At Winter’s Gate
Feeding Strategies for Females in Late Gestation Through Winter
November – the last month of autumn. By now, many spring-calving herds have weaned their 2021 calf crop and may be in a bit of a grace period where females are drying up, grazing the last bit of pasture and preparing to be moved to corn stalks. According to Martha Gellhorn, American novelist, journalist and war correspondent, in November, you begin to get an idea how long the winter will be.
When planning winter feeding strategies, the main goal is to meet the increasing nutritional demands of females during late gestation. Evaluating body condition, forage testing, calculating forage intake and knowing when to add supplements are four methods to ensure appropriate nutritional needs are being met during times of gestational and environmental changes.
Strategy 1: Evaluate and Sort Based on BCS
Body condition score (BCS) is a term used to describe the relative “fatness” of a female based on a 9-point scale (1 to 3 thin; 4 to 6 moderate; and 7 to 9 fleshy). Kacie McCarthy, Ph.D., University of Nebraska beef cow-calf specialist, uses a three-step system to evaluate females for BCS:
Step 1: Look at the last two ribs; if both are easily visible, BCS is less than 5. If not, BCS is more than 5.
Step 2: Look at the spine; if individual vertebrae are visible, BCS is less than 3.
Step 3: Look at the shape from hooks to pins; a shallow “U” shape indicates a BCS of 6, while a very strong “V” shape indicates a BCS of 2.
Ideally, mature March-calving cows should calve with a BCS of 5, while it is recommended that first-calf heifers calve with a BCS of 6.
Evaluating body condition during late gestation is important because it’s easier to put weight on during gestation than lactation. When appropriate, thin and/or young females should be sorted into their own management group post-weaning or at pregnancy checking. Depending on the type of cattle, it could take anywhere from 75 to 120 pounds of gain to increase one BCS. Forage testing is the first step in nutritional management for maintenance or gain.
Strategy 2: Test Forage
Setting about the task of putting the pounds on those thin females is no small feat, but with some information in hand, it can be done and done well. While forages can supply much of the nutrient requirements needed for a female, sometimes quality falls short, especially if the forage has been in storage or exposed to the elements for a long time.
“As nutrient requirements increase, the quantity and quality of forage needed by the cow also increases,” McCarthy points out.
She recommends testing forages prior to winter so you know what you’re working with.
According to https://beef.unl.edu/learning/feedanalysis.shtml, “Once a feed sample has been collected properly, it can be analyzed for nutrients. Analyzing cattle feeds for moisture, protein and energy is recommended.”
Like nutrient requirements for beef cattle, forage test results are typically reported on a dry matter (DM) basis. “After formulation on a dry-matter basis, values can be converted to an as-is basis (using the moisture content of the feed) to determine the actual amount of feed (as-is) that should be fed,” the webpage continues. Once samples have been tested, the next step is to calculate forage intake.
Strategy 3: Calculate Forage Intake
Generally, non-lactating females consume 2.5 to 3 percent of their body weight per day based on a 100 percent DM basis. For example, a 1,200-pound female in late gestation could consume 30 pounds of forage per day on a DM basis (1,200 × .025). Forages, however, contain moisture as well as DM. A forage sample could test 92 percent DM and 8 percent moisture. In this case, the female will consume about 32.6 pounds of forage per day on an “as-fed” basis (30 ÷ 0.92).
Rations are developed based on animal requirements and stage of production cycle, and should pay particular attention to total digestible nutrients (TDN) and crude protein (CP). TDN is a measure that indicates the feedstuffs’ energy content. CP is essential for increasing digestibility and forage intake as well as maintaining or increasing body weight. According to McCarthy, general energy and protein rules of thumb are:
Mid-Gestation: 55 percent TDN, 7 percent CP
Late-Gestation: 60 percent TDN, 9 percent CP
After Calving: 65 percent TDN, 11 to 12 percent CP
McCarthy reminds producers that periods of stress, like cold weather, affect a female’s lower critical temperature (LCT) – the temperature at which she starts using reserved energy to maintain body temperature. TDN needs to increase 1 pound for every 5° F the temperature falls below 0° F; simultaneously TDN requirements increase 1 pound for every degree the temperature falls below a female’s LCT.
Producers should be prepared to be hit with a double whammy of cold stress and the large nutritional demands of late gestation as deep winter sets in. Moving from mid- to late-gestation increases a female’s energy requirements by 25 percent and her protein requirements by 10 percent, McCarthy reports, as 75 percent of ruminant fetal growth occurs in the final two months of gestation. That preparation often comes in the form of supplements.
Strategy 4: Supplement Smartly
At a minimum, 7 percent CP in cattle diets is needed to maintain microbial function and digestion in the rumen. In an extremely close working relationship, daily energy intake – the primary factor limiting cattle performance on forage diets – declines rapidly as forage CP falls below 7 percent. If this situation arises, a protein supplement readily available in your area should be fed. Oftentimes, protein supplements like tubs, cake/cubes or distillers can be offered to cattle one, three or seven days a week, and will correct a protein deficiency, resulting in boosted energy intake, McCarthy reports.
On the other hand, supplementing energy should be a daily occurrence to decrease the chance of rapid change in the rumen environment or shifts in fermentation patterns that could reduce forage utilization or cause acidosis or digestive upset, McCarthy explains. When supplementing energy, feedstuffs like corn silage or range cubes are recommended. Factors like transportation, costs and variation of intake among individual females should be considered when choosing supplements.
While supplementing protein and energy may take place on a case-by-case basis, offering cattle a complete mineral supplement is recommended daily, year-round. A good trace mineral may help with the utilization of protein and energy, and can improve the performance, health and fertility of cattle.
When standing at winter’s gate, producers are encouraged to evaluate and sort their herd based on BCS, test their forage supply, calculate forage intake for females in late gestation and utilize supplements as needed as part of their winter feeding strategy.
Written By: Micky Burch, Nebraska Cattleman Senior Writer
Source: Nebraska Cattleman November 2021 Issue