Effect of feeding an energy supplement prepartum and postpartum on milk yield and composition, and incidence of ketosis in dairy cows

Forty dry pregnant multiparous Holstein cows housed in a free stall barn on a commercial dairy were blocked and assigned randomly to treatments to evaluate the effect of feeding an energy supplement for 3 weeks prepartum and 3 weeks postpartum on milk production and composition, and incidence of ketosis. The energy supplement, which was in powder form, contained 78.43% propionic acid, 21.36% calcium, 0.155% zinc and 0.053% copper (DM basis). Diets were fed as total mixed rations (TMR) for ad libitum intake and contained (DM basis) approximately 56% forage and 44% concentrate for dry cows, and 44% forage and 56% concentrate for lactating cows. In addition, cows fed the supplemental diet received 0.11 kg per day of the energy supplement (DM basis). Prepartum DM intake by cows fed the TMR containing the energy supplement and cows fed the control TMR were 13.1 +/- 2.6 and 12.6 +/- 1.9 kg per day, respectively. Feeding cows the TMR containing the energy supplement decreased milk fat percentage (P = 0.02) and fat yield (P = 0.02), compared with cows fed the control TMR, during weeks 1-3 postpartum. There were no differences between treatments in milk yield, milk CP, milk true protein, milk urea N and somatic cell counts during weeks 1-3 postpartum, and urine ketone scores during weeks I and 2 postpartum. Feeding cows the TMR containing the energy supplement tended (P = 0.07) to decrease serum non-esterified fatty acids during week 1 postpartum, and decreased subclinical ketonuria during week 1 (P = 0.03) and week 2 (P < 0.01) postpartum compared with the control TMR. After feeding of the energy supplement was discontinued at week 3, cows previously fed the TMR containing the energy supplement tended (P = 0.17) to continue to produce milk containing a lower fat percentage during weeks 4-8 postpartum compared to cows fed the control TMR. There were no differences in milk yield, change in body condition score, milk CP, milk true protein, milk urea N, and somatic cell counts between treatments during weeks 4-8. Feeding an energy supplement containing largely propionic acid to Holstein cows for 3 weeks prepartum and 3 weeks postpartum lowered milk fat yield and tended to decrease the concentration of non-esterified fatty acids, thus suggesting lowered catabolism of adipose tissue in early lactation. Feeding this supplement to close up dry cows through early lactation could prevent fat mobilization and subclinical ketosis normally associated with calving. (C) 2003 Elsevier Science B.V. All rights reserved.