Cardiovascular performance of adult breeding sows fails to obey allometric scaling laws

A high-throughput study of visceral organs in CT-scanned pigs

It has been debated whether intensive selection for growth and carcass yield in pig breeding programmes can affect the size of internal organs, and thereby reduce the animal’s ability to handle stress and increase the risk of sudden deaths. To explore the respiratory and circulatory system in pigs, a deep learning based computational pipeline was built to extract the size of lungs and hearts from CT-scan images. This pipeline was applied on CT images from 11,000 boar selection candidates acquired during the last decade. Further, heart and lung volumes were analysed genetically and correlated with production traits. Both heart and lung volumes were heritable, with h² estimated to 0.35 and 0.34, respectively, in Landrace, and 0.28 and 0.4 in Duroc. Both volumes were positively correlated with lean meat percentage, and lung volume was negatively genetically correlated with growth (r_g = − 0.48 ± 0.07 for Landrace and r_g = − 0.44 ± 0.07 for Duroc). The main findings suggest that the current pig breeding programs could, as an indirect response to selection, affect the size of hearts- and lungs. The presented methods can be used to monitor the development of internal organs in the future.

Embryonic and fetal development of the collared peccary (Pecari tajacu)

The relative timing of the main fetal development events in species determine the extent of fetal development at birth, which range along a gradient of having altricial and precocial traits. The results from this study allow for description of important fetal developments in collared peccary (Pecari tajacu) using data from 118 embryo/fetuses from 68 pregnant peccaries obtained over a period of 15 years through collaborative methods with local hunters in the Amazon. The chronological order of emergence of external characteristics in relation to the total dorsal length (TDL) was: differentiated genitalia, limbs and eyelid buds (TDL ≥ 4.5 cm), fusioned eyelids and outer ear (TDL ≥ 5.6 cm), dorsal gland (TDL ≥ 7.3 cm), skin (TDL ≥ 9.2 cm), tactile pelage (TDL ≥ 12.9 cm), coverage pelage (TDL ≥ 17.0 cm), opened eyelids (TDL ≥ 21.5 cm) and tooth eruption (TDL ≥ 24.5 cm). The formula of fetal age was ∛W = 0.079 (t - 27.6), with a linear relationship between TDL and gestational age. The relative weight of tubular gastrointestinal organs, lungs, spleen and thymus increased during fetal development. In contrast, the relative weight of kidneys and liver consistently decreased during the fetal development period. Results of this study indicate the collared peccary is a precocial species and that changes during fetal development are very similar to those in other Suiform species.

Embryonic and fetal development of the white-lipped peccary (Tayassu pecari)

The white-lipped peccary (Tayassu pecari) is an endangered large-sized Neotropical ungulate that is one of the most hunted mammals in the Amazon. Here, we used two embryos and 102 white-lipped peccary fetuses originated from animals hunted for subsistence in the Peruvian and Brazilian Amazon to describe the intrauterine development of external and internal morphology of this Neotropical ungulate. Logistic regressions were used to estimate the probability of occurrence of main external characteristics in relation to the total dorsal length (TDL), while multiple linear and non-linear regressions were conducted to assess the relationship between external and visceral biometry with TDL. External characteristics appeared in the following chronological order: limbs, differentiated genitalia and opened eyelids (≥5.1 cm TDL), fused eyelids (≥6.2 cm TDL), hooves and outer ear (≥7.9 cm TDL), dorsal gland (≥9.4 cm TDL), skin (≥11.5 cm TDL); tactile pelage (≥13.8 cm TDL), covering pelage (≥20.9 cm TDL), tooth eruption (≥26.4 cm TDL) and opened eyelids (≥27.8 cm TDL). The formula of fetal age was ∛W = 0.084 (t - 31.80), with a high linear relationship between TDL and gestational age. All external biometric parameters and absolute volume of visceral organs showed strong positive relationship with TDL. Except for the liver, we found differences in the relative volume of most visceral organs between advanced fetuses (≥34.2 cm TDL) and adults. The most important events during the intrauterine development in the white-lipped peccary show that, in contrast with the domestic pig, it is a highly precocial species producing newborns with a high fetal growth velocity which allows newborns to achieve an early autonomous functionality. Our results are relevant to improve imaging techniques and assist the reproductive and clinical management for the white-lipped peccary both in captivity and in the wild.

Cardiovascular Function of Modern Pigs Does not Comply with Allometric Scaling Laws

Growing concerns have been expressed regarding cardiovascular performance in modern farm pigs, which has been proposed as a critical factor contributing to the reduced adaptability of modern pigs to stress. Here we tested the hypothesis that cardiac dimensions and pump function in modern heavy farm pigs are disproportionally low for their body weight, and investigated potential underlying mechanisms. The results from the present study indeed demonstrate disproportionally low values for stroke volume and cardiac output in pigs with bodyweights over 150 kg. Importantly, these low values were not the result of impaired left ventricular (LV) systolic contractile function, but were due to a disproportionally small LV end-diastolic volume. The latter was associated with changes in determinants of LV passive stiffness, including (i) an increase in LV myocardial collagen, (ii) a shift from the compliant N2BA titin isoform towards the stiff N2B, and (iii) a marked elevation of aortic blood pressure. Taken together, these results demonstrate reduced pumping capacity of the hearts of heavy modern pigs, due to structural abnormalities in the LV myocardium.

Familial hypercholesterolemia impairs exercise-induced systemic vasodilation due to reduced NO bioavailability

Hypercholesterolemia impairs endothelial function [e.g., the nitric oxide (NO)-cyclic GMP-phosphodiesterase 5 (PDE5) pathway], limits shear stress-induced vasodilation, and is therefore expected to reduce exercise-induced vasodilation. To assess the actual effects of hypercholesterolemia on endothelial function and exercise-induced vasodilation, we compared the effects of endothelial NO synthase (eNOS) and PDE5 inhibition in chronically instrumented Yucatan (Control) and Rapacz familial hypercholesterolemic (FH) swine, at rest and during treadmill exercise. The increases in systemic vascular conductance produced by ATP (relative to nitroprusside) and exercise were blunted in FH compared with Control swine. The vasoconstrictor response to eNOS inhibition, with nitro-l-arginine (NLA), was attenuated in FH compared with Control swine, both at rest and during exercise. Furthermore, whereas the vasodilator response to nitroprusside was enhanced slightly, the vasodilator response to PDE5 inhibition, with EMD360527, was reduced in FH compared with Control swine. Finally, in the pulmonary circulation, FH resulted in attenuated vasodilator responses to ATP, while maintaining the responses to both NLA and EMD360527. In conclusion, hypercholesterolemia reduces exercise-induced vasodilation in the systemic but not the pulmonary circulation. This reduction appears to be the principal result of a decrease in NO bioavailability, which is mitigated by a lower PDE5 activity.