The ideal silage hybrid is the one that maximizes profitability under a specific set of conditions (i.e., your farm). A multitude of factors influence profitability, but for hybrid selection, the list can be reduced to:
1. Cost of production of the silage,
2. Effect the silage hybrid has on total diet cost, and
3. Effect on milk production.
To select the most profitable hybrid for your farm, you need to know how much it will cost to produce each hybrid, its yield and nutrient composition, the cost and nutrient composition of other ingredients, intake and milk production when cows are fed the silage, and the price of milk. And, you need to know this information months before the seed goes into the ground and more than a year before you will finish feeding the silage. The chance of you choosing the "perfect hybrid" is about zero. This article will provide some general guidelines that should assist you in narrowing your choices to a group of hybrids that are likely to be more profitable than the 'average' hybrid.
Cost of production
Differences in yield (first and foremost), seed costs, and agronomic traits (for example, insect resistance) are how hybrid affects production cost of silage. Based on the average corn silage yield reported in Ohio, silage yields among hybrids could vary by about 4 tons/acre. On average, we would expect corn silage from the lowest yielding hybrid to cost about $4/ton more than the highest yielding hybrid (assuming seed prices were equal but other variable costs increased with increasing yields). At typical feeding rates and assuming everything else is equal, that difference in production costs will increase feed costs about $0.10/cow/day. A much bigger consideration is the increased land needed. If yields are 25% less, you will need 25% more land to provide the same amount of corn silage for your herd. Is using that additional land for corn silage more profitable than growing corn grain? The answer will likely differ when corn grain is selling for $1.80/bu (December, 2005, Chicago price) compared with $3.60/bu (December, 2006, Chicago price). Increased ethanol production is likely to cause a long term (at least several years) increase in the price of corn, making corn grain production a profitable enterprise for many farmers. Under current conditions, you should usually select hybrids with above average yields (even with their generally higher seed costs).
Yield, however, cannot be the sole criteria when selecting a hybrid. A high yielding hybrid will usually reduce the cost of the silage but that may not necessarily reduce the cost of feeding your cows a balanced diet. In addition, with corn silage, the primary return will be via milk income; therefore, potential effects of silage hybrid on milk production must be a factor in the selection decision.
Effect of silage hybrid on total diet costs
Composition of silage varies among hybrids, and therefore, hybrid can influence the ingredients used in a diet. Currently, the greatest difference among hybrids is in the carbohydrate fraction (starch and fiber). The concentrations of neutral detergent fiber (NDF) and starch vary markedly among hybrids, but concentrations of NDF and starch are negatively correlated. Hybrids with high NDF concentrations usually have lower starch concentrations and vice versa. Dairy diets need to contain a certain amount of NDF from forages (approximately 16 to 20% of the dry matter) and a certain amount of starch (approximately 24 to 30%) to achieve good milk production and maintain the health of the cow. A hybrid with high NDF will reduce the amount of forage needed in the diet but will increase the amount of corn grain needed (vice versa for a high starch hybrid). These changes in ingredient composition of diets can affect the cost of the ration. If you expect supplemental starch (e.g., corn grain) to be relatively high priced compared with the cost of supplemental forage fiber (e.g., hay), then hybrids with above average starch concentrations should be considered. A hybrid with above average NDF concentrations would likely be a better choice if the opposite is expected. Forage fiber is expensive and even with today's high corn grain price, using corn silage hybrids that are very low in NDF (and high in starch) usually will increase the cost of the total diet, and hybrids with moderate or above average NDF concentrations are usually the best choice. The quality of the NDF (i.e., in vitro NDF digestibility, IVNDFD) is important when choosing hybrids with higher concentrations of NDF.
Effect of hybrid on milk production
Unlike for alfalfa, NDF concentration of corn silage has not been shown to have an effect on intake and milk production; however, in most lactation studies, cows fed corn silage hybrids with higher IVNDFD ate more feed and produced more milk than cows fed corn silage with lower IVNDFD. You should select hybrids with above average IVNDFD.
General approach, in order
1. Get the seed catalogs out,
2. Identify hybrids with agronomic traits you consider necessary (for example, disease resistance, rootworm resistance, etc.),
3. From that list, choose a set of hybrids with above average IVNDFD,
4. From that list, choose a set of hybrids with above average silage yields,
5. From that list, choose a set of hybrids with average or above average NDF concentrations (consider seed price), and
6. You should never grow a single hybrid on a farm, so pick a few hybrids from that list to plant (consider seed price).
A note on brown-midrib (bmr) hybrids
Using the guidelines above, bmr hybrids would never make the cut because yields are usually lower than average (on the other hand, IVNDFD is usually well above average). Several studies have shown that feeding bmr silage increases intake and milk yield compared with conventional hybrids. Studies have also shown the response to bmr silage is much greater for early lactation, high producing cows than lower producing cows. If you group cows by stage of lactation and have the ability to maintain a separate inventory of bmr silage to feed only to that group, bmr, even with the low yield, can be profitable.