Project description:Puberty is a complex physiological event measured by various indicator traits in genetic improvement programs of beef cattle; thus, developing a more complete understanding of the genes and regulatory pathways and networks involved in puberty will provide knowledge to help improve genetic selection strategies. Herein, we characterized the transcriptome of five reproductive tissues (i.e. hypothalamus, pituitary gland, ovary, uterus, and endometrium) as well as tissues known to be relevant to growth and metabolism needed for cattle to achieve puberty (i.e., longissimus dorsi muscle, fat, and liver). These tissues were collected from pre (PRE)- and post (POST)-pubertal Brangus (3/8 Brahman; Bos indicus x 5/8 Angus; Bos taurus) heifers derived from a population of cattle used to identify QTL associated with fertility traits. In order to exploit the power of complementary omics analyses, PRE and POST puberty co-expression gene networks were constructed by combining the results from RNA-Seq, GWAS, and bovine transcription factors. RNA-Seq of 8 tissues among PRE and POST Brangus heifers revealed 1515 differentiallyexpressed and 943 tissue-specific genes within the 17,832 genes confirmed by metrics of RNA-Seq analysis. Combining the results from RNA-Seq and GWAS indentified a total of 25 QTL associated to heifer fertility. The hypothalamus experienced the most notable up-regulation of genes via puberty. Complementary omics procedures revealed 2,450 co-expressed genes across the 8 tissues relative to puberty. The PRE network had 372,861 connections whereas the POST network had 328,357 connections. A sub-network from this process revealed key transcriptional regulators (i.e., PITX2, FOXA1, TSG1D1, DACH2, LHX4, PROP1 and SIX6). Results from multiples sources of omics data will facilitate the design of breeding strategies to improve fertility in Bos indicus-influenced composite cattle. Sixty-one samples from PRE and POST pubertal composite beef heifers were analyzed with RNA-Seq. The transcriptome of five reproductive tissues (i.e. hypothalamus, pituitary gland, ovary, uterus, and endometrium) as well as tissues known to be relevant to metabolism andbody morphometrics needed for cattle to achieve puberty (i.e.,) was characterized. These tissues were collected from pre (PRE)- and post (POST)-pubertal Brangus (3/8 Brahman x 5/8 Angus) heifers derived from a population of cattle used to identify QTL associated with fertility. Total RNA was purified using a Trizol protocol (Invitrogen, Carlsbad, CA). Sequencing libraries were made using TruSeq RNA Sample Preparation kit of Illumina (San Diego, CA).

Project description:Background: Infertility is a longstanding limitation in livestock production with important economic impact for the cattle industry. Female reproductive traits are polygenic and lowly heritable in nature, thus selection for fertility is challenging. Beef cattle operations leverage estrous synchronization in combination with artificial insemination (AI) to breed heifers and benefit from an early and uniform calving season. A couple of weeks following AI, heifers are exposed to bulls for an opportunity to become pregnant by natural breeding (NB), but they may also not become pregnant during this time period. Focusing on beef heifers, in their first breeding season, we hypothesized that: a- at the time of AI, the transcriptome of peripheral white blood cells (PWBC) differs between heifers that become pregnant to AI and heifers that become pregnant late in the breeding season by NB or do not become pregnant during the breeding season; and b- the ratio of transcript abundance between genes in PWBC classifies heifers according to pregnancy by AI, NB, or failure to become pregnant. Results: We generated RNA-sequencing data from 23 heifers from two locations (A: six AI-pregnant and five NB-pregnant; and B: six AI-pregnant and six non-pregnant). After filtering out lowly expressed genes, we quantified transcript abundance for 12,538 genes. The comparison of gene expression levels between AI-pregnant and NB-pregnant heifers yielded 18 differentially expressed genes (DEGs) (ADAM20, ALDH5A1, ANG, BOLA-DQB, DMBT1, FCER1A, GSTM3, KIR3DL1, LOC107131247, LOC618633, LYZ, MNS1, P2RY12, PPP1R1B, SIGLEC14, TPPP, TTLL1, UGT8, eFDR≤0.02). The comparison of gene expression levels between AI-pregnant and non-pregnant heifers yielded six DEGs (ALAS2, CNKSR3, LOC522763, SAXO2, TAC3, TFF2, eFDR≤0.05). We calculated the ratio of expression levels between all gene pairs and assessed their potential to classify samples according to experimental groups. Considering all samples, relative expression from two gene pairs correctly classified 10 out of 12 AI-pregnant heifers (P=0.0028) separately from the other 11 heifers (NB-pregnant, or non-pregnant). Conclusion: The transcriptome profile in PWBC, at the time of AI, is associated with the fertility potential of beef heifers. Transcript levels of specific genes may be further explored as potential classifiers, and thus selection tools, of heifer fertility.

Project description:A better understanding of impacts of nutrition during pre- weaning and post- weaning period is needed in order to design feeding strategies that optimize lifetime productivity. Therefore, the objectives of the present study were three-fold: to evaluate nutrition-induced changes of 1) growth from birth to first calving in heifers, 2) its impact on first-lactation milk yield and composition and 3) evaluate nutrition-induced changes in gene expression of mammary gland in Parda de Montaña heifers. Sixteen Parda de Montaña heifers, were randomly but equally assigned at birth to one of four management strategies, in a 2 x 2 factorial experiment. In the pre-weaning period (0-6 months of age), all the heifers suckled their dams twice daily for 30 minutes. Half of the heifers (n=8) were supplemented a starter concentrate (CON) while the other half only had access to their dam’s milk (NOCON). In the post-weaning period (6-15 months), half of the heifers of each pre-weaning feeding treatment received alfalfa hay ad libitum plus concentrates, with a different forage to concentrate ratio (F:C), 67:33 (67F:33C) or 87:13 (87F:13C). Plasma metabolites and hormones concentration at weaning was determined, and cows and their calves weigh was recorded once/week throughout the first lactation, and their ADG was calculated. Milk composition and quantity was determined during the first 4 months of lactation. Mammary tissue samples were taken by biopsy at weaning at the end of first lactation. RNA mammary gland samples (n=16, 8 samples from each treatment) were analyzed by using Bovine Gene 1.1 ST Array Strip. The results of the present study showed that heifers that received concentrate during pre- weaning period had greater BW at weaning when compared to NOCON heifers. Concentrate supplementation during the pre-weaning period increased heifers’ weight gains in the pre-weaning period (P < 0.001) but decreased weight gains in the post-weaning period (P < 0.01) and during pregnancy (P < 0.05). In addition, CON cows had lower milk production throughout the 4 months of the first lactation when compared with NOCON (P < 0.01). Moreover CON cows had decreased milk crude protein, crude fat, lactose, extract and casein content in their first lactation. In addition, cows that received concentrate during pre- weaning period showed greater SCC at the third and fourth month of lactation. Different gene expression patterns were found between CON and NOCON animals. Overall, concentrate supplementation at pre- weaning resulted in up –regulation of genes related with immune response and chemokine activity, suggesting that these animals might be in a compromised immune status, probably being at greater risk to develop mastitis in the later periods.

Dataset Information

Transcriptome related to pubertal development in Brahman heifers

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