Effects of transition diets varying in dietary energy density on lactation performance and ruminal parameters of dairy cows
2003
Rabelo, E. | Rezende, R.L. | Bertics, S.J. | Grummer, R.R.
Forty cows and twenty heifers were used to study the effects of dietary energydensity during late gestation and early lactation on lactation performance and ruminal parameters.A 2 x 2 factorial arrangement of treatments was used. During prepartum (-28 d to calving),animals were fed a low energy density diet [DL; 1.58 Mcal of net energy for lactation (NEL)/kg,40% neutral detergent fiber (NDF) and 38% nonfiber carbohydrate (NFC)] or a high energy diet(DH; 1.70 Mcal NEL /kg, 32% NDF and 44% NFC). After calving, half of the cows from eachprepartum treatment group were assigned to a low energy density diet (L; 1.57 Mcal NEL /kg,30% NDF and 41% NFC) or a high energy density diet (H; 1.63 Mcal NEL/kg, 25% NDF and47% NFC) until d 20 postpartum. After d 20, all cows were fed H until d 70. Animals fed DHhad 19.8% greater dry matter intake (DMI; % of body weight) and 21.5% greater energy intakethan animals fed DL prepartum and the response was greater for cows compared to heifers.Animals fed DH had lower ruminal pH compared to animals fed DL, but no major changes involatile fatty acid concentrations were observed. Effects of dietary energy density duringprepartum on postpartum production responses were dependent on parity. Primiparous cows fedDL had higher 3.5% fat-corrected milk yield and milk fat production and percentage during thefirst 10 wk of lactation than those fed DH. Prepartum diet did not affect lactation performance ofmultiparous cows. Cows fed H had higher DMI and energy intake for the first 20 d of lactationcompared to cows fed L. Diets did not affect DMI after the third wk of lactation. Milk productionincreased faster for cows fed H compared to cows fed L. Animals fed DL-L sequence oftreatments tended to have the lowest energy intake during the first 10 wk of lactation. Prepartumtreatments did not affect ruminal fermentation characteristics postpartum. Cows fed H had lowerruminal pH and higher propionate concentrations than cows fed L. No prepartum x postpartuminteractions were observed for ruminal fermentation parameters. The effects of DH on prepartumDMI did not carry over to the postpartum period or influence early postpartum production.Increasing concentrate content of the diet immediately postpartum instead of delaying theincrease until d 21 postpartum is associated with a higher rate of increase in milk production andhigher DMI.
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