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Andrews, D.J., W.W. Hanna, J.F. Rajewski, and V.P. Collins. 1996. Advances in grain pearl millet: Utilization and production research. p. 170-177. In: J. Janick (ed.), Progress in new crops. ASHS Press, Alexandria, VA.

Advances in Grain Pearl Millet: Utilization and Production Research*

David J. Andrews, Wayne W. Hanna, John F. Rajewski, and Victoria P. Collins


  1. UTILIZATION RESEARCH
  2. PRODUCTION RESEARCH
  3. BREEDING RESEARCH
  4. FUTURE NEEDS
  5. CONCLUSION
  6. REFERENCES
  7. Table 1
  8. Table 2
  9. Table 3
  10. Table 4
  11. Table 5
  12. Table 6

Pearl millet [Pennisetum glaucum (L) R. Br.] ranks as the world's fourth most important tropical food cereal with 26 million ha (64 million acres) being grown mostly in semi-arid west Africa and India (Andrews and Bramel-Cox 1994). While early maturing and well adapted to droughty, sandy acid soils of low fertility, pearl millet is highly responsive to fertilizer and moisture on well drained soils.

Until recently, pearl millet has only been grown in the United States as a hybrid forage crop, on about 0.6 million ha (1.5 million acres). Grain breeding programs have been established at Kansas State University (Hays), USDA/ARS (Tifton, Georgia) and the University of Nebraska-Lincoln as previously described by Andrews et al. (1993). Grain hybrid HGM 100™, an exclusive release from Tifton, Georgia, has been marketed in the Southeast by Agra Tech Ltd., of Atlanta since 1991. The grain has been purchased at the current maize price and is used in poultry and animal rations.

UTILIZATION RESEARCH

From a nutritional standpoint, pearl millet is an attractive feed grain. Several studies indicate that metabolizable energy of pearl millet for non-ruminant animals is approximately equal to that of maize (Abate and Gomez 1984; Fancher et al. 1987; Amato and Forrester 1995). When compared to maize on a weight basis, pearl millet is 8%-60% higher in crude protein, 40% richer in lysine and methionine, and 30% richer in threonine (Burton et al. 1972). Therefore, substitution of pearl millet for maize reduces the need for high protein feed ingredients and supplemental amino acids.

Pearl millet has fewer anti-nutritional factors than most grain crops. In contrast to rye and sorghum, pearl millet grain is low in tannins, which limit palatability and inhibit protein digestion. There appears to be no need for heat treatment of pearl millet to destroy protease inhibitors or other harmful factors. However, pearl millet can contain saponin anti-metabolites at levels up to 200 ppm (Sodipo and Arinze 1985). Saponins are known to damage membranes in the digestive tract, so Burtle and Newton (1995) have suggested caution when feeding high levels of pearl millet to fish species, which may be especially sensitive to saponin toxicity.

In the United States, mycotoxins are not likely to cause major problems in pearl millet. Wilson and co-workers (1993) found that this crop appears to be resistant to Aspergillus flavus infestation. Pearl millet is susceptible to infection by Fusarium fungi. When harvest was delayed 50 days post anthesis, Wilson et al. (1995) isolated Fusarium species in 71.5% of the grain samples. However, levels of Fusarium toxins remained very low.

Poultry are likely to be the major consumers of pearl millet in the United States and a Georgia poultry cooperative has already provided a market for this grain. In 1993, 6300 ha (15,500 acres) of the first commercially available strain of pearl millet bred for grain, HGM 100™, were grown in Georgia and Florida for broiler feed. In 1994, 4000 ha (9,900 acres) were planted (Grabow and Wilson 1995). Several studies have compared isocaloric, isonitrogeneous broiler diets based on maize and pearl millet (Fancher et al. 1987; Smith et al. 1989; Amato and Forrester 1995). All have shown that when pearl millet diets are formulated with correct estimates of protein and energy, broiler performance is equivalent to that obtained with maize (Table 1).

Supplementation of pearl millet-soy diets with lysine or sulfur amino acids appears to be unnecessary (Amato and Forrester 1995). Because the need for protein supplementation is reduced, the feed cost of per unit gain is about 3% lower for millet than maize (Bramel-Cox et al. 1995).

Pearl millet is also a satisfactory feed for laying hens. Kumar et al. (1991) found increased egg size and better feed conversion when pearl millet was substituted for maize at 60% by weight. The higher methionine and energy content of pearl millet might explain these results. Using more recent estimates of nutrient content, Collins et al. (1995) found millet and maize gave equivalent egg production and feed efficiency. However, the fatty acid profile of the eggs produced by millet-fed hens differed significantly from those from maize-fed hens. Feeding millet produced eggs which were higher in mono-unsaturated and omega-3 polyunsaturated fatty acids (PUFA), and lower in omega-6 fatty acids than when feeding any other common cereal (Table 2). Since mono-unsaturated and especially omega-3 PUFA may offer health benefits to consumers, pearl millet may offer one route to a more healthy "designer" egg.

Swine may represent a second major market for pearl millet, although few studies have been reported. Calder (1955) found pigs fed 50% or 75% pearl millet reached slaughter weight 10 days earlier than maize-fed pigs. Murray and Lewis (1995) found "optimal growth performance" in pearl millet-fed pigs. Lawrence and co-workers (1995) and Adeola and Orbain (1995) found that replacement of maize with pearl millet on a weight basis gave equivalent gain and feed efficiency, but the pearl millet diets used in these studies were higher in protein than the maize diets. In contrast, Dove and Myer (1995) found that replacement of more than 67% of maize with pearl millet resulted in an increased feed/gain ratio. They suggested that methionine may be less available in pearl millet than in other grains, but this is not supported by the above studies with laying hens, which are very responsive to methionine levels. Undigested whole millet seeds may have been responsible for the poorer performance in this trial.

Ducks have even faster growth rates and higher protein requirements than broiler chickens, so this species is very sensitive to nutrition. Adeola et al. (1994) estimated conservatively that pearl millet is equivalent to maize in feeding value for ducks. They calculated that pearl millet is 6% higher than maize in metabolizable energy.

Wild birds can cause significant crop losses in pearl millet, and this suggests its use in wildlife plantings for game birds. In these situations, a tendency to lodge might even be useful because it gives the birds easy access to feed. Iler and Hanna (1995) found pearl millet gave good cover to birds in the summer and easy access to hunters in the fall. Savage (1995) fed pearl millet to newly hatched bobwhite quail, and found pearl millet fed chicks consumed more and wasted far less feed than chicks fed maize. Fourteen-day weight gains were improved 8%-22% and mortality was halved when chicks were fed a pearl millet based diet instead of maize (Table 3). Pearl millet may thus be ideal for the specialty game bird market.

At University of Georgia, channel catfish showed equivalent weight gain and feed efficiency when either maize or pearl millet was fed at 30% of total diet. However, diets containing pearl millet: maize ratios of 1:2 or 2:3 gave significantly better gain and efficiency than either grain alone (Table 4), (Burtle and Newton 1995).

For beef cattle, pearl millet grain appears to be superior to sorghum but inferior to maize in feeding value. Christiansen and co-workers (1984) found pearl millet was 4% higher in net energy than sorghum and pearl millet gave better calf performance. Hill et al. (1990) evaluated pearl millet grain for finishing beef cattle in both metabolism and feedlot trials. Both experiments showed that the usable energy value of pearl millet is 85%-90% of that of maize, when equivalent protein/energy ratios are fed. These authors also reported that careful grinding of pearl millet seems to improve nutrient utilization.

Processing and handling pearl millet feeds requires some practice, but no special equipment. Harvesting equipment should be carefully adjusted to thresh the small seeds completely, because poorly threshed millet has lower feeding value (Collins et al. 1995). Grinding or rolling is probably necessary, because experiments with cattle (Hill and Hanna 1990) and swine (Dove and Myer 1995) indicate that small unground seeds may not be fully digested. Amato and Forrester (1995) found that pearl millet shows satisfactory behavior in pelleting processes. However, ground feeds made with pearl millet tend to flow much more easily than traditional maize-based feeds. This trait may be an advantage with some feeder designs, but it could cause wastage with other feeding systems.

In summary, pearl millet appears to have significant potential as a feed grain, especially for non-ruminant species. Best results will be obtained with careful attention to harvesting and processing the grain and to correct formulation of feeds.

PRODUCTION RESEARCH

Research has been conducted on planting date, row spacing, weed control and fertilizer response. Experiments in Florida (Woodruff 1995) with HGM 100™ showed the highest yields, 5430 kg/ha (6080 lb/acre), were obtained with the closest row spacing, 13 cm (5 inch) compared to 4380 kg/ha (4900 lb/acre) at 38 cm (15 inch) and 3730 kg/ha (4180 lb/acre) from 76 cm (30 inch) rows. Wiatrak et al. (1995) also obtained the highest yields at close row spacings, recording grain yields of 2840, 1760, and 1870 kg/ha (3180, 1970 and 2090 lb/acre) from 13, 38, and 76 cm rows, respectively. A contributory factor may be better weed competition from the narrow rows. Experiments in Nebraska (Boggs et al. 1992) on planting date x row spacing x Atrazine applications indicated that early planting (before June 7), 61 cm (24 inch) rather than 91 cm (36 inch) rows, and Atrazine 1.12 kg/ha (1.0 lb/acre) gave the highest yields with early hybrid 79-2068A x 57028R (Table 5). Yields from Atrazine treated plots were as good as those from hand cultivated, and both were significantly better than no weed control. There was no advantage of 30 cm over 61 cm rows.

The lack of herbicide registrations** and the physiological similarities between pearl millet and annual grass weeds need to be considered for chemical weed control in pearl millet production. Although Banvel and 2,4-D are the only herbicides registered for use on millet, there is no federally approved registration of these two herbicides or any other herbicide on pearl millet as a grain crop. Most grass herbicides damage pearl millet but some cause less injury at reduced application rates from which pearl millet recovers depending on the soil and field conditions. Tests conducted by Dowler and Wright (1995) in Georgia and Florida on sandy loam soils using hybrid HGM 100™ gave variable results but some general trends appeared (Table 6). Atrazine and Prowl caused less damage than Dual. Ramrod caused moderate damage. Postemergence Atrazine at 2.24 kg/ha (2 lb/acre) gave moderate grass control and good broadleaf control with light damage to pearl millet and no significant yield reduction. Preemergence 0.56 or 0.84 kg/ha Prowl (0.5 or 0.75 lb/acre) + 0.56 kg/ha 2,4-D (0.5 lb/acre) gave good grass and broadleaf control with little crop damage and no yield reduction. Herbicide rates used would depend on soil type. Herbicide studies on silt clay loam at Nebraska (Rajewski et al. 1987; Rajewski et al. 1995) indicate that surface and incorporated preemergence applications of Ramrod, Lasso, Lorox, Mowdown, Eradicane-X, Prowl, Treflan, or Sonalan can reduce pearl millet plant populations by 40% or more. Incorporated applications of Evik, Alanap, Atrazine, and Propazine did not reduce pearl millet emergence. Postemergence applications of Ramrod, Propazine, Atrazine, Basagran, Buctril, or Banvel at the 4-leaf stage of pearl millet development did not reduce plant numbers or cause significant leaf injury.

Research programs at Kansas and Nebraska have routinely used 1.12 kg/ha Atrazine (1.0 lb/acre) or 2.8 kg/ha Propazine (2.5 lb/acre) as preemergence grass and broadleaf weed control in breeding nurseries and hybrid yield tests on silt clay loam soils. After pearl millet emerges and reaches 2-3 leaf stage, the Nebraska program surface applies 3.36 kg/ha (3 lb/acre) Ramrod to prevent further emergence of grassy weeds. Basagran or Buctril, at normal recommended rates, is used as needed to provide postemergence control of broadleaf weeds.

Early planting (May, June in the Southeast; early June in the Midwest) are advantageous for growing pearl millet. Until new rust resistant cultivars are available in the Southeast, early planting is necessary to avoid losses to rust. However, warm soil (18° to 24°C, 65° to 75°F) is needed for good emergence which determines the earliest planting date in the Midwest. The need for warmer temperatures also allows the early germinated annual grass weeds to be removed prior to planting. Lower temperatures in conjunction with heavy rains risk soil crusting and fungal damping off which severely affects emergence. Experimental plantings made in early July in Indiana have shown that pearl millet has potential as an early maturing double crop after wheat harvest (J.D. Axtell 1994, pers. commun.). Optimum plant populations are about 150,000 plants/ha (60,000 plants/acre) but pearl millet can compensate well for much lower or irregular populations because of high tillering capacity. Among insects, chinch bug and European corn borer can cause damage, and varietal differences in susceptibility have been noted. In some locations, birds can be a severe problem on small isolated fields requiring timely harvest at grain maturity.

Pearl millet's feed advantages partly depend on consistently high grain protein levels. On soils of low inherent fertility, as in the Southeast, depending on soil tests, 90-134 kg/ha (80-120 lb N/acre) are needed (Woodruff 1995). In the Midwest, a side dressing of 45-90 kg/ha (40-80 lb N/acre) is worthwhile on the heavier fertile soils, depending on rotation with soybean and soil moisture availability. Production of grain with consistent protein levels is needed by the feed industry (especially for poultry).

BREEDING RESEARCH

Inbred parents for producing new hybrids are being developed by all three programs. Releases from the Kansas and Nebraska programs due this year are likely to be unrestricted public releases. The next releases from Tifton will carry rust and blight resistance. A grain pearl millet regional test with about 20 entries including sorghum checks has been conducted at 5 to 9 locations each year since 1988, (Rajewski and Andrews 1995a). This has allowed breeders to determine regional adaptabilities and cooperators to assess hybrids from different breeding programs. Pearl millet yields have exceeded sorghum in some locations, principally where the season is short, rainfall low, or soils sandy. The location average of all millet entries in 1994 trials ranged from 620 to 4370 kg/ha (550 to 3900 lb/acre). The best individual pearl millet entry yields were 5340, 5590, and 5430 kg/ha (4770, 4990, and 4850 lb/acre) at Tifton, Georgia; Lafayette, Indiana; and Mead, Nebraska, respectively (Rajewski and Andrews 1995b).

Population improvement has continued at Nebraska for herbicide tolerance to a higher preemergence application rate of Ramrod (5.6 kg/ha; 5 lb/acre) with Atrazine (1.12 kg/ha; 1 lb/acre). Population releases NPM-1, NPM-2, and NPM-3 all show potential for tolerance selection to the herbicides at rates recommended for grain sorghum. Four additional populations of different genetic backgrounds are being developed for future release with Ramrod tolerance.

Until the recent discovery of useful male fertility restorers for the A4 system of cytoplasmic male sterility (CMS) found by Hanna (1989), most hybrid grain breeding research had been based on developing maintainers (for seed parents) and restorers (pollen parents) for the A1 CMS system. Although the A1 system has been widely used in India, and is currently used in the U.S. to produce forage millet hybrids and HGM 100™, it does produce some pollen shedding revertants and causes problems in breeding because of the occurrence of high levels of partial sterility (Andrews and Rajewski 1994). The expression of male sterility and fertility in the A4 system is complete and no instances have yet been noted where minor genes or environment have modified this expression. Because almost all existing germplasm lines can, with a high probability of success, be converted to A4 seed parents, the A4 CMS system greatly increases the opportunities for breeding superior hybrids. Restorer (R4) genes, though generally infrequent, are readily identified and much more widely distributed than initially thought. The first grain type source population for A4 cytoplasm restorers, NPM-3, was released in 1994, (Andrews and Rajewski 1995). Rapid progress has been made in the University of Nebraska program, both in converting good A1 seed parents to A4 seed parents and in developing completely new A4 hybrid parents.

FUTURE NEEDS

Apart from higher yield potential, which is always needed, several obvious research and development needs still exist. These include: (1) better resistance to rust and blight for the South; (2) better germination, cool tolerance and seedling vigor for the Midwest/High Plains to permit earlier planting; (3) better herbicide tolerance, new herbicide evaluation, registration and label approval of available herbicides for grain production; (4) better resistance to lodging due to shallow rooting, weak stalk, or corn borer susceptibility; (5) good threshability; (6) release of new hybrid parents; and (7) continued end-use research and market development.

CONCLUSION

In the last four years interest in pearl millet has grown and substantially more is now known about how to produce pearl millet and its comparative feed values for a number of end-uses. In 1993, following commercial tests that showed pearl millet was equivalent to maize in feed value for broilers, pearl millet grain production commenced in Georgia and Florida. Utilization research has shown that pearl millet is better than maize in broiler and pig rations and equivalent to maize for ducks. While pearl millet is at least as good as maize for egg production, it produces a decrease in the egg n6:n3 fatty acid ratio. In human diets, lower n6:n3 ratios are associated with reduced incidence of cardiovascular disease. Pearl millet was found to be superior to maize in bob white chick and channel catfish diets.

Production research has determined that higher grain yields can be obtained from 61 cm (24 inch) or closer rows. Pearl millet is generally more sensitive to grass herbicides than soybeans, but adequate weed control has been obtained with some herbicides including Atrazine, Propazine, and Prowl. Except for double cropping situations, planting should be as early as consistent with soil temperature reaching 18° to 24°C (65° to 75°F).

Parental lines for early maturing hybrids for the midwest are due for release from the Kansas and Nebraska breeding programs early in 1996. Breeding research is well advanced to producing hybrids in the A4 cytoplasmic male sterile system, which offers advantages in both breeding efficiency and in the commercial production of hybrid seed.

In summary, recent research work has shown that pearl millet is a high quality feed grain, especially for poultry, and is well adapted to situations that may involve sandy soil, short season, heat, and low moisture. Markets need to be developed and more hybrid options made available.

REFERENCES


*Pearl millet research at the University of Nebraska is funded in part by USAID Grant No. DAN1254-G-00-0021-00 through INTSORMIL, the International Sorghum and Pearl Millet Collaborative Research Support Project.
**Mention of herbicides and other products is for identification only and does not imply endorsement by USDA or Universities.
Table 1. Final body weights at 41 days and feed conversion data for broilers where pearl millet was substituted for maize and soybean in isonitrogenous diets (Amato and Forrester 1995).

Treatment
(% millet)
Final body wt. (kg) Feed conversion
0 1.91 1.68
15 1.92 1.66
30 1.96 1.65
45 1.98 1.66


Table 2. Effect of substituting pearl millet for maize on egg fatty acids (Collins et al. 1995).

Content (% of total fatty acids)
Substitution of maize with pearl millet (%) Mono-unsaturated Poly-unsaturated DHA (C22:6n3) n-6/n-3 ratio
0 44.9az 20.3a 0.52a 13.1a
50 47.6b 17.9b 0.64b 10.1b
100 48.7c 15.7c 0.78c 8.6c
zMean separation in columns by Duncans multiple range test, 1% level.


Table 3. Body weight and mortality of bob-white Quail chicks fed pearl millet and maize-based diets (Savage 1995).

Weight (g) Mortality (%)
Crop 16 days 34 days 48 days 16 days 34 days 48 days
Pearl millet 28.7 88.7 117.5 4.6 5.7 14.3
Maize 23.2 80.1 110.6 22.3 27.7 31.1


Table 4. Performance and survival of channel catfish fed diets where pearl millet was substituted for maize (Burtle and Newton 1995).

Diet
Millet (%) Maize (%) Gain/fish (g/day) Feed/gain Survival (%)
0 30 2.27az 1.28a 91.5
10 20 2.44b 1.21b 91.0
20 10 2.47b 1.18b 93.4
30 0 2.15a 1.32a 89.2
zMean separation in columns by Duncan's multiple range test, 5% level.


Table 5. Row spacing and planting date effects on grain pearl millet yields (kg/ha) in Nebraska, 1991 (with Atrazine 1.12 kg/ha) (Boggs et al. 1992).

Row spacing
Planting time 30 cm 61 cm 91 cm
Early (May 20) 4310 4380 3880
Mid (June 7) 3530 3430 3040
Late (June 24) 2140 2510 2480
Planting date LSD, (5%) = 890
Row spacing LSD, (5%) = 220


Table 6. Herbicide test in Quincy, Florida, 1993, on grain pearl millet (Dowler and Wright 1995).

Control
Treatment Rate (kg/ha) Grass Broadleaf Injury (%) Grain yield (kg/ha)
Atrazinez 2.2 90 100 11 3160
Dual + 2, 4-D 1.7 + 0.6 90 96 96 1340
Ramrod + 2, 4-D 3.4 + 0.6 98 85 45 2430
Ramrod + Atrazine 3.4 + 1.1 98 97 31 2360
Prowl + 2, 4-D 0.6 + 0.6 95 97 16 3430
Prowl + Atrazine 0.6 + 1.1 99 97 10 2630
Hand weeded -- 100 100 0 3140
Non-treated -- 0 0 0 3120
LSD 5% 7 5 7
zPostemergence


Last update June 4, 1997 aw