Dairy operations must replace 25-33% of the milking herd each year, making heifer development a major production cost, second only to feed. Because of National Organic Program (NOP) pasture requirements, organic farmers face unique challenges in raising heifers to desired body weight (60% of mature weight) for first breeding at 15 months age. This project sought to establish an organic heifer development strategy based on high energy grasses and birdsfoot trefoil (BFT), a high protein legume containing condensed tannins.

Heifers were rotationally grazed on eight different pasture treatments: tall fescue, meadow bromegrass, orchardgrass, and perennial ryegrass in monocultures and binary mixtures with BFT. Trials were conducted over three successive seasons, and the performance of pastured heifers was compared with heifers raised in a dry lot with non-organic total mixed ration (TMR). Daily dry matter intake (DMI), weight gain over a 105-day period, parasite load (fecal egg count), blood urea nitrogen (BUN) and other health indicators, and reproductive success were recorded, and a partial budget analysis was conducted.

Heifers on grass-BFT showed higher DMI and weight gain (1.32 lb/day) than heifers on the corresponding grass monocultures (1.08 lb/day). Weight gain on ryegrass + BFT equaled that for the TMR control at 1.48 lb/day, while heifers grew more slowly on fescue pasture (0.86 and 1.19 lb/day for monoculture and ryegrass-BFT, respectively). Treatments did not significantly affect growth in hip height or fecal egg count. Heifers on grass-BFT pastures or TMR had higher BUN levels (13-16 mg/dL) than on grass monocultures (10-13 mg/dL), but no treatment resulted in BUN levels that could hurt reproductive performance (>20 mg/dL).

Although biculture pasture planting entailed added costs, enhanced heifer growth resulted in a significant improvement in net economic returns.