Effects of Pasture vs. Drylot Flushing on Ewe Body Weight Change and Number of Lambs Born

Abstract

Flushing is the practice of increasing nutrient intake before and during breeding in order to increase ovulation and ultimately the number of lambs born (NLB). Although extensive research has investigated the impact of different feeds and feeding strategies on the flushing response, literature addressing the impacts of environment on flushing is limited. Generalized linear mixed models (GLMM) were used to evaluate the responses of ewes to flushing treatments. A two-year study using two breeds of white-faced ewes was conducted at Montana State University’s Fort Ellis Experiment Station near Bozeman, MT. Two flushing trials were conducted to evaluate NLB per ewe, and BW (body weight) gain of ewes receiving 1 of 3 treatments: 1) control treatment; ad libitum access to pea-barley hay in drylot (CON), 2) ad libitum access to swathed pea-barley forage in paddocks (PAD), and 3) ad libitum access to swathed spring wheat straw in paddocks with 0.45 kg of supplement∙ewe-1∙d-1 (WHT). Trial 1 (28 d) evaluated yearling Targhee ewes and Trial 2 (14 d) evaluated mature Rambouillet ewes. For Trials 1 and 2, ADG (average daily gain), BW gain, lambing date, and NLB did not differ among treatments (P > 0.10). However, BW gain of ewes in PAD treatments was more variable than ewes in CON and WHT treatments for both Trials. Similar responses by ewes to feeding treatments suggest swath grazing as a viable flushing strategy to reduce inputs while maintaining high productivity.