Effect of betaine on fat content in growing lambs

A total of 48 weaned Manchego breed lambs (same number of males and females) with an initial live weight of 11.5 kg were randomly distributed into four pens to study the effect of betaine supplementation in a 2×2 factorial design with dietary betaine and sex as main effects. Weaned males and females were fed on a starter diet for 3 weeks (aprox 20 kg live weight) and then were changed to a finisher diet for another 3 weeks. Within each feeding period, the starter and finisher diets containing 0 or 2 g kg−1 betaine were fed to each group of males and females lambs. No effect of betaine was observed on weight gain and final body weight of lambs. The evolution over time of ultrasonic determination of subcutaneous fat thickness (FT) showed a significant lower FT from near week four of experiment to slaughter in lambs receiving the diet enriched in betaine (P<0.0001). No effect of sex was observed on FT. Measurement of longissimus dorsi muscle area showed no effect of sex or diet. Muscle area and FT measured on the carcass showed similar results. A lower concentration of neutral lipid in intramuscular fat of lambs fed diets enriched in betaine than in those fed the basal diet, was also observed (P=0.0211), which suggest a generalized effect of betaine lowering animal fat in all lamb tissues. No effect of diet or sex was observed on polar lipid concentration in muscle. No effect on individual fatty acids was observed in any case, but lambs fed diets enriched in betaine had slightly lower concentration of (n-6) fatty acids (P=0.0479) and higher concentration of monounsaturated fatty acids (P=0.0478) in neutral lipids of intramuscular fat.