A note on the effects of health environment on heterosis for growth rate in pigs

Abstract

Heterosis for growth rate in pigs is usually expressed, and reviews of European and North American studies have been given by Sellier (1976) and Johnson (1981). Kennedy and Moxley (1980) observed heterosis of 0·044 to 0·067 for weight at 154 days and attributed some of the crossbred advantage to heterosis for resistance to atrophic rhinitis. Similarly, McGuirk, Bourke and Manwaring (1978) attributed some of the heterosis for growth rate in sheep to heterosis for resistance to pneumonia. Although little attention has been paid to interactions between heterosis and health environment, Barlow (1981) concluded from an extensive review of studies involving farm and laboratory animals that heterosis is environment dependent and is enhanced by increased stress. Sellier (1976) commented that it would be useful to examine the degree of heterosis with ‘specific pathogen free’ pigs raised in a healthy environment, and this study examined heterosis for days to 90 kg in Yorkshire × Landrace pigs under three different environments with respect to health conditions.

Genetic analyses of growth, real-time ultrasound, carcass, and pork quality traits in Duroc and Landrace pigs: I. Breed effects

“…Lerner's (1954) concept of genetic homeostasis (i.e., that heterozygotes are less influenced by environmental effects than are homozygotes) suggests a mechanism for heterosis x environment interaction that has been demonstrated experimentally to exist in a number of species (Barlow, 1981). In pigs, different degrees of individual heterosis for postweaning ADG have been reported for ad libitum consumption vs limit feeding (Gregory and Dickerson, 1952;Skarman, 1965) and for different health status classifications (Kennedy and Quinton, 1987). The low estimates of heterosis for growth rate associated the high mean performance in the present study may reflect such heterosis x environmental interactions.…”

Family Law Exceptionalism in Comparative Law

“…46 As Duncan Kennedy explains, this Savignian dichotomy fits perfectly with the colonial enterprise: colonial powers would harmonize the law of the market according to Western liberal values, while deferring to local traditions in family law. 47 For instance, as Otto Kahn-Freund noted: "The British rulers introduced in India and in many colonies the English law of contract, even the criminal law and the law of civil procedure and of evidence: to introduce the English law of marriage, of parent-child relation, or of succession, would have been impossible." 48 In Ancient Law, Sir Henry Sumner Maine (1822-1888), the wellknown Victorian jurist, showed the disintegration of the patriarchal family as a backward and ancient institution based on notions of status, while the corporation, based on contractual and individualized agreements, represented modernity.…”