A beef calf typically nurses its dam for 6 to 8 months, while most dairy calves receive a liquid ration for just 6 to 8 weeks. One of the nutritional challenges of this contrasting scenario is delivering optimal levels of fat to dairy calves.
A team of European researchers led by well-known calf and heifer researcher Alex Bach recently published a study in the Journal of Dairy Science that explored a new method for increasing fat intake in young dairy calves via the starter ration. The researchers noted that previous attempts to boost fat levels in starter grain were mostly unsuccessful because:
- Inclusion of high levels of fat in starter grain can negatively influence rumen development, because it provides a boost of energy to the calf, but very little to rumen bacteria.
- When fat and fermentable ingredients are combined in one pellet, fat may physically impregnate fermentable compounds, limiting bacterial access to fermentable particles and thus hampering potential microbial growth and rumen development.
- While rumen-inert fat sources are available via ingredients such as hydrogenated fat prills and calcium soaps, their inclusion has been shown to compromise both solid feed intake and pellet quality. Feeding these fat sources separately is not an option because of their poor palatability and relatively small particle size, which would cause them to settle out of rations and be easily sorted.
As an alternative, the European researchers explored using extrusion and vacuum-coating feed technology, which commonly is used in the manufacturing of fish and pet feeds. The similar size of these pellets offered an opportunity to homogenously mix them with conventional pellets with a lower risk of sorting by calves.
The team conducted a 4-month trial in which 75 female Holstein newborn calves from a single farm were fed five different starter-pellet rations:
- 100% low-fat (3.5%), highly fermentable pellet (control)
- 90% of control pellet mixed with 10% of an extruded, high-fat pellet (7% total ration fat)
- 80% of the control pellet mixed with 20% of the high-fat, extruded pellet (11% total ration fat)
- 70% of the control pellet mixed with 30% of the high-fat, extruded pellet (14% total ration fat)
- A homogenous, high-fat, single pellet with 11% total fat
All starter rations were offered free-choice, along with fresh water and chopped barley straw. All calves received an identical liquid ration: 3 L twice a day of milk replacer powder containing 23.2% crude protein and 18.6% fat, reconstituted at 12.5% concentration, for the first week of life. Concentration then was increased to 15% until 49 days of age. For the last week, the formulation stayed the same, but feedings of 3L were administered only once a day, until complete weaning at 56 days of age.
The researchers found that the 90:10 (7% total fat) formulation appeared to be the optimal ration, because it produced increased total starter intake, energy intake and body weight gain until 84 days of age, compared to the control ration or the high-fat, single pellet.
An interesting finding was that the control group and 90:10 group consumed nearly the same amount of fermentable pellets, but the 90:10 group consumed additional energy because they also consumed the high-fat pellets. The researchers hypothesized that this finding may indicate calves have a ceiling for maximum starter intake dictated by the capacity of the rumen to ferment solid feed, and that inclusion of a non-fermentable, high-fat pellet may allow calves to consume more energy beyond their maximum capacity to consume fermentable feeds.