RenTip133 11/25/16 Evaluating Feed Additives for Dairy Cows

Transcription

1 RenTip133 11/25/16 Evaluating Feed Additives for Dairy Cows There are many products on the market today with a lot of sales people telling very convincing stories about their product. Sense much of these products are not controlled or governed on their efficiency how do you sort through the stories and evaluate these products. What questions should you ask? 1. What does the product claim to do? (Example to increase milk fat) 2. How does the additive suppose to do what it claims to do? (Example to increases fiber digestion by increasing fiber digesting bacterial activity and producing more acetate and butyrate) 3. Is what the product claims to do important (Example milk fat adds value) 4. Can the product prove that it can do what it claims Do they have research proving the mode of action i. Is the research conducted on the actual product (Example: Meta-analysis of yeast products or on the actual yeast product) Research showing/proving the mode of action Performance trials i. What type of research trials are used to support the proof of the product When evaluating research what really is research, what are the types of research, how are the trial different and which are of most value.

2 Peer Reviewed Controlled Research Uncontrolled Research On Farm Research Anecdotal Evidence Peer reviewed research (most expensive so general products have the fewest of this type) Published in a recognized Journal (JDS, JAS, etc.) o Once the experiment is completed and the paper is written, it is submitted to a Journal such as the Journal of Dairy Science. The Journal will then send the paper to a minimum of two reviewers to review the study design, sample size, methodology, statistical analysis, interpretation of the results, valid conclusions, etc. to see that they were fair and appropriate. This type research is designed and orchestrated to that others could reproduce these studies. Controlled Research This type research could be conducted by a university or research facility and does have a true control and treatment. The results might appear in an Ag Report, conference proceedings, university bulletin, or a company write-up. However the results are not reviewed by a peer review board or published in a Journal. Uncontrolled Research This is where a treatment is applied but there is no appropriate control group. The comparison could be to a previous point of time (before and after using the product). An example would be to put the entire herd on the product and compare to previous production. It is always difficult to compare to previous years

3 production or an earlier time due to changes in feed qualities or time of the year effects. On-Farm Research This is certainly the least costly form of research The perceived advantage is the number of animals used. Most university research is conducted on a small number of animals. This type is difficult to control variation because maintaining animals on a treatment for the entire period. Because these are working dairies it is generally difficult to maintain a large group of animals in the research pens for the entire trial period. Many times it is difficult to balance the control and treatment pens that are similar in parity, production levels and days in milk. What type of records does that dairy maintain to be able to compare. Is it once a month DHIA testing? Anecdotal Evidence The results are based on feelings instead of facts. I think it works, Animals appeared healthier. Research types In vitro means done in the laboratory (desk top fermenter) In situ (in sarco) means done with a fistulated animal In vitro means done with animals Trial designs Controlled research means that there is a true control o Negative control the control does not have any treatment with a similar activity o Positive control the control does have a treatment with a similar activity (Example comparing an all natural treatment to an antibiotic) Switch back design o The group is divided and the treatment is applied to half the animals for a given time followed by the control animals receiving the treatment and the previously treated animals now not receiving the treatment. Factorial trials (example 2X2)

4 Red-flag things on non-peer reviewed studies Switch back or factorial design trials o Is there a carry over effect of the treatment? o While the diets could be formulated the same do changes in feed stuffs (particularly of forages) over time affect the results Selection of the control animals o How equal are the control and treatment groups? Parity (heifers use energy differently than cows) Milk production Actual milk production FCM or ECM Body condition or body condition change over time Is energy going to BCS or being pulled from condition? Days in milk between the controls and treatments Is milk adjusted to a similar DIM if different Components (milk fat requires more energy than fluid milk) How are they measured? How do you handle cows that do not complete the entire trial period? How is dry matter intake measured? o Feed delivered or are the refusals measured o What percent of animals are not on the treatment for the entire period and how does that effect DMI evaluation? Non-treated animals are also eating feed Statistical significant P < 0.05 (means that there is less than a 5% chance the results were due to chance, in other words if you did the experiment 100 times then you have a 95% chance the results would be the same) P < 0.01 (means there is less than a 1% chance the results were due to chance) P < 0.10 (means there is a trend for the results) Type I and Type II error of research

5 Type I Error is the incorrect rejection of a true null hypothesis. (a false positive, in other words the product really doesn t work) Fed/used, but no milk or component response occurred Type II Error is the failure to reject a false null hypothesis. (False negative, the product really does work) Null Hypothesis is a statement that you want to test. In general, the null hypothesis is that things are the same as each other, or the same as a theoretical expectation Response milk production was possible, but was not fed Evaluating field trial data questions to ask What all was measured? How equally were the animals divided on DIM, performance, DMI. etc.? Were any animals excluded from the data analysis why? Milk production measurement how? Monthly DHI, daily milk What environmental factors could of influenced the results? How was body weight or condition measured? Could there have been a carry over effect? Remember how and where energy is used If a product increases energy availability then does the measurements of the trial capture the gain in energy? Energy is used to produce more milk typically only in early lactation. Heifers will typically use extra energy for body condition/growth instead of extra milk production. Cows greater than around 150 DIM will typically eating less rather than produce more milk. So, can dry matter intake be measured accurately? Milk fat requires a lot more energy to produce than milk so evaluate pounds of fat, FCM or ECM.