The objective of this study was to estimate the genetic parameters of reproductive traits in heifers and adult cows and to elucidate the genetic correlations of these traits between heifers and adult cows as well as across different parities. This study collected a total of 84 061 reproductive records， including calving， insemination， and pregnancy diagnosis， from 37 329 Holstein cows in 6 large-scale dairy farms in Jiangsu Province between 2020 and 2024. Among these， 31 689 records were from heifers and 52 372 records were from cows. Genetic parameters were estimated using the average information restricted maximum likelihood （AI-REML） procedure implemented in the DMU software based on animal and repeatability models. The results showed that the heritability estimates of reproductive traits in heifers ranged from 0.04 to 0.52， with the highest value observed for age at first service （0.52±0.01）， while the heritability of the other traits ranged from 0.04 to 0.22. In heifers， the genetic correlations among age at first service， age at last service， and age at first calving were high， ranging from 0.73 to 0.98. In cows， the highest genetic correlations were observed between days open and the number of services and interval between first and last service， with values ranging from 0.95 to 0.96. The genetic correlations of reproductive traits between adjacent parities were relatively high， with values ranging from 0.62 to 0.68 between heifers and primiparous cows. By contrast， the correlations between heifers and multiparous cows were low （0.05-0.15）. Furthermore， phenotypic correlations across different parities were generally low， ranging from 0.01 to 0.18. In addition， the absolute genetic correlations of number of services and interval between first and last service with other traits were relatively high， ranging from 0.28 to 0.97， suggesting that these traits could serve as important indicators of reproductive performance in both heifers and cows. This study systematically elucidated the genetic parameters of reproductive traits in Holstein cattle in Jiangsu Province， providing a theoretical basis for the genetic improvement of reproductive traits in this population.

This study aimed to elucidate the phenotypic patterns and genetic architecture of fertility traits in Ningxia Holstein cattle， providing a theoretical basis for establishing a balanced breeding program in the region. We compiled 216 787 fertility records from 92 152 Holstein cattle across 15 farms in Ningxia during 2005—2024. Genetic parameter were estimated for 4 heifer traits and 9 cow traits （first， second， and third parities） using the AI-REML algorithm in DMU. Single-trait animal models were fitted to estimate heritability within parity， whereas bivariate models were used to get genetic and phenotypic correlations. Heifer heritabilities ranged from 0.097 0±0.008 to 0.500 9±0.012 9， with AFS the highest and CR_h the lowest. Heritability estimates for fertility traits in cows across the first， second， and third parities ranged from 0.007 6 （0.002 5） to 0.150 8 （0.011 6）， 0.010 1 （0.003 4） to 0.149 9 （0.010 2）， and 0.003 9 （0.005 2） to 0.137 6 （0.013 3）， respectively； differences for the same trait between parities were small and consistently lower than those observed in heifers. Genetic and phenotypic correlations among heifer fertility traits ranged from -0.845 8 to 0.835 1 and from -0.550 7 to 0.908 4， respectively； the strongest negative genetic correlation （-0.845 8） was observed between CR_h and IFL_h. Within any parity， genetic and phenotypic correlations among cow fertility traits showed consistent trends， with phenotypic correlations consistently lower than genetic correlations. As parity increased， genetic correlations strengthened among DO， IFL_c， and CI， whereas BW， CS， CE and GL exhibited weak genetic correlations with other fertility traits and can be selected independently. The same fertility trait measured in adjacent parities showed high genetic correlations， indicating that it is largely controlled by the same gene， whereas the phenotypic correlations remained low， suggesting that the trait is strongly influenced by environmental factors. Fertility traits show low-to-moderate heritability in Ningxia Holstein cattle， with greater genetic variation in heifers. CR_h and IFL_h are strongly and negatively correlated and should be treated as core traits in a heifer fertility index. DO， IFL_c， and CI can be selected jointly， and multi-parity records for cow fertility traits can be combined to increase selection accuracy. This study provides scientific basis for developing a balanced breeding programs for Holstein cattle in Ningxia and facilitates the simultaneous improvement of fertility and productive performance.

This study aimed to analyze the effects of dietary supplementation with flaxseed （Linum usitatissimum） and Schizochytrium on rumen microorganisms and meat fatty acid profiles in yaks.Twenty-one 12-month-old male healthy yaks weighing （95.00±5.20） kg were selected and divided into 3 groups according to the test requirements， with 7 replicates in each group. Supplementary feeding group （S） served as the control group， and the 2 experimental groups were fed with flaxseed （Y） and Schizochytrium （L） respectively for 210 days to analyze the effects on the microbial community structure and differential metabolites in the rumen of housed yaks， in conjunction with 16S rRNA sequencing and non-target metabolomes. Flaxseed and Schizochytrium supplementation significantly affected growth performance， muscle fatty acid composition， and rumen microbiota. Both treatment groups showed significantly lower dry matter intake （P<0.05） but improved feed conversion ratio （P<0.05）. The Schizochytrium group exhibited significantly higher muscle docosahexaenoic acid （DHA） content （0.35% vs. control 0.04%， P<0.05） and lower n-6/n-3 PUFA ratio （5.42 vs. control 36.28）. The flaxseed group showed increased total fatty acids （1.44 g vs. control 0.85 g， P<0.05）. Rumen analysis revealed significantly higher Firmicutes phylum abundance （69% vs. control 57%， P<0.05） and significantly lower Bacteroidota abundance （21% vs. control 27%，P<0.05） in the flaxseed group. The Schizochytrium group demonstrated increased Prevotella genus abundance （7.5% vs. control 3.9%， P<0.05）. α-diversity decreased in treatment groups versus control， while β-diversity differed significantly among groups. Muscle metabolomics analysis results indicated the downregulated phospholipid and acylcarnitine metabolism （P<0.05） and upregulated fatty acid derivatives in both treatment groups. Rumen microbiota correlated significantly with muscle metabolism （e.g.， Patescibacteria positively correlated with succinic acid metabolism， P<0.05）. Flaxseed and Schizochytrium promote lipid deposition in yaks by affecting rumen microbes and muscle metabolism， providing a theoretical basis for precision feeding strategies in alpine regions.

This study aimed to identify pregnancy-associated differentially methylated genes and develop an early pregnancy detection technology utilizing methylation-specific fluorescent probes. This study focused on differentially methylated regions in gene promoters and CpG islands to identify potential biomarkers for swine pregnancy. Initially， methylation-specific PCR （MSP） was employed for preliminary validation of these differentially methylated regions. Subsequently， target-specific fluorescent probes were designed to establish an early pregnancy detection method based on quantitative methylation-specific PCR （qMSP）， followed by methodological verification. Compared with empty pregnant sows， the blood of pregnant sows at 25-30 days of gestation showed high methylation of VBP1 and CpG_280， while CpG_1360 showed low methylation， indicating that these sites may be involved in pregnancy regulation. Using β-actin as an internal reference probe， methylation probes for VBP1， CpG_280， and CpG_1360 were designed to establish a qMSP detection method for preliminary application. Concordance analysis between this methylation probe-based detection and ultrasound （B-ultrasound） showed ROC curve AUC values of 0.713 8， 0.608 0， and 0.746 6 （all>0.5）， with qMSP concordance rates of 85.0%， 78.75%， and 85.0%， respectively. This study is the first to confirm that VBP1 and CpG_280 are hypermethylated while CpG_1360 is hypomethylated during early sow pregnancy. The fluorescence probe-based methylation detection technology targeting these genes offers a novel method for early pregnancy diagnosis in swine.

This study aimed to explore the impact of different photoperiods on the hypothalamic-pituitary-gonadal （HPG） axis in poultry， to reveal the mechanisms by which light regulates the follicles development and egg production performance of hen， and to provide a theoretical basis for the development of technologies to regulate the reproduction of female poultry and enhance the reproductive performance of breeding poultry. A total of 860 healthy Xinghua hens， aged 290 days and in the egg-laying period， were randomly divided into a control group and a treatment group. The experiment lasted for 61 days， with the control group maintained on a lighting schedule of 16.5L：7.5D throughout the experimental period. The lighting schedule for the treatment group was 16.5L：7.5D from day 1 to day 7， 12L：12D from day 8 to day 42， 18L：6D from day 43 to day 50， and 16.5L：7.5D from day 51 to day 61. Egg production was recorded throughout the experiment， and ovarian development， blood hormone levels， and reproductive axis factor expression were measured on days 8， 43， and 61， respectively. The results showed that under 16.5 hours of light exposure， there was no significant difference in egg production between the two groups. Shortening the light exposure to 12 hours significantly suppressed egg production， while extending it to 18 hours rapidly increased the egg production rate， which remained higher than that of the control group after restoring 16.5 hours of light exposure. Consistent with egg production， reducing light exposure significantly decreased the number of LYF and SYF in the ovaries， while extending light exposure quickly increased the number of LYF. However， changes in light exposure had no significant effect on the ovarian index or the number of LWF. Results showed that shortened photoperiod significantly reduced GnRH levels in the treatment group （P<0.05）， while extended photoperiod restored hormone levels to those comparable with the control group， though the differences were not significant （P>0.05）. Furthermore， shortened photoperiod significantly downregulated the expression of hypothalamic GnRH and TRH （P<0.01）. In contrast， extended photoperiod increased the expression of GnIH， GnRH， VIP， and TRH in the hypothalamus， though these changes were not significantly different （P>0.05）. GnRH protein expression followed a trend consistent with that of GnRH.In the pituitary gland， shortened photoperiod led to a significant reduction in the expression of GnRHR， FSH， and PRL （P<0.01）， and a moderate decrease in TSH and LH expression. Under extended photoperiod， the expression of GnRHR， TSH， FSH， and LH recovered to levels similar to the control group.In the ovaries， shortened photoperiod resulted in decreased expression of LHR， FSHR， GnRHR， and PRLR， with significant reductions in LHR and GnRHR （P<0.05 or P<0.01）. Extended photoperiod restored the expression of these factors to control levels. Protein expression levels of FSHR， LHR， and PRLR were generally consistent with their corresponding gene expression trends， though none of the differences reached statistical significance （P>0.05）.In summary， these findings demonstrate that photoperiod regulates follicular development and laying performance in Xinghua chickens by modulating the expression of key factors along the reproductive axis. Shortened photoperiod downregulates the expression of reproductive-promoting factors and gonadal receptors， thereby reducing serum reproductive hormone levels and inhibiting both follicular development and egg production. Conversely， extended photoperiod upregulates reproductive factor expression， promoting follicular development and enhancing laying performance.

The study aimed to further understand the changes in steroid hormones and their related substances at different stages of follicular development in Holstein cows， and to provide a theoretical basis for exploring the process and mechanism of follicular development in cows. In this study， based on liquid chromatography-tandem mass spectrometry （LC-MS/MS） technology， Holstein cows （n=18） were used as research subjects. Targeted steroid metabolomics analysis was performed on follicles of three sizes at different developmental stages， with exploration and group comparison conducted on small （Small follicle， SF， <5 mm， n=6）， medium （Medium follicle， MF， 5-8 mm， n=6）， and large （Large follicle， LF， >8 mm， n=6） follicles. A total of 24 steroid substances were identified. Among them， 8 differential metabolites （6 down-regulated， 2 up-regulated） were found in the comparison between SF and MF； 6 differential metabolites （2 down-regulated， 4 up-regulated） were found in the comparison between MF and LF； and 6 differential metabolites （4 down-regulated， 2 up-regulated） were found in the comparison between SF and LF. Subsequent analysis of differential metabolites based on the KEGG database revealed that in SF and MF， the endocrine resistance pathway （P=0.04） and prostate cancer pathway （P=0.03） were significantly enriched. In conclusion， this study confirmed significant changes in steroid hormones and their related substances during follicular development in Holstein cows， providing a theoretical basis for in-depth understanding of changes in the cow reproductive system.

This study aimed to explore the differences in epididymal histological characteristics and gene expression profiles of Angora rabbits in spring，summer and autumn.Twelve 1-year-old male Angora rabbits with healthy body conditions and normal reproductive functions were chosen. Epididymal tissues of 4 Angora rabbits were collected in spring （no heat stress）， summer （intense heat stress） and autumn （no heat stress），respectively. The histological differences of the epididymis in different seasons were compared through HE staining，and the transcriptome profiles of the epididymis tissues in different seasons were analyzed using RNA-Seq technology. Histological analysis revealed that， compared with spring，heat stress in summer resulted in atrophy of the epididymal duct，disorganized arrangement of epithelial cells，and absence of sperm. In contrast，the epididymal morphology recovered in autumn，resembling that of spring，and exhibited an abundance of sperm. Transcriptome analysis revealed that a total of 1 133 differentially expressed genes （DEGs） were detected in the epididymal tissue between spring and summer，910 DEGs were detected between summer and autumn，while only 36 DEGs were detected between autumn and spring. Among them，the expression trends of 535 DEGs were opposite in spring/summer and summer/autumn groups，and their expression levels recovered in autumn and were similar to those in spring，which were consistent with the histological results of the epididymis. GO enrichment analysis revealed that the DEGs in epididymal tissue between spring and summer were mainly enriched in biological processes including immune response，response to external stimulus，sperm motility，flagellated sperm motility，epithelial cell apoptotic process，and programmed cell death，and cytokine-cytokine receptor interaction pathway. DEGs in the epididymis tissue from summer and autumn were significantly enriched in biological processes including immune response，response to external stimuli，positive regulation of flagellated sperm motility，sperm motility，and negative regulation of cell death，as well as TNF，Th1 and Th2 cell differentiation，Th17 cell differentiation，and cytokine-cytokine receptor interaction pathways. Analysis of gene expression trends indicated that the highly-expressed genes in summer，including 449 differentially expressed genes with opposite expression trends between spring/summer and summer/autumn，mainly enriched in immune responses，response to external stimulus，regulation of programmed cell death and regulation of apoptotic process. The low-expression genes in summer are mainly enriched in collagen fibril organization and amino acid transport. In conclusion， heat stress during summer damaged epididymis tissue structure and changed expression profiles of genes related to reproduction，immunity and apoptosis in Angora rabbits，which recovered to normal levels in autumn. This study provided an important theoretical basis for a in-depth understanding of the molecular mechanism of“summer infertility”in rabbits.

The study evaluated the effects of folic acid （FA） on rumen fermentation parameters， antioxidant indicators and microbial population in dairy cows in vitro. Four early lactation Holstein dairy cows were used as the donor of ruminal fluid， and the total mixed ratio of dairy cows was used as the fermentation substrate. The supplementation level of FA was 0， 1.5， 3.0， 4.5， 6.0， 7.5 and 9.0 mg·kg^-1 dry matter （DM）， respectively. After incubation at 39℃ for 24 h， ruminal DM degradability （DMD）， gas production （GP）， FA content， antioxidant indicators， fermentation parameters， microbial enzyme activity and population were determined. The results were showed as follows： 1） The DMD was greater （P<0.05） for the supplementation of FA at 1.5， 3.0 and 4.5 mg·kg^-1 DM， and the 24 h GP and theoretical maximum GP were greater （P<0.05） for the supplementation of FA at 1.5， 3.0， 4.5 and 6.0 mg·kg^-1 DM compared with other groups. 2） Ruminal fluid FA content was greater （P<0.05） and malondialdehyde content was lower （P<0.05） for the groups with FA supplementation compared with the control. The activity of superoxide dismutase was greater （P<0.05） in the groups with 1.5， 3.0， 4.5 and 6.0 mg·kg^-1 DM FA supplementation compared with other groups. The activity of glutathione peroxidase was greater （P<0.05） in the groups with supplementation of FA at 3.0， 4.5， 6.0 and 7.5 mg·kg^-1 DM than in the control and 1.5 mg·kg^-1 DM FA supplementation groups. The total antioxidant capacity activity was greater （P<0.05） for the supplementation of FA at 1.5， 3.0， 4.5， 6.0 and 7.5 mg·kg^-1 DM than for the control. 3） The groups with FA addition had greater （P<0.05） total volatile fatty acids （TVFA） and acetate production compared with the control， and the production of TVFA and acetate were greater （P<0.05） for the 3.0 and 4.5 mg·kg^-1 DM FA supplementation than for 7.5 and 9.0 mg·kg^-1 DM FA supplementation. 4） The groups with FA addition had greater （P<0.05） activities of cellobiase and xylanase compared with the control， and the activity of cellobiase was greater （P<0.05） for the supplementation of FA at 3.0， 4.5 and 6.0 mg·kg^-1 DM than for the supplementation of FA 1.5 and 7.5 mg·kg^-1 DM， and the activity of xylanase was greater （P<0.05） for the 1.5， 3.0 and 4.5 mg·kg^-1 DM FA supplementation than for the 7.5 and 9.0 mg·kg^-1 DM FA supplementation. 5） The groups with FA addition had greater （P<0.05） populations of total bacteria， protozoa and R. flavefaciens compared with the control. The total bacteria population was greater （P<0.05） in the 4.5， 6.0 and 7.5 mg·kg^-1 DM FA supplementation groups than in the 1.5 and 9.0 mg·kg^-1 DM FA supplementation groups. The R. flavefaciens population was greater （P<0.05） for the 1.5， 3.0 and 4.5 mg·kg^-1 DM FA supplementation than for the 7.5 and 9.0 mg·kg^-1 DM FA supplementation. The fungi population was greater （P<0.05） in the 3.0， 4.5， 6.0 and 7.5 mg·kg^-1 DM FA groups than in the control， 1.5 and 9.0 mg·kg^-1 DM FA groups. The R. albus population was greater （P<0.05） for the groups with 1.5， 3.0， 4.5 and 6.0 mg·kg^-1 DM FA supplementation than for the control， 7.5 and 9.0 mg·kg^-1 DM FA groups. The F. succinogenes population was greater （P<0.05） in the 4.5， 6.0， 7.5 and 9.0 mg·kg^-1 DM FA groups than in the control and 1.5 mg·kg^-1 DM FA group. In conclusion， the supplementation of FA improves rumen antioxidant status， stimulate cellulolytic and amylolytic bacteria growth， and resulting in an increase in DMD and TVFA production. The proper level of ruminal FA supply is 1.5-3.0 mg·kg^-1 DM in the condition of the current study.

This experiment aimed to investigate the effects of dietary supplementation with Glycyrrhiza polysaccharides （GCPs） on the growth performance， serum indicators， apparent nutrient digestibility， rumen fermentation parameters and microbial communities in fattening beef cattle. Forty Simmental fattening bulls with good growth status and an average body weight of 617.70±18.85 kg were selected as experimental animals and randomly divided into four groups. The experimental groups received the basal diet supplemented with 0 mg·kg^-1 BW （control group， G0）， 15 mg·kg^-1 BW （low-dose， G15）， 30 mg·kg^-1 BW （medium-dose， G30）， or 45 mg·kg^-1 BW （high-dose， G45） of GCPs， respectively. The trial included a 10-day adaptation period followed by a 90-day feeding period. The body weight were measured at 0， 45，90 d of the feeding period， daily feed intake was recorded to determine average dry matter intake and feed-to-gain ratio. At 45 and 90 d of the feeding period， 10 mL of blood sample was collected from each bull to assess serum biochemical， antioxidant and immune indicators. At the end of the trial， 300 g of feces sample was collected from each bull to evaluate nutrient apparent digestibility， and 50 mL of rumen fluid was collected to analyze rumen fermentation parameters and microbial related indicators. Compared with the G0 group： 1） During the 0-45 d and 0-90 d periods， the average daily gain and average dry matter intake of the G30 and G45 groups were significantly increased （P<0.05）； in the 0-90 d period， the feed conversion ratio of the G30 and G45 groups decreased significantly （P<0.05）， while the crude fat digestibility increased significantly （P<0.05）； 2） The serum aspartate aminotransferase level and alanine aminotransferase level of the G30 group were significantly decreased （P<0.05）； at 45 d， the serum levels of superoxide dismutase and interleukin-10 in the experimental groups increased significantly （P<0.05）； 3） The acetic acid proportion of the G15 and G30 groups was significantly decreased （P<0.05）， the butyric acid proportion of the G30 group was significantly increased （P<0.05）； 4） The Chao1 richness index of the rumen microbial community in the G30 group was significantly increased （P<0.05）， along with structural changes in microbial composition. In the G30 group， the relative abundance of Bacteroidota， Pseudomonadota， Fibrobacterota， Prevotella and Fibrobacter showed a significant upward trend， while the relative abundance of Bacillota showed a significant downward trend （P<0.05）； the differential metabolic pathways of rumen microorganisms in the G15 group were mainly enriched in Synthesis and Degradation of ketonebodies， and nitrotoluene degradation. In the G30 group， these pathways were mainly linked to Amino acid metabolism， and Fatty acid biosynthesis， while the G45 group showed enrichment in C5-branched dibasic acid metabolism. In summary， dietary supplementation of Glycyrrhiza polysaccharides enhanced the growth performance， antioxidant capacity， immune function， and nutrient digestibility of Simmental fattening beef cattle， while optimizing rumen fermentation patterns and promoting beneficial rumen microorganisms. Under the conditions of this experimental study， the optimal addition amount of GCPs was 30 mg·kg^-1 BW.

This study was conducted to investigate the effects of Bacillus subtilis （BS） and Chitosan oligosaccharides （COS） on growth performance， nutrient utilization， slaughter performance， meat quality and cecal microflora diversity of AA broilers. A total of 288 one-day-old broilers with similar body weight （46±0.64 g） were randomly divided into 6 treatment groups with 6 replicates per treatment and 8 chickens per replicate （ half male and half female ）. The control group （CON） was fed a basal diet， and the experimental groups were fed a basal diet supplemented with 5×10⁹ CFU·kg^-1Bacillus subtilis （BS1 group）， 6×10⁹ CFU·kg^-1Bacillus subtilis （BS2 group）， 125 mg·kg^-1 COS （COS group）， 5×10⁹ CFU·kg^-1Bacillus subtilis+125 mg·kg^-1 COS （MIX Ⅰ group）， 6×10⁹ CFU·kg^-1Bacillus subtilis+125 mg·kg^-1 COS （MIX Ⅱ group）. The experiment lasted for 42 days. The results were showed as follows： 1） From 1 to 21 days of age， compared with CON， ADG in MIX Ⅱ group was significantly increased （P<0.01）， and FCR in MIX Ⅱ group was significantly increased （P<0.01）. At 22-42 days of age， compared with CON， ADG in MIX Ⅰ and MIX Ⅱ groups were significantly increased （P<0.01）. From 1 to 42 days of age， compared with CON， the ADG of MIX Ⅰ and MIX Ⅱ groups were significantly increased （P<0.01）， and the FCR of MIX Ⅱ group was significantly increased （P=0.01）. 2） Compared with CON， the semi-eviscerated rate and eviscerated rate of BS2 group were significantly increased （P<0.05）. 3） Compared with CON， the crude protein utilization rate of broilers in MIX I group and COS group was significantly increased （P<0.05）. 4） Compared with CON， there was no significant difference in pH_{45 min}， pH_{24 h}， shear force， water loss rate， L^*， a^* or b^* among groups （P>0.05）. The drip loss of breast muscle in MIX Ⅰ group was significantly increased （P<0.01）， but the drip loss of leg muscle showed a downward trend， and the difference was not significant （P>0.05）. 5） Compared with CON， the Chao1， ACE and Shannon index of cecal flora in COS group increased by 0.13%， 0.52% and 1.56%， respectively， but the difference was not significant （P>0.05）. The Simpson index of cecal flora in COS group decreased by 5.2%， but the overall difference was not significant （P>0.05）. The BS2 group was significantly deviated from the other treatment groups on the PC1 axis. BS1 group， COS group， MIX Ⅰ group and MIX Ⅱ group were close to each other and tended to gather， with more overlapping parts， indicating that the composition of cecal flora was similar. At the phylum level， compared with CON， the relative abundance of Bacteroidetes and Verrucomicrobia in the cecal flora of broilers in MIX Ⅱ group increased， and the relative abundance of Proteobacteria in the cecal flora of broilers in BS1 group increased； at the genus level， compared with CON， the relative abundance of Bacteroides and Akkermansia in the cecal flora of broilers in MIX Ⅱ group increased. In summary， dietary supplementation of Bacillus subtilis or Chitosan oligosaccharides alone or their combination can promote the growth performance， improve meat quality， enhance the diversity and richness of cecal flora， and ensure the healthy growth of broilers to a certain extent.