Evaluation of forage soybean yield and quality characteristics and potential as a feed resource for developing replacement beef heifers

Emily G Taylor, Purdue University

Abstract

Two agronomic studies were conducted to evaluate the yield and quality potentials of forage soybean (Glycine max ( L.)) grown with and without pearl millet (Pennisetum glaucum (L.)). Results indicate that there were no differences between row spacings of 18 cm or 36 cm and targeted populations of 469,500 seeds ha-1 or 234,750 seeds ha-1 on dry matter yield or overall quality of the forage soybean. While harvest date had significant effects on quality as the crop matured, forage soybean as a monoculture proved to be a very forgiving crop, and recovered in quality as maturity advanced into the later reproductive stages of plant development. When forage soybean was intercropped with pearl millet as a mixture or in alternating rows, there were no significant differences in DM yield. In general, neutral detergent fiber and acid detergent fiber increased across harvest dates, while crude protein and in-vitro digestibility decreased. Collectively these studies suggest that, depending on equipment availability, row spacings of either 18 cm or 36 cm, and lower seeding rates of 234,750 seeds ha-1 would be most cost effective. These results also indicate that one late season harvest of soybean monoculture should reduce harvest cost and maximize both forage yield and quality, while an early season harvest followed by a late season harvest is needed to maximize both forage yield and quality when soybean is intercropped with pearl millet. In the feeding trial, yearling beef heifers were fed one of three nutritionally balanced diets; 1) a control diet of alfalfa haylage , 2) soybean silage or 3) soybean and pearl millet silage to evaluate growth performance and reproductive efficiency. While there were differences in dry matter intake and average daily gain, these diets were fed without negatively impacting growth or reproduction of the heifers. All heifers performed adequately on the soybean diets, maturing to at least 63% of their mature equivalent prior to breeding. One of the more significant observations from this study was that heifers consumed a near constant 1% of body weight of neutral detergent fiber per day. This finding should allow more precise dietary formulations by more accurate estimations of dry matter intake. Collectively, these experiments illustrate that forage soybean is an alternative feed resource for developing replacement beef heifers. Soybean has the potential to have a positive impact on the cow-calf industry by allowing producers to utilize land in a singular and "double crop" manner to improve land use and profitability.

Degree

M.S.

Advisors

Lemenager, Purdue University.

Subject Area

Zoology|Animal sciences

COinS