Heat stress during the dry period is known to compromise udder growth, thus negatively affecting milk yield in subsequent lactations. Cooling during the late dry period, when mammary tissue proliferates, is a common management practice. However, it neglects udder involution (or return to a pre-lactation state) during the early dry period, a process that is accomplished by both apoptosis and autophagy (self-destruction of damaged cells). Yenny Ramirez-Lee reported on work at the University of Florida that was designed to evaluate the effect of heat stress on mammary gland autophagy during the early dry period. 

Holstein cows were dried off 45 days before expected calving and randomly assigned to one of two treatments: heat stress (HT) or cooling (CL). All cows were housed in the same barn during the dry period, but only the stall area for CL cows was equipped with soakers and fans.

The work confirmed that both groups of cows were exposed to significant heat stress. However, the cooling system effectively alleviated heat stress in cooled cows by decreasing the rectal temperature and respiration rate. Their data suggests that cows undergoing chronic heat stress throughout the entire dry period (1) lack the autophagic activity in the early dry period needed for mammary gland involution, and (2) lack a subsequent attenuation of autophagy, which may hinder mammary gland growth during the late dry period and thus limit future production.

Genomic selection in dairy cattle has been successfully applied for milk production traits in many countries around the world. This has been enabled through the routine collection of phenotypes over several years and the large body of animals that have been genotyped. The application of genomics for non-routinely collected phenotypes has been less successful due to the cost of phenotyping and the smaller number of animals available for genotyping.

Richard J. Spelman of the Livestock Improvement Corporation of Hamilton, New Zealand, reported on genomic estimates for Johne's susceptibility and residual feed intake that have been recently been commercialized in the New Zealand dairy population. Johne's susceptibility has been estimated in a case control experimental setting. Over 1,500 animals that have been identified to be affected by Johne's have been genotyped and compared with a control derived from the general population of animals that have been genotyped in the LIC genomic selection data set. The accuracy of evaluation for Johne's susceptibility is approximately 30% with a heritability of 18%. Residual feed intake was measured over 2000 growing Holstein-Friesian heifers in New Zealand and Australia, which were phenotyped over 42 days for feed intake and live weight gain. Genomic estimates for residual feed intake have a reliability of 10%.