- 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.