Guideline No. 10
Amendment of Section II(G)(1)(b)(4) of the Preclearance Guidelines
Revised October 1975
U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES
PUBLIC HEALTH SERVICE
FOOD AND DRUG ADMINISTRATION
CENTER FOR VETERINARY MEDICINE
(4) Specific Considerations for Lactating Dairy Cows
This section addresses those studies designed for purposes of supporting a claim of increased milk production of some component therein for a drug. This section equally addresses those studies used to support the utility of food additives and those studies designed to evaluate the animal safety of drugs and food additives.
[a] Claims
[1] Increased milk production
For this claim, the amount of milk produced during the entire lactating period (at least 305-days) should be measured. If the claim is for a specific period of time which is less than 305-days, the data should support the claim for this specified period. However, for the shorter period this increase should not affect (decrease) the level of milk production or any other related parameter during the remainder of the lactation period. Of interest is the pounds of actual milk and yields adjusted for solids or other major constituent.
[2] Increased production of milk component
For this claim, the average composition of milk for that component for the entire lactation (at least 305-days) or the average component production for the entire lactation (at least 305-days) should be evaluated. The period of increase for the respective component could also be of shorter duration if the data supports such. The remainder of the lactation period for this component or any other parameter not intentionally affected could not be adversely affected by the increase during the period of treatment.
[b] Design of studies
[1] Full lactation studies
((a)) Cows to be used in these studies should be blocked or balanced into groups according to age, calving date and production during a three week standardization period immediately after parturition or previous DHIA production (if records are available) or other previous production records. All cows used in such studies should have been previously maintained at the same location and at the same level of nutrition. The use of first lactation cows should be kept to a minimum. Cows within a block should be randomly assigned to treatment.
((b)) Other designs will be considered upon request.
((c)) Reference is also made to section II(A), (C), (D) and (H) of these guidelines.
[2] Short term lactation studies
((a)) For the short term study which begins at parturition, the cows should be blocked or balanced into groups on the basis of age, calving date and production during a three week standardization period immediately after parturition or previous DHIA production (if records are available) or other previous production records.
For the short term study which begins at a time other than at parturition, cows should be blocked or balanced into groups on the basis of stage of lactation, level of production and body weight observed during a three week standardization period. The cows within blocks should be randomly assigned to treatment groups. As above, cows used in such studies should previously have been maintained at the same location and at the same level of nutrition.
((b)) Other designs will be considered upon request.
((c)) Reference is also made to section II (A), (C) (D) and (H) of these guidelines.
[c] Parameters to be measured
[1] Milk yield - Daily milk weights from each cow are desired. Other weighing periods will be considered.
[2] Milk constitutents - Composite samples (morning and evening) taken bi-weekly and weighed for morning and evening milk yield are desired.
[3] Cow weights
((a)) Ideally, cow weights should be taken at a constant time with relation to milking and feeding.
((b)) The initial weight for all studies should be taken on day zero of the standardization period followed by weights being taken on day 21 of the standardization period. This last weight will serve as the day zero weight of the lactation trial.
((c)) For the full lactation or short term study, weights should be taken every three weeks and at the end of the study. For those studies which begin at parturition weights should be taken at parturition, every subsequent three weeks and at termination of the study.
((d)) All weights should be based on one weighing.
[d] Data to be provided for each study
[1] Average daily milk yield for each cow and each treatment.
[2] Fat and solids corrected milk for each cow and each treatment.
[3] Milk fat (percent and total amount), milk SNF (percent and total amount) and milk protein (percent and total amount) for each cow and each treatment.
[4] Total dry matter intake for each cow and each treatment. Energy intake should be provided if possible (mcal NE or lbs TDN/day).
[5] Body weight change for each cow and each treatment.
[6] Persistency of milk and constituent yield for each cow and each treatment for the length of the designated experimental period with the base being the three week standardization period. Subsequent three week periods will be used for persistency comparisons. For complete lactation studies which begin at parturition, the base period will be the first month of lactation.
[7] Efficiency (total FCM or SCM or specific component which may be affected by the additive/unit of energy intake) for each cow and each treatment. This applies only to those studies in which the cows are not on pasture.
[e] Cow Management
[1] Full lactation studies - If the treatment begins at parturition or immediately following the three week standardization period, all cows should be adjusted to the basal diet two weeks prior to parturition. Initiation of additive administration will depend on previous knowledge of the additive in question.
[2] Short term lactation studies - The short term lactation study may begin at parturition, three weeks following parturition or at any other time during the lactation study. If the study begins at parturition or three weeks following parturition, the basal diet should be fed beginning two weeks prior to parturition. If the study begins during another part of the lactation period, the basal diet should be fed for a minimum of three weeks prior to initation of the study.
[3] Herd health - The following are parameters of concern for the evaluation of the effects of herd health on treatments and vice versa: post-partum interval, genital diseases, services required for conception, milk fever, ketosis, mastitis, abortions, etc. All herd health problems and therapy will be reported for each animal and each treatment.
[4] Concentrate adjustment - Concentrate level should be adjusted every 14-28 days in accordance with production level.
[f] Animal Safety - See section II (G) (5).
[g] Statistical Analysis - If the cows are individually fed the additive, then the individual cow will be considered the experimental unit. If the additive is provided on a group basis, the treatment group will be considered the experimental unit with more than one group per treatment (replicated in time or location) needed for a valid statistical analysis. Section II (C) of these guidelines will be applicable in determining the minimum effective dose.
September 1976
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