Everyone wants their cow-calf herd to make it through the winter in good condition and ready to calve and breed back. But do we understand what it takes to make that happen?
In this piece, Travis Mulliniks and TL Meyer describe what what good body condition is, how gestational changes affect nutrition needs, the stress periods that require extra attention, and how to make sure animals are getting the feed they need.
What Body Condition Do We Want?
On a scale of 1 to 9, a calving BCS of 5 to 6 is considered optimal at calving. Weather changes and forage availability can make achieving an optimum BCS 60 to 90 days before calving difficult. A mild winter may result in most cows being BCS 5 or greater, whereas a harsh winter may result in cows calving at BCS less than 5.
Measuring BCS in the winter can be deceiving due to gut fill of low-quality forage, winter hair coat, or environmental conditions. Thin cows with increased gut fill of low-quality forages can be mistaken as being in better condition than they truly are. Long winter hair coats can mask prominent ribs or the vertebrae, landmarks used in scoring body condition. After a winter storm, cows can also look thinner than they actually are with a shrunk appearance due to a lack of water and forage intake.
If you’re not familiar with Body Condition Scoring, here’s a review of the basics to get you started. We also provide pictures here. Click on the photo of the BCS you’re interested in to see more pictures you can use as guides.
Stress Periods Affect Nutrition Requirements and Body Condition
What is a stress period? It’s a time when an animal’s nutritional needs change because of changes in its physical condition or changes in the weather.
One “stress period” is late gestation. Moving from mid to late gestation increases a cow’s energy requirement 25% and her protein requirement 10%. Providing good nutrition to pregnant cattle during late gestation supports rapid fetal growth, and calf health and performance. Calves born from nutrient-restricted dams during late gestation have been shown to have reduced immunity. In addition, it prepares the cow for her greatest nutritional “stress period” of lactation, which can affect her subsequent reproductive performance. In addition, the nutritional management of the pregnant beef cow can affect her calf’s performance.
Cold winter weather is another stress period. When the effective temperature is below the animal’s lower critical temperature, the animal must increase heat production to maintain a constant body temperature. To produce more heat, the cow must either receive more energy from the feed ration or draw on her body stores. Seven days or more of cold, windy or wet weather will increase cow energy requirements 10 to 30%. If cows are not fed enough during cold stress periods, they can easily drop a body condition score (BCS) in 30 days or less.
If hay or forage quality is good, intake will increase; however, with low-quality forage, the increased intake and overall energy intake may not be enough to meet requirements. To maintain body condition, cows will need additional supplement during extreme weather.
Supplementing to Meet Our Goals
The last chance to economically increase BCS on a cow during late gestation is the last 90 days prior to calving. After that, it is difficult for a thin cow to gain condition immediately after calving because it requires large amounts of high quality feeds, due to her increased nutrient demand for lactation.
This leads us to supplementation options. When cows are thin or grazing low-quality forages, some producers want to increase energy intake with corn, but this can backfire in some circumstances. Feeding corn on a forage-based diet can reduce forage intake and digestibility because the increased levels of starch from the corn alter rumen microflora and ruminal fermentation. The level of protein in the diet determines how corn supplementation affects cow performance. If the cow’s protein requirement is not met, feeding corn alone may actually increase body weight loss during gestation compared with feeding corn + protein or protein alone, as shown in the Table 1.
Protein supplements improve cow nutritional status by increasing digestibility and intake of low-quality forages and/or increasing nutrient flow of protein from the rumen to the intestines. If cows are thin, both protein and energy supplementation is needed to increase BCS. With cows in good, acceptable BCS, protein supplementation on low-quality forages can maintain BCS or slightly increase BCS over winter. Thin cows (BCS ≤ 4) or young cows could be sorted and fed separately from the mature cowherd. This would allow for more strategic supplementation and decrease overall feed costs.
Typically, a cow must gain 75 to 100 lbs of body weight to increase 1 full BCS, but during late gestation that number increases to account for fetal growth and placental weight. Thus, it is important to distinguish body weight differences due to differences in BCS and body weight changes resulting (and required) by fetal growth.
At the end of the day, BCS is an insurance policy or risk management. It is easier to stay ahead while maintaining adequate BCS than letting cows slip and get behind. Getting behind during late gestation can decrease rebreeding performance of the cowherd and negatively influence calf performance.
What Can You Do With This?
Obtain a nutrient analysis of forage resources.
Here’s an On Pasture article to help with that.
Inventory forage resources by quality.
Once you know what you have, you can provide the quality and quantity you need through the winter. Do remember that forages continue to change in quality over the winter. So if you haven’t checked quality recently, you may need to do it again.
Sort cowherd into nutritional needs groups (thin cows and young cows).
Match forage resources with those nutritional needs groups. Determine supplemental needs and balance diets to minimize costs. Adjust supplemental energy for cold stress and/or for thin cows.
Use body condition score (BCS) as a guide and monitor throughout the winter.
Listen to a discussion of the content in this article on this episode of the BeefWatch podcast. You can subscribe to new episodes in iTunes or paste http://feeds.feedburner.com/unlbeefwatch into your podcast app.