A recent study looked at whether these advantages were truly coming from forages or just added fiber in the diet. Total dry matter intake and rumen pH was higher in forage supplemented calves than those offered a high (or low) NDF calf starter. Although simply buying a concentrate with a higher fiber level may be easier, it appears to be more beneficial to provide forage in the calf diet as the same benefits aren’t seen through raising the fiber content of a concentrate.
The type of forage offered to calves can have different effects. In general feeding legume forages results in higher intakes of the forage itself, but doesn’t result in greater intakes of concentrate or total dry matter intake. Calves offered legume forages tend to have a higher weight of the GI tract as a percent of body weight than calves offered just starter grain, or starter grain and grass hay. This indicates that feeding legumes may appear to be beneficial when evaluating weight and gains, but are actually just adding to gut fill and not carcass weight.
Grass hays and silages have been shown to produce greater average daily gains and total dry matter intake. Castells et al. (2012a) studied the effects of six different forage sources; average daily gain of calves offered oat hay, triticale silage, and barley straw were found to be 21-28% greater than calves fed only concentrates.
Any farm that raises its own replacement animals is essentially raising the future of their farm, since calf performance and growth is vitally important. Achieving greater growth and gains of calves should be a high priority on any dairy farm and can be achieved with the correct supplementation of a forage and a concentrate. Providing a good quality grass hay/silage in an ad libitum manner, separate from but in conjunction with a concentrate starting in the first weeks of life and continuing through the post weaning period, will maximize calf performance and growth.