3 research outputs found
Associations among milk production traits and glycosylated haemoglobin in dairy cattle: importance of lactose synthesis potential
Abstract Glucose is the major precursor of lactose synthesis in the mammary gland.
Lactose the major carbohydrate and osmolyte of milk, controls milk volume and its
concentration. Glycosylated haemoglobin (HbG) is a retrospective measure of mean blood
glucose level and it is largely unaffected by recent physiological conditions and
environmental events. The purposes of this study were to determine the correlations
between lactose traits and other milk production traits in dairy cattle and to investigate
whether HbG level can be correlated with milk and lactose production traits. Here, HbG
percentage, milk and lactose production traits including milk yield, lactose, protein, SNF,
total solid and fat percentages and yields were measured in 485 second calved Iranian
Holstein cattle. Statistically significant negative correlations were established between HbG
and milk yield (r=−0.88), lactose yield (r=−0.83), SNF yield (r=−0.81), protein yield
(r=−0.79) and total solid yield (r=−0.74). Positive correlations were established between
lactose yield and milk (r=0.96), protein (r=0.81), SNF (r=0.92) and total solid (r=0.79)
yields. The negative correlation between HbG and milk and total lactose production is probably related to the higher glucose demands in the lactating mammary gland of more
productive cows. The positive correlation between lactose yield and milk, protein, SNF and
total solid yield indicates that the level of lactose synthesis influences milk production traits
in ways other than merely via its osmolytic action
Association of polymorphism of the ß(1, 4)-galactosyltransferase-I gene with milk production traits in Holsteins
The b(1,4)-galactosyltransferase-I gene (b4galt1) encodes the catalytic part of the enzyme lactose synthase, responsible of lactose synthesis in the mammary gland. The
complete coding region of the gene was screened for the presence of allelic variation among a sample of 1,200 Iranian
Holstein cows, using PCR-SSCP technique followed by sequencing. Nine polymorphic nucleotide sites were identified-
one in exons I and VI, two in exons II and III, and three in exon V. Altogether 18 different genotypes were assigned.
Statistical analysis showed that the genotypes of B4GALT1 significantly affect milk, lactose, protein and total solid
productions in both the first and second lactation (P\0.001). Variance component analysis considering restricted
maximum likelihood showed that the major factor making differences in milk, lactose, protein and total solid productions
among the studied cow is the b4galt1 genotype. We concluded that the b4galt1 gene is potentially associated with milk production traits in dairy cows and should be
considered for further studies on genetics of the milk production traits
Polymorphisms of the beta-1,4 galactosyltransferase-I gene in Holsteins
The scope of this study was to identify sequence polymorphisms in the β-1,4-
galactosyltransferase-I gene (B4GALT1), the gene which encodes the catalytic part of lactose
synthase enzyme. Exons of the gene were scanned for the presence of allelic variation among a
sample of 400 Iranian Holsteins, using the single strand conformation polymorphism technique
followed by sequencing. Nine polymorphic nucleotide sites and 16 different genotypes of
B4GALT1 were identified. We concluded therefore that the β-1,4-galactosyltransferase-I gene
was polymorphic in Holsteins. Considering the biological roles of the B4GALT1 gene, we suggest
that further studies are critical to investigate the biological effects of the SNPs reported in this study