~ updated Aug 9, 2017.
Milk replacer feeding rates have received much attention over the past several years. Calves grow bigger in a shorter period of time mainly due to consumption of more milk or milk replacer. This changes the supporting role of calf starter feed in early growth. Starter quality and the milk replacer feeding program have a big impact on starter intake in pre-weaning calf growth.
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In general, we expect to see calf starter intake delayed as milk replacer intake increases. But that’s not a hard, fast rule. Table 1 shows feed consumption results for a research trial comparing two milk replacer formulas and feeding schedules. Calves on the 20-20 (20% protein, 20% fat) all milk protein formula received 16 oz of milk replacer powder in one gallon of water each day. Calves on the 25-15 formula received 24 oz of powder in one gallon of water each day. All calves received milk replacer twice-a-day and had access to free choice water and starter. All calves and were weaned at the end of Week 6.
Table 1.
By week 6, calves on the 20-20 treatment consumed 42 pounds of milk replacer powder and 49 pounds of calf starter feed for a total feed intake of 91 pounds. Calves on the 25-15 treatment consumed 63 pounds of milk replacer powder and also ate 49 pounds of starter. Total feed intake for these calves was 112 pounds by the end of week 6. During weeks 7 and 8, calves received only starter feed and free-choice water. Feed values in the table are As-fed and are cumulative from the beginning of the trial.
Despite different formulas and feed rates, calves on both treatments ate the same amount of starter by weaning. After weaning, calves on the 25-15 treatment consumed more starter than 20-20 calves. The following graph shows the energy intake from the different feed sources during the trial.
Energy provided by the two milk replacers are shown by the blue and red horizontal lines. Energy provided by the amount of starter each day is shown by the green line. For calves on the 20-20 program, energy from starter intakes surpassed energy from milk replacer at about 4 weeks. This transition point was a couple days later for calves on the 25-15 program. Now look at what happens when you change starter quality.
Effect of Calf Starter Quality
The treatment results described above are for calves that received Starter A, pictured below on the left. Two other treatment groups of 20-20 and 25-15 calves received Starter B instead of Starter A. Both starters were commercially available with similar nutrient analyses. Starter B is a drier feed, containing little molasses, more pellets, less grain and more small, broken particles (fines).
The Energy Intake graph below shows calf response to Starter B. The transition point where energy from starter intake surpassed that of milk replacer was delayed more than a week for 20-20 calves. This point was pushed back to weaning time for the 25-15 calves. By week 8, Starter B calves were eating 3 pounds per day less starter than calves on Starter A. Differences in starter quality resulted in Starter A calves being 18 to 20 pounds heavier than their counterparts on Starter B by the end of the trial.
Effect of Milk Replacer Program
Another reason for starter intake depression is the design of the milk replacer feeding program. Table 2 shows trial results comparing milk replacer and starter intakes of calves on a 25-15 program vs. calves on a 28-20 program. Calves on the 25-15 treatment received 1.5 pounds of milk replacer powder per day throughout the trial. Calves on the 28-20 calves trial received 1.88 pounds of powder per day during the first week. The feeding rate for 28-20 calves increased to 2.6 pounds per day during weeks 2 through 6, and dropped to 1.3 pounds per day during week 7. Calves received milk replacer twice daily and had access to free choice water and starter. Calves on the 25-15 treatment were weaned at the end of week 6, and 28-20 calves were weaned at the end of week 7.
Table 2.
By week 6, the 25-15 calves consumed 41 pounds less milk replacer powder and 25 pounds more starter than the 28-20 calves. That’s nearly double the starter intake. By the end of the trial, 25-15 calves consumed 50 pounds less milk replacer powder and 45 pounds more starter than the 28-20 calves. That’s one bag less milk replacer and one bag more starter. Although not reported in the table, the 28-20 calves were significantly heavier (p<0.05) at the end of weeks 2 and 3, were only 4 pounds heavier at the end of week 6, and were the same weight as the 25-15 calves by the end of week 8.
Gross Energy Intake
The graph below provides insight into what’s going on with the two treatments. The red line shows energy intake with the 25-15 program. The blue line shows energy intake for calves on the 28-20 program. Energy from starter intake of the 25-15 calves, the purple line, shows that starter became the major energy source for those calves just prior to the end of week 4. Energy from starter intake of the 28-20 calves didn’t cross that point until weaning at 7 weeks.
By week 4, the difference in total daily energy consumption between the two groups had narrowed substantially, and by week 6, daily energy intakes were virtually the same. During weeks 7 and 8, the 25-15 calves consumed more energy than 28-20 calves.
These intake and growth results show that 28-20 calves lag behind as they approach weaning, and strongly suggest that calves could benefit from modifications to this milk replacer feeding approach. These calves certainly can’t afford any intake lag due to issues with calf starter quality and composition. Increasing the number of milk feedings per day might be one way to help improve starter intake — perhaps for both groups, and adjustments to the 28-20 feeding rates or delaying weaning may help reduce the growth lag and need for these calves to catch up. With total feed costs about 60% higher with this 28-20 program, the only time you’d expect calf weights to be the same is on day 1.
