Effects of supplementation and stage of lactation on performance of grazing dairy ewes.
The majority of dairy sheep in the world are fed pasture and supplemental grain during lactation; however, no trials have reported the effects of supplementation of dairy ewes grazing improved pastures in North America. In trial 1, 56 three-year-old grazing dairy ewes in early [21 +/- 10 d in milk (DIM)] or late (136 +/- 9 DIM) lactation were fed 0 or 0.82 kg of dry matter/d per ewe of supplement (16.5% crude protein mixture of corn and a soybean meal-based high-protein pellet) in a 2 x 2 factorial arrangement of treatments. There were no significant interactions between stage of lactation and supplementation treatments. Average test-day milk production was higher in early-lactation ewes than in late-lactation ewes (1.74 vs. 1.21 kg/d, respectively). Although test-day milk protein percentage was higher in late-lactation ewes than in early-lactation ewes (5.02 vs. 4.86%, respectively), there was no difference in milk fat percentage between stages of lactation. Supplemented ewes had higher milk production (1.59 vs. 1.36 kg/d, respectively), lower milk fat percentage (5.75 vs. 6.00%, respectively), and lower milk protein percentage (4.84 vs. 5.04%, respectively) than unsupplemented ewes. Milk urea N levels were similar between the 2 stages of lactation and between the 2 supplementation treatments and were above recommended levels for dairy sheep, indicating an excess intake or inefficient utilization of protein for both supplementation treatments. In trial 2, 96 two-, three-, and four-year-old grazing dairy ewes in midlactation (112 +/- 21 DIM) were randomly assigned to 4 treatments of 0, 0.41, 0.82, or 1.24 kg of dry matter/d per ewe of whole corn. Average test-day milk production increased linearly and milk fat percentage decreased quadratically with increasing amounts of corn supplementation. Milk protein yield increased linearly, and milk urea N levels decreased quadratically with increasing amounts of corn supplementation, suggesting an improvement in the utilization of pasture protein with increasing dietary energy intake.
Mikolayunas
C M
CM
Department of Animal Sciences, University of Wisconsin-Madison, Madison 53706, USA. mikolayunas@wisc.edu
Thomas
D L
DL
Albrecht
K A
KA
Combs
D K
DK
Berger
Y M
YM
Eckerman
S R
SR
D000821:Animal Feed / Q000032:analysis; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001824:Body Constitution / Q000502:physiology; D001835:Body Weight / Q000502:physiology; D003612:Dairying / Q000191:economics / Q000379:methods; D004044:Dietary Proteins / Q000378:metabolism; D019587:Dietary Supplements; D005223:Fats / Q000032:analysis; D005260:Female; D007774:Lactation / Q000502:physiology*; D008892:Milk / Q000737:chemistry* / Q000378:metabolism; D008894:Milk Proteins / Q000032:analysis; D009584:Nitrogen / Q000032:analysis; D011897:Random Allocation; D012756:Sheep / Q000502:physiology*; D013025:Glycine max / Q000378:metabolism; D013997:Time Factors; D014508:Urea / Q000032:analysis; D003313:Zea mays / Q000378:metabolism
D004044:Dietary Proteins; D005223:Fats; D008894:Milk Proteins; D014508:Urea; D009584:Nitrogen