Body Condition Scoring Beef Cows
Late gestation and early lactation are critical periods in the cow production year. Nutrition during these periods impacts calf health, cow milk production and cow reproductive success. Cows derive most of their nutrients from their diet; however, body energy reserves are another important source of energy for cows. In addition, the cow has developed the ability to shut down non-essential processes such as reproduction when nutrients are limiting. An important part of this regulatory system is body energy reserves.
In this session, we will focus on:
1) how to body condition score cows
2) the impact of body condition scores are reproduction
Body Condition Scoring
Body energy reserves can be assessed by a visual appraisal system known as body condition scores (BCS). BCS gives a relative score to each cow for her level of body reserves in the form of muscle and fat. The system is on a scale of 1 - 9 with 1 being extremely thin and 9 being obese (see box below).
Body condition scores of 5, 6 or 7 are desirable. However, it is not unusual for good milking cows to be a BCS 4 at weaning. In addition, it is often un-economical for producers to try to maintain cows in BCS 6 or higher during mid to late lactation. In other words, it's all right for a cow to lose some weight when shes nursing a calf. But we need to get her back in shape by the time she calves again.
|Outline of spine visible||yes||yes||yes||slight||no||no||no||no||no|
|Outline of ribs visible||all||all||all||3-5||1-2||0||0||0||0|
|Fat in brisket and flanks||no||no||no||no||no||some||full||full||extreme|
|Outline of hip & pin bones visible||yes||yes||yes||yes||yes||yes||slight||no||no|
|Fat udder & patchy fat around tail head||no||no||no||no||no||no||slight||yes||extreme|
When to Body Condition Score?
Cows should be body condition scored at least four times per year.
90 days before calving
Beginning of the breeding season
These are critical times in the production year when decisions can be made on nutritional management. In most cases, cows will need to be divided into three groups cows in good condition, thin cows and young (<3 yrs old) cows.
Why is Body Condition Important?
Energy reserves in the form of fat and muscle (a.k.a. body condition) are extremely important for reproductive success. Several studies found that body condition score (BCS) at calving and BCS at the beginning of the breeding season were the most important indicators of reproductive performance (Perry et al., 1991; Spitzer et al., 1995). Body condition score at calving has the greatest effect on pregnancy rate during a controlled breeding season (Lalman et al., 1997).
Impact of Body Condition Score at Calving
Cows in body condition score BCS 5 (1 = emaciated to 9 = obese; Herd and Sprott, 1986) or better at calving have fewer days to first estrus and increased pregnancy rates (Rasby et al., 1981, Wettemann et al., 1981). Cows calving in BCS less than or equal to 4 had a 9 % to 29 % lower pregnancy rate compared to cows calving at BCS greater than or equal to 5 (Makarechain and Arthur, 1990; Selk et al., 1988). Based on data from the literature, hypothetical pregnancy rates for cows of various body condition scores are illustrated in figure 1. Research from Oklahoma indicates that changes in BCS between 4 and 6 have a greater impact on pregnancy rate than changes in BCS above 6 or below 4 (Selk et al., 1988). In other words, little improvement in pregnancy rates is seen when cows calve in BCS above 6 while pregnancy rate does not get much worse below BCS 4.
In addition to the overall decrease in pregnancy rates, cows calving at BCS less than or equal to 4 that conceive become pregnant later in the breeding season (Table 1). As a result, these cows calve later in the calving season the next year. Late calving cows are more likely to fail to conceive during a controlled breeding season. Calves born late in the calving season will be lighter at weaning than calves born early in the calving season. At weaning, calves will be approximately 17 kg (35 lbs) lighter for every 21-day delay in calving (Lesmeister et al., 1973).
Table 1. Effect of Body Condition Score at Calving on Cumulative Pregnancy Rates
|Day of the Breeding Season|
|BCS||20 d||40 d||60 d|
|Mature Cows (Richards et al., 1986)||Cumulative % Pregnant|
|less than or equal to 4||41||67||84|
|greater than or equal to5||51||79||91|
|First Calf heifers (Spitzer et al., 1995)||Cumulative % Pregnant|
First calf heifers are even more sensitive to the effects of BCS at calving on pregnancy rates. Dramatic decreases of 40 % to 50 % (Figure 2) occur as heifers drop from BCS 6 to BCS 4 (De Rouen et al., 1994; Spitzer et al., 1995). In contrast to mature cows, heifers exhibit a significant decrease of approximately 16 % in pregnancy rate between BCS 6 and BCS 5. Therefore, the optimum BCS at calving is 6 or 7 in heifers.
Limited data indicates that cows that calve at BCS greater than or equal to 7 and heifers that calve in BCS greater than or equal to 8 may have impaired reproduction during the breeding season (Richards et al., 1986; Houghton et al., 1990). One should be cautious in drawing any conclusions about fat cows, as the numbers of cows with BCS greater than or equal to 7 in these studies were limited. In addition, it is not always clear if cows were in high BCS due to nutritional manipulation or physiological factors. Efforts should be made to keep cows in the BCS 5-7 range from an economic standpoint as well as a possible reproductive effect.
Influence of Body Condition Score Changes from Calving to Breeding
Although body condition score at calving has the greatest impact on cow reproduction, changes in body weight and body condition score postpartum will also affect reproductive performance. Change in body condition score postpartum dramatically affect cows that calve at BCS less than or equal to 4. Low BCS cows that continue to lose weight and BCS after calving are unlikely to become pregnant during the breeding season. Thin cows that continue to lose BCS have a longer interval from calving to first heat (postpartum interval). This means a low percentage of these cows (0-40%) are cycling by the start of the breeding season (Houghton et al., 1990; Perry et al., 1991; Spitzer et al., 1995). Often it may take over 80 to100 days until these cows begin cycling. As a result of delayed cyclicity, thin cows losing BCS postpartum have low pregnancy rates, which are often 30 to 50 % lower than their well-fed counter parts.
Cows that calve in BCS greater than or equal to 5 are less sensitive to the effects of postpartum nutrition, but reproductive ability of cows losing weight after calving may be compromised. Interval from calving to heat is lengthened and pregnancy rate decreased in fleshy cows that lose weight postpartum. For example, researchers in Oklahoma reported a increase of 22 days in postpartum interval and a reduction in pregnancy rate of 14 % in cows that calved at BCS 5.4 but lost 1 BCS before the start of the breeding season (Cantrell et al., 1981).
Producers often hope that feeding thin cows to increase BCS and body weight after calving will solve their reproductive problems. Unfortunately, once a cow has calved her metabolism has shifted to support milk production. Therefore, only a portion of the additional energy fed to postpartum cows is available to combat the effects of low BCS. Cows that calve at BCS less than or equal to 4 and are fed high energy diets postpartum usually have a 10 to 20 % reduction in cyclicity compared to moderate flesh cows that maintain their weight (Perry et al., 1991). A reduction in the percentage of cows cycling diminishes the chances high pregnancy rates. Occasionally, these refed cows have conception rates equal to cows maintained in better body condition. (Richards et al., 1986; Houghton et al., 1990).
First calf heifers are less responsive to attempts to feed them to gain weight after calving. First, these primiparous cows have a longer postpartum interval and are more sensitive to the negative effects of poor body condition on reproduction. Because they are growing in addition to lactating, enhancing dietary energy intake does not readily enhance reproductive performance. Most studies indicate that thin heifers that are refed during early lactation have lower pregnancy rates at the end of the breeding season compared to heifers that calve at BCS greater than or equal to 5 and maintain their body weight (Spitzer et al., 1995; Lalman et al., 1997). Distribution of conception is also effected, as thin-refed heifers tend to breed later in the breeding season.
Modulating Body Condition
Since BCS of 5-7 is the optimum range for reproductive performance, keep cows in BCS 5 or better has been the dogma carried across the industry. In practice, cattle are often below BCS 5 at weaning, but good managers usually have them back to adequate BCS by 60 to 90 days before the calving season. The question is whether it is biologically and economically efficient to maintain cows in optimum BCS year-round.
Changes in environmental conditions and availability of forage often make achieving an optimum BCS by 60 to 90 days before calving difficult. A mild winter may result in most cows being BCS 7 or greater whereas a harsh winter may result in cows calving at BCS < 5. Only a few studies have looked at the effects of making short-term changes in BCS immediately before or after calving.
In a multi-state study, DeRoun and co-workers found that it did not matter if first-calf heifers lost weight or gained weight in the last 90 days before calving as long as they achieved a BCS of 6 by calving time. If heifers were BCS 6, then they had a high probability of conceiving during a controlled breeding season. Several studies indicate that cows that gain a BCS during the last trimester have improved pregnancy rates over those that maintain their body condition. Therefore, it may be economically and biologically advantageous to keep heifers at a BCS 5 for most of gestation and move them to BCS 6 during the last trimester.
Feeding Cows for Optimum Performance
Now, that we have discussed how and why to body condition score cows. Lets talk about using that information to plan a feeding program. If cows are in BCS 5 or 6 and heifers are in BCS 6 or 7, then the nutrition program is on target. However, if animals are thin then changes need to be made immediately. Remember, it is important for cows to be in the proper body condition BEFORE the calving or breeding season.
We can use the average BCS for the herd and the number of days until the calving or breeding season to decide how much to feed them. For example, cows in Bobs herd are BCS 4 45 days before the calving season. Those cows need to gain 1 BCS (40 to 85 lbs) in 45 days, so we need to choose a diet that will increase the body condition rapidly.
Feeding Strategies For Cows In Late Gestation
Supplement Energy First. Energy is usually the most limiting nutrient. Corn, barley and other grains are good sources of energy. These energy products will also reduce the amount of hay needed by cattle. When grains are fed at higher than 0.5% of BW forage intake is reduced. For example, a 1200 lb cow fed over 6 lbs of grain will reduce the amount of hay she will eat. This can be a good thing if we want to limit feed hay.
Grains can be fed at up to 50% of the diet without causing digestive upsets. Higher fiber feeds like corn gluten and soy hulls can be fed at much higher rates without worrying about cattle getting sick.
Some example diets for dry beef cows are shown in Tables 2 & 3. All diets are designed for cows that will weigh 1250 lbs. at BCS 5. The diets to gain weight are designed for cows that are BCS 3 and weigh 1050 lbs. now, but should weigh 1250 lbs. These diets are good examples, but feedstuffs on individual farms will vary. For accurate ration formulation, producers should have a nutrient analysis of their feeds, and consult your county extension agent or nutritionist to help design a ration.
Table 2. Diets to help dry cows gain weight
(lbs. per cow per day as fed basis)
|Ingredient||Diet 1||Diet 2||Diet 3|
|Corn Gluten Feed||0||7.0||16.0|
|Days to gain 1 condition score||46||57||27|
|Cost per cow per day||$1.00||$0.89||$1.04|
Table 3. Diets to help dry cows maintain weight
|Diet Composition (lbs. per cow per day)|
|Ingredient||Diet 1||Diet 2||Diet 3||Diet 4|
|Corn Gluten Feed||0||7.0||0||8.0|
Feeding Strategies Between Calving and Breeding
The primary nutrient that needs supplementation during this period is energy. Protein may also need to be supplemented, but it should be secondary to energy. The first thing you need to do is test your feeds especially hays and silage for nutrient content. Then compare these tests to the nutritional needs of your cows. Your animal science extension agent or nutritionist can help you with comparing the test results to the needs of your animal.
The source of energy can also be important. Grains such as corn or barley are good sources of energy, but they cause cattle to eat less forage due to a shift in the rumen microbes. If your hay is in short supply this decrease in forage consumption can be a good thing. However, you need to remember that once you supply more than 1/2% of body weight in grain, forage consumption decreases so you need to compensate by feeding a little more grain. Try not to feed more than 1 % of body weight in grain.
Highly digestible fiber feeds like soy hulls or corn gluten will increase the energy level of the diet without decreasing forage intake. This is an advantage because then feed intake is maximized which is important in getting weight on thin cows. These feeds usually have about 85 to 90 % as much energy as corn, so you will need to feed more pounds. Remember energy supplements need to be fed daily.
You should decide from the feed tests if you need to supplement protein. DO NOT over supplement protein. When an animal is fed too much protein it must rid its body of excess protein in the form of ammonia. Excreting ammonia is a process that takes energy. This is why the high protein diets cause you to lose weight if you dont eat a lot of carbohydrates (energy) while on the diet. So if you over feed protein, you will cause cows to lose weight or use the energy you are feeding them to get rid of ammonia rather than gain weight.
The best protein supplements are soy bean or cottonseed meal, corn gluten, and brewers grains. A reasonably priced mixed feed from the local feed mill is also good. Lick tanks and tubs are expensive sources of proteins, but they are an even more expensive source of energy. Generally, you should avoid lick tanks unless you are feeding corn silage or grazing corn stalks. Protein supplements can be fed every other or every third day. Just double or triple the amount of protein supplement you would normally feed. Remember this only works if you would only be feeding a small amount of protein supplement daily.
Table 4. Lactating cow diets
|Diet Ingredients||Meets or exceeds needs||Increase or loss of body condition in good weather|
|17.5 lb hay + 14.5 lbs of soy hulls or barley||Yes||+1 BCS in 110 d|
|16.5 lbs hay + 13.5 lbs corn + 2.2 lbs soybean meal||yes||+1 BCS in 60 d|
|16.5 lb fair hay + 14.5 lb dry corn gluten||Yes||+1 BCS in 180 d|
|8.8 lb hay + 22 lb dry corn gluten||Yes||+1 BCS in 60 d, very high energy diet needs to be fed carefully|
|8.8 lb hay + 95.2 lbs wet brewers grain||Yes||+1 BCS in 175 d; cows may not be able to eat that much brewers grain|
|36 lbs hay||NO||-1 BCS in 90 days|
Body condition scoring your cows is an essential management practice. You should body condition score your cows within the next 3 days if you have not body condition scored them in the last month. The severe winter and low feed supply has many cows in less than optimal body condition. If your cows are thin or your feed supply is short, get with your county agent or nutritionist right away to plan your feeding program. Open cows and weak calves are a costly way to learn a lesson in nutrition.
By John B. Hall, Ph.D.
Extension Beef Cattle Specialist
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