Calves that are 450 pounds or lighter going into winter may have more challenges than calves that are 650 pounds and heavier. To maintain growth rates on these light weight animals, paying attention to details makes all the difference.
Respiration rate is one indicator temperature stress. A cold stressed animal will breathe 20 times a minute to minimize heat loss from the lungs. Blood flow is also constricted to the outer parts of the body to keep core body temperatures warmer. The occurrence of frozen ears and tails increase.
With a large body surface area relative to body weight, the lower critical temperature for the light weight calf is much higher than for the heavier animal. A calf between 1 month of age and weaning has a lower critical temperature of -2 degrees Celsius. (https://extension.psu.edu/calf-management-tips-for-cold-weather). This is because of the high heat loss compared to the amount of heat the animal can generate from digesting feed compared to heavier calves.
Feed quality is important. To generate more heat, cattle increase feed passage rates so they can eat more each day. Rations that include high quality hay or silage and grain tend to be easier to digest and produce more energy (heat). Inclusion of grain in the ration is essential to increase energy density. Providing a creep feed with 16 to 18% protein helps improve feed intake and heat generation. Protein requirements for the 450 pound calf is roughly 14 to 15% on a dry matter (DM) basis. This is to optimize rumen microbe populations so that feed is digested quickly and efficiently. Low protein rations reduce feed intake because of slow digestion rates. (https://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex9146/$file/420_52-4.pdf)
Preventing heat loss by wind cooling can be done by providing shelters or hutches and along with wind fences. Keeping the area dry by bedding with straw or shavings is recommended. If the bedding and haircoat is wet up to 25% of the heat generated by the animal can be lost.
Management is key to keep the light weight animals healthy, warm, and productive.
For more information on feeding light weight calves, Barry can be reached at 403-741-6032 or firstname.lastname@example.org.