By Dr. Jeff Lehmkuhler
The extremely wet spring in the southeast resulted in hay fields being cut late when forage was physiologically mature. Mature forage has greater fiber content and less protein than vegetative forage. The ideal stage of maturity for cutting our cool-season forages from a quality and yield perspective is from boot stage, just prior to seed head emergence, to early flowering. Digestibility rapidly declines as plants advance in maturity. Mature forage cut for hay yields a double whammy to the beef cow. The forage is lower in digestibility yielding less energy and has a slower rate of fermentation leading to decreased intakes. Thus, mature forage can greatly lower the nutritional balance of a cow.
How bad can it be? The only way to really know is to test the hay. Sample the hay and send it off for analyses to find out the quality and work with a nutritionist to develop a feeding strategy. Beef cows in fair to good body condition (4+) at weaning require a diet containing approximately 48-55% TDN and 7-8% crude protein. Why the range? Variation in condition, energetic efficiency, intake, and environmental conditions impact the nutritional needs of beef cows. Much of the hay in Kentucky, Tennessee and other states in the upper Southeast is Kentucky 31 Tall Fescue infected with the wild-type endophyte.
The alkaloids produced by the endophyte are generally highest in the seed heads and mature hay has plenty of these. These alkaloids can reduce forage intake beyond that of the physiological maturity of the forage. Thus, late cut wild-type infected tall fescue hay would need to be higher in energy concentration to offset this reduced intake. However, this is contradictory to the relation of forage maturity and energy availability.
In order to provide adequate ammonia for the microbes in the rumen to thrive and digest the fiber, it is generally stated that a level of 7% available protein is needed in the forage or diet. Several hay samples this year fell below this threshold. The bugs essentially hit the wall and fiber digestibility suffers. This leads to longer rumen retention times and lower intakes. This rumen digestive physiology fact is often the basis to the old adage of a belly full of straw and starving to death. A small level of protein supplementation in these deficiency cases improves forage digestion and energy balance. In plain words, late cut tall fescue is problematic for late gestation and early lactation as it will not meet the nutritional needs of the cow at these phases of production often requiring some form of supplementation.
In many situations, correcting the protein deficiency by feeding 0.5 - 1 lb of protein will not rectify the energy deficit. For the extremely poor quality hay, the supplement level required to balance the energy and protein needs may be 7-9 pounds. A self-fed product supplying 0.75 lb of TDN a day is simply not able to compensate for the reduced energy contribution of the forage. By testing your hay and working with a nutritionist you can develop a strategic supplementation program.
This year's poor hay quality coupled with the extremely cold winter temperatures is beginning to be seen. This low energy hay combined with the increased energy for maintenance to compensate for the cold stress has resulted in some cows being in a negative energy balance or simply in a state of malnutrition. Cows pull from body reserves to support the increased energy needs lowering their condition. Often the long hair coats tend to mask this tissue loss and cows enter the calving season thin. During the last trimester fetal development increases nutrient needs greatly. Protein deficiencies during gestation can lead to weak calves. Trace mineral deficiencies can also occur resulting in white muscle disease from low selenium and poor calf health. Cows will lose even more condition as they go through the first eight weeks of lactation if the forage quality is poor. This will lower milk production and lead to poor calf performance.
For 1,400 pound beef cows that are in their first month of lactation with a potential of 20 lbs of milk and receiving hay that is 48% TDN and 8% crude protein with an intake of 1.8% of their body weight, the current Nutrient Requirements for Beef Cattle publication would indicate the energy and protein deficit to be 5 lbs of TDN and 0.86 lbs, respectively. Assuming a 1:1 mixture of soyhulls and corn gluten feed would contain 78% TDN and 16% crude protein on a dry matter basis, it would take about 7 lbs of supplement to meet the maintenance needs. Cows in good condition at calving and having the body reserves will mobilize tissue to support lactation.
Feeding less than the above level of supplement will be acceptable for cows with adequate reserves, but excessive mobilization of tissue can increase post-partum anestrous or the time from which she calves and comes back into heat. This lost time means lost pounds on the next calf crop. Cows that are thin at calving and lack the body reserves to mobilize to support lactation will suffer lower milk production, extended anestrous and in the most severe cases of malnutrition they may even die. To optimize reproduction, the research suggests cows should be consuming adequate nutrients to meet maintenance or slightly above.
As pasture green-up begins, don't be fooled by the cow. The early forage will be extremely high in water content. There will be little dry matter per acre resulting in energy expended to walk the fields and in cases with lactating cows they quickly mobilize tissue losing more reserves than if they were maintained on hay until the grass was 3-4 inches before turning out. Fresh cows on lush forage should have access to high magnesium mineral supplement to prevent grass tetany as well. Cows and calves are too valuable not to provide them with adequate nutrition to avoid deficiencies.
The moral of the story, it is too late to prevent nutritional inadequacies after you see symptoms of deficiency. Be proactive, attempt to cut this year's hay early and have all your hay tested this year. Then talk to your county agent, nutritionist or contact your beef specialist to develop a feeding strategy.