About

Duarte Diaz is a Professor and Dairy Extension Specialist at the University of Arizona, affiliated with the School of Animal and Comparative Biomedical Sciences. He is based at the Agricultural Research Center in Tucson, Arizona, and is involved in extension activities related to dairy science. His work focuses on providing expertise and support in dairy production, contributing to research and community outreach efforts within the field of animal sciences. Duarte Diaz's role includes engaging with the community and advancing knowledge in animal and dairy sciences through extension services.

Research topics

• Biology
• Chemistry
• Internal medicine
• Animal science
• Medicine
• Endocrinology
• Ecology
• Cell biology
• Biochemistry
• Genetics

Selected publications

• 215 Tracking growth performance and insulin response on four-month-old maternal heat-stressed lambs

  Journal of Animal Science · 2024-09-01

  articleOpen access

  Abstract Poor growth performance and metabolic disorders are prevalent problems in lambs exposed to maternal heat stress, specifically during the last mid-third of gestation. Columbia–Rambouillet crossbred lambs (n = 12) were immediately separated from their heat-stressed and non-stressed dam at lambing. The maternal heat stress exposure occurred during the last mid-third gestation and was for about 40 d (40 to 80 d). Lamb body weight (BW) was recorded daily for 4 mo. A glucose tolerance test was performed in mo 4 to evaluate glucose concentrations and insulin response. Maternal heat-stressed lamb (HS) presented reduced BW throughout the experimental time (P < 0.05) than maternal thermoneutral lamb (TN; CN = 12.69 ± 0.29 kg and HS = 9.89 ± 0.29 kg). Glucose concentrations were similar between environmental conditions (P > 0.05). Neither the insulin response presented a significance (P > 0.05) between those lambs exposed to HS and TN conditions during gestation. Although maternal exposure to HS can affect performance of the offspring throughout life, metabolic disorders associated with insulin resistance are not a problem at 4 mo. However, preliminary data showed that these same lambs at 8 mo old and 11 mo old show an irregular insulin response in maternal heat-stressed lambs that can persist throughout the life of the offspring.

  PublisherOA PDFDOI

• PSIV-2 Gestational heat stress and its impact on placental weight, colostrum production, and milk production on Columbia-Rambouillet ewes

  Journal of Animal Science · 2024-09-01 · 2 citations

  articleOpen accessSenior author

  Abstract Heat stress during pregnancy causes placental insufficiency and resduces fetal growth by reducing the oxygen and nutrients availability. In lactating production animals, heat stress during gestation lowers performance by decreasing milk yield and impairing reproduction. The study objectives were to understand the consequences of the exposure to warm environmental conditions during pregnancy on placental weight, colostrum production, and milk production of ewes utilizing heat chambers. Columbia-Rambouillet pregnant ewes with singletons (n = 11) were assigned to one of two environmental treatments: 1) heat stress (HS) or 2) thermoneutral (TN; 22°C) during mid-gestation (d 40 to 80) for a duration of 40 d. Heat stress consisted of 12 h at 40°C/55% humidity and 12 h at 35°C/45% humidity. Dry matter intake (DMI) and water intake (WI) were measured daily for both treatment groups. Feed and water were given ad libitum for HS ewes and TN ewes were pair fed to HS ewes for the entire duration of study. At lambing, the offspring were separated from dams. Measurements were taken of placental weight and colostrum production. The placental weights from HS ewes had a mean of 218 g compared with the placental weights of the TN group at a mean of 396 g (P < 0.01). Colostrum was measured for the first 24 h post lambing. The mean colostrum production of TN was 718 mL and for the HS group it was 882 mL. The colostrum production differences between control and HS groups were nonsignificant. Following lambing, ewes were milked twice a day for a 21-d period to evaluate milk production. Daily milk production for HS ewes was a mean of 1.16 kg/d while the TN group ewes had a mean of 1.31 kg/d (P < 0.01). Exposure of HS during mid-gestation had a significant impact on placental weight and 21-d milk production.

  PublisherOA PDFDOI

• Prevalence of <i>e.coli</i> O157:H7, <i>Salmonella</i>, and <i>Cryptosporidium </i>Among Arizona Dairy Workers Using Post-Work Swabbing

  Journal of Agricultural Safety and Health · 2024-01-01

  article

  HIGHLIGHTS: Microbial assessment of dairy workers in Arizona, U.S. Provides demographic and working information of an underserved group. Highlights the need for health and safety assessments and solutions in the dairy industry. ABSTRACT: The dairy industry in Arizona, like many other agricultural industries in the United States, is dependent on the labor that migrant farm workers provide. Infections caused by zoonotic pathogens are commonly underreported or misdiagnosed, and possibly more so in migratory workers that face cultural, structural, legal, financial, and geographic barriers to health services. The objectives of this project were to: assess the demographics of Arizona dairy workers, determine the exposure potential of Arizona dairy workers to zoonotic organisms, and inform best management practices. A questionnaire including demographics, work tasks, and household characteristics was administered. Swab samples were collected from the shoulders, knees, and foreheads of employees at two dairy operations at the end of the work shift. The swabs were cultured for E.coli O157:H7 and Salmonella. Molecular DNA isolated from Salmonella and Cryptosporidium was quantified using droplet-digital Polymerase Chain Reaction (ddPCR). Twenty dairy workers were recruited, and 60 samples were collected. The majority of workers were male, preferred to speak Spanish, and identified as Latino/Hispanic (68.8%, 93.8%, and 93.8%, respectively). E. coli O157:H7 was detected in 13% of cultured knee and forehead samples. Salmonella spp. gene copies were detected on 60.0% of samples collected from forehead skin samples; 40.0% of shoulder clothing samples; and 15% of knee clothing samples, as measured via ddPCR. The positive cultural and molecular samples indicate the need for improved post-workday sanitation practices at farms. This study provides surveillance of a largely invisible population, including insights that can be used to create site-specific health and safety protocols for the dairy industry, inform risk assessment models, and foster preventive practices in the dairy industry.

  PublisherDOI

• PSVIII-A-8 Growth and Physiological Responses to Heat Stress and Zilpaterol Hydrochloride in Angus and Brahman Steers

  Journal of Animal Science · 2023-11-06

  articleOpen accessSenior author

  Abstract The response to zilpaterol hydrochloride supplementation by two breeds of beef steers under controlled heat stress conditions were evaluated for impacts on growth, carcass merit, and physiological stress indicators. In two separate studies, Brahman and Angus steers were placed in environmental chambers and housed for 21 d under 1 of 2 environmental conditions 1) heat stress (THI = 73 to 85) or thermoneutral (THI = 68). In a 2 x 2 factorial, steers also received 8.38 mg· kg-1· d-1 on 88% DM of zilpaterol hydrochloride (ZH) or soybean meal carrier only for the 21-d period. Feed intake, respiratory rate, and rectal temperatures were evaluated daily. Total weight gain was recorded and used to calculate average daily gain (ADG) and gain-to-feed ratio (G:F). Brahman steers were harvested at the market weight (489.31 ± 97.7 kg) and Angus steers on d ~22 after treatment (307.26 ± 6.23 kg). In both studies, body weight gain and ADG did not differ between environments or supplements. Brahman steers exposed to heat stress exhibited greater (P &amp;lt; 0.05) respiratory rate than thermoneutral steers, regardless of supplement. An environment x day interactions (P &amp;lt; 0.04) was observed for rectal temperature. On d 8, unsupplemented heat-stressed Brahman steers had higher (P &amp;lt; 0.05) rectal temperatures than ZH-supplemented thermoneutral steers. On d 11, ZH-supplemented heat-stressed Brahman steers had higher (P &amp;lt; 0.05) rectal temperatures than unsupplemented thermoneutral steers. Angus steers exposed to heat stress exhibited greater (P &amp;lt; 0.05) respiration rates throughout the experiment than thermoneutral steers. On d 8, unsupplemented heat-stressed Angus steers exhibited greater (P &amp;lt; 0.05) respiration rates than ZH-supplemented heat-stressed steers. On d 8 and 19, heat-stressed Angus steers exhibited greater (P &amp;lt; 0.05) rectal temperatures than thermoneutral steers. Angus steers exhibited an environment x supplement x day interaction (P &amp;lt; 0.05) for rectal temperature, with a decrease (P &amp;lt; 0.05) rectal temperature in ZH-supplemented steers. Carcass merit traits did not differ between environments in Brahman steers. Cold carcass weights were lighter (P &amp;lt; 0.05) in heat-stressed Angus steers compared with thermoneutral steers. ZH-supplemented Angus (but not Brahman) steers exhibited decreased (P &amp;lt; 0.05) respiration rates and rectal temperatures. Together these findings indicate that Brahman steers were more resistant to heat stress than Angus steers but were less efficient, with ~10% less G:F. Based upon the data collected, supplementation with zilpaterol hydrochloride did not negatively impact production in either breed.

  PublisherOA PDFDOI

• Transcriptome analyses indicate that heat stress-induced inflammation in white adipose tissue and oxidative stress in skeletal muscle is partially moderated by zilpaterol supplementation in beef cattle

  Journal of Animal Science · 2022 · 30 citations

  • Biology
  • Animal science
  • Internal medicine

  Heat stress (HS) triggers oxidative stress, systemic inflammation, and disrupts growth efficiency of livestock. β-adrenergic agonists supplemented to ruminant livestock improve growth performance, increase skeletal muscle mass, and decrease carcass fat. The objective of this study was to understand the independent and interacting effects of HS and zilpaterol hydrochloride (ZH) supplementation on the transcriptome of subcutaneous white adipose tissue and the longissimus dorsi muscle in steers. Twenty-four Red Angus-based steers were assigned to thermoneutral (TN; Temperature Humidity Index [THI] = 68) or HS (THI = 73-85) conditions and were not supplemented or supplemented with ZH (8.33 mg/kg/d) for 21 d in a 2 × 2 factorial. Steers in the TN condition were pair-fed to the average daily feed intake of HS steers. RNA was isolated from adipose tissue and skeletal muscle samples collected via biopsy on 3, 10, and 21 d and sequenced using 3' Tag-Seq to an achieved average depth of 3.6 million reads/sample. Transcripts, mapped to ARS-UCD1.2, were quantified. Differential expression (DE) analyses were performed in DESeq2 with a significance threshold for false discovery rate of 0.05. In adipose, 4 loci (MISP3, APOL6, SLC25A4, and S100A12) were DE due to ZH on day 3, and 2 (RRAD, ALB) were DE due to the interaction of HS and ZH on day 10 (Padj < 0.05). In muscle, 40 loci (including TENM4 and OAZ1) were DE due to ZH on day 10, and 6 loci (HIF1A, LOC101903734, PDZD9, HNRNPU, MTUS1, and TMCO6) were DE due to environment on day 21 (Padj < 0.05). To explore biological pathways altered by environment, supplement, and their interaction, loci with DE (Praw < 0.05) were evaluated in Ingenuity Pathway Analysis. In adipose, 509 pathways were predicted to be altered (P < 0.01): 202 due to HS, 126 due to ZH, and 181 due to the interaction; these included inflammatory pathways predicted to be upregulated due to HS but downregulated due to the interaction of HS and ZH. In muscle, 113 pathways were predicted to be altered (P < 0.01): 23 due to HS, 66 due to ZH, and 24 due to the interaction of HS and ZH. Loci and pathway data in muscle suggest HS induced oxidative stress and that the stress response was moderated by ZH. Metabolic pathways were predicted to be altered due to HS, ZH, and their interaction in both tissues. These data provide evidence that HS and ZH interact to alter expression of genes in metabolic and immune function pathways and that ZH moderates some adverse effects of HS.

  PublisherOA PDFDOI

• 12 Growth Performance, Physiology, and Carcass Merit of Supplementing Brahman Steers with Zilpaterol Hydrochloride Under Heat Stress Conditions

  Journal of Animal Science · 2022-10-22 · 1 citations

  articleOpen accessSenior author

  Abstract Supplementation with a β- adrenergic agonist (β-AA) for 21 days in Brahman steers under heat stress conditions (HS) was evaluated with respect to feedlot performance and carcass merit. Twenty-four Brahman steers (kg = 338 ± 39) were housed in two controlled environment chambers with one of two environmental (ENV) conditions 1) heat stress (HS; THI = 73 to 85) and 2) thermoneutral (TN; THI = 68) with either Zilpaterol hydrochloride (ZL) or soymeal supplementation (CN) using a randomly assigned in a 2 x 2 factorial design (n=6/group). Daily data were collected for dry matter intake, water intake, respiratory rate (RR), and rectal temperature (RT). At the end of 21 d period, total weight gain was used to calculate average daily gain (ADG) and gain to feed. Blood samples were collected from the jugular vein on days -7, 3, 10, and 21 for cortisol analysis, and biological impedance analysis (BIA) was determined on days 3, 10, and 21 on each animal. Steers were harvested at 544 kg on average post supplementation/environment conditions, and carcass merit was determined. There were no differences (P &amp;gt; 0.05) in feedlot performance. Brahmans exposed to heat stress had greater RR during the heat stress periods of the experiment, regardless of supplementation. Environment and day interactions (P &amp;lt; 0.04) were observed for RT, HS steers had a greater RT on d 8 but similar RT on d 15 and 19. Stressed steers with ZL had higher RT (P &amp;lt; 0.05) than TN/CN steers on d 11. There was no interaction (P &amp;gt; 0.05) between environmental conditions and CN and ZH supplementation for cortisol concentrations. Regardless of environmental treatment or supplementation, no difference (P &amp;gt; 0.05) was associated with BIA characteristics. There were no differences (P &amp;gt; 0.05) for hot carcass weight, cold carcass weight, USDA yield grade, 12th rib loin eye area, marbling score, KPH percentage, and 12th rib fat thickness between groups. Twelfth-rib loin eye area lean color from HS/CN had higher lightness (L*) (P &amp;lt; 0.05) than TN/CN steers. HS/CN steers present a similar (L*) to ZL in TN and HS conditions. Redness-greenness (a*) was greater (P = 0.01) in carcasses from HS steers with or without ZL than TN/ZL but similar to TN/CN. Steers exposed to HS and CN had a higher (P = 0.02) change of 12th rib lean color from yellow to blue (b*) than TN steers with CN and ZL. Supplementation with β-AA did not negatively impact growth, carcass performance, or carcass merit in heat-stressed steers.

  PublisherOA PDFDOI

• Beta-adrenergic agonists and heat stress impact skeletal muscle gene expression and mitochondrial function in beef cattle

  Translational Animal Science · 2021 · 2 citations

  • Cell biology
  • Endocrinology
  • Internal medicine

  Open access journal

  PublisherOA PDFDOI

• Supplementing zilpaterol hydrochloride to heat-stressed beef cattle for 21 d alters the adipose transcriptome and is predicted to alter stress response pathways

  Translational Animal Science · 2021-11-30

  articleOpen access

  Open access journal

  PublisherOA PDFDOI

• 131 Zilpaterol Hydrochloride and Heat Stress Each Alter the Cattle Adipose Transcriptome and Predicted to Alter Molecular Pathways After 21 Days

  Journal of Animal Science · 2021-05-01

  articleOpen access

  Abstract Heat stress reduces livestock performance while supplementation of beta-adrenergic agonists (βAA) such as zilpaterol hydrochloride (ZH) improve production efficiency; both stimulate lipolysis. The objective of this study was to understand the effects (independent, interacting) of heat stress and ZH on the subcutaneous adipose transcriptome in fed steers. 24 Red Angus steers were assigned to thermoneutral (TN; THI=68) or heat stress (HS; THI=83) conditions and fed no supplement (NS) or ZH (8.33 mg/kg/day) for 21d in a 2x2 factorial. TN steers were pair-fed the HS daily average. Subcutaneous adipose samples were collected at day -3, 3, 10, and 21. RNA was isolated and sequenced using 3’ Tag-Seq reads to a depth of 3.6 million reads/sample. Transcripts were mapped to ARS-UCD1.2 and quantified. After quality control, differential expression (DE) analyses were performed in DESeq2 with a significance threshold (FRD) of 0.05. Pathway analysis was used to explore pathways affected by HS, ZH, and their interaction using DE loci (P &amp;lt; 0.05). The acute phase response signaling pathway was predicted to be activated at 3d, but inhibited at 10d and 21d by the combination of HS and ZH. At multiple time points, inflammatory pathways including those for interferon and IL-8 were predicted to be activated by HS. Mitochondrial function pathways including oxidative phosphorylation, mitochondrial dysfunction, and TCA cycle II were altered by ZH. Adipose centric pathways for phospholipase-C and protein kinase-A signaling were altered by HS/ZH interaction while glycolysis was altered solely by HS. These data support the hypothesis that exposing cattle to HS conditions and ZH supplementation alters the subcutaneous adipose transcriptome, but not necessarily in an additive fashion. These data provide information regarding the supplementation of βAA in heat stress environments, especially if it mediates the effects of HS.

  PublisherOA PDFDOI

• 256 Heat stress and β-adrenergic agonists alter the adipose transcriptome and fatty acid mobilization in ruminant livestock

  Journal of Animal Science · 2020-11-03 · 1 citations

  articleOpen access

  Abstract Heat stress (HS) negatively impacts livestock performance and carcass traits while beta-adrenergic agonist (βAA) supplementation improves animal production and efficiency; both can stimulate lipolysis in adipose. The objective of this study was to understand the independent and interacting effects of HS and βAA on the subcutaneous adipose transcriptome in lambs and on visceral adipose fatty acid mobilization in steers. For study 1, 24 wethers were assigned to thermal neutral (TN THI = 65) or HS (THI = 80) conditions and supplemented without (NS) or with ractopamine hydrochloride (RH) for 30d in a 2 x 2 factorial. TN lambs were pair-fed the average intake of HS. RNA collected from subcutaneous fat at harvest was sequenced. Differential expression (DE) analyses identified 71 (Padj &amp;lt; 0.05) loci altered due to the interaction of environment and supplement. No DE genes were observed for the main effect of supplement, but HS reduced expression (P &amp;lt; 0.05) of RBM3 and increased expression (P &amp;lt; 0.05) of ATXN7L1. HS was predicted by pathway analyses to impair adipogenesis and fatty acid mobilization. In study 2, 24 steers were assigned to TN (THI = 65) or HS (THI = 83) and NS or zilpaterol hydrochloride (ZH) treatments for 21d in a 2 x 2 factorial. TN steers were pair-fed the intake of their HS cohort. Ex vivo fatty acid mobilization from visceral adipose in response to 0 or 1µM epinephrine was quantified at harvest. Fatty acid mobilization did not differ among groups when unstimulated, but epinephrine-stimulated mobilization was less (P = 0.05) in HS and greater (P &amp;lt; 0.01) in ZH steers. These findings indicate that heat stress-induced reduction of fatty acid mobilization from adipose may be associated with increased expression of stress-responsive genes. Moreover, the stimulatory effect of ZH on epinephrine-induced fatty acid mobilization was present after chronic treatment. Our data have yet to identify an interaction between HS and βAA supplementation that demonstrably impacts well-being.

  PublisherOA PDFDOI

Frequent coauthors

• Pablo C Grijalva

  University of Nebraska–Lincoln

  9 shared

• Dustin T Yates

  University of Nebraska–Lincoln

  9 shared

• Ty B Schmidt

  University of Nebraska–Lincoln

  9 shared

• Jessica L. Petersen

  University of Nebraska–Lincoln

  8 shared

• Rachel R Reith

  University of Nebraska–Lincoln

  8 shared

• Renae L Sieck

  University of Nebraska–Lincoln

  7 shared

• Maurizio Moschini

  Università Cattolica del Sacro Cuore

  7 shared

• Francesco Masoero

  Università Cattolica del Sacro Cuore

  6 shared

Education

• Ph.D., Animal and Dairy Science

  North Carolina State University

  2001

• M.S., Animal and Dairy Science

  North Carolina State University

  1997

• B.A., Biology

  Jacksonville University

  1995