MATERNAL INGESTION OF LOCOWEED. III. EFFECTS ON LAMB BEHAVIOUR AT BIRTH

Authors: Pfister, James; DAVIDSON, T - CAMPBELL SCIENTIFIC; Panter, Kip; CHENEY, C - UTAH STATE UNIVERSITY; Molyneux, Russell

Submitted to: Small Ruminant Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/12/2005
Publication Date: 7/1/2005
Citation: Pfister, J.A., Davidson, T.W., Panter, K.E., Cheney, C.D., Molyneux, R.J. 2005. Maternal ingestion of locoweed. III. Effects on lamb behaviour at birth. Small Ruminant Research, 65:70-78.

Interpretive Summary: Locoweeds (Oxytropis and Astragalus spp.) are toxic plants found throughout the western U.S. and in other parts of the world. Livestock that eat locoweed develop behavioral abnormalities and are often fatally poisoned. When pregnant animals give birth, the period immediately after birth is critical for formation of a bond between mother and offspring, and for sucking to occur. The objective of this study was to determine if feeding of locoweed to pregnant ewes during days 100-130 of gestation would affect lamb behavior shortly after birth. Twenty yearling Columbia-Targhee ewes were divided into two treatment groups: loco ewes fed a 10% locoweed (Oxytropis sericea) pellet; control ewes were fed alfalfa pellets. Feeding locoweed to pregnant ewes had significant negative effects on newborn lambs. These loco lambs were slower to stand compared to control lambs. Further, none of the loco lambs were able to nurse successfully by 120 min after birth. The lambs born to ewes fed locoweed performed poorly on a battery of behavioral tests compared to normal lambs. Lambs from mothers given locoweed during pregnancy were behaviorally impaired at birth, and they would not have survived without human intervention.

Technical Abstract: Locoweed (Oxytropis sericea) is a toxic plant commonly found on rangelands in the western United States. The locoweed toxin is an indolizidine alkaloid, swainsonine, that causes neurological and systemic damage. The objective of this study was to determine if feeding of locoweed to pregnant ewes during days 100-130 of gestation would affect lamb behaviour shortly after birth. Twenty yearling nulliparous Columbia-Targhee ewes were divided into two treatment groups: loco ewes fed a 10% locoweed (Oxytropis sericea) pellet; control ewes were fed alfalfa pellets. Locoweed pellets contained 0.01 mg/g swainsonine with a mean consumption of 0.32 mg swainsonine ' kg-1 ' day-1 ' ewe-1. Lambs from the two groups did not differ in birth weight (P = 0.35), although single lambs had higher (P = 0.001) birth weights than did twin lambs (5.6 vs. 4.2 kg, respectively). Four control ewes had live twins whereas no loco ewes had live twins. Loco lambs were slower (P = 0.004) in latency from birth to first successful standing event compared to control lambs (65 vs. 22 min, respectively). None of the loco lambs successfully nursed their dams up to 120 min post partum, whereas control lambs all sucked successfully at 35 min (P = 0.0004). Loco lambs had slower (P = 0.0009) times ('=164 vs. 11 sec, respectively) through a progressive maze on days 2, 4, and 6 compared to control lambs. Loco lambs were also much slower (P = 0.002) to reach their dams during a barrier test at 12 hours post partum compared to controls (193 vs. 42 sec, respectively). Control lambs discriminated their dams at 12 hours post partum whereas most loco lambs did not. In this same test, control lambs spent a higher percentage (P = 0.03) of their time in close proximity to their dam (' = 53%) compared to loco lambs (' = 19%). Lambs exposed to locoweed in utero for 30 days were intoxicated at birth. Lambs born to loco ewes showed impairments in their behavior and appeared to demonstrate a weakened maternal infant bonding. Loco lambs would not have survived at birth without human intervention to assist in helping these lambs to suck.