Cryopreservation technology has become a primary method for preserving animal genetic resources in the biomedical field. It achieves long-term storage by placing gametes or embryos in an ultra-low-temperature environment, enabling them to retain biological activity after thawing. However, the cytotoxicity issues associated with traditional cryoprotectants limit their application, making the development of non-toxic and highly effective novel cryoprotectants a current research priority. This review systematically reviews the development history and principles of cryopreservation technology, and summarizes the classification and mechanisms of action of cryoprotectants, with a particular focus on five types of novel cryoprotectants featuring bioinspired structural characteristics. Their ice-suppression performance and mechanisms of action are analyzed. These protectants possess structures similar to those of natural antifreeze substances and exhibit low toxicity, thereby demonstrating higher cryopreservation efficiency, and are thus referred to as novel bioinspired cryoprotectants. Furthermore, this review examines the potential applications of the aforementioned protectants in the cryopreservation of animal gametes (sperm, oocytes, and embryos), offering new insights into expanding the use of bioinspired cryoprotectants in the preservation of animal genetic resources.

Our previous study has shown that supplementation of 0.50% benzoic acid (BA) increased growth performance, promoted rumen fermentation, and improved the composition and function of rumen microbiota. This research was designed to conduct a deeper exploration of the impacts of dietary supplementation with BA on the apparent digestibility of nutrients and the composition of rectal microbiota in weaned Holstein dairy calves. Sixteen Holstein heifer calves with similar body weights (91.2 ± 0.7 kg) were selected and randomly allocated into two groups, each comprising eight calves. Calves in the control group (CON group) were fed with a basal diet, while those in the benzoic acid group (BA group) were fed with the basal diet supplemented with 0.50% benzoic acid (on a dry matter basis). The experimental period started at 60 days of age and ended at 102 days of age, lasting for a total of 42 days. The calves were weaned at 60 days of age, with a transition period of 7 days. Feed samples were collected every two weeks, fecal samples were collected from 99 to 101 days of age, and blood samples were collected at 102 days of age. The results showed that supplementation with BA did not influence the digestibility of dry matter, crude protein, ether extract, neutral detergent fiber, acid detergent fiber, calcium, and phosphorus between the two groups. Compared with the CON group, BA supplementation tended to decrease the total cholesterol (TC) in the serum of the calves (p = 0.067). Supplementation with BA increased the relative abundances of the two beneficial bacteria, Bifidobacterium and Bifidobacterium pseudolongum (p < 0.05, LDA > 2), but decreased that of the harmful bacterium, Clostridium sensu stricto 1, in the rectum of dairy calves. The microbial functional prediction revealed that the fecal microbial metabolism involved in primary bile acid biosynthesis was higher in the calves from the BA group. In conclusion, the present study demonstrated that adding 0.50% BA to the diet did not influence the apparent nutrient digestibility, but improved rectal microbiota health, which finally promoted the growth performance in weaned Holstein dairy calves.

Transgenic cloning allows genetic modification in cattle, yet its translational potential is constrained by low cloning efficiency and limited gene-editing capacity, due largely to the restricted proliferative ability of somatic donor cells. Pluripotent stem cells (PSCs), with their unlimited self-renewal ability, represent a promising alternative to overcome these bottlenecks. Here, we first established stable bovine epiblast stem cell lines (bEpiSCs) and achieved site-specific integration of the HCSN2-HLF-GFP cassette into the β-casein locus, with high transfection (72.07%) and correct integration efficiency (80.48%). Following Cre LoxP mediated excision of the selectable marker, we obtained marker free HCSN2-HLF bEpiSCs that retained pluripotency markers, tri lineage differentiation potential, and supported target protein expression in immortalized bovine mammary epithelial cells. When used as nuclear donors, these cells produced blastocysts with quality comparable to in vitro fertilization (IVF) embryos. Notably, cloning with HCSN2-HLF bEpiSCs resulted in the birth of twelve calves, with significantly higher birth and survival rates (30.71% and 16.74%, respectively) than those obtained using fibroblasts. Both PCR-based genotyping of the edited loci and microsatellite kinship analysis confirmed that all cloned calves were genetically derived from the HCSN2-HLF bEpiSCs. Collectively, this study establishes an efficient embryonic stem cell based platform for targeted gene editing and rapid production of multigene edited cloned cattle, offering a scalable strategy with strong potential for industrial translation. ### Competing Interest Statement The authors have declared no competing interest. the Biological Breeding-National Science and Technology Major Project (2023ZD0407503), the National Key R&D Program of China (2022YFD1302201), the Natural Science Foundation of China (32302746, 32370846), , Hebei Province Science and Technology Plan (23227602Z), and Shijiazhuang City Science and Technology Project (221790262A), the 2115 Talent Development Program of China Agricultural University

Supplementation with benzoic acid (BA) in animal feed can reduce feeds’ acid-binding capacity, inhibit pathogenic bacterial growth, enhance nutrient digestion, and increase intestinal enzyme activities. This study aimed to investigate the effects of different doses of BA on the growth performance, rumen fermentation, and rumen microbiota of weaned Holstein dairy calves. Thirty-two Holstein calves at 60 days of age were randomly assigned into four groups (n = 8): a control group (fed with a basal diet without BA supplementation; CON group) and groups that were supplemented with 0.25% (LBA group), 0.50% (MBA group), and 0.75% (HBA group) BA to the basal diet (dry matter basis), respectively. The experiment lasted for 42 days, starting at 60 days of age and ending at 102 days of age, with weaning occurring at 67 days of age. Supplementation with BA linearly increased the average daily gain of the weaned dairy calves, which was significantly higher in the LBA, MBA, and HBA groups than that in the CON group. The average daily feed intake was quadratically increased with increasing BA supplementation, peaking in the MBA group. Supplementation with BA linearly decreased the feed-to-gain (F/G) ratio, but did not affect rumen fermentation parameters, except for the molar proportion of butyrate and iso-butyrate, which were linearly increased with the dose of BA supplementation. Compared with the CON group, the molar proportions of iso-butyrate in the LBA, MBA, and HBA groups and that of butyrate in the HBA group were significantly higher than those in the CON group. Supplementation with BA had no significant effect on the alpha and beta diversity of the rumen microbiota, but significantly increased the relative abundances of beneficial bacteria, such as Bifidobacterium, and reduced those of the harmful bacteria, such as unclassified_o__Gastranaerophilales and Oscillospiraceae_UCG-002, in the rumen. Functional prediction analysis using the MetaCyc database revealed significant variations in the pathways associated with glycolysis across groups, including the GLYCOLYSIS-TCA-GLYOX-BYPASS, GLYCOL-GLYOXDEG-PWY, and P105-PWY pathways. In conclusion, BA supplementation improved the composition and function of rumen microbiota, elevated the production of butyrate and iso-butyrate, and increased the growth performance of weaned Holstein dairy calves.

In mammals, imprinted genes are characterised by a monoallelic expression, which is based on parental origin and is essential for both foetal and placental development. The ZFAT gene encodes a transcriptional factor, and its non-coding antisense RNA, ZFAT-AS1, overlaps with the ZFAT locus. Both ZFAT and ZFAT-AS1 are maternally imprinted in human placentas. In bovines, the imprinting status of the ZFAT and ZFAT-AS1 genes has yet to be reported. In this study, we analysed the allelic expression of three transcript variants (X1-X3) of the bovine ZFAT and ZFAT-AS1 genes in somatic tissues and placentas using a single nucleotide polymorphism-based method. The results showed that bovine ZFAT exhibited isoform-specific paternal expression. The ZFAT X2 variant exhibited monoallelic expression in the bovine placentas and biallelic expression in the six bovine somatic tissues (heart, liver, spleen, lung, kidney and brain). However, the ZFAT X1 and X3 variants were biallelically expressed in both bovine tissues and placentas. A 311 bp bovine ZFAT-AS1 complementary DNA (cDNA) sequence was obtained by aligning the human ZFAT-AS1 cDNA sequence with the bovine genome and conducting reverse transcription polymerase chain reaction amplification. Bovine ZFAT-AS1 have monoallelic expression in bovine placentas and somatic tissues. In addition, the DNA methylation of two regions was characterised, including the partial promoter, and exon 1 and intron 1 regions of ZFAT, and there were no differentially methylated regions.

Genomic imprinting is an epigenetic regulation in mammals in which a small subset of genes is monoallelically expressed dependent on their parental origin. A large imprinted domain, SGCE/PEG10 locus, is located on human chromosome 7q21s and mouse proximal chromosome 6. However, genomic imprinting of bovine SGCE/PEG10 cluster has not been systematically studied. In this study, we investigated allele expression of 14 genes of the SGCE/PEG10 locus in bovine somatic tissues and term placenta using a single nucleotide polymorphism (SNP)-based sequencing method. In addition to SGCE and PEG10, two conserved paternally expressed genes in human and mice, five other genes (TFPI2, GNG11, ASB4, PON1, and PON3) were paternally expressed. Three genes, BET1, COL1A2, and CASD1, exhibited tissue-specific monoallelic expression. CALCR showed monoallelic expression in tissues but biallelic expression in the placenta. Three genes, GNGT1, PPP1R9A, and PON2, showed biallelic expression in cattle. Five differentially methylated regions (DMRs) were found to be associated with the allelic expression of TFPI2, COL1A2, SGCE/PEG10, PON3, and ASB4 genes, respectively. The SGCE/PEG10 DMR is a maternally hypermethylated germline DMR, but TFPI2, COL1A2, PON3, and ASB4 DMRs are secondary DMRs. In summary, we identified five novel bovine imprinted genes (GNG11, BET1, COL1A2, CASD1, and PON1) and four secondary DMRs at the SGCE/PEG10 locus.

Genomic imprinting is an epigenetic regulation mechanism in mammals resulting in the parentally dependent monoallelic expression of genes. Imprinting disorders in humans are associated with several congenital syndromes and cancers and remain the focus of many medical studies. Cattle is a better model organism for investigating human embryo development than mice. Imprinted genes usually cluster on chromosomes and are regulated by different methylation regions (DMRs) located in imprinting control regions that control gene expression in cis. There is an imprinted locus on human chromosome 16q24.1 associated with congenital lethal developmental lung disease in newborns. However, genomic imprinting on bovine chromosome 18, which is homologous with human chromosome 16 has not been systematically studied. The aim of this study was to analyze the allelic expressions of eight genes (CDH13, ATP2C2, TLDC1, COTL1, CRISPLD2, ZDHHC7, KIAA0513, and GSE1) on bovine chromosome 18 and to search the DMRs associated gene allelic expression. Three transcript variants of the ZDHHC7 gene (X1, X2, and X5) showed maternal imprinting in bovine placentas. In addition, the monoallelic expression of X2 and X5 was tissue-specific. Five transcripts of the KIAA0513 gene showed tissue- and isoform-specific monoallelic expression. The CDH13, ATP2C2, and TLDC1 genes exhibited tissue-specific imprinting, however, COTL1, CRISLPLD2, and GSE1 escaped imprinting. Four DMRs, established after fertilization, were found in this region. Two DMRs were located between the ZDHHC7 and KIAA0513 genes, and two were in exon 1 of the CDH13 and ATP2C2 genes, respectively. The results from this study support future studies on the molecular mechanism to regulate the imprinting of candidate genes on bovine chromosome 18.

Traditional measurement methods often rely on manual operations, which are not only inefficient but also cause stress to cattle, affecting animal welfare. Currently, non-contact cattle dimension measurement usually involves the use of multi-view images combined with point cloud or 3D reconstruction technologies, which are costly and less flexible in actual farming environments. To address this, this study proposes an automated cattle dimension measurement method based on an improved keypoint detection model combined with unilateral depth imaging. Firstly, YOLOv8-Pose is selected as the keypoint detection model and SimSPPF replaces the original SPPF to optimize spatial pyramid pooling, reducing computational complexity. The CARAFE architecture, which enhances upsampling content-aware capabilities, is introduced at the neck. The improved YOLOv8-pose achieves a mAP of 94.4%, a 2% increase over the baseline model. Then, cattle keypoints are captured on RGB images and mapped to depth images, where keypoints are optimized using conditional filtering on the depth image. Finally, cattle dimension parameters are calculated using the cattle keypoints combined with Euclidean distance, the Moving Least Squares (MLS) method, Radial Basis Functions (RBFs), and Cubic B-Spline Interpolation (CB-SI). The average relative errors for the body height, lumbar height, body length, and chest girth of the 23 measured beef cattle were 1.28%, 3.02%, 6.47%, and 4.43%, respectively. The results show that the method proposed in this study has high accuracy and can provide a new approach to non-contact beef cattle dimension measurement.

红枣口味甘甜,营养价值丰富,可作为非常规饲料在动物生产中应用.但是红枣鲜果的含水量较高,需要进行一定处理才可作为饲粮使用.制作成枣粉饲料是提高红枣利用效果的方式之一.文章主要综述了我国红枣资源现状、红枣的营养成分、枣粉饲料的种类及其在动物生产中的应用和问题,为枣粉作为非常规饲料在动物生产中的应用提供参考.

In the current study, we explored the relationship between melatonin and lactose synthesis in in vivo and in vitro conditions. We found that long-term melatonin feeding to the dairy cows significantly reduced the milk lactose content in a dose dependent manner. This lactose reduction was not associated with a negative energy balance, since melatonin treatment did not alter the fat, glucose, or protein metabolisms of the cows. To identify the potential molecular mechanisms, the cow’s mammary epithelial cells were cultured for gene expression analysis. The results showed that the effect of melatonin on lactose reduction was mediated by its receptor MT1. MT1 activation downregulated the mRNA expression of the prolactin receptor gene (PRLR), which then suppressed the gene expression of SLC35B1. SLC35B1 is a galactose transporter and is responsible for the transportation of galactose to Golgi apparatus for lactose synthesis. Its suppression reduced the lactose synthesis and the milk lactose content. The discovery of this signal transduction pathway of melatonin on lactose synthesis provides a novel aspect of melatonin’s effect on carbohydrate metabolism in cows and maybe also in other mammals, including humans.

The experiment was to investigate the effect of supplementing leucine and tryptophan in low protein diets on growth performance, serum biochemical indicators, immune performance, and antioxidant capacity of weaned calves. Chinese Holstein calves with good health and similar birth weight (42±2) kg were randomly divided into five groups. The groups were HK group (22% CP level of open food), LK group (19% CP level of open food), L group (19% CP level containing 1.15% Leu of open food), T group (19% CP level of 0.26% Trp of open food), LT group (19% CP level of 1.15% Leu+ 0.26% Trp of open food). There were 12 replicates in each group with one calve in each replicate. The experiment lasted for 72 d. The results showed that final weight, average daily feed intake and average daily gain in LT group were higher than HK group (P<0.05). Three days before weaning, the content of BUN and IL-1 were lower than HK group (P<0.05). While the content of TP, IgM, interferon-γ, superoxide dismutase and catalase activities were significantly increased in LT group (P<0.05). On the day of weaning, compared with HK group, the activity of TP, IgA, IL-2 and T-AOC significantly increased (P<0.05). On the third day after weaning, the content of TNF-α was significantly increased in LT group (P<0.05). The experiment indicates that supplementation of Leu (1.15%) and Trp (0.26%) in low protein diet increased average daily gain and average daily feed intake of weaned calves, improve calf growth performance, enhanced immunity and oxidation ability of weaned calves, and alleviated weaning stress.

Oocyte maturation is a critical step in the completion of female gametogenesis in the ovary; thus, for subsequent fertilization and embryogenesis. Vitrification of embryo also has been shown to be closely associated with oocyte maturation. To improve the quality and developmental potential of bovine oocytes derived from in vitro maturation (IVM), Pre-IVM with C-type natriuretic peptide (CNP), melatonin (MT) and in combination, IGF1, FGF2, LIF (FLI) were supplemented in the IVM medium. In this current study, we cultured bovine oocytes in Pre-IVM with CNP for 6 h before transferring them to the IVM medium supplemented with MT and FLI. The developmental potential of bovine oocytes was then investigated by measuring the reactive oxygen species (ROS), the intracellular glutathione (GSH) and ATP levels, the transzonal projections (TZP), the mitochondrial membrane potential (ΔΨm), cacline-AM, and the expression of related genes (cumulus cells (CCs), oocytes, blastocysts). The results revealed that oocytes treated with a combination of CNP, MT, and FLI had dramatically improved the percentage of oocytes developed to blastocyst, ATP content, GSH levels, TZP intensity, the ΔΨm, cacline-AM fluorescence intensity, and considerably reduced ROS levels of oocytes. Furthermore, the survival rate and the hatched rate after vitrification of the CNP+MT+FLI group were significantly higher than those other groups. Thus, we speculated that CNP+MT+FLI increases the IVM of bovine oocytes. In conclusion, our findings deepen our understanding and provide new perspectives on targeting the combination of CNP, MT and FLI to enhance the quality and developmental potential of bovine oocytes.

试验采用体外产气法研究不同日粮30 h中性洗涤纤维(dNDF30)水平对反刍动物瘤胃发酵的影响.在等能等氮(蛋白含量为16.5％)与中性洗涤纤维(NDF)水平为32％下分别配制dNDF30水平为16.4％、17.9％、19.4％、20.9％、22.4％、23.9％、25.4％和26.9％的日粮为发酵底物,分别为T1组～T8组,每组8个重复.结果显示,体外发酵24 h,T1组的产气量(GP)显著低于其他各组(P<0.05).体外发酵48 h,T5组、T6组、T7组、T8组GP显著高于其他处理组(P<0.05).T8组的体外干物质消失率(IVDMD)最高,显著高于T1组、T2组、T3组、T4组(P<0.05).T8组pH值显著低于其他各组(P<0.05).T1组氨态氮(NH3-N)含量显著高于除T2外的各组(P<0.05).T1组微生物蛋白(MCP)含量显著高于其他各组(P<0.05).T8组总挥发性脂肪酸含量最高,显著高于除T7组、T6组之外的各组(P<0.05).T1组乙酸含量显著高于除T2组、T3组、T4组外各组(P<0.05).T8组丙酸含量显著高于T1组、T2组(P<0.05).研究表明,较高日粮dNDF30水平有利于氨氮的利用和反刍动物瘤胃发酵.

This experiment was conducted to investigate the effects of N-carbamylglutamate（NCG） supplementation in different doses on microflora composition in rumen and rectum of Holstein bulls. Forty-five healthy Holstein bulls [initial body weight（478±13.66） kg, 12 to 13 months of age] were randomly divided into three groups, and there were 15 bulls in each group, 0（group Ⅰ）, 15（group Ⅱ） and 25 g/（d·bull） NCG（group Ⅲ） were added in a basal diet, respectively. The pre-test period lasted for 7 days and the experimental period lasted for 90 days. Results showed as follows: with the increase of NCG supplemental dose, rumen microbial diversity was not significantly affected（P＞0.05）, but the relative abundance of Bacteroidetes showed linear decreasing trend（0.05＜P＜0.10）, while the relative abundance of Firmicutes showed linear increasing trend（0.05＜P＜0.10）. At genus level, the relative abundance of Ruminococcus 1 in group Ⅱ was significantly higher than that in group Ⅰ（P＜0.05）. The relative abundance of Ruminococcaceae UCG-005 showed increasing trend（P=0.05）, and the relative abundance of Succinivibrio showed linear increasing with the increase of NCG supplemental dose（P＜0.05）, and the relative abundance of Lachnospiraceae 2 showed linear increasing trend with the increase of NCG supplemental dose（0.05＜P＜0.10）. In the rectal microflora, the diversity of rectal microflora showed liner increasing trend with the increase of NCG supplemental dose（P＞0.05）. At phylum level, the supplement of NCG had no significant effect on rectal microflora（P＞0.05）, but the relative abundance of Patescibacteria showed quadratic curve change with the increase of NCG dose（0.05＜P＜0.10）. At genus level, the relative abundance of Rikenellaceae RC9 gut group showed liner increasing trend with doses the increase of NCG（0.05＜P＜0.10）, the relative abundance of Bifidobacterium and Ruminococcaceae UCG-010 in group Ⅱ was significantly higher than that in group Ⅰ（P＜0.05）, and there was no significant difference compared with group Ⅲ（P＞0.05）. In conclusion, the addition of NCG does not significantly increase the relative abundance of microorganisms in rumen and rectum except for Rumenococcus 1 at rumen genus level and Bifidobacterium and Ruminococcaceae UCG-010 at rectum genus level.

Recent years, techniques for in vitro embryo production（IVP） have advanced significantly, especially the ovum pick-up（OPU） technology grows widely. OPU is a new technology developed in the 1990 s that can obtain oocytes from excellent breeding heifers, which has a broad application prospect in the research of the mechanism of animal embryo production and development and in the clinical practice of human assisted reproductive technology. It can improve the resource protection efficiency of breeding females and precious wild animals, and the genetic potential of excellent females, and provide the necessary supporting technology for the development of cattle biotechnology. The quality of oocytes is the key to the success of the IVP system, and the in vitro maturation（IVM） process of the oocytes is critical for successful fertilization and embryo development. Oocyte IVM completes the cytoplasmic and nuclear maturation of the oocyte, preparing all necessary components for development to the activation of the embryonic genome. Developmental ability of oocytes matured in vitro is lower than that of oocytes matured in vivo, non-synchronization of oocyte meiosis and nucleocytoplasmic maturation, oxidative stress damage, et al are important for successful fertilization and embryo development. Therefore, it is necessary to further improve the in vitro maturation ability of oocytes to improve the bovine IVP system. In this paper, the problems of in vitro maturation of oocytes such as non-synchronization of nucleocytoplasmic maturation and oxidative stress were summarized, as well as the improvement effects of C-type natriuretic peptide, melatonin, FLI and other substances on oocytes IVM were discussed in order to improve the bovine IVP system.

[Objective] This study aimed to estimate the genetic parameters of body weight and body size for Simmental beef cattle in Hebei province and to provide a reference for breeding programs. [Method] This study was based on the body weight and size records of 266 Simmental beef cattle in Hebei Tianhe Beef Cattle Breeding Limited Company from 2015 to 2021, which included body weight, body height, hip cross height, body length, chest girth, abdomen circumference, and cannon circumference. [Result] Genetic parameters of body weight and size traits were estimated using AI-REML and EM algorithm of DMU software combined with animal models. The results showed that the heritability estimates of body weight and body size traits were 0.41, 0.41, 0.45, 0.45, 0.48, 0.31, and 0.66, respectively. The genetic correlations between body weight and body size traits ranged from 0.20（body height） to 0.79（chest girth）, and the phenotypic correlations ranged from 0.14（hip cross height） to 0.23（chest girth）. The genetic correlations between body size traits ranged from-0.70（abdomen circumference and cannon circumference） to 0.92（body height and hip cross height）, and the phenotypic correlations ranged from-0.10（abdomen circumference and cannon circumference） to 0.94（body height and hip cross height）. [Conclusion] Body weight and body size traits were high heritability traits, and a strong positive genetic correlation was between body weight and body size traits, except for the cannon circumference. Strengthening the selection and breeding of these traits would help to improve the growth and development performance of Simmental beef cattle.

本试验旨在研究饲粮添加发酵枣粉对高温季节荷斯坦公牛行为、生长性能、抗氧化性能、免疫性能的影响.试验选取60头4～6月龄体重[(200.00±30.28)kg]相近的健康荷斯坦公牛,随机分成4组,每组15头,分别饲喂含0(C组)、5％(L组)、10％(M组)、15％(H组)发酵枣粉的等能等氮的饲粮.预试期7 d,正试期90 d.结果表明:1)当温湿度指数(THI)<78时,添加发酵枣粉显著降低荷斯坦公牛呼吸频率(P<0.05),呼吸频率随着发酵枣粉添加量的增加线性降低.当57<THI<89时,M组荷斯坦公牛躺卧率最高,随着发酵枣粉添加量增加,荷斯坦公牛躺卧率呈二次升高变化(P<0.001).2)C组、L组、M组之间平均日增重无显著差异(P>0.05),但H组平均日增重显著低于其他3组(P<0.05);L组、M组荷斯坦公牛体高增长显著高于C组和H组(P<0.05).3)M组粗蛋白质表观消化率显著高于其他组(P<0.05),粗脂肪表观消化率随着发酵枣粉添加量增加呈线性增加(P<0.001).4)试验第30天,H组荷斯坦公牛血清三碘甲腺原氨酸(T3)的含量显著高于C组(P<0.05),血清T3含量随着发酵枣粉添加量增加而呈线性增加(P=0.017).M组血清总蛋白(TP)含量显著高于对照组(P<0.05),且随着发酵枣粉添加量增加,血清TP含量有二次升高趋势.荷斯坦公牛血清尿素氮(UN)含量随着发酵枣粉添加量增加呈二次下降变化(P=0.010).试验第90天,M组和H组荷斯坦公牛血清热休克因子-1(HSF?1)含量显著高于对照组(P<0.05).5)试验第30天,M组血清白细胞介素-1(IL?1)、白细胞介素-6(IL?6)含量显著降低(P<0.05),H组血清免疫球蛋白A(IgA)含量显著高于其他3组(P<0.05);试验第90天,M组和H组血清IL?1含量显著低于对照组(P<0.05);随着发酵枣粉添加量的增加,血清IgA含量呈线性升高(P=0.019).6)试验第30天,随着发酵枣粉添加量的增加,血清总抗氧化能力(T?AOC)呈线性上升趋势(P=0.137);试验第90天,M组荷斯坦公牛血清中超氧化物歧化酶(SOD)、谷胱甘肽过氧化氢酶(GSH?Px)活性、T?AOC显著提高(P<0.05),同时血清丙二醛(MDA)含量显著降低(P<0.05).综上所述,在本试验条件下,饲粮添加10％发酵枣粉能有效提高高温季节荷斯坦公牛生长性能,降低呼吸频率,提高躺卧率,改善免疫性能,增强奶公牛的抗氧化性能.

为了研究皮下埋植褪黑素(MT)对奶牛超数排卵的影响,本试验选择48头发育良好的荷斯坦牛分为对照组(0mg MT)和试验组(160mg MT、240mg MT),结合CIDR-FSH-PG-GnRH的方案进行超数排卵.通过B超检测卵巢及非手术法冲胚效果,统计超数排卵期间卵巢长、宽、高及回收胚胎情况与胚胎移植妊娠率.结果表明,皮下埋植160mg MT的效果较好,输精时卵泡数显著高于0mg、240mg组(P<0.05),卵巢宽度及高度显著大于0mg、240mg组(P<0.05),冲胚时黄体数显著高于0mg、240mg组(P<0.05),卵泡数、卵巢长度及高度呈增大的趋势,但差异不显著(P>0.05).在胚胎生产及移植方面,显著提高了可用胚胎数及比例、A级胚数及比例、移植妊娠率(P<0.05),显著降低了未受精胚数及比例、退化胚数及比例、B级胚数及比例(P<0.05),冲胚总数、囊胚数、早期囊胚数、桑葚胚数均有上升的趋势(P>0.05).综上,皮下埋植160mg褪黑素能够提高可用胚胎数、胚胎质量和胚胎移植妊娠率,从而提高供体奶牛超数排卵效果.

为了提高奶牛胚胎移植效率,试验研究了黄体酮阴道缓释剂+前列腺素(CIDR+PG7-10组、CIDR+PG8-10 组、CIDR+PG9-10 组、CIDR+PG7-8 组、CIDR+PG7-9 组、CIDR+PG7-10 组)、Ovsynch(079B/G组)和D-Ovsynch(D-079B/G组)3种同期发情-胚胎移植方案对196头育成牛和376头经产牛同期发情的效果和移植妊娠率的影响,并分析了促性腺激素释放激素(GnRH)和布舍瑞林对胚胎移植的效果.根据采用方案不同分为CIDR+PG7-10组、079B/G组、D-079B/G组.结果表明:3种周期发情方案中经产牛发情时间均滞后于育成牛,CIDR+PG7-10组育成牛(100％)和经产牛(94.44％)的发情集中度均好于其他组,且育成牛好于经产牛.各组育成牛和经产牛的移植利用率和妊娠率均差异不显著(P＞0.05),但CIDR+PG7-10组移植妊娠率(48.39％和56.67％)均高于其他组,079B组育成牛(93.55％)和D-079B组经产牛(92.86％)移植利用率高于其他组.育成牛冲胚后第7天同期发情,079B组(95.83％)移植利用率高于CIDR+PG7-10组(76.00％)和079G组(72.00％),且差异显著(P＜0.05),3组间移植妊娠率差异不显著(P＞0.05);随机时间处理时,3组间移植利用率和移植妊娠率均差异不显著(P＞0.05);冲胚后第7天与随机时间处理间各组移植利用率和移植妊娠率均差异不显著(P＞0.05).说明同期发情方案CIDR+PG7-10、079G和079B均适用于育成牛胚胎移植,同期发情方案CIDR+PG7-10、D-079G和D-079B均适用于经产牛胚胎移植,GnRH与布舍瑞林的作用效果差异不显著,产后奶牛首配实施CIDR+PG7-10或D-079同期发情-胚胎移植方案是可行的.