The effect of an anabolic agent on N deposition, growth, and slaughter quality in growing castrated male pigs.

The conversion of feed protein into body protein in growing pigs is rather unfavourable. With Dutch Landrace pigs only 30--40 percent of the digestible crude protein is converted into body protein. To study the influence of implanting 20 mg 17beta-estradiol + 140 mg trenbolone acetate per animal on this conversion ratio, three nitrogen-balance experiments were performed with castrated male pigs of 55--75 kg liveweight. In experiment 3 the energy balance was also measured. N-retention was significantly improved by the treatment. In none of the experiments the digestibility of the ration was influenced. With the pigs implanted at around 55 kg live weight, N-deposition during the period from 6--9 till 26--32 days after treatment was increased by on an average respectively of 24 percent (experiment 1), 60 percent (experiment 2) and 56 percent (experiment 3) as compared with a placebo. Where pigs of 75 kg were implanted, N-deposition was increased over the period from 2 till 28 days after implantation by 39 percent as compared with a placebo. In experiment 3 it was shown that the conversion of the metabolizable energy of the ration into energy deposited in the body (= protein + fat) was not considerably altered at 13--17 days after the treatment of pigs (weighing 55 kg) with anabolic agents. As compared with the placebo, N-deposition was increased by 40 percent and fat deposition was descreased by 15--20 percent. So the implantation with the anabolic agents has resulted in shift to a higher protein deposition and a lower fat deposition. The results of the balance determinations were confirmed in a comparative growth experiment, in which 14 castrated male Large Wht& x Landrace pigs of 56 kg weight (i.e. 69 days before slaughter at 90 kg live weight) were implanted with the aforementioned combination; 14 animals served as control. In the period from treatment till slaughter live weight gain was significantly improved by 6.5 kg; feed conversion was 0.3 units significantly lower than the control. Carcass weight was significantly higher for the treated group (difference compared with control 4.5 kg). Carcass quality was also improved; the carcasses of the treated pigs were longer and the thickness of the backfat was less. In a second comparative experiment on growth of castrated male pigs from 66 to 100 kg, the effect of the oral application of the combination ethinylestradiol (0.6 ppm, 1.2 ppm, and 2 ppm respectively in the feed) and trenbolone acetate (2 ppm in the feed) was studied. The three experimental groups and the control group consisted of 15 animals each. Live weight gain was significantly improved in the two groups with the higher levels of ethinyl estradiol (i.e. 4.4 kg and 6.9 kg respectively), feed conversion was significantly lower in all three anabolic agroups (i.e. 0.2, 0.3 and 0.4 respectively). Backfat thickness was less in all three anabolic groups and the carcasses were longer in the two higher dosage groups compared with the control group...