Grassland Evaluation Contest Study Guide	Fifth Edition: October 2005
Grassland Evaluation Contest Rules - Matching Livestock and Forage
When does this livestock herd have the highest forage quality requirement? Spring Summer Fall Winter Requirement high year round Livestock nutritional requirements change throughout the year as the animals go through different stages of production. Forage quality must be higher for growing animals than for mature animals. Growing animals, such as steers or heifers, need a constant supply of high quality feed through the season to maintain growth. Shortages in quality will sharply reduce gain and profit. As an animal matures its nutritional needs change. The forage quality and quantity needed by mature animals also changes with production stage through the year. A mature beef cow goes through four stages of production each year (Figure 3). Nutritional needs will be different for each of these stages. Stage One is post-calving and lasts 90 days. Since the cow has just had a calf, her nutritional needs are now the highest of the entire year. She is lactating at her highest level, she is undergoing uterine involution, and she must cycle and re-breed within 90 days of calving to stay on a 12-month calving schedule in the herd. Lack of nutrition during this period results in lower milk production and failure to re-breed on time. A cow must re-breed in time to have a calf every 365 days. Failure to do this results in an unprofitable operation due to added costs of maintaining open, unbred cows. In Stage Two the cow is pregnant and lactating. This stage usually lasts 115 days. Nutritional needs will be dropping slightly during this period. The cow is in the early stages of pregnancy while still nursing her calf. She should be gaining some weight now. Stage Three is mid-gestation and lasts about 100 days. The cow has just weaned her calf and she is dry. Her nutritional needs are at the lowest point of the entire year since she only has to maintain herself and the developing fetus. She can get by on much lower quality pasture now than in Stage One. Stage Four is pre-calving. This stage lasts about 60 days and is the second most important period nutritionally during the year. Seventy to 80 percent of fetal development is occurring. The cow is gaining weight and preparing for lactation. Inadequate nutrition during stage four will often cause weak calves and poor re-breeding success during stage one. Cows need to be in good body condition now. She needs good quality pasture or hay to make sure both herself and calf will be strong and healthy. First or second calf heifers need higher quality forage than mature cows during all four of these stages since their bodies are still growing plus they are producing a calf. This makes it very important to feed these animals separately from the mature animals to ensure proper development. Mature bulls also need good quality feed during the breeding season but can get by on lower quality forages other times of the year. A cow herd has its highest forage quality requirement during stage one, which is during calving and rebreeding. This stage usually occurs in spring and fall in Missouri. Herds that have not set calving season or those that calve year-round need high forage quality year-round to support the cows calving at any given time. Year-round calving is not recommended. Calving seasons of 90 days or less are recommended to optimize forage production, breeding, and marketing. Source: 1984 NRC requirements for beef cattle Figure 3. Seasonal total digestible nutrient (TDN) requirement for a spring-calving 1,100 lb. Beef cow with average milk production Return to Grassland Evaluation Contest Study Guide