An Evaluation of Tissue Mobilization and Chronic Circadian Disruptions in Transition Dairy Cows
Cattle that were exposed to the PS light pattern in the late gestational period were determined to have a disrupted, weaker circadian rhythm than CON animals as a result of a decreased internal temperature circadian rhythm amplitude and delayed start of the daily circadian rhythm. These circadian disruptions resulted in PS cows developing greater insulin resistance than CON cows at 14 d BEC (4,303 vs. 2,386 mIU Insulin AUC/180 min) and at 7 DIM (1,053 vs. 697 mIU Insulin AUC/180 min) after the light timing treatment was removed. The PS timing of light was associated with reduced mammary development at 21 d BEC (5.22 vs. 12.44% epithelial proliferation) and those animals produced less milk compared to CON through 60 DIM (40.3 vs. 42.6 kg/d). Thereby demonstrating the importance of maintaining consistency in the timing of events during the dry period to maximize animal health and performance through early lactation.
HM cattle mobilized more muscle tissue than LM cows from 35 d BEC through 60 DIM (1.64 vs. 0.30 cm LDD mobilized) to have no difference in LDD at 60 DIM (3.41 vs. 3.09 cm). While there were no differences in milk production (40.6 vs. 42.0 kg/d), milk components, or intake between HM and LM cows, there was a tendency for HM cows to give birth to heavier calves (44.3 vs. 42.3 kg) and have greater 3-MH:CRE ratio (0.153 vs. 0.135) over the first three weeks of lactation. Overall, cattle mobilized muscle and adipose tissue reserves through 30 DIM relative to the amount of those reserves they had available at 21 d BEC (R2=0.47 and 0.82, respectively). Thereby suggesting that cattle tissue reserves in the last few weeks of gestation affect the nutrient source that cattle primarily use to meet nutrient requirements from late gestation into early lactation. Continued research will need to address how alterations in the timing of events and quantity of tissue reserves through the lactation period affect cattle performance and heath in the postpartum period.
Funding
AFRI competitive grant no. 2017-67015-26569
History
Degree Type
- Master of Science
Department
- Animal Sciences
Campus location
- West Lafayette