This past summer was not good for making hay. That said, the hay’s resulting nutrient quality is less than ideal. Cows need to calve in a body condition score of 5.0 – 5.5. Will this year’s hay support this goal?
The nutrients of greatest practical concern to beef producers are energy (TDN or total digestible nutrients), crude protein (CP), calcium (Ca), phosphorus (P) and vitamin A. Other nutrients such as salt and various trace minerals are certainly important, but these requirements are generally met by feeding a balanced loose mineral. The major exception is the requirement for selenium, which can be met by injection or feeding. In this article I’ll focus on the primary nutrients, energy and protein.
Nutrient requirements are affected by stage of production, cow weight, milk production and environmental conditions. First, it’s important to determine the requirements for energy and protein. Table 1 provides information based on whether she’s dry or lactating, frame size (weight) and when lactating, how much milk she produces. Using this table, a frame size 7 cow that produces 18 pounds of milk requires 12.5 pounds of TDN and 1.9 pounds of crude protein (CP) when she is dry and increases to 14.6 pounds of TDN and 2.5 pounds of CP when lactating. Note the jump in requirements as she begins lactating. This is one reason many producers have moved their calving season later, when pasture is ready.
Use Table 2 to determine milk production of your cows. Again using the frame 7 cow, if she weans a 537-pound calf at 7 months of age, then her peak milk production is 12 pounds/day. If she weans a 607-pound calf at 7 months her peak milk is 24 pounds.
These guidelines hold true with the assumption that the cow is eating at least 2.2 percent of her body weight in dry matter (DM). Therefore the frame 7 cow should be consuming 29 pounds (1,320 pounds × 0.022 = 29). For dry hay this converts to 32 pounds/day, because dry hay is usually 90% DM (29 pounds ÷ 0.90 = 32). When feeding a wet feed such as baleage, the value would be greater. For example if the percent DM of the baleage was 60, the 1,320-pound cow would need to consume 48 pounds per day (29 pounds ÷ 0.60 = 48).
Finally, poor environmental conditions increase requirements due to extra energy expended to keep warm (Table 3). If housed outside with no wind protection, but kept dry, this 1,320-pound cow would need to consume an additional 0.9 pounds of TDN per day.
The hay I chose for this example (Table 4) typifies a lot of dry hay that was made this summer – first and second cut all rolled into one bale. Can we feed cows on this poor quality feed? The answer is yes, quite nicely.
Nutrient requirements are the lowest during the dry period. This is a period of time that putting on condition after weaning should be the goal. Assuming that the cows are eating 32 pounds hay/day as calculated, this late-cut hay will meet the non-lactating cows requirement at least through mid-gestation. This is seen in the positive balance TDN and CP of 3.0 pounds and 0.2 pounds, respectively.
However, as she gets closer to calving the energy balance is only +0.8 pounds and the CP balance is negative. Long-term negative energy balance leads to loss in body condition, which affects calf vigor, colostrum quantity and quality, and speed at which she rebreeds. If this period of body loss is short (\<30 days) it will not have a long-term negative affect. So, if these are April calving cows that will go to lush pasture by mid-May, then energy is not as large a concern as CP. Negative protein balance also affects colostrum quality, lowering the calf’s ability to fight off infection at birth and successive periods of stress.
Fortunately you were able to make some decent quality second-cut hay, which is 87 percent DM, 62 percent TDN and 15.2 percent CP. Can you make up the 0.4-pound CP deficit with this hay? To determine the amount of second-cut hay to feed: 0.4 pounds CP ÷ 0.152 CP = 2.6 pounds of second-cut hay. Divide this by 0.87 to get the “as fed” amount, and you need to feed 3.0 pounds of the second-cut/herd/day. This calculation can be done with any feed that will provide additional protein: soybean meal, dried distiller’s grain and shelled corn. It comes down to economics and convenience.
Many variables can affect the results. Do you really know the weight of the cows? Do you have a forage analysis? Do you know weaning weights of your calves? Are they consuming at least 32 pounds/day? What are the climatic conditions? The bottom line is that while you can apply the best science, you need to observe your cattle. An old adage that says “the eye of the master fattens the cattle” still applies today. Watch the body condition score. If the cows drop below 5.0 – 5.5, then a change is needed: greater intake, better quality hay or supplementation with grain. Cows that calve in a BCS less than 5 create a whole set of problems for the cows, calves and you.
Resource: “Feeding Cows and Their Nursing Calves” Fact Sheet 1300b. Cornell Beef Production Manual, Revised and abbreviated May, 2013. Michael J. Baker, Danny G. Fox and Phillip D. George (original authors).