The statistical basis of selection in animal husbandry. II. Studies on life performance of brood sows: the judging of brood sows by their number of offspring born and reared in the earliest litters

Abstract

To study the total-life performance of all the 156 sows, they were divided into groups consisting of sows having produced 73 to 77, 78 to 82, 83 to 87, … pigs throughout their breeding life often litters. The frequency distribution, of total number of offspring born, thus obtained is shown in Fig. 2.

Effect of Sequence of Pregnancy on Litter Size and Growth in Peromyscus Polionotus

“…Biggers, Finn & McLaren (1962) reported a similar relationship of litter size to litter order in eighteen normal mice and twenty-two mice in which one ovary had been removed before sexual maturity. Evidence that other litter-bearing animals follow this general pattern has been presented by King (1916) and Asdell, Bogart & Sperling (1941) in rats {Rattus norvegicus) and by Lush & Molln (1942), Olbrycht (1943) and Pomeroy (I960) in the sow {Sus scrofa). Generally the decline of litter size in the sow is slower than in the mouse or rat.…”

Genetic and environmental aspects of litter size in swine

“…The effects estimated from If the regression coefficients concerning inbreeding in Table 12 are Table 5) is given in There seems to be no explanation for this unless some of the sows in the latter group were actually inferior and did not farrow in the intervening season. given in Table 15 is There is considerable evidence that sows with litters of more than twelve or so pigs at birth raise no more pigs than those with twelve (Axelsson, 1928;Johansson, 1929;Menzies-Kitchin, 1937;Olsen, 1939;Olbrycht, 1943;Wilson et al, 1960; and data from this study). Thus one might theorize that sizes greater than twelve represent genetic effects for about twelve pigs, and that the rest is random or environmental variation.…”