Graduate Thesis Or Dissertation
 

Effects of body condition and pre-lambing supplementation on ewe productivity

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  • A series of trials was conducted with Polypay (P), Coopworth (CP), Hampshire (H), and crossbred ewes over a two year period at three locations to assess the effects of ewe body condition and pre-lambing supplementation on ewe productivity. Supplementation trials were conducted at all three locations in Year 1 using P (OSU), CP (Farm 1), and crossbred ewes (Farm 2), and at OSU in Year 2 using P ewes. Supplementation consisted of one pound of whole corn daily in addition to the routine ration being fed to the controls. Supplementation began four weeks prior to lambing and continued to parturition. Body condition trials were conducted concurrently at OSU using CP, H, and crossbred ewes in the first year and CP ewes in the second year. A body condition trial was also conducted at Farm 1 (CP ewes) in the second year. At OSU, Polypay ewes were mated to CP, P, and H rams, CP ewes were mated to CP and H rams, and H ewes were mated to H rams. On the commercial farms, CP ewes (Farm 1) were mated to CP rams, and crossbred ewes (Farm 2) were mated to Suffolk rams. Ewes in supplementation trials were condition scored on a five point scale(1=very thin; 5=very fat)at the time of allocation to treatments six weeks pre-lambing, and ewes in all trials were scored one week prior to lambing. In addition, in Year 2 P and CP ewes at OSU were scored and weighed at mating, post-mating, mid-gestation, pre-lambing, and weaning. Production traits recorded included litter size at birth, total weight of lamb born (TWB), lamb survival, and individual lamb weaning weights (WWT). The various components were combined to calculate total weight of lamb weaned (TWW) by each ewe as the measure of total lamb production. In most trials, higher ewe body condition score pre-lambing (CSL) was associated with heavier TWW. The heavier TWW was the result of both increased lamb survival and heavier individual lamb WWT. Supplementation increased both CSL and subsequent TWW; the increase in TWW was accounted for entirely through improved CSL. The response to supplementation was not consistent over ewe genotypes; crossbred ewes showed a greater increase in CSL than purebred ewes, and likewise a greater response in TWW. While supplementation increased ewe productivity, a comparison of control vs supplemented ewes which were at the same body condition prelambing (CSL = 3.0) indicated that ewes which were previously thin did not perform as well as ewes which had been maintained in good condition throughout gestation. While supplementation raised their CSL to the same level, their lambs exhibited both lower survival and lighter WWT. Comparison of the expense of supplementation with the increased TWW indicated a feed cost of about $.30 per extra pound of lamb weaned. At typical lamb market prices of $.60/lb, identification and supplementation of thin ewes pre-lambing would be a profitable management strategy for sheep producers.
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