Phenotypic population screen identifies a new mutation in bovine DGAT1 responsible for unsaturated milk fat.

Selective breeding has strongly reduced the genetic diversity in livestock species, and contemporary breeding practices exclude potentially beneficial rare genetic variation from the future gene pool. Here we test whether important traits arising by new mutations can be identified and rescued in highly selected populations. We screened milks from 2.

Genetic ancestry modifies fatty acid concentrations in different adipose tissue depots and milk fat.

The objective of this study was to determine the effect of cow genetic strain on fatty acid (FA) profiles in adipose tissue and milk. Adipose samples from two subcutaneous (shoulder and tail-head) and three visceral (kidney channel, mesenteric and omental) depots were obtained post mortem from New Zealand (NZ; n = 8) and North American (NA; n = 8) Holstein-Friesian cows. At the time of slaughter cows were in similar body condition (NZ: 4.

The effect of temperament and responsiveness towards humans on the behavior, physiology and milk production of multi-parous dairy cows in a familiar and novel milking environment.

The objectives of this study were to investigate whether; 1) temperament or 2) behavioral responsiveness to humans, can affect the behavior, physiology and productivity of dairy cows being milked in a familiar and novel milking environment. Temperament of multi-parous cows was defined based on exit time from a restraint device, as High Responders (HR; n=10), Medium Responders (MR; n=10) or Low Responders (LR; n=10). The behavioral response of cows to humans was assessed using four tests: restraint, exit speed, avoidance distance test and a voluntary approach test.

Effects of divergent Holstein-Friesian strain and diet on diurnal patterns of plasma metabolites and hormones.

Commonly measured metabolite and hormone concentrations used to describe the metabolic status of lactating cows undergo diurnal variation resulting in distinct patterns. Studies have shown that feeding events can modulate these diurnal patterns as cows respond to the nutrient intake. What is less clear is the extent to which cow genetics and diet interact to modify the diurnal patterns of specific nutritionally related metabolites and hormones.

Fecal glucocorticoid metabolites as a measure of adrenal activity in dairy cattle.

The feasibility of monitoring acute adrenal activity in New Zealand dairy cattle by measuring fecal glucocorticoid metabolites was investigated. Fecal glucocorticoid measurement has potential as an indicator of adrenal activity and animal stress because sampling is relatively noninvasive, does not interfere with the stress response itself, and permits on-farm monitoring. Fecal samples were collected from dairy cattle following ACTH challenge and exposure to stressors (novel environment, transport).