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Invited Review: Production and Digestion of Supplemented Dairy Cows on Pasture

Invited Review: Production and Digestion of Supplemented Dairy Cows on Pasture,10.3168/jds.S0022-0302(03)73581-4,Journal of Dairy Science,F. Bargo,L.

Invited Review: Production and Digestion of Supplemented Dairy Cows on Pasture   (Citations: 84)
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Literature with data from dairy cows on pasture was reviewed to evaluate the effects of supplementation on intake, milk production and composition, and ruminal and postruminal digestion. Low dry matter intake (DMI) of pasture has been identified as a major factor limiting milk production by high producing dairy cows. Pasture DMI in grazing cows is a function of grazing time, biting rate, and bite mass. Concentrate supple- mentation did not affect biting rate (58 bites/min) or bite mass (0.47 g of DM/bite) but reduced grazing time 12 min/d per kilogram of concentrate compared with unsupplemented cows (574 min/d). Substitution rate, or the reduction in pasture DMI per kilogram of concen- trate,isafactorwhichmayexplainthevariationinmilk response to supplementation. A negative relationship exists between substitution rate and milk response; the lowerthesubstitutionratethehigherthemilkresponse to supplements. Milk production increases linearly as the amount of concentrate increases from 1.2 to 10 kg DM/d, with an overall milk response of 1 kg milk/kg concentrate. Compared with pasture-only diets, in- creasing the amount of concentrate supplementation upto10kgDM/dincreasedtotalDMI24%,milkproduc- tion 22%, and milk protein percentage 4%, but reduced milk fat percentage 6%. Compared with dry ground corn, supplementation with nonforage fiber sources or processed corn did not affect total DMI, milk produc- tion, or milk composition. Replacing ruminal degrad- able protein sources with ruminal undegradable pro- tein sources in concentrates did not consistently affect milk production or composition. Forage supplementa- tion did not affect production when substitution rate was high. Fat supplementation increased milk produc- tion by 6%, without affecting milk fat and protein con- tent. Increasing concentrate from 1.1 to 10 kg DM/d
Journal: Journal of Dairy Science - J DAIRY SCI , vol. 86, no. 1, pp. 1-42, 2003
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