Effect of whole cottonseeds and calcium salts of long-chain fatty acids on performance of lactating dairy cows.

Holstein cows were assigned to diets containing no supplemental fat, supplemental fat from whole cottonseed, or supplemental fat from whole cottonseed plus Ca salts of fatty acids (Megalac). The TMR contained 46% forage and 54% concentrate or mixtures of concentrate and whole cottonseed on a DM basis and were fed from wk 3 through 44 of lactation. The mean fat content of the three diets was 3.0, 4.7, and 6.4% of DM for control, whole cottonseed, and whole cottonseed plus Ca salts of fatty acids, respectively. Supplemental fat increased NEL intake, percentage of milk fat, milk fat production, and rate of recovery of BW and body condition. Supplemental fat decreased milk protein production in early lactation, but not in late lactation. Addition of supplemental fat had no significant effect on ruminal concentration of VFA, NH3 N, or in situ digestibility of fiber. The proportion of unsaturated fatty acids in milk fat was increased with supplemental whole cottonseed or whole cottonseed plus Ca salts of fatty acids. During the first 3 mo of lactation, the proportion increased of fatty acids C14 or less, C16, and C18:2. Proportion of fatty acids C16:1 and C18:1 correspondingly decreased. The change in composition of milk fatty acids during early lactation is consistent with the use of body fat for milk synthesis.