Feeding time and sequence of forage rape and maize silage does not affect digestibility and rumen parameters in sheep

Abstract

The objective of this study was to evaluate the effect of time and sequence of feeding forage rape in relation to maize silage on whole tract digestibility and rumen parameters. Three rumen-fistulated castrated male sheep (45 ± 1.2 kg) were individually housed in metabolic crates and fed a diet comprising 25% forage rape, 25% maize silage, 10% concentrate and 40% short rotation ryegrass. The experimental design was a 3 × 3 Latin-square design and treatments were: forage rape fed after maize silage in the morning; forage rape fed before maize silage in the morning; and forage rape fed after maize silage in the afternoon. As the three treatments were identical in composition, the first experimental period comprised a 15-day adaptation period whereas the other two periods had a 7-day adaptation, each followed by 6-day sampling periods for measurement of feed intake and faeces and urine output (day 1–5). Rumen fluid was collected at day 6 of each sampling period and analysed for pH and ammonia concentration. In a subsequent experiment in sacco rumen degradation characteristics of all feeds were measured by incubating nylon bags in the rumen of each sheep. Neither dry matter (DM) intake (mean = 21.2 g/kg liveweight.day) nor whole tract in vivo DM (mean = 0.74) and neutral detergent fibre digestibility coefficients (mean = 0.69) were different (P > 0.05) among treatments. Similarly, neither rumen pH (6.19 ± 0.2) nor ammonia levels (27.2 ± 4.5 mg/100 mL) were affected (P > 0.05) by time of feeding forage rape in relation to maize silage. The calculated efficiency of microbial protein synthesis was similar (P = 0.73) for all treatments [mean = 17 g/day of microbial nitrogen (N) per kg of apparently digested organic matter in the rumen], although the excretion of urinary N was relatively high for all treatments due to high N intake and high degradation of N in forage rape. In conclusion, this study has revealed no effects of time and sequence of feeding forage rape with maize silage on rumen parameters and efficiency of feed utilisation. These results suggest that farmers using these forages can allocate these to animals based on practical convenience.