Effects of day relative to parturition and dietary crude protein on rumen fermentation in prepartum transition XXXX .

@entity844 @entity1133 @entity3265 @entity4322 @entity1503 @entity3691 @entity291 @entity413
Twelve Holstein @entity291 and eight heifers were used in a randomized block design to examine changes in @entity1503 as animals fed diets containing 9.1 (low protein, LP) or 11.2% crude protein (moderate protein, MP) approached parturition. Animals were blocked by expected calving date and parity. Diets were isocaloric (1.58 Mcal/kg of dry matter), and the difference in dietary crude protein was achieved by the addition of @entity1133 . Diets were fed as total mixed rations for ad libitum intake. Dry matter intake decreased from 12.2 kg/d on d -21 to 9.1 kg/d on d -1 relative to parturition and was unaffected by dietary crude protein or parity. Rumen @entity3265 concentrations were higher for animals fed the MP diet compared with those fed the LP diet (1.8 vs. 3.7 mM). In situ neutral detergent fiber disappearance was not affected by dietary crude protein after 8 h of incubation, but it did decrease from 25.8% on d -21 to 23.3% on d -1. After 16, 24, and 48 h of incubation, neutral detergent fiber disappearance was greater for animals consuming MP than for animals consuming LP (30.6 vs. 34.4%, 37.0 vs. 44.1%, and 57.9 vs. 65.1%, respectively). There was a parity x treatment interaction after 48 h of incubation. Fiber disappearance was 55.7 or 65.9% for heifers and 60.0 or 64.7% for @entity291 fed LP or MP, respectively. The solids rate of passage was not affected by treatment, parity, or day relative to parturition. Concentrations of plasma nonesterified @entity844 ( @entity3691 ) increased from 218 microEq/L on d -21 to 619 microEq/L on d -1. There was an interaction between day relative to parturition and parity on @entity3691 concentrations. Heifers had plasma @entity3691 concentrations of 272 and 772 microEq/L on d -21 and -1, respectively. @entity291 had @entity3691 concentrations of 164 and 467 microEq/L on d -21 and -1, respectively. Plasma @entity413 concentrations were affected by parity (65.8 and 58.8 mg/dl for heifers and @entity291 ). Plasma @entity1133 , @entity3691 , @entity4322 , and @entity413 concentrations were not affected by dietary treatment. In conclusion, heifers tended to have higher plasma concentrations of @entity3691 and @entity413 , but did not have elevated concentrations of @entity4322 . Rumen fermentation was relatively unaffected by day relative to parturition, but feeding less than 11% crude protein to prefresh transition @entity291 may limit ruminal fiber degradation.
