About

Lars Hansen is a Professor in the Department of Earth & Environmental Sciences at the University of Minnesota Twin Cities. His research focuses on how rocks behave at extreme conditions, particularly their rheological behavior at high temperatures and pressures. Hansen's group primarily uses laboratory-based experiments to investigate the mechanisms of rock deformation at the atomic scale and how these mechanisms influence the dynamics of the solid Earth at the scale of tectonic plates. His work involves studying the generation, evolution, and interaction of lattice dislocations during the plastic deformation of rocks across a wide range of temperatures, time scales, and spatial scales. His research emphasizes the role of crystal defects, grain boundaries, and microstructural evolution in controlling the mechanical strength and viscosity of rocks. Hansen's studies extend to understanding how these defects influence large-scale processes such as seismic anisotropy in the upper mantle, the viscosity and microstructural evolution of Earth's deep interior, and the yield strength of the lithosphere. His laboratory experiments include high-resolution and high-temperature creep, high-pressure creep, and low-temperature plasticity, complemented by microscopy analysis to develop a comprehensive understanding of rock deformation physics. Hansen's work also involves examining naturally deformed rocks to validate hypotheses derived from laboratory experiments, contributing to our understanding of geodynamic processes and Earth's interior behavior.

Research topics

• Biology
• Veterinary medicine
• Animal science
• Medicine
• Biotechnology
• Genetics

Selected publications

• Lactation curves of Montbéliarde-sired and Viking Red-sired crossbred cows and their Holstein herdmates in commercial dairies

  Journal of Dairy Science · 2024-01-21 · 4 citations

  articleOpen access

  Lactation curves were estimated for Montbéliarde (MO) × Holstein (HO) and Viking Red (VR) × HO 2-breed crossbred cows and for MO × VR/HO and VR × MO/HO 3-breed crossbred cows and their HO herdmates from test-day observations in 7 high-performance herds that participated in a designed study. Cows calved from 2010 to 2017. Test-day observations from milk recording were used to fit the lactation curves of cows in their first 3 lactations. Lactations of cows were required to have at least 250 DIM and to have at least 6 test days ≤265 DIM. Lactation curves from random regression (RR) were compared for 305-d production (kg), peak production (kg), peak day of production, and production from 4 to 103 DIM (kg), from 104 to 205 DIM (kg), and from 206 to 305 DIM (kg) for milk, fat, and protein. Also, the persistency of production was compared. First-lactation versus second- and third-lactation cows were analyzed separately for both the 2-breed and 3-breed crossbred cows and their respective HO herdmates. Legendre polynomial RR had the best goodness of fit for the lactation curves compared with Ali-Schaeffer and Wilmink RR from the test-day observations of milk, fat, and protein production. For fluid milk production of first-lactation cows, the MO × HO 2-breed crossbreds were not different from their HO herdmates for any of the lactation-curve characteristics, except persistency. However, the VR × HO 2-breed crossbreds had less fluid milk production compared with their HO herdmates. For first lactation, the MO × HO 2-breed crossbreds had more persistency of milk, fat, and protein production compared with their HO herdmates. The first-lactation MO × VR/HO 3-breed crossbreds had more persistency of fluid milk production compared with their HO herdmates. For second and third lactations, both the MO × HO and the VR × HO 2-breed crossbreds had higher fat production compared with their HO herdmates. Furthermore, the MO × HO 2-breed crossbreds had more protein production (kg) in all 3 periods of lactation compared with their HO herdmates. Crossbred cows may have advantages over HO cows for persistency of production in high-performance herds.

  PublisherOA PDFDOI

• Genetic selection for reduced health treatment costs in Holstein cows: implications from a long-term study

  Frontiers in Genetics · 2023-09-22 · 1 citations

  articleOpen access

  The objective of this study was to estimate genetic parameters of health treatment cost of Holstein cows from producer-recorded health treatments in 8 herds over an 8-yr period of time. Genetic parameters of health treatment cost were estimated in first ( n = 2,214), second ( n = 1,487) and third ( n = 800) parities of US Holstein cows. The health treatments were uniformly defined and consistently recorded by 8 high-performance dairy herds in Minnesota from 2008 to 2015. A fixed treatment cost was assigned to 14 types of health treatments, and the cost included the mean veterinary expense obtained from the veterinary clinics that serviced the 8 herds, pharmaceuticals, and labor cost. The labor cost was $18/h, and the time incurred for each type of health treatment was determined from interviews with the herd owners. The 14 types of health treatment costs were partitioned into 5 categories: mastitis (including mastitis diagnostic test), reproduction (cystic ovary, retained placenta, and metritis), lameness (hoof treatments), metabolic (milk fever, displaced abomasum, ketosis, and digestive), and miscellaneous (respiratory, injury, and other). Health treatment cost for each cow was summed by category within lactation and also across categories within lactation. The estimates of heritability for health treatment cost were 0.13, 0.04, 0.10, 0.12, and 0.04 for the mastitis, reproduction, lameness, metabolic, and miscellaneous categories, respectively, in first parity. Genetic correlations between categories of health treatment cost in first parity were greatest for mastitis and reproduction ( r = 0.85); however, phenotypic correlations between all categories were small ( r < 0.16). Total health treatment cost had a large genetic correlation with somatic cell score (0.93) and 305-d milk production (0.44) in first parity; however, the genetic correlation (−0.60) between total health treatment cost and udder depth in first parity indicated a genetic relationship exists between shallow udders and less total health treatment cost. Total health treatment cost across categories had a heritability estimate of 0.25 in first parity, 0.16 in second parity, and 0.17 in third parity. Consequently, genetic selection for reduced health treatment cost should be possible by using producer-recorded health treatment records supplemented with treatment costs.

  PublisherOA PDFDOI

• Management of Sternal Wounds, Infections, and Sternal Non-Union with Plate Fixation: Result from a Single Site Experience

  Surgical Infections · 2023-02-03

  article

  Background: Patients with sternal wounds, infection, or non-union after cardiac surgery continue to have increased morbidity and mortality rates compared with those without sternal complications. Reconstructive methods have largely centered on soft tissue approaches, including muscle or omental flaps, which result in functional loss. Some data show early positive advantages using sternal rigid plate fixation (SRPF), however, it is debated in the setting of active infection. The goal of this study is to examine the outcomes of SRPF in patients with and without infections. Patients and Methods: This is a retrospective study of consecutive patients who underwent SRPF by a single plastic surgeon from April 2013 to August 2021. Patients treated without SRPF, lacking at least six months of follow-up, or those plated more than once were excluded. Ninety-seven patients were included. Demographic and peri-operative factors associated with sternal infection after SRPF were evaluated. Results: Sixty-eight patients were clinically infected/culture positive or open (INFECTED), and 29 were clean/primary plating (CLEAN). Sixteen percent of the INFECTED cases (11/68) returned with infection. Fourteen percent of the CLEAN cases (4/29) had subsequent infections. Additionally, we did note a decrease in rates of infections overall (p < 0.0001) as experience and frequency of plate fixation increased (p < 0.0001). Regardless of infection status, all but one patient had a healed and stable sternum at the end of data collection. Conclusions: There is no statistically significant difference between wound class prior to SRPF and development of infection after SRPF. Even in infected settings, patients can be treated successfully with SRPF. Further study is needed.

  PublisherDOI

• Health Treatment Cost of Holsteins in Eight High-Performance Herds

  Animals · 2023-06-22 · 6 citations

  articleOpen access

  = 2214) were recorded by the owners of eight high-performance dairy herds in Minnesota. Cows calved from March 2008 to October 2015, and 14 types of health treatments were uniformly defined across the herds. Specific types of health treatment were subsequently assigned a cost based on the mean veterinary cost obtained from the veterinary clinics that serviced the eight herds. A fixed labor cost for time (USD 18/h) associated with specific types of health treatment was determined based on interviews with the herd owners and was added to the veterinary cost. Health treatment cost was then partitioned into five health categories: mastitis (including mastitis diagnostic test), reproduction (cystic ovary, retained placenta, and metritis), lameness (hoof treatments), metabolic (milk fever, displaced abomasum, ketosis, and digestive), and miscellaneous (respiratory, injury, and other). Lactations of cows were divided into six intervals that corresponded with stage of lactation based on days in milk. The first interval of lactation was 30 days in length, followed by four intervals of 60 days each, and the final interval started on day 271 and had variable length because it continued to the end of lactation and included the dry period. Health treatment cost was summed within each interval of lactation and subsequently across lactations by parity. Statistical analysis by parity included the fixed effects of herd, interval, and the interaction of herd and interval, with interval regarded as a repeated measure of cows. Health treatment cost was highest during the first interval for all five parities of cows and ranged from USD 22.87 for first parity to USD 38.50 for fifth parity. Reproduction treatment cost was about one-half of the total health treatment cost during the first interval in all five parities. Metabolic treatment cost during the first interval ranged from USD 3.92 (in first parity) to USD 12.34 (in third parity). Compared to the other health categories, mastitis treatment cost was most evenly distributed across intervals of lactation in all parities. Lameness treatment cost was highest during mid- or late-lactation across parities and reflected the time when cows received routine hoof trimming. Additionally, treatment cost across health categories was summed across intervals of lactation for each cow, and the total health cost of cows varied substantially from herd to herd and ranged from USD 23.38 to USD 74.60 for first parity and usually increased with parity.

  PublisherOA PDFDOI

• 71. Feed efficiency of crossbreds of Montbéliarde, Viking Red, and Holstein with Holstein cows fed two alternative diets

  2022-12-31 · 1 citations

  articleSenior author

  The objective of this study was to compare three-breed rotational crossbred (CB) cows of the Montbéliarde, Viking Red, and Holstein (HO) breeds with HO cows fed two alternative diets for dry matter intake (DMI), fat plus protein production (CFP), body weight (BW), body condition score (BCS), feed efficiency and residual feed intake (RFI) from 46 to 150 days in milk during first lactation. Cows were fed either a traditional total mixed ration (TMR) diet (TRAD) or a higher fibre, lower starch TMR diet (HFLS). The CB cows fed HFLS had less DMI (-12%) compared with the HO cows fed TRAD. For CFP, CB and HO cows were not different when fed TRAD or HFLS. The mean RFI from 46 to 150 days was lower and more desirable for CB cows fed HFLS (-120.0 kg) compared with HO cows fed TRAD (85.3 kg).

  PublisherDOI

• Birth traits of Holstein calves compared with Holstein, Jersey, Montbéliarde, Normande, and Viking Red-sired crossbred calves

  Journal of Dairy Science · 2022-09-07 · 9 citations

  articleOpen access

  Holstein (HO) calves, 3-breed crossbred calves of Montbéliarde, Viking Red, and HO (MVH), and 3-breed crossbred calves of Normande, Jersey, and Viking Red (NJV) were compared for gestation length (GL), calf weight at birth (CW), calving difficulty (CD), and stillbirth (SB) in 2 research herds at the University of Minnesota. Calves were born from January 2009 to December 2019. For the St. Paul and Morris herds, HO calves (n = 1,121) were compared with MVH calves (n = 1,393) from primiparous and multiparous cows. For the single herd analysis at Morris, HO calves (n = 476), MVH calves (n = 922), and NJV calves (n = 405) were compared from primiparous and multiparous cows. Primiparous and multiparous births were analyzed separately because multiparous cows had multiple births, and CD and SB are likely different traits for primiparous and multiparous cows. Statistical analysis of GL, CW, CD, and SB included fixed effects of sex of calf, herd, breed group of calf, and year-season of calving. For the St. Paul and Morris herds, HO calves from primiparous (278 d) and multiparous (279 d) HO cows had shorter GL compared with MVH calves from primiparous (280 d) and multiparous (282 d) crossbred cows. The HO calves (39.4 and 43.2 kg, respectively) from primiparous and multiparous HO cows had lower CW compared with MVH calves (40.3 and 44.3 kg, respectively) from primiparous and multiparous crossbred cows. Calving difficulty and SB were not different for HO and MVH calves from primiparous and multiparous cows. For the single herd analysis at Morris, HO calves (278 and 279 d, respectively) from primiparous and multiparous HO cows had shorter GL compared with MVH calves (281 and 282 d, respectively) and NJV calves (282 and 282 d, respectively) from primiparous and multiparous crossbred cows. The CW of HO calves (38.6 and 42.0 kg, respectively) from primiparous and multiparous HO cows was lower compared with MVH calves (39.7 and 42.9 kg, respectively), but higher compared with NJV calves (35.1 and 38.0 kg, respectively) from primiparous and multiparous crossbred cows. Calving difficulty and SB did not differ for HO, MVH, and NJV calves from primiparous and multiparous cows. The longer GL for crossbred calves and higher CW for MVH calves did not increase CD and SB for primiparous and multiparous cows. Dairy producers may implement 3-breed rotational crossbreeding systems that include the HO, Jersey, Normande, Montbéliarde, and Viking Red breeds, and some breeds may increase GL and CW without an increase in CD and SB.

  PublisherOA PDFDOI

• Comparison of 3-breed rotational crossbreds of Montbéliarde, Viking Red, and Holstein with Holstein cows fed 2 alternative diets for dry matter intake, production, and residual feed intake

  Journal of Dairy Science · 2022-08-31 · 8 citations

  articleOpen accessSenior author

  The objective of this study was to compare 3-breed rotational crossbred (CB) cows of the Montbéliarde, Viking Red, and Holstein (HO) breeds with HO cows fed 2 alternative diets for dry matter intake (DMI), fat plus protein production (CFP), body weight (BW), body condition score (BCS), feed efficiency, and residual feed intake (RFI) from 46 to 150 days in milk (DIM) during first lactation. The CB cows (n = 17) and HO cows (n = 19) calved from September 2019 to March 2020. Cows were fed either a traditional total mixed ration diet (TRAD) or a higher fiber, lower starch total mixed ration diet (HFLS). The HFLS had 21% more corn silage, 47% more alfalfa hay, 44% less corn grain, and 43% less corn gluten feed than the TRAD. The 2 diets were analyzed for dry matter content, crude protein, forage digestibility, starch, and net energy for lactation. The BW and BCS were recorded once weekly. Daily milk, fat, and protein production were estimated from twice monthly milk recording with random regression. Measures of efficiency were CFP per kilogram of DMI and DMI per kilogram of BW. The RFI from 46 to 150 DIM was the residual error from regression of DMI on milk energy, metabolic BW, and the energy required for change in BW. Statistical analysis of all variables included the fixed effects of diet, breed group, and the interaction of diet and breed group. The CB cows fed HFLS had less DMI (-12%) and lower DMI/BW (-14%) compared with the HO cows fed TRAD. For CFP, CB and HO cows were not different when fed TRAD or HFLS. Furthermore, the CB cows fed HFLS had higher BW (+50 kg) compared with HO cows fed HFLS. The CB cows fed TRAD had higher BCS than HO cows fed TRAD and HO cows fed HFLS (+0.46 and +0.62, respectively). The HO cows fed TRAD had more DMI (+14%) and lower CFP per kilogram of DMI (-12%) compared with the HO cows fed HFLS. In addition, mean RFI from 46 to 150 DIM was lower and more desirable for CB cows fed HFLS (-120.0 kg) compared with HO cows fed TRAD (85.3 kg). Dairy producers may feed either TRAD or HFLS to CB cows without loss of CFP.

  PublisherOA PDFDOI

• Herd life, lifetime production, and profitability of Viking Red-sired and Montbéliarde-sired crossbred cows compared with their Holstein herdmates

  Journal of Dairy Science · 2021 · 21 citations

  Senior authorCorresponding
  • Animal science
  • Biology
  • Biotechnology

  The first 2 generations from a 3-breed rotation of the Viking Red (VR), Montbéliarde (MO), and Holstein (HO) breeds were compared with their HO herdmates in high-performance commercial herds in Minnesota. The designed study enrolled pure HO females in 2008 to initiate a comparison of 3-breed rotational crossbreds with their HO herdmates. Sires of cows were proven artificial insemination bulls selected for high genetic merit in each of the 3 breeds. The first-generation cows calved for a first time from 2010 to 2014 and had 376 VR × HO and 358 MO × HO crossbreds to compare with their 640 HO herdmates. The second-generation cows calved for a first time from 2012 to 2014 and had 109 VR × MO/HO and 117 MO × VR/HO crossbreds to compare with their 250 HO herdmates. Collection of data ceased on December 31, 2017, and all cows studied had the opportunity for 45 mo in the herd after first calving. Production of milk, fat, and protein (kg) during lifetimes of cows was estimated from test-day observations with best prediction. The lifetime profit function included revenue and cost. Revenue was from production, calves, and slaughter of cull cows. Costs included feed cost during lactation, lactating overhead cost, dry cow cost (including feed cost during dry periods), replacement cost, health treatment cost, insemination cost, fertility hormone cost, pregnancy diagnosis cost, hoof trimming cost, and carcass disposal cost. For individual cows with herd life longer than 45 mo after first calving, survival of cows was projected beyond 45 mo after first calving to estimate herd life, production, and profitability. The 2-breed crossbreds had +158 d longer herd life and the 3-breed crossbreds had +147 d longer herd life compared with their respective HO herdmates. Also, 12.4% of the 2-breed crossbreds died up to 45 mo after first calving compared with 16.3% of their HO herdmates. Furthermore, approximately 29% of both the 2-breed and 3-breed crossbreds lived beyond 45 mo after first calving compared with approximately 18% of their respective HO herdmates. On a lifetime basis, the 2-breed and 3-breed crossbreds provided +$122 and +$134, respectively, more cull cow revenue compared with their HO herdmates. For lifetime replacement cost, the 2-breed crossbreds did not differ from their HO herdmates; however, the 3-breed crossbreds had -$28 less lifetime replacement cost compared with their HO herdmates because of their younger age at first calving. The combined 2-breed crossbreds had +$0.473 (+13%) more daily profit (ignoring potential differences for feed efficiency) and the combined 3-breed crossbreds had +$0.342 (+9%) more daily profit compared with their respective HO herdmates. This resulted in +$173 more profit/cow annually for the combined 2-breed crossbreds and +$125 more profit/cow annually for the combined 3-breed crossbreds compared with their respective HO herdmates.

  PublisherOA PDFDOI

• Health treatment cost, stillbirth, survival, and conformation of Viking Red-, Montbéliarde-, and Holstein-sired crossbred cows compared with pure Holstein cows during their first 3 lactations

  Journal of Dairy Science · 2020 · 20 citations

  Senior authorCorresponding
  • Animal science
  • Veterinary medicine
  • Biology

  Three generations of crossbreds from a 3-breed rotation of the Viking Red (VR), Montbéliarde (MO), and Holstein (HO) breeds were compared with their HO herdmates in 7 commercial dairy herds in Minnesota. The designed study enrolled 3,550 HO females in 2008 to initiate crossbreeding and a control of pure HO herdmates within each herd. Service sires were high-ranking, proven AI bulls selected for high genetic merit within each of the VR, MO, and HO breeds. Cows in this study calved from 2010 to 2017 and collection of data ended on December 31, 2017. The first generation of cows consisted of 644 VR × HO and 616 MO × HO crossbreds and their 1,405 HO herdmates. The second generation had 615 VR × MO/HO and 568 MO × VR/HO crossbreds and their 1,462 HO herdmates. The third generation had 466 combined HO × VR/MO/HO and HO × MO/VR/HO crossbreds and their 736 HO herdmates. Total health cost was the sum of veterinary treatment cost, pharmaceutical cost, and farm labor cost to treat 16 different health disorders. Conformation traits and body condition score were subjectively scored once during early lactation for each of the first 3 lactations of cows. Total health cost of the 2-breed crossbreds was significantly lower during first (-23%), second (-29%), and third (-21%) lactation compared with their HO herdmates. For the 3-breed crossbreds, total health cost did not differ during first lactation but was -26% lower during both second and third lactation compared with their HO herdmates. The stillbirth rate for calves born to 2-breed crossbred dams (4%) was significantly lower compared with calves born to their HO herdmates (8%) at first calving. Survival from first to third calving (+9%) and first to fourth calving (+11%) was significantly higher for the 2-breed crossbreds compared with their HO herdmates. Also, the 3-breed crossbreds had significantly higher survival to third (+11%) and fourth (+19%) calving compared with their HO herdmates. Across each generation of crossbreeding, the crossbreds had uniformly shorter stature, less angularity, and less body depth compared with their respective HO herdmates. The crossbred cows also had significantly less udder clearance from the hock but significantly more rear teat width and longer teat length compared with their respective HO herdmates. Furthermore, the crossbred cows had higher body condition score compared with their HO herdmates during each of their first 3 lactations.

  PublisherOA PDFDOI

• Fertility and 305-day production of Viking Red-, Montbéliarde-, and Holstein-sired crossbred cows compared with Holstein cows during their first 3 lactations in Minnesota dairy herds

  Journal of Dairy Science · 2020 · 17 citations

  Senior authorCorresponding
  • Animal science
  • Biology
  • Veterinary medicine

  Three generations of crossbred cows from a 3-breed rotation of the Viking Red (VR), Montbéliarde (MO), and Holstein (HO) breeds were compared with HO herdmates in 7 high-performance, commercial dairy herds in Minnesota. The designed study was initiated in 2008 with the enrollment of 3,550 HO females. Sires of cows were proven artificial insemination bulls and were high-ranking for genetic merit within each of the VR, MO, and HO breeds. The first generation of cows calved a first time from 2010 to 2017 and consisted of 644 VR × HO and 616 MO × HO 2-breed crossbreds and their 1,405 HO herdmates. The second generation calved a first time from 2012 to 2017 and consisted of 615 VR × MO/HO and 568 MO × VR/HO crossbreds and their 1,462 HO herdmates. The third generation calved a first time from 2014 to 2017 and was composed of 466 HO × VR/MO/HO and HO × MO/VR/HO crossbreds combined and their 736 HO herdmates. Collection of data ceased on December 31, 2017, and for the duration of study, many of the 2-breed and 3-breed crossbreds and their HO herdmates had the opportunity to complete at least 3 lactations, whereas the HO-sired crossbreds and their HO herdmates had the opportunity to complete 1 lactation. The 305-d actual (not mature equivalent) production of milk, fat, and protein was estimated from test-day observations with best prediction and cows with <305 DIM were projected to 305 d. The 2-breed and 3-breed crossbred cows had superiority over their HO herdmates for all of the fertility traits measured. The 2-breed crossbreds had -9, -17, and -15 d fewer days open than their HO herdmates during first, second, and third lactation, respectively. Also, the 3-breed crossbreds had -15, -19, and -20 d fewer days open than their HO herdmates during first, second, and third lactation, respectively. Cows in these herds had young ages at first calving of 22 to 23 mo across the breed groups, and the 3-breed crossbreds had significantly younger ages at first, second, and third calving than their HO herdmates. The 2-breed crossbreds had +2% higher fat plus protein production (kg) during first lactation, but did not differ during second and third lactation, from their HO herdmates. The 3-breed crossbreds had -3% to -4% lower fat plus protein production (kg) than their HO herdmates in each of their first 3 lactations. During first lactation, the HO-sired crossbreds did not differ for fat plus protein production (kg) from their HO herdmates.

  PublisherOA PDFDOI

Frequent coauthors

• Brad Heins

  University of Minnesota

  25 shared

• Charles W. Young

  Pulmonary Associates

  17 shared

• H. Chester-Jones

  University of Minnesota, Waseca

  16 shared

• P. Boettcher

  15 shared

• A.R. Hazel

  University of Minnesota

  13 shared

• A.J. Seykora

  University of Minnesota

  12 shared

• P.M. VanRaden

  United States Department of Agriculture

  11 shared

• M.M. Schutz

  11 shared

Labs

• Rock & Mineral Physics LaboratoryPI