Understanding hay testing and cattle nutrient requirements is important when feeding cattle through the winter

 

It is time to discuss nutritionally how to carry cattle through the winter. Hay is part of the winter cattle feeding strategy.  Whether hay is purchased or home raised, hay testing and understanding cattle nutrient requirements are key to efficiently feeding cattle through the winter with minimal                 supplementation, resulting in improved profit potential of the cattle operation.

 

Hay testing is important because it is the only way to know the exact nutrient value of the hay.  The main hay test components to look at are fiber, energy and protein. 

 

Neutral detergent fiber (NDF) and acid detergent fiber (ADF) are the forage fiber components evaluated in the hay test.  The NDF measurement is used to determine forage intake.  Cattle will consume 1.2% of their bodyweight in forage NDF daily.  The other fiber measurement, ADF, measures forage digestibility.  When forage NDF and ADF percentages increase, less forage intake and digestibility occur, which represents a poorer quality forage.  

 

Total digestible nutrients (TDN) and net energy are two forage testing measures of energy.  Total digestible nutrients looks at more than just energy, since TDN includes crude protein, carbohydrates, and fats. This measurement is a long–standing representation of energy.  As TDN increases, the forage has more energy, is higher quality, and is more likely to satisfy the energy needs of the animal.  Net energy, a more accurate representation of energy, accounts for the actual energy that the forage will provide to the animal.  Net energy is broken into categories with the first one that the animal uses being net energy for maintenance (NEm).  Once the NEm requirement is satisfied, the left over net energy will go to performance like lactation (NEl) or growth (NEg).  For beef cows, we look at NEm and for growing cattle in addition to NEm we also look at NEg.  An increase in forage net energy represents a better quality forage and increases the likelihood that forage is meeting the animal’s energy requirements. 

 

Two measurements used to evaluate forage protein content are crude protein and available protein.  Crude protein (CP) is calculated by multiplying measured forage nitrogen content by 6.25.  As forage quality improves, crude protein content increases improving the likelihood that forage will meet the animal’s protein requirements.  Hay that was baled wet and has a tobacco appearance and aroma may have reduced protein availability and absorption by the animal. Therefore, an available protein test should be used to determine the percentage of protein available for the animal.  When purchasing hay and not aware of the baling process, it is a good idea to do an available protein test so that you know how much forage protein is available for the animal to use.

 

In addition to knowing the nutritive value of the forage, understanding cattle nutrient requirements is necessary to determine if the forage is adequate or if supplementation is needed to meet animal needs for maintenance and production goals. You can break cattle into four categories based on their nutrient requirements, growing cattle, lactating mature cows, lactating first calf cows, and dry cows.  Growing animals have the highest nutrient needs.  Depending on body weight and gain expectations, TDN requirements range from 64% to 69% and CP requirements range from 10.6% to 12.8%.  The reason for growing cattle needing a high percentage is their intake is much lower than cows at approximately 12 to 14 lbs. of dry matter (DM) daily.

 

Cattle that have the next highest nutrient demand are first–calf lactating cows with 62% TDN and 10.7% CP, consuming  approximately 27 lbs. of DM daily. There is a high nutrient demand because these cows are lactating for the first time, still growing, and  becoming  reproductively sound prior to the next breeding season.

 

The final two groups include mature dry and lactating cows. Lactating cows have a higher percent TDN requirement (59 to 58 versus 54 to 50) and a higher percent CP requirement (9.8 to 10.5 versus 7.1 to 7.9) than dry cows.  Lactating cows have an increased nutrient requirement due to the nutrient  demand associated with milk production. Furthermore, as cows enter the final 1/3 of pregnancy, make sure to increase the nutrient content of the diet to the higher end of the dry cow nutrient need because of the growing fetus. Total DM intake for dry cows ranges between 21 lbs. and 24 lbs., with higher intakes as they get closer to calving.  Lactating cow DM intake ranges from 27 lbs. to 32 lbs.

 

The keys to feeding cattle efficiently through the winter includes determining hay nutrient content, sorting cattle into feeding groups based on nutrient requirements, and matching forage quality to cattle requirements with minimal grain/co-product based supplementation. In addition to appropriate supplementation, if hay is poorer quality than what is required by the animal, adjust future hay making or hay purchasing processes to get better quality hay. Cattle that use more forage to meet their nutrient requirements have less need for supplementation which can potentially improve profitability of the cattle operation.  Hopefully understanding a hay test will result in providing better quality hay for your cattle.  Furthermore, grouping and feeding cattle based on nutrient needs will lead to more efficient supplementation of cattle through the winter. This will potentially reduce supplementation cost leading to improved profit potential of the cattle operation.

 

 

Source: Patrick Davis, Livestock Specialist