Pearl Millet Silage for Growing Beef Heifers and Steers

Spring and late summer planted crops of ‘HGM-100 ’ pearl millet grain hybrid [Pennisetum glaucum (L.) R. Br.] were compared with corn (Zea mays L.) as potential silage for growing beef cattle (Bos taurus). In Experiment 1 separate plantings of pearl millet were harvested at the soft dough stage of grain maturity in either July or September 1993. Wilting the springplanted first crop millet (FCM) prior to harvest or direct cutting and adding a microbial preservative to the summer planted second crop millet (SCM), did not improve fermentation. The pH was higher, and lactic acid much lower for millet silages compared with corn silage (HCS; pH and lactic acid [% of dry matter (DM)], respectively, were: FCM, 5.74, 3.22; SCM, 4.12,3.34; HCS, 3.66, 8.69). Dry matter intake by growing heifers (average initial weight 600 lb) was 6.5 lb/d for both FCM and SCM silages, and higher (P < 0.01) at 13.4 lb/d for HCS. Average daily gains (ADG) were 0.34 and 0.45 lb/d, respectively, for FCM and SCM silages, and ADG was higher (P < 0.01) at 2.1 lb/d for HCS. In Experiment 2 (1996), silage treatments included corn silage (SCS), direct-cut HGM-100 millet treated with an inoculant (MS) or inoculant plus 0.5% ground corn (MSC) added to improve fermentation of silages. These millet silages had higher DM (31% and 36%), somewhat lower crude protein (11% to 11.5%), but they had improved fermentation compared with millet silages in Experiment 1. In Experiment 2, 75 beef steers (avg initial wt 600 lb) were assigned to the three silage treatments and fed in drylot for 56 d. Steers fed SCS had higher ADG (P < 0.05) and improved DM/gain (P < 0.05) than steers fed millet (MS) or corn (MSC). Respective 56-d ADG (pounds) and DM/gain for treatments were: MS, 1.71, 7.35; MSC, 1.70, 7.92; SCS, 2.69, 5.05. Steer performance indicated that millet silages might be efficiently used in growing cattle diets, but supplemental energy would be required for increased performance in comparable corn silage diets. Research QuestionTwo crops of millet for silage can be grown during the same time required to grow one crop of corn for silage. It is generally recommended that a readily available carbohydrate source be added to millet forage at ensiling time to aid fermentation. ‘HGM-100’ pearl millet (Tift 90 D₂A₁E₁ × Tift 8699) was released as a high grain-producing cultivar. The increased grain-to-plant ratio of this millet offered the potential to provide additional readily fermentable carbohydrates to adequately support ensiling without the addition of a supplemental carbohydrate source. Studies were conducted to address the question: What is the potential quality of millet silages with and without additional carbohydrate added at ensiling, and is the quality high enough to support acceptable performance in growing beef cattle? Literature SummaryThe development and release of improved varieties of pearl millet in the 1950s initiated research to evaluate millet as a silage crop. Results of feeding trials with millet silage were generally positive. However, to attain good fermentation, the chopped millet forage was mixed with 5% to 7.5% of a readily fermentable carbohydrate such as corn. Grain yield of 3000 lb/acre are typical for the HGM-100 pearl millet cultivar. Therefore, sufficient carbohydrates should be present in the HGM-100 forage for adequate fermentation of the millet silage. Study DescriptionIn one experiment, a spring crop and a late summer crop of HGM-100 pearl millet were compared with corn as potential silages for growing beef heifers. Forage yield and silage characterization were determined, and the silages were fed in a heifer growth trial. In a second experiment, millet silages with and without a carbohydrate source added at ensiling were compared for effects on silage quality and feeding value in a steer feeding trial. Applied QuestionsDid the grain content of the HGM-100 pearl millet provide sufficient carbohydrates for proper fermentation? The millet forage did not contain enough carbohydrate to support proper fermentation and silage preservation in the original study, and although fermentation was improved in the second study, lactic acid and dry matter (DM) were increased when a carbohydrate source was added to millet forage at ensiling. Since the millet forages were harvested in the soft dough stage of maturity, the potential for high grain production and increased carbohydrate content was over estimated. Did wilting of the millet forage prior to harvest or direct cutting and adding a microbial preservative result in proper fermentation? Wilting the spring crop millet prior to harvest or direct cutting and adding a microbial preservative to the second crop millet in the first study failed to provide forage material for proper fermentation and preservation. Addition of silage inoculant and a carbohydrate source improved millet silage fermentation and preservation in the second study, however, the millet forage had higher DM before ensiling in this study than in the first study. Is the quality of millet silage sufficient to support acceptable gains in growing beef cattle? In the first experiment, heifers were fed millet silages of relatively poor quality resulting in a daily DM intake of 6.5 lb/d, which was about half that for corn silage (13.4 lb/d). The low intake of millet silages reduced average daily gains, and heifers gained only 0.34 and 0.45 lb/d compared with 2.08 lb/d when fed corn silage. In the second experiment, beef steers had similar DM intake on millet silage, with added carbohydrate at ensiling, and corn silage, and both had higher DM intake than millet silage alone. These millet silages were of higher quality than in the first study, and supported average daily gains of 1.7 lb/d, which were acceptable, but significantly lower than gains on corn silage (2.69 lb/d). Growing beef cattle need more energy than that supplied by pearl millet silage to produce efficient gains, but it might be used in transition feeding with other supplemental energy sources, or for cattle in transit from one feeding/management system to another when properly suplemented with energy and protein sources.