Secondary analysis of feed intake, calcemia, and assessment of immune function in the subsequent periparturient period of cows that responded to high- and low-energy diets during late lactation

The purpose of this study was to use a secondary analysis to investigate the use of feeding high and low-energy diets to alter BCS at dry-off, and to assess the subsequent changes in BCS on feed intake, calcemia, and assessment of immune function, including inflammation, during the periparturient period. Multiparous Holstein lactating dairy cows at 150 d of gestation were blocked by expected calving date and randomly assigned to receive one of 2 dietary treatments during late lactation until dry-off, aiming to maintain or decrease BCS. To this end, a low-energy diet (LE; 1.54 ± 0.01 Mcal/kg DM; n = 27) was formulated not to exceed energy requirements, and a high-energy diet (HE; 1.8 ± 0.01 Mcal/kg DM; n = 28) was formulated to exceed energy requirements based on the NEL of cows during late lactation. The HE cows that gained ≥0.5 BCS and LE cows that lost, maintained, or gained ≤0.25 BCS were included in this study for analysis. Cows that did not respond to dietary treatment were not included in the analysis, resulting in a cohort of 40 cows: 20 cows in the HE group that responded, and 20 cows in the LE group that responded to dietary treatments. After dry-off, all cows were fed the same diets for the duration of the study. In the last week of gestation, the BCS of the HE and LE cows averaged 3.85 and 3.26 ± 0.1, respectively. During the last 10 d prepartum, HE cows consumed, on average, 1.6 kg DM per day less than LE cows. Plasma concentrations of IL-6 and haptoglobin did not differ between groups 7 d before parturition (725 ± 147 pg/mL and 0.57 ± 0.04 ng/mL, respectively). Serum leptin concentrations also did not differ between groups 7 d before parturition. No differences were detected in ionized calcium, total magnesium (Mg), and total phosphorus (P) between groups from -1 to 3 DIM. Nonesterified fatty acid concentrations tended to be elevated in HE cows from -7 to 7 DIM. Neutrophil phagocytic capacity, oxidative burst, and the expression of the cellular adhesion selectin CD62L were also similar between groups. The expression of the cellular adhesion integrin CD18 on neutrophils was increased in the LE group at 2 DIM but was not different at 0 and 7 DIM. Overall, our findings from this secondary analysis of cows that altered BCS in response to dietary treatment indicate that feeding a HE diet during late lactation affected feed intake without significantly altering immune function or calcemia during the periparturient period.