Oertzenweg 19 b
+49 30 838 62600
The objective of this study was to determine if the forage-to-concentrate ratio (F:C) of diets fed prior-to and during (PRE) feed restriction (FR), and diets fed post FR (POST) effect the recovery for DMI, ruminal fermentation, and short-chain fatty acid (SCFA) absorption following FR. Twenty ovariectomized and ruminally cannulated Angus × Hereford heifers were used in this study and were fed (ad libitum) either a high forage (HF; F:C = 92:8) or a moderate forage diet (MF; F:C = 60:40) for 19 d. Heifers were then exposed to a 5-d FR period where feed was restricted to 25% of ad libitum intake relative to that measured during the previous 5 d. After FR, heifers were provided feed ad libitum with one half of the HF and MF heifers receiving the HF or MF diet during the 3-wk recovery period (REC1, REC2, and REC3). This resulted in 4 treatment combinations separated over time (PRE-POST): HF-HF, HF-MF, MF-HF, and MF-MF. Interactions of PRE × POST were not significant for any of the measured variables, and the PRE × POST × period interaction was only significant for the molar proportion of ruminal butyrate. For heifers fed HF PRE, DMI increased from REC1 to REC3, while DMI did not differ among periods for heifers fed MF PRE (PRE × period, P = 0.045). The duration was affected by a PRE × period interaction (P = 0.003) such that pH < 5.5 was numerically greater during REC1 for heifers fed HF than MF PRE (191 vs. 98 min/d), with duration decreasing from REC1 to REC2 for heifers fed HF PRE. Total ruminal SCFA concentration and absorption rate were not affected by the diet fed PRE (P > 0.05) or period (P > 0.05). For heifers fed MF POST, DMI increased from REC1 to REC3 whereas DMI did not differ among REC periods for heifers fed HF POST (POST × period, P = 0.033). The duration that ruminal pH was < 5.5 was greater for heifers fed MF than HF POST (274.9 vs. 14.1 min/d; POST × period, P < 0.001) with MF heifers decreasing duration from REC1 to REC2, whereas, duration did not differ among periods for HF. Ruminal SCFA concentration and rate of absorption were not affected (P > 0.05) by diet fed POST. It is concluded that feeding an MF diet prior-to and during FR improves the recovery response for DMI. Irrespective of the pre-feeding, however, an HF diet is beneficial in the POST-restriction period because it most effectively alleviated ruminal pH reduction and hastened DMI recovery.