Calculating dry matter intake to meet the nutrient requirements of the beef cow

Frank Wardynski<wardynsk@msu.edu>, Michigan State University Extension - August 02, 2013

Using large round bales to feed beef cows limits a producer’s ability to precisely meet her nutrient requirements. Accurately predicting feed intake and nutrient analysis of forages can help.

Many beef cow-calf producers across the Midwest feed large bales of hay in feeders as their primary feeding method. They keep hay in feeders nearly constantly by placing bales into a feeder once it is empty or contains sorted hay that is less palatable. Feeding cows in this manner to meet their specific nutrient requirements while minimizing feed wastage is difficult.

Table 1. lists nutrient analysis of various types of hay for Crude Protein (CP), Neutral Detergent Fiber (NDF) and energy reported as net energy for maintenance (NE_m) and total digestible nutrients (TDN). Protein and energy requirements are no more important than any other nutrients regarding cow performance; however, they are more expensive to provide and are more greatly impacted by forage quality variability. Early bloom alfalfa hay is clearly higher in CP and energy content while possessing less fiber than the other samples. Late bloom alfalfa is higher in protein, lower in fiber and similar in energy content when compared to the grass samples. Comparing nutrient analysis is critical to ensure meeting the nutrient requirements of the cow.

Table 1. Nutrient values for selected hay samples

	Early Bloom Alfalfa	Late Bloom Alfalfa	Early Cut Grass	Reed Canary Grass	Late Cut Grass
CP, percent	20.4	14.3	11.3	10.2	7
NDF, percent	40	51	58	70	62.5
NE_m, Mcal/pound	0.64	0.54	0.55	0.52	0.53
TDN, percent	62	53.6	55	55	53
Calculated DMI, pound of DM	35.75	28.04	24.66	20.43	22.88
Mcal/d	22.88	15.14	13.56	10.62	12.13

All of the forages in Table 1 would be able to meet the nutrient requirements of the cow if feed intake were high enough. Unfortunately feed intake is limited by fiber content. Cattle can consume 1.1 percent of their body weight in NDF. Dry Matter Intake is calculated in Table 1. Assuming a 1,300 pound cow with the equation of Cow Body Weight * .011/NDF, percent. Another way to look at this is for every 100 pounds of body weight, a cow can consume 1.1 pounds of her body weight in NDF. A 1,300 pound cow can consume 14.3 pounds of NDF per day. Megacalorie (Mcal) intake is calculated by DMI * NE_m. These calculations allow producers to estimate forage and energy intake.

These estimates can be compared to the nutrient requirements of a 1,300 pound cow at various stages of production shown in Table 2. Evaluating energy intake and requirements indicate that only early bloom alfalfa will meet the energy requirements of the early lactation cow. Only the alfalfa, both early and late meet the energy requirements of the cow during late gestation, while early cut grass hay is slightly deficient. The early cut grass sample indicates it contains greater energy values than the late cut alfalfa, however, due to the higher NDF values, the cow simply cannot consume enough forage to meet the energy requirements.

Table 2. Nutrient requirements of 1,300 pound cow at various stages of production as stated in the 2000 NRC, Nutrient Requirements of Beef Cattle.

	Early Lactation	Late Gestation	Dry, Mid Gestation
CP, percent	10-10.75	7-8.8	6-6.5
NE_m, Mcal/d	18.8	14.8	9.7

Michigan State University Extension recommends that beef producers utilize feed nutrient analysis to calculate DMI and nutrient intake. In situations that feed quality is at a level that allows for over consumption, strategies can be implemented to restrict feed intake. Producers can also evaluate feeds that will not allow for adequate nutrient intake and make necessary plans for needed supplementation. Producers who consistently test forages can develop a better understanding for the importance of forage quality and its ability to meet the cow’s nutrient requirements at various stages of production. For more information regarding more precisely feeding beef cows, contact me at wardynsk@anr.msu.edu or 906-884-4386.

This article was published by Michigan State University Extension. For more information, visit https://extension.msu.edu. To have a digest of information delivered straight to your email inbox, visit https://extension.msu.edu/newsletters. To contact an expert in your area, visit https://extension.msu.edu/experts, or call 888-MSUE4MI (888-678-3464).