negate the effect of using predicted dry matter intake (DMI) in the comparison of models. Diet energy density, days in milk, and MPY estimated breeding value were related to the residual in the 4 models, and Lys and Met (as percent of MP) only in NRC_2001 and NorFor. This suggests that inclusion of these factors in these models would improve MPY predictions. From the sensitivity analysis, for the 4 FEM, DMI and factors affecting its prediction had the greatest influence on the predictions of MP supply and MPY. Of the feed ingredients, forage composition had the greatest effect on these predictions, including a strong effect of legume proportion with NorFor. Diet acid detergent fiber concentration had a very strong effect on MP supply and MPY predictions only in INRA_2018, because of its effect on organic matter digestibility estimation. The range of predictions of MP supply and MPY when combining all these potential uncertainties varied depending on the models. The INRA_2018 model presented the lowest standard deviation (SD) and NorFor the highest SD for the predictions of both MP supply and MPY. Overall, despite the fact that FEM were developed in a research context, their use in a commercial context yields acceptable predictions, with NorFor yielding the best predictions overall, although within-herd responses varied similarly for the 4 tested models.     

Transition cow nutrition and management strategies of dairy herds in the northeastern United States: Part I—Herd description and performance characteristics

Our objective was to describe management and herd characteristics of the transition period on freestall dairy herds in the northeastern United States using an on-farm survey and prospective cohort design. Enrolled herds (n = 72) had a median of 900 milking cows (range: 345–2,900) and a rolling herd average of 12,674 kg (standard deviation ± 1,220 kg), and 87.2% (n = 82/94) of fresh pens were milked at least 3×/d. The prevalence of herds with ≥15% of sampled cows with elevated concentrations of nonesterified fatty acids prepartum (≥0.27 mmol/L, 2–14 d before parturition) and postpartum [primiparous: ≥0.60 mmol/L, multiparous: ≥0.70 mmol/L, 3–14 d in milk (DIM)], β-hydroxybutyrate postpartum (≥1.2 mmol/L, 3–14 DIM), and haptoglobin postpartum (≥1 g/L, 0–12 DIM) was 51%, 51%, 51%, and 57%, respectively. In most herds, cows were moved to a calving pen when showing signs of labor (73.6%; n = 53/72) instead of 0 to 3 d before expected calving (26.4%, n = 19/72). Cows remained in the calving or maternity pen for a median (range) time of 2 (0–24) h after parturition before moving to the next pen. Primiparous cows remained in the first pen moved to after parturition for a longer period than multiparous cows [median (range) days: 12 (1.5–25) vs. 6 (1.5–22)]. Approximately 20% of herds had routine vaccinations administered in the maternity or calving pen, first pen after parturition, or both. Almost all herds (n = 69/72) performed fresh cow health checks; however, only 53% (n = 38/72) locked up all fresh cows daily. More herds housed primiparous and multiparous cows in separate pens during the far-off dry (65.3%; n = 47/72) and high-lactation (81.9%; n = 59/72) periods compared with the close-up dry (31.9%; n = 23/72) and fresh periods (27.8%; n = 20/72). At least half of the pens observed during the far-off dry, close-up dry, and fresh periods had a stocking density <100%. Approximately one-third of pens observed during the far-off dry period had feed pushed up ≤4×/d compared with approximately 15 to 20% of pens observed during the close-up dry, fresh, and high-lactation periods. More than half of the total mixed ration samples acquired from the far-off and close-up dry period visits had greater than the recommended proportion of particles in the 19-mm screen of the Penn State Particle Separator. The results of this observational study illustrated the range of management practices used in freestall herds in this region and lay the groundwork for future hypothesis-driven studies using this sampled population.     

Veterinary herd health management—Experiences and perceptions among Swedish dairy cattle veterinarians

Cattle veterinarians have long been encouraged to take on a role as proactive health consultants. However, the process so far has been slow in Sweden and elsewhere, and only a rather small proportion of cattle work conducted by veterinarians involves veterinary herd health management (VHHM). The aims of this exploratory study were to explore Swedish cattle veterinarians' interpretation of VHHM services and to understand the factors that might affect the extent to which cattle veterinarians perform VHHM. Six focus group discussions with cattle veterinarians complemented with 5 individual telephone interviews with clinic managers were conducted in 2020. In total, 33 cattle veterinarians participated, all employed by the largest employer of Swedish cattle veterinarians: Distriktsveterinärerna (Swedish Board of Agriculture). Participants were chosen from 6 geographical regions with the aim to present variations in gender, age, country of education, proportion of dairy cattle work at the clinic, experience in the veterinary profession, and experience in work with dairy herds and in VHHM. The focus group discussions and interviews were recorded and these recordings were transcribed and analyzed thematically. Participants interpreted VHHM as work associated with the process of advising and included both ad hoc advising and more strategic forms of services. Prebooked visits per se were not seen as VHHM. We identified 4 different themes among the factors affecting the extent of VHHM services: (1) farmer trust and demand; (2) veterinary competence; (3) time available for VHHM; and (4) the individual veterinarian's commitment and motivation. To gain farmers' trust and to create a demand for VHHM services, the results of VHHM work and the veterinarian's competence were deemed central by the participants. The veterinarians' skills in communication and relation building were considered especially important. Some farmers were perceived as having little interest in, or lacking deeper knowledge about, VHHM services. The promotion of VHHM services was mentioned as an important factor to increase farmer demand. Participants described VHHM as work demanding high skills and continuous capacity development. Veterinarians' personal commitment and motivation were also described as important for the extent to which VHHM services were performed. This was in turn affected by the psychosocial work environment (e.g., workload, interest and recognition from farmers and managers, and acceptance, priority, and support by colleagues and managers). Clinic managers had a central role in the extent to which VHHM services are offered by an individual veterinarian due to their responsibility for staff scheduling, which highly affects the conditions for capacity development, intercollegiate networking, and cooperation. Lack of time was a major barrier for VHHM. On-call duty time and subsequent compensatory leave affected the total time available, and participants described time conflicts between VHHM and emergency services; moreover, it was perceived as challenging to find sufficient time for capacity development in several different species for veterinarians working in mixed practice. The slow development toward more proactive approaches for cattle veterinarians can be explained by the numerous different factors that together constrain the veterinarian to the traditional role of diagnosing and treating sick animals.     

Incidence,clinical patterns,and risk factors of postpartum uterine diseases in dairy cows from high-altitude tropical herds

The cow's uterus sustains bacterial contamination and active inflammation after calving as part of the normal physiological process of uterine involution. Although the definition, incidence, and risk factors for postpartum uterine diseases (PUD) have been documented in annual calving systems with high-producing cows on total mixed ration, the literature contains little information for other production systems. The objective of this study was to quantify the incidence risk and factors associated with metritis, clinical endometritis, and cytological endometritis in high-altitude tropical dairy herds in a pasture-based system. A total of 248 cows from 5 commercial dairy herds in northern Antioquia, Colombia, were enrolled in this prospective observational longitudinal cohort study. Data collection and PUD diagnosis were performed at d 0, 3, 10, 17, 24, 31, 38, 45, and 52 (±1) after parturition. Between 60 and 70 d, cows were systematically enrolled in a synchronization protocol, and herds were visited monthly for pregnancy diagnosis until 180 ±15 d. The multivariable logistic regression model of variables associated with PUD occurrence included (a) parity, season of calving, transition diet, and body condition score at calving; (b) blood calcium, phosphorus, and magnesium concentrations, and milk urea nitrogen, β-hydroxybutyrate and fat-to-protein ratio; and (c) dystocia, retained placenta, and delayed uterine involution. The incidences of puerperal metritis, clinical metritis (MET), clinical endometritis (CE), and cytological endometritis (CYTO) were 2.8, 25, 29, and 26%, respectively. Retained placenta and dystocia were associated with MET, and MET was associated with CE. Low blood calcium concentration at calving was associated with CYTO. Overall, 51.2% of the cows suffered at least 1 category of PUD during the first 60 d postpartum (DPP). However, cows also suffered from different consecutive clinical events of PUD (MET, CE, and CYTO) during the follow-up period (0 to 180 ±15 DPP). These events could be grouped into 4 types (which were referred to as “clinical patterns”) based on interactions between MET, CE, and CYTO.     

Short communication: Iodine content in bovine milk is lowly heritable and shows limited genetic variation

Milk and dairy products are considered important sources of iodine in several countries. Despite this, there is a paucity of studies that have investigated sources of variation of milk iodine, especially on a large scale. So far, it is not clear if milk iodine content could be increased through breeding in dairy cattle. Recently, a mid-infrared spectroscopy prediction model has been developed for an indirect quantification of iodine content in cow milk, as it is a faster and less expensive method that allows the prediction at population level. The model has coefficient of determination and ratio of performance to deviation in external validation of 0.57 and 1.44, respectively, and it was used in the present study to predict the iodine content from historical milk spectral data to investigate phenotypic and genetic aspects in the Italian Holstein cattle. Based on the accuracy of the model, the prediction was interpreted as proxy for the real milk iodine concentration (IOD_P). The data set comprised 33,776 test-day records with IOD_P from 4,072 cows. Data of IOD_P were transformed through natural logarithm to achieve a normal distribution. The effect of parity, lactation stage, and month of sampling were investigated, and genetic parameters were estimated using a test-day repeatability animal model. Milk IOD_P decreased with parities and was the lowest in early lactation. Heritability of IOD_P was low (0.025) and it was positively genetically correlated with milk yield and negatively with fat content. Results suggested that it would be challenging to directly improve this trait through breeding strategies in dairy cattle, because IOD_P is mainly affected by temporary environmental factors and thus, cannot be easily improved through genetics. Although preliminary, findings of this study suggest that it would be more convenient to develop feeding and management strategies to drive milk iodine level than to put efforts and resources into breeding strategies. Further studies should validate IOD_P as an indicator trait of milk iodine content by improving reference data and estimating genetic correlation between predicted and measured values.     

The effects of supplementation with a blend of cinnamaldehyde and eugenol on feed intake and milk production of dairy cows

Plant extracts (PE) are naturally occurring chemicals in plants, and many of these molecules have been reported to influence production efficiency of dairy and beef animals. Two experiments were conducted to determine the effect of a PE additive (CE; an encapsulated blend of cinnamaldehyde and eugenol) on the milk production performance of lactating dairy cows across a range of doses. In experiment 1, 32 Holstein multi- and primiparous dairy cows in mid-lactation were assigned to no additive or supplementation with CE (350 mg/d; n = 16 cows/treatment) for 6 wk. In experiment 2, 48 Holstein multi- and primiparous dairy cows were assigned to no additive or supplementation with CE (200, 400, or 600 mg/d; n = 12 animals/treatment) for 8 wk. A 1-wk covariate period was included in both experiments. In both experiments, individual dry matter intake (DMI), milk production, milk composition, and somatic cell count were recorded daily. In experiment 1, CE was associated with an increase in DMI in both parity groups but an increase in milk production of multiparous cows only. In experiment 2, milk yield of multiparous cows was decreased at the 2 highest doses, whereas milk yield of primiparous cows was increased at the low and high doses of CE. These responses were accompanied by similar changes in DMI; therefore, CE did not affect feed efficiency. We observed no effect of CE on SCC or milk composition; however, treatment by parity interactions were detected for each of these variables that have not been described previously. Based on the results of these experiments, we conclude that a blend of cinnamaldehyde and eugenol can increase DMI and milk production in lactating dairy cows. In addition, environmental factors appear to influence the response to CE, including dose and parity, and these should be explored further.     

A dose-response evaluation of rumen-protected niacin in thermoneutral or heat-stressed lactating Holstein cows

Twenty-four multiparous high-producing dairy cows (40.0 ± 1.4 kg/d) were used in a factorial design to evaluate effects of 2 environments [thermoneutral (TN) and heat stress (HS)] and a dose range of dietary rumen-protected niacin (RPN; 0, 4, 8, or 12 g/d) on body temperature, sweating rate, feed intake, water intake, production parameters, and blood niacin concentrations. Temperature–humidity index values during TN never exceeded 68 (stress threshold), whereas temperature–humidity index values during HS were above 68 for 24 h/d. The HS environment increased hair coat and skin, rectal, and vaginal temperatures; respiration rate; skin and hair coat evaporative heat loss; and water intake and decreased DMI (3.5 kg/d), milk yield (4.1 kg/d), 4% fat-corrected milk (2.7 kg/d), and milk protein yield (181.7 g/d). Sweating rate increased during HS (12.7 g/m² per h) compared with TN, but this increase was only 10% of that reported in summer-acclimated cattle. Niacin supplementation did not affect sweating rate, dry-matter intake, or milk yield in either environment. Rumen-protected niacin increased plasma and milk niacin concentrations in a linear manner. Heat stress reduced niacin concentration in whole blood (7.86 vs. 6.89 μg/mL) but not in milk. Reduced blood niacin concentration was partially corrected by dietary RPN. An interaction existed between dietary RPN and environment; dietary RPN linearly increased water intake in both environments, but the increase was greater during HS conditions. Increasing dietary RPN did not influence skin temperatures. During TN, supplementing 12 g/d of RPN increased hair coat (unshaved skin; 30.3 vs. 31.3°C at 1600 h) but not shaved skin (32.8 vs. 32.9°C at 1600 h) temperature when compared with 0 g/d at all time points, whereas the maximum temperature (18°C) of the room was lower than skin temperature. These data suggest that dietary RPN increased water intake during both TN and HS and hair coat temperature during TN; however, core body temperature was unaffected. Thus, encapsulated niacin did not improve thermotolerance of winter-acclimated lactating dairy cows exposed to moderate thermal stress in Arizona.     

Bivariate threshold models for genetic evaluation of susceptibility to and ability to recover from mastitis in Danish Holstein cows

Mastitis in dairy cows is an unavoidable problem and genetic variation in recovery from mastitis, in addition to susceptibility, is therefore of interest. Genetic parameters for susceptibility to and recovery from mastitis were estimated for Danish Holstein-Friesian cows using data from automatic milking systems equipped with online somatic cell count measuring units. The somatic cell count measurements were converted to elevated mastitis risk, a continuous variable [on a (0–1) scale] indicating the risk of mastitis. Risk values >0.6 were assumed to indicate that a cow had mastitis. For each cow and lactation, the sequence of health states (mastitic or healthy) was converted to a weekly transition: 0 if the cow stayed within the same state and 1 if the cow changed state. The result was 2 series of transitions: one for healthy to diseased (HD, to model mastitis susceptibility) and the other for diseased to healthy (DH, to model recovery ability). The 2 series of transitions were analyzed with bivariate threshold models, including several systematic effects and a function of time. The model included effects of herd, parity, herd-test-week, permanent environment (to account for the repetitive nature of transition records from a cow) plus two time-varying effects (lactation stage and time within episode). In early lactation, there was an increased risk of getting mastitis but the risk remained stable afterwards. Mean recovery rate was 45% per lactation. Heritabilities were 0.07 [posterior mean of standard deviations (PSD) = 0.03] for HD and 0.08 (PSD = 0.03) for DH. The genetic correlation between HD and DH has a posterior mean of ?0.83 (PSD = 0.13). Although susceptibility and recovery from mastitis are strongly negatively correlated, recovery can be considered as a new trait for selection.