The effects of pregnancy and lactation on rumen motility.

Abstract

245 The effects of pregnancy and lactation on rumen motility L.A. Zaenuri and I.R. Godwin School of Rural Science and Natural Resources, University of New England, Armidale NSW 2351 During pregnancy and lactation there is an increase in voluntary food intake. As the embryo develops during pregnancy the growth of the foetus and the uterus reduces abdominal space and limits the capacity of the gut to receive more food. How is the increase in food intake sustained in the face of a reduced abdominal volume? We monitored the fkequency of reticula-rumen contractions and rumen turnover rate in six merino ewes from the non-pregnant state, through pregnancy until the first 2 months of lactation. The sheep were fitted with rumen cannulae, housed in metabolism cages and fed a mixture of equal quantities of oaten and lucerne chaff ad libitum. A balloon pressure transducer was placed in the reticulorumen and connected to a computerised recording apparatus allowing continuous recording of reticulorumen contractions. After baseline non-pregnant data were obtained, the animals were mated and confirmed pregnant by ultrasound. The housing and recording procedures were then repeated periodically over the duration of pregnancy and 2 months of lactation. Primary secondary contraction fkequencies were determined from examination of the pressure traces. Rumen fluid volume and outflow rates were determined by CrEDTA dilution. The changes in rumen volume and turnover rate are shown in Figure 1. Rumen volutne remained relatively constant during pregnancy, but increased by about 30% during lactation. Rumen outflow rate steadily increased throughout pregnancy and lactation. Reticulo+umen contraction frequencies obtained are shown in Figure 2. Primary rumen contractions increased after about 90 days of pregnancy and remained at this level with a slight drop in contraction rate after parturition. Secondary contractions showed no major changes in tiequency. The data indicate that the increased food intake of pregnancy and lactation is accompanied by an enhanced mixing motility of the reticulo-rurnen, with no apparent increases in eructation of gases; thus producing a greater rumen outflow rate. Recent Advances in Animal Nutrition in Australia 1997 University of New England, Armidale NSW 235 I, Australia