Carcass and muscle characteristics of Yorkshire, Meishan, Yorkshire x Meishan, Meishan x Yorkshire, Fengjing x Yorkshire, and Minzhu x Yorkshire pigs

Transcriptome-Wide lncRNA and mRNA Profiling of Spleens from Meishan Pigs at Different Development Stages

Simple Summary

Meishan pig is a local pig breed in China, which has higher immunity than commercial pig breeds for some diseases. The spleen has hematopoietic and immune response functions, making it a good organ model for studying immunity. We depicted the expression profiles of lncRNA-mRNA in the spleen of Meishan pigs at different developmental time points (7 d, 21 d, 35 d, 120 d and 180 d). In addition, we found that AKT3, CBL and PTK2B may be involved in immune regulation in Meishan pigs through a competing endogenous RNA network. This result provides valuable genomic resources for studying immune regulation in animals and finds potential molecular markers for pig disease resistance breeding.

Abstract

Meishan is a well-established local Chinese breed known for its high fecundity, strong immune response and high meat quality. However, the molecular mechanism of immune regulation during the development of Meishan pigs still remains unclear. Here, we performed the transcriptional sequencing of spleen tissues from Meishan pigs at different development stages. In total, 10,268 lncRNAs were identified, including 1254 novel lncRNAs and 9014 known lncRNAs. Time series analysis revealed that genes of the up-regulated module were enriched in pathways associated with transport, immunity, and histone acetylation modifications, while genes of the down-regulated module were enriched in DNA metabolic process and cell cycle. Weighted gene co-expression network analysis (WGCNA) showed the functional linkage between mRNAs and lncRNAs, indicating that lncRNAs are important regulatory elements of mRNAs. Notably, a lncRNA-miRNA-mRNA competing endogenous RNA (ceRNA) network that contained 3 mRNAs (AKT3, CBL and PTK2B), 17 lncRNAs and 67 miRNAs were screened out, which probably plays a critical role in immune regulation of Meishan pigs. Our findings not only revealed the transcriptome profile of spleen development, but also provide novel insights into the mechanism of lncRNA-miRNA-mRNA axis in the immune response in Meishan pigs.

SINE Insertion May Act as a Repressor to Affect the Expression of Pig LEPROT and Growth Traits

Retrotransposon is an important component of the mammalian genome. Previous studies have shown that the expression of protein-coding genes was affected by the insertion of retrotransposon into the proximal genes, and the phenotype variations would be related to the retrotransposon insertion polymorphisms (RIPs). In this study, leptin (LEP), leptin receptor (LEPR), and leptin receptor overlapping transcript (LEPROT), which play important roles in the regulation of fat synthesis and body weight, were screened to search for the RIPs and their effect on phenotype and gene expression, as well as to further study the function of the insertion. The results showed that three RIPs located in intron 1 of LEPROT and intron 2 and 21 of LEPR were identified, and they were all SINEA1, which was one type of retrotransposon. The SINE insertion at the LEPROT was the dominant allele in native pig breeds. The age of 100 kg body weight of SINE+/+ Large White individuals was significantly higher than those of SINE+/− and SINE−/− individuals (p < 0.05). The LEPROT gene expression in the liver and suet of 30-day-old SINE−/− Sujiang piglets were significantly higher than those of SINE+/+ and SINE+/− piglets (p < 0.01). The dual-luciferase reporter gene assay showed that SINE insertion in PK15 and 3T3-L1 cells significantly reduced the promoter activity of the LEPROT gene (p < 0.01). Therefore, SINE insertion can be a repressor to reduce the expression of LEPROT and could be a useful molecular marker for assisted selection of growth traits in pig breeding.

Comparison of growth performances, carcass characteristics, and meat qualities of Okinawan indigenous Agu pigs and crossbred pigs sired by Agu or Duroc boar

Indigenous Okinawa Agu pigs are crossed with Large White × Landrace (WL) pigs to improve their meat production, but there is little information regarding the crossbreeding effects. The study aims to compare growth, carcass characteristics, and meat qualities of Agu pigs with those of WL crossbreeds with Agu sires (WLA) or Duroc sires (WLD). WLA pigs showed better growth performance and carcass characteristics and less intramuscular fat (IMF) contents than Agu ones, but they had higher fat deposition, smaller longissimus dorsi muscle area, and higher IMF contents than WLD pigs. Agu pigs showed higher water holding capacity than the other two breeds. The inner layer of Agu backfat contains higher and lower proportions of monounsaturated fatty acids (MUFA) and polyunsaturated fatty acid (PUFA), respectively, than that in WLD animals. WLA animals had intermediate values for the fatty acid content in the inner backfat, although MUFA contents were equal to those of Agu pigs. Fatty acid profiles in IMF were similar to those in the backfat. These results indicate that crossbreeding of Agu with WL pigs improves growth performance and carcass quality. Particularly, WLA pigs have higher IMF contents and MUFA concentrations and lower PUFA concentrations than WLD pigs.

Effect of MSTN Mutation on Growth and Carcass Performance in Duroc x Meishan Hybrid Population

Simple Summary

Myostatin (MSTN) is a transcriptional growth factor that inhibits the development and growth of skeletal muscle. The MSTN-deficient animals display an increase in skeletal muscle mass known as double-muscling. Therefore, MSTN becomes an important target for improving lean meat production in livestock husbandry. There are many local pig breeds in China, but because of the slow growth, poor feed conversion, and low lean meat percentage and other unsatisfactory qualities, pure local breeds are rarely used on commercial farms. The objective of this study is to evaluate the effects of MSTN single allele mutation on carcass composition in Meishan crossbred pigs and demonstrate a way to increase lean meat yield while maintaining prolificacy and good meat quality of local pig crossbreeds. This has significant implications for the widespread use and conservation of local pig breeds in China.

Abstract

The Meishan pig is a traditional Chinese native breed, known for its excellent reproduction performance that is widely used in commercial pig production through two-way or three-way crossbreeding systems. However, the lean meat yield of Meishan crossbred pigs is still very low and cannot meet the market demand. To evaluate the lean meat yield of Meishan crossbred pigs, six wild-type Meishan sows were artificially inseminated by using the MSTN^+/− Duroc boar semen in this experiment. Some reproductive performance-related traits of Meishan sows were recorded to ensure that semen from MSTN knockout Duroc boar did not affect offspring production, including total births, live births, sex, and litter weight. In total, 73 piglets were obtained and 63 were alive. Male to female ratio was close to 1: 1. because of factors such as disease, only 43 pigs were utilized, including 28 MSTN mutant pigs (MSTN^+/−) and 15 MSTN homozygous pigs (MSTN^+/+). We compared the growth performance and carcass performance of these full or half-sib populations and found that there were no differences between MSTN^+/− and MSTN^+/+ genotypes for live animal measures including average daily gain (ADG), body dimensions, or ultrasonic measurement of fat thickness when pigs were harvested after 120 days of feeding. Conversely, the MSTN^+/− pigs had higher dressing percentage and lean meat percentage, lower level of carcass fat, larger longissimus muscle area, less percentage of skin and skeleton, thinner average backfat thickness, and lower intramuscular fat (IMF) content than MSTN^+/+ pigs. In conclusion, the production of MSTN^+/− mutant progeny from Meishan females resulted in improved carcass composition, providing a feasible solution to improve the lean meat yield of Chinese local fat-type pig breeds.

Evaluation of the four breeds in synthetic line of Jiaxing Black Pigs and Berkshire for meat quality traits, carcass characteristics, and flavor substances

To investigate breed characteristics and the effect of hybridization of Jiaxing Black Pig (JBP) with Western breeds, the carcass and meat quality traits and flavor substances such as inosinic acids (IMP), intramuscular fat (IMF) in longissimus muscle (LM) from five breeds including JBP, Berkshire, Berkshire × JBP (BJBP), Duroc × Berkshire × JBP (DBJBP), Duroc × Landrace × JBP (DLJBP) were compared in this study. It was found that water holding capacity (WHC) of LM in JBP was significantly higher than that in the other strains (p < 0.01). Dressing out percentage and lean percentage of JBP were both significantly lower than those in the others (p < 0.01) in connection with their lighter carcass weight and higher subcutaneous fat percentage (p < 0.01). Heterosis was realized in DJBP, DBJBP, and DLJBP since their carcass weight, lean percentage, and loin eye muscle area (LEMA) were markedly higher when compared to JBP, whereas lower than those in Berkshire. Among the breeds, the content of IMF and IMP in the LM of JBP were the highest. These traits were also palpably improved in the crossbreds, especially for DBJBP, of which pork was considered outstanding for containing the most abundant essential amino acids (EAA) and total amino acids (TAA).

Growth, carcass characteristics and meat quality of Chinese indigenous Yanan pig crossbred with Duroc and Berkshire genotypes

The objective of the present study was to evaluate the effects of crossbreeding on the growth, carcass characteristics and meat quality of Chinese native Yanan (YN) pig breed and related crossbreeds, including Duroc × Yanan (DY) and Duroc × (Berkshire × Yanan) (DBY). In total, 60 pigs (20 per breed) were used in the study. The results showed that both crossbreeds, especially DBY pigs, exhibited improved growth and carcass characteristics compared with those of purebred YN pigs. Moreover, the two crossbreeds, especially DBY pigs, produced acceptable meat-quality characteristics (normal pH and meat-colour values, high intramuscular fat content and water-holding capacity, acceptable muscle-fibre parameters, and strong pork flavour) similar to those of YN pigs. M. longissimus lumborum contained eight essential amino acids, with high contents in all pigs. C18:1, C16:0, C18:0, and C18:2 were the main fatty acids in M. longissimus lumborum in the three breeds, and a polyunsaturated:saturated fatty acid ratio of ~0.2 was observed in DBY and YN pigs. These results indicated that DBY pigs exhibit an acceptable total production performance and could be extensively used in commercial pig production to provide high-quality niche products.

Differences in calpain system, desmin degradation and water holding capacity between commercial Meishan and Duroc × Landrace × Yorkshire crossbred pork

The objective of this study was to examine the differences in calpain system, desmin degradation, pH values and water holding capacity (WHC) between muscles of commercial Meishan and Duroc × Landrace × Yorkshire crossbred pigs. Meishan pork presented better WHC evidenced by lower purge loss at days 1 and 3 and less centrifugation loss at day 1 post mortem (P < 0.05). pH values at 45 min post mortem in Meishan pork were significantly higher compared to crossbred pork (P < 0.05). Calpain-1 messenger RNA (mRNA) expression was lower in Meishan pork compared to that from crossbred pork (P < 0.05). Additionally, calpain-1 activity, the ratio of calpain-1 to calpastatin activity and desmin degradation were lower in Meishan pork compared to those from crossbred pork samples (P < 0.05). The results indicate that the calpain system including mRNA expression and activity were different between commercial Meishan and crossbred pork resulting in difference in the degree of desmin degradation during post mortem aging. pH values at 45 min and 24 h post mortem rather than calpain activity and desmin degradation could explain the higher water holding capacity in commercial Meishan pork.

Impact of genetic drift on access and benefit sharing under the Nagoya Protocol: the case of the Meishan pig

Genetic drift (GD) randomly impacts small breeds and imported populations. Therefore, it can impact policies that affect conservation of animal genetic resources. This paper evaluates GD for a population of Meishan pigs imported into the United States and explores the ramifications of GD on access and benefit sharing of genetic resources under the Nagoya Protocol (NP) of the United Nations' Convention on Biological Diversity. The NP was motivated by concerns about fair and equitable benefit sharing of genetic resources across life forms. In this experiment, 35 microsatellite markers were used to quantify the level of GD that occurred between Meishan pigs (Meishan-China; n = 22) imported into the United States in the late 1980s and contemporary Meishan (Meishan-US; n = 42), which have been randomly bred since importation. The Meishan-US consisted of 2 subpopulations (Meishan-MARC and Meishan-ISU). Five other breeds were also included in the analysis to serve as reference populations: Fengjing and Minzhu, which were imported with Meishan-China, and Duroc, Berkshire, and Yorkshire from the United States. Mean shift in allele frequency was 0.11 (SE = 0.019) due to GD for Meishan-US vs. Meishan-China with some loci having changed allele frequencies by greater than 0.20. Principle coordinate analysis confirmed divergence among the Meishan populations. Model-based clustering tended to place the U.S. and Chinese breeds into 2 distinct clusters, likely due to differences in allele frequencies between U.S. and Chinese breeds. Contemporary Meishan-US has become differentiated from the original imported animals due to GD. Attributing future performance of Meishan-US to Meishan-China, as set forth by NP, is problematic due to GD. As an imported breed becomes established there will be an increasing number of breeders who may have different selection goals and private treaty contracts will govern the exchange of stock between them. Therefore, considering biological phenomena and social dynamics simultaneously draws into question whether a rigorous access and benefit sharing protocol as envisioned in the NP will be operational.

Influence of on-farm production practices on sensory and technological quality characteristics of pork loin

Quality of pork from pigs raised either traditionally (outdoor access or bedded settings with no sub-therapeutic antibiotics or growth promotants in feed) or conventionally (commercial indoor) was evaluated. Pork loins (m. longissimus thoracis et lumborum, LTL) from four hundred pigs from either traditional or conventional production systems (n=200) fed commercially formulated diets ad libitum were harvested at slaughter. Intramuscular crude fat content and lean color (L* and b*) values were significantly decreased in conventional pork loins. LTL from conventionally-raised pig carcasses showed increased (P<0.05) mean pH, moisture content and reduced cooking loss and shear force values and had increased tenderness and juiciness scores compared to those from traditionally-raised pig carcasses. Results indicated that pork from conventionally raised pigs was superior to that from traditionally raised pigs in terms of tenderness and juiciness, suggesting that consumers may value pork from traditionally raised pigs on the basis of factors other than eating quality and appearance.

Carcass and meat quality traits of four commercial pig crossbreeds in China

We evaluated carcass and meat quality traits of two Chinese native crossbreeds Landrace x Meishan (LM) and Duroc x (Landrace x Meishan) (DLM) and two foreign crossbreeds Duroc x (Landrace x Yorkshire) (DLY) and PIC (an imported five-way crossbreed). One hundred and twenty weaned pigs (half castrated males and half females) were reared and slaughtered at a predestinated slaughter age. The general carcass and meat quality traits were measured and analyzed. The DLY and PIC crosses had significantly heavier live weights (93.39 and 96.33 kg, P < 0.01), significantly higher dressing percentages (80.65 and 79.39%, P < 0.05), significantly bigger loin areas (42.69 and 43.91 cm(2), P < 0.001), and significantly more lean carcasses (65.78 and 66.40%, P < 0.001) than LM and DLM. On the other hand, LM had a significantly lower live weight (70.29 kg, P < 0.01), significantly thicker back fat (3.54 cm, P < 0.001), significantly less lean carcasses (46.82%, P < 0.001), and significantly less ham and breech (26.53%, P < 0.05) than the other crossbreeds. Among meat quality parameters, LM had the highest intramuscular fat content (5.02%, P < 0.001) and the smallest fiber area (3126.45 μm(2), P < 0.01). However, PIC showed the lowest pH(1) (5.82, P < 0.01) and pH(2) (5.63, P < 0.01), the highest drip loss (2.89%, P < 0.01), and the lowest intramuscular fat (1.35%, P < 0.001). We concluded that LM and DLM had good meat quality traits but poorer carcass traits than DLY and PIC; DLY had good carcass and meat quality traits; PIC had good carcass traits, but it had less intramuscular fat, lower pH and higher drip loss.

The eating quality of pork from Meishan and Large White pigs and their reciprocal crosses

Two studies, one using a trained taste panel and the other a consumer panel, were carried out to evaluate the eating quality of the Meishan breed. Entire male and female pigs of four genotypes: purebred Meishan (MS) and Large Wliite (LW) and the reciprocal crosses (MS♂ × LW ♀ and LW♂ × MS♀) were reared in single sex groups and given a commercial diet ad libitum from 35 kg live weight to slaughter at around 70 kg. For the taste panel, a loin joint was roasted under standard conditions and samples of fat and lean were presented to the panellists. There were no statistically significant differences between the genotypes for tenderness, juiciness, flavour, odour, incidence of boar taint or overall acceptability. Purebred Meishan samples had a higher incidence of abnormal odours but lower cooking losses and shear force values than the other three genotypes. Meat from gilts was judged to be significantly more tender and juicy, with a weaker pork flavour but a lower incidence of abnormal flavours and higher overall acceptability than that from boars. There were statistically significant interactions between genotype and sex for tenderness, abnormal odour and shear force which mainly involved the purebred Meishans and were of little practical significance. In the consumer study, loin chops and leg joints from purebred LW and the two crossbred genotypes were evaluated. Households received two samples of the same type of joint from the same sex in two separate distributions. Each household received an LW sample and a sample from one of the crossbred genotypes. In general, consumers found the appearance of the joints from the three genotypes to be equally acceptable. For eating quality, the within-household deviations of the crossbred compared with the LW suggested that MS♂ × LW♀ samples were considered to be of better eating quality, particularly for juiciness (deviation -0·71, s.e. 0·24, P < 0·01). In contrast, LW♂ × MS♀ samples were generally considered inferior, particularly in terms of juiciness (+ 0·59, s.e. 0·26, P < 0·05) and flavour (+0·63, s.e. 0·27, P < 0·05). However, the overall acceptability of both crossbreds was considered little different from the Large White. Overall, the results of this work suggest little benefit in eating quality for the Meishan under United Kingdom production conditions.

The effect of energy supply on the contribution of lean tissue to total body protein mass in pigs slaughtered at 100 kg

The effect of energy supply between 45 and 100 kg body weight (BW) on the contribution of lean tissue (muscle plus intermuscular adipose tissue) to total protein mass was studied in Large White castrated males (cLW), crossbred Piétrain × Large White castrated males (cPPx) and boars (bPPx). The pigs were allocated to four energy levels (0·70, 0·80, 0·90 or 1·00 ad libitum) and kept in metabolism cages in experiment 1 or given food ad libitum and kept in individual pens in experiment 2. Daily protein supplies were calculated to be non-limiting for growth and identical for all pigs in experiment 1. Temperature was 23°C in both experiments. The pigs were slaughtered at 100 kg BW and physically dissected; the body tissues were chemically analysed. Taking into account housing conditions, the food intake of pigs in experiment 2 corresponded to 1·20 of ad libitum intake of pigs in experiment 1; data of both experiments were combined. The energy supply and the type of pig influenced significantly the protein content of empty BW (eBW) (170 g/kg on average), of lean (184g/kg on average) and non-lean compartment (eBW minus lean, 152 g/kg on average), the proportion of total protein deposited in lean (604 g/kg of total protein, on average) but not the protein content in fat-free eBW (209 g/kg on average). The fat-free eBW can be predicted as 4·8 times the body protein mass.

Correlations of trained panel sensory values of cooked pork with fatty acid composition, muscle fiber type, and pork quality characteristics in Berkshire pigs

The objective was to examine the relationship of trained panel sensory scores of cooked pork with fatty acid composition, muscle fiber type, and meat quality characteristics from Berkshire pigs. No or few associations were found between the panel sensory scores of cooked meat, especially tenderness attributes, and fatty acid composition; however, intramuscular fat content positively correlated with off-flavor score (r=0.31). On the other hand, the morphological characteristics of muscle fibers were correlated with panel sensory values. Muscles with smaller cross-sectional area and higher density of fibers were more closely associated with softer, more tender panel scores and a lower number of chews than muscles with larger fiber area and lower density of fibers. The water holding capacity test of filter-paper fluid uptake was moderately correlated with panel scores of softness (r=0.33), initial tenderness (r=0.38), chewiness (r=0.40), juiciness (r=-0.27), flavor intensity (r=-0.23), and off-flavor (r=0.30). Panel sensory values of Berkshire pig meat was moderately related to postmortem meat quality, especially water holding capacity. A more thorough understanding of the relationships between fatty acid composition and muscle fiber type with palatability is needed.

Effect of different Duroc line sires on carcass composition, meat quality and dry-cured ham acceptability

Carcasses of 399 malignant hyperthermia gene free pigs from crosses sired by three types of Duroc (Virgen de la Fuente, DU1; Diputación de Teruel, DU2; DanBred, DU3) were analyzed for carcass and meat quality. Carcass leanness and fat parameters were measured at the last rib and at the space between the 3rd and 4th last ribs counting from the last one. Weights, pH, electrical conductivity, colour and intramuscular fat were also measured. A sample of 133 legs per cross were processed by dry-curing. The ham portion including Biceps femoris, Semimembranosus and Semitendinosus muscles was evaluated for instrumental texture and colour, biochemical and sensory analyses and acceptability (trained panel and consumers). DU3 carcasses were well conformed but lean. DU1 carcasses had a lower conformation but higher marbling. DU2 carcasses were intermediate. Dry-cured hams from DU1-sired pigs had a higher overall acceptability, although fat content influenced a consumers group negatively. Leaner DU3 hams had the lowest acceptability.

Interval mapping of carcass and meat quality traits in a divergent swine cross

An autosomal scan of the swine genome with 119 polymorphic microsatellite (ms) markers and data from 116 F2 barrows of the University of Illinois Meishan x Yorkshire Swine Resource Families identified genomic regions with effects on variance in carcass composition and meat quality at nominal significance (p-value <0.05). Marker intervals on chromosomes 1, 6, 7, 8 and 12 (SSC1, SSC6, SSC7, SSC8, SSC12) with phenotypic effects on carcass length, 10th rib backfat thickness, average backfat thickness, leaf fat, loin eye area and intramuscular fat content confirm QTL effects identified previously based on genome wide significance (p-value <0.05). Several marker intervals included nominally significant (p-value <0.05) dominance effects on leaf fat, 10th rib backfat thickness, loin eye area, muscle pH and intramuscular fat content.

Influence of intramuscular fat content on lipid composition, sensory qualities and consumer acceptability of cured cooked ham

The present study is part of a project which aims to examine the influence of intramuscular fat (IMF) content on the sensory attributes and consumer acceptability of pork. An experiment was conducted to evaluate the influence of IMF level in muscle semimembranosus (SM) on the composition of its lipid fraction and on the sensory qualities and consumer acceptability of cured cooked hams. Thirty-two carcasses were selected 24 h after slaughter from 125 Duroc × Landrace castrated male pigs showing large variability in SM muscle IMF content and were assigned to four IMF groups: ≤2%, 2-3%, 3-4% and >4%. Cured cooked ham slices were evaluated by a trained expert panel of 12 members and by a group of 56 consumers. Results from lipid analyses indicate that (i) an increase in IMF content was almost entirely reflected by an increase in the triglyceride content of the muscle and (ii) higher IMF levels were associated with higher free fatty acid and monoglyceride and lower cholesterol levels. The sensory evaluation of marbling significantly increased with IMF level, whereas other sensory qualities were unaffected. High IMF levels significantly depreciated the consumer perception of fat, aspect, taste and smell of ham slices. Overall, slices with the highest IMF levels got the least favourable rating by consumers. The present study indicates that increased IMF levels in muscle semimembranosus do not have significant effects on the sensory attributes of cured cooked hams, apart from the perception of marbling. However, high IMF levels have detrimental effects on the acceptability by consumers. © 2000 Society of Chemical Industry.

A surgical model for determination of true absorption and biliary excretion of manganese in conscious swine fed commercial diets

Some trace elements, such as Mn, Cu and Zn, are absorbed and quickly resecreted into the gut through the bile. When this occurs, the unabsorbed nutrient and the absorbed and resecreted nutrient may mix in the gut, preventing quantitative calculation of either. We have developed a surgical model that prevents this complication. Pigs (20-40 kg) were fitted with cannulas in the bile duct, lumen of the duodenum, portal vein, ileocolic vein and jugular vein. After recovery for 6-8 d, pigs were given an oral dose of 9.25 mBq of 54Mn. The flow rate of blood past the portal vein was determined by infusion of P-amino hippuric acid into the ileocolic vein. Absorption was quantified by multiplying the concentration of 54Mn in the portal blood by the flow rate. Biliary excretion was determined by quantitative collection of bile, and previously collected bile was reinfused into the gut lumen. Urine and feces were also quantitatively collected. A postoperative time of 6-8 d was sufficient for pigs to recover from the effects of surgery and anesthesia, as assessed by several measures of metabolic function and food and water intake. True absorption was calculated to be 0.5%. 54Mn in the urine and bile began to increase after 4 d. When the pigs were killed after 12 d, only 0.5% of the 54Mn remained in the carcass. Results of this study show that pigs surgically modified by the described procedure can recover fully and can serve as a model to study intestinal absorption and biliary excretion of nutrients. Furthermore, initial studies using 54Mn showed that the model is applicable to studying Mn metabolism and suggest the need for a more detailed study of Mn absorption and biliary excretion.

Cocaine-induced microvascular vasoconstriction but differential systemic haemodynamic responses in Yucatan versus Yorkshire varieties of swine

1. Systemic and coronary haemodynamics were measured in 6 Yorkshire swine and 6 Yucatan miniature swine under isoflurane anaesthesia to investigate the influence of cocaine following its intravenous administration at 1, 3 and 7 mg kg-1. 2. Cocaine in Yorkshire swine decreased mean arterial pressure and rate pressure product (systolic pressure x heart rate), suggesting a cardiac depressant effect, whereas cocaine in Yucatan miniature swine increased these parameters, consistent with a hyperadrenergic state. 3. Cocaine in both Yorkshire swine and Yucatan miniature swine decreased coronary blood flow and coronary flow reserve, and increased coronary vascular resistance. 4. A modest generalized epicardial coronary artery constriction was observed by angiography, without evidence of focal spasm. 5. Our results confirm a marked vasoconstrictor effect of cocaine on the coronary arterial circulation, predominantly distal to the epicardial coronary arteries, but also indicate important differences in the systemic cardiovascular responses to the drug between two closely related strains of animals within the same species. Due to the similarities between the swine and human coronary arterial vasculature, we suggest that vasoconstriction in the coronary microcirculation may produce cardiac toxicity in man.