A higher proportion of female lambs in Kurdish × Romanov ewes fed a diet rich in n-3 fatty acids and rumen undegradable protein around mating

An increased intake of rumen undegradable protein (RUP) or n-3 fatty acids (FA) around mating is connected with improved reproductive efficiency in ewes. This experiment was aimed to study whether the ratio of female lambs was greater when Kurdish × Romanov ewes were received a diet rich in n-3 FA and RUP together around mating. Experimental diets were supplemented with 5% (DM basis) Ca salts of saturated FA (SFA), 5% Ca salts of fish oil (as n-3 FA source; n-3FO), or a combination of 5% Ca salts of fish oil and 5% fish meal (as a RUP source; n-3FO+RUP). The results showed that the proportion of total n-3 polyunsaturated FA (PUFA) in plasma increased and the n-6:n-3 decreased at CIDR removal day in animals received the n-3FO+RUP diet (P 0.05) compared with the other diets. Plasma concentrations of oestradiol, glucose, and urea nitrogen (UN) at the day of oestrus (P 0.05) was also lower when ewes received the n-3FO+RUP diet compared with the other diets. The ratio of female lambs was greater when ewes were fed the n-3FO+RUP diet around mating (P 0.05) and was greater than an expected 50:50 ratio (72% females, P = 0.028). It was concluded that feeding ewes a diet rich in n-3 FA and RUP content around mating, rather than n-3 FA alone, could skew the sex ratio of lambs toward females.