Mapping QTL for porcine muscle fibre traits in a White Duroc × Erhualian F2 resource population

Muscle fibre traits are related with meat quality in meat animals. In this study, a whole‐genome scan with 183 microsatellite markers covering the pig genome was performed to identify quantitative trait loci (QTL) for cross‐sectional area, numerical percentage and relative area of type I, IIA and IIB myofibres, fibre number per square centimetre and total fibre number in the longissimus muscle by using 120 F₂ animals in a White Duroc × Erhualian intercross. In total, 20 QTL were mapped on pig chromosomes (SSC) 1, 2, 7, 8, 9, 11, 15, 16 and X, of which eight reached genome‐wide significance levels and explained large proportions (6.53–34.63%) of phenotypic variance. Five QTL detected in this study confirmed the previous QTL reports and the others were detected for the first time. Chinese Erhualian alleles are generally associated with muscle fibre traits favourable for meat quality.     

MAGNETIC RESONANCE IMAGING OF THE CANINE BRAIN AT 3 AND 7 T

Magnetic resonance (MR) imaging of the canine brain is commonly acquired at field strengths ranging from 0.2 to 1.5 T. Our purpose was to compare the MR image quality of the canine brain acquired at 3 vs. 7 T in dogs. Low‐resolution turbo spin echo (TSE) T2‐weighted images (T2W) were obtained in transverse, dorsal, and sagittal planes, and high‐resolution TSE T2W and turbo spin echo proton density‐weighted images were obtained in the transverse and dorsal planes, at both 3 and 7 T. Three experienced reviewers evaluated 32 predetermined brain structures independently and without knowledge of field strength for spatial resolution and contrast. Overall image quality and evidence of artifacts were also evaluated. Contrast of gray and white matter was assessed quantitatively by measuring signal intensity in regions of interest for transverse plane images for the three pulse sequences obtained. Overall, 19 of the 32 neuroanatomic structures had comparable spatial resolution and contrast at both field strengths. The overall image quality for low‐resolution T2W images was comparable at 3 and 7 T. High‐resolution T2W was characterized by superior image quality at 3 vs. 7 T. Magnetic susceptibility and chemical shift artifacts were slightly more noticeable at 7 T. MR imaging at 3 and at 7 T provides high spatial resolution and contrast images of the canine brain. The use of 3 and 7 T MR imaging may assist in the elucidation of the pathogenesis of brain disorders, such as epilepsy.     

A genome scan for quantitative trait loci affecting the length of small intestine in a White Duroc × Chinese Erhualian intercross resource population

The small intestine is a vital organ in animal gastrointestinal system, in which a large variety of nutrients are absorbed. To identify quantitative trait loci (QTL) for the length of porcine small intestine, phenotypic values were measured in 1034 individuals at 240 d from a White Duroc × Chinese Erhualian intercross F₂ population. The length of small intestine showed strong correlation with growth traits and carcass length in the F2 population. A whole‐genome scan was performed based on 183 microsatellites covering the pig genome in the F₂ population. A total of 10 QTL for this trait were identified on 8 pig chromosomes (SSC), including four 1% genome‐wide significant QTL on SSC2, 4, 7 and 8, one 5% genome‐wide significant QTL on SSC12, and five 5% chromosome‐wide significant QTL on SSC5, 7, 13 and 14. The Erhualian alleles were generally associated with shorter length of the small intestine except the alleles on SSC7 and 13. The QTL on SSC4 overlapped with the previously reported QTL for the length of small intestine. Several significant QTL on SSC2, 8, and 12 were consistent with previous reports. The significant QTL detected on SSC7 was reported for the first time. All QTL identified in this study corresponded to the known region significantly associated with growth traits, supporting the important role of the length of small intestine in pig growth.     

Isolation,Identification and Enrichment of Type A Spermatogonia from the Testis of Chinese Cross‐Bred Buffaloes (Swamp × River)

The proportion of type A spermatogonia in the isolated testis cells is a prerequisite for conducting experiments and the manipulation of these germ cells. Thus, this study was designed to examine the wide range of strategies for the isolation, identification and enrichment of type A spermatogonia in pre‐pubertal buffalo calves (3–6 months). Histological findings revealed the presence of maximum number of type A spermatogonia at 5 months, which was further confirmed by DBA immunohistochemistry. In a newly modified strategy for the isolation of testis tissues, mincing followed by trituration and two rounds of digestion with collagenase, hyaluronidase and DNase yielded more than 95% testis cell population. Differential plating with laminin, poly‐l ‐lysine and gelatin significantly (p < 0.05) affected the purity of type A spermatogonia. Among these extracellular matrix (ECMs) molecules, laminin and gelatin performed well and reached at a purity of 39.38 ± 1.21% and 32.15 ± 1.60%, respectively. In addition, combination of laminin and gelatin followed by Percoll centrifugation performed the best and yielded >90% type A spermatogonial purity. Moreover, viability of the cells was not affected (p > 0.05) irrespective of different enrichment methods. In conclusion, type A spermatogonia isolation and enrichment system was developed using different ECM molecules in buffaloes, which will aid in solving wide range of problems especially fertility‐related problems and transgenic animal production in buffaloes.     

Effect of nutrient intake on intramuscular glucose metabolism during the early growth stage in cross‐bred steers (Japanese Black male × Holstein female)

The objective was to investigate the impact of nutrient intake during the early growth period on the expression of glucose metabolism‐related genes in skeletal muscle of cross‐bred cattle. From 1.5 to 5 months of age, group H (n = 7) animals were intensively fed a high‐protein and low‐fat milk replacer [crude protein (CP) 28%; ether extracts (EE) 18%; max: 2.0 kg, 12 l/day], and group R (n = 7) animals were fed a restricted amount of normal milk replacer (CP 25%; EE 23%; max 0.5 kg, 4 l/day). From 6 to 10 months of age, group H cattle were fed a high‐nutrition total mixed ration mainly prepared from grain feed, and group R cattle were fed only roughage. Blood samples were taken from each animal at three biopsy times (1.5, 5 and 10 months of age), and the blood plasma concentration of glucose and insulin was analysed. In glucose concentration, there were no significant differences; however, the concentrations of insulin were higher in group H than in group R at 5 and 10 months of age. Muscle samples were taken by biopsy from longissimus thoracis muscle (LT) at 1.5, 5 and 10 months of age. We analysed mRNA expression levels using the quantitative real‐time polymerase chain reaction (PCR) assay for glucose transporters (GLUT1 and GLUT4), insulin receptor, phosphatidylinositol 3‐kinase (PI‐3K), protein kinase B (PKB, also known as Akt), hexokinase 1 (HK1) and tumour necrosis factor alpha (TNFα). Although no differences were detected at 1.5 and 5 months of age, at 10 months of age, GLUT1, HK1 and TNFα mRNA expression levels were significantly higher in group H than in group R. These results suggested Glut1 that affects insulin‐independently mediated glucose uptake was more responsive to improved nutrition during early growth stage than GLUT4 that insulin‐dependently mediated glucose uptake in LT of cattle.     

Relation of reproductive performances and rectal palpation for luteum function of heifers 7 days after estrus

Diagnosis of corpus luteum (CL) function by rectal palpation (RP) has been widely used for recipient selection of embryo transfer (ET), a technology essential for genetic improvements in cattle. To examine the accuracy of RP diagnosis method, the relationship between RP‐based CL function and reproductive performance was compared in this study. In Experiment 1, CL of Holstein heifers on day 7 after estrus was classified into functional or hypoplastic by RP, and the results were compared with ultrasonographic (US) images and plasma progesterone (P4) levels. As a result, heifers with functional CL judged by RP had a mean maximum CL diameter of 20.1 ± 3.1 mm on US and a mean P4 concentration of 8.1 ± 2.3 ng/mL. These values were significantly greater than those of heifers with hypoplastic CL (12.4 ± 5.4 mm, 4.0 ± 2.8 ng/mL) (P < 0.001). In Experiment 2, the length of the estrus cycle was examined between functional CL and hypoplastic CL. The rate of heifers with a normal estrus cycle length with 18–25 days was significantly lower with hypoplastic CL than with functional CL (16/24 vs. 43/46, P < 0.01). In Experiment 3, 543 inseminated heifers were similarly classified by CL function by RP 7 days after estrus. The heifers with functional CL showed higher pregnancy rate compared with the heifers with hypoplastic CL (75.2 vs. 47.9%, P < 0.0001). Finally, the CL function of 66 heifers was examined by RP on day 7 post‐estrus, and ET was performed in 49 (74.2%) heifers with functional CL. As a result, 27 (55.1%) of them became pregnant. Taken together, these results reconfirm that RP on day 7 after estrus is useful for selection of heifers with functional CL.