Increased Milk Production, Concentration of Unsaturated Fatty Acids and Conjugated Linoleic Acid in the Milk of Holstein Lactating Cows using Monensin

Conjugated linoleic fatty acid (CLA) in milk fat has a positive effect on cardiovascular health, so efforts have been focused on increasing this fatty acid in cow's milk. Ionophores, including monensin, have been shown to increase milk production performance and immune capacity in the diet of lactating cows. In addition, monensin may have beneficial effects on milk production and the body's immune system, as well as milk composition and the pattern of milk fatty acids in dairy cows. Therefore, the main purpose of this experiment was to investigate the effect of monensin on the production, composition and pattern of milk fatty acids in Holstein cows

4 lactating Holstein lactating cows (mean calving 3.5) with an average weight of 507±14 and lactation days 91±16 days in a rotating Latin square design (rotating) 4× 4 randomly Four experimental diets were allocated. Experimental diets included levels of 0, 250, 350 and 450 mg monensin per kg of dietary dry matter. Each cow received all experimental diets over 4 periods. The length of each experimental period was 21 days, of which the first 14 days of each period were considered for adaptation of cows and the last 7 days were considered for data collection. Diets were balanced using NRC (2001) software. The ratio of forage to concentrate in all four diets was 44 to 56%. The cows were milked twice a day and the record of both meals was recorded as a daily record. Feed and manure samples were analyzed for dry matter, organic matter, crude protein, crude fat, NDF. Milk production was also recorded daily in a 7-day data collection period. Milk sampling was performed on days 17 and 18 of each experimental period. The pattern of milk fatty acids in the nutrition laboratory of Ilam Veterinary Office was determined by gas chromatography.

The results of this study showed that the addition of monensin significantly increased the production of raw milk and corrected milk for 4% fat (p<0.05). Monensin also reduced the concentration of short-chain fatty acids in milk fat, but had no significant effect on the concentration of medium-chain and long-chain fatty acids. The addition of monensin decreased the concentration of saturated fatty acids and increased the unsaturation of 18: 1 (omega-9) and 18: 1 (trans-9) and conjugated linoleic acid (cis-9, trans-11) in milk

In general, this study showed that monensin increases milk production, concentration of unsaturated fatty acids, conjugated linoleic acid in milk fat and decreases the concentration of short chain fatty acids and saturated fatty acids in milk fat.