Embryonic Losses and the Role of Nutrition — Statistical Considerations

Abstract

Data on correlation between nutritional regimes and proven embryonic Tosses in cattle and swine are negligible. Widespread inconsistency seems to exist concerning criteria or terms to categorize experimental animals subjected to investigations for embryonic losses. For this reason the author has felt it necessary to discuss some highly variable reproductive parameters found in any farm animal population and which may be of importance for evaluation of embryo losses in general and for designing research projects aiming at estimation of correlation between nutrition and proven embryonic losses in particular. At least four interrelated and highly variable parameters of importance for the reproductive efficiency in farm animal herds (dairy cattle) should be considered 1) effectiveness of inse-minations (CR),2) heat detection rate (HDR), 3) days from calving to 1st ins. (C-ins.), and 4) deadline for insemination of cows post partum (see Table 5). From field investigations it appears that in a normal cattle population between 50–60% of the cows may be expected to concieve after an insemination irrespectively whether it is after 1st, 2nd, 3rd, 4th, or 5th successive insemination (Fig. 1) and that regular/irregular interservice intervals occur in a normal population after a variable pattern (mainly due to external factors) (Table 6). From a statistical point of view it is possible to calculate the number of animals required in experimental and control groups to obtain significant differences (Tables 7 and 8). It seems likely that such experiments would require large groups of animals and might bring additional variable factors causing conflicting results.