Cattle in Different Stages (Nutrition Perspective)

Growing Dairy Heifers

We have been stressing the desirability of having first calf heifers calve at less than 26 months of age. Some dairymen have been resistant to this because they felt that young heifers did not do well during their first lactation relative to older heifers. One of the keys to making the system work is getting the heifer to calve at an acceptable size (at least 1200 lbs. for large breed heifers and 800 for small breeds). This is weight after the calf is born. Heifers that reach this size generally do well and have the ability to peak at 70 or more lbs. of milk per day. In order to do this, Holsteins must average about 1.7 lbs. gain/day and Jerseys 1.2 lbs. after weaning.

Table 1 contains requirements for three ages of heifers. The 3-6 month group needs more nutrients per pound of feed than the 6-12 and 12 and older groups. Younger heifers consume less feed, so the nutrient density needs to be higher. Protein required drops from 16% for the young calf to 12% for the older heifers. Virginia Tech research suggests that energy content of diets for a given rate of gain should be adjusted according to housing and environmental conditions. Heifers reared in confinement housing, such as the Virginia Countersloped barn, require 10-20% less energy. Adjust pounds of grain fed per day based on observed gain. Notice that calcium and phosphorus concentration declines as the heifer gets older, but the other minerals do not change with age. Part of this is due to a lack of information about the requirements for some of these nutrients, especially the microminerals. The vitamins are expressed as amounts (International Units) and not concentration, and they actually increase as the heifer gets older. This would be true for all of the other nutrients if actual quantity was expressed instead of concentration. These tables of nutrient requirements for heifer growth are suggestions and represent nutrients required under optimal conditions. During cold, wet weather, energy requirements increase. Similarly, heifers heavily infected with intestinal parasites require higher levels of nutrients.

Nutrient Specifications for the Dairy Herd; Table 1

Table 1. Dairy cattle ration specifications for heifers, dry cows, and lactating cows

Heifers (Age, Mos)

Dry Pregnant Cows

Production Groupa

 

3-6

6-12

>12

High

Medium

Low

Maximum

Crude protein (% dry matter, DM)

13-16

12-13

12 12

16-18b

15-16

14-15

19

-

Acid detergent fiber (% DM)

22-29

29-33

33-38

35-45

19-21

21-24

24-28

-

Neutral detergent fiber (% DM)

-

-

-

-

27-32

32-40

40-48

-

TDN (% DM)

68-79b

66-68b

60-66b

60-66

72-78

68-72

63-68

-

Net energy (Mcal/lb)

.69-.80

.67-.69

.61-.67

.61 – .67

.74-.80

.70-.74

.64-.70

-

Calcium (% DM)

.52

.41

.29

.50 – .70c

.8-1.0

.75-.8

.7-.75

2.0

Phosphorus (% DM)

.31

.30

.23

.30 – .35c

.45-.50

.40-.45

.35-.40

1.0

Magnesium (% DM)

.16

.16

.16

.16

.30

.25

.20

.5

Potassium (% DM)

.80

.80

.80

.80

1.0

.90

.90

3.0

Sodium (% DM)

.10

.10

.10

.10

.18

.18

.18

-

Sulfur (% DM)

.16

.16

.16

.17

.25

.20

.20

.4

Iron (ppm)

50

50

50

50

60

50

50

1,000

Cobalt (ppm)

.10

.10

.10

.10

.10

.10

.10

10

Copper (ppm)

10

10

10

10

15

10

10

100

Manganese (ppm)

40

40

40

40

50

40

40

1,000

Zinc (ppm)

40

40

40

40

50

40

40

500

Iodine (ppm)

.25

.25

.25

.6

.6

.6

.6

50

Selenium (ppm)

.10

.10

.10

.10

.3

.3

.3

2.0

Vitamin A (I.U./day)

10,000

15,000

20,000

40,000

100,000

80,000

60,000

-

Vitamin D (I.U./day)

5,000

7,500

10,000

20,000

50,000

40,000

30,000

50,000

Vitamin E (I.U./day)

100

100

200

200-1000

500

400

300

-

aHigh and low group cows are assumed to be producing 20% above or below herd average; if feeding two groups the medium group specification should be the low group. High group cows would be mature Holsteins producing 80 or more pounds of 4.0% milk, middle group would be 80 to 50 pounds, and low group below 50 pounds. Special consideration should be given to first calf heifers and smaller dairy breeds. Ranges are what would be under normal conditions, but will vary with production level of herd, environmental conditions, etc.

bHeifers reared under confinement may need to have lower levels of energy to prevent deposition of fat in the mammary gland. Limit weight gain to 2 lbs/day or less.

bPregnant dry cows (large breeds) in the last two months of gestation should receive at least 60 grams of calcium per day, but not more than 100 grams. At least 30 grams of phosphorus should be in the ration. Reduce by 20% for Jerseys.

Dry Cows

Dry cow requirements are to maintain the cow plus fetal growth plus some weight gain. The range in energy is to accommodate situations where some body condition restoration is needed during the dry period. Indications are that .25 to .5 body condition units can be put on during the dry period with little adverse effect. The requirements for energy are higher than NRC in an attempt to ensure acceptable condition at calving. The other nutrients are similar to NRC except vitamin E, which has a range up to 1000 IU’s, a level that has been associated with improved udder health and reduced somatic cell counts. Close-up dry cows, cows in the last 2 to 3 weeks of the dry period, usually are placed on a transition ration that contains more nutrients than would be in a ration for the far-off cows. Energy would be at the upper end of the suggested range and fiber at the lower end. Sometimes protein is also increased as more supplement is fed. If anionic salts are fed calcium is many times increased to levels greater than suggested in the table. Calcium at 1.4% of the dry matter ration has been proposed as desirable when anionic salts are fed to the close-up dry cows. Care should be taken when using these salts because of palatability problems and the elevated calcium.

Lactating Cows

The lactating cows are categorized by production group within the herd. The high production group would be those top producers in the herd plus most cows less than 90 days in milk. A range is given in order to adjust for production of the herd. Lower producing herds wouldn’t need as much as higher producing herds, because cows are not milking at as high a level. The higher producers will many times be fed fat and, therefore, the calcium should be .9-1% and magnesium .30%. Requirements for potassium, sulfur, iron, copper, manganese, and zinc have been increased above NRC for the top production group.

First calf heifers should be given special consideration and remain in the top group to a lower production level than older cows. In other words, if older cows are moved out of the top group at 80 lbs. of milk, first calf heifers might be moved at 70 lbs. because body weight is less and they have less ability to consume feed. Therefore, they need a more nutrient dense ration. Not too many herds in Virginia contain three production groups. Most usually have two groups. In this case, the middle group specifications would be appropriate for the low group. The low group’s specifications would only be appropriate with cows in the final few months of gestation, producing less than 50 lbs. of milk. Herds that are capable of having three groups will often have a high production group composed only of older cows and a separate heifer group. Both groups would be fed the high group ration. The third group would be compatible with the middle group specs. The goal is to prevent extreme changes in nutrient concentration when switching groups. This minimizes the reduction in milk when switching groups.

Table 2 contains some terms nutritionists consider when attempting to balance the ration for rumen available carbohydrates and protein. Nonfiber carbohydrates are our best indication of the carbohydrates that are available for fermentation in the rumen. In most rations much of this fraction would be starch, primarily from grains and corn silage. At the nonfiber carbohydrate levels indicated, there should be adequate energy for the rumen to produce adequate microbial protein.

Protein is divided into that which is undegradable and degradable in the rumen. These two must add up to 100%. Generally, higher production warrants higher concentration of undegradable protein. Not all the research supports this idea and it is still uncertain when a response is expected. However, many nutritionists are recommending a source of rumen resistant protein in rations for high producing cows. Neither undegradable or degradable protein can be measured with a laboratory test. Therefore, book or average values are used, making this aspect of nutrition as much art as science. A recommendation is to have half of the degradable protein as soluble. Soluble protein indicates the amount of degradable protein that is rapidly degraded in the rumen and is easily mesured in the laboratory.

Updated Nutrient Specifications for the Dairy Herd; Table 2

Table 2. Recommended nonfiber carbohydrates and rumen degradable protein in rations for lactating cows.

Particulars

Days in Lactation

0-80

81-200

>200

Nonfiber Carbohydrates, %DM

38-42

35-38

33-35

Crude Protein, %DM

17-19

15-17

14-15

Rumen Undegradable Protein, %CP

38-40

36-38

32-36

Rumen Degradable Protein, %CP

60-62

62-64

64-68

Soluble Protein, %CP

30-31

31-32

32-34