FEED ADDITIVES: MODES OF ACTION AND ASSESSING THEIR EFFICACY

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1 FEED ADDITIVES: MODES OF ACTION AND ASSESSING THEIR EFFICACY Limin Kung, Jr. Department of Animal a Food Sciences University of Delaware Newark, DE Iksilage@ udel.edu INTRODUCTION There are many kinds of feed additives that can be used to improve the performance of dairy cattle. Obviously, all additives increase the cost of feeding. The increase is moderate for some products: for example using a silage inoculant costing $0.75 per ton of treated forage would cost about $0.02/cow/d if each cow were fed 60 lb. of wet silageld. However, some additives such as protected amino acids and some protected fats can easily add more than $0.30 to the cost of a cow's diet each day. In these cases, this amount may represent a 6-8% increase in daily feed cost. With so many additives and claims about them one would expect that dairy cows should have no health problems and all produce 150 lb of miwd! Dairymen must decide which additives are needed and must determine whether the use of the additives is efficacious. There are no easy answers to these questions, but this paper will try to explain how one might evaluate the use of additives for dairy cattle. SUGGESTIONS TO FOLLOW BEFORE CONSIDERING USE OF A FEED ADDITIVE Suggestion #l. Before using any dairy feed additive, work closely with your nutritionist and veterinarian to make sure that your rations are balanced on paper. Why? Because, as an example, adding yeast will not solve all your problems if your high cows producing over 100 lb of milkld are fed a diet containing only 14% CP. Suggestion #2. Test feeds regularly to insure that the cows are offered the balanced ration in suggestion #l. Why? Because, for example, we know that forage quality and silage moisture can change considerably between silos and even between days. Suggestion #3. Determine that your cows are "eating" the balanced rations. Why? Because, as examples, load cells on TMR wagons may need calibration, cows may be sorting the TMR, and insufficient bunk space may limit intake by shy or smaller cows.

2 Suggestion # 4. Evaluate housing and management practices that may be affecting your cows in a negative manner. Why? As an example, perhaps the fact that you are moving your cows 5 times between 3 weeks pre- and 3 weeks post-fresh is one cause of many of your post fresh problems. Perhaps reevaluating this process may eliminate the need for a feed additive. USING FEED ADDITIVES Which FeedAdditive Do I Need and Why? Determine which feed additive to choose and the proper amount to use based on a specific need. For example, feeding protected choline to reduce the incidence of fatty livers and ketosis makes little sense in late lactation cows. However, if your next set of cows to calve are a bit on the fat side, protected choline might help. Ask yourself and the recommending person for the signs or symptoms that would suggest using the feed additive. In addition, having records documenting these issues makes sense; otherwise the call is rather subjective. What are the Expected Responses and are they Economical? Even if a feed additive is successful in producing an expected response from an animal, dairymen need to determine whether the response makes economic sense. This process is seemingly straightforward if the expected response is one of increased milk production. If a feed additive costs $O.lO/cow/d, and if milk is work $0.12/lb, then a cow must give 0.8 lb more milkld in order for you to break even. However, breaking even should not be your final goal. Be aggressive and demand a 2: 1 or even 3: 1 return on your investment. This is important because not all cows respond to the same extent or even respond at all. Is There Independent Research Supporting the Additive's Claims? I cannot over stress the importance of asking for evidence that supports a product's claim(s). Research should be independent and preferably published in a peer-reviewed journal such as the Journal of Dairy Science, the Journal of Animal Science, or Animal Feed Science and Technology. (Internally generated research only, or in house technical bulletins are not sufficient for me.) You should be very cautious if a new feed additive is offered to you and it has no independent published research supporting its claims. Unfortunately, this is a common occurrence. How many independent publications are needed to support a product's claim is a more difficult question to answer. The reason for this is that there are many factors that may interact with an additive. Thus, certainly the more positive publications the better. Use some caution in taking the claims from one manufacturer at face value. In the silage world you may often hear claims such this as this, "not all Lactobacillus plantarum are the same" to emphasize the presumed difference between manufacturers. In another example, my lab evaluated several products that were said to be "rumen protected choline". However, we found that only one of these products had any substantial protection from rumen degradation (Kung et al., 2003).

3 EVALUATION OF FEED ADDITIVES ON THE FARM Determining whether a feed additive is efficacious (works and is economical) on your farm is an extremely difficult challenge. Here are several suggestions to follow if you have done your homework and have decided to try a feed additive. It is imperative that you have a good record keeping system that can monitor your herd's performance. Regardless of what the additive should do, having records for milk and reproduction information, body condition scores, SCC counts and health records are a must. Again, without good records, your evaluations will be very subjective. Monitor the cows (records, behavior, etc.) to be fed the additive closely for at least two weeks prior to using the additive. Start feeding the additive without making any other major simultaneous change to management or the ration formulation. This includes even things like changing silos, feeding hay from a different source, etc. (If you change 10 things at the same time you won't know which change resulted in any observed benefit.) Based on the recommendations of the product (some products work quickly, some more slowly) identify an appropriate amount of time for which you will "test" the additive. Following cows individually based on daily milk weights is desirable. Have a "control group" and a "test group" of cows that are similar in terms of DIM, milk production, diet fed, and lactation number, etc. Cows can also be followed as groups. Group intakes can be monitored to estimate changes in DM intake, etc. (This certainly is more difficult on small farms.) Look for a treatment effect in the "test group" versus the untreated cows. This manner of evaluation helps to reduce some of the effects that uncontrollable factors may have during the test period (see below). Alternatively, the "feed and stop-feed" method can be used. Here, all cows in the herd or group are fed the additive for "X" weeks, then feeding is stopped. One can evaluate if there was a response to feeding and also if there was a response to withdrawal of the additive. When evaluating the benefit to cost ratio of your additive remember to try to include the cost of any specialized equipment or change in labor associated with providing the additive. Remember that during your "test period", there are several uncontrollable factors that could affect your results. For example, you may have a spell of extremely bad weather (e.g. a heat wave or ice storm). If you are using groups, cows may be entering the group (new fresh cows, moving into different production groups, etc.) or leaving (culling, drying off, etc.). Thus, be sure to take these factors into consideration when making an evaluation.

4 CONCLUSIONS There is no foolproof method to accurately determine whether a feed additive is working on your farm. However, you can help your assessment by following some of the guidelines presented in this paper. Hutjens (2003) summarized the status of several feed additives and gave them various status ratings. I have streamlined his suggestions, changed the status on some based on more recent evidence, and added some of my own in Table 1. Table 1. A list of some commonly used feed additives for dairy cows. Additive Function Status* Anionic salts Reduces DCAD to reduce Recommended incidence of milk fever Antifungal acids (buffered propionic, sorbate, etc.) for silage Reduces growth of fungi (yeasts and molds) Recommendedcaution, products Aspergillus oryzae Stimulates fiber digestion in the rumen; Evaluate alleviation of heat stress Bacterial-Direct fed Competitive exclusion, production of Experimentalmicrobials enzymes, antimicrobials, growth factors caution, products Bacterial- Silage Stimulates silage fermentaiton, increas- Recommendedinoculant es DM recovery, sometimes improves caution, not all performance, specific bacteria improve products are equal aerobic stability Bacterial- Hay Reduces growth of fungi (yeasts and Not Recommended inoculant molds) Biotin Improves hoof integrity Recommended Beta-carotene Improved reproduction and immune Not Recommended function, reduced mastitis Calcium propionate Increases bloood glucose and calcium Recommended Rumen protected choline Minimizes fatty liver tissues Recommendedcaution, products Enzymes-micro doses Increases fiber or starch digestion Not Recommended usually w/dfm added concentrates are too low to be effective Enzymes-large doses Increases fiber or starch digestion Experimental usually sprayed onto the feed

5 Magnesium oxide Raises rumen ph Recommended Malic acid Increased VFA production and Experimental efficiency Methionine hydroxy Improves milk fat test, may reduce Evaluative analogue fatty livers Niacin Reduces the incidence of ketosis Recommended Plant essential oils Anti microbial effects in the rumen Exverimental Propulene glycol Source of blood glucose, reduce ketosis Recomended Rumensin Alters rumen VFA production and efficiency Recommended-use caution based on specific diets, high levels may depresss milk fat Rumen protected Sources of rumen bypass essential Evaluative amino acids amino acids Sodium bentonite Binds Mycotoxins Evaluative Sodium bicarbonate or sesquicarbonate Stabilizes rumen ph Recommended- Less effective in high forage, high alfalfa diets Yeast culture and extracts Stimulates fiber digesters and lactate Recommendedutilizers in the rumen caution, products Yucca extracts Improves nitrogen efficiency Evaluative Zinc methionine Improved immune response, better hoof Recommended integrity, lower SCC "Recommended = Include the additive as needed. Experimental = Additional research and study are needed before recommending. Evaluative = Monitor under specific situations; research results are variable. Not recommended = Lacks sufficient economic responses to recommend and may have inclusive research at the time of this report. REFERENCES Hutjens, M Economics of Feed Additives. Proceedings of the Penn State Dairy Cattle Nutrition Workshop. Kung 2003 Reference on protected choline from JDS abstracts