The functioning of the oesophageal groove reflex and comparison of the performance of lambs fed individually and in groups.

I. Two experiments involving 106 lambs were conducted to study the functioning of the oesophageal groove reflex in lambs sucking from either individual feeders or from a bulk dispenser. The effects on the performance of lambs given either a high-protein or a lowprotein creep feed in conjunction with either a ewe’s milk substitute, Ewelac, or a homogenate of calcium caseinate, Casilan, were studied. Two milk substitutes, one with a long and one with a short clotting time were compared in terms of their effects on the incidence of diarrhoea. 2. The location of the liquid feeds in the stomach was studied radiologically. 3. In both experiments the sucking behaviour of the lambs was closely related to the functioning of the oesophageal groove reflex and performance of the lambs. In the first experiment the milk substitute consistently entered the abomasum in seven of the ten individually fed lambs and in twelve of the twenty-two group-fed lambs. The corresponding figures for the second experiment were twenty-two of the twenty-four individually fed and thirty-four of the fifty group-fed lambs. 4. When the milk substitute entered the abomasum it always did so throughout the fattening period even in those instances where the milk had been withheld for I month. 5 . Poor sucking, low milk consumption and the entry of the milk into the rumen resulted in very poor performance by the lambs. Such lambs demonstrated a non-specific unthriftiness similar to the ‘tail enders’ sometimes observed with lambs reared with ewes. 6. Continued feeding with either the milk substitute or casein homogenate with a lowprotein creep feed did not improve performance. 7. The clotting time of the milk substitute did not appear to influence the incidence of diarrhoea among the lambs.