Purdue University Bill Wheeler Department of Animal Sciences Lilly Hall West Lafayette, Indiana
Fourteen Holstein heifers, weighing from 279 to 467 kilograms, were paired on the basis of age and weight for random assignment to treatment sequences for a switchback design with 14-day experimental periods. The complete mixed rations consisted of approximately equal parts of dry matter from forage and concentrate with corn silage as the forage. Corn earlage and a supplement comprised the concentrate
portion.The supplement mixture, Table
26, consisted mainly of soybean meal with all ingredients combined to provide a
calculated 12.0 % crude protein, .35 % calcium, .35 % phosphorus, and .50 %
trace mineral salt in the total ration dry matter.Magnesium limestone was included in the
buffered ration at a level estimated to provide 198 grams per animal daily.Ration and chemical compositions are
presented in Table 27. Ingredients were blended once daily in a mixer wagon and fed in equal portions morning and afternoon to provide ad libitum feed intakes. Daily records were kept of feed offered and refused. A conventional stanchion barn was used for housing to facilitate individual feeding with sawdust as bedding. Animals were weighed at 14-day intervals prior to morning feeding.
Feed samples were obtained twice weekly, oven-dried at 60º C., equilibrated to air, composted, and ground for laboratory analysis. These samples were analyzed for moisture by oven-drying at 100º C., nitrogen by Kjeldahl, calcium (Willis), phosphorus (Harris and Popat ), and neutral detergent fiber (Van Soest ).
Fecal samples were obtained from fresh defecation material of each heifer on days 5 and 7 of the last week for experimental period. Each fecal sample was thoroughly mixed and pH determined by the use of a general purpose combination pH electrode. Fecal samples were oven-dried at 60º C., equilibrated to atmospheric conditions, composted, and ground for analysis. Dry matter of fecal samples was obtained by oven drying at 100º C. Starch content for both feed and fecal samples was determined by the procedure of Smith using –1,4– glucan glucohydrolase and the colorimetric method of Hodge and Hofreiter (1962). Statistical analysis of the data was by procedures of Brandt.
Table 26. Ingredient Composition of Supplement Mixture.
Trace mineral salt - - Guaranteed to contain not less than .50 % Zn, .40 % Mn, .25 % Fe, .05 % Cu, . 01 % I2, and .01 % Co. Vitamin premix - - Supplied 1679 I.U. Vitamin A and 300 I.U. Vitamin D per kilogram of ration dry matter.
Table 27. Ration and Chemical Composition of Complete Feeds.
Magnesium limestone -- Contained 21.14% Calcium, 13.14% Magnesium, and 0.18% Phosphorus on a dry Matter basis.
Table 28. Feed Intake, Weight Gain, Fecal Starch, and Fecal pH of Dairy Heifers.