Brady Campbell, Program Coordinator, OSU Sheep Team
As we approach the winter months, I find it timely to discuss what types of feedstuffs are available to feed gestating ewes. Last fall I published a summary from Radunz and others (2011) that covered the effects of winter feeding systems on ewe performance which can be found by clicking this link. For those not able to access the link, three different diets were fed to gestating ewes during the last 90 days of gestation which consisted of either forage (haylage), grain (limit fed corn), or by-products (limit fed dried distillers grains). After birth, all ewes were fed the same lactation diet.
From an economic perspective, feeding by-products proved to be roughly $0.01/head/day cheaper than grain and forage diets. Forage fed ewes had a lower body condition score during the latter portion of pregnancy to birth when compared to grain and by-product fed ewes. At weaning (60 days of age), ewes fed by-products had a greater body condition score when compared to grain and forage fed ewes. Lambs born from grain and by-product fed ewes were heavier (13.3 lbs. and 13.5 lbs.) than forage fed ewes (12.0 lbs.). Overall, there was no effect on ewe milk yield or quality. At weaning, there was no difference in lamb body weight.
By the looks of the summary above, feeding by-products to ewes during gestation seems to be well worth it. Ewes on this type of gestation diet remain in good condition, give birth to large lambs, and the diet itself is cheaper when compared to grain and forage diets. However, we cannot let our train of thought end here. Thinking beyond the ewe, how do these three different types of gestation diets effect the growth, performance, and carcass composition of lambs during the finishing period? Would those lambs from by-product fed ewes perform better than the others just as their mothers did? To find out, Radunz and others conducted and additional experiment investigating just that.
Upon weaning, lambs from the previously summarized experiment were placed into a feedlot and fed a common high concentrate diet. Lambs were harvested individually when they had roughly 0.24 in. of back fat over the 12th rib as determined by manual palpation.
As mentioned above, weaning weight did not differ between groups; however, final harvest weights differed based upon ewe gestational diet whereas lambs from by-product fed ewes had the heaviest weight (127.9 lbs.), lambs from grain fed ewes were intermediate (121.0 lbs.), and lambs from forage fed ewes were the lightest (114.4 lbs.).
At the conclusion of all harvests, all carcasses had similar hot carcass weights. However, dressing percentage ((carcass weight ÷ live weight) x 100) was greater for lambs from ewes fed grain and forage diets (50.1% and 49.9%) as compared to the by-product diet (48.6%).
Due to the manner in which lambs were removed from trial, there was no difference in back fat among treatments. There was a difference in loin eye area (an indication of overall muscling); whereas lambs from grain fed ewes had the largest loin eye area (2.53 in.2), with lambs from by-product fed ewes had the smallest loin eye area (2.26 in.2), and lambs from forage fed ewes were intermediate (2.40 in.2). The proportion of internal or wasteful fat tended to be greatest to smallest in lambs from ewes fed by-products (7.10%), grain (6.30%), and forage diets (5.95%). In calculating the overall value of lamb carcasses, lambs from ewes fed by-products had a boneless trimmed retail cut percentage that was less (48.6%) than lambs from grain or forage fed ewes (49.3% and 49.5%).
To wrap this series of experiments up, while evaluating lamb feedlot performance alone, the data from the feedlot phase shows that ewe gestation diet did have an effect on lamb performance and carcass composition. Although lambs from ewes fed by-product diets were heavier in weight at harvest, these lambs also had the greatest amount of internal fat in conjunction with the smallest loin eyes. Furthermore, the lambs from by-product fed ewes had the lowest percentage of boneless trimmed retail cuts.
However, it cannot go un-noticed that during gestation, by-product fed ewes remained in the best body condition, had the heaviest lamb birth weights, and overall cost less on a per head/day basis.
At the end of the day, it is ultimately the producer’s decision upon what gestation diet they will choose. This decision may be dependent upon resource availability, labor involved in feeding each diet, whether the lambs are retained on-farm or not, and if lambs are sold on a premium or value based system to name a few.
With that, I challenge you to think about all of your management decisions a bit more critically. Everything that you do, even if it is prior to the lambs being born, can potentially affect the outcome of your lamb crop 6 months later. Happy feeding and good luck with the upcoming lambing season!
Radunz, A. E., F. L. Fluharty, I. Susin, T. L. Felix, H. N. Zerby, and S. C. Loerch. 2011. Winter-feeding systems for gestating sheep II. Effects on feedlot performance, glucose tolerance, and carcass composition of lamb progeny. J. Anim. Sci. 89: 478-488.