Ranchers have flexible feed possibilities when developing heifers
Developing replacement heifers from weaning to breeding can offer some flexibility in feed resources. “The pathway we use to get there can be up to us,” Chandra Engel, a North Dakota State University cow-calf specialist, told producers. “Producers have a lot of different environmental conditions which makes for a lot of different options for feed, including cover crops and crop residues, that could help reduce the cost of developing heifers.”
When producers develop replacement heifers, their goal should be optimizing the number of heifers that have reached puberty and have started cycling by the start of the breeding season. “Reaching puberty is a function of age and weight, but it is also impacted by genetics,” she said. “Post-weaning management of nutrition and growth performance are important to reaching puberty by 13-15 months.”
EARLIER CAN MEAN LONGER
“The earlier the heifers breed during the breeding season, the earlier they will breed during each subsequent breeding season,” she said. Engel said she is asked all the time how much a heifer should weigh at breeding to ensure she has reached puberty. “It has been well-established that the recommendation is 60-65 percent of mature body weight, but some research from different states indicates some heifers will breed at 55 percent mature body weight,” she said.
Reaching 60-65 percent of mature body weight has proven effective across a wide range of biological types and environments, but it could require more higher quality feed resources which could cost more. On the other hand, aiming for a 55 percent target mature weight may help producers reduce development costs, but it could also limit the number of heifers that breed within the first 21 days of the breeding season. “Even if we hit our target and get them bred, we need to remember they are still growing, and they are not at mature weight. We will need to manage their nutrition even after we get them bred,” Engel said.
“No matter the breeding target, whether it is 55 percent or 65 percent, we still need to get them to 85 percent mature weight and a body condition score six by calving time to ensure they will stay in the system for a longer term,” she said.
TARGET BODY CONDITIONING SCORE
Body condition scoring measures the body’s energy reserves using a visual method of determining nutritional status. It is highly linked to reproduction. It can also be done without gathering cattle, running them through a chute or across a scale. “It is a good tool to access to evaluate how well your nutritional program is working,” she said. “You can do it in a pasture or walk across a pen.”
If enough space is available, Engel recommended grouping heifers by light and heavy to better target their nutritional needs. “It will prevent you from feeding to the average of the group. It could also save feed resources and prevent under or over-feeding,” she said. Over-conditioning heifers above a body condition score of seven has added nutrient and feed costs, and it can have detrimental effects on reproduction, mammary development and milk production. It also increases dystocia.
HOW TO HIT THE TARGET
Engel recommended that producers know what their heifers weigh at weaning, what their mature weight should be, and determine a target weight between 55-65 percent. Then they should calculate how much the heifers need to gain before breeding, and decide how they will reach the target weight. “There are several options — constant gain, slow-fast gain, fast-slow gain or a combination,” Engel said.
Then producers need to determine their heifer’s nutritional requirements. Protein, energy, vitamins and minerals, and water are the most important. The amount they need is impacted by age, stage of growth, and production.
Protein is usually identified as crude protein and is measured in pounds. Crude protein is used by the rumen microbes to provide the animal with maintenance, growth and production. “Heifers have a specific total pound requirement per day that they need to maintain body condition and the level of growth we expect them to have,” she said.
Producers are also encouraged to remember that crude protein requirements will increase as the heifers gain weight. “Calcium and phosphorus requirements will also increase as the heifer develops more bone,” Engel said.
Energy is measured as Total Digestible Nutrient (TDN) or Net Energy maintenance (NEm) or Net Energy growth (NEg). Heifers have a specific total pound of Mcal requirement each day. That requirement can be met with feed sources that contain fiber, starch and fat.
Developing heifers during cold weather can also impact nutritional needs. “Cold stress is affected by temperature, wind speed and hair coat. A basic rule of thumb is that energy requirements will increase 1 percent for every degree the temperature drops below that animal’s lower critical body temperature,” she said.
• Summer wet 60 degrees F
• Dry fall coat 45 degrees F
• Dry winter coat 32 degrees F
• Dry heavy winter coat 19 degrees F
As a final thought, Engel encouraged producers to get their feed tested, so their feeding program is more efficient. “Feedstuffs vary in protein and energy. Some will have high energy and protein, and others won’t,” she said. “Testing feedstuffs will help you balance their diet. But, the best diet is the one that matches your financial and feed resources to help you make your desired goals.” ❖
— Clark is a freelance livestock journalist from western Nebraska. She can be reached by email at firstname.lastname@example.org.