Cholesterol deficiency carriers have lowered serum cholesterol and perform well at an elite cattle show

Cholesterol deficiency (CD) in Holstein cattle results from an insertion in the APOB gene, which traces to the bull Maughlin Storm and was spread to elite show cattle largely through his grandson Braedale Goldwyn. Calves that are homozygous for CD can neither transport dietary fat from the gut nor synthesize low-density lipoproteins, and they perish before 6 mo of age. The mutation may have a partially dominant effect, with lowered cholesterol in heterozygous animals. Our aims were to evaluate serum cholesterol in heterozygous animals, evaluate daily phenotypic records of lactating CD carriers, and determine whether CD carrier status is associated with show ring success. Blood was collected on a single date in May 2018 from 12 carriers and 14 controls and 1 yr later from 17 carriers (7 repeated for 2018) and 27 controls (6 repeated from 2018); animals ranged in age from 14 to 84 mo and varied in stage of lactation and pregnancy status. Serum samples were analyzed for cholesterol concentration (mg/dL) and results were analyzed using mixed models that included linear and quadratic effects of days in milk and days carried calf. Daily phenotypic records of milk yield, milking time, milk conductivity, activity, and body weight were compared between carriers and controls. Additionally, the CD carrier status of cows that were sired by known CD carriers and had available genotypes was recorded. Cows placing in the top 5 and top 10 of their classes at World Dairy Expo between the years of 2006 and 2019 were included in our analysis. Chi-squared tests for equal proportions were evaluated to determine whether the following were associated with CD status: placing in the top 10 with repeated placings from the same cow included, placing in the top 5 with repeated placings, top 10 cows considering individuals only once, and top 5 cows considering individuals only once. Control animals (noncarriers) had significantly higher serum cholesterol (116.21 ± 6.45 mg/dL) than CD carriers (90.15 ± 7.49 mg/dL). There was no difference between carriers and controls in milk yield, milk conductivity, or activity. However, CD carriers had shorter milking times and lower body weights than their herdmates. Further, there were more CD carriers in the top 5 and more carriers tended to place in the top 10 at World Dairy Expo when repeated placings were included. These data support observations that CD is partially dominant and indicate that CD carriers display other phenotypic differences from their herdmates that may give them a small advantage at elite cattle shows.