19 Comparative Evaluation of Human-edible Animal Products Derived from Offspring of Genome Edited and Control Cattle

Abstract Risk assessments of genetically modified (GM) animals include evaluating whether milk and meat derived from the GM animal is as nutritious to humans and/or animals as traditionally-bred animals. The underlying assumption of this comparative approach is that traditionally-bred animals have a well-established history of safe use. The goal of this project was to provide empirical data on the development and nutritional composition of animal products derived from the offspring of a genome edited dairy bull, homozygous for the dominant PC Celtic POLLED allele. The bull was crossed with horned Hereford (HH) cows (pp) to obtain five male and one female heterozygous hornless (RC) calves. Hereford, Angus and Holstein bulls were also bred to Hereford cows to produce five HH calves, two polled Angus/Hereford (AH) calves, and three horned Holstein/Hereford (HO) calves (with 25% genetic identity to the hornless offspring), respectively as contemporary controls. Weights were recorded at 8 months, 1 year and slaughter (n = 9–16). Following calving, individual quarters of the RC heifer (RC.calf1), one HO heifer (HO.calf2), two horned HH heifers, and one contemporaneous hornless AH cow (3113) were milked at varying timepoints during the first seven weeks of lactation. Meat samples were collected from the 6 hornless RC calves and 3 horned HO comparator offspring after slaughter. Proximate analysis was conducted for meat and milk samples. Cattle that inherited a POLLED allele from the genome-edited bull showed no differences in their overall growth (Figure 1) or meat composition (Figure 2) when compared to contemporary controls. Milk composition varied between animals and by days in milk (DIM), although values were within the normal range reported in peer-reviewed literature (Figure 3). Bovine milk composition is known to be influenced by breed, nutrition, parity, and DIM, making it difficult to obtain appropriate comparators in experiments with a limited number of GM animals.