Oxeladin Citrate

Periparturient dairy cattle undergo physiological adaptations to support fetal growth and colostrum synthesis in late gestation and milk production in early lactation. To support energy and protein demands, dairy cattle mobilize body tissue reserves. The objective of this study was to determine the effects of prepartum skeletal muscle reserves and supplementation of branched-chain volatile fatty acids (BCVFA) on body composition measurements, metabolic markers related to health, protein, and energy status, and subsequent milk yield in multiparous dairy cows. Skeletal muscle reserves were assessed by 3 ultrasounds of the longissimus dorsi muscle depth (LDD) measured 42 d before expected calving, and cows (n = 48) were assigned to either high muscle (HM; >4.6 cm) or low muscle (LM; ≤4.6 cm) groups. Cows were then randomly assigned to either control (CON) of soyhull pellets (80 g/d) or BCVFA treatment, which contained isobutyrate (40 g/d), isovalerate (20 g/d), and 2-methylbutyrate (20 g/d) calcium salt products. Treatments were top dressed from 42 d before expected calving until parturition, resulting in 4 combinations of muscle groups and treatments: HM-CON (n = 13), HM-BCVFA (n = 13), LM-CON (n = 11), and LM-BCVFA (n = 11). Measurements of the LDD, BW, and BCS were taken on the following days relative to calving: -42, -35, -21, -7, 0, 7, 14, 21, 28. Weekly blood samples were taken to measure glucose, BHB, and insulin concentrations, and 5 of the blood sample time points were used to determine 3-methylhistidine and creatinine blood concentrations. Milk yield was recorded daily for the first 28 d of lactation, and samples were taken from both milkings once a week for the first 4 wk to determine components. The statistical model included the fixed effects of treatment, group, time, and their interactions, and the random effect of cow nested within group and treatment. Prepartum muscle mobilization varied between muscle groups, as LM cows accreted muscle prepartum, and HM cows mobilized muscle. The HM cows had higher milk fat, protein, lactose, and energy-corrected milk yields. The BCVFA supplementation tended to increase blood glucose concentrations both prepartum and postpartum and decreased milk urea nitrogen concentrations. Greater prepartum skeletal muscle reserves improve productivity of early-lactation cows, likely due to differences in muscle mobilization, and BCVFA supplementation improves glucose dynamics during the transition period, which may improve the metabolic health of the periparturient dairy cow.

Our objective was to determine the effects of isoacids (ISO) on the lactation performance, digestibility, and milk fatty acid (FA) profile of Holstein cows fed 2 forage NDF levels (FL). The study was 10-wk long (including 2-wk for covariate) utilizing a randomized complete block design. Sixty-four mid-lactating Holstein cows [662 ± 71 kg BW, 119 ± 51 DIM, 2 ± 0.9 parity] were blocked by parity, DIM, and prior milk yield (MY) for multiparous cows or genetic merit for primiparous cows, and randomly assigned to 1 of the 4 diets (n = 16). Diets were arranged as a 2 × 2 factorial, with 2 FL containing 21 (HF) and 17% forage NDF (LF) without (WIA) or with ISO supplementation (IA, 7.85 mmol/kg DM and 3.44 mmol/kg DM for isobutyrate and 2-methylbutyrate, respectively). Diets were balanced for similar NE_L (1.58 Mcal/kg DM), CP (16.0%) and total NDF (27.2%). Feed intake and MY were recorded daily. Nutrient digestibility for each cow was determined using indigestible NDF as a marker, and fecal samples were collected at 8-time points (4 h intervals between samples). Individual cow milk samples composited over a 10-wk period were analyzed using gas chromatography for FA profile. The statistical model included FL, ISO, and FL × ISO as fixed effects and block as a random effect (lme4 in R). The ISO did not affect DMI (P = 0.13), while LF had greater DMI than HF diets (27.8 vs. 26.0 kg/d; P < 0.01). However, ISO increased MY (34.7 vs. 37.2 kg/d; P < 0.01) and ECM (41.9 vs. 39.0 kg/d; P < 0.01) by 7% in HF but not in the LF diet, suggesting FL × ISO interaction (P = 0.04). Interestingly, ISO increased ADG (0.4 kg/d) but decreased MUN by 9% only in LF diet as indicated by FL × ISO interaction (P < 0.01). Additionally, ISO increased DM, OM, NDF, and CP digestibility by 10-24% in HF (P < 0.01), but not in LF (FL × ISO; P > 0.05). As expected, ISO increased milk odd chain FA profiles in the IA groups irrespective of FL, e.g., the IA had greater C15:0 (1.87 vs. 1.54 g/100g FA; P = 0.03) and a tendency to be greater C17:0 levels (0.86 vs. 0.76 g/100g FA; P = 0.05) compared with WIA groups. Overall, ISO improved MY and nutrient digestibility in the HF whereas it increased ADG and decreased MUN in LF diet. Additionally, ISO increased milk odd chain FA (C15:0 and C17:0) regardless of FL.