How many of your calves will the abominable snowman eat this winter?
Say NO to "calf-sickles"! Thermal stress is one of the biggest challenges when raising calves during Minnesota winters. Industry and University experts have targeted low total caloric intake as the chief cause of poor performance and increased mortality rates in the winter. Caloric intake for a nursery calf is the sum of energy intake from milk or milk replacer and starter grain. Additionally, performance of calves fed accelerated milk replacer programs during winter might be diminished compared with other times of the year if energy (not protein) is the rate-limiting nutrient for growth.
Previous research in my laboratory at the University Minnesota demonstrated that calves fed an accelerated milk replacer program (26:18 @ 2.0 % of body weight (BW)) had higher average daily gain (ADG) than conventionally fed (20:20 @ 1.5% of BW) calves. Interestingly, calves fed the accelerated program did not meet predicted energy or protein allowable gain. We hypothesize that the combination of low starter intake and cold stress likely resulted in lower than predicted gain. Perhaps energy intake was limited resulting in use of protein for energy rather than for structural growth.
Research demonstrating effective feeding strategies for cold stressed nursery calves is lacking. This winter at the University of Minnesota Dairy Teaching and Research Unit on the St. Paul Campus, we will evaluate the use of supplemental fat for calves fed an accelerated milk replacer program. Our objectives are to determine if adding a commercially available fat to milk replacer at 0, 0.25 or 0.5 lb per day improves ADG in nursery calves fed milk replacer (28:15 at 1.8% of birth BW) during winter and secondly we aim to determine if fat supplementation affects starter intake and thus total energy intake in nursery calves during winter in Minnesota.
I used software (National Research Council, 2001) to predict energy available gain for the calves in our trial for this coming winter (Figure 1). Calculations are based on a 130-lb calf with an intake of 1.0 lb per day of starter. If the predictions hold true, the added fat will improve gains and ADG will not dip below 1.0 lb per day even in temperatures of -10°F. It will be interesting to see the effects of fat on starter intake.
Figure 1. Estimated energy allowable gain (lb per day) for calves fed whole milk or a 28:15 milk replacer at 2.0 lb of DM daily and supplemented with either 0, 0.25 lb or 0.50 lb per day of a commercial fat supplement containing 7% protein and 60% fat.
Cooler temperatures typically result in an increase in starter intake, but only if good quality palatable starter is within reach of the calf. I took a look at starter intake data from calves at the St. Paul Dairy early last winter by summarizing average starter intake above and below the median temperature based on age of the calf (Table 1). We feed a texturized starter that is refreshed daily in amounts to provide 5% refusals. Two key "take home" messages from this data are: 1) calves raised in colder conditions eat more starter, and 2) more importantly, they eat more starter earlier in life. It is important to feed starter to calves beginning within the first week of life and more importantly, calves must be able to reach the starter. Bucket opening height should be no greater than 20 to 24 inches from the ground.
Table 1. Starter intake of nursery calves by calf age and average environmental temperature at 7, 14, and 21 days of age (U of M, 2010).
|Calf age, days|
|Day 7||Day 14||Day 21|
|Environmental temperature||< 27 °F||> 27 °F||< 27 °F||> 27 °F||< 27 °F||> 27 °F|
|Starter intake, lb per day||0.08||0.04||0.24||0.20||0.50||0.46|
Fermentation of starter in the rumen likely acts as an internal heater for calves. In a 1400-lb lactating dairy cow, heat produced accounts for about 20% of total energy intake or around 32,000 British Thermal Units (BTUs) per day. If we take some liberty with this calculation, a 140-lb calf may produce around 10% of the heat of an adult cow or 3,200 BTUs per day. As a comparison, this conservative estimate is enough energy to run a 1-kilowatt electric heater for one hour.
Some other tips for cold weather calf feeding include:
- Adding up to 40% additional total volume of milk replacer per day in extremely cold conditions.
- When feeding powder at higher mixing rates, do not reconstitute milk replacer in excess of 15% total solids. Mother Nature intended milk to be 12.5% solids, so higher solids often equal greater health risks.
- Add at least 1.5 bales of straw to each hutch initially and add more straw frequently to provide insulation for calves. The Wisconsin nest scoring system is useful for determining when to add straw. Nesting score: 1 = Calf lies on top of bedding with legs exposed; 2 = Nestled slightly into bedding, but part of legs are visible; 3 = Nestled deeply into bedding so that legs are not visible.