Maternal experience in Romanov sheep impairs mother-lamb recognition during the first 24 hours postpartum

Romanov ewes give birth to an average of 2.8 lambs per partum and display maternal ability over other sheep breeds; however, few studies have investigated their mother-young mutual recognition. Here, 8 primiparous and 7 maternally experienced (multiparous) ewes and their lambs were studied. Maternal selectivity was evaluated at 3 hours postpartum during 2 consecutive periods of 3 minutes each. Ewes were tested with their own lambs and then with alien lambs. High- and low-pitched bleats, attempts, and rejection to the udder, aggressive behavior toward the lambs, and amount of time that the mother permits the lamb to be near the udder were recorded. At 8 hours postpartum, a double-choice test was performed to assess distal recognition of the lamb by the mother; in the lambs, a double-choice test was performed at 24 hours of age. Latency to reach one of the animals, frequency to visit each, time spent near the choice subject, time spent looking toward them, and frequency of vocalization were recorded. A Mann-Whitney U test was used for between-group comparisons, and a Wilcoxon test was used for within-group comparisons. At 3 hours postpartum, most of the ewes (multiparous and primiparous) were selective; however, multiparous ewes tended to have a higher index of acceptance of their own lambs than primiparous ewes (2.74 ± 0.66 vs. 0.56 ± 0.76; P = 0.083). At 8 hours postpartum, multiparous ewes spent more time looking toward their own lambs than primiparous ewes (50 ± 11.8 s vs. 15.8 ± 8.9 s; P = 0.018). Compared with primiparous ewes, multiparous ewes spent more time near their own lambs than near alien lambs (84.85 ± 19.6 s vs. 21.7 ± 9.7 s; P = 0.05) and more time looking toward their own lambs than toward alien lambs (P = 0.018). At 24 hours after birth, lambs born to multiparous ewes spent more time near their own mothers than near alien mothers (P = 0.043) and visited their own mothers more than they visited alien mothers (P = 0.05). In contrast, lambs born to primiparous ewes did not show similar behaviors (P ≥ 0.73). In conclusion, in Romanov sheep, maternal experience affects mostly nonolfactory recognition of the lamb and also influences the ability of the lamb to recognize its mother.