No abstract

The objective of this study was to evaluate the feasibility of using the dry matter intake of first 2 h after feeding (DMI-2h), body weight (BW), and milk yield to estimate daily DMI in mid and late lactating dairy cows with fed ration three times per day. Our dataset included 2840 individual observations from 76 cows enrolled in two studies, of which 2259 observations served as development dataset (DDS) from 54 cows and 581 observations acted as the validation dataset (VDS) from 22 cows. The descriptive statistics of these variables were 26.0 ± 2.77 kg/day (mean ± standard deviation) of DMI, 14.9 ± 3.68 kg/day of DMI-2h, 35.0 ± 5.48 kg/day of milk yield, and 636 ± 82.6 kg/day of BW in DDS and 23.2 ± 4.72 kg/day of DMI, 12.6 ± 4.08 kg/day of DMI-2h, 30.4 ± 5.85 kg/day of milk yield, and 597 ± 63.7 kg/day of BW in VDS, respectively. A multiple regression analysis was conducted using the REG procedure of SAS to develop the forecasting models for DMI. The proposed prediction equation was: DMI (kg/day) = 8.499 + 0.2725 × DMI-2h (kg/day) + 0.2132 × Milk yield (kg/day) + 0.0095 × BW (kg/day) (R2 = 0.46, mean bias = 0 kg/day, RMSPE = 1.26 kg/day). Moreover, when compared with the prediction equation for DMI in Nutrient Requirements of Dairy Cattle (2001) using the independent dataset (VDS), our proposed model shows higher R2 (0.22 vs. 0.07) and smaller mean bias (−0.10 vs. 1.52 kg/day) and RMSPE (1.77 vs. 2.34 kg/day). Overall, we constructed a feasible forecasting model with better precision and accuracy in predicting daily DMI of dairy cows in mid and late lactation when fed ration three times per day.

Abstract Backgrounds: Chromium is an important trace element that may regulate dairy cow metabolism. The objective of this study was to investigate the effect of chromium methionine (Cr-Met) supplementation on lactation performance, hepatic respiratory rate and anti-oxidative capacity in early-lactating Holstein dairy cows. Results: Sixty-four multiparous cows were grouped into 16 blocks based on parity, days in milk and milk production, and four cows within a block then were assigned randomly to one of four dietary treatments with 0, 4, 8 or 16 g/d of Cr-Met per cow in addition to a basal diet. The experiment lasted for 14 weeks, with the first two weeks as adaptation period. Milk yield and composition were recorded weekly. Dry matter intake was measured every other week. The plasma variables were measured in weeks 4, 8 and 12 of the experiment. Supplementation of Cr-Met did not affect dry matter intake of early-lactating dairy cows. As the supplementation of Cr-Met increased, yields of milk, fat, lactose and energy corrected milk increased in a linear manner (P < 0.01). In terms of plasma variables, insulin concentration decreased in a linear manner with Cr-Met supplementation (P = 0.04). As for variables relative to hepatic respiration rate, concentrations of pyruvate and NADH in the plasma were increased in linear (P < 0.01) and quadratic manners (P < 0.01), and lactic dehydrogenase activity was linearly increased as the feeding levels of Cr-Met increased (P < 0.01). Moreover, plasma glutathione peroxidase and superoxide dismutase activity were increased in a linear manner (P < 0.01). Conclusion: The results suggest that Cr-Met supplementation improved lactation performance of early-lactating dairy cows through enhancing antioxidant capacity and hepatic cellular respiration.

The authors have withdrawn this preprint due to erroneous posting.