. Bulletin of the Department of Agriculture. Agriculture; Agriculture. EFFECTS OF IISTBREEDING AND CROSSBREEDIJ^ /9/<S /^/T /S/e /9/9 Fig. 3.—The average gain between birth and weaning (33 days) in the inbred stock during successive 3-nionth periods, 1916-1919. duration) we obtain the desired estimate for inbreds producing litters simultaneously with Experiment Cl. In dealing with other characteristics, the number of matings present in each 3-month period does not necessarily provide the proper weights to be applied to the records of the inbreds. Litters per year, young per year, an
. Bulletin of the Department of Agriculture. Agriculture; Agriculture. EFFECTS OF IISTBREEDING AND CROSSBREEDIJ^ /9/<S /^/T /S/e /9/9 Fig. 3.—The average gain between birth and weaning (33 days) in the inbred stock during successive 3-nionth periods, 1916-1919. duration) we obtain the desired estimate for inbreds producing litters simultaneously with Experiment Cl. In dealing with other characteristics, the number of matings present in each 3-month period does not necessarily provide the proper weights to be applied to the records of the inbreds. Litters per year, young per year, and young raised per year are properly weighted by the num- ber of matings, but in the case of size of lit- ter the number of lit- ters produced by the given experiment in each 3-month period (Table 23) should be used. The percentage of young born alive, the percentage raised of all bom, and the birth weight of all born should be weighted by the number of young born in each 3-month period as given in Table 24. There is a slight impropriety here, owing to the use of indices for these characters, but it is of no practical impor- tance. Similarly the percentage raised of the young born alive is to be weighted by the numbers born ahve, shown in Table 25. The birth weight of the young raised, the rate of gain to weaning, and the weight at weaning are to be weighted by the numbers weaned in each period, shown in Table 26. The estimated record of the inbreds, simul- taneous with each ex- periment, is shown for each character in Table 28. This method of cor- recting for the seasonal fluctuations rests on the assumption that the condition of the total inbreds was genetically constant during the four years. Theoretically one would expect practical constancy in each family after a dozen generations of brother-sister mat w ~ A? '^-e T^S/0-/e,J-3 4-6 ^ 7-9 /a-/ZjJ-J 4^-6 7-9 /0-/2,s/-3 4-6 ?-& MHZt /9/6 /9/7 7§73 7S7h Fig. 4.—The average number of litters produced per year by mature
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