This study was designed to determine the effect of adding a molasses-based liquid feed (LF) supplement to a total mixed ration (TMR) on the feed sorting behavior and production of dairy cows.

Twelve lactating Holstein cows (88.2±19.5 DIM) were exposed, in a crossover design with 21-day periods, to each of two treatment diets: 1) control TMR and 2) control TMR with 4.1 percent dietary dry matter LF added.

Dry matter intake (DMI), sorting and milk yield were recorded for the last 7 days of each treatment period. Milk samples were collected for composition analysis for the last 3 days of each treatment period; these data were used to calculate 4 percent fat-corrected milk and energy-corrected milk yield. Sorting was determined by subjecting fresh feed and orts samples to particle separation and expressing the actual intake of each particle fraction as a percentage of the predicted intake of that fraction.

Addition of LF did not noticeably change the nutrient composition of the ration, with the exception of an expected increase in dietary sugar concentration (from 4.0 to 5.4 percent). Liquid feed supplementation affected the particle size distribution of the ration, resulting in a lesser amount of short and a greater amount of fine particles. Cows sorted against the longest ration particles on both treatment diets; the extent of this sorting was greater on the control diet (55.0 vs. 68.8 percent). Dry matter intake was 1.4kg/day higher when cows were fed the LF diet as compared with the control diet, resulting in higher acid-detergent fiber, neutral-detergent fiber and sugar intakes. As a result of the increased DMI, cows tended to produce 1.9kg/d more milk and produced 3.1 and 3.2kg/d more 4 percent fat-corrected milk and energy-corrected milk, respectively, on the LF diet. As a result, cows tended to produce more milk fat (0.13kg/d) and produced more milk protein (0.09kg/d) on the LF diet. No difference between treatments was observed in the efficiency of milk production.

Overall, adding a molasses-based LF to TMR can be used to decrease feed sorting, enhance DMI and improve milk yield.

Source: T.J. DeVries, R.M. Gill/Journal of Dairy Science