The effect of physiological state on digestion in the ewe and its influence on the quantity of protein reaching the abomasum

Abstract

Three experiments were carried out on Finnish Landrace × Dorset Horn ewes in various physiological states and given daily 2 kg of a diet containing equal parts of hay and concentrate. In experiment 1 six ewes, each fitted with cannulae in the rumen and abomasum, gave mean estimates for the proportion of their digestible organic matter intake that was apparently digested in the rumen of 0.50 in late pregnancy, 0.64 in early lactation and 0.65 post-weaning ( P < 0.01). The quantities ( g/d) of non-ammonia nitrogen reaching the abomasum were 46.9 for pregnancy, 36.4 for lactation and 40.4 post weaning ( P < 0.001). In experiment 2 the time required to recover an oral dose of chromic oxide in the faeces was significantly ( P < 0.001) lower for ewes in late pregnancy than for barren ewes and the effect was not influenced significantly by the physical form of the roughage (milled versus chopped). In experiment 3 the fractional outflow rate per hour of a chromium-mordanted fish meal supplement from the rumens of eight ewes in the 18th week of pregnancy was 0.053 compared with 0.044 for the same ewes in early lactation ( P < 0.025). It is suggested that the stimulatory effects of pregnancy on the rate of outflow of material from the rumen and on the quantity of protein reaching the abomasum may play a role in the nitrogen economy of the pregnant ewe.