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The “how” of body condition modification

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By Tyler Melroe, M.S., Beef Nutritionist, Hubbard Feeds

Managing a herd’s fertility is a continuous process in which one must plan for changing variables, such as weather and lactation. Because we are presently in the fall season, some may think it’s too late to manage body condition score (BCS) in their spring-calving cows. However, as soon as we know they’re bred, it’s time to start managing for future pregnancies. This article is not about why body condition score is important, but about how — and why — we manage it.

Managing maintenance

Whether we are looking to maintain cows or add condition, the first step is understanding what factors influence maintenance requirements. To keep this practical, we will relate these changes to three common feed ingredients (Table 1) and how many pounds of feed a good-milking, 1,300-pound cow would need to consume to maintain a proper BCS.

Table 1.  Net energy (Mcal/cwt) values for grass hay, corn grain and corn silage (dry matter basis)

 

DM, %a

NEga

NEma

Grass hay

85

26

58

Corn grain

85

65

98

Corn silage

35

47

75

a DM: dry matter; NEg: net energy for gain; NEm: net energy for maintenance

 

Lactation and pregnancy

The simplest way to reduce a lactating cow’s maintenance requirement is to wean her calf. The first question that should be asked is, “How much feed will be saved by early weaning?” While lactation declines from mid- to late lactation, energy is still required to produce milk. Table 2 describes the additional inputs needed to maintain BCS during late lactation.

Table 2.  Additional feedstuffs (pounds, as fed) per cow to maintain BCS, weaning at 148 vs. 240 days* 

 

Days since calving

 

148-168

169-189

190-210

211-240

Total

Grass hay

178

141

108

81

508

Corn grain

94

74

57

43

267

Corn silage

300

238

183

137

857

*Not providing these additional resources would cause a cow starting at BCS 5 to lose about half a condition score during this timeframe.

 

Weather’s role

Another influencer is the weather. In parts of the country where winter is more pronounced, the changes in daily requirements can be significant. Table 3 describes the additional feed needed for a clean and dry cow on a day that is slightly windy and has a temperature of 10 degrees Fahrenheit.

Table 3.  Daily added pounds of feed needed to maintain BCS on a 10oF day with a 10-mph wind

 

Pounds, as fed

Grass hay

10.2

Corn grain

5.4

Corn silage

17.2

 

Additionally, these effects are cumulative. For example, when feeding corn silage, not only does the cow need an additional 17.2 pounds for managing cold stress, but she will require another estimated 4.5 pounds when prolonging lactation. This equates to an additional 22 pounds of corn silage required daily, simply to maintain condition.

Adding condition

A common situation is trying to put a “little condition” on cattle. Findings by the National Research Council (NRC) in 2000 have provided us with the information necessary to determine the appropriate nutrition required to change condition (Table 4). While each condition score results in roughly the same change in weight for a given cow (80–100 pounds), the composition of gain changes (more fat, less protein). Thus, it takes more energy to achieve each pound of weight gain for a cow with a BCS 5 compared to one with a BCS 3. 

Table 4.  Energy reserves for cows with different body weight (BW) and BCS (NRC, 2000)

 

Mature BW (pounds) at BCS 5

BCS

1,200

1,300

1,400

1,500

3

172

186

200

214

4

196

212

229

245

5

226

245

264

283

6

264

286

308

330

7

311

337

363

389

*Mcal NE required or provided to change condition score

 

So, how is this information practically applied? Cow feeding decisions require the following considerations:

  • What change in BCS is desired?
  • How many days do we have to make this change?

Referencing the same 1,300-pound cow moving from a BCS 4 to a BCS 5 in 80 days, Table 5 represents the additional pounds of feed needed daily for 80 days to achieve this goal.

Table 5.  Additional feed per day for a 1,300-pound cow to move from a BCS 4 to a BCS 5 in 80 days

 

Pounds, as fed

Grass hay

14.4

Corn grain

5.5

Corn silage

19.0

 

Intake alone is not sufficient to increase BCS score. More energy-dense feedstuffs must be utilized.  Adding condition is extremely difficult in early lactation, especially when dealing with cold stress. This emphasizes the need to recognize the opportune times to add body condition and manage feed resources.

It is well established that proper BCS management is critical to a cow’s ability to reproduce. However, what isn’t as intuitive is what needs to be done to make the necessary changes. The information to help you make the appropriate changes is available; if you have a plan and seek products and answers that work, results will follow.