A genetic evaluation of some serum and milk production traits of dairy cattle

This study was initiated to evaluate the genetic aspects of certain serum constituents and milk production traits of dairy cattle. The population under study was located on commercial dairy farms in the upper Fraser Valley region of British Columbia. Serum samples from 545 animals were used in the analysis. This represented 27 sire groups with approximately 20 samples per group. Serum constituents analysed were calcium, inorganic phosphate, glucose, BUN, uric acid, cholesterol, total protein, albumin, bilirubin, alkaline phosphatase, SGOT, creatinine, triglycerides, sodium, potassium, chloride, bicarbonate, thyroxine and amylase, Production traits studied were milk, milk fat and milk protein for both first lactation and the lactation in progress at time of serum sampling. Several effects were recognized as having a potentially significant influence on the traits under study. Herd effects were expected to be significant for all traits. Seasonal effects, estimated by sampling in summer and winter seasons, were considered as potentially important. An interaction between herds and seasons was deemed important and included in adjustments for all traits. The covariables used in the analyses were unique to the serum and production traits. Age at lactation start and stage of lactation at time of bleeding were the covariables appropriate for serum traits, while age at lactation start and length of lactation were appropriate covariables for the production traits. All effects were evaluated by least squares techniques. The traits under study were adjusted by the least squares constants with the resulting corrected data subjected to the genetic analysis. The traits that were discerned to have a significant heritability included all the production traits and the following serum constituents: creatinine (0.32), alkaline phosphatase (0.30), amylase (0.20), potassium (0.13), and albumin (0.08). SGOT and BUN were also deemed of interest with her inabilities of 0.05 and 0.05, respectively. Genetic correlations that existed among the traits were also evaluated. The evaluation of these correlations was carried out in light of the magnitude of the correlation and the relative magnitude of the associated standard errors. The genetic correlations judged reliable were as follows: creatinine correlated highly and negatively with both milk fat and milk protein for both first and current lactations. Alkaline phosphatase correlated highly and negatively with all production traits for both lactations. Potassium and albumin exhibited reliable, positive correlations with milk production alone. Genetic correlations were also examined among serum traits in order to elucidate common underlying genotypes. SGOT exhibited a positive correlation with amylase, potassium and albumin, and a negative correlation with alkaline phosphatase. BON was negatively correlated with amylase and positively correlated with albumin. Creatinine was correlated positively with alkaline phosphatase, and amylase, alkaline phosphatase correlated negatively with amylase and potassium. Potassium was positively correlated with albumin. This study estimated and tabulated the genetic parameters involving some serum and production traits in dairy cattle, further, it reduced the total number of serum constituents to a subset which demonstrated a genetic component or a genetic involvement in other traits.