great lakes dairy sheep symposium - the Department of Animal ...

EFFECT OF SUPPLEMENTATION AND STAGE OF LACTATION ON
PERFORMANCE OF GRAZING DAIRY EWES
Claire M. Mikolayunas 1,2 , David L. Thomas 1 , Kenneth A. Albrecht 2 , David K. Combs 3 , and
Yves M. Berger 4
1 Department of Animal Sciences, 2 Department of Agronomy, 3 Department of Dairy
Science, 4 Spooner Agricultural Research Station, University of Wisconsin-Madison,
Madison, Wisconsin, USA
Summary
A study was conducted in the summer of 2005 to determine the effect of stage of lactation
and supplementation on the performance of dairy ewes grazing kura clover-orchardgrass
pastures. Fifty-six three-yr-old ewes in early (21 ± 10 d in milk (DIM)) or late (136 ± 9 DIM)
lactation and were fed 0 or 0.80 kg DM/d of supplement (18 % CP mixture of corn and a high
protein pellet) in a 2 x 2 factorial arrangement of treatments. Average daily milk production and
daily milk protein percentage was higher in early lactation ewes than late lactation ewes (1.74 vs.
1.21 kg/d and 5.02 vs. 4.86 %, respectively). Supplemented ewes had higher average daily 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. Trial milk urea nitrogen (MUN) levels in all treatments (18 to 34 mg/dl)
tended to be higher than recommended levels for sheep (14 to 22 mg/dl), indicating an excess of
protein intake. This can be explained by high quality pastures, which ranged in crude protein
from 16 to 30 %. Based on estimates of dry matter intake using the external marker titanium
dioxide and the internal marker acid detergent lignin, there was no significant difference in
pasture dry matter intake between supplementation or stage of lactation treatments.
Background
The United States dairy sheep industry has grown over the past 25 years and in 2003 there
were approximately 75 farms in North America producing over 1.5 million kg of sheep milk
annually (Thomas, 2004). Despite this growth, the United States imported 33.2 million kg of
sheep milk cheese worth over $184 million in 2004 (FAO, 2006), indicating room for the
domestic market to expand.
The United States dairy sheep industry has developed in two main regions, New England and
the Upper Midwest, both well suited to pasture production. The development of flocks in these
areas may be attributed to the sheep’s ability to effectively utilize improved pasture along with a
market and infrastructure for artisan cheeses and sheep-milk products. Since dairy sheep are
relatively new to the United States, information regarding supplementation on pasture and
pasture utilization remains inadequate. While supplementation had a positive effect on milk
production of grazing lactating cows (Reis and Combs, 2000) and commercial sheep (D’Urso et
al., 1993), little information is available regarding the supplementation of dairy sheep on high
quality, temperate pastures. In a study of nursing ewes receiving low or high levels of
supplementation while grazing, lamb growth was greater when dam supplementation was high
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