Researchers controlled- or limit-fed
Heifers began the study at four months of age and continued on their respective treatment until puberty at about 245 days of age. The researchers followed the heifers through the first 150 days of their first lactation. Here are some of the results:
Similar average daily gain. Heifers in both treatment groups gained about 1.82 pounds per day.
Better efficiency. Heifers fed the high-concentrate diet ate less dry matter, which gave them a slight edge on feed efficiency.
Same structural growth. Structural size and bodyweight did not differ between the two groups at puberty. However, high-concentrate heifers eventually had greater paunch girth than their high-forage peers.
Same calving age. Age at first calving averaged 23.4 months for both groups.
Same milk yield. Milk production through 150 days in milk was about 70 pounds per day for animals in the high-forage group. Production in the high-concentrate group was numerically higher at 76.5 pounds per day. However, this is not considered to be statistically different, or better than the performance of the high-forage group.
To read the abstract in the July 2007 Journal of Dairy Science, follow this link.