Early luteal concentrations of progesterone were a reasonable predictor of concentrations on day seven and could be used to predict animals at risk of embryo loss.
Recent trials have revealed that fertilisation failure occurred in 53.5% of dairy animals (67.5% of cows, 18.8% of heifers) – a figure that is greater than previous estimates of between 10 and 20%. And the work also revealed that energy status in early lactation significantly affected fertilisation rate.
There is a detrimental effect of a bad calving on cows’ subsequent fertility and milk production. When calving difficulty increases, fertility declines and milk yield in the first stage of lactation also decreases.
It is not genetic merit for milk production or breed that has an adverse impact on embryo quality, but rather that a variety of factors associated with milk production, such as metabolism and nutritional management, induce hostile conditions that prevent optimal embryo development.
Dairy cow fertility is negatively associated with both genetic merit and level of production, and various other factors including season of calving, lactation number and difficult calvings.
Selection of the best dairy animals for breeding could be made on the basis of juvenile predictors through the use of genotyping coupled with phenotypic profiling of type traits and metabolic parameters.
Take Home Message: Selection for increased milk yield and lower somatic cell counts based on 305-d lactation data is resulting in a shift in peak yield, a flatter lactation curve and lower cell counts in mid-late lactation.
The rate of change of milk predicted transmitting abilities (PTAs) at various days in milk (DIM) is greatest around [...]
Take Home Message: Selecting for milk yield decreases fertility and body condition score.
Selecting for increased milk production leads to a deterioration in genetic merit for fertility and condition score. That was the unequivocal conclusion of a study carried out by geneticists at SAC on the college’s Langhill herd, which was under maximum selection for milk [...]
Take Home Message: Selecting for carcass conformation in dairy cows will reduce milk yield but improve fertility, with little effect on somatic cell count or lifespan.
Selection on an index that improves carcass conformation of Holstein Friesian beef by 0.1 of a unit will lead to a reduced rate of improvement in production traits and an [...]
Take Home Message: Earlier turnout for 2-3h per day in the Spring will decrease total mixed ration intake and have no effect on milk yield or composition, improving margin over feed by 50p/cow/day
Allowing access to grazing for two hours per day in the spring had no effect on milk yield or milk composition in autumn [...]
