Ear maize is an energy-rich feed suitable for all classes of ruminants, including dairy cows, growing and finishing cattle, and sheep (Kenyon, 2006; Ely et al., 1989). It is often fed ground and ensiled, and it is usually a valuable alternative to grain, for reasons both nutritional (energy value, presence of fibre) and practical (cost, ease of harvesting). Because ear maize contains a significant amount of roughage, it is a very safe feed with little risk of acidosis. However, the nutritional value of ear maize as a substitute for maize grain is variable, and it may not provide enough energy to livestock such as finishing steers. It will then require supplementation with protein and energy to achieve desired levels of performance (Lardy et al., 2010).
Energy value and degradability
The nutritional value of ground ear maize is about 88-90% that of maize grain and it is higher in fat (Ely et al., 1989; Gillepsie et al., 2009). The in vitro enzymatic starch degradability was found to be much higher in high-moisture ear maize than in dry maize grain (24h degradability of 90% vs. 53%) (Boas et al., 2010).
Ear maize is very palatable to ruminants. Cattle thrive easily on diets based on it (Gillepsie et al., 2009).
A meta-analysis of the literature showed that high-moisture ear maize (and high-moisture maize grain) tends to increase total-tract and rumen starch digestibility, and to decrease milk fat compared to dry maize grain (Ferraretto et al., 2013). High-moisture ear maize was found to combine well with maize silage for dairy cows, the diet mixing these two ingredients providing a good balance of soluble carbohydrates (Gillepsie et al., 2009). In Brazil, ear maize was found to be an energy source able to efficiently maintain milk performance (Paladini et al., 2013). In Poland, high-moisture corn cob mix included at 20% (diet DM) in the diet of high-yielding dairy cows did not have a significant impact on DM intake, energy corrected milk efficiency, fat content in milk, milk fatty acid profile and protein efficiency when compared to a similar amount of high moisture maize grain, but the harvesting costs were lower (Pysera et al., 2012). In the USA, high-moisture ear maize introduced at 38% (diet DM) in the diet of dairy cows resulted in dairy performance similar to that obtained with the same amount of cracked shelled maize (Broderick et al., 2002). Not all comparisons are favourable to ear maize: another USA trial found that feeding high-moisture ear maize compared with high-moisture shelled maize resulted in lower milk production, reflecting the lower energy content of ear maize, which is diluted by the presence of low-energy cobs (San Emeterio et al., 2000).
In a trial with lactating dairy cows in the USA, grinding high-moisture ear maize increased rate and extent of rumen fermentation, thus improving utilization of non-protein nitrogen by stimulating greater rumen synthesis of microbial protein. This resulted in higher yields of milk and milk components, and greater efficiency of nutrient utilization (Ekinci et al., 1997).
In an early trial with finishing steers in the USA, high-moisture ground ear maize was found preferable to dry ear maize, increasing gains in finishing cattle by 3% and feed efficiency by 10% (Beesom et al., 1956). Steers fed ear maize silage gained slightly faster and had a better feed efficiency than steers fed dry ear maize (Klosterman et al., 1960). In Brazil, ground ear maize was found equivalent to ground maize for grazing finishing steers in the rainy season (Porto et al., 2008). In a trial with steer calves in the USA, high moisture ear maize had a feeding value essentially equal to that of high moisture maize grain, but it increased DM yield of crop per ha by 18%, thereby increasing potential beef production per ha by 17% (Hill et al., 1995). In Serbia, partial or total replacement of maize grain with dry ear maize decreased DM digestibility and increased digestibility of crude fibre, whereas it increased intake and lowered performance (average daily gain) (Bačvanski, 1976).
In Canada, inoculation of high-moisture ear maize with homo- or hetero-lactic bacteria, or aqueous ammonia, resulted in marginal changes in fermentation characteristics leading to similar diet digestibility and comparable performance during the finishing phase of steers (Diaz et al., 2013).
Ear maize is a common and excellent source of energy for sheep, though it should preferably be ground and mixed with 5% molasses (Ely et al., 1989). However, literature is scarce. In the USA, it is recommended not to feed ground ear maize to lambs weighing below 30 kg (Umberger, 2009). Self-feeding brood ewes have been able to consume diet containing 34% ear maize (Ricketts et al., 1993). In a trial in Italy, ground ear maize silage fed at 32% (diet DM) to ewes and compared to the same amount of flaked barley gave lower nutrient digestibility, lower DM intake and lower milk performance than barley, though the ear maize diet did not have any adverse nutritional and metabolic effects (Vincenzi et al., 1999).