Effects of Bypass protein on wool fiber quality 1Dawit Mamo Zegeye2Tegene Negesse

Effects of Bypass protein on wool fiber quality
1Dawit Mamo Zegeye2Tegene Negesse (Professor, PhD)
1Aksum University, College of Agriculture, Department of Animal Science
E-mail: [email protected] University, College of Agriculture, School of Animal Range Science
E-mail: [email protected]
Abstract
The paper is aimed to review the effects of bypass protein on wool fiber quality. Different searching engines have been employed to find appropriate information. Fiber diameter is widely acknowledged as the most important wool characteristics when assessing wool quality and value accounting for approximately 75% of the total price of raw wool. Growth of lamb wool fibre is a continuous process influenced by: a genetic basis, nutrition, general physiological status and different environmental factors. Feeding different levels of formaldehyde treated feed ingredients have no effects on wool quality fiber. However, protein containing a high level of sulphur-containing amino acids that is less degradable in the rumen has favour increased wool production. When ruminal degradation of protein is avoided, substantial increase in wool growth rate can be obtained with protein. Finally, research works concerning the effect of feeding by-pass protein are scarce in Ethiopia specifically and in the areas too. This suggests the urgent need to conduct research in this area, which is vital in improving the nutrition and thereby increase the productivity of wool fiber qualities.
Keywords: Bypass; Protein; Sulfur-containing; Wool fiber.
Introduction
By-pass (rumen undegradable) protein is defined as the proportion of dietary protein that passes from the rumen to the lower digestive tract, without being fermented in the rumen, for digestion and absorption as it would be in non-ruminants (Varga, 2010). Different feeds have varying degrees of naturally protected proteins. Cottonseed cake, maize gluten meal and fish meal are among the naturally occurring rumen by-pass proteins while oilseed cakes like groundnut, mustard and rapeseed are highly degradable in the rumen. These highly-degradable protein supplements need protection against degradation by rumen proteolytic enzymes to increase the flow of protein in to the small intestine (Walli, 2011).
The main interest of protein protection from ruminal degradation is therefore to enhance the supply of essential amino acids to the highly productive animal by preventing rumen degradation of high quality protein and reduction of nitrogen losses as urea in the urine (Kamalak et al., 2005). However, the magnitude of ruminal destruction of dietary proteins varies, and greatest responses can be expected only when rumen soluble proteins are protected. Thus, to obtain responses with supplements of protected protein or amino acids, one must know that amino acids are in short supply for animals performing a particular physiological function (Chalupa, 1975; cited by Kamalak et al., 2005).

Wool growth is a function mainly of the amount of amino acids reaching the intestine (Hynd and Allden, 1985) rather than energy supply (Reis et al., 1992). Furthermore, the amino acid pattern of the protein which reaches the intestine may affect wool growth since sulphur-containing amino acids (SAA) are first limiting in terms of wool protein synthesis (Reis and Tunks, 1978). Therefore, the ruminally degradable proportion of dietary protein becomes a critical factor for wool growth and, on isonitrogenous diets, wool growth responds well to less degradable proteins, particularly when they are high in SAA concentration (White et al., 1999). Consequently, SAA supplementation in the form of methionine, cysteine is effective for enhancing wool growth if degradation in the rumen is avoided (Reis and Tunks, 1978). Therefore, the term paper is aiming to review the effects of bypass protein on wool fiber quality.
Literature Review Wool Fiber Quality Characteristics
Wool is not a uniform biological product because its physical characteristics vary depending on sheep genetics, environment and management strategies (Warn et al., 2006; Poppi and McLenan, 2010). Wool value is intrinsically linked to its characteristics and the ability to meet commercially pre-determined parameters (Wood, 2003; Jones et al., 2004; Purvis and Franklin, 2005; Bidinost et al., 2008). The quality of wool has determined by the physical and mechanical properties: diameter (fineness), height, length, tortuosity, strength and ductility of the wool fibres (Ružic-Muslic, 2006). In addition, these properties have ascertained by factors of genetic and paragenetic nature. The most important characteristic of wool is definitely diameter (fineness) fibres, which implies an average thickness or diameter of the cross section of fibre expressed in micrometres (µm). Fibre diameter (FD) refers to the average width of a single cross section of wool fibre (Gillespie and Flanders, 2010). It is measured in microns (µm) which equates to one thousandth of a millimetre (Cottle, 1991; Cottle, 2010; Poppi and McLenan, 2010; Rowe, 2010). Fiber diameter (FD) is widely acknowledged as the most important wool characteristics when assessing wool quality and value (Edriss et al., 2007; Kelly et al., 2007; Rowe, 2010) accounting for approximately 75% of the total price of raw wool (Jones et al., 2004; Mortimer et al., 2010).
Growth of lamb wool fibre is a continuous process influenced by: a genetic basis, nutrition, general physiological status and different environmental factors. The potential of sheep for wool production was determined during their embryonic development. During intrauterine development of lambs, begins the formation of the hair, to the extent of which depends on the genetic potential of the animal. The number and size of wool fibres produced by follicles (structural units in the skin of sheep) determine the quantity of wool produced. Primary follicles occur in the skin of the foetus on the ninetieth day after fertilization, while the secondary follicles develop from that moment on until the birth of lambs (Jovanovic et al., 2001). The volume of maturation of follicles and production of wool fibres have closely related to nutrition and intensity of lamb growth. Because the wool fibre is a protein matter whose main ingredient is keratin, the presence and source of protein in the diet affect the yield and quality of fibre (Zeremski et al., 1989). According to the research results obtained by Slen (1969) increase of protein levels from 7 to 10 % in dry matter of isoenergy diet used for feeding sheep, has resulted in an increase in production of unwashed wool by 16 %. At the same time, influenced by the above nutrition treatment, in terms of length and thickness of wool fibre, improvement of 8-12 % was established. In order to investigate the optimal protein content in the diet for maximal growth of high-quality wool fibre, the author carried out a trial on Romney Marsh breed lambs fed diets to suit their basic requirements and rations for fattening with a high proportion of protein in dry matter. It was established that during the period of 6 months of the experiment the lambs fed fattening diets with a high proportion of protein realized by 343 % more of unwashed wool, superior tortuosity of fibre, by 172 % higher fibre, by 206 % stronger and slightly coarser fibre.
Table 1: Relative importance of raw wool characteristics on worsted processing performance
No. Raw wool characteristic Importance
1 Yield ****
2 Fibre diameter ****
3 Length ***
4 Strength/position of break ***
5 Colour ***
6 Coloured ?bres ***
7 Fibre diameter variability **
8 Length variability **
9 Degree of cottedness **
10 Crimp/resistance to compression **
11 Staple tip *
12 Age/breed/category *
13 Style/character/handle *
Notes: ****Most important, *** Major, **Secondary, *Minor.

Source: Anton and Lawrance (2010)
Dietary effect of bypass protein on Sheep Wool fiber quality
Proteins that avoid bacterial hydrolysis in the rumen (undegradable protein), increase the wool production through increase in supply of the organism with amino acids, especially cystine, which is a limiting factor for the production of wool (Dragana Ružic-Muslic et al., 2016). According to Dragana Ružic-Muslic et al., (2016), the infusion of cystine into abomasums or blood cans double the growth of wool, while the infusion of methionine increases the wool growth by providing sulphur for the synthesis of cystine. Another method to protect proteins from degradation in the rumen is treatment with formaldehyde. Zeremski et al. (1989) showed that lambs fed diets supplemented with casein (previously treated with formaldehyde) realized by 70% more wool than those who received untreated casein. Chalupa (1975) studied the impact of application of formaldehyde treated feeds on growth of wool. Comparing the effects of soybean meal (untreated and treated) as the protein source, the author found that the increase of wool in the use treated soybean meal of 117 % compared to untreated (100 %). The use of untreated meat meal as a source of undegradable protein in the sheep diet had a greater effect on the growth of wool (100 %) compared to treated meal (96%). A similar relationship has noted in the use of flax meal (100:92 %). Kiljpa and Kravcov (1989) studied the effect of different protein supplements on the productivity of four (4) groups of sheep. As a source of protein, the Group I used sunflower meal, Group II used peas, Group III soybean meal and Group IV cottonseed meal. Respectively, wool yield in animals at the age of two years was 4.75, 4.78, 5.20, 4.73 kg. Effect of different concentrations of dehydrated alfalfa (0, 5, 10, 15 and 20 %) as source of undegradable protein in the diets for feeding lambs from 17.0 to 36.0 kg on wool production, Urbaniak (1994) found that the greatest accumulation of proteins in wool fibres (4.11 g day-1) was achieved by lambs fed concentrate mixture that contained 10 % of dehydrated alfalfa.
Table 2: The effects of Bypass protein on wool yield, staple and fiber growth in sheep, expressed as the difference with the control treatment.Bypass proteins BWG (g/day) CWP (g/d) Wool quality Source
FG (µm) SL (cm) Rapeseed oil meal (HCHO) treated 57** 4.0* 20.5 3.5 G. Habib et al., 2001
Casein HCHO treated 43 8.5 1.9 2.9 J. Kowalczyk et al., 1993
Sunflower oilcake meal 19 1.21* 0.28 0.45 J.A. Baldwin et.al, 1993, J.coetzee et.al, 1995,
RPMet Premix NA 1.27 0.45 0.28 J.A. Baldwin et.al, 1993, J.coetzee et.al, 1995,
Guar meal treated with HCHO NA 213 NA 3.5 O.P, Mathur, 1990
Guar meal treated HCHOand urea NA 218 NA 3.5 O.P, Mathur, 1990
HCHO-treated silage NA 4.46 0.93 3.22 T. N. Barry et al., 1973
HCRO-treated silage
+ methionineNA 7.03 0.93 5.22 T. N. Barry et al., 1973
Note: *Significant difference p<0.05. NA: not available. In parenthesis: number of observations.
Other studies also showed that, growth of clean wool was lower in control sheep and increased with feeding of the treated rapeseed cake over the other supplements (G.Habib et al, 2001) however, supplements of treated rapeseed cake did not cause any significant change in the staple length or fiber diameter (G.Habib et al, 2001). Earlier work has shown that replacement of soluble protein with slowly degradable protein source either increased (Hoaglund et al., 1992; Thomas et al., 1994) or did not change (Baldwin et al., 1993; Kowalczyk et al., 1993) wool growth in sheep. In studies, where positive response to undegradable protein was found in wool growth, the basal diet was of low quality. Conversely, sheep receiving grass hay or other good quality forages, did not respond to differences in protein degradability of the supplements. These observations support G.Habib et al, (2001) findings where difference in degradability of protein supplements did not influence wool yield in sheep grazing range grasses with CP contents above 10% in DM.
In agreement to (G.Habib et al, 2001) findings, Kowalczyk et al. (1993) reported that feeding of HCHO-treated rapeseed meal failed to improve wool yield and quality over the sheep given untreated meal. Recent work in the same laboratory (Marghuzani et al., 1999) also demonstrated that N retention in sheep given U-RSC or T-RSC supplements was the same, namely, 4.48 and 4.72 g per day, respectively. Small differences in the availability of total protein (microbial and dietary) in the intestine on different four supplements (Wheat bran, treated rapeseed cake, untreated rapeseed cake and cotton seed cake) were apparently not sufficient to cause difference in wool growth and quality among these diets (G.Habib et al, 2001). It can be assumed also that the escaped protein may not have changed the balance of amino acids in favour of wool growth and hence negated the difference between degradable and undegradable protein supplements (G.Habib et al, 2001). Merchen and Titgemeyer (1992) reported that undegraded proteins reaching the small intestine differ in their ability to supply total absorbable amino acids. They further postulated that two protein sources providing different quantities of amino acids may not differ in the supply of specific amino acids that are limiting performance. This would mean that feeding proteins that escape rumen fermentation might be of little benefit if limiting amino acids are deficient in the supplement.
Also, Chalupa (1975) has studied the impact of the application of formaldehyde treated feeds on growth of wool. Comparing the effects of soybean meal (untreated and treated) as the protein source, the author found an increase in wool by 117% when used treated soybean meal compared to untreated (100 %).

The use of untreated meat meal as a source of undegradable protein in the sheep diet had a greater effect on the growth of wool (100 %) compared to treated meal (96 %). A similar relationship noted in the use of flax meal (100: 92 %).
In order to investigate the optimal protein content in the diet for maximal growth of high-quality wool fibre, Slen (1969) performed a trial on Romney Marsh breed lambs fed diets to suit their maintenance requirements and rations for fattening with a high proportion of protein in dry matter. It has found that during the period of 6 months of the experiment, the lambs fed fattening diets with a high proportion of protein had by 343 % more of unwashed wool, superior fibre tortuosity, by 172 % increase in the height of fibre and by 206 % stronger and slightly coarser fibre.
Feeding protein containing a high level of sulphur-containing amino acids that is less degradable in the rumen would favour increased wool production. For example, canola (rapeseed) meal and lupin seed both contain similar and high levels of crude protein, but canola meal is less degraded in the rumen (AFRC, 1993). Merino lambs fed a diet containing canola meal grew 7-64 % more wool than sheep fed a lupin seed diet (Masters and Mata, 1996; White et al., 2000) and the response depends on the level of intake and the proportion of canola meal in the diet. When ruminal degradation of protein is avoided, substantial increase in wool growth rate can be obtained with protein, and only small responses are associated with energy (Allden, 2001). Reis (2000) showed that very high rates of wool growth could be obtained with moderate energy intakes when casein was given through the abomasum.
Conclusions and Recommendation
Feeding protein containing a high level of sulphur-containing amino acids that is less degradable in the rumen has favour increased wool production. When ruminal degradation of protein is avoided, substantial increase in wool growth rate can be obtained with protein. Finally, research works concerning the effect of feeding by-pass protein are scarce in Ethiopia and in other areas. This suggests the urgent need to conduct research in this area, which is vital in improving the nutrition and thereby increase the productivity of wool fiber quality.
References

AFRC (1993): Energy and Protein Requirements of Ruminants: on Advisory Manual Prepared by the AFRC Technical Committee on Responses to Nutrients, eds., CAB International, Wallingford, UK, pp.159.

Ash, A.J., Norton, B.W., 1987a. Effect Of D,L-Methionine Supple- Mentation On ?eece Growth By Australian Cashmere Goats, Short Note. J. Agric. Sci. Camb. 109, 197–199.

Baldwin, J.A., Horton, M.J., Wohlt, J.E., Palatini, D.D., Emanuele, S.M., 1993. Rumen-Protected Methionine For Lactation, Wool And Growth In Sheep. Small Rumin. Res. 12, 125±132.
Bidinost F., Roland D.L.,Dodero A.M., Cano E.M.,Taddeo H.R., Mueller J. P., Poli M. A. (2008): Wool Quantitative Trait Loci In Merino Sheep. Small Ruminant Research, 74, 113-118.

Bishop, S.C., 1994. Genetic Parameters And Selection Objectives For Cashmere Goats. In: Laker, J.P., Bishop, S.C. (Eds.), Genetic
Chalupa W. (1975): Rumen Bypass And Protection Of Proteins And Amino Acids. Journal Dairy Science, 58, 1198-1218.

Cottle D. J. (1991): Australian Sheep And Wool Handbook, Eds., Inkata Press, Melbourne, Pp 499.

Cottle, D. J. Wool Preparation And Metabolism. In: Cottle, D. J. (Editor) (2010): International Sheep And Wool Handbook, Eds., Nottingham University Press, Nottingham, Uk, 581-618.

Cottle, D.J. (2010). Wool Preparation And Metabolism. In: Cottle, D.J. (Editor), International Sheep And Wool Handbook. Nottingham University Press, Nottingham, UK, Pp. 581618.

Cottle, D.J., Carter, R.R., 1992. Overcoming Seasonal Depression In Wool Production In Romney Marsh Ewes By Feed Supplementa- Tion. Proc. Aust. Soc. Anim. Prod. 19, 135±137.
Edriss M.A., Dashab G., Ghareha. A., Aghaji M.A., Nilforoosh A., Movassagh H. (2007): A Study Of Some Physical Attributes Of Naeini Sheep Wool For Textile Industry. Pakistan Journal Biology Science, 10, 9, 415-420.

Gambetta, A., Gratarola, M., Federico, J.L., Hitateguy, J.E., Mussio, P., 1992. Seasonal Wool Growth In Corriedale Wethers. Prod. Ovina 5, 85±89.
Gillespie J.R., Flanders F.B. (2010): Modern Livestock And Poultry Production, 8th Edition, Delmar Cengage Learning, New York, Pp. 1073.

H. Galbraith, 2000. Protein And Sulphur Amino Acid Nutrition Of Hair ?bre-Producing Angora And Cashmere Goats. Livestock Production Science 64 (2000) 81–93
Hart, J., Yáñez-Ruiz, S. M. Duval, N. R .Mcewan, And C. J .Newbold, 2007. Plant Extracts To Manipulate Rumen Fermentation. J.Ani. Feed Sci. 147(1-3):8-35.

Hoaglund, C.M., Thomas, V.M., Petersen, M.K., Kott, R.W., 1992. Effects Of Supplemental Protein Source And Metabolizable Energy Intake On Nutritional Status In Pregnant Ewes. J. Anim. Sci. 70, 273±280.
Hynd, P.I., 1989. Effects Of Nutrition On Wool Follicle Cell Kinetics In Sheep Differing In Ef?ciency Of Wool Production. Aust. J. Agric. Res. 40, 409–417. Improvement Of Fine Fibre Producing Animal. European Fine Fibre Network Occasional Publication. No.1, Macaulay Land Use Research Institute, Aberdeen, Pp. 31–46.
J. Kowalczyk, Z. Buczkowski, Alina Jaczewska And Urszula Pawlus, 1993. Performance And Wool Growth In Lambs Fed Rations Containing Formaldehyde Treated Protein. Journal Of Animal And Feed Sciences, 2, 1993, 35-4.

J.C. And Cochrane, M.J. (1970) Digestibility And Crude Protein Changes In Ten Maturing Pastures Species. Proceedings From The Australian Society Of Animal Production. Vol. 8, Pp. 531-536
Jones C., Menezes F., Vella F. (2004): Auction Price Anomalies: Evidence From Wool Auctions In Australia. Econ. Rec., 80, 271-288.

Jovanovic R. (1996): Ishrana Ovaca, Eds., Stylos, Novi Sad, Pp. 420.

Jovanovic R., Dujic D., Glamocic D. (2001): Ishrana Domacih Životinja, Eds., Stylos, Novi Sad, Pp. 713.
Kelly M.J., Swan A. A., Atkins K. D. (2007): Optimal Use Of On-Farm Fibre Diameter Measurement And Its Impact On Reproduction In Commercial Merino Flocks. Australian Journal Of Experimental Agriculture, 47, 525-534.

Kiljpa A.B. And Kravcov L.F. (1989): Ocenka I Normirovanie Proteinogo Pitanija Žvacnih Životnih. Tezis Dokladov. 51. Barnaul, 03-04.10, 9, 7.

Kowalczyk, J., Buczkowski, Z., Jaczewska, A., Pawlus, U., 1993. Performance And Wool Growth In Lambs Fed Rations Containing Formaldehyde-Treated Protein. J. Anim. Feed Sci. 2, 35±42.
Langlands, J. P. (1970). Aust. J. Exp. Agric. Anim. Husb. 10, 665-71.Marghuzani, I.B., Habib, G., Siddiqui, M.M., 1999. Nitrogen Retention And Nutrient Digestibility In Sheep Given A Basal Diet Of Sorghum Hay Supplemented With Protein Of Varying Degrad- Ability. Sarhad J. Agric. 15, 381±386.
Masters, D.G., Stewart, C.A. And Connell, P.J. (1993). Changes In Plasma Amino Acid Patterns And Early Wool Growth During Late Pregnancy And Early Lactation. Aust. J. Agric. Res.. Vol 44, Pp. 945-57
Mata, G., Masters, D.G., Chamberlain, N.L. And Young, P. (1997). Aust. J. Agric. Res. 48, 1111-20.

Merchen, N.R., Titgemeyer, E.C., 1992. Manipulation Of Amino Acid Supply To The Growing Ruminants. J. Anim. Sci. 70, 3238± 3247.
Mortimer, S.I., Atkins, K.D., Semple, S.J., Fogarty, N.M. (2010). Predicted Responses In Merino Sheep From Selection Combining Visually Assessed And Measured Traits. Anim. Prod. Sci., 50, 976-982.

O.P, Mathur, 1990. Evaluation Of By-Pass Protein And Urea For Wool Production. Annals Of Arid Zone 29 (2): 131-135.
Ørskov, E.R., 1992. Protein Nutrition In Ruminants, 2nd Edition, Academic Press, London. Souri, M., Galbraith, H., Scaife, J.R., 1998a. Comparisons Of The Effect Of Genotype And Protected Methionine Supplementation On Growth, Digestive Characteristics And ?bre Yield In Cashmere And Angora Goats. Anim. Sci. 66, 217–223.

Poppi, D.P., Mclennan, S.R. (2010). Nutritional Research To Meet Future Challenges. Anim. Prod. Sci., 50, 329-338.
Purvis I.W., Franklin I.R. (2005): Major Genes And Qtl Influencing Wool Production And Quality: A Review. Genetics Selection Evolution, 37, 97- 107.Restall, B.J., Restall, H., Restall, M., Perry, A., 1994. Seasonal Production Of Cashmere And Environmental Modi?cation In Australian Cashmere Goats. In: Laker, J.P., Allain, D. (Eds.), Hormonal Control Of Fibre Growth And Shedding, Vol. Euro- Pean Fine Fibre Network, Publication No. 2, Macaulay Land Use Research Institute, Aberdeen, Pp. 63–74.

Rohon Leach And Emma Doyle, 2013. Wool Quality And Rumen-Protected Lysine In Merino Ewes During Late Pregnancy And Early Lactation. 4th Year Honours Thesis Submitted In Partial Fulfilment Of Bachelor Of Rural Science (Honours). To The School Of Environmental And Rural Science University Of New England.
Rowej.B. (2010): The Australian Sheep Industry – Undergoing Transformation. Animal Production Science, 50, 991-997.

Russel, A.J.F., 1995. Current Knowledge On The Effects Of Nutrition On ?bre Production In Nutrition And Grazing Ecology Of Speciality ?bre-Producing Animals. In: Laker, J.P., Russel, A.J.F. (Eds.), European Fine Fibre Network Publication, Vol. No. 3, Macaulay Land Use Research Institute, Aberdeen, Pp. 3–21.

Ružic-Muslic D. (2006): Uticaj Razlicitih Izvora Proteina U Obroku Na Proizvodne Rezultate Jagnjadi U Tovu. Doktorska Disertacija, Poljoprivredni Fakultet, Beograd-Zemun, Pp. 160.

Slen S. B. (1969): Nutrition In Relation To Wool Production And Body Growth In Sheep. In Nutrition Of Animals Of Agricultural Importance, SIR DAVID
T. N. Barry , P. F. Fennessy & S. J. Duncan (1973) Effect Of Formaldehyde Treatment On The Chemical Composition And Nutritive Value Of Silage, New Zealand Journal Of Agricultural Research, 16:1, 64-68, DOI: 10.1080/00288233.1973.10421161
Thomas, V.M., Clark, C.K., Schuldt, C.M., 1994. Effects Of Sub- Stituting Feather Meal For Soybean Meal On Ruminal Fiber Ferme- Ntation And Lambs And Wool Growth. J. Anim. Sci. 72, 509±514.
Urbaniak m. (1994): Effect Dehydrated Lucerne On Lamb Performance And Protein And Energy Deposition In The Body. Journal Of Animal And Feed Sciences, 3, 191-199.
Varga, G.A., 2010. Why Use Metabolizable Protein For Ration Balancing? Department Of Dairy And Animal Science, Pennsylvania State University, Pennsylvania. Retrieved On 15/042012 From Http://Www.Das.Psu.Edu/Research-Extension/Dairy/Pdf/Vargametabolizableprotein.PdfWalli,T.K., 2011. Rumen By-Pass Protein Technology. In:FAO. Successes And Failures With Animal Nutrition Practices And Technologies In Developing Countries. Proceedings Of The FAO Electronic Conference. FAO Animal Production And Health Proceedings. No. 11. Rome, Italy.Pp.61-64.Warn, L.K., Geenty, K.B., Mceachern, S., 2006. Wool Meets Meat: Tools For A Modern Sheep Enterprise. In: Cronjé, P., Maxwell, D.K. (Eds.), Australian Sheep Industry Cooperative Research Centre Conference, Orange, Australia, Pp. 60-69.
Wood, E. (2003). Textile Properties of Wool and Other Fibres. Wool Tech.Sheep Breed., 51, 272-290.
Woods, J.L., Orwin, D.F.G., 1988. Seasonal Variation In The Dimensions Of Individual Romney Wool ®Bers Determined By Autoradiographic Tech. N. Z. J. Agric. Res. 31, 311±323.
Zeremski D., Pavlicevic A., Grubic G. (1989): Uticaj Ishrane Na Prinos I Kvalitet Vune. XI Savetovanje Jugoslovenskog odbora za ovcarstvo i kozarstvo, 87100.