MILK YIELD, COMPOSITION, NUTRITIVE AND TECHNOLOGICAL VALUES FROM EWES FED DRIED DISTILLERS’ WHEAT GRAINS WITH SOLUBLES (DDGSw)

The aims of this study were to evaluate the effects of lactating dairy ewes diets supplementing with different vegetable protein sources (sunflower meal (SFM) vs. dried distillers’ wheat grains with solubles (DDGSw)) at the pick of lactation (27 – 72 lactating day). The experiment was carried out with sixteen lactating dairy ewes, Bulgarian Dairy Synthetic Population (BDSP) in 60-d feeding trial (7-d preparatory + 45-d experimental + 8-d closing periods). Animals were allotted randomly (by age, lactation, milk yield, % milk fat, % milk protein) into two dietary treatments: 1./ a SFMbased control diet (CD), and 2./ DDGSwbased experimental diet (ED). Diets were isonitrogenous, isofibrogenous, isocaloric and equal in protein truly digestible in the small intestines (PDI), calcium (Ca) and phosphorus (P). Compared with the CD, supplementation with DDGSw decreased (p<0.001) the average daily milk yield (5.8 %) and 6.5 % fat-corrected milk (6.8 %). There’re no significant differences in milk composition between treatments (CD and ED): solids non-fat (SNF) + 0.8; dry matter (DM) + 0.1 %; fat content of milk (MF) 1.1 and milk protein (MP) content + 0.4 % per sheep for ED, compared with CD. DDGSwbased diet did not affect nutritive and technological parameters of raw milk: MP/MF (+ 1.3 %), MP/DM (0.1 %) and MF/DM (1.0 %) ratios. In conclusion, observed data indicates that DDGSw at level of 17 % DM basis affected ewe milk yielding negatively, without affecting milk composition, nutritive and technological parameters.

Commonly, DDGS have been recognized at low/moderate levels in feedlot rations as substitute for both traditional protein and energy sources (Yossifov and Kovelov, 2012).But recent studies indicate that adding DDGS to dairy rations improve cow' dry matter intake (DMI) (Zhang et al., 2010), milk yield (Anderson at al., 2006;Chibisa et al., 2010), milk protein and fat (Schingoethe et al., 1999;Sasikala-Appukuttan et al., 2008).Nevertheless, there have been relatively few studies reported in which DDGS has been fed to sheep.Some suggested that it can be successfully fed to lactating dairy sheep without any effect on animal performance, milk composition and rennet abilities (Dimova et al., 2009;Yossifov, 2014a).So, our experiment was intended to explore the concept of supplementing lactating dairy ewe' diets with DDGSw.The objectives of this were to verify if higher (than recommended) DDGSw levels affect milk yield at the pick of lactation curve, and if the ED affect milk composition and milk nutritive and technological parameters.Such differences, if existing, may be used from animal nutritionists to balance dairy sheep total mixed ration.

Material and methods
Experimental animals and diets.The experiment was conducted at the Experimental Farm of the Institute of Animal Science, Kostinbrod, BG using 60-d feeding trail (7-d preparatory + 45-d experimental + 8-d closing periods).Sixteen lactating dairy ewes of Bulgarian Dairy Synthetic Population (BDSP) breed were randomly (by age, lactation, milk production, % milk fats, % milk protein) divided into two diet treatments (n=8): control (CD) and experimental diet (ED) in order to evaluate the effects of DDGSw supplementation during the pick of lactation (27 -72 lactating day).
The experimental design is shown in table 1. Daily ration (as DM basis) contained 75 % forage (meadow hay + corn silage) and 25 % concentrate mixture.CD concentrate mixture consisted of corn (7.72 %), wheat (8.79 %), sunflower meal (SFM= 8.26 %) and supplement (0.65 %).Part of the wheat and whole SFM of the CD were replaced by 16.75 % DDGSw in ED.Diets were formulated to be iso-caloric, iso-fibrogenous and equal in PDI, Ca and P to meet and exceed all nutrient requirements of lactating dairy ewes (NRC, 2007).The supplement provided Ca (limestone), ammonium sulphate and vitamin-mineral premix (per kg of diet: Mg -60.0 mg, Fe -1.3 mg, copper -1.0 mg, I -1.6 mg, Zn -60.0 mg, Co -1.0 mg, Vit.A -5000 IU, Vit.D -2000 IU, Vit.E -10.0 mg).The diets were fed twice daily -7.00 AM and 6.00 PM throughout the experimental period.Feed intake was being adjusted daily.Animals were provided free access to fresh water and salt blocks.
Feed sampling and analytical procedures.Feeds were sampled and analysed bimonthly.The feed refusals were collected and weighed daily and analysed twice a month.Samples were analysed for DM by drying in a forced-air drying oven at 65 o C for 48 h.Samples were ground to pass through a 1 -mm screen for further chemical analyses: crude protein (CP) (Kjeldahl N x 6.25), ether extract (EE), crude fibres (CF), ash, calcium (Ca) and phosphorus (P) according to AOAC (2002).
Milk sampling and Analysis.Milk yield was recorded twice a dayindividually per ewe, during the morning and evening milking.Milk samples were taken and analysed weekly in accordance to the regulations for milk sampling (country AC method).Physicochemical characteristics of the raw milk samples were analysed with apparatus EcoMilk (Milkana KAM 98-2A -Bultech Company).The following milk composition parameters were investigated: solids non fats (SNF), dry matter (DM), milk fats (MF) and milk protein (MP).
Biostatistical Analyses.The amount of feed offered and refused was recorded daily for each treatment (CD and ED) of ewe and feed intake and dry matter intake (DMI) was calculated (average per sheep).Feed efficiency (FE) was calculated as ratio of average daily milk yield to the average DMI (M: F).The following indices and ratios for milk samples were calculated: MP/MF, MP/DM and MF/DM to evaluate the nutritive and technological qualities of raw sheep milk.All parameters were analysed using MS Office 2007 and Student t-test.Statistical significance was accepted at p<0.05 and p≥0.05 but ≤0.1 was interpreted as indicating a trend towards significance.
The chemical composition of total mixed ratios (TMRs) was similar in DM (2.1 kg) and ensured iso-caloric (on the average 2.3 FUM as net energy), isofibrogenous (on the average 0.6 kg CF) and equal in PDI (on the average 0.19 kg), Ca (0.017 kg) and P (0.009 kg).Balance of Protein in Rumen (BPR) was between -0.001 and + 0.002 kg for CD and ED, respectively (table 3).
Intake.Average daily intake (ADI), dry matter intake (DMI) and consumption of nutrients from TMRs are summarized in figure 1. Sheep fed ED consumed higher levels of TMRs as fed basis (2.2 %), DM from forage (3.0 %), DM from concentrate mixture (5.4 %) and DM from TMRs (3.9 %).Thus, our results are in agreement with the reported DDGS-induced increase in feed consumption (as DMI).The higher values of average daily intake (ADI) of CP (33.2 %), Ash (6.4 %), Ca (22.1 %) and P (36.5 %) were found in ED compared to CD.As DM basis (except DM); 2 Our own data (our unpublished data); 3 As fed basis; 4 According to Bulgarian feed evaluation system.PDI-Protein truly digestible in small intestines, BPR-Balance of protein in rumen, FUM-Feed units for milk as net energy.
The higher EE intake from ED (48.7 %) seem to be compensated by the lower consumption of fibres (5.5 %) and did not increase the net energy intake expressed as feed units for milk (2.2 %).Consumption of PDI was higher at ED (10.0 %) and balance of protein in rumen varied between CD (-1.39) and ED (+ 3.23 %).Animal performance.Ewe performance is shown in table 4. The DDGSw supplementation to the ewe diets decreased (5.8 %) significantly (p<0.001) the average daily milk yield for the studied segment of lactation curve (1.32 L (CD) to 1.24 L (ED)).The observed distance was higher (6.8 %) when milk yield was corrected to 6.5 % milk fat (FCM) as a difference between ED and CD (p<0.001).Milk analyses.Milk composition is presented in figure 2. The differences between investigated milk parameters were not significant among the treatments.So, our data on the sheep milk content correspond to Boikovski et al. (2006) and Djorbineva et al. (2002).Also, they're within the limits of dairy sheep and standards for SBDP breed (Hinkovski et al., 1984;Nedelchev et al., 2003).
Besides, we evaluated milk properties by physicochemical parameters, nutritive and technological ratios and indices in order to get more profound insight on its quality.Percentage of SNF and DM (fig.2) among the groups was within the norms (10.93 -11.02 and 18.03 -18.05 %) and the differences were not significant (CD << ED).Similar values were reported by Boikovski et al. (2005).However, some authors found lower values (Stancheva, 2003), while other reported higher (Djorbineva et al., 2002).The content of milk fat (fig.2) showed downward tendency -ED << CD (1.1 %), but results were within the normal range and corresponded with the results found by Stancheva (2003).Some found lower values (Djorbineva et al., 2002), andother -higher (Stancheva et al., 2011).Milk proteins were actually the same among the groups (5.66 %) and exceeded the values found by other authors (Boikovski et al., 2005;Stancheva et al., 2011).
The nutritive and technological parameters of raw sheep milk were characterized by the use of the following ratios (figure 3): MP/MF, MP/DM and MF/DM.All values were within the recommended standards (0.80, 0.31 and 0.39).The MF/DM and MP/DM values were lower at ED (1.0 and 0.1 %) than CD and corresponded to the values published by Stancheva ( 2003), but were lower than values found by Djorbineva et al. (2002) andStancheva et al. (2011).The MP/MF ratio was higher at ED (1.3 %) than CD but the values were lower than those found by Djorbineva et al. (2002) andStancheva et al. (2011).The nitrogen, as a limiting factor in high productive dairy animals was used to be established the effect of dietary protein source (SFM vs. DDGSw) on milk production (figure 5).So, animals fed with CD consumed (253 g) lower levels of dietary CP (as N), compared with ED (24.9 %).The percentage of N retained in milk rose in order ED << CD (-5.4 %).Thus, the percentage of N utilization was higher in SFM-based diet (40.8 %) compared with ED.The observed results of the present study indicate that DDGSw supplementation of lactating dairy sheep in early to peak of lactation, as protein source, decreases milk yield but has no effect on its composition, nutritive and technological qualities.Lower to moderate levels of supplementation should be tested (Dimova et al., 2009).

Conclusion
The results in our experimental conditions shows that: • The data on the chemical composition of DDGSw were as follows: DM -92.72 %; CP -368.50 g/kg DM; EE -57.00 g/kg DM; CF -65.50 g/kg DM; Ash -48.90 g/kg; Ca -0.12 g/kg DM and P -0.97 g/kg DM; • Sheep fed ED consumed higher levels of total diet as fed basis (2.2 %), DM from forage (3.0 %), DM from concentrate mixture (5.4 %) and DM from total diet (3.9 %), average daily intake (ADI) of CP (33.2 %), Ash (6.4 %), Ca (22.1 %) and P (36.5 %) as compared with CD.The higher EE intake from ED (48.7 %) compensated for the lower consumption of fibres (5.5 %) and didn't increase intake of feed units for milk (2.2 %).Consumption of PDI was higher in ED (10.0 %) and balance of protein in rumen varied between CD (1.39) and ED (3.23 %); • Average daily milk yield for the studied segment of lactation curve was significantly (p<0.001)lower in ED < CD (5.8 %).The differences between treatments were significant and statistically proved as 6.5 % fatcorrected milk -CD >> ED (p<0.001); • Differences between controlled physicochemical milk composition parameters (solids non fats (SNF), dry matter (DM), milk fat (MF) and milk protein (MP)) and nutritive and technological parameters (MP/MF, MP/DM, MF/DM) were within the recommended range and were not affected by treatments; • The conversion of nutrient ingredients into 1 L milk production was less effective in animals consuming DDGSw-based diet, relative to CD: Total diet (9.7 %), DM (11.5 %), CP (14.1 %), net energy as FUM (4.4 %), PDI (18.0 %).; • The feed efficiency, presented as milk/feed (M/F) ratio was advantaged by the SFM-based diet (19.3 %).
So, we can conclude that higher (than recommended) DDGSw levels (17 and 44 % as fed total ration or concentrate mixture, respectively) in our experimental units affected animal response negatively.Thus, the ED decreased significantly milk yield, but did not affected milk composition, nutritive and technological parameters.

Figure 1 .
Figure 1.Average daily intake of forage, DM and nutrients

Figure 3 .Figure 4 .
Figure 3. Nutritive and technological quality of sheep milk Figure 5. Nitrogen balance