改良基体改进剂对石墨炉法测定饲料中硒含量的影响

实验对比研究了塞曼效应石墨炉原子吸收法测定饲料样品中硒含量。以硝酸钯(Pd(NO3)2)、三氯醋酸(TCA)、及Pd(NO3)2+TCA作为基体改进剂可使吸光度分别增加4倍、15倍及21倍,检出下限分别为20μg/ml、8μg/ml、6μg/ml。以塞曼效应扣除背景吸收,能有效地克服Fe2+、Cu2+、Mn2+等共存离子的干扰。通过对不同类型饲料中硒含量检测可知,混合型的基体改进剂能够提高硒含量测定的灵敏度及回收率。     

微波消解-石墨炉原子吸收光谱法测定鱼粉中的镉和铬

采用微波消解技术处理样品,用石墨炉原子吸收光谱法测定,对消解溶剂和微波条件进行了优化,研究了石墨炉原子吸收法的测定条件。结果表明,以HNO3+HClO4+H2O2作为微波消解溶剂效果最佳,在基体改进剂NH4H2PO4和Pd(NO3)2存在下,可有效地消除基体的影响,建立了微波-石墨炉原子吸收光谱法测定鱼粉中镉(Cd)和铬(Cr)的方法,Cd和Cr检出限分别为0.17ng/mL和0.46ng/mL;回收率分别为88.2%～94.1%(RSD:2.7%,n=6)、91.7%～106.2%(RSD:6.6%,n=6)。     

微波消解-石墨炉原子吸收光谱法测定醋酸地塞米松中的微量硒

采用微波制样技术对样品进行消解,减少了消化过程中硒的损失,利用石墨炉原子吸收光谱法对醋酸地塞米松中微量硒进行测定.以4 mg/mL Pd(NO3)2作为基体改进剂,灰化温度为950 ℃,原子化温度为2 100 ℃时,经氘灯校正背景,测定硒含量,回收率在89.24%～112.37% 之间,方法的相对标准偏差为7.42%,检出限为0.53 ng/mL.该法具有简便、快速、灵敏、稳定、准确等优点,适用于醋酸地塞米松中微量硒的分析测定.     

微波消解-石墨炉原子吸收光谱法测定9种中兽药散剂中铅含量

建立了微波消解-石墨炉原子吸收光谱法（GFAAS）测定9种中兽药散剂中铅含量的方法。采用微波消解技术处理样品,对消解溶剂、微波条件以及石墨炉原子吸收法的测定条件进行了优化。结果表明,以HNO3＋HClO4＋H2O2（4＋0.5＋1,V＋V＋V）作为微波消解溶剂最佳,基体改进剂Pd（NO3）2可有效地消除基体的影响。此方法的线性范围为5.00～80.00 ng/mL（r=0.9978）,检出限为0.39 ng/mL,添加回收率为87.1%～96.3%,相对标准偏差（RSD）为1.9%～6.9%（n=9）,将该方法应用于9种中兽药散剂中铅含量的测定,结果令人满意。     

水浴湿法消化Zeeman石墨炉原子吸收法测定肉鸡肝组织中硒含量

采用水浴湿法消化 ,以 Pd( NO3) 2 - Triton X- 10 0作为基体改进剂 ,应用 Zeem an石墨炉原子吸收法测定了肝组织硒含量。试验结果表明 ,肝组织经水浴湿法消化测得的硒含量与消化炉湿法消化测定结果基本一致 ( P >0 .0 5) ,相对标准偏差为 1.11%,回收率为 95.80 %～ 10 0 .4 0 %。石墨炉原子吸收法测定硒的检测限为 5.0 μg/ L     

石墨炉原子吸收法测定饲料中的硒

本文研究用石墨炉原子吸收分光光谱仪测定饲料原料及成品中硒含量的方法。用Pd(NO_3)_2作为基体改进剂,重点研究了基体改进剂的体积、灰化温度和原子化温度对吸光值的影响,同时以此为基础建立了饲料中硒的优化分析方法。此方法中硒含量在0~100μg/L成线性关系,检测限为0.33μg/kg,回收率为95.0%~105.3%。该方法具有简单、灵敏、准确的优点,适合饲料原料和成品中硒的含量分析。     

胰岛素对奶牛乳腺上皮细胞生长及κ-酪蛋白和胰岛素受体基因表达的影响

本试验旨在研究培养基中添加不同浓度的胰岛素对奶牛乳腺上皮细胞生长及κ-酪蛋白(CSN3)和胰岛素受体(INSR)基因表达的影响。选用中国荷斯坦奶牛的乳腺上皮细胞进行体外培养,在以无血清无激素的生长培养基为对照的基础上,分别添加胰岛素5、50、500和5 000 ng/mL,测定CSN3和INSR基因表达量以及CSN3相对含量的变化。结果表明:1)胰岛素能够促进乳腺上皮细胞的增殖,其中5～500 ng/mL的胰岛素促增殖作用较好。2)胰岛素能提高乳腺上皮细胞CSN3、INSR基因表达量和CSN3相对含量,50 ng/mL组CSN3基因表达量和CSN3相对含量均显著或极显著高于对照组(P<0.01)以及5(P<0.01)、500(P<0.01)和5 000 ng/mL组(P<0.05),INSR基因表达量显著或极显著高于对照组(P<0.05)以及500(P<0.05)和5 000 ng/mL组(P<0.01)。结果提示,随着胰岛素浓度的增加,CSN3和INSR基因的表达量及CSN3相对含量均呈先增加后下降的趋势,50 ng/mL时最高,而高浓度(5 000 ng/mL)的胰岛素不利于奶牛乳腺上皮细胞合成乳蛋白。     

蓝狐阴茎化学成分的研究

应用放射免疫测定技术及激光速率散射比浊法对蓝狐阴茎中某些化学成分进行测定分析 ,得出与蓝狐生殖有关的睾酮 (T)、孕酮 (P)、17β -雌二醇 (E2 )、生长激素 (GH)、人绒毛膜促性腺激素 (HCG) ,其含量分别为 (2 0 5 0± 3 6 5 )ng/g、(0 6 7± 0 12 )ng/g、(99 2 5± 9 87)pg/g、(18 2 1± 2 98)ng/g、(4 5 6 3± 5 2 9)mIU/g ,得出与蓝狐生命活动有关的三碘甲状腺原氨酸 (T3 )、四碘甲状腺原氨酸 (T4)、生物信使cAMP、cGMP及免疫球蛋白IgA、IgG、IgM等成分含量分别为 (1 17± 0 17)ng/g、(2 6 13± 3 6 6 )ng/g、(2 1 39± 2 89)ng/g、(2 7 75±3 18)ng/g、(0 0 8± 0 0 1)mg/g、(0 0 7± 0 0 2 )mg/g、(0 0 4± 0 0 1)mg/g。     

青海细毛羊和半细毛羊血清NO和NOS的测定

对生活在海拔 2 2 6 0m的青海细毛羊和海拔 2 5 0 0m的青海半细毛羊血清中NO和NOS进行了测定 ,结果为 :5 0 0 0 μmol/L± 12 71μmol/L和 30 83μmol/L± 2 1 31μmol/L ;2 0 5 0u/mL± 2 4 4u/mL和 19 5 7u/mL± 4 6 5u/mL。青海细毛羊的血清NO含量显著高于半细毛羊 (P <0 0 5 ) ,NOS在两种羊中无显著差异 (P >0 0 5 )。     

博落回提取物对脂多糖诱导猪应激细胞应激参数及免疫球蛋白G和超氧化物歧化酶mRNA表达的影响

本文旨在研究博落回提取物对脂多糖(LPS)诱导猪应激细胞应激参数及免疫球蛋白G(IgG)和超氧化物歧化酶(SOD)mRNA表达的影响。试验选用猪胚胎背部成纤维细胞,分别用正常细胞和以LPS刺激细胞建立的应激模型进行试验,对照组采用基础培养液,土霉素组在基础培养液中添加土霉素50μg/mL(阳性对照),博落回组在基础培养液中分别添加50、100、150 ng/mL的博落回提取物。检测IgG、溶菌酶(LSZ)、一氧化氮(NO)含量,一氧化氮合酶(NOS)、乳酸脱氢酶(LDH)活性以及IgG和SOD mRNA表达量。结果表明:1)博落回组IgG、NO和LSZ含量及NOS活性均极显著高于对照组(P<0.01),土霉素组IgG和LSZ含量极显著高于对照组(P<0.01)。2)对应激细胞和正常细胞而言,博落回组IgG mRNA表达量均极显著高于对照组和土霉素组(P<0.01),50和100 ng/mL博落回组均极显著高于150 ng/mL博落回组(P<0.01)。土霉素组IgG mRNA表达量极显著高于对照组(P<0.01)。100 ng/mL博落回组应激细胞IgG mRNA表达量极显著高于正常细胞(P<0.01)。3)对应激细胞和正常细胞而言,与对照组相比,添加博落回提取物50、100、150 ng/mL均极显著提高SOD mRNA表达量(P<0.01)。土霉素组SOD mRNA表达量极显著高于对照组和博落回组(P<0.01)。各组应激细胞SOD mRNA表达量均显著或极显著高于正常细胞(P<0.01)。综合各项指标,博落回提取物可提高LPS应激细胞IgG、NO和LSZ的含量及NOS活性,提高应激细胞和正常细胞IgG和SOD mRNA的表达量,总体效果优于土霉素,较好的添加浓度为50～100 ng/mL。     

In vitro effects of Actinobacillus pleuropneumoniae on inducible nitric oxide synthase and cyclooxygenase-2 in porcine alveolar macrophages

OBJECTIVE: To determine the amount of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) activity in alveolar macrophages in response to Actinobacillus pleuropneumoniae (APP) by determining nitric oxide (NO) and prostaglandin E2 (PGE2) concentrations. SAMPLE POPULATION: Freshly isolated porcine alveolar macrophages. PROCEDURE: Alveolar macrophages were incubated for 48 hours with APP (1 X 10(4) colony-forming units/mL), interleukin-1beta, (IL-1beta; 5 U/mL), tumor necrosis factor-alpha (TNFalpha; 500 U/mL), interferon-gamma (IFN-gamma, 100 U/mL), or lipopolysaccharide (LPS; 10 microg/mL). In a second experiment, alveolar macrophages were incubated with fresh medium (negative control), APP alone, or APP with 1 of the following: IL-1beta, TNF-alpha, or IFN-gamma. In a third experiment, alveolar macrophages were incubated with fresh medium (negative control), LPS (positive control), APP alone, or APP with 1 of the following: an iNOS inhibitor (3.3 microM), a COX-2 inhibitor (10 microM); or both the iNOS and COX-2 inhibitors. Supernatant was obtained at 0, 3, 6, 9, 12, 24, and 48 hours after treatment for determination of NO and PGE2 production. RESULTS: The addition of APP to alveolar macrophages resulted in significant increases in NO and PGE2 production. The addition of APP and IFN-gamma synergistically induced NO production. Inhibition of iNOS and COX-2 decreased NO and PGE2 production, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: In vitro activation of alveolar macrophages by APP results in increased production of NO and PGE2. Nitric oxide and PGE2 production appears to be largely dependent on iNOS and COX-2 activity. Pharmacologic modulation of iNOS and COX-2 activity may represent a therapeutic target for pigs with pleuropneumonia.     

The stimulatory effect of insulin-like growth factor-1 on the proliferation, differentiation, and mineralisation of osteoblastic cells from Holstein cattle

This study investigated the effect of exogenous insulin-like growth factor (IGF)-1 on the proliferation and differentiation of osteoblastic cells from Chinese Holstein cattle and the resultant bone nodule formation and mineralisation in vitro. The osteoblastic cells were isolated and cultured, then identified using Giemsa and alkaline phosphatase (ALP) staining methods. The effect of different concentrations of IGF-1 on cell growth was assessed by MTT assay. The ALP activity and osteocalcin (OC) concentration in the osteoblastic cells were measured by a colorimetric assay and a radioimmmunoassay, respectively. Calcium nodules were observed using alizarin red S stain, while the content of matrix calcium was determined by atomic absorption spectrophotometry. Cell proliferation in the cultures was stimulated by IGF-1 at concentrations ranging from 1 to 200 ng/mL, with the maximum effect observed at 100 ng/mL. This effect was observed from day 1 and peaked at day 5, but decreased at day 7. At concentrations of 10 ng/mL and 100 ng/mL, IGF-1 significantly induced ALP activity, OC level, matrix calcium content, and nodule formation of the osteoblastic cells by 20–180% (P < 0.05 or P < 0.01), compared to controls. The results suggested that IGF-1 is an anabolic agent for the proliferation, differentiation, mineralisation and calcium content of dairy cow osteoblasts, and could therefore act as a potential treatment for the metabolic bone diseases in these animals.     

Effects of carprofen and dexamethasone on canine chondrocytes in a three-dimensional culture model of osteoarthritis

OBJECTIVE: To determine effects of carprofen and dexamethasone on chondrocytes in a culture model of osteoarthritis (OA). SAMPLE POPULATION: Chondrocytes isolated from articular cartilage of the humeral head of 5 adult dogs. PROCEDURE: Chondrocytes were harvested, cultured and subcultured in monolayer, and then cultured in a 3-dimensional (3-D) medium. Cells from each dog were distributed into 6 groups with differing content of liquid medium for each 3-D construct (agarose [AG], AG plus interleukin [IL]-1beta, AG plus carprofen [4 microg/mL], AG plus dexamethasone [1 mg/mL], AG plus IL-1beta [20 ng/mL] plus carprofen [4 microg/mL], and AG plus IL-1beta (20 ng/mL) plus dexamethasone (1 mg/mL). On days 3, 6, 12, and 20 of culture, samples from all groups were collected. Liquid media were assayed for glycosaminoglycan, prostaglandin (PG)E2, matrix metalloprotease (MMP)-3, and MMP-13 concentrations. All 3-D constructs were evaluated for viability, cell morphology, proteoglycan staining, and collagen type-II concentration. Total glycosaminoglycan content in each 3-D construct was quantitated by spectrophotometric assay. RESULTS: Addition of IL-1beta caused a significant loss of cell viability and matrix production. Addition of carprofen or dexamethasone caused significant decreases in PGE2 in the liquid media, and each was minimally effective in protecting chondrocytes against negative effects of IL-1beta. CONCLUSIONS AND CLINICAL RELEVANCE: Human recombinant IL-1beta resulted in loss of cell viability, alterations in extracellular matrix components, and production of PG and MMP Carprofen and dexamethasone had little effect on cell and matrix variables but did decrease PGE2 concentrations and primarily affected the inflammatory pathway of osteoarthritis.     

Effects of insulin-like growth factor-II on the mitogenic and metabolic activities of equine articular cartilage with and without interleukin 1-beta

OBJECTIVE: To investigate the effects of insulin-like growth factor-II (IGF-II) on DNA and glycosaminoglycan (GAG) synthesis and the expression of matrix-related genes in equine articular cartilage explants and chondrocytes, respectively, with and without interleukin 1-beta (IL1-beta). SAMPLE POPULATION: Articular cartilage from 12 adult horses. PROCEDURE: Articular cartilage was incubated in standard media with and without equine IL1-beta (10 ng/mL) containing various concentrations of IGF-II for 72 hours. Synthesis of DNA and GAG was determined by incorporation of thymidine labeled with radioactive hydrogen (3H) and sulfate labeled with radioactive sulfur (35S), respectively. Total GAG content of the explants and spent media was determined by use of the 1,9-dimethylmethylene blue assay. Northern blots of RNA from cultured equine articular cartilage chondrocytes were hybridized with cDNA of major matrix molecules. RESULTS: Insulin-like growth factor-II stimulated DNA and GAG synthesis at concentrations of 25 and 50 ng/mL, respectively. In cartilage explants conditioned with IL1-beta, IGF-II stimulated DNA and GAG synthesis at concentrations of 500 and 50 ng/mL, respectively. Insulin-like growth factor-II had no effect on total GAG content as determined by the 1,9-dimethylmethylene blue assay. No specific effects on steady-state levels of messenger RNAs were observed. CONCLUSIONS AND CLINICAL RELEVANCE: Insulin-like growth factor-II stimulated DNA and GAG synthesis in equine adult cartilage and may have potential application in vivo.     

酶法制备蚕茧层抗氧化多肽水解液的研究

基于利用蚕茧层开发抗氧化剂的目的,采用mu ltifect neutral细菌中性蛋白酶酶解蚕茧层,并用铁离子还原/抗氧化力分析法(FRAP)测定蚕茧层酶解液总抗氧化能力,确定原料预处理的温度和时间;运用正交试验优化酶解条件,比较蚕茧层多肽与丁基甲基苯酚(BHT)和VC的总抗氧化能力。结果表明:蚕茧层在100℃水浴加热2h后,添加质量分数为7.0%的mu ltifect neutral细菌中性蛋白酶,55℃下,pH 6.5、底物质量浓度0.033 3 g/mL、酶解210 m in时的水解物总抗氧化能力最强。     

GDF9对绵羊卵丘细胞增殖的影响

本试验旨在探究生长分化因子9（GDF9）对卵丘细胞扩展相关基因和激素受体基因表达量及激素分泌的影响,为GDF9在绵羊卵泡发育中的作用提供依据。以绵羊卵丘细胞为研究对象,通过在低血清细胞培养液中添加不同浓度（0、50、100、200、400 ng/mL）的GDF9,培养绵羊卵丘细胞48 h后,提取细胞总RNA,利用实时荧光定量PCR技术,以β-actin为内参基因,检测卵丘细胞扩展相关基因透明质酸合酶2（HAS2）、前列腺素内过氧化物合酶2（PTGS2）、穿透素3（PTX3）及激素受体相关基因卵泡刺激素受体（FSHR）、促黄体生成素受体（LHR）和雌激素受体（E₂R）的mRNA相对表达量;利用酶联免疫吸附法（ELISA）测定培养液中卵丘细胞分泌的雌二醇（E₂）和孕酮（P₄）含量。结果显示：在细胞培养液中添加200 ng/mL GDF9时,HAS2、PTX3、FSHR、E₂R和LHR的mRNA相对表达量极显著高于对照组与其他处理组（P<0.01）;PTGS2 mRNA相对表达量极显著高于对照组、50和400 ng/mL GDF9组（P<0.01）,显著高于100 ng/mL GDF9组（P<0.05）。当添加400 ng/mL GDF9时,各基因mRNA相对表达量均极显著低于200 ng/mL GDF9组（P<0.01）;E₂分泌量极显著高于对照组与50 ng/mL GDF9组（P<0.01）,显著高于100 ng/mL GDF9组,与200 ng/mL GDF9组差异不显著（P>0.05）。100、200和400 ng/mL GDF9组P₄分泌量显著高于对照组（P<0.05）,与50 ng/mL GDF9组没有显著差异（P>0.05）,且3组之间差异不显著（P>0.05）。综上所述,GDF9能够促进绵羊卵丘细胞扩展,并参与绵羊卵丘细胞激素分泌的调控。     

Effect of GDF9 on Sheep Cumulus Cell Proliferation

The purpose of this study was to investigate the effect of growth differentiation factor 9 (GDF9) on the gene expression of cumulus cells expansion and hormone receptors as well as hormone secretion,in order to provide evidence for the role of GDF9 in the development of sheep cumulus cells.Sheep cumulus cells were used as the research object in this study,and were cultured for 48 h by adding different concentrations (0,50,100,200,400 ng/mL) GDF9 to low serum cell culture medium.Total RNA were extracted from the cells,using β-actin as the reference gene,Real-time quantitative PCR technology were used to detect the cumulus cells expansion related genes hyaluronic acid synthase gene 2 (HAS2),prostaglandin lead oxide synthase 2 (PTGS2),pentraxin 3 (PTX3) and hormone receptor genes follicle-stimulating hormone receptor (FSHR),luteinizing hormone receptor (LHR) and estrogen receptors (E₂R).Using the enzyme-linked immunosorbent assay (ELISA) method to test the content of E₂ and P₄.The results showed that HAS2,PTX3,FSHR,E₂R and LHR mRNA relative expression of 200 ng/mL GDF9 group was extremely significantly higher than the control group and other GDF9 groups (P<0.01),PTGS2 mRNA relative expression was extremely significantly higher than the control group and 50,400 ng/mL GDF9 groups (P<0.01),and significantly higher than 100 ng/mL GDF9 group (P<0.05).When added 400 ng/mL GDF9,the relative mRNA expression of all the mentioned-above genes were all extremely significantly lower than that of the 200 ng/mL GDF9 group.Moreover,the E₂ secretion level was extremely significantly higher than that of the control group and 50 ng/mL GDF9 group (P<0.01),significantly higher than that of the 100 ng/mL GDF9 group(P<0.05),while had no significant difference from the 200 ng/mL GDF9 group (P>0.05).When added 100,200 and 400 ng/mL GDF9,the concentration of P₄ was significantly higher than the control group (P<0.05),and there was no significant difference from the 50 ng/mL group (P>0.05),and there was no significant difference between 100,200 and 400 ng/mL GDF9 groups (P>0.05).To sum up,GDF9 could promote the expansion of sheep cumulus cells and participated in the regulation of hormone secretion of sheep cumulus cells.     

Assessment of pregnancy‐associated glycoprotein (PAG) concentrations in swamp buffalo samples from fetal and maternal origins by using interspecies antisera

Pregnancy‐associated glycoproteins (PAG) constitute a large family of glycoproteins found in the outer placental epithelial cell layer of the placenta in Eutherian species. In ruminants, they are noted to be structurally closely related among the different species. This study was designed to determine PAG concentrations in maternal and fetal plasma, allantoic and amniotic fluids in buffalo species. Antisera (AS) generated in rabbits against distinct PAG molecules were used in three radioimmunoassay (RIA)‐PAG systems: RIA‐1 (antiserum raised against bovine PAG67kDa; AS#497), RIA‐2 (antiserum raised against caprine PAG55 + 62 kDa; AS#706) or RIA‐3 (antiserum raised against buffalo PAG; AS#859). Samples were collected at a slaughterhouse (n = 67). PAG concentrations determined by RIA‐2 gave significantly higher results in both allantoic and amniotic fluids (12.7 ± 2.1 ng/mL and 24.0 ± 7.3 ng/mL, respectively). Regarding maternal and fetal plasma, PAG concentrations obtained by RIA‐2 (21.8 ± 2.4 ng/mL and 20.2 ± 2.5 ng/mL, respectively) and RIA‐3 (25.0 ± 2.2 ng/mL and 21.9 ± 3.2 ng/mL, respectively) were higher than those obtained by RIA‐1 (15.5 ± 1.4 ng/mL and 16.1 ± 1.8 ng/mL, respectively). The correlation among the three systems was very high. The study clearly reveals the ability of different PAG‐RIA systems to measure PAG concentration in swamp buffalo samples.     

Urinary biomarkers to assess exposure of cats to environmental tobacco smoke

OBJECTIVE: To evaluate the use of urinary biomarkers to assess exposure of cats to environmental tobacco smoke (ETS). ANIMALS: 61 healthy client-owned cats (19 from households in which smoking was reported and 42 from households in which there was no smoking). PROCEDURES: Urine samples were obtained from each cat and assayed for total nicotine (nicotine plus nicotine glucuronide) and total cotinine (cotinine plus cotinine glucuronide) content by use of gas chromatography-mass spectrometry. In addition, total urinary content of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), a major metabolite of the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, was measured by use of gas chromatography with nitrosamine-selective detection. RESULTS: Cats from households in which smoking was reported had significantly higher concentrations of total nicotine (70.4 ng/mL), total cotinine (8.53 ng/mL), and total NNAL (0.0562 pmol/mL) in urine, compared with concentrations for cats that lived in households in which there was no smoking (4.89 ng/mL, 0.74 ng/mL, and 0.0182 pmol/mL, respectively). CONCLUSIONS AND CLINICAL RELEVANCE: Analysis of these data provided biochemical evidence of exposure to ETS and uptake of tobacco-specific carcinogens by cats that live in households with smokers. Biomarkers could facilitate investigation of the health effects of ETS in cats and other species.     

Effect of hypothyroidism on the blood lipid response to higher dietary fat intake in mares

Blood lipid and lipoprotein concentrations were measured and compared between euthyroid and thyroidectomized mares on low-fat or high-fat diets to test the hypothesis that hypothyroidism alters the blood lipid response to higher dietary fat intake. Four healthy adult mares and four adult mares that had been thyroidectomized 3 to 6 mo earlier were placed on low-fat or high-fat diets according to a replicated 2 x 2 Latin square design consisting of two 5-wk feeding periods separated by a 2-wk washout interval. Plasma lipid concentrations were measured at 0, 3, 4, and 5 wk, and plasma lipase activities were measured at the end of each 5-wk feeding period. Compared with euthyroid mares (0.46 ng/mL [range 0.34 to 0.68 ng/mL T3], and 21.5 ng/mL [range 18.1 to 25.1 ng/mL T4], respectively), median serum concentrations of T3 and T4 were lower (P = 0.029 and P = 0.021, respectively) in thyroid-ectomized mares (0.26 ng/mL [range 0.23 to 0.26 ng/ mL T3], and undetectable T4). Serum T4 concentrations were below the limits of detection in thyroidectomized horses. Alterations in body weight over 5 wk did not differ between groups. Mean plasma very low density lipoprotein (VLDL) and triglyceride (TG) concentrations were higher (P = 0.045 and 0.034, respectively) in hypothyroid mares (55.42 +/- 35.05 mg/dL and 52.83 +/- 34.46 mg/dL, respectively) compared with euthyroid mares (28.28 +/- 13.76 mg/dL and 23.53 +/- 9.84 mg/dL, respectively). Mean plasma total cholesterol (TC) concentrations increased from 88.73 +/- 25.49 mg/dL at baseline to 103.93 +/- 24.42 mg/dL after 5 wk on the low-fat diet, but increased by a greater magnitude (P = 0.006 diet +/- time interaction) in mares that were on the high-fat diet (81.05 +/- 17.24 mg/dL and 123.84 +/- 32.27 mg/ dL, respectively). Mean plasma TC concentrations were higher (P = 0.099) in hypothyroid mares (116.16 +/- 32.89 mg/dL) than in euthyroid mares (89.56 +/- 14.45 mg/ dL). Higher post-heparin plasma lipoprotein lipase and hepatic lipase activities (P = 0.012 andP = 0.017, respectively) were detected in mares that were on the high-fat diet (2.66 +/- 0.91 micromol FA x mL(-1) x h(-1) and 2.95 +/- 0.49 micromol FA x mL(-1) x h(-1), respectively) vs. a low-fat diet (1.75 +/- 0.55 micromol FA x mL(-1) x h(-1) and 2.27 +/- 0.59 micromol FA x mL(-1) x h(-1), respectively). We conclude that plasma VLDL and TG concentrations are elevated in hypothyroid mares, but the blood lipid response to higher dietary fat intake is not influenced by hypothyroidism.