Jialian Li

Detection of quantitative trait loci associated with several internal organ traits and teat number trait in a pig population.

Quantitative trait loci (QTL) were detected for 8 internal organ traits, 3 carcass length traits, and teat number trait in 214 pigs in a resource population that included 180 F(2) individuals. A total of 39 microsatellite markers were examined on SSC4, SSC6, SSC7, SSC8, and SSC13. The genetic traits included heart weight (HW), lung weight (LW), liver and gallbladder weight (LGW), spleen weight (SPW), stomach weight (STW), small intestine weight (SIW), large intestine weight (LIW), kidney weight (KW), carcass length to the first cervical vertebra (CL1), carcass length to the first thoracic vertebra (CL2), rib numbers (RNS), and teat numbers (TNS). Results indicated that, 3 highly significant QTL (P <or= 0.01 at chromosome-wise level) for HW (at 30 cM on SSC6), RNS (at 115 cM on SSC7), TNS (at 110 cM on SSC7), and 6 significant QTL (P <or= 0.05 at chromosome-wise level) for LW (at 119 cM on SSC13), LGW (at 94 cM on SSC6), SPW (at 106 cM on SSC8), SIW (0 cM on SSC4), LIW (170 cM on SSC 4), and TNS (at 95 cM on SSC6) were detected. The phenotypic variances for which these QTL were accounted ranged from 0.04 % to 14.06 %. Most of these QTL had not been previously reported.

miR-762 promotes porcine immature Sertoli cell growth via the ring finger protein 4 (RNF4) gene

A growing number of reports have revealed that microRNAs (miRNAs) play critical roles in spermatogenesis. Our previous study showed that miR-762 is differentially expressed in immature and mature testes of Large White boars. Our present data shows that miR-762 directly binds the 3′ untranslated region (3′UTR) of ring finger protein 4 (RNF4) and down-regulates RNF4 expression. A single nucleotide polymorphism (SNP) in the RNF4 3′UTR that is significantly associated with porcine sperm quality traits leads to a change in the miR-762 binding ability. Moreover, miR-762 promotes the proliferation of and inhibits apoptosis in porcine immature Sertoli cells, partly by accelerating DNA damage repair and by reducing androgen receptor (AR) expression. Taken together, these findings suggest that miR-762 may play a role in pig spermatogenesis by regulating immature Sertoli cell growth.

Genetic Analysis and Linkage Mapping in a Resource Pig Population Using Microsatellite Markers

The use of markers and linkage map construction are important for QTL mapping in pigs. In this article, the genetic characteristics were studied and the linkage map was constructed in a pig resource population including 214 individuals by typing 39 microsatellite marker loci on Sus scrofa chromosomes, SSC4, SSC6, SSC7, SSC8, and SSC13. Results indicated that the average allele number, the average observed heterozygosity (H(0)), and the average polymorphism information content (PIC) in F(1) and F(2) population were 3.2, 0.528, 0.463 and 3.2, 0.496, 0.447, respectively. In the pig resource population, the average informative meiosis (IM) was 217.4 (44-316), and the average linkage map length between the two sexes on the five chromosomes were 172.3 cM (SSC4), 168.7 cM (SSC6), 191.7 cM (SSC7), 197.3 cM (SSC8), and 178.3 cM (SSC13). The orders of microsatellite marker loci in the linkage maps were identical to, but the length was greater than, those of USDA-MARC reference map. The results of this research showed the genetic relationship and genetic characteristics of the microsatellite markers in the pig resource family population, and the linkage map could be used to for QTL mapping in the subsequent study.

Genome-wide differential expression of genes and small RNAs in testis of two different porcine breeds and at two different ages.

Some documented evidences proved small RNAs (sRNA) and targeted genes are involved in mammalian testicular development and spermatogenesis. However, the detailed molecular regulation mechanisms of them remain largely unknown so far. In this study, we obtained a total of 10,716 mRNAs, 67 miRNAs and 16,953 piRNAs which were differentially expressed between LC and LW pig breeds or between the two sexual maturity stages. Of which, we identified 16 miRNAs and 28 targeted genes possibly related to spermatogenesis; 14 miRNA and 18 targeted genes probably associated with cell adhesion related testis development. We also annotated 579 piRNAs which could potentially regulate cell death, nucleosome organization and other basic biology process, which implied that those piRNAs might be involved in sexual maturation difference. The integrated network analysis results suggested that some differentially expressed genes were involved in spermatogenesis through the ECM–receptor interaction, focal adhesion, Wnt and PI3K–Akt signaling pathways, some particular miRNAs have the negative regulation roles and some special piRNAs have the positive and negative regulation roles in testicular development. Our data provide novel insights into the molecular expression and regulation similarities and diversities of spermatogenesis and testicular development in different pig breeds at different stages of sexual maturity.

Effects of feeding regimen on weight gain, semen characteristics, libido, and lameness in 170- to 250-kilogram Duroc boars1

A 2-period field trial was conducted to determine the effects of feeding regimen on weight gain, semen characteristics, libido, and lameness in 170- to 200-kg (period 1) and 200- to 250-kg (period 2) boars. Sixty-one Duroc boars were allotted to 1 of 3 dietary treatments and 15 g/d fish oil was also provided for each experimental boar, to maintain the n-6:n-3 intake ratio at approximately 6.1:1. The energy intakes of the 3 treatment groups were controlled by basing the feed intake on a corn-soybean meal-based diet (3.11 Mcal/kg of ME) to create: 1) low energy intake group (L, = 20, 7.3 Mcal/d of ME), 2) medium energy intake group (M, = 20, 7.7 Mcal/d of ME), and 3) high energy intake group (H, = 21, 8.3 Mcal/d of ME) in period 1. Feed intake was then increased to 7.6, 8.2, and 8.6 Mcal/d of ME for the 3 groups, respectively, in period 2. During the 28-wk experimental period, boar weight gain, testis volume, semen characteristics, libido, toe measurements, claw lesions, and lameness were examined, and the number of boars culled in each group was recorded to calculate the culling rate. Although there were no differences in testis volume, sperm concentration, and motility, the percentage of abnormal sperm, the percentage of claw lesions, and claw lesion scores differed among treatments ( > 0.05), and ADG was significantly increased with the increase of energy intake between the 2 periods ( < 0.05). The M and H boars had significantly greater total sperm number and functional sperm number than the L boars ( < 0.05), while no significant difference was observed between the M and H groups ( > 0.05). Nonetheless, the H boars took more time to mount the collection dummy and produce an ejaculate and, in particular, showed a greater percentage of lameness than the L and M boars ( < 0.05). Therefore, the medium energy intake regimen (energy intakes of 7.7 and 8.2 Mcal/d of ME with ADG of 454.5 and 375.3 g/d in 2 periods, respectively) improved the total sperm number and functional sperm number, and meanwhile decreased the occurrence of lameness in 170- to 250-kg Duroc boars.

Association analyses of polymorphisms in porcine MYF5 and MYOD1 genes with carcass traits

The objective of this study was to assess the effect of polymorphisms of myogenic factor 5 (MYF5) and myogenic differentiation 1 (MYOD1) genes on carcass traits in pigs. PCR-RFLP was used to identify three and one SNP(s) from the MYF5 and the MYOD1 gene, respectively. Association analysis performed on the four polymorphisms in a series of three Large White × Meishan F2 populations totalling near 400 pigs showed: (1) an MYF5 exon 1 Hsp92II polymorphism causing a Met→Leu substitution was significantly associated with fat meat percentage, shoulder fat thickness, thorax-waist fat thickness, average backfat thickness and carcass length to 1st rib (P < 0.05); (2) an MYF5 exon 2 MspI polymorphism and an intron 1 HaeIII polymorphism, which were completely linked, were significantly associated with thorax-waist fat thickness, 6–7th rib fat thickness and carcass length to 1st rib (P < 0.05); (3) an MYOD1 intron 1 DdeI polymorphism was significantly associated with carcass length to 1st rib.

Linear growth model analysis of factors affecting boar semen characteristics in Southern China1

This study investigated the factors affecting the semen traits of boars in Southern China. A total of 172,408 ejaculates of boars from 9 AI centers were collected from January 2013 to May 2016. A linear growth model was used to analyze the effects of leve1 1 (boar breed, age, season, and boar age at herd entry) and level 2 (housing type) factors on semen quality. The intraclass correlation coefficients of semen volume, total sperm number, functional sperm number, sperm concentration, motility, and abnormal sperm were 0.62, 0.62, 0.61, 0.60, 0.54, and 0.70, respectively. Boars reared in ordinary houses had lower total and functional sperm numbers than those reared in air filtration houses ( < 0.05). The functional sperm number of Duroc boars was lower than that of Landrace and Yorkshire boars ( < 0.05). The total and functional sperm numbers were lowest from May to September and peaked at the age of 34.1 and 37.7 mo, respectively. Furthermore, boars aged 8 and 9 mo at herd entry had greater functional sperm numbers than those aged 5, 6, 7, and 12 mo at herd entry ( < 0.05), whereas no significant difference was observed between boars aged 8 mo and boars aged 9 mo at herd entry ( > 0.05). In conclusion, the linear growth model is suitable for longitudinal data analysis. To improve boar breeding, sunstroke prevention in the early spring should be given greater attention. Importantly, 8 mo appears to be the most suitable age for boar introduction, especially for Duroc boars.

Supplementing oregano essential oil to boar diet with strengthened fish oil: Effects on semen antioxidant status and semen quality parameters.

Previous research has shown benefits of dietary fish oil supplementation on semen quality of boars. However, little is known about how antioxidant protects lipid peroxidation on spermatozoa from n‐3 polyunsaturated fatty acid (PUFA) addition. This study evaluated the effect of oregano essential oil (OEO) supplementation on semen antioxidant status and semen quality in boars fed a diet enriched with fish oil. Thirty‐four mature boars of proven fertility, received daily 2.5 kg basal diet top‐dressed with 45 g soybean oil and 15 g fish oil to meet the n‐3 PUFA requirement of spermatozoa, randomly allocated to one of four groups supplemented with 100 mg α‐tocopheryl acetate kg−1 (control), or 250 or 500 or 750 mg OEO kg−1 for 16 weeks. Semen was collected at weeks 0, 8, 12 and 16 for measurements of sperm production, motion characteristics, sperm α‐tocopherol content, antioxidant enzyme activities, reactive oxygen species (ROS), DNA damage (8‐hydroxydeoxyguanosine, 8‐OHdG), lipoperoxidation (malondialdehyde, MDA) and seminal total antioxidant capacity (TAC). Sperm production and motion characteristics were similar (p > .05) among groups throughout the experimental week 16, but increased (p < .01) with experimental week. Although higher α‐tocopherol content and superoxide dismutase (SOD) activities were in OEO group spermatozoa, feeding diet with 500 mg/kg OEO resulted in elevation in seminal TAC, decrease in sperm ROS, MDA and 8‐OHdG than control group (p < .05). Overall, these results support the view that oregano essential oil has a positive effect on antioxidant capacity in boar when used fish oil.