Effect of Dietary Protein Supplementation on Sheep Milk Coagulation Properties

Document Type: Research Article


Departmentof Animal Nutrition and Feed Technologies, Institute of Animal Science, Kostinbrod, Bulgaria


The objectives of this experiment were to evaluate the effects of dietary protein supplementation in lactating dairy ewe’s diets on milk coagulation properties. Milk samples (n=126) were analyzed to assess the source of variation for rennet coagulation ability at the 6th (RCA6) and 12th hour (RCA12), milk clotting time (MCT, s) and an index of milk clotting time (IMCT, %). In addition, data were used to determine the influence of dietary protein source (sunflower meal (SFM) vs. rapeseed meal (RSM)) and lactating day (27, 35, 42, 49, 56, 63 and 70) on RCA6, RCA12 and MCT. Eighteen early lactation (4-10 weeks) dairy ewes from the synthetic Bulgarian dairy population breed (SBDP) were allocated into two isonitrogenous (crude protein (CP)=18%, dry matter (DM) basis) dietary treatments (n=9 per diet) formulated to contain equal amounts of fibre, energy, protein digestible in small intestines (PDI) and Ca:P ratio. The rates of MCT (s) were measured as time from rennet addition to onset of rennet-induced gel. RCA values were measured subjectively based on a scale of coagulum characteristics (score 1-3). Results showed a significant effect (P<0.05) of supplement (RSM vs. SFM) on RCA6 and a tendency at RCA12 (p=0.10). The influence on MCTand IMCT also showed such a tendency (p=0.11). Studied correlations between RCA6, RCA12 and MCT values todiet supplements at different lactation stages (days) showedno strong relationships, but the directions and strengths were permanent over the evaluated periods. We can conclude, that the investigated parameters (RCA6, RCA12, MCT and IMCT) were affected by dietary protein source (SFM vs. RSM) in regards to firmer coagulum (RCA6 and RCA12) and shorter MCT for milk collected from ewes fed SFM vs. RSM based diets.


Aleandri R., Schneider J. and Buttazzoni L. (1990). Evaluation of milk for cheese production based on milk characteristics and formagraph measures.J. Dairy Sci. 72, 1967-1975.
AOF Crop Report. (2012). AustralianSquare. Sydney, Australia, NSW: Australian Oilseeds Federation.
Bittante G., Penasa M. and Cecchinato A. (2012). Genetics and modelling of milk coagulation properties.J. Dairy Sci. 95,6843-6870.
Clark S. (1993). Associations between breed, age, lactation number, days in milk, season, month and percent protein in goat milk.MSThesis. Cornell Univ., Ithaca, NY.
Cumby N., Zhong Y., Naczk M. and Shahidi F. (2008). Antioxidant activity and water-holding capacity of canola protein hydrolysates. Food Chem. 109, 144-148.
Dimov N., Georgiev I., Velev S. and Chomakov C. (1974). Controlof Milk and Milk Products. Publisher: Zemizdat, Sofia, Bulgaria.
Guinee T., Mulholland E., O’Brien B. and Murphy J. (2001). Effect of dietquality on the suitability of mid-lactation bovine milk for cheddar cheesemanufacture. Australian J. Dairy Technol. 56, 3-8.
Harzia H., Kilk K., Ariko T., Kass M., Soomets U., Joudu I., Kaart T., Arney D., Kart O. and Ots M. (2013). Crude glycerol as glycogenic precursor in feed,effects on milk coagulation properties and metabolic profiles of dairy cows. J. Dairy Res. 80, 190-196.
Joudu I., Henno M., Varv S., Viinalass H., Pussa T., Kaart T., Arney D. and Kart O. (2008). The effect of milk proteins on milk coagulationproperties in Estonian dairy breeds. Vet. Ir Zootech. 46, 4-19.
Lucey J. (2002). Formation and physical properties of milk protein gels. J. Dairy Sci. 85, 281-294.
Malossini F., Bovolenta S., Piras C., Dalla Rosa M. and Ventura W. (1996). Effect of diet and breed on milk composition and rennetcoagulation properties. Ann. Zootech. 45, 29-40.
Marczak E., Usui H., Fujita H., Yang Y., Yokoo M. and Lipkowski A. (2003). New antihypertensive peptides isolated from rapeseed. Peptides. 24,791-798.
Mellema M., Walstra P., vanOpheusden J. and van Vliet T. (2002). Effects of structural rearrangements on the rheology of rennetinduced casein particle gels. Adv. ColloidInterface Sci. 98, 25-50.
Politis I. and Ng-Kwai-Hang K. (1988). Effects of somatic cell counts and milk composition on the coagulating properties of milk. J. Dairy Sci. 71, 1740-1746.
Storry J., Grandison A., Millard D., Owen A. and Ford G. (1983). Chemical composition and coagulating properties of renneted milks from different breeds and species of ruminant. J. Dairy Res. 50, 215-229.
Sundekilde U., Frederiksen P., Clausen M., Larsen L. and Bertram H. (2011). Relationship between the metabolite profile and technological properties of bovine milk from two dairy breeds elucidated by NMR-based metabolomics. J. Agric. Food Chem. 59, 7360-7367.
Yossifov M. (2014). Influence of different protein supplements on sheep milk quantity and quality. Pp.392-403 in Proc. 15th Int. Feed Technol. Symp., Novi Sad, Serbia.
Yossifov M. (2013). Utilization by-products of biofuel industry in sheep diets. Ph D. Thesis. Institute of Animal Science. Bulgarian Agricultural Academy, Sofia, Bulgaria.
Yossifov M. (2014). Influence of dietary protein source on milk clotting time and rennet coagulation ability.Poster Session 48 in 56th EAAP Ann. Meet. Copenhagen, Denmark.