A High Roughage System for Raising Calves Based on Early Development of Rumen Function. VI. Influence of Hay to Grain Ratio on Calf Performance, Rumen Development, and Certain Blood Changes

Early establishment of mature type rumen function encouraged in young calves by feeding rations high in roughage along with fresh cud inoculations has been shown to be an aid in producing low cost dairy herd replacements (5,6,7,15,16).Iu this experiment a study was made of the effects of feeding three different ratios of hay to grain (4:], 3:2, 2:3) and an exclusive milk diet on feed consumption, growth, and efficiency of feed utilization.Also measured were changes with age in rumen volatile fatty acids, rumen pH, rumen microorganisms, blood glucose, and blood cholesterol in calves fed the various rations. EXPERIMENTAL PROCEDURETwelve Jersey and nine Holstein calves were assigned to one of three groups at birth to be fed either a 4:1, 3:2, or 2:3 ratio of hay to grain.After a 3-day colostrum feeding period whole milk was fed twice daily at the daily rate of 1 lb.per 10 lb. of birth weight.No milk was fed after 7 weeks.Beginning on the fourth day and continuing to 12 weeks of age, chopped, good quality, mixed clover-timothy hay (11.5% protein) was offered free choice.In order to obtain the hay to grain ratio desired a simple (18% protein) grain mixture was fed, the amount being regulated by the quantity of hay being consumed.Fresh warm cud inoculations taken from older cattle in the herd were given weekly for the first 6 weeks.Salt, water, and steamed bonemeal were provided free choice in each pen.For purposes of comparison with calves fed hay and grain, four Jersey calves were fed exclusively on whole milk to 12 weeks of age at the daily rate of approximately 1 lb.per 10 lb. of body weight.These calves were maintained without bedding, with Neomat pads on the pen floor.Records were kept of daily feed consmnption, weekly body weight changes, and withers height at birth and at 12 weeks of age.Whole blood glucose, determined by the method of Somogyi (20), and plasma cholesterol, determined by the method of Saifer and Kammerer (18), were measured at weekly intervals throughout the 12-week experimental period.