Abstract Our objective was to evaluate the effect of a daily intramuscular injection of adrenocorticotropic hormone 1-24 (ACTH24) in lactating ewes on ewe and lamb growth and plasma glucose concentration (PGC) during the lactation period, and lamb growth and PGC during the finishing period. This experiment was conducted using 25 lactating, crossbred ewes (n = 36) with single or twin lambs. Seven (±3) days postpartum (d 1 of the experiment), ewes were randomly divided into 10 pens with 2-3 ewes/pen with their lambs. Treatments were applied to ewes (saline, CON; n = 12 ewes and 19 lambs) or ACTH 1-2424 (0.44 µmol/kg body weight (BW); ACTH24; n = 13 ewes and 18 lambs) intramuscularly daily at 1100 for 15 d. Ewe and lamb BW were collected before feeding (65% concentrate, 35% forage) at 900 and blood samples were collected two hours post-injection on d 1, 8, and 15 of treatment. Lambs were weaned at 60 d of age. For the finishing phase, 36 lambs were arranged by dam treatment and lamb sex and sorted randomly into 12 pens with 2-4 lambs/pen and fed a diet containing 61% corn, 24% soyhulls, and 11% soybean meal. Lamb dry matter intake (DMI) was recorded daily, and BW was collected every 21 d during finishing. Blood samples were collected from the jugular vein at the beginning and end of the 63-d finishing period. Data were analyzed using a mixed model, pen as random effect, and treatment, sex, day, and their interactions as fixed effects. The model utilized repeated measures with compound symmetry. There were no differences (P ≥ 0.22, Table 1) in ewe BW, average daily gain (ADG), DMI, gain to feed ratio (G:F), PGC, and lamb BW during the lactation phase. There was a treatment × time interaction (P = 0.04, Table 1) for lamb PGC during the lactating phase; on d-1 ACTH24 lamb PGC was greater than CON lambs but were similar on d-8 and d-15. During the finishing phase, there was a treatment × time interaction for lamb BW (P 0.01, Table 1). Despite lambs beginning with similar BW, ACTH24 lambs were heavier than CON lambs on d-63 of finishing. There were no differences in lamb DMI or G:F (P ≥ 0.16, Table 1). There was a treatment × time × sex interaction for lamb PGC during the finishing period. Lamb PGC was similar for all the lambs at the start of finishing but on d-63 CON-ewes had a lesser concentration than CON-wethers. These results suggest that, under the current dose, ACTH 1-24 injections to lactating ewes improved lamb growth during finishing.
Tacuri-Vera et al. (Wed,) studied this question.