Progress 10/01/07 to 09/30/11
Outputs
OUTPUTS: Four major trials were conducted over the 4 yr of this project to investigate supplementation strategies and protein utilization for lactating dairy ewes. A previous trial with supplementation of 2 lb/d per ewe of a 16% CP diet suggested that excess protein was being fed, which resulted in poor protein efficiency and increased milk urea nitrogen (MUN) levels. In trial 1, 96 two-, three-, and four-year-old grazing dairy ewes in mid-lactation (112 days in milk) were randomly assigned to 4 treatments of 0, 1, 2, or 3 lb/d per ewe of whole corn. High-producing ruminants, like lactating dairy ewes, may increase their productivity if rumen undegraded protein (RUP) is added to rations already adequate in rumen degraded protein (RDP). In trial 2, three diets were formulated to provide similar energy concentrations and varying concentrations of RDP and RUP: 12% RDP and 4% RUP (12-4) included basal levels of RDP and RUP, 12% RDP and 6% RUP (12-6) included additional RUP, and 14% RDP and 4% RUP (14-4) included additional RDP. Diets were composed of alfalfa-timothy cubes, whole and ground corn, whole oats, dehulled soybean meal, and expeller soybean meal (SoyPlus, West Central Cooperative, Ralston, IA). Ewes were fed complete diets in pens. In the previous trial, dairy ewes were fed complete diets in confinement. However, dairy sheep production in the United States is primarily based on grazing mixed grass-legume pastures, which contain a high proportion of RDP. Two trials (Trials 3 and 4) were conducted to evaluate the effects of high-RUP protein supplementation and varying levels of legume in legume-grass forages on lactation performance. In Trial 3, a cut-and-carry trial, 16 multiparous dairy ewes in mid-lactation were randomly assigned 1 of 2 protein supplementation treatments, receiving either 0.0 or 0.66 lb. of a high-RUP protein supplement (Soy Pass, LignoTech USA Inc., Rothschild, WI) per day. Within supplementation treatment, ewes were full-fed freshly cut forage of varying percentages of orchardgrass:alfalfa dry matter: 25:75, 50:50, 75:25, and 100:0. In Trail 4, a grazing trial, 12 multiparous dairy ewes in mid lactation were randomly assigned to receive either 0.0 or 0.66 lb. of a high-RUP protein supplement (SoyPlus, West Central Cooperative, Ralston, IA) per day. Within supplementation treatments, ewes grazed paddocks that contained the following percentages of surface area of pure stands of orchardgrass:alfalfa: 50:50, 75:25, and 100:0. The results of these trials were presented to the scientific community through refereed papers published in the Journal of Dairy Science and to dairy sheep producers through presentations at the annual Spooner Sheep Dairy Day and the annual Great Lakes Dairy Sheep Symposium. PARTICIPANTS: Claire Mikolayunas - Ph.D. student, Department of Animal Sciences, UW-Madison; Louis Armentano - Professor, Department of Dairy Science, UW-Madison; David L. Thomas - Professor, Department of Animal Sciences, UW-Madison; Yves Berger - Researcher, Spooner Agricultural Research Station, UW-Madison TARGET AUDIENCES: Dairy Sheep Producers, Animal Sciences Extension Specialists, Ruminant Nutrition Researchers PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Trial 1: Average test-day milk production increased, milk fat percentage decreased, and milk protein percentage was not changed with increasing amounts of corn supplementation. MUN levels for all four groups were within the range suggested for dairy sheep and decreased with increasing amounts of corn supplementation. This suggested that protein levels in the high quality legume-grass pasture were adequate for milk production in these ewes and utilization of pasture protein improved with increasing dietary energy intake from whole corn. Trial 2: There was no effect of dietary treatment on dry matter intake. The 18% crude protein diet with the high level of RDP (14-4) resulted in no more milk production than obtained with the 16% crude protein diet with a lower level of RDP and the same level of RUP (12-4). However, the 18% crude protein diet with the high level of RUP (12-6) increased (P < 0.01) milk yield over both the 14-4 and 12-4 diets. This is strong evidence for the inclusion of RDP in diets of lactating ewes. Milk urea N concentration was greater (P < 0.05) in the 14-4 diet and tended to be greater (P < 0.10) in the 12-6 diet compared with the 12-4 diet, indicating that the excretion of urea N in this study was more closely related to dietary crude protein concentration than to protein degradability. Trial 3: Supplementation with a high-RUP source tended to increase (P < 0.10) milk yield by 9%. Milk yield, milk protein yield, and milk urea nitrogen increased with increased percentage of alfalfa. Trial 4: Milk yield, milk protein yield, and milk urea nitrogen increased with increased percentage of alfalfa in the paddock. Major conclusions from this project are: 1) increased energy intake by ewes grazing high quality pastures high in protein (22 to 24%) will increase milk yield and the efficiency of protein utilization, 2) supplementing with a high-RUP protein source tended to increase milk yield even more, and 3) and increasing the proportion of alfalfa in the diet increased dry matter intake, milk yield, and protein yield of lactating dairy ewes fed or grazing fresh forage.
Publications
- Mikolayunas-Sandrock, C., L.E. Armentano, D.L. Thomas, and Y.M. Berger. 2009. Effect of protein degradability on milk production of dairy ewes. J. Dairy Sci. 92:4507-4513. Mikolayunas, C., D.L. Thomas, L.E. Armentano, and Y.M. Berger. 2011. Effect of rumen undegradable protein supplementation and fresh forage composition on nitrogen utilization of dairy ewes. J. Dairy Sci. 94:416-425.
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Progress 01/01/10 to 12/31/10
Outputs
OUTPUTS: Twelve, third-lactation dairy ewes in mid-lactation with similar milk production (2.32 kg/d) were randomly assigned to three groups of four ewes each. Groups were grazed on one of three dietary forage treatments, which were balanced for carryover effects and applied to ewes for 10-d periods in a 3 x 3 Latin Square. Forage treatments were paddocks containing the following proportions of surface area from pure stands of orchardgrass and alfalfa: 50% orchardgrass and 50% alfalfa (50), 75% orchardgrass and 25% alfalfa (75), and 100% orchardgrass (100). Forages were planted in monoculture strips, clipped to a height of 7.5 cm, and allowed 20-d of regrowth before the start of each grazing period. No plot was grazed more than once and the maximum age of forage regrowth was 30-d. Ewes were given fresh forage daily and paddock size was based on the residual from the previous day. Within each group, two ewes were randomly assigned to one of two supplementation treatments, receiving either 0 (NS) or 0.3 kg/d of SoyPlus (S), a source of rumen undegraded protein (RUP) fed in two equal feedings in the milking parlor. All ewes were milked twice daily (0700 and 1900 h) and had access to water and a free choice mineral-salt mixture. All ewes received 0.8 kg DM/d of whole corn, which was fed in equal portions at each milking. All ewes were dosed twice daily with a gelatin capsule containing 0.1 g of dotriacontane (C32) at 0700 and 1900 h for a total of 0.2 g dosed per d. The dosed alkanes were used as an external marker in order to estimate forage dry matter intake (DMI) and forage composition. Individual ewe milk yield was measured during the final 4 milkings of each treatment period using a graduated Waikato Goat Meter. Individual milk samples were analyzed for fat, protein, and milk urea nitrogen (MUN). Milk fat and protein percentages were measured using a CombiFoss 5000 and MUN was analyzed using a Foss FT6000. Milk fat yield and protein yield were calculated for each ewe from daily milk yield and fat and protein percentages. Ewes were weighed at the start of the first treatment period and during the final 2-d of each experimental period, and BW change during each period was calculated as initial BW minus final BW. The orchardgrass, alfalfa, and residual forage were sampled during the final 2-d of each treatment period. Orchardgrass and alfalfa were sampled by randomly tossing 2 quadrats (0.37m2) into an adjacent ungrazed, monoculture strip and harvesting the forage to a height of 2.5 cm. Pen residual forage was sampled by randomly tossing 2 quadrats into the grazed paddock and harvesting forage to 2.5 cm stubble height. Forage samples were weighed and dried in a forced-air oven at 37C until they reached a constant weight. Final DM was determined by drying samples overnight at 100C in a forced-air oven. All samples were analyzed for NDF, ADF, CP, and ash. Results of this trial were presented at the 4th Biennial Dairy Sheep Day, Spooner, WI in August 2009 and at the 15th Great Lakes Dairy Sheep Symposium, Albany, NY in November 2009. A journal article with the results of this trial is in press in the Journal of Dairy Science. PARTICIPANTS: Claire Mikolayunas - Ph.D. student, Department of Animal Sciences, UW-Madison; Louis Armentano - Professor, Department of Dairy Science, UW-Madison; David L. Thomas - Professor, Department of Animal Sciences, UW-Madison; Yves Berger - Researcher, Spooner Agricultural Research Station, UW-Madison TARGET AUDIENCES: Dairy Sheep Producers, Animal Sciences Extension Specialists, Ruminant Nutrition Researchers PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Forage DM on offer averaged 2.6, 3.1, and 3.3 kg DM/ewe/d for the 100, 75 and 50 treatments, respectively. There was no effect of supplementation or forage composition on BW; therefore the data are not presented. Based on analysis of dosed and naturally occurring alkanes, ewes in the grazing trial consumed diets with botanical composition similar to those offered. Orchardgrass accounted for 96.4, 73.0, and 59.3% of DMI in the 100, 75, and 50 treatments, respectively. Despite a numerical increase of 0.17 kg/d in milk yield in RUP-supplemented, the effect was not statistically significant, perhaps due to the experimental design, which gave more power to detecting an effect of forage composition than RUP supplementation. The mid-lactation ewes in our studies may not have had sufficient protein requirements to elicit a significant response to RUP supplementation, or the level of RUP supplementation may not have reached requirements. There was a tendency for forage composition to affect milk yield (P = 0.055), but across forage treatments there was a linear increase (P < 0.05) in milk yield as the proportion of orchardgrass decreased. However, there was no additional response in milk yield in going from 50 to 25 % orchardgrass (50 to 75% alfalfa). Based on literature values of RUP, dietary RUP (% of DM) was not affected by forage treatment. Therefore, increased milk yield from higher alfalfa intake likely resulted from increased DMI and CP intake, with little effect of RUP. Increasing the proportion of alfalfa increased (P < 0.05) milk protein yield. Increasing alfalfa increased milk protein yield by 25% or 19.7 g/d in 50 compared to 100. The increase in milk protein is likely due to increased availability of AA for milk protein production from increased alfalfa intake. Supplementation did not significantly affect MUN, but the supplemented group had a larger mean value than the unsupplemented group. Similar to milk protein yield, MUN increased linearly (P < 0.01) as the proportion of intake from alfalfa increased. Regression of MUN on CP (% of intake), as calculated from forage composition offered, had an R2 value of 0.45 for all ewes and 0.48 for unsupplemented ewes. Therefore, MUN may be used as an indicator of protein intake in ewes consuming grazed forage. Sheep milk was valued at $75.30/cwt in Wisconsin. Based on this price, RUP supplementation increased return/ewe by $0.28/d. If this effect is consistent throughout the 80 d period from mid-lactation to the end of lactation, a flock of 300 ewes may realize an increased gross return of $6,773 by supplementing an RUP source. Based on the current cost of SoyPlus ($0.328/kg or $297.90/ton), the total cost of supplementation of this flock during this 80-d period would be $2,364. This would lead to a net return of $4,408 over 80 d. Therefore, a positive economic return to producers may be realized with the supplementation of RUP if the increases in milk yield from RUP supplementation reported in this study are real.
Publications
- Mikolayunas, C., D.L. Thomas, L.E. Armentano, and Y.M. Berger. 2010. Effect of rumen undegradable protein supplementation and fresh forage composition on nitrogen utilization of dairy ewes. J. Dairy Sci. (In Press).
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Progress 01/01/09 to 12/31/09
Outputs
OUTPUTS: Sixteen, third-lactation dairy ewes in mid-lactation (104 DIM; SD = 8) with similar milk production (2.37 kg/d; SD = 0.22) were randomly assigned to eight pens of two ewes each. Pens were randomly assigned to one of two supplementation treatments, receiving either 0 (NS) or 0.3 kg/day Soy Pass (Borregaard LignoTech, LignoTech USA Inc., Rothschild, WI; S), a chemically derived source of rumen undegraded protein (RUP). Within each supplementation treatment, pens were assigned to one of four forage treatments. Forage treatments were composed of the following proportions of dry matter from orchardgrass and alfalfa: 25% orchardgrass and 75% alfalfa (25:75), 50% orchardgrass and 50% alfalfa (50:50), 75% orchardgrass and 25% alfalfa (75:25), and 100% orchardgrass (100:0). All pens were fed a 50:50 mixture of the two forages for a 5 day adaptation period before the trial began. Forages were clipped daily at 0600 h at a height of 5 cm above the soil surface using a walk behind, sickle bar mower (Jari Products Inc, Minneapolis, MN). Clipped forages were fed to ewes at 0800 and stored at 7 C until feeding again at 1100 and 1800 h. Multiple feedings per day were designed to imitate the grazing behavior of ewes. Forage DM was determined on day 2 and 7 of each experimental period by drying forages in 37 C forced-air oven until they reached a constant weight. As-fed forage amounts were calculated based on these DM determinations. Pens were fed ad libitum to allow 5% refusals. Forages were clipped to maintain similar stages of development. Dietary forage treatments were balanced for carryover and applied to pens for 10-day periods in a 4 x 4 Latin Square. All ewes were milked twice per day (0530 and 1700 h) and had access to water and a free choice mineral-salt mixture. All ewes received 0.4 kg DM/day of an equal mixture of whole corn and soyhulls in the milking parlor at each milking. Results of this trial were presented at the 4th Biennial Dairy Sheep Day, Spooner, WI in August 2009 and at the 15th Great Lakes Dairy Sheep Symposium, Albany, NY in November 2009. A journal article was published in 2009 in the Journal of Dairy Science on a trial conducted under this project in 2008. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
The CP content was lower for orchardgrass (10.8 to 15.2% CP) compared to the alfalfa (18.7 to 20.0% CP). While supplementation with 0.3 kg/day of Soy Pass had no effect on DMI, forage composition significantly affected DMI. Ewes consuming 100% orchardgrass consumed less (P < 0.05) than ewes fed 25:75 or 50:50 diets. Consistent with dietary treatments, CP intake and CP intake as a % of DM were linearly related (P < 0.01) to orchardgrass content of the diet. Ewes consuming Soy Pass had greater (P < 0.01) CP intake than ewes not supplemented with Soy Pass. The NDF content of the diet consumed was also linearly related to forage content: ewes offered more of the higher NDF forage (orchardgrass) consumed greater (P < 0.01) NDF than ewes consuming 25% orchardgrass. The 50:50, 75:25 and 100:0 treatments consumed diets greater than 38% NDF, the level recommended by Cannas (2002). Supplementing ewes with RUP increased (P < 0.10) milk production by 9%, representing a numerical increase of 0.16 kg/day. Increasing dietary alfalfa from 0 to 75% increased (P < 0.10) milk production by 12%, representing a numerical increase of 0.21 kg/day, emphasizing the importance of pasture quality in dairy sheep production. Milk fat and milk protein yield were not affected by RUP supplementation. Increasing alfalfa in the diet up to 75% increased milk protein yield by 15% or 12.8 g/d. Milk urea N (MUN) was greater (P < 0.05) in ewes consuming RUP. Supplementation of RUP increased milk and milk protein yield. This effect is likely due to increased supply of AA to the small intestine and the mammary gland, which supports both milk and milk protein production. This is particularly relevant to dairy sheep producers, since the majority of sheep milk is processed into cheese and protein and fat yield are important in determining cheese yield. Forage composition, and resulting CP intake, also affected milk, milk protein yield, and N utilization. Milk production increased as the proportion of alfalfa in the diet increased to 50%, but no benefit was observed above 50%.The excretion of urea, as indicated by MUN, was higher for ewes on high CP diets compared to ewes on low CP diets. The MUN results indicate that MUN level closely reflects CP intake, regardless of protein degradability. Increased milk yield may be realized by supplementing RUP to grazing dairy ewes and maintaining mixed grass-legume pastures with at least 50% legume.
Publications
- Mikolayunas-Sandrock, C., L.E. Armentano, D.L. Thomas, and Y.M. Berger. 2009. Effect of protein degradability on milk production of dairy ewes. J. Dairy Sci. 92:4507-4513.
- Mikolayunas, C.M., D.L. Thomas, and Y.M. Berger. 2009. Protein utilization in lactating dairy ewes. Proc. 15th Annual Great Lakes Dairy Sheep Symp., Albany, New York. University of Wisconsin-Madison, Dept. of Anim. Sci. pp. 59-77.
- Sandrock, Claire M., D.L. Thomas, and Y. M. Berger. 2009. Protein utilization in lactating dairy ewes. Proc. 4th Biennial Spooner Dairy Sheep Day, Dept. Animal Sci., Univ. of Wisconsin-Madison. pp. 11-29.
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Progress 01/01/08 to 12/31/08
Outputs
OUTPUTS: The objective of this experiment is to determine the effects of protein degradability of dairy sheep diets on milk yield and protein utilization across two levels of milk production. Three diets were formulated to provide varying concentrations of rumen-degradable protein (RDP) and rumen-undegradable protein (RUP): 12% RDP and 4% RUP (12-4) included basal levels of RDP and RUP, 12% RDP and 6% RUP (12-6) included additional RUP, and 14% RDP and 4% RUP (14-4) included additional RUP. All diets had similar energy concentration. Eighteen multiparous dairy ewes in mid-lactation were divided by milk yield (low and high) into two blocks of 9 ewes each and randomly assigned within block (low and high) to 3 pens of 3 ewes each. Dietary treatments were arranged in a 3 x 3 Latin Square within each block and applied to pens for 14-d periods. We hypothesized that pens consuming high RUP diets (12-6) would produce more milk and milk protein than the basal diet (12-4) and pens consuming high RDP diets (14-4) would not produce more milk than the basal diet (12-4). Ewes in the high milk yield square consumed more dry matter and produced more milk, milk fat, and milk protein than ewes in the low milk yield square. There was no effect of dietary treatment on dry matter intake. Across both levels of milk production, 12-6 increased milk yield, milk fat yield, and milk protein yield by 14, 12, and 13% respectively compared to 14-4 and by 15, 15, and 14% respectively compared to 12-4. Gross N efficiency (intake protein N / milk protein N) was 11 and 15% greater in 12-6 and 12-4, respectively, compared to 14-4. Milk urea N concentration was greater for the 12-6 and 14-4 treatments compared to the 12-4 treatment (26.33 and 27.39 vs. 23.43 mg/dL, respectively), indicating that the excretion of urea N in this study was more related to dietary crude protein concentration than protein degradability. An oral presentation of this study was made at the Joint Annual Meeting of the American Society of Animal Science and the American Dairy Science Association in Indianapolis, IN in July 2008. A paper has been submitted to the Journal of Dairy Sciences for possible publication. PARTICIPANTS: Claire Mikolayunas-Sandrock - Ph.D. candidate; L.E. Armentano - Professor of Dairy Science; D.L. Thomas - Professor of Animal Science; Y.M. Berger - Researcher TARGET AUDIENCES: Dariy sheep producers, dairy ruminant nutrition scientists PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Supplementation of RUP increased milk, milk protein, and milk fat production in both high and low milk production dairy ewes. This information is relevant to dairy sheep producers, since the majority of sheep milk is processed into cheese and protein and fat yield are important in determining cheese yield. Gross N efficiency, or the capture of intake protein in milk protein, was greater in low RDP diets. The excretion of urea, as indicated by MUN, was higher for ewes on high CP diets compared to ewes on low CP diets. For dairy sheep producers, the benefits of balancing RUP and RDP in lactation diets would be increased milk, milk protein, and milk fat yields and improved N utilization.
Publications
- Mikolayunas, C.M., L.E. Armentano, and D.L. Thomas. 2008. Effect of protein degradability on milk production of dairy ewes. J. Anim. Sci. 86(E-Suppl. 2) and J. Dairy Sci. 91(E-Suppl. 1):396. (Accessed at: http://adsa.asas.org/meetings/2008/abstracts/0394.PDF).
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