Our recent mild and extended autumn (in November) might have given a false sense of security that somehow most post-weaned cows are in great body shape, and they will be able to carry this condition into calving time; no matter how they’re fed or managed. However, in the back of our minds, we know this isn’t true.
A sound pre-calving feeding program is a wise investment.
In the last 80 -90 days of gestation, all beef cows should have a rapidly growing calf inside them. We need to put them on a better plane of nutrition; not only maintain or achieve a Body Condition Score (BCS) of 2.5 -2.75 by calving, but also to gain a parallel weight of 150 -180 lbs. (the fetus, fetal membranes and placental fluids), which is lost on the day her calf is born. Additional feeding programs should be set up for thin mature cows (BCS < 2.0) and growing replacement heifers, so they can gain sufficient non-fetal weight until they calve. Ultimately, a successful calving season equals a cow in the right body condition that gives birth and ready to nurse a healthy and growing calf.
Here are five overwinter feeding tips that should be incorporated into the diets of your beef cows during last trimester of their gestation.
1. All ration balancing activities should center around optimizing “dry matter” and “as fed” intakes of a well-balanced diet. It regulates the total amount of nutrients entering the cows’ body and in many cases determines whether essential nutrients are going to be met. There is a host of factors that determine feed intake by gestating beef cows, ranging from body size to digestibility and palatable of the feed. A common 1,300 -1,400 lb. gestating beef cow is estimated to consume about two to 2.25 per cent of her body weight on a dry matter basis or about 25 -30 lbs. of dry-based feed. When moisture of the feed is taken into account, a bulky 50 -60 lbs. of feed can be consumed.
Consequently, these beef cow diets should be balanced upon a good forage foundation that either provides significant beef cow nutrition or if low quality forages are used; lacking nutrients can be easily supplemented with grain concentrates and protein supplements to meet overwintering nutrient requirements. High fibre forages such as barley straw and wet fermentable feeds such as cereal silages are acceptable, just as long as producers have the option of putting “as fed” limitations upon them. Because both types of these forages can easily dilute the important nutrients of the diet, they should never be formulated in such great amounts that make us challenge beef cows’ feed intake nor force us to rely on them for most of the cows’ nutrient requirements. This is particularly critical during the late-gestation period, when we wish to increase overall nutrient density of the cows rations.
2. Evaluate and increase the energy density of late gestation diets. Energy is the single largest nutrient requirement of the overwintered beef cow herd. The amount of dietary energy that each beef cow receives throughout the winter dictates whether a healthy body condition is going to be either maintained or improved by the calving season.
Most late-gestation cows of the herd with a decent BCS of 2.5 to 2.75 will require a revised late-gestation diet that should contain about 55 to 60 per cent TDN (total digestible nutrients) to maintain good body condition for the next few months. Thin beef cows of BCS of 2.0 or less and growing replacement heifers should be fed a similar diet, however its energy density should be increased by 25 per cent.
Furthermore, we might need to increase the energy content of all of these diets by an additional 25 -40 per cent as the weather turn bitterly cold. An old winter rule of thumb dictates to feed an extra lb. of grain for every -5C drop in temperature below -20C during the day. Therefore, one should be prepared to feed a few extra pounds of grain during the coldest winter weeks.
3. Protein like energy density is going to be at a premium in late-winter cow diets. It’s a nutrient, which is essential in the diet to meet the gestating cows’ metabolic requirements (including those of the fetus, and to make colostrum). In addition, dietary protein to provide their rumen bugs with adequate nitrogen to maximize forage fermentation and thus increase the digestibility of high fibre forages of the late-gestation cow diet.
The protein requirement of mature cows freed of spring calves in the fall starts off at very modest level of seven to nine per cent in the diet, but steady increases to about 10 to 11 per cent protein or about 20 to 25 per cent by 90 days before calving. This a good time to make sure that the diet, especially those containing straw or other low-protein forages are adequately supplemented with dietary protein. There are many available protein options such as feeding better protein forages, providing a couple of pounds of corn distillers’ grains (28 per cent protein) or setting out protein blocks and tubs.
4. It is a good idea to ensure that all pregnant cows are consuming a consistent three to four ounces of a commercial beef mineral, complimentary balanced to the rest of the gestation diet. University and extension studies have proven that late-gestation cow mineral and requirements increase as much as 25 to 50 per cent compared to the start of the winter.
Some beef producers make it a point to improve the mineral program of their cows during the last 60 to 90 days of gestation by switching them onto a premium cattle “breeder mineral.” Such breeder mineral formulas often contain elevated levels of essential trace minerals such as copper, zinc, manganese and selenium. A portion of these latter trace elements are usually provided in an organic or chelated form, which assures better absorption and better retention in pregnant beef cows as well as help improve the essential mineral status of their growing beef fetuses.
5. Make sure a good clean source of water is available at all times. Water is sometimes called, “the forgotten nutrient.” Many of us forget that gestating cattle need about nine to 12 gallons of water on a daily basis to meet this nutrient requirement.
If beef cows do not get enough water, not only do they not meet their physiological requirement for maintaining good body function, they can be placed under dire consequences, depending on the type of overwinter diet consumed. For example, cows that are overwintered on a straw-based diet are susceptible to deadly impaction, if there is not a source of available water located nearby. If snow is the cows’ source of water, make sure enough clean snow is pushed up to meet all the cows’ water requirements. As late-gestation progresses toward calving, the cows’ water requirements will only increase.
The following sample diets are a cost-comparison between a typical early-to mid-gestation diet fed for the first half of the winter and a late-gestation diet fed for the later half or 90 days before calving:
Mid-gestation diet: 18 lbs. barley straw @ $50/mt, 10 lbs. 14 per cent cow screening pellets @ $160/ mt and 3 oz. of commercial 2:1 mineral with salt @ 11c/head/d. = $1.24/head/day.
Late-gestation diet: 10 lbs. barley [email protected]$50/mt, 10 lbs. grass [email protected]$90/mt, 12 lbs. of 14 per cent cow screening [email protected]$160/mt and 3 oz. of a commercial breeder [email protected]/head/d. = $1.64/head/ day.
Despite a significant 33 per cent increase in feed costs, this extra $0.40 spent on each pregnant cow is well spent. It also represents one of many possible feeding scenarios for late-gestation cows.
Peter Vitti is an independent livestock nutritionist and consultant based in Winnipeg. To reach him call 204-254-7497 or by email at [email protected]