Milk Yield Differences

Cornell University, Ithaca, New York, U.S.A.

INTRODUCTION

Milk production is an integral component of the total life cycle of mammals. The term lactation is another term commonly used to describe this biological process. Milk production serves a number of functions. A primary function, in most species, is to provide nutrients for newborn animals. The milk produced in the first few days of lactation is called colostrum. Typically, colostrum contains a higher level of protein, fat, energy, and solids than milk produced in later lactation. Colostrum also provides a method of providing immunity to newborn animals. Milk and milk products are also utilized as a food source for humans in many parts of the world. The quantity of milk produced has increased in many species over time. These species have been genetically selected for milk yield and are managed for production of milk for sale and consumption by humans. The most common species used for this purpose are dairy cattle, goats, sheep, and water buffalo. The quantity of milk produced varies both within and among animal species.

MILK YIELD

Table 1 contains milk yield data for selected species on a total lactation length basis. This information provides averages for several breeds of dairy cattle, goats, deer, and water buffalo. The difference between the seven U.S. dairy breeds is 3189 kg of milk per lactation. There is also a large variation in herd average milk production within breed. As an example, Holstein herds in the United States may produce <7200 to >14,500 kg of milk per cow per year. Individual Holstein cows have produced in excess of 30,000 kg milk in a single lactation and >200,000 kg in total lifetime milk production. The milk yields for water buffalo in Table 1 are for animals selected and managed for producing milk. These yields are higher than would be expected for the same species in less intensively managed situations.

The production of milk requires the synthesis of large quantities of precursors by the animal. The milk of Holstein dairy cattle typically contains about 5% lactose. Thus, a dairy cow producing 45 kg of milk per day needs to synthesize about 2.25 kg of lactose on a daily basis. This cow also needs to synthesize 3 3.6 kg of glucose, 1.4 1.8 kg of microbial protein, and 1 1.2 kg of amino acids daily to support this level of milk production.

There are also milk production estimates for other animals that either have shorter lactations or are not continuously milked. Milk yield in beef cattle will vary depending on breed, genetic selection, and number of calves suckled. Reported daily milk production of Angus and Hereford beef cattle was 5.2 to 7 kg/day at peak yield.[5] Average peak milk for the Angus cows was 6.98 kg/day for the daughters of the high-EPD (expected progeny difference) bulls compared with 5.74 kg for daughters of the low-EPD Angus sires. The Hereford cows from the high-EPD bulls produced 6.07 kg/day at peak compared with 5.24 kg for the daughters of the low-EPD sires.

Milking sheep produce an average of about 3 kg/day during a 180-day lactation period.[6] These sheep are mainly of the East Friesian breed housed in large commercial flocks. Average daily milk production for ewes nursing either single or twin lambs over a 63-day lactation period ranged from 2.5 to 3.5 kg.[7]

Total milk production of sows nursing pigs was reported to vary from 7.8 to 13.8 kg/day during a 5-day period in early lactation (days 10 14).[8] Total daily yields were 8.2 to 12.4 kg for sows in late lactation (days 24 28) in the same trial. The higher yields are for sows suckling a larger number of pigs.

LACTATION LENGTH

The length of the lactation cycle varies greatly among various species of animals. A review paper indicated that lactation length can range from 4 to >900 days in various species of mammals.[8] Animals such as hooded seals, spiny rats, and elephant shrews had a 4 5-day lactation length. A lactation length of >900 days was found in some of the great apes. This same paper indicated that there was a positive relationship between adult female body mass and lactation length. This relationship is for animals not used in intensive milk production systems.

Table 1 Annual lactation milk yields

Lactation length Milk 4% FCM Milk Milk total

Lactation length Milk 4% FCM Milk Milk total

Table 1 Annual lactation milk yields

Animal

(days)

yield, kg

yield, kg

fat, %

protein, %

Year

Country

Dairy Cattle

Ayrshire

305

7,016

6,899

3.88

3.33

2003

US

Brown Swiss

305

8,045

8,093

4.04

3.54

2003

US

Guernsey

305

6,665

7,195

4.53

3.53

2003

US

Holstein

305

9,830

9,314

3.65

3.21

2003

US

Jersey

305

7,144

7,808

4.62

3.76

2003

US

Milking shorthorn

305

6,444

6,125

3.67

3.28

2003

US

Red and white

305

8,979

8,534

3.67

3.16

2003

US

Normande

305

6,649

7,018

4.37

3.6

2000

France

Swedish red

305

8,378

8,717

4.27

3.41

2001

Sweden

Swedish friesian

305

9,204

9,177

3.98

3.28

2001

Sweden

Danish red

305

7,553

7,791

4.21

3.56

2002

Denmark

Goats

Alpine

305

945

874

3.5

3.1

2003

US

LaMancha

305

765

734

3.73

3.24

2003

US

Nubian

305

679

742

4.61

3.79

2003

US

Oberhasli

305

668

642

3.74

3.07

2003

US

Saanen

305

871

811

3.54

3.07

2003

US

Toggenburg

305

840

752

3.3

3.0

2003

US

Others

Iberian red deer

238

224

475

11.5

7.6

2000

Spain

Water buffalo

270

2,524

3,808

7.39

4.5

2002

England

(From Refs. 1 4.)

FACTORS THAT INFLUENCE MILK YIELD

Many factors influence either daily or total lactation milk yield. The two key factors that control milk yield within an animal are genetics and environment. The heritability of milk yield in dairy cattle is estimated to be 0.25 to 0.3. This implies that 25 30% of the difference in milk yield among cows is due to genetics. The remainder of the difference is related to environment. The quantity and quality of the nutrients fed will also impact both milk production and composition.

The frequency of milk removal from the udder is another factor that will influence milk yield. In nursing animals, the number of animals being suckled will also affect milk yield. Sows nursing 12 pigs produced about 50 75% more milk per day than sows nursing 6 pigs.[8] Sheep nursing twin lambs had higher milk production over a 63-day lactation period than ewes nursing single lamb.[7] Dairy cattle milked three times per day produced about 3.5 kg more milk per day than cows milked twice daily.[9]

The use of recombinant bovine somatotropin (BST) is another tool that can be used to increase milk production in dairy cattle. The results of a field study using 15 dairy herds reported daily milk production increases of 3.6 to 5.5 kg in cows receiving exogenous BST.[11] The response to BST was greater in multiparous than primiparous cows in this study. Milk production to exogenous BST has also been reported to increase milk yield in beef cattle and goats.

There has also been interest in milking animals more frequently in the early part of the lactation cycle. A recent paper examined milking cows either three or six times daily for the first 21 days of lactation.[10] Both groups were then milked three times per day for the remainder of the lactation cycle. Peak milk yields were 57.0 and 51.1 kg per day for cows milked six or three times per day, respectively. Over the total lactation period, cows milked 6 times daily for the first 21 days produced 1118 kg more total milk.

LACTATION CURVES

The quantity of milk produced daily varies throughout the lactation period. In most animals, there will be a high, peak yield followed by a gradual decrease in daily milk production for the remainder of the lactation cycle. In dairy cattle, peak milk production occurs in the first 40 70 days of the lactation cycle for multiparous cows. The days to peak milk are usually slightly later in primiparous cattle. The decline in milk production after peak is 6 9% per month for multiparous cows, while the rate of decline for primiparous cows is 3 6%. Peak milk production in beef cattle and sheep occur at days of lactation similar to those in dairy cattle.

WHAT IS THE LIMIT FOR MILK YIELD IN DAIRY CATTLE?

One approach to this question is to examine the quantity of milk produced by world-record cows. The world record for a Holstein dairy cow is 30,805 kg in a 365-day lactation period.[11] The world record for a Jersey is 20,380 kg in a 365-day lactation.[12] Even though these are records for individual cows, they do provide an index of the potential of dairy cows for milk yield. It is probable that these records will be surpassed in the next 5 years.

CONCLUSION

Milk yield varies both within and among species due to a combination of genetic and management factors. The quantity of milk produced can be altered by the nutrient content of the diet provided. Other factors that can influence the quantity of milk produced include the number of animals suckled, frequency of milking, and BST. The biological limit for milk yield has not been defined. However, individual Holstein dairy cows have produced >30,000 lb of milk in a 365-day lactation and >200,000 kg in total lifetime milk production.

REFERENCES

1. http://aipl.arsusda.gov (accessed February 2004).

2. http://www.buffalomilk.co.uk (accessed June 2003).

3. http://www.milkproduction.com (accessed March 2003).

4. Landete Castillejos, T.; Garcia, A.; Molina, P.; Vergara, H.; Garde, J.; Gallego, L. Milk production and composition in captive Iberian red deer (Cervus elaphus hispanicus): Effect of birth date. J. Anim. Sci. 2000, 78, 2771 2777.

5. Minick, J.A.; Buchanan, D.S.; Rupert, S.D. Milk produc tion of crossbred daughters of high and low milk EPD Angus and Hereford bulls. J. Anim. Sci. 2001, 79, 1386 1393.

6. http://www.blacksheepcheese.com (accessed February 2004).

7. Cardellino, R.A.; Benson, M.E. Lactation curves of commercial ewes rearing lambs. J. Anim. Sci. 2002, 80, 23 27.

8. Auldist, D.D.; Carlson, D.; Morrish, L.; Wakeford, C.M.; King, R.H. The influence of suckling interval on milk production in sows. J. Anim. Sci. 2000, 78, 2026 2031.

9. Erdman, R.A.; Varner, M. Fixed yield responses to increased milking frequency. J. Dairy Sci. 1995, 78, 1199 1203.

10. Dahl, G.E.; Wallace, R.L.; Shanks, R.D.; Lueking, D. Hot topic: Effects of frequent milking in early lactation on milk yield and udder health. J. Dairy Sci. 2004, 87, 882 885.

11. Thomas, J.W.; Erdman, R.A.; Galton, D.M.; Lamb, R.C.; Arambel, M.J.; Olson, J.D.; Madsen, K.S.; Samuels, W.A.; Peel, C.J.; Green, G.A. Responses by lactating cows in commercial dairy herds to recombinant bovine somatotro pin. J. Dairy Sci. 1991, 74, 945 964.

12. http://www.holsteinuse.com (accessed January 2004).

13. Hayssen, V. Empirical and theoretical constraints on the evolution of lactation. J. Dairy Sci. 1993, 76, 3213 3233.

14. http://www.usjersey.com (accessed January 2004).

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