Effects of lasalocid on performance of lactating dairy cows

Sixty lactating dairy cows (30 multiparous and 30 primiparous) were used in a completely randomized block design to determine the effect of lasalocid supplementation on dairy cow performance. Starting wk 2 prepartum and lasting through wk 17 of lactation, cows received one of three experimental diets. The experimental total mixed rations were control (CD), control + 10 mg/kg of lasalocid (CD + 10) and control + 20 mg/kg of lasalocid (CD + 20). The alfalfa-based control diet (40:60; forage:concentrate) was formulated to contain 18% crude protein, 35% nonstructural carbohydrates, 31% neutral detergent fiber, and 6.6% ether extract. Lasalocid supplementation linearly decreased dry matter intake (DMI) without affecting milk production or milk composition. Mean milk production and percentages of fat and protein were 30.0, 30.8, and 28.6; 3.56, 3.51, and 3.63; 3.06, 3.05, and 3.09; respectively for treatments CD, CD + 10, and CD + 20. Lasalocid supplementation decreased milk urea N (MUN) when compared to control cows, and increasing supplementation caused a significant linear decrease in MUN. For the primiparous cows, lasalocid supplementation decreased DMI and MUN while increasing body condition score and feed efficiency. Results from this study indicate that lactating dairy cows and, in particular, primiparous cows may benefit from lasalocid supplementation in terms of more efficient utilization of nutrients for milk production, reduced MUN levels, reduced body condition loss, and higher margin over feed cost.