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POSILAC® and Nutrition

 

Key Points:

  • Bovine somatotropin has no effect on the efficiency of nutrient utilization.
  • Managers who encourage maximum dry matter intake are expected to profit maximally from use of POSILAC® and will experience higher overall milk production.
  • Dry matter intake of cows supplemented with POSILAC will increase sufficiently to support increased milk production.
  • Responses to POSILAC are greatest when quality feed is available for consumption at least 20 hours a day.

Nutrition requirements of cows supplemented with POSILAC are the same as that of nonsupplemented cows producing at similar levels. Controlled studies1,2,4,5 have demonstrated that supplementation with bovine somatotropin does not change nutrient requirements per unit of milk produced nor does it change the digestion characteristics of the diet. Therefore, the ration balance required for cows supplemented with POSILAC bovine somatotropin will depend on body weight and milk production just as it does in nonsupplemented cows.

Controlled studies1,2 demonstrate that bovine somatotropin has no effect on the efficiency of nutrient utilization. Nutrients are directed away from other body tissues toward the mammary gland.3,4,5 These same studies show that basal metabolism and maintenance requirements are unaffected by somatotropin supplementation. Slight increases in body temperature are associated with higher milk yields.

After exhaustive research on the subject, the National Research Council (NRC) publication, Nutrient Requirements of Dairy Cattle, recognizes only body weight, milk production, milk fat test, and expected gain or loss of body weight as factors that affect nutrient demand.6

In the dairy cow, fat covering is an indicator of the amount of stored energy. Cows without adequate body reserves are prone to disease, metabolic disorders, impaired reproductive efficiency, and reduced milk production. In heifers, lack of body reserves will delay breeding and will lower milk production after calving.

Excessively fat cows, on the other hand, are predisposed to calving difficulties, fatty liver after calving, and often death. This condition has been termed Fat Cow Syndrome. Even cows that recover from this condition experience lower milk and butterfat production as well as increased risk of other disease conditions. Heifers that are fat at puberty fail to develop their full mammary gland capacity, resulting in lower lifetime production. Problems of repeat breeding are also reported for overly fat heifers at puberty.

The body fat covering of dairy cattle changes with different stages of lactation. Fresh cows lose body fat because they are unable to eat enough to meet the energy requirements for their high milk production. Late lactation and dry cows can add large amounts of body fat because they are able to take in more energy that they require for the amount of milk they produce.

Dairy farmers need to be aware of the body condition of their cows and heifers so that they can adjust management practices and feed rations as needed.

The body reserves of dairy cows are evaluated by a procedure known as body condition scoring. When body condition scoring the fat covering the rump and loin is evaluated and the cow is given a numeric score based on this evaluation. Body condition is scored between 0 and 5 with half scores in between. This gives a total of 11 possible body scores. Use of the body condition score system enables a farmer to accurately evaluate the body reserves of a cow and describe it in an easily understood, consistent way.

In long-term studies with bovine somatotropin8,9,10 dry matter intake was increased to a level that would support increases in milk production. This increase in dry matter intake occurred at variable times after initiation of POSILAC treatment, but generally within 3-5 weeks.

This implies that those managers who encourage maximum dry matter intake by lead feeding would be expected to profit maximally from POSILAC as well as to experience higher overall milk production. This also implies that cattle selected for supplementation with POSILAC should have adequate body condition for their stage of lactation.

Because the increase in dry matter intake does not occur for several weeks after initiation of treatment, initially the nutrients for increased milk production will come from body scores.3 Loss of body condition after supplementation with somatotropin may occur if cows move into a negative energy balance.11,12,13 This transitory condition loss corresponds to between 1/4 and 1/2 of one body condition score.14 This agrees with theoretical energy balance calculations, assuming that one body condition score is between 120 and 180 pounds of body weight.

Ultimately, dry matter intake determines the productive level of any herd of dairy cattle.15 Suggested nutrient levels, which optimize dry matter intake for animals producing at various production levels, are presented in Table 1. These were developed from NCR recommendations and from field experience.16

Table 1
Approximate desired nutrient concentration in total ration dry matter for stated amount of milk

Nutrient Dry Milk production lbs/day
<40 41-45 46-70 71-85 86-100 >100
Mcal NEI/lb .58 .69 .73 .75 .77 .78 .78
Protein % 13 13 15 16 17 18 18
ADF % (minimums) 27 21 21 21 19 19 19
NDF % (minimums) 35 28 28 28 25 25 25
Calcium % .40 .70 .75 .80 .85 .90 .90
Phosphorus % .29 .35 .40 .45 .50 .50 .50
Magnesium % .20 .25 .25 .25 .25 .25 .25
Potassium % .8 1.0 1.0 1.0 1.1 1.2 1.2
Sulphur % .2 .2 .2 .2 .2 .23 .23
Salt (NaCl) % .2 .45 .45 .45 .45 .46 .47
Iron ppm 100 100 100 100 100 100 100
Zinc ppm 50 50 50 50 50 50 50
Copper ppm 12 12 12 12 15 15 15
Iodine ppm .4 .6 .6 .6 .6 .6 .6
Selenium ppm .3 .3 .3 .3 .3 .3 .3
Cobalt ppm .1 .1 .1 .1 .1 .1 .1

Because of increased dry matter intake and the constancy of nutrient demand, cows supplemented with POSILAC have no increased requirements for concentrate, added fat, ruminally inert fat, protein, undegradable intake protein, minerals, or trace minerals beyond those of unsupplemented cows producing at the same levels.

Different researchers have proposed various schemes for feeding the bST-supplemented cow including increasing the amount of grain fed,17 feeding a single, high-energy Total-Mixed Ration ad libitum,18 increasing the amount of energy,19 increasing the amount of ruminally bypassed fat,20 or increasing total protein and undegraded intake protein.21 To date all of these schemes have shown no or very low effects on somatotropin response. At present, encouraging increased dry matter intake is the only proven strategy for feeding the cow treated with POSILAC.22 In a large field study,13 cows were found to respond well to POSILAC over a wide range of ration nutrient composition.

At present, NRC recommendations for ration formulation are the best-known guidelines. These guidelines may need to be updated as new published studies on the role of fats and proteins become available. However, changes in ration balance will depend on production levels and body size, not POSILAC use.

Preliminary studies have demonstrated that POSILAC responses are greatest when feed is available for consumption at least 20 hours a day.23 Likewise, it has been shown that when forage quality is poor, POSILAC response appears to be reduced. Changes in ration balance when forage quality is low may mitigate these effects.

References

  1. Tyrell HF, Brown ACG, Reynolds PJ, Haaland GC, et al: Effect of bovine somatotropin on metabolism of lactating cows: Energy and nitrogen utilization as determined by respiration calorimetry. J Nutr 1988;118:1024.
  2. Robinson PH, de Boer G, Kennelly JJ: Effect of bovine somatotropin and protein on rumen fermentation and forestomach and whole tract digestion in dairy cows. J Dairy Sci 1991;74:3505.
  3. Peel CJ, Bauman DE: Somatotropin and lactation. J Dairy Sci 1987;70:474
  4. Hart IC: Altering the efficiency of milk production of dairy cows with somatotropin, in Garnsworthy PC (ed): Nutrition and Lactation in the Dairy Cow. London, Butterworths, 1988, pp 232-247.
  5. McBride BW, Brown JL, Burton JH: Review: The influence of bovine growth hormone (somatotropin) on animals and their products. Res Dev Agricult 1988;5:1.
  6. National Research Council. Nutrient Requirements of Dairy Cattle. 1988.
  7. Patton RA, Bucholtz HF, Schmidt MK, Hall FM: Body Condition Scoring - A Management Tool. Michigan State University, East Lansing, MI. 1988.
  8. Bauman DE, Eppard PJ, DeGeeter MJ, Lanza GM: Responses of high-producing cows to long-term treatment with pituitary somatotropin and recombinant somatotropin. J Dairy Sci 1985;68:1352.
  9. Phipps RH, Weller RF, Craven N, Peel CJ: Use of prolonged-release bovine somatotropin for milk production in British Friesan dairy cows. Effect on intake, milk production and feed efficiency in two consecutive lactations of treatment. J Agricult Sci 1990;115:95.
  10. Hartnell GF, Franson SE, Bauman DE, Head HH, et al: Long-term evaluation of sometribove, recombinant methionyl bovine somatotropin, in a prolonged release system in lactating dairy cows-production responses in a dose titration study. J Dairy Sci 1991;74:2645.
  11. McDaniel BT, Fetrow J, Harrington BD, Bell WE, Rehman JD: Factors affecting response to recombinant bovine somatotropin. J Dairy Sci 1990;73(Suppl 1):159(Abstr.).
  12. Thomas JW, Samuels WA, Madsen KS: Use of sometribove, USAN (recombinant methionyl bovine somatotropin) in a prolonged release system in commercial dairy herds. J Dairy Sci 1989;72(Suppl 1):450(Abstr.).
  13. Thomas JW, Erdman RA, Galton DM, Lamb RC, et al: Responses by lactating cows in commercial herds to recombinant bovine somatotropin. J Dairy Sci 1991;74:945.
  14. Ferguson JD: Interactions between milk yield and reproduction in dairy cattle, in Meeting the Challenges of New Technology. St. Louis, MO, Monsanto Technical Symposium. Monsanto Agricultural Group, 1989, pp 35-44.
  15. Patton RA: Dry matter intake. Department of Animal Science monograph, Michigan State University, East Lansing, MI. 1987.
  16. Bucholtz HF, Thomas JW, Walter JP, Patton RA, Hayes ST: Approximate desired nutrient concentrations in total ration for slated amounts of milk. Spartan Dairy Ration Evaluator, Cooperative Extension Service, Michigan State University, East Lansing, MI. 1987.
  17. Tessman NJ, Kleimans J, Dhiman TR, Radloff HD, Satter LD: Effect of dietary forage:grain ratio on response of lactating dairy cows to recombinant somatotropin. J Dairy Sci 1988;71(Suppl 1):121(Abstr.).
  18. Hutjens MF: Dairy nutrition applications. Dairy Forum, Production Medicine - Managing the Whole Picture. St. Louis, MO, Monsanto Agricultural Group, 1990.
  19. Lormore MJ, Muller LD, Deaver DR, Griel LC, Jr: Early lactation responses of dairy cows administered bovine somatotropin and fed diets high in energy and protein. J Dairy Sci 1990; 73:3237.
  20. Chalupa W, Galligan DT: Nutritional implications of somatotropin for lactating cows. J Dairy Sci 1989;72:2510.
  21. McGuffey RK, Basson RP, Snyder DL, Block E, et al: Effects of sometribove sustained release administration on the lactational performance of dairy cows. J Dairy Sci 1991;74:1263.
  22. Franson SE, Cole WJ, Hoffman RG, Meserole VK, et al: Response of cows throughout lactation to sometribove, recombinant methionyl somatotropin, in a prolonged release system - a dose titration study. Part 1. Production response. J Dairy Sci 1989;72(Suppl 1):451 (Abstr.).
  23. Patton RA, Heald CW: Management of bST-supplemented cows, in Halberg MC (ed): Bovine somatotropin and Emerging Issues - An Assessment, Boulder, CO, Westview Press, 1992, p 73.

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