A comparison of two complete rations for their effect on intake, production and energy balance of dairy cows and first lactation heifers

During the winters of 1975-76 and 1976-77, 76 Holstein cows and first lactation heifers were subjected to an 18 week continuous feeding trial beginning the week of their calving. Two complete rations varying in forage:concentrate ratio were fed; Ration 1 - 37:62 on a dry matter basis plus 4.5 kgs of alfalfa hay and 2.7 kgs of concentrate fed in the milking parlor, and Ration 2 - 54:46 on a dry matter basis plus 2.25 kgs alfalfa hay and 2.7 kgs of concentrate in the parlor. Thus there were four treatment groups: a) first lactation heifers receiving Ration 1, b) second or more lactation cows receiving Ration 1, c) first lactation heifers receiving Ration 2, and d) second or more lactation cows receiving Ration 2. Intake was considered both as complete ration dry matter, and with inclusion of alfalfa hay and parlor concentrate, total ration dry matter. Daily intake of complete ration dry matter was a) 9.75, b) 11.44, c) 9.54, and d) 12.32 kgs for the respective treatment groups showing a significant difference due to age (P < .05) but not to ration. Daily total ration dry matter consumption was a) 16.28, b) 17.97, c) 14.03, and d) 16.80 kgs, respectively with (b) signi-ficantly higher and (c) significantly lower (P < .05) than (a) or (d). Daily fat corrected milk production was a) 24.42, b) 29.63, c) 25.29, and d) 30.78 kgs respectively being significantly affected by age (P < .05) but not by ration. Apparently the higher proportion of concentrate in Ration 1 allowed higher total consumption and a closer equilibration between energy intake and requirement although no increase in milk production was noticed.