ONA REPORT

published in

THE FLORIDA CATTLEMAN AND LIVESTOCK JOURNAL


September 2015

Planning Winter Supplementation for the Cow Herd


For questions or comments regarding this publication contact: Dr. Pillip Lancaster, University of Florida, IFAS


It is time to plan for winter supplement needs. There are three important components to designing a winter supplementation program: cow nutrient requirements, forage nutritive value, and supplemental feed type. In South Florida with cows calving in the fall, cow nutrient requirements during winter months are determined by cow body weight and milk production, with an estimate of each being necessary to calculate nutrient requirements. The best method to determine cow body weight is to weigh the cows when they come through the chute for routine husbandry practices. But an estimate of body weight can also be obtained from the sale ticket of cull cows. Any estimate of body weight should be accompanied by an estimate of body condition score so that body weight can be adjusted to body condition score 5. Maintenance requirements of the cow are based on body condition score 5. To adjust cow body weight for body condition score, subtract 75 lb from the body weight for each body condition score above 5 and add 75 lb to the body weight for each body condition score below 5.

Determining an estimate of milk production is difficult in beef cows, because milking beef cows is not feasible for ranchers. The average milk production for the breed can be used, but that is only accurate for the average purebred cow; additionally, most commercial cows are crossbred. Thus, a Peak Milk Calculator has been developed in excel to help ranchers estimate the peak milk production of cows. The Peak Milk Calculator can be found at the Range Cattle Research and Education Center website (https://rcrec-ona.ifas.ufl.edu/resources). The calculator requires an estimate of forage total digestible nutrients (TDN; a measure of energy content) for each month from birth to weaning, calf birth weight and weaning weight, anticipated calf slaughter weight at USDA Choice Quality Grade, and calf day of age at weaning. Once an estimate of cow body weight and peak milk production is known, cow energy and protein requirements can be found in Basic Nutrient Requirements of Beef Cows (EDIS AN190; https://edis.ifas.ufl.ed).

The next part of the equation is forage nutritive value, which is the variable a rancher has greatest control over to impact supplemental feed needs from year to year. The effect of winter forage nutritive value on supplemental feed needs is shown in Table 1. Nutritive value of winter forage negatively impacts supplemental feed needs in two ways. First, the forage of lower nutritive value does not provide as much protein or TDN in each pound of forage, and second, the cow cannot eat as much of a forage with lower nutritive value. Both of these factors combine to increase the supplemental feed needs for the cow when fed forage of low nutritive value. In the example, the forage of low nutritive value requires 8.5 lb/d of a 16% protein molasses product to meet the TDN and protein requirements of the cow, whereas, the forage of high nutritive value requires only 3 lb/d of the same molasses product.

Hopefully, planning for greater nutritive value of winter hay began last spring. Spring is the time of year that forages have the greatest nutritive value, and the climate provides the best chance of harvesting high quality hay. Harvesting forage for hay more frequently in the spring will increase nutritive value of hay, because it is less mature at the time of harvest. Harvesting more frequently will reduce the forage yield per cutting, but the increased number of cuttings will result in the same forage yield as a single cutting in early summer. In this manner a rancher will have the same amount of stored hay for the winter, but the hay will be of greater nutritive value.

Stock-piling forage such as limpograss in the fall is another method to increase nutritive value of winter forage. Limpograss maintains good TDN value even late into the fall and winter as it matures, however, mature limpograss has low protein content, usually between 3 and 5% of dry matter. With the good TDN value of stockpiled limpograss, supplementation of cows consists primarily of protein. Supplementing protein is less expensive than supplementing energy due to the lower amount of feed required. The cow may require only 3 to 4 lb of a high protein feed to meet protein requirements when grazing limpograss, but may require 7 to 8 lb of a high energy feed to meet energy requirements when fed mature hay with a low TDN value.

It is always important to take a sample of the winter forage available to have tested for its nutritive value. Suppose it is assumed that the winter forage available is of medium nutritive value, but is actually of low nutritive value. Then the amount of supplemental feed will not meet the nutrient requirements of the cow reducing cow performance. Also, if the available winter forage is actually of high nutritive value, then more supplemental feed will be purchased than necessary. A forage sample can be sent to the Range Cattle Research and Education Center Forage Extension Laboratory for testing anytime (http://rcrec-ona.ifas.ufl.edu/agronomy/forage-extension-laboratory.shtml).

The last component of the winter supplementation program is supplemental feed type. Feeds are classified based on their protein content, and to some extent their TDN value. High energy feeds such as corn, soybean hulls, blackstrap molasses, and citrus pulp have low protein content, but high TDN value, thus are best suited when cows are deficient in energy but mostly adequate in protein. High protein feeds such as soybean meal, cottonseed meal, and 32% molasses have high protein content, thus are best suited when cows are deficient in protein but mostly adequate in energy. Even though these high protein feeds have a high TDN value, the high protein content can negatively affect performance of cattle when using these feeds to meet energy requirements of cows. When cattle are deficient in energy and protein, a combination of high energy and high protein feeds can be used or feeds that have moderate protein content and high TDN values such as distillers grains, 16% molasses, and corn gluten feed can be used.

In conclusion, to adequately supplement cows this winter, cow nutrient requirements need to be determined through estimates of cow body weight and milk production, available winter forages should be tested for nutritive value, and the type and amount of supplemental feed needs to be determined based on cow nutrient requirements and nutritive value of forage.

Table 1. Effect of nutritive value of winter forage on supplemental feed needs for 1100 lb early lactation cow having peak milk production of 18 lb/day
Item Low Nutritive Value 5% CP; 49% TDN Medium Nutritive Value 8% CP; 54% TDN High Nutritive Value 10% CP; 58% TDN
Forage intake, lb/d
25
27.8
29.5
Molasses 16%, lb/d
8.5
5.5
3.0
Total Feed, lb/d
33.5
33.3
32.5

 

 


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