Overview of project: Our question was: “What is the optimal level of concentrate supplementation needed for lactating dairy sheep and goats grazing intensively managed pastures?” After three seasons of careful study our conclusion for dairy sheep is that they are able to meet their lactation requirements from well managed high quality pastures with little or no concentrate supplementation. Dairy goats do respond with increased milk yield if given supplementation. A secondary finding was that a concentrate containing a source of highly fermentable fiber, such as soybean hulls, reduces metabolic problems to negligible levels. Both these findings resulted in significant economic savings for the farm cooperators.
To determine the optimum level of a formulated complete concentrate supplement to feed high yielding dairy sheep and goats grazing intensively managed pastures.
The project used a team approach involving farmers, researchers, UVM and UNH Cooperative Extension, and NRCS personnel. The project was conducted at two on-farm sites, Major Farm (dairy sheep), Westminster, VT and Quarrier Farm (dairy goats), Acworth, NH. Dr. James Welch, UVM, developed the experimental design.
In year one, we used a Randomized Complete Block design. i.e. All available animals were identified according to previous milk production, genetic potential for milk production, number of offspring nursed, weight and age. Animals were assigned to blocks of three according to the above criteria. Animals within blocks were randomly assigned to treatments 1, 2, or 3. Each animal was identified by ear tag or tattoo and by a colored leg band for quick ID at milking.
The three groups received different levels a of nutritionally complete supplement designed by Dr. Doug Hogue, Cornell University. This supplement was designed utilizing the current information available on feeding high milk producing sheep and goats and utilized readily available feedstuffs. The resulting supplement was a 14-16% protein, high-energy dairy pellet with 20% soybean hulls as a source of highly fermentable fiber. The supplement was balanced for vitamins and minerals for each species. The National Research Council’s Nutrient Requirements of Sheep, 6th edition, 1985 and Nutrient Requirements of Goats, 1981, were used as guidelines to determine the nutrient requirement baseline on which the level of supplementation was determined.
All three groups were grazed together and allowed unlimited consumption of the same high quality pasture. At milking each animal received the supplement according to which of the three groups it had been assigned. After milking the animals returned to a single group. Animals received new pasture after every milking. All animals received care at the best management level throughout the life of the project. Animal care was monitored weekly by Extension Specialists or a licensed veterinarian.
In years two and three, we redesigned the experiments based on our analysis of the previous year’s data.
The following measurements were taken in each of the three years of the project:
Weight – all animals were weighed at the beginning of the last trimester of pregnancy, within 1-2 days postpartum and at the beginning and end of each experiment period.
Milk – milk was weighed and analyzed regularly during each experiment for fat, protein, milk urea nitrogen (MUN), and somatic cell count.
Pasture- pasture quantity and quality was measured/sampled and recorded daily during each testing period. A rising plate pasture meter designed and made in New Zealand was used for quantity measurement. Quality was analyzed at the Dairy One forage-testing lab, Ithaca, NY.
Health – animal health and overall condition was assessed by a licensed veterinarian at the beginning of the last trimester, and at the beginning and end of each experiment. A condition score of 1 to 5 was assigned each animal at each of these times. Health treatments were administered under the direction of the veterinarian.
An intern on each farm assisted in taking these measurements and in recording and compiling the data. All milk production data compiled was statistically analyzed.
For the dairy sheep: in year one, following the methods detailed above, we compared three levels of concentrate feeding, .5 lb per ewe per day, 1.5 lbs per ewe per day, and 2.5 lbs per ewe per day. We found that there were no significant differences in milk yield or milk composition, or animal condition score between the three treatments.
Although not significantly different, the average milk yield and milk composition of the group fed 2.5 lbs per day was actually lower than the other two groups. We reasoned this was the result of the sheep reducing their consumption of pasture in favor of the supplement. Milk yield was reduced because the pasture was more nutritious than the supplement.
Having concluded that there was no reason for supplementing above the 1.5 level, in year two we used a “switch-back” design to compare .5 lbs per ewe per day and 1.5 lbs per ewe per day. Again we found no significant difference.
In year three, we again randomly divided the flock into groups and fed one group .5 lbs per ewe per day, and the other group 1.5 lbs per ewe per day. However, we kept the groups on those treatments for the entire lactation with no “switch-back”.
Again, there were “no significant differences”.
Our conclusion was that dairy sheep on well managed pastures needed no more than .5 lbs per ewe per day concentrate supplementation. We didn’t try feeding no concentrate supplementation because David Major felt that .5lbs per ewe per day was the minimum practical level of concentrate feeding necessary to attract the sheep into the milking parlor.
We used similar methods for the goats, although the feeding levels were higher at 1., 3.0 and 5.0 lbs per doe per day. We found that the does responded to increased concentrate. Our conclusion/recommendation for dairy goats is to feed concentrate at a ratio of 1 lb of concentrate for each 3 lbs of milk yield.
In year three of the goat study, we compared the concentrate with fermentable fiber with a concentrate exactly the same except without fermentable fiber.. This comparison was done during lactation only. The results showed no significant difference in milk yield, milk composition, or animal condition score between the two formulations. The Quarriers did observe that by feeding the concentrate with fermentable fiber the last 4-6 weeks of gestation, they significantly reduced what had been a fairly high incidence of ketosis . For them, this was the most important economic benefit of this project.
Other results from this project include:
(1) a comprehensive data set on the nutritive quality of well managed pasture collected from the same pastures over three consecutive pasture seasons. These data show levels (on a dry matter basis) of crude protein averaging over 20% and as high as 28%, of TDN averaging over 60% and as high as 67%, and relative feed values averaging over 110 and as high as 159.
(2) A comprehensive data set on sheep and goat milk yield and milk composition(including fat, protein, MUN, SCC) collected from a significant number of animals(100 ewes, 60 does) and over three consecutive lactation periods. The sheep milk data are especially useful because the sheep dairy industry in North America is so young that data such as these collected under controlled conditions are not readily available.
(3) A clear demonstration that high quality data ,that can serve as a solid basis for management recommendations, can be successfully generated from on-farm experiments through the collaboration of university researchers, Extension and USDA agency staff, dedicated farmers, and SARE funding support.
Techniques such as pasture walks and farm visits (see photos in appendices) were used throughout the three years to share the objective, methods, and preliminary findings with producers, extension and other ag agency staff.
We presented our preliminary findings to New England Extension Dairy and Livestock
staff on October 15,2001
Carol Delaney published updates on the project in the “Small Ruminant Dairy Newsletter”.
We presented the results from the first year’s studies at the 5th Great Lakes Dairy Sheep Symposium in November 1999.
We will present the entire project and its findings at the 8th Great Lakes Dairy Sheep Symposium at Cornell University in November 2002.
We also will publish an article describing the project and our findings in one or two national sheep magazines, the Small Ruminant Dairy Newsletter, and the British Dairy Sheep Newsletter.
Impacts of Results/Outcomes
The primary impact we were after was the answer to our question, “what is the optimal level of concentrate supplementation needed for lactating sheep and goats grazing intensively managed pastures?” As detailed above, we were very successful in achieving that impact.
Other impacts from our project include:
(1) Cost savings to dairy sheep producers who adopt our results of approximately $13/ewe per lactation (see detail in next section of this report).
(2) Most dairy sheep and many goat producers in the VT-NH-MA area now use the concentrate formulated by Dr. Hogue for this project.
(3) David Major credits his involvement in the project as the primary reason his per ewe milk yield increased over 50% during the three years of the project.
(4) The camaraderie that developed between project participants was very valuable and was sited by each participant as a personal impact of the project.
The results from the project allowed us to do a very straightforward economic analysis.
For the dairy sheep producer, the economic benefit is substantial. Previous to our work, dairy sheep producers were typically feeding 1.5 – 2.0 lbs of supplement/ewe/day in the form of whole grain or pelleted concentrate. Also, scouring and other symptoms of acidosis were commonly seen.
Our results point to two economic benefits for dairy sheep producers:
(1) Our recommendation of feeding .5lbs of supplement/ewe/day rather than 1.5 -2.0 lbs/ewe/day saves the cost of 1.0 – 1.5 lbs supplement/ewe/day. At an average cost of $.09/lb, times an average 150 day lactation, gives a savings of $13.50 – $20.25 per ewe. Multiply this times the number of ewes in a flock(in Major’s case 100ewes), and the savings are very substantial.
(2) The other benefit is the improvement in milk production. David Major reported a 50% increase in milk production over the three years of the project (see letter in appendices). He credits most of this increase to improvement in the metabolic health of his ewes due to the proper balancing of their pasture diet with a concentrate supplement that contained 20% fermentable fiber. If we credited the project with just a 20% improvement in milk production, then the increase in income would be calculated as 20% times 3lbs/milk/ewe/day times 150 days times the price of milk at $.70/lb equals an increased income of $63/ewe/lactation.
The economic benefits to a goat producer were not as direct. Our work did not point out any savings in feed costs, however, the generation of data to substantiate the recommendation of feeding supplement at the ratio of 1 lb of supplement to every 3 lbs of milk will likely result in economic benefits due to more accurate feeding of supplement. The Quarriers also reported significant increases in milk production over the three years of the project which they also credit to the improvement in the metabolic health of their does(see letter in appendices). The Quarrier’s also reported that the use of Dr. Hogue’s concentrate formula reduced a serious ketosis problem in their herd.
Areas needing additional study
We suggest the following as two areas needing further study:
(1) One more year of study to see whether milking sheep grazing high quality pastures need any concentrate supplement at all. Results from our work suggest that supplements may not be necessary.
(2) A study of the effect of growth rate of replacement ewe lambs and doe kids on their udder development and future milk production. Research has indicated that rapid growth rate before puberty in dairy heifers reduces future milk production. We need to know if this same effect happens in sheep and goats and, if so, what is the optimum pre-puberty growth rate.