The effects of alternative weaning strategies on lamb health and performance

Two experiments were conducted to determine the effects of weaning age on lamb growth and the severity of parasitic infection in grazing lambs. All lambs were fed in a feedlot until they reached a set marketable weight after their allocated grazing period. In experiment 1, 48 Hampshire × Dorset and Suffolk × Dorset crossbred lambs and 24 Dorset × Suffolk and Dorset × Hampshire crossbred ewes were placed into one of two weaning treatments for 63 days: Pasture control (PC): lambs weaned early at 60 days of age and placed on pasture and Ewe (E): Lambs placed on pasture at 60 days of age with ewe and weaned at approximately 123 days of age. The E lambs had a greater average final body weight, total ADG, and PCV value on day 63 compared to PC lambs during the grazing period (P < 0.05). In the feedlot, E lambs spent fewer days in the feedlot to reach market weight and had a greater overall ADG with PC lambs demonstrating a greater G:F and total DMI (P < 0.05). In experiment 2, a total of 72 crossbred lambs and 27 crossbred ewes were placed into one of four weaning treatments for 56 days: Pasture control (PC). Ewe (E): lambs weaned at approximately 116 days of age. Social facilitator (SF): lambs weaned at 60 days of age and placed on pasture with non-lactating, non-related ewes. Feedlot control (FC): lambs weaned at 60 days of age and placed in a research feedlot facility. Feedlot control lambs were not re-exposed to parasites after the initiation of the experiment and therefore included as an industry standard control. The E lambs demonstrated greater BW from day 42 to the end of the grazing period and FC lambs had the lowest BW from day 7 to day 28 and a greater ADG on day 56 of the grazing period (P < 0.05). The E and FC lambs also demonstrated a smaller difference in change in PCV values from day 28 to the end of the grazing period (P < 0.05). In the feedlot, E lambs required less total weight gain and had lower DMI compared to all other treatments to reach market weight (P < 0.05). The FC lambs had a greater total weight gain, DMI, and G:F compared to all other treatments (P < 0.05). The results from these two experiments demonstrate that extending the weaning age of lambs beyond 60 days of age in pasture-based systems can be beneficial from an animal health standpoint and requires less harvested grain in the feedlot to reach a market appropriate endpoint.