The effect of supplementation of plant and animal- derived dietary oils in pre- and post-parturition Döhne merino ewes on the growth performance of the lambs

Abstract

The objective of this study was to investigate the effect of dietary supplementation of sunflower oil, olive oil, fish oil, and palm oil to pre- and post-parturition Döhne Merino ewes on lamb growth performance. Birth weight, post-natal growth rate, and weaning weight of lambs suckling on supplemented ewes were compared. Fifty South African Döhne Merino ewes, 2–4 years old (second parity), weighing 46–55 kg, with a mean body condition score (BCS) of 3.5 ± 0.4, were randomly divided into groups of 10 animals each. Each group (n = 10 per group) received a daily dose of 30 ml of either sunflower, olive, fish, or palm oil, while the control group received no oil. The study was conducted over a period of 210 days (i.e., 7 months). Oestrus was synchronised through the use of controlled internal drug release (CIDR) devices inserted intravaginally for a period of 15 days. Oestrus synchronisation and oil supplementation commenced simultaneously. At CIDR withdrawal, ewes were injected intramuscularly with 200 IU Pregnant Mare Serum Gonadotrophin (PMSG). Fixed-time laparoscopic artificial insemination (LAI) was performed with diluted Döhne Merino semen 48 hours following CIDR removal. Two weeks after LAI, follow-up Döhne Merino rams were introduced to all 50 ewes for 2 weeks to mate ewes that exhibited any signs of oestrus, as this is standard procedure of the experimental farm, and it was also importatnt that all selected ewes for the experiment conceive, although not part of the objectives of the present research. The production parameters were expressed as an average per group. The mean conception rate and lambing rate of ewes across all groups were 88%. The olive oil treatment recorded the highest conception rate and lambing rate (100% for both), but did not differ significantly (P> 0.05) from other groups. followed by sunflower oil (90%), fish oil (90%), palm oil (70%); the control group had rates of 90%. post-hoc test using Tukey’s HSD to identify significant differences between treatment groups at specific time points at a 95% confidence interval. The IBM Statistical Package for the Social Sciences (SPSS) 27 software programme was utilised. The shortest gestation length of 150 days was recorded for the control group. The gestation lengths of the sunflower oil, olive oil, fish oil, and palm oil groups were 153, 156, 155, and 156 days, respectively, with no significant differences (P > 0.05) between any groups. The birth weights of female lambs from the control, sunflower oil, olive oil, fish oil, and palm oil groups were 5.41 ± 0.87 kg, 5.70 ± 0.61 kg, 5.8 ± 0.70 kg, 5.8 ± 0.74 kg, and 4.9 ± 0.50 kg, respectively. The birth weights of male lambs from the control, sunflower oil, olive oil, fish oil, and palm oil groups were 5.6 ± 1.19 kg, 4.85 ± 0.70 kg, 5.6 ± 0.84 kg, 5.5 ± 0.49 kg, and 5.4 ± 0.33 kg, respectively. The results indicate no significant difference (P > 0.05) between different treatment groups for birth weights for both male and female lambs. There was improvement or significance (P>0.05) on percentage increment in weight over time in weeks 5,9 and 11. There was significant difference experienced in ADG of lambs among groups in weeks 5,6,10,11 and 13. There was no significant difference (P > 0.05) observed in the final body weight at weaning for both males from the control, sunflower oil, olive oil, fish oil, and palm oil groups (28.8 ± 4.93 kg, 25.5 ± 8.13 kg, 29.0 ± 4.88 kg, 30.2 ± 4.59 kg, and 28.8 ± 5.03, respectively) and females from the control, sunflower oil, olive oil, fish oil, and palm oil groups (28.5 ± 4.58 kg, 28.3 ± 3.81 kg, 25.8 ± 6.93 kg, 28.9 ± 4.51 kg, and 27.6 ± 2.46 kg, respectively) for the lambs of ewes supplemented with different experimental dietary oils. There was difference in the effect of plant and animal-derived dietary oils – namely sunflower oil, olive oil, fish oil, and palm oil – on the percentage increment in weight over time and ADG of lambs among groups. The growth performance of the lambs was similar to the control group. It can thus be concluded that, in this study, diets enriched with plant and animalderived dietary oils pre- and post-mating had an effect on growth performance in Döhne Merino sheep.