Vitamin A and intramuscular fat deposition: a nutrigenetic investigation in beef cattle
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Vitamin A restriction has been associated with increased marbling in beef cattle. The purpose of this study was to investigate a possible nutrigenetic mechanism leading to this increase in intramuscular fat. Four genes involved in the vitamin A pathway were examined for genetic polymorphisms that could alter mRNA expression or protein structure. A total of fourteen SNPs were found in bovine alcohol dehydrogenase 1C (ADH1C), aldehyde dehydrogenase 1A1 (ALDH1A1), peroxisome proliferator-activated receptor (PPAR), and retinol binding protein 4 (RBP4). Five of these SNPs were examined for associations with production and carcass traits in a previously reported population of 400 crossbred steers. ALDH1A1 c.*27C>T was significantly associated with backgrounding average daily gain (P<0.05) however no associations were found between ADH1C c.-64T>C, ADH1C c.967C>T, ALDH1A1 c.*109A>G, or PPAR c.1344G>T with any of the parameters measured. A nutritional study was performed to examine the interaction between ADH1C c.-64T>C and vitamin A restriction on production and carcass traits in cattle. It was hypothesized that a phenotypic effect would be observed only when vitamin A was restricted. An initial population of 450 black Angus cross steers were genotyped at ADH1C c.-64T>C and from that population 130 steers (50 TT, 50 CT, and 30 CC) were randomly selected for use in the vitamin A restriction study. They were backgrounded for three months on a low -carotene diet and finished for five months on a diet that did not contain supplemental vitamin A. During the finishing period the steers were treated with monthly boluses of either 0 IU (unsupplemented) or 750,000 IU (supplemented) supplemental vitamin A. Liver and fat biopsies were obtained at the start and end of finishing from a subgroup of five steers per genotype per treatment to assess vitamin A status and measure gene expression. Marbling score was significantly greater (P<0.05) in unsupplemented steers. A significant interaction was found between genotype and vitamin A supplementation on intramuscular fat content. Within the unsupplemented treatment, TT steers had significantly greater intramuscular fat than CC steers. Within TT steers, unsupplemented steers had significantly greater intramuscular fat than supplemented animals. Expression of ADH1C in the liver was significantly higher in TT steers than CC steers. ADH1C c.-64T>C in combination with reduced vitamin A supplementation could potentially be implemented in marker-assisted management to maximize intramuscular fat deposition in finishing cattle.
DegreeDoctor of Philosophy (Ph.D.)
DepartmentAnimal and Poultry Science
SupervisorBuchanan, Fiona C.
CommitteeSchmutz, Sheila S.; McKinnon, John J.; Laarveld, Bernard; Palmer, Colin
Copyright DateNovember 2011