Investigation of dry period length and transition period intervention strategies to increase ruminant productivity in the subsequent lactation

Doctor of PhilosophyDepartment of Animal Sciences and IndustryBarry J. BradfordSuccessful transition from gestation to lactation sets the stage for lifetime productivity in ruminants. Several factors affecting successful transition are due to characteristics of the dry period. Optimal dry period length for dairy cattle has long been debated, but no study has ever evaluated performance associations with dry period length while differentiating between reasons for the deviation from target. We used 32,182 lactations from 16 farms in a retrospective observational study to determine if biological versus management reasons for a short or long dry period have the same associations with subsequent lactation productivity. Dry period length (DPL) and gestation length (GL) were each categorized as short or long and combined to generate 7 study groups. Cows with both a short DPL and GL had the worst early and whole lactation milk and component yields. Although not as severe, similar decreases for cows with an average DPL but short GL indicated short GL is a greater contributor to poor performance than DPL itself. Long GL, independent of DPL, did not impact productivity. Cows subjected to a long DPL based on management decisions experienced issues related to excessive lipid mobilization that did not affect milk production but manifested in greater hazard of leaving the herd. Intervention strategies have targeted the depressed feed intake and postpartum inflammation that characterizes the transition period. Saccharomyces cerevisiae fermentation product was fed from -29 ± 5 to 42 d relative to calving to evaluate the effects on feed intake, milk production, and metabolism. Supplementation increased meals per d with less time between meals, increased milk fat concentration, altered cholesterol metabolism, and increased incidence of subclinical ketosis, but early lactation milk yield and metabolism (plasma free fatty acids, β-hydroxybutyrate, glucose, and insulin) were generally unaffected. Postpartum treatment with the non-steroidal anti-inflammatory drug, meloxicam, has previously been evaluated in dairy cattle, but this intervention strategy has not been applied to sheep. After lambing, 36 Hampshire and Hampshire × Suffolk ewes were sequentially assigned within type of birth to control or meloxicam treatment on d 1 and 4 of lactation. Postpartum meloxicam treatment of ewes decreased plasma concentrations of haptoglobin (marker of inflammation) and several oxylipids, with the greatest impact in ewes with biomarkers reflecting a greater inflammatory state before treatment. Overall, the transition from gestation to lactation can be impacted by differences in individual biology and management, with some aspects of the transition improved through use of feed additives and drug interventions