Semen quality and fertilization ability of myostatin-knockout boars

The role of alginate oligosaccharide on boar semen quality: A research review

Alginate is the general term of a polysaccharide which is widely used in the area of pharmaceutics and the food industry and is known for its unique biological activities. However, due to the low water solubility and large viscosity of alginate, its development and utilization in the agricultural field are limited. Alginate oligosaccharide (AOS) is a degradable product derived from alginate and has attracted much attention in recent years because of its specific characteristics such as a low molecular weight, high water solubility, and non-toxicity. Boar semen quality, which is affected by various factors, is an important indicator for measuring reproductive performance of boars. With the development of artificial insemination technology, high quality semen has been more and more important. Therefore, increasing semen quality is an important means to improve the reproductive performance in swine industry. In this research review, we used the PubMed database and Google Scholar and web of science to search for relevant literature on the topic of AOS in relation to boar semen quality. Key words used were alginate oligosaccharide, boars, semen quality, microbiota and metabolites. The purpose of this review article was to describe the current knowledge on the relationship between AOS and boar semen quality, and provide an overview of solutions for the decline in the boar semen quality in specific conditions. Based on the existing literature, it is evident that AOS can be used as a new type of food additive. This review paper provides a theoretical basis for the production of high-quality boar sperm and, suggests that, in the future, AOS can even aid in treating human infertility.

Application of PCR-RFLP for quick identification of MSTN mutants in MSTN mutant pig breeding

Knockout of the MSTN gene is linked to the enlarged tongue, and it causes suckling difficulty in animals. The suckling difficulty has a severe effect on animal mortality. Thus, special care was required to ensure their survivability. Here, it is critical to promptly ascertain the genotype of all pigs after birth. The main objective of the present study was to develop the restriction enzyme-mediated PCR-RFLP assay for MSTN mutant pig genotyping. To accomplish this, conserved oligonucleotide primer and restriction site were deduced according to the mutated sequence of the MSTN mutant pigs. PCR amplification yielded a 176 bp band for all homozygous MSTN mutant (MSTN-/-), heterozygous MSTN mutant (MSTN+/-) and wild-type (WT) pigs. However, MSTN+/- samples produced two fragments with 176 and 87 bp, and WT samples produced one fragment with 87 bp after being digested by BstNI. MSTN-/- samples were not digested by BstNI and yielded a 176 bp band. Thus, we were able to determine the genotype of all pigs using BstNI restriction enzyme-mediated PCR-RFLP method. Overall, the present study reported a simple and fast PCR-RFLP genotyping method for MSTN mutant pig breeding. The present study may contribute to the establishment of commercial breeding systems and the production of double muscle pigs.

Effects of myostatin gene knockout on porcine extraocular muscles

Myostatin (MSTN), a negative regulator of skeletal muscle mass, is not well known in extraocular muscles (EOMs). EOMs are specialized skeletal muscles. Hence, in this study, the effect of MSTN on the superior rectus (SR) and superior oblique (SO) of 2-month-old MSTN knockout (MSTN-/-) and wild-type (WT) pigs of the same genotype was investigated. SR (P < 0.01) and SO (P < 0.001) fiber cross-sectional areas of MSTN-/- pigs were significantly larger than those of WT pigs. Compared with WT pigs, MSTN-/- SO displayed a decrease in type I fibers (WT: 27.24%, MSTN-/-: 10.32%, P < 0.001). Type IIb fibers were higher in MSTN-/- pigs than in WT pigs (WT: 30.38%, MSTN-/-: 62.24%, P < 0.001). The trend in SR was the same as that in SO, although the trend in SO was greater than that in SR. The expression of myogenic differentiation factor (MyoD) and myogenic (MyoG) showed a significant increase in MSTN-/- SO (about 2.5-fold and 2-fold, respectively at the gene expression level, about 1.5-fold at the protein level) compared with WT pigs. MSTN plays an important role in the development of EOMs and regulates the muscle fiber type by modulating the gene expression of MyoD and MyoG in pigs.

Reproduction and viscera organ characteristics of MSTN and FGF5 dual-gene knockout sheep

Introduction

Myostatin (MSTN) negatively regulates skeletal muscle development. However, its function in reproductive performance and visceral organs has not been thoroughly investigated. Previously, we prepared a MSTN and fibroblast growth factor 5 (FGF5) double-knockout sheep, which was a MSTN and FGF5 dual-gene biallelic homozygous (MF−/−) mutant.

Methods

To understand the role of MSTN and FGF5 in reproductive performance and visceral organs, this study evaluated the ejaculation amount, semen pH, sperm motility, sperm density, acrosome integrity, rate of teratosperm, and seminal plasma biochemical indicators in adult MF−/− rams. We also compared the overall morphology, head, head-neck junction, middle segment and the transection of middle segment of spermatozoa between wildtype (WT) and MF−/− rams.

Results

Our results showed that the seminal plasma biochemical indicators, sperm structure and all sperm indicators were normal, and the fertilization rate also has no significant difference between WT and MF−/− rams, indicating that the MF−/− mutation did not affect the reproductive performance of sheep. Additional analysis evaluated the histomorphology of the visceral organs, digestive system and reproductive system of MF+/− sheep, the F1 generation of MF−/−, at the age of 12 months. There was an increased spleen index, but no significant differences in the organ indexes of heart, liver, lung, kidney and stomach, and no obvious differences in the histomorphology of visceral organs, digestive system and reproductive system in MF+/− compared with WT sheep. No MF+/− sheep were observed to have any pathological features.

Discussion

In summary, the MSTN and FGF5 double-knockout did not affect reproductive performance, visceral organs and digestive system in sheep except for differences previously observed in muscle and fat. The current data provide a reference for further elucidating the application of MSTN and FGF5 double-knockout sheep.

When Less Is More: Targeting the Myostatin Gene in Livestock for Augmenting Meat Production

How to increase meat production is one of the main questions in animal breeding. Selection for improved body weight has been made and, due to recent genomic advances, naturally occurring variants that are responsible for controlling economically relevant phenotypes have been revealed. The myostatin (MSTN) gene, a superstar gene in animal breeding, was discovered as a negative controller of muscle mass. In some livestock species, natural mutations in the MSTN gene could generate the agriculturally desirable double-muscling phenotype. However, some other livestock species or breeds lack these desirable variants. Genetic modification, particularly gene editing, offers an unprecedented opportunity to induce or mimic naturally occurring mutations in livestock genomes. To date, various MSTN-edited livestock species have been generated using different gene modification tools. These MSTN gene-edited models have higher growth rates and increased muscle mass, suggesting the high potential of utilizing MSTN gene editing in animal breeding. Additionally, post-editing investigations in most livestock species support the favorable influence of targeting the MSTN gene on meat quantity and quality. In this Review, we provide a collective discussion on targeting the MSTN gene in livestock to further encourage its utilization opportunities. It is expected that, shortly, MSTN gene-edited livestock will be commercialized, and MSTN-edited meat will be on the tables of ordinary customers.

Reproduction traits of heterozygous myostatin knockout sows crossbred with homozygous myostatin knockout boars

Few studies exist on homozygous myostatin gene mutant (MSTN^-/- ) pigs, especially on their reproductive ability. We have previously shown that semen quality of homozygous MSTN^-/- boars is comparable to that of wild type (WT). However, no data exist on the reproductive ability of heterozygous MSTN gene mutant (MSTN^{+/ -} ) sows. The present study highlights showed that the heterozygous MSTN^{+/ -} sows have delayed pubertal age than WT sows (255.80 ± 6.79 versus 191.10 ± 3.42, respectively). The number of services per pregnancy of heterozygous MSTN^{+/ -} sows is significantly higher than that of WT sows (3.33 ± 0.43 versus 1.60 ± 0.25, respectively). Moreover, although heterozygous MSTN^{+/ -} sows have natural reproduction ability, their litter size was significantly lower than that of WT sows (7.75 ± 0.44 versus 14.25 ± 0.60, respectively). Offsprings generated from heterozygous MSTN^{+/ -} sow and homozygous MSTN^-/- boar were genotyped with the PCR and sequencing method to detect myostatin mutation and to identify whether the piglets are homozygous MSTN^-/- or heterozygous MSTN^{+/ -} . The proportion of homozygous MSTN^-/- piglets was significantly lower than that of heterozygous MSTN^{+/ -} piglets (2.50 ± 0.35 versus 5.25 ± 0.60, respectively). Furthermore, none of the sows presented dystocia, and the phenotype of heterozygous MSTN^{+/ -} piglets was normal. However, 10% homozygous MSTN^-/- piglets died of dyspnoea within 2 hr after birth, 60% of homozygous MSTN^-/- piglets showed large tongues, and 50% had umbilical hernias. In summary, this study for the first time reports the reproduction traits of heterozygous MSTN^{+/ -} sows crossbred with homozygous MSTN^-/- boars. This study will pave the way in a new direction for the breeding and development of super lean meat varieties in the future.

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.