Importance of Sire X Ration Interactions in Production and Feed Intake Traits of Dairy Cattle

Lactation records of 228 first lactation Jerseys were utilized to assess the importance of sire ration interactions. Daughters of 13 sires were divided randomly into two groups at calving and assigned to either an all forage ration or a forage plus grain ration. Data were analyzed by least squares methods with year-seasons, sires, rations, and sire rations interactions included in the model. Ration differences were large and indicatire of the stres~ of the all forage ration. The all forage group produced 83% as much milk, consumed 9.6% more forage but only 58% as much estimated net energy, and was more efficient than the forage plus grain group. The sire ration interaction approached significance for milk and fat-corrected milk production (.10 > P > .05) but contributed less than 4% of the total variation. The sire ration interaction was significant for total estimated net energy Consumed and gross efficiency. This interaction may be because the amount of grain fed in the forage plus grain group was controlled by production.