Genome-wide association analysis of feed intake and residual feed intake in Nellore cattle.

BACKGROUND: Feed intake plays an important economic role in beef cattle, and is related with feed efficiency, weight gain and carcass traits. However, the phenotypes collected for dry matter intake and feed efficiency are scarce when compared with other measures such as weight gain and carcass traits. The use of genomic information can improve the power of inference of studies on these measures, identifying genomic regions that affect these phenotypes. This work performed the genome-wide association study (GWAS) for dry matter intake (DMI) and residual feed intake (RFI) of 720 Nellore cattle (Bos taurus indicus). RESULTS: In general, no genomic region extremely associated with both phenotypic traits was observed, as expected for the variables that have their regulation controlled by many genes. Three SNPs surpassed the threshold for the Bonferroni multiple test for DMI and two SNPs for RFI. These markers are located on chromosomes 4, 8, 14 and 21 in regions near genes regulating appetite and ion transport and close to important QTL as previously reported to RFI and DMI, thus corroborating the literature that points these two processes as important in the physiological regulation of intake and feed efficiency. CONCLUSIONS: This study showed the first GWAS of DMI to identify genomic regions associated with feed intake and efficiency in Nellore cattle. Some genes and QTLs previously described for DMI and RFI, in other subspecies (Bos taurus taurus), that influences these phenotypes are confirmed in this study.

Supplemental fish oil does not alter immune competence or the pathophysiological response to an intramammary infusion of endotoxin in peri-partum multiparous Holstein cows.

The objective was to determine the effects of supplementing the diet with fish oil during the peri-partum period on the immune competence and the pathophysiological response to a lipopolysaccharide-induced mastitis challenge. Multiparous Holstein cows (n=30) were completely randomized to one of two treatments at 3 weeks pre-partum. Treatments differed only in the source of supplemental lipid and included either Energy Booster or fish oil. Treatment diets were fed from -21 d relative to expected date of parturition until 10 d post partum. Treatments were fed as a bolus prior to the a.m. feeding. The dose of lipid during the pre-partum period was 250 g/d, whereas the amount of lipid supplemented post partum was adjusted to the level of intake, approximately 0.92% of the previous day's dry matter intake. Ex-vivo analyses of immune competence were measured including the antimicrobial activity of whole blood against Escherichia coli, Salmonella typhimurium and Candida albicans as well as the production of interferon-gamma by peripheral blood mononuclear cultures. At 7 days in milk cows were infused with 100 microg of Esch. coli lipopolysaccharide into one rear quarter. Supplementing fish oil increased plasma concentrations of eicosapentaenoic and docosahexaenoic acids, but had no affect on the proportions of arachidonic acid at calving. Fish oil did not influence the production of interferon-gamma or the antimicrobial activity of whole blood against any of the microorganisms. Furthermore, fish oil had no ameliorative effect on either the local or the systemic acute phase response following an intramammary lipopolysaccharide challenge in early lactating Holstein cows. Supplementing fish oil in the diet of peri-partum cows will not protect them from deleterious effects of an excessive acute phase response.

Bovine NR1I3 gene polymorphisms and its association with feed efficiency traits in Nellore cattle.

The Nuclear receptor 1 family I member 3 (NR1I3), also known as the Constitutive Androstane Receptor (CAR), was initially characterized as a key regulator of xenobiotic metabolism. However, recent biochemical and structural data suggest that NR1I3 is activated in response to metabolic and nutritional stress in a ligand-independent manner. Thus, we prospected the Bovine NR1I3 gene for polymorphisms and studied their association with feed efficiency traits in Nellore cattle. First, 155 purebred Nellore bulls were individually measured for Residual Feed Intake (RFI) and the 25 best (High Feed Efficiency group, HFE) and the 25 worst animals (Low Feed Efficiency group, LFE) were selected for DNA extraction. The entire Bovine NR1I3 gene was amplified and polymorphisms were identified by sequencing. Then, one SNP different between HFE and LFE groups was genotyped in all the 155 animals and in another 288 animals totalizing 443 Nellore bulls genotyped for association of NR1I3 SNPs with feed efficiency traits. We found 24 SNPs in the NR1I3 gene and choose a statistically different SNP between HFE and LFE groups for further analysis. Genotyping of the 155 animals showed a significant association within SNP and RFI (p = 0.04), Residual Intake and BW Gain (p = 0.04) and Dry Matter Intake (p = 0.01). This SNP is located in the 5'flanking promoter region of NR1I3 gene and different alleles alter the binding site for predicted transcriptional factors as HNF4alpha, CREM and c-MYB, leading us to conclude that NR1I3 expression and regulation might be important to feed efficiency.