Diacylglycerol-O-acyltransferase (DGAT1) gene encodes the rate-limiting enzyme 
of triglyceride synthesis. A polymorphism in this gene, DGAT1 K232A, has been 
associated with milk production and composition in taurine breeds. However, this 
polymorphism is not a good tool for ascertaining the effects of this QTL in Bos 
indicus (Zebu), since the frequency of the DGAT1 232A allele is too low in these 
breeds. We sequenced the 3'-untranslated region of DGAT1 gene in a sample of 
bulls of the breeds Guzerá (Bos indicus) and Holstein (Bos taurus) and, using in 
silico analysis, we searched for genetic variation, evolutionary conservation, 
regulatory elements, and possible substitution effects. Six single nucleotide 
(SNPs) and one insertion-deletion (INDEL) polymorphisms were found in the Guzerá 
bulls. Additionally, we developed a preliminary association study, using this 
INDEL polymorphism as a genetic marker. A significant association was detected 
(P ≤ 0.05) between the INDEL (DGAT1 3'UTR INDEL) and the breeding values (BV) 
for protein, fat, and milk yields over a 305-day lactation period. The DGAT1 3' 
UTR INDEL genotype I/I (I, for insertion) was associated with lower BVs (-38.77 
kg for milk, -1.86 kg for fat, and -1.48 kg for protein yields), when compared 
to the genotype I/D (D, for deletion). I/D genotype was lower D/D genotype 
(-34.98 kg milk, -1.73 kg fat, and -1.09 kg protein yields). This study reports 
the first polymorphism of DGAT1 3'UTR in the Guzerá breed, as well as its 
association with BV for milk protein, fat, and milk yields.