Growth performance, ruminal fermentation characteristics and microbial protein synthesis of lambs fed palmitic and stearic acid

The objective of this experiment was to investigate the effects of palmitic and stearic acids individually or in combination on growth performance, rumen fermentation, rumen cellulase activity, and microbial protein synthesis of lambs. Thirty male Dalagh-Romanov crossbred lambs with an average initial weight of 26 +/- 2.7 kg were used for 89 days in a completely randomized design. Experimental treatments included: 1) control diet (no added fat); 2) control diet with a 3% palmitic acid-enriched supplement; (3% PA) 3) control diet with a 3% stearic acid-enriched supplement; (3% SA), 4) control diet with 3% mixture of 2% palmitic acid and 1% stearic acid; (2% PA + 1% SA) and 5) control diet with 3% mixture of 1% palmitic acid and 2% stearic acid; (1% PA + 2% SA). Results showed that fatty acid supplementation (FA) had no significant effects on dry matter intake (DMI), average daily gain (ADG), and feed conversion ratio (FCR) of lambs. However, a trend towards higher final weight was observed in lambs fed 3% PA compared with the control group (P = 0.088). Contrast showed that final body weight was also increased in lambs receiving the fat supplements compared with the control lambs (P < 0.05). The addition of fatty acids did not affect rumen pH but increased the concentration of ammonia nitrogen in all SA-containing diets fed to lambs (P < 0.05). Total volatile fatty acid (VFA) concentrations remained unchanged among treatments, but branched-chain fatty acids (BCFA) and acetate-topropionate ratio were higher in lambs fed SA compared with control (P < 0.05). There was also a trend towards lower propionate concentration at 3% SA and 1% PA + 2% SA compared with the control (P = 0.07). The total population of protozoa increased in the FA mixtures compared with the other treatments (P < 0.05). The extracellular activity of carboxymethylcellulose (CMCase) increased in lambs fed SA-containing diets compared with the control (P < 0.05). Total activity of microcrystalline cellulase (MCCase) was also increased in lambs fed SA compared with control and 3% PA groups (P 0.05). Microbial nitrogen supply (MNS) and efficiency of microbial nitrogen (EMNS) were not affected by the treatments (P 0.05). Thus, it can be concluded that FA supplements and PA in particular with 3% of the feed DM have the potential to increase final BW without increasing MNS, probably due to the efficient use of FA.

Automated summary

The objective of this experiment was to investigate the effects of palmitic and stearic acids individually or in combination on growth performance, rumen fermentation, rumen cellulase activity, and microbial protein synthesis of lambs. Fatty acid supplementation had no significant effects on dry matter intake, average daily gain, and feed conversion ratio of lambs. However, a trend towards higher final weight was observed in lambs fed 3% palmitic acid compared with the control group.