A beef producer recently asked me, “Can I stretch my hay supply with corn?” As is always the case, there are many variables that you need to think about.

This farm could buy corn or, if available, buy more hay. Therefore, I developed six rations to explore some options.

The rations below assume a 1,300-pound cow in late gestation eating 33 pounds of dry hay or corn on an as-fed basis, maintaining her body weight and body condition score (BCS).

The nutrient composition of the two hays used in these rations are in Table 2. While the question was specifically on replacing hay with corn, I also looked at purchasing hay. The daily cost to keep a cow is the metric for this discussion.

Here are the four rations.

By far, the lowest-cost ration is utilizing later-cut, or more mature, hay — No. 3. This reinforces the fact that matching nutrient requirements with nutrient demand optimizes animal performance and cost.

Nonlactating mature beef cows have low nutrient requirements. Forages of higher quality are best used for growing cattle that are on the farm, or perhaps selling. Even if both hays are produced on-farm and assumed to have the same cost of production, the hay with a higher nutrient quality is worth more. If supply is not limiting, then the adage of “market the best and feed the rest” holds.

Rations 4, 5 and 6 supplement hay with corn at various rates. Again, the low-cost ration involves using the lower-quality hay and supplementing with 5 pounds of corn. Ration 4 uses the rule of thumb that you can replace 3 pounds of hay with 2 pounds of corn. Other than ration 5, this supports a cow at the lowest cost.

Here are considerations in developing the diets:

Cow body weight and condition. Heavier cows eat more. Cows with a BCS lower than 4 also require more feed to keep warm.

Feeding environment. Poor environmental conditions increase nutrient requirements, meaning she will have to eat more just to maintain body condition. Eating more will increase feed costs up to 15%.

Nutrient composition. A forage analysis gives you the information you need to meet the cow’s requirements and optimize feed cost. This is especially true with forages, as nutrient composition varies with species and date of harvest. Here is an example:

In the Northeast, crude protein is generally not the limiting nutrient in mature beef cow rations. The CP requirement of a mature cow is 8%. Over the past 16 years, the Dairy One forage lab has reported the range in CP levels for dry, mostly grass hay was 8.1% to 16.7%. Supplementation above requirements costs money.

Cost and supply of feed ingredients. While the price of a feed ingredient varies, the critical factor on which to make a decision is the dollar per pound of nutrient. Relative to recent years, the price of corn is high, making it less attractive as a supplement. On the other hand, if hay supply is short, the price of the total digestible nutrients is equal to lower-quality hay.

Finally, one more adage: “The eye of the master fattens the cow.” While a blunt tool, if cows are losing body condition score, then an evaluation of ration quality or quantity is required.

Baker is a senior Extension associate in the Cornell Department of Animal Science.