The production year of the cow herd is typically broken down into four physiological stages of production. Amy Radunz, from the University of Wisconnsin reviews these stages and offers some key management strategies to consider during these periods.
Stage 1: This is approximately 80-90 post-calving. The cow has four basic functions during this stage 1) lactation; 2) undergo uterine involution; 3) resume estrus; and 4) conceive
These is the time when the cow has her highest nutrient requirements because she is lactation and trying to re-breed. In northern climates, cows spend most of this time on pasture. This is to match the high nutrient content of the pastures during the spring, but it is important to make sure the cow is receiving enough nutrients during this period and at times pasture may not be enough.
Dietary energy and protein intake as well as cow body condition score will determine the length of time required for the animal to start cycling again (otherwise called postpartum anestrus period).
Postpartum anestrus is on average 60 days, but can be up to 100 days. The later a cows a cycles, the younger her next calf will be weaned and marketed the next year, this could mean 50-60 fewer pounds of calf in the fall. Another common problem is cows may show up open in the fall and then culled from the herd.
Stage 2: This is from about 80 to 205 days postpartum, or from the time of breeding to weaning. The three basic functions of the cow during this period are 1) lactation; 2) maintain pregnancy; and 3) gain weight and body condition lost during previous winter.
Commonly this period is during the summer and cows are grazing pasture and try to maximize use of animal harvested forage. ”It is always cheaper to have an animal harvest its own feed”. If pasture becomes limited at the end of this period several strategies can be implemented in order to provide enough nutrition to both the cow and her calf. Three common solutions are 1)supplement cows with hay and/or concentrates; 2) early wean the calves; and 3) creep feed the calves.
Stage 3: This is approximately from day 206 to 315 days postpartum or from the time calves are weaned until the 3rd trimester of gestation. The cow has only 2 basic functions at this stage are 1) maintain herself and 2) maintain her pregnancy.
This is what can be considered the make or break period in the production year and when the cow’s energy requirements are her lowest. Again during this period, it is important to maximize the use of cow harvested forage. This can be done by extending the grazing season through stockpiled forages, cover crops, or crop residues. This is also the time to feed the poorest quality harvested forage. However, if you have cow in poor body condition, this is a cheap time to add the weight lost during the past stages very economically.
Stage 4: From day 316 to 365 postpartum or the last third of gestation. During this stage the cow has 3 functions: 1) prepare for parturition; 2) prepare for lactation and 3) provide nourishment to allow for the majority of fetal growth to occur during this stage. The fetus grows about 0.9 lbs/day during the last trimester.
If cows are not provided enough nutrition during this stage this can cause several problems such as:
Reduced birth weight and thus survival is reduced
Reduced immune function of calf primarily due to inadequate colostrum production by the cow
Increased postpartum anestrus in Stage 1
Reduced conception rates in Stage 1
Reduced milk production thus reduced calf weaning weight
Low critical temperature is the temperature at which the cows starts to use energy to stay warm. It ranges from 5 to 49 degree F. Temperatures below 20-40 degree F can increase feed intake by 3-8% and below 0 can increase feed intake by 25%. The goal should be for cows to calve at a body condition score of 5 to 6 and this is highly correlated to reducing the risk of the problems outlined above.
All of these stages are important to the productivity and profitability of the cow herd. Therefore making sure nutrient needs are met but necessarily exceeded at each stage is important to achieve this aim.