RELATIONSHIPS AMONG EWE MILK-PRODUCTION AND EWE AND LAMB FORAGE INTAKE IN TARGHEE EWES NURSING SINGLE OR TWIN LAMBS

Targhee ewes with single or twin lambs were used in four trials during early lactation through weaning to evaluate ewe milk production (MP), kilograms of lamb weaned, and forage intake by ewes and lambs. During Trial 1, ewes with lambs were individually penned, fed .45 kg of barl ey.ewe-1.d-1 and allowed ad libitum access to chopped alfalfa hay. Tri als 2, 3, and 4 were conducted on three different types of Western ran ge environments. Forage intake of ewes in Trials 2, 3, and 4 and of la mbs in Trials 3 and 4 was estimated using chromic oxide. Estimates of milk production were obtained by hand-milking. Average lamb age was 4, 50, 78, and 106 d at the beginning of Trials 1, 2, 3, and 4, respecti vely. Milk production was greater (P = .01) for ewes nursing twins tha n for those nursing singles at d 4 and 14 in Trial 1. In Trials 2, 3, and 4, all ewes had similar (P > .18) milk production. Ewe DMI during Trials 1 and 2 was greater (P < .05) for ewes nursing twin lambs than for those nursing singles. There was no difference (P > .88) in DMI be tween ewes with single and those with twin lambs in Trials 3 and 4. Fo rage DMI by twin lambs, expressed as either kilograms.ewe-1.day-1 or p ercentage of lamb BW, was higher (P = .01) than intake by single lambs in Trials 3 and 4. Equations predicting single lamb weight in Trial 3 showed that ewe DMI and MP were important variables, whereas in Trial 4 only lamb DMI was important in determining lamb weight at the concl usion of the trial. Correlations for twin lamb variables failed to con firm the relationships noted with the single lamb data. Lamb DMI accou nted for 37 and 66% of the variation in single lamb BW for Trials 3 an d 4, respectively. Results demonstrate the importance of forage intake by suckling single lambs on weaning weight.