Have your calves been starving this winter?

Why do calves struggle to grow and survive in the winter?  Much of the answer comes from the fact that calves have a lot of surface area relative to their mass.  This means that calves need a lot of energy to keep warm due to the amount of body heat they can lose.  An excellent tool to predict performance of calves in different temperature scenarios exists in the 2001 Nutrient Requirements of Dairy Cattle (NRC, 7^th edition, 2001).  Simulations of calf performance can be made using diets with various levels of nutrition fed at various temperatures.  A calf's energy requirement increases as ambient temperature decreases.

Table 1 shows a comparison of three milk replacer feeding programs for a 100 pound calf one week of age that is not consuming any starter.  In other words, the baby calf relies on milk replacer for all nutrients.  The three milk replacer feeding programs are a 20% protein, 20% fat (20/20) all milk, calf milk replacer fed at 1.0 pounds/day (conventional) or 1.25 pounds/day (increased gain).  The third program uses a high protein (28%) milk replacer fed at 2.5 pounds/day using an intensified calf-feeding program. Using the NRC program, daily gains on calves were predicted for each program at 0, 20, 40, and 60° F.

The table shows that at an average temperature of 60° F, the calves gained weight on all programs, although the calves fed the higher protein milk replacer gain 6 times as much weight as the calves on the conventional feeding program.  When average temperatures drop to 40° F, calves fed a conventional program do not have enough nutrients to gain weight and the gain on the increased gain program drops by two thirds while the calves fed the intensified program continued to gain, but at a slightly slower rate.  As average temperatures drop to 0° F and 20° F, calves fed the 20/20 milk replacer on either the conventional or increased gain program either stop gaining weight or lose weight.  Only the calves on the intensified feeding program continue to gain weight, even at colder temperatures.  In extreme cold temperatures where calves are kept in cold housing, traditional milk replacer programs do not provide enough nutrients to maintain a healthy calf.  The calf will lose weight, the immunity may be compromised and some calves may die of starvation if they do not increase their starter consumption dramatically.  Many calves are not able to increase their starter intake rapidly enough to compensate for the energy shortfall.  The result is that the calf may become weakened and ultimately dies of malnutrition or starvation.

 

Table 1.  Comparison of average daily gains for a 100 pound calf, one week of age, fed different amounts of milk replacer at different temperatures (Based on 2001 NRC predictions)
	Conventional	Increased Gain	Intensified Management
Milk replacer (protein/fat)	20/20	20/20	28/20
Pounds powder (#/d)	1.0	1.25	2.50
Average Temperature	Average Daily gain (#/day)
60° F	.39	.79	2.48
40° F	.01	.26	2.11
20° F	Weight loss	0	1.83
0° F	Weight loss	Weight loss	1.56

 

 

What are the options to prevent starvation of calves during cold stress?  Some producers will attempt to improve the energy status of calves during cold weather.  When average temperatures are 0° F, it will take .3 pounds of fat to prevent the calf from losing weight.  However, additional fat will result in up to .4 pounds of gain when temperatures average 20° F.    Another option is to feed an additional feeding of milk replacer.  Feeding 1.5 pounds/day (in 3 feedings/day) of 20/20 milk replacer at an average temperature of 0° F will maintain body weight and result in gains of  .30 pounds/day when temperatures average 20° F.   However, the best option for cold weather feeding is an intensified feeding program, as it will maintain the nutrients a calf needs to maintain body heat and continue to grow. 

 

Some producers will argue that an intensified feeding program is too expensive to implement.  Table 2 shows an economic comparison of the three scenarios presented in Table 1 at 40° F.  On a cost/day basis, the conventional program is the lowest cost at $.84/calf/day, with the higher feeding rate of the 20/20 milk replacer costing $1.05/calf/day and the intensified management program costing $2.70/calf/day.  Purely from a cost standpoint, the conventional program makes the most sense.  However, if you factor in calf performance and evaluate cost in terms of pounds of gain, the results reverse themselves.  With virtually no gain the conventional program costs $84/pound of gain, the increased gain program costs $4.04/pound of gain and the intensified feeding program costs $1.08/pound of gain.  Clearly, the returns are improved when the nutrition of baby calves is improved.  If your calves have not performed very well this winter, consider providing them with the nutrients they need to achieve acceptable gains. 

 

Table 2.  Economic comparison of average daily gains for a 100-pound calf, one week of age, fed different amounts of milk replacer at 40° F.
	Conventional	Increased Gain	Intensified Management
Milk replacer (protein/fat)	20/20	20/20	28/20
Pounds powder (#/d)	1.0	1.25	2.50
Average Daily gain (#/day)	.01	.26	2.11
Cost ($/bag)	42	42	54
Cost ($/pound)	.84	.84	1.08
Cost ($/day)	.84	1.05	2.70
Cost($/pound of gain)	84	4.04	1.08