Nutrition and Management: Feed Intake in Feedlot Cattle

This is a fact sheet from the Nutrition and Management section of the Alberta Feedlot Management Guide,Second Edition published September 2000. The 1200 page guide is available for purchase on CD-ROM.

Take Home Message

• Dry matter intake is a measurable window to the soul of cattle performance.
• Animal performance can be predicted with reasonable accuracy if feed intake is monitored on a daily basis and if historical feed conversions or net energy of current feed ingredients are known.
• Dry matter intake can also be used to troubleshoot pens of cattle.
• If dry matter intake (DMI) is unexpectedly low, changes should be made to correct the problem.
• To determine expected feed intake of cattle combine the base dry matter intake shown in Table 1 with the adjustment factors shown in Table 2.
• If intake of your cattle is significantly below these numbers, then you should make changes to your nutrition and management regime to boost dry matter intake.
• The first step is to monitor DMI.

Optimizing cattle performance is essential to remain competitive. If you finish cattle, common goals are to maximize average daily gain and optimize feed efficiency. If you are a backgrounder, the main goal is to obtain a predictable amount of gain in an efficient manner to meet contract specifications. Feed intake is a powerful tool used by feedlot personnel and nutritional consultants to predict animal performance, meet contract deadlines and to monitor the ongoing progress of pens of cattle.

If you know historical feed conversions or if you know the net energy content of current ingredients you can reasonably accurately predict average daily gain if you monitor dry matter intake (DMI). If your cattle are below expected DMI it serves as a troubleshooting technique that can be used to get pens of cattle back on track. In general, if cattle are eating well, they should be performing well. If dry matter intake is low, animal performance is usually disappointing. Estimates of DMI expressed as a percentage of body weight on a dry matter basis are an excellent tool to monitor ongoing progress of cattle in feedlots. The goal of this fact sheet is to indicate the importance of monitoring DMI and indicate its usefulness as a performance predictor and troubleshooting tool.

Factors Affecting Dry Matter Intake

The generally accepted theory is that cattle on high roughage rations limit their intake by physical means; they simply cannot fit any more feed in the rumen. Physical limitations to feed intake is partially a function of rate of digestion and therefore rate of passage of feed from the gut. If the rate of digestion can be increased, then the rate of passage will most likely increase which in turn allows the animal to consume more dry matter. If the rate of digestion is slow, feed intake is limited due to a full rumen.

Cattle consuming a finishing ration do not stop eating because they can no longer fit any more feed in the rumen. Feed intake of cattle fed a high energy ration is limited by total energy intake. The brain says, “do not consume any more energy!”. These relationships are shown in Figure 1. It is important to be familiar with this basic concept so that we can readily understand and help correct problems with low dry matter intake in cattle consuming high roughage and high concentrate rations. For example, if you feed long chopped silage you may run into dry matter intake problems in cattle fed a high roughage diet but it probably will not significantly influence dry matter intake in finishers.


Figure 1. Relationship of the Nutritive Value of Feed and Feed Intake to Factors Limiting Feed Intake. Adapted from (4).

Estimates of Dry Matter Intake and Adjustment Factors

Dry matter intake alone is an ineffective tool, however if DMI is compared to a benchmark then it becomes a very important management tool. Table 1 shows expected DMI of cattle that are settled in the feedlot. Dry matter intake is influenced by many factors, these factors do not act alone, there are an unlimited number of interactions. Key factors that influence DMI are shown in Table 2. The adjustment factors shown in Table 2 are based on the animal described in Table 1.

Table 1. Expected Feed Intake of Cattle in Feedlots.

Low Protein

“With feedlot cattle, most feed intake responses to crude protein supplementation are the result of an increased rate of gain rather than an increased DMI as a percent of body weight”(1).

Environmental Conditions

The adjustment factors for environmental conditions shown in Table 2 are most accurate when applied to cattle exposed to short periods of heat and cold stress. Feed intake data summarized by Koers & Turgeon Consulting Services (8) over an 8 year period indicates a seasonal pattern in feed intake with feedyards located from the Texas panhandle to Nebraska, Figure 2. This graph indicates that cattle fed during the months of February and March have the lowest level of feed intake which is difficult to explain based on relatively cold temperatures. This data set challenges conventional thinking that feed intake automatically goes up during exposure to cold temperatures. Most feed intake data for ruminants associated with changes in temperature has been generated in short term research trials. Feed intake of cattle in feedlots sometimes drops during exposure to cold temperatures. The reduction in feed intake may be caused by several factors. The cattle may not rise from their well bedded pack as regularly as compared to warmer conditions, therefore they go to the bunk less frequently. In addition, if a silage based ration is fed in extremely cold conditions, it takes excellent bunk management to keep palatable, unfrozen feed in front of the cattle during cold days. In addition, bison reduce their feed intake during winter periods as a strategy for survival. Perhaps the same phenomenon occurs in cattle. In general, feed intake is higher in the summer months than the winter months.


Figure 2. Seasonal Variation in Feed Intake of Feedlot Cattle. Source: Koers and Turgeon, Consulting Service, unpublished.

Table 2. Adjustment Factors for Dry Matter Intake in Feedlot Cattle, based on the example steer shown in Table 1.

Adjustment factor		Multiplier	References
Empty body fat	% Condition score
21.3	5.5	1.0	(7)
23.8	6.5	0.97
26.5	7.0	0.90
29.0	8.0	0.82
31.5	8.5	0.73
No ionophore		1.06	(7)
Tylan		1.00	(10)
Non-implanted cattle, Estrogenic		0.92	(9)
Non-implanted cattle, Trenbolone acetate and estrogenic		0.92	(3)
Heifers, no MGA		0.90	(7)
Heifers, MGA		0.95	(10)
Holsteins		1.08	(7)
Holsteins - British Cross		1.04	(7)
Calf		1.00	(7)
Yearling		1.10	(7)
Lactating		1.35 to 1.50	(7)
Selection pressure for growth rate		1.12	(3)
Environmental conditions See discussion in text
>35°C, with no night cooling		0.65	(6)
>35°C, with night cooling		0.90
25-35°C		0.90
15-25°C		None
5-15°C		1.03
-5 to 5°C		1.05
-15 to -5°C		1.07
< -15°C		1.16
Intake during extreme cold, storms or blizzard may be temporarily depressed
Rain		0.90 to 0.70	(5)
Mud, mild, 10-20 cm		0.95 to 0.85	(5)
Mud, severe, 30-60 cm		0.85 to 0.70	(5)
Long days		1.02	(7)
Short days		0.98	(7)
Compensatory growth		1.10-1.20	(11)
Long chopped forage, background ration		0.80 to 0.95	Personal observation
Long chopped forage, finishing ration		0.95	Personal observation
Low protein		See discussion	(1)

The following numbers which were obtained from Tables 1 and 2 are used to estimate DMI expressed as a percentage of body weight on a dry matter basis of a 700 pound crossbred heifer calf. The heifer has a condition score of 6.5 and is fed during the summer time at 20 C. The heifer is fed a combination of RumensinŽ and MGAŽ and is implanted with a Trenbolone-Estrogenic implant.

Feed intake is an excellent tool for estimating performance of feedlot cattle. The data shown in Tables 1 and 2 give a basis for comparing dry matter intake of feedlot cattle under various conditions. However, the first step is to monitor DMI if you are not already doing so.

References

1. Berger, L.L. and N.R. Merchen. 1995. Influence of protein level on intake of feedlot cattle - Role of ruminal ammonia supply. Symposium: Intake by Feedlot Cattle. Oklahoma state University.
2. Fox, D.G. 1986. Physiological factors influencing voluntary intake by beef cattle. Symposium proceedings: Feed Intake by Beef Cattle. Oklahoma State University.
3. Fox, D.G. et al. 1992. A net carbohydrate and protein system for evaluating cattle diets: III. Cattle requirements and diet adequacy. J. Anim. Sci. 70:3578- 3596.
4. Montgomery, M.J. and B.R. Baumgardt. 1965. Regulation of food intake in ruminants. 2. Rations varying in energy concentration and physical form. J. Dairy Sci. 48:1623.
5. National Research Council. 1981. Effect of Environment on Nutrient Requirements of Domestic Animals. Washington D.C. National Academy Press.
6. National Research Council. 1987. Predicting Feed Intake of Food-Producing Animals. Washington D.C. National Academy Press.
7. National Research Council. 1996. Nutrient Requirements of Beef Cattle. 7th rev.ed. Washington D.C. National Academy Press.
8. Parrott, C. et al. 1996. Feed intake response “Altering Rumensin levels during the feeding period”. Symposium proceedings: 1996 Scientific Update “ On Rumensin /Tylan/Micotil for the Professional Feedlot Consultant”. Elanco Animal Health, Indianapolis, IN.
9. Plegge, S.D. and R.D. Goodrich. 1986. Intake equations for feedlot cattle. Symposium proceedings: Feed Intake by Beef Cattle. Oklahoma State University.
10. Potter, E.L. and J.F. Wagner. 1986. The effect of feed additives and anabolic implants upon the feed intake of beef cattle. Symposium proceedings: Feed Intake by Beef Cattle. Oklahoma State University.
11. Yambayamba, E. and M. Price. 1991. Growth performance and carcass composition in beef heifers undergoing catch-up (compensatory growth). Can. J. Anim. Sci. 71:1021-1029.