Variance components and correlations of female fertility traits in Chinese Holstein population

Background: The objective of the present study was to estimate(co)variance components of female fertility traits in Chinese Holsteins, considering fertility traits in different parities as different traits. Data on 88,647 females with 215,632 records(parities) were collected during 2000 to 2014 from 32 herds in the Sanyuan Lvhe Dairy Cattle Center, Beijing, China. The analyzed female fertility traits included interval from calving to first insemination, interval from first to last insemination, days open, conception rate at first insemination, number of inseminations per conception and non-return rates within 56 days after first insemination.Results: The descriptive statistics showed that the average fertility of heifers was superior to that of cows. Moreover,the genetic correlations between the performances of a trait in heifers and in cows were all moderate to high but far from one, which suggested that the performances of a trait in heifers and cows should be considered as different but genetically correlated traits in genetic evaluations. On the other hand, genetic correlations between performances of a trait in different parities of cows were greater than 0.87, with only a few exceptions, but variances were not homogeneous across parities for some traits. The estimated heritabilities of female fertility traits were low; all were below 0.049(except for interval from calving to first insemination). Additionally, the heritabilities of the heifer interval traits were lower than those of the corresponding cow interval traits. Moreover, the heritabilities of the interval traits were higher than those of the threshold traits when measuring similar fertility functions. In general, estimated genetic correlations between traits were highly consistent with the biological categories of the female fertility traits.Conclusions: Interval from calving to first insemination, interval from first to last insemination and non-return rates within 56 days after first insemination are recommended to be included in the selection index of the Chinese Holstein population. The parameters estimated in the present study will facilitate the development of a genetic evaluation system for female fertility traits to improve the reproduction efficiency of Chinese Holsteins.

Effects of melatonin implantation on carcass characteristics, meat quality and tissue levels of melatonin and prolactin in Inner Mongolian cashmere goats

Background: Implantation of goats with melatonin can induce cashmere growth and significantly increase cashmere production performance. However, the impact of melatonin implantation on the carcass characteristics,meat quality and related hormone levels in muscle and viscera of cashmere goats has not been studied. This experiment was conducted to determine the effects of melatonin implantation of cashmere goats during the nongrowing period on meat quality and related hormone levels in the tissues. It aimed to provide a theoretical basis for the practical application of melatonin in cashmere goat production systems.Results: Melatonin implantation(2 mg/kg live weight) had no influence(P > 0.05) on daily weight gain, carcass weight, dressing percentage, loin muscle area, or the p H, moisture level, crude fat(except for Gluteus muscle) and amino acid content of muscles of cashmere goats. After implantation for 1 month, shear force of Longissimus dorsi and water loss rate of Longissimus dorsi and Biceps femoris of cashmere goats were increased(P < 0.05), whereas the cooking yield of Gluteus muscle was reduced(P < 0.05). The melatonin treatment decreased(P < 0.05) muscle crude protein, Gluteus muscle crude fat and ∑n-3 PUFA content and decreased(P < 0.05) ∑n-6 PUFA content.However, after 2 months of implantation most of these effects had resolved. Melatonin implantation had no effect(P >0.05) on the melatonin or prolactin contents of kidney, heart, spleen, liver, Longissimus dorsi, Biceps femoris and Gluteus muscles. Melatonin content of lung tissue was lowered(P < 0.05) and that of prolactin was elevated(P < 0.05) by the melatonin implantation.Conclusion: This study has shown little impact of melatonin implantation of cashmere goats on carcass quality. A few meat quality indices i.e., shear force, water loss rate, ∑n-3 PUFA, ∑n-6 PUFA, and crude protein content of Longissimus dorsi;water loss rate, cooking yield and crude protein content of Biceps femoris;ether extract, crude protein content of Gluteus;were affected briefly(at 1 month of implantation) but these effects were not evident after 2 months of implantation.There was little effect of the melatonin treatments on tissue levels of melatonin or prolactin except in lung.

Genomic and transcriptomic analyses enable the identification of important genes associated with subcutaneous fat deposition in Holstein cows

Subcutaneous fat deposition has many important roles in dairy cattle,including immunological defense and mechanical protection.The main objectives of this study are to identify key candidate genes regulating subcutaneous fat deposition in high-producing dairy cows by integrating genomic and transcriptomic datasets.A total of 1654 genotyped Holstein cows are used to perform a genome-wide association study(GWAS)aiming to identify genes associated with subcutaneous fat deposition.Subsequently,weighted gene co-expression network analyses(WGCNA)are conducted based on RNA-sequencing data of 34 cows and cow yield deviations of subcutaneous fat deposition.Lastly,differentially expressed(DE)m RNA,lnc RNA,and differentially alternative splicing genes are obtained for 12 Holstein cows with extreme and divergent phenotypes for subcutaneous fat deposition.Forty-six protein-coding genes are identified as candidate genes regulating subcutaneous fat deposition in Holstein cattle based on GWAS.Eleven overlapping genes are identified based on the analyses of DE genes and WGCNA.Furthermore,the candidate genes identified based on GWAS,WGCNA,and analyses of DE genes are significantly enriched for pathways involved in metabolism,oxidative phosphorylation,thermogenesis,fatty acid degradation,and glycolysis/gluconeogenesis pathways.Integrating all findings,the NID2,STARD3,UFC1,DEDD,PPP1R1B,and USP21 genes are considered to be the most important candidate genes influencing subcutaneous fat deposition traits in Holstein cows.This study provides novel insights into the regulation mechanism underlying fat deposition in high-producing dairy cows,which will be useful when designing management and breeding strategies.

Weighted single-step GWAS and RNA sequencing reveals key candidate genes associated with physiological indicators of heat stress in Holstein cattle

Background: The study of molecular processes regulating heat stress response in dairy cattle is paramount for developing mitigation strategies to improve heat tolerance and animal welfare. Therefore, we aimed to identify quantitative trait loci(QTL) regions associated with three physiological indicators of heat stress response in Holstein cattle, including rectal temperature(RT), respiration rate score(RS), and drooling score(DS). We estimated genetic parameters for all three traits. Subsequently, a weighted single-step genome-wide association study(WssGWAS) was performed based on 3200 genotypes, 151,486 phenotypic records, and 38,101 animals in the pedigree file. The candidate genes located within the identified QTL regions were further investigated through RNA sequencing(RNA-seq) analyses of blood samples for four cows collected in April(non-heat stress group) and four cows collected in July(heat stress group).Results: The heritability estimates for RT, RS, and DS were 0.06, 0.04, and 0.03, respectively. Fourteen, 19, and 20 genomic regions explained 2.94%, 3.74%, and 4.01% of the total additive genetic variance of RT, RS, and DS, respectively. Most of these genomic regions are located in the Bos taurus autosome(BTA) BTA3, BTA6, BTA8, BTA12, BTA14, BTA21, and BTA24. No genomic regions overlapped between the three indicators of heat stress, indicating the polygenic nature of heat tolerance and the complementary mechanisms involved in heat stress response. For the RNA-seq analyses, 2627 genes were significantly upregulated and 369 downregulated in the heat stress group in comparison to the control group. When integrating the WssGWAS, RNA-seq results, and existing literature, the key candidate genes associated with physiological indicators of heat stress in Holstein cattle are: PMAIP1, SBK1, TMEM33, GATB, CHORDC1, RTN4IP1, and BTBD7.Conclusions: Physiological indicators of heat stress are heritable and can be improved through direct selection. Fifty-three QTL regions associated with heat stress indicators confirm the polygenic nature and complex genetic determinism of heat tolerance in dairy cattle. The identified candidate genes will contribute for optimizing genomic evaluation models by assigning higher weights to genetic markers located in these regions as well as to the design of SNP panels containing polymorphisms located within these candidate genes.