Two years ago, the UN General Assembly adopted India’s resolution to declare 2023 as the International Year of Millets. It offers numerous benefits to farmers, consumer health, foreign trade, the environment, and the country’s overall economy.
Millets are small seed grasses and cereal crops native to India, Africa, and other Asian countries where India is the largest producer in the world. Multiple varieties of millets are produced in the country such as Pearl Millets (Bajra), Sorghum (Jowar), Finger Millet (Ragi), Foxtail, Kodo, Barnyard, Proso, Little Millet, and Pseudo Millets like Buckwheat and Amaranths.
With better awareness, there is a rise in millet cultivation and consumption, particularly in India. It is a tough crop that can be cultivated in hot, drought-prone, or semi-arid regions, unpredictable climates, and nutrient-depleted soils.
Animal nutrition in India primarily comprises agricultural wastes like rice/wheat hay, oil cakes, corn silages, brans and/or pellet feeds, premixes, and supplements. Millets can be promoted in animal husbandry especially at last-mile rural areas and make the farmer self-sufficient by ensuring a sustainable income source despite the uncertainties in agriculture. The states like Uttar Pradesh, Maharashtra, Karnataka, Rajasthan, Andhra Pradesh, etc. actively involved in animal husbandry and dairy, and contribute to millet production with higher cultivation rates. Therefore, it is an apt time to understand the benefits of millet for animals and their nutrition costs or nutritional values. This can create a sustainable value chain and an economic & environment-friendly approach to animal husbandry.
This article sums up the scope of millets as animal nutrition: for dairy cattle, buffaloes, goats, poultry, and aquaculture on a brief note.
In animal nutrition, sorghum grain is mostly used as an energy source and is a good feedstuff for poultry, pigs, and ruminants. As compared to a maize plant, sorghum is approximately 30 to 40 percent more water-use efficient.
Pre-requirement for feeding: It must be processed before being fed else a large proportion of it will be swallowed whole and the waxy bran covering the grain will make digestion difficult.
Sorghum is the grass that is grown for fodder for grazing purposes or cut green to make silage and hay. Modern dairy promotes sorghum silage as feed. The stalk remaining after harvest is often grazed as it stays greener for a longer time. Grinding is a simple and least expensive method of preparing sorghum grain for cattle.
As a drought-tolerant species, sorghum improves water use efficiency while supporting relatively high levels of production in dairy cattle. Nutritionally, the protein content and neutral detergent fiber (NDF) digestibility of the sorghum and corn silage are similar.
However, sorghum silage is about 15% units higher in NDF content, causing it to be more “rumen filling” than corn silage, which could reduce total diet intake if sorghum silage is fed at the same amount as corn silage.
A total replacement of corn: If competitively priced, grain sorghum can be used at up to 70% in a broiler and layer rations and 55% in turkey rations replacing all corn. The nutrient profile of sorghum is complementary to protein sources typically formulated in poultry rations anywhere in the world and is very similar to corn (maize).
New varieties of grain sorghum are an excellent source of protein and energy for broilers and egg layers. Particle size is more important for feed manufacturing than nutrient uptake by poultry. Over-processing of the grain may cause chemical cross-linking and reduce nutrient availability.
Compared to corn, grain sorghum contains reduced quantities of yellow xanthophylls required for egg yolk pigmentation and skin coloration for broilers.
Goats and Aquaculture
Sorghum straw can be successfully incorporated into the complete diet of goats with an average weight gain of 66 g daily.
Omnivorous fish such as carp and tilapia can digest and metabolize sorghum-based diets. In common carp, the nutrient digestibility of sorghum compared with that of wheat bran and rye is shown in the below table.
In another study, sorghum or pellets containing 25% protein are used to feed common carp in ponds. The results showed that feeding on sorghum led to lower growth and higher body fat as compared with feeding on the pellet diet.
It may have light levels of allergens or tannins and checking the nutritive quality before feeding is advised.
Benefits of sorghum over corn
- Significantly lesser cost of seeds
- Inexpensive basic weed control
- Lesser requirement of fertilization
- Environment and cost of production are deciding factors to opt for sorghum over corn.
Pearl Millet (Bajra)
Pearl millet is palatable to livestock but its nutritive value depends on factors like variety, growing conditions, and preservation methods. The crude protein content of green bajra ranges from 6-20%. The fresh forage is well digested by ruminants, with DMD being 66-69%. A lot of research is going on to enhance forage yield, palatability, and digestibility.
Pearl millet grain is hard-hulled and should be finely grounded before being fed to livestock. As coarse grinding leads to the hard hull splintering into sharp fibres which can result in internal irritation to animals.
Impact of Pearl millet silage as an Alternative to Corn silage in Cattle
Studies with Pearl millet silage showed 4-10% lower crude protein content due to protein losses, and low rumen degradable fibre fraction (Guimaraes et al., 2010). Grazing pearl millet can potentially cause nitrate poisoning, and above 0.6% nitrate can reduce milk yield in dairy cattle (Newman et al., 2006). High nitrate levels can occur during drought (Sedivec et al., 1991) or due to heavy applications of nitrogen fertilizer.
Pearl millet silage can be included at 50% (DM basis) in a lucerne silage/concentrate-based diet or 36% (DM basis) of a concentrate-based diet which can sustain 24-26.3 kg/d milk yield in lactating dairy cows (Kochakpadee et al., 2002; Messman et al., 1991).
Pearl millet grain can be replaced up to 10-30% of corn silage or maize grain in dairy cows with no deleterious effect on DM intake, milk yield, or milk composition (Ribeiro et al., 2004; Terrill et al., 1998). In Brazil, pearl millet grain replacement of up to 67% of the whole maize plant showed no effect on milk production (França et al., 2004).
Feeding pearl millet to lactating dairy cows may reduce the supplemental protein requirement traditionally added to corn-based diets.
When compared to maize or sorghum, pearl millet is found to have equal or higher nutritive value (Vasan et al., 2008; Evans et al., 2005; Healy et al., 1991), which is confirmed by a meta-analysis of literature data (Batonon et al., 2015). Reconstitution with or without enzymes is interesting as it enhances metabolizable energy and N retention (Manwar et al., 2009; Manwar et al., 2008). Grinding pearl millet resulted in inconclusive and contradictory results (Vasan et al., 2008; Vasan et al., 2009).
Laying hens can be fed on pearl millet as a maize replacement in soybean/maize-based diets up to 15% of the diet for ungrounded pearl millet (Garcia et al., 2006). In order to guarantee egg production, yolk color, and poly-unsaturated fatty acids, pearl millet-based rations can be fed to laying hens with flaxseed (6% of the diet) (Amini et al., 2008) or soybean oil supplementation (Muramatsu et al., 2005).
For goats and aquaculture
As per studies, pearl millet forage can be fed to goats which resulted in similar DM, OM, and NDF intakes as Sudan grass, elephant grass, or forage sorghum. The crude protein intake and digestibility of pearl millet forage are higher than for other forages in goats (Aguiar et al., 2006).
Replacement of pearl millet hay with clover hay showed no effect on reproduction of female goats and the performance of the kids (Hanafy et al., 2007).
Pearl millet is efficiently used by tilapia (Oreochromis niloticus) and can be included as 10% of the diet during sex reversal.
Some pearl millet varieties contain alkaloids at levels ranging from 17-101 mg kg-1 (Krejsa et al., 1984). Water stress as well as added N fertilizer appears to increase nitrate and alkaloid content.
Overall, pearl millet can replace corn to an extent proving economic benefits but further research is required about the maximum quantities that can be fed to different species.
Finger Millet (Ragi)
Finger millet is cultivated as fodder grass in many places including India, the USA, and Ireland. It provides excellent hay and is used as green forage for cattle, sheep, and goats (de Wet, 2006; Mgonja et al., 2007; Baker, 2003). The straw resulting from grain harvest can be grazed directly by the animals.
While finger millet is grown for fodder, most of the information available is about the straw, which is an important by-product of the grain crop. Since finger millet straw is of poor nutritive value, it must be supplemented with nitrogen and energy sources in order to meet maintenance or production requirements. As with other cereal straws, its nutritive value can be improved by urea and ammonia treatment, but supplementation must be adapted accordingly.
Like other cereal grains, finger millet is an energy feed valuable for its high carbohydrate content. However, its protein content (7-10%) is often slightly lower than that of maize grain and its fibre content is higher (crude fibre 4-9% DM). It is also much less rich in protein than pearl millet (Pennisetum glaucum), which is a common potential replacement for maize in areas where the three crops are available.
Because of its lower nutritive value, finger millet is used when the prices of other cereals are high.
Ragi straw can be used as forage in diets for crossbred dairy cows supplemented with a balanced concentrate mixture (energy and protein), which give 8-9 kg milk yield (Chandrasekharaiah et al., 2004; Bhatta et al., 2000).
Finger millet straw is a valuable forage for growing heifers when supplemented with wheat bran (25%) and groundnut cake (Prasad et al., 1997). The straw can be used as forage for growing heifers (155 kg) supplemented with a small amount of concentrate (0.89 kg DM).
Finger millet grains contain tannins in variable amounts, depending on the variety. These tannins affect in vitro protein digestibility but it is unclear if it is detrimental to animal nutrition (Ramachandra et al., 1977).
In India, finger millet grain is used as a source of energy to supplement dairy cows during early to mid-lactation, resulting in an increase in milk yield (average increase of 1.9 liter/cow/day), fat and solids-not-fat content of milk (average increase of 0.2-0.3%), but reduced milk urea content. It is economically profitable (Gowda et al., 2009). Cows with high blood urea nitrogen (more than 19 mg%) and infertility showed improvement in their health and reproductive status after supplementation with 1-2 kg/d of finger millet grain for 2 to 3 months (Gupta et al., 2008).
It also contains methionine, an essential nutrient that helps dairy cattle digest feed, wean healthier calves, and milk yield.
Finger millet is rarely used as poultry feed (Esele, 1986). Due to its lower protein and higher fiber content, it is of lower quality for poultry than maize, sorghum, and pearl.
Several trials found that finger millet can substitute safely up to 25% of maize grain (about 15% of the diet) without affecting weight gain, carcass yields, and immunity in commercial broiler diets. The inclusion also reduced the fat deposition in the thigh muscle, liver, and abdominal area compared to maize (Rao et al., 2005). At higher substitution levels, it depressed growth in the starting phase though this effect is less noticeable during the finishing phase.
It is important that the grain is fed grounded as whole finger millet depressed body weight and feed efficiency.
For Goats and Aquaculture
In some areas, Ragi straw is fed to goats but a higher protein supplement (broiler droppings or concentrates) should be given along for profitable results. In female goats, Ragi straw is known to induce better lactation. Millet pearls can be used in feeds for Nile tilapia fingerlings totally replacing energy and protein of corn without effecting performance and carcass quality of the animals.
Finger millet could be used as an ideal carbon source for biofloc to augment the growth and productivity of P. hypophthalmus under farming.
Millets seem to offer a promising alternative to expensive animal nutrition for dairy, aquaculture, and goats. The immediate actions would be to research and set standards for real time commercial applications, considering indigenous animals and ongoing animal husbandry practices. The Ministry of Animal Husbandry and the National Veterinary Institutes may take up extensive research projects and arrive at data that could be implemented to make animal husbandry economical and more profitable for farmers in the long run.