The stress of high milk production, along with increasing herd size and changes in facilities and management, has made fertility one of the main focuses of genetic improvement today. In the US, the reduction in calving rate to first service and the impact of this decrease in fertility on the Holstein breed, mainly in the last 20 years, is of major concern [27]. Figure 1 shows the clear trend fo...

Decreased fertility in dairy cows is widespread and economically undesirable. Current management strategies to prevent decreased fertility are exploiting the close relationship between negative energy balance in transition cows and subsequent decreased fertility. However, there is a continuous need for more information regarding the effects of different strategies on fertility. This thesis eval...

Milk yield per cow has more than doubled in the previous 40 years and many cows now produce more than 20,000 kg of milk per lactation. The increase in production should be viewed with concern because: i) the increase in milk yield has been accompanied by declining fertility, increasing leg and metabolic problems and declining longevity; ii) there are unfavourable genetic correlations between mi...

The establishment and maintenance of pregnancy in lactating dairy cows is a complex biological event that is influenced by a multitude of factors, from the reproductive biology of the cow to managerial aspects of the dairy farm. It is often mentioned in the scientific literature that fertility in dairy cows has declined concurrent with major advances in milk production. Some of this decline is ...

The efficiency of milk production in pasture-based systems is heavily influenced by calving pattern, necessitating excellent reproductive performance in a short-breeding season. Where grazed pasture is the major component of the diet, cows are underfed relative to their intake potential. The cow responds by reducing milk output, but fertility is generally better than high intake confinement sys...

A national fertility evaluation was developed based on pregnancy rate, which measures the percentage of nonpregnant cows becoming pregnant within each 21-d opportunity period. Data for evaluation are days open, which are calculated as date pregnant minus previous calving date. Date pregnant is determined from last reported breeding or from subsequent calving minus expected gestation length. Suc...

Genomic selection offers the opportunity to improve female fertility in the Northern Australian beef herd. However, genomic predictions for a number of female fertility traits derived solely from the small number of female fertility records collected thus far are only of modest accuracy. In this study measures of Brahman male reproduction were used jointly with the female records, increasing th...

In the 1970s, bovine embryo transfer (ET) shifted from research in a laboratory environment to commercialization of this technology for beef producers. With the quarantine requirements and expense of importing Continental breeds of cattle from Europe, embryo transfer became the logical means to reproduce greater numbers of these animals at a lower cost. The ET industry grew very rapidly and soo...

Reproduction continues to be a critical component to maintain a dairy farm economically viable. For every farm and for every cow, there is an optimum time for pregnancy, which is mostly influenced by level of production, persistency of lactation, and parity. In general, as production decreases, lactation number increases, and persistency of lactation decreases, cows should be bred sooner postpa...