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Component vs. total mixed ration feeding improves peripheral energetics in high-producing lactating dairy cows
This objective of this study was to compare effects of total mixed ration (TMR) delivery vs. component feeding of forage and concentrate (CFC) on peripheral blood indicators of energy status in high-producing lactating cows in a noncompetitive housing environment. Four multiparous (665 ± 65 kg body weight; 67 ± 20 days in milk; mean ± SD) and four primiparous (583 ± 43 kg body weight; 85 ± 36 days in milk) lactating Holstein cows in free individual boxes (4 ×3 m) were monitored in a cross-over design experiment with two 25-d periods. Each period had 20-d of adaptation and 5-d of sampling and data collection. Cows were offered a single diet, based on barley grain and a mixture of corn silage and alfalfa hay, prepared and presented as either TMR or CFC. The forage to concentrate ratio was 50:50 (dry matter basis), permitting 5-10% daily orts. Cows were experimented under thermoneutral conditions and were milked twice daily at 0500 and 1700 h. Jugular vein blood samples were taken for two days in each period, twice daily just before milking. Data were analyzed using Mixed Models with fixed effects of treatment, parity and their interaction, and random effects of period and cow within parity. Least square means were estimated with Restricted Maximum Likelihood method, and degrees of freedom were calculated using Satterthwaite method. Feeding CFC instead of TMR increased (P<0.05) blood concentrations of glucose (65 vs. 60 mg/dl) and BHBA (0.35 vs. 0.25 mmol/L), while decreasing (P<0.05) those of NEFA (0.2 vs. 0.3 mmol/L). Blood urea nitrogen was not different between treatments (12.7 mg/dL). Neither parity nor its interaction with feeding system affected blood metabolites. The data do not support the conventional belief that feeding TMR is more energetically efficient than component forage and concentrate delivery. The results provide new insights into optimizing feeding systems in high-producing dairy cows for improved energy efficiency and animal health. Future studies are required before clear-cut guidelines can be formulated for on-farm practice.
Keywords:
Feeding system
Energetics
Lactating cow