animal welfare concerns (Matthews, 1992; Moore and Mepham, 1995; Seamark, 1993), these generally are not specific to the production of genetically engineered animals. Few of these procedures have received systematic study from the perspective of animal welfare (Van der Lende et al., 2000).

Handling and restraint can be distressful to farm animals (Grandin, 1993) but are essential for almost all husbandry procedures, including those involving reproductive manipulation. Certain reproductive manipulations (e.g., the administration of injections to induce ovulation) can cause additional transient distress, as can electroejaculation.

AI and embryo collection and transfer present a range of animal welfare issues depending on the species used. In cattle, these procedures can be accomplished with minimally invasive non-surgical procedures—the latter under epidural anesthesia. However, in sheep, goats, and pigs these manipulations involve surgical or invasive procedures (laparotomy or laparoscopy), and hence the potential for operative and postoperative pain. In poultry species the hen is killed in order to obtain early-stage embryos. In fish, eggs and milt might be hand-stripped in some species (causing handling discomfort), while in others the males or females must be killed to obtain eggs and/or sperm.

Since breeding livestock are valuable, they might be subjected to these reproductive manipulations repeatedly during their lifetime. In particular, because of the problems involved in screening microinjected embryos prior to implantation to ensure that they actually are carrying the transgene of interest (Eyestone, 1994), recipient cows might be subject to transvaginal amniocentesis for genotyping; nontransgenic fetuses (or male fetuses) are then aborted and the cows reused as recipients (Brink et al., 2000). While this limits the number of recipient animals used, it also raises welfare concerns over the repeated exposure of individual animals to procedures likely to cause pain and distress.

Replacements for, or alternatives to, some reproductive manipulations are available (Moore and Mepham, 1995; Seamark, 1993). For example, a method has been devised for non-surgical embryo transfer in pigs, and ova for some purposes can be obtained from slaughterhouses, which eliminates the need for manipulation of live donor livestock females. The use of nuclear transfer to produce transgenic animals could eliminate the problem of repeated elective abortion and reuse of recipient animals, since cell populations with specific genotypes or phenotypes could be selected before embryo reconstruction (Eyestone and Campbell, 1999).

IN VITRO CULTURE

The development of in vitro embryo culture techniques has provided an alternative to in vivo culture, but ruminants produced by in vitro culture



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