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Fatty acid composition of Verata goat kids fed either goat milk or commercial milk replacer
Small Ruminant Research ELSEVIER
Small Ruminant Research 14 (1994) 61-66
Fatty acid composition of Verata goat kids fed either goat milk or commercial milk replacer A. Rojas ~', C. L6pez-Bote b'*, A. Rota a, L. Martin a, P.L. Rodrfguez a, J.J.
Tovar a ~Departamento de Zootecnia, Facultad de Veterinaria, Universidad de Extremadura, 10071 Cdceres, Spain hDepartamento de Produccidn Animal, Facultad de Veterinaria, Universidad Complutense de Madrid. 28040 Madrid. Spain Accepted 3 September 1993
Abstract
Fatty acid composition of perirenal fat of young Verata male and female kids fed with natural milk and with three concentrations of commercial milk replacer was studied. There was no effect associated with sex. In each gender the only statistical difference in fatty acid composition between the tour feeding groups under study were pentadecanoic acid (C15:0), heptadecanoic acid (C17:0) and heptadecenoic acid (C17:l) which were higher in all cases in naturally fed kids (P < 0.05). The origin of oddnumbered fatty acids in depot fats of goat kids is discussed considering the possible role of microbial rumen synthesis in goat kids or the direct incorporation from the milk (or milk replacer) fat. The relatively low stearic concentration in perirenal fat in all groups (around 15%) suggest low ruminal activity. Determination of C15:0, C17:0 and C17:1 in perirenal fat could help differentiate the feeding system of young kids and might be useful for identification purposes of goat kid carcasses. Kew~'or&: Goat kid: Milk replacer; Artificial rearing; Fatty acids, odd-numbered
1. Introduction In Spain and other Mediterranean countries, goat meat from milk-fed kids is traditionally in high demand. Kids from the Verata breed are among the most valued. Although this breed can be utilized as milk producers because of its good milk production performances (Rota et al., 1993), traditionally milk production has been low since the main objective was kid-meat production, that was obtained from naturally nursing kids. In recent years, artificial rearing of goat kids has become more important and allows commercialization of milk and kid meat, with higher economic returns. Utilization of milk and milk replacers has been stud*Con'espondence author. 0921-4488/94/$07.00 :t'~ 1994 Elsevier Science B.V. All rights reserved SSDI092 I - 4 4 8 8 ( 93 ) E 0 1 0 7 - 4
ied in lambs, calves (Walker and Stokes, 1970; Penning et al., 1977; Neergaard, 1980; Abe et al., 1981 ) and young goats (Sanz Sampelayo et al., 1990). Young pre-ruminant animals can utilize fat, protein and carbohydrates of milk as efficiently as can young mammals of other species (Porter, 1969). Although growth and carcass characteristics are not negatively affected by milk-replacer administration in Verata goats (Rojas et al., 1992), some consumers claim lower meat acceptability, which limits the generalization of artificial rearing of goat kids (Rojas, 1990). The objective of this paper was to study the relationship between milk feeding systems and fatty acid composition of goat kid tissues, and to assess the possibility of using the analysis of fatty acids to differentiate the origin of kid meat.
62
A. Rojas et al. / Small Ruminant Research 14 (1994) 6 1 ~ 6
2. Materials and methods
We used 48 Verata goat kids (24 males and 24 females) that were randomly distributed in four groups of 12 animals, with six of each gender. Animals were separated from their mothers 2 d after birth and were kept in separated cages according to feeding treatment. Temperature was 2 2 _ 3 ° C and relative humidity around 60%. Group 1 received commercial milk replacer solution ( 17% solids, w/v) ; group 2 received milk replacer at the solution 17% solids for 21 d and 23% solids for the remaining time; group 3 received 12% solids ( w / v ) for 2 wk, then 17% for 2 wk and 23% for the remaining time. Commercial milk replacer included animal and vegetable lipids in its formulation. An extra group (group N) received natural goat milk and was used as control. In all cases feeding was done ad libitum twice a day (at 9 a.m. and 7 p.m., approx.). Naturally nursed kid were allowed to suckle from their mothers and then were separated again. Milk replacer was given by means of a bottle. Temperature of the milk replacer solution was 32 + I°C. Goat milk chemical composition was determined weekly by conventional laboratory techniques; N content by the Kjeldahl method; fat by the Gerber method (Egan et al., 1987); ash content incineration in a muffle furnace at 600°C (AOAC, 1984). Chemical composition of milk replacer was taken from the supplier correcting for total DM. In all cases, energy (MJ/1) determination was carried out in an adiabatic bomb calorimeter on freeze-dried samples (IKA Calorimeter C4000, Janke and Kunkel). Animals were weighed prior to slaughter at 45 d of age. Carcass weight was also recorded and samples from perirenal fat were taken, vacuum packed and kept frozen at - 2 2 ° C until analyses for fatty acid composition. Lipids from the perirenal fat depot were extracted by an automatic Soxhlet apparatus (Btichi-810) using petroleum ether (b.p. 40--60°C) and then methylated in the presence of sulfuric acid for gas chromatography identification of fatty acids (AOAC, 1984). This was done on a 5890 Hewlett Packard gas chromatograph with a 2 m OV-1 column. The oven temperature was 200°C, the injector and detector were maintained at 220°C. Nitrogen carrier gas flow was 24 Ml/min. All
fatty acids were identified by means of external standards provided by Sigma (St. Louis, MO, USA). The data were analyzed by a four (feeding regimen) X two (males and females) factorial analysis of variance. Data were presented as means and standard deviations for individual treatment groups. Statistical significance of the difference between means was assessed by the multiple range test of Tukey.
3. Results and discussion
Chemical composition and gross energy of goat milk and commercial milk replacer solutions used for this experiment are shown in Table 1. There was no effect of sex or feeding regime on live weight at slaughter (around 8.8 kg in all groups) and carcass weight (around 4.9 kg), although naturally nursed kids had values 5-7% higher in all cases. In a previous paper (Rojas et al., 1992) we reported higher fat content in dissected carcasses from naturally fed kids ( P < 0.01). This may be associated with better meat acceptability (and market price) of the meat, since some portions of the fat (particularly intramuscular fat) is closely related to meat quality characteristics (flavor, juiciness) and in general there is a direct relationship between total carcass fat and intramuscular lipids (L6pez-Bote, 1992). Fatty acid composition of the perirenal fat showed differences between groups. Means and standard deviations of the percentage of fatty acids in the different feeding groups for males and females are shown in Table 2. There were some minor fatty acids that were not identified and appear in the table as UFA (unidentified fatty acids). There was no effect associated with sex. The fatty acid composition of perirenal fat tended to reflect dietary fatty acid concentration (Table 3 ). This is in agreement with Jenkins et al. (1986) who reported a direct relationship between fatty acid composition of major blood plasma, liver and perirenal lipids and dietary fatty acid concentration in young pre-ruminants. Also, Semlek and Riley (1975) found that changes in nutrition and ruminant physiology, which occur during growth,
A. Rojas et aL / Small Ruminant Research 14 (1994) 6 1 4 6
63
Table 1 Chemical composition and gross energy content of goat milk and commercial milk replacers fed to experimental groups 1, 2 and 3 (expressed as percentage) Goat milk
DM CP Fat Ash Ca P Gross energy ( M J / l )
Milk replacer
1
2
3
14.00 3.55 4.53 1.19 -
12.00 2.93 2.85 0.77 0.12 0.09
17.00 4.15 4.04 1.09 0.17 0.13
23.00 5.61 5.47 1.47 0.23 0.18
3.71
3.04
4.31
5.83
Table 2 Means and standard deviations of fatty acid composition of the per±renal fat from Vemta goat kids fed with commercial milk replacers (groups 1-3) or with natural goat milk (group N)' Group l
Group 2
Group 3
Group N
4.33±0.56 10.90 ± 0.57 0.49 ± 0.12 a 22.89 ± 0.65 2.69±0.19 0.87±0.17 a 0.48 ± 0.12 a 12.38 ± 0.49 35.24 ± 1.23 4.98 ± 0.71 4.75 ± 0.47 h
1.38±0.13 8.35 ± 0.24 0.74 ± 0.08 h 26.59 ± 1.00 2.93 ±0.12 1.25+_0.12 h 0.83 ± 0.08 t' 14.63 ± 0.98 34.94 ± 1.37 3.92 ± 0.51 4.44 ± 0.84 t'
3.62 + 0.32 10.46 ± 0.40 0.52 + 0.06 a 24.00 ± 1.17 2.94+0.25 0.83 + 0.12 a 0.50 ± 0.14 a 12.68 ± 1.00 36.58 ± 2.42 4.00±0.46 3.87 ± 0.72 r'
1.40 ± 0.06 8.64 ± 0.33 0.81 ± 0.11" 26.56 ± 0.63 2.76_+0.07 1.22 + 0.09 b 1.27_+0.18 b 15.36 ± 0.35 32.77 ± 0.9 I 3.23 ± 0.51 5.98 ± 0.97 a
males C12:0 C 14:0 C 15:0 C 16:0 C16:1 C17:0 C 17:1 CI 8:0 C 18: l C 18:2 UFA 2
3.40+_0.52 10.61 ± 0.42 0.46 ± 0.06 a 24.43 ± 0.19 2.91 ±0.07 0.79 ± 0.07 a 0.40 ± 0.04 a 14.86 ± 0.73 35.35 ± 0.17 4.02 ± 0.23 2.77 ± 0.38 a
2.67±0.24 10.04 ± 0.29 0.45 ± 0.10 a 23.25 ± 0.45 3.19±0.15 0.81 ±0.14 a 0.43 ± 0.02 a 14.19 ± 0.81 36.18 ± 0.44 4.83 ± 0.46 3.96 ± 0.56 ~' females
C 12:0 C 14:0 C 15:0 C 16:0 C16:1 C 17:0 C17:1 C 18:0 C 18:1 C18:2 UFA 2
2.73 + 0.45 9.26 _+0.93 0.51 ± 0.04" 24.40 + 0.23 3.41 ±0.32 0.80 ± 0.09" 0.62±0.11" 12.46 ± 0.58 35.69 ± 0.73 5.14 ± 0.64 4.98 ± 0.73"
3.09 + 0.31 10.52 + 0.19 0.47 ± 0.05 a 23.56 _+0.28 3.21 _+0.04 0.84 + 0.11 a 0.41 ±0.04 a 13.93 _+0.87 35.98 ± 0.24 4.31 ±0.15 3.68 ± 0.62 h
EAII results are expressed as a percentage. 2UFA = unidentified fatty acids. ~'bMeans with different superscript within row are statistically different (P < 0.05 ).
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A. Rojas et al. / Small Ruminant Research 14 (1994) 61-66
Table 3 Means and standard deviations o f fatty acids in g o a t milk and c o m mercial milk replacers used in the e x p e r i m e n t ' G o a t milk
Milk replacer
C12:0 C14:0 C15:0 C16:0 C16:1 C 17:0 C17:1
5.08 + 0.96 a 11.68 _+ 0.80 1.04 + 0.43 a 32.01 -t- 1.27 a 2.47+0.41 a 1.06 5:0.25 a 1.13 + 0.07 a
15.47 + 0.30 b 10.26 + 0.24 0.59 + 0.12 b 23.88 + 0 . 4 1 b 3.77+0.18 ° 0.57 + 0.11 b 0.61 + 0 . 1 1 b
C18:0 C18:1
10.35 ± 1.48 30.15 + 1.14 a
12.71 + 0 . 3 8 26.67 + 0 . 2 3 b
C 18:2
3.49 + 0.32 a
4.45 + 0.14 °
~All results are expressed as a percentage. a'bMeans with different superscript within a r o w are statistically different ( P < 0 . 0 1 ) .
are the main reasons for changes in the fatty acid composition of fat depots in ruminants. The C 16 and C 18 components (palmitic, C 16:0; palmitoleic, C16:1; stearic, C18:0; oleic, C18:1 and linoleic, C 18:2) together comprised in all cases the greatest proportion of fatty acids that were present in perirenal fat, although there were no statistical differences in the proportions of these fatty acids between the four feeding groups. Concentration of C18:0 in perirenal fat was relatively low (around 15% in all cases) compared with common values reported for ruminants. Sauvant et al. (1979) observed in young goats that after weaning perirenal fat becomes rich in saturated fatty acids in general, and stearic acids in particular rise from 19.4 to 28.26%. Also, Semlek and Riley (1975), in a study of fatty acid composition of perirenal fat of growing lambs, showed an increasing concentration of C18:0 from around 15% in neonatal lambs to approx. 30% at 4.5 months of age. The relative low stearic acid concentration compared with common values reported for adult ruminants suggests low overall ruminal activity in all cases. It is also remarkable that long chain saturated fatty acids (C16:0 and C18:0) had in general higher concentrations in naturally nursed than in artificially reared kids, and unsaturated (C 16:1, C 18:1 and C18:2) fatty acids had lower values. The index (C16:0+C18:0/C16:1 +C18:1 +C18:2) was lower in artificially reared than in naturally nursed kids (P<0.01), which suggests higher microbial activity
in naturally ted kids. Also, the tendency to higher proportions of unidentified fatty acids in naturally fed kids (Table 2) suggests higher microbial activity in kids nursed with their mothers, since bacterial metabolism may produce trace amounts of a variety of non-common fatty acids in animal tissues (Sauvant et al., 1979; Minato et al., 1988). Concentration of medium chain fatty acids in perirenal fat was relatively high compared to common values reported for ruminants (Sauvant et al., 1979; Semlek and Riley, 1975; Byers and Schelling, 1988). In all cases, animals that received goat milk had lower lauric (C12:0) and myristic (C14:0) acids than groups that received milk replacer. However, this difference did not reach significant levels, probably due to the relatively small number of animals and variation. When considering both genders together, differences in C 12:0 and C14:0 became apparent (P < 0.01 ). Differences in medium chain fatty acids in perirenal fat of artificially reared kids may be due to the high concentration of C12:0 in commercial milk replacers (15.47%) in comparison to goat milk (5.08%). Odd-numbered fatty acid (C15:0, C17:0 and C17:1) concentrations in perirenal fat were higher in animals that received goat milk than in those that received milk replacer in all cases (P < 0.05). Odd-carbon fatty acids constitute a very small proportion of the total fatty acid composition of animal fat and have been proposed to derive from fatty acid ofrumen microorganisms (Byers and Schelling, 1988; Minato et al., 1988; O'Kelly and Spiers, 1991 ) or from condensation of propionate as a result of bacterial fermentation in the rumen (James et al., 1956; Duncan and Garton, 1978; Massart-Le6n et al., 1983). Enhanced amounts of odd-numbered fatty acids have been reported in adipose tissue of lambs and goats (Linzell et al., 1976; Duncan and Garton, 1978) when they were fed cereal rich diets. Kurtz (1965) reported that neonatal lambs with no functional rumen and fed commercial milk replacers, have smaller concentrations or even non-detectable amounts of odd fatty acids in fat depots than adults, and that proportion rise when the rumen becomes functional. Also, Semlek and Riley (1975), in an experiment with growing lambs, found a small proportion of C15 and C17 in fatty tissues of newborn lambs (0.08% and 0.49% respectively). The proportion of odd-chain fatty acids increased gradually with age up to 0.56% and 1.44%, respectively, when the rumen became func-
A. Rojas et al. / Small Ruminant Research 14 (1994) 6 1 ~ 6
tional. Sauvant et al. (1979) reported an increase of odd-numbered fatty acid concentration in goat kid fat after weaning, which they attributed to ruminal activity. In our experiment, concentrations of odd-numbered fatty acids in naturally nursed kids are close to data reported by these authors for fully weaned ruminants. However, as previously discussed, ruminal activity in our experiment seemed to be relatively low in all groups, and consequently it is questioned whether the relatively high concentration of odd-numbered fatty acids in animal tissues may have exclusively ruminal origin. On the other hand, both goat milk and commercial milk replacers contain relatively high proportions of odd-numbered fatty acids (Table 3), the concentration being higher in natural milk ( P < 0 . 0 1 ) . Since young pre-ruminant animals utilize tat without much digestive modification, as in non-ruminant mammals, it is reasonable to assume that the odd fatty acids detected in depot fat of young kids may have an origin, to some extent, in the composition of the milk. The concentration of odd-numbered fatty acids in milk replacer was approx. 45% less than the concentration of these fatty acids in goat milk, and the concentration in animal tissues of artificially reared kids is approx. 42% lower than in naturally nursed animals. This small difference suggests an important role of nutrition on odd-numbered fatty acid concentration of fat tissue in young pre-ruminants. The possible limited higher ruminal activity in naturally led kids previously propossed, based on the tendency to the more elevated saturation of the lipids and higher concentration of unidentified fatty acids in perirenal fat, may help to widen the difference in oddnumbered fatty acid concentration between naturally fed and artiticially reared kids. Probably the close presence of the mother in naturally fed kids facilitates natural inoculation of the kid rumen with microbes and also may promote the natural tendency in the kid to take small amounts of solid feeds. This helps develop rumen functionality quicker in naturally fed kids than in artificially reared and could aid to some extent the higher concentration of odd-numbered fatty acids in fat depots (Hamada et al., 1977; Bonhomme, 1990). Consequently, we propose that the determination of C15:0, C17:0 and C17:1 fatty acids could provide a reliable method to differentiate raising systems of young goat kids.
65
References Abe, M., Takase, O., Shibui, H. and lriki, T., 1981. Neonatal diarrhoea in calves given milk substitutes differing in fat source and fed by different procedures. Br. J. Nutr., 46: 543-548. AOAC, 1984. Official Methods of Analysis. 14th edn. Assoc~ Offic. Agric. Chem. Washington, DC, USA. Bonhomme, A., 1990. Rumen ciliates: their metabolism and relationship with bacteria and their host. Anim. Feed Sci. Technol., 30: 203-266. Byers, F.M. and Schelling, G.T., 1988. Lipids in ruminant nutrition. In: D.C. Church (editor). The Ruminant Animal. Digestive Physiology and Nutrition. Prentice Hall, Englewood Cliffs, N J, pp. 298-312 Duncan, W.RH. and Garton, G.A., 1978. Differences in the proportions of branched-chain fatty acids in subcutaneous triacylglycerols of barley-fed ruminants. Br. J. Nutr, 40:29 34. Egan, H., Kirk, R.S. and Sawyer, R., 1987. An~ilisis qufiuico de alimentos de Pearson. (Chemical analysis of feeds after Pearson. ) Compafifa editorial continental SA. M6xico, pp. 443-518. Hamada, T., Maeda, S. and Kameoka, K., 1977. Factors influencing growth of rumen, liver and other organs in kid weaned from milk replacers to solid foods. J. Dairy Res., 59:11 t0-1118. James, A.T., Peters, G. and Lauryssens, M., 1956. The metabolism of propionic acid. Biochem. J., 64:726-73 I Jenkins, K.J., Kramer, J.K.G. and Emmons, D.B., 1986. Effect of lipids in milk replacers on calf performance and lipids in blood plasma, liver and perirenal fat. J. Dairy Sci., 69: 447459. Kurtz, F.E., 1965. The lipids of milk: composition and properties. Fundamentals of dairy chemistry. AVI Publishing Inc., Westport. Linzell, J.L., Mepham, T.B. and Peaker, M., 1976. The secretion of citrate into milk. J. Physiol., 260:739 742. L6pez-Bote, C., 1992. Calidad de la came. ( Properties of Meat. ) In: Martin, S. (Editor), Manual Prfictico de la Came. Martin Macias Publisher, Madrid, pp. 143-180. Massart-Le6n. A.M., Roets, E., Peeters, G. and Verbeke, R., 1983. Propionate for fatty acid synthesis by the mammary gland of the lactating goat. J. Dairy Sci., 66:1445-1454 Minato, H.; Ishibashi, S. and Hamaoka, T., 1988. Cellular fatty acid and sugar composition of representative strains of rumen bacleria. J. Gen. Appl. Microbiol. 34: 303-319. Neergaard, L., 1980. Influence of specially extracted soya meal on nitrogen and energy metabolism in the preruminant calf. In: L.E. Mount (Editor), Energy Metabolism. Proc. 8th Symposium on Energy metabolism. Butterworth, London, pp. 43~47. O'Kelly, J.C. and Spiers, W.G., 1991. Influence of host diet on the concentrations of fatty acids in rumen bacteria from cattle. Australian J. Agric. Res., 42:243-252 Penning, P.D., Penning, 1. and Treacher, T., 1977. The effect of temperature and method of feeding on the digestibility of two milk substitutes and on the performance of the lambs. J. Agric. Sci. Cambr., 88: 579-589. Porter, J.W.G., 1969. Digestion in the pre-ruminant animal. Proc. Nutr. Soc., 28: 115-12t. Rojas, A. 1990. Contribuci6n al estudio de la lactancia artilicial en la especie caprina. ( Artificial rearing of goat kids. ) Ph. D. Thesis. Universidad de Extremadura, 260 pp.
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A. Rojas et al. / Small Ruminant Research 14 (1994) 61-66
Rojas, A., Rota, A., Martin, L., Rodriguez, P. and Tovar,J., 1992. Influencia del tipo de lactancia en cabritos sobre las caracterfsticas de su canal al sacrificio. (Effect of the type of lactation in young kids on the carcass characteristics.) Arch. Zootech., 41: 131-139. Rota, A., Rodriguez, P., Rojas, A., Martin, L. and Tovar, J., 1993. Evoluci6n de la cantidad y calidad de la leche de cabra Verata a 1o largo de la lactaci6n. (Evolution of milk quantity and quality in the Verata breed along the lactation period.) Arch. Zootech., in press. Sanz Sampelayo, M.R., Hemandez-Clua, O.D., Naranjo, J.A., Gil, F. and Boza, J. 1990. Utilization of goat milk vs. milk replacer
for Granadina goat kids. Small Rumin. Res., 3: 37-46. Sauvant, D., Bas, P. and Morand-Fehr, P., 1979. Production de cheveaux lourds: II.- Influence du niveau d'ingestion de lait sur les performances et la composition du tissu adipeux. (Production of heavy goat meat. II. Influence of level of milk feeding on performance and composition of adipose tissue.) Ann. Zootech., 28: 73-92. Semlek, M.A. and Riley, M.L., 1975. Fatty acid composition in growing lambs. Proceedings, Western Section, American Society of Animal Science, 26: 58-59. Walker, D.M. and Stokes, G.B., 1970. The nutritive value of fat in the diet of the milk-fed lamb. Br. J. Nutr., 24: 425-433.
Resumen Rojas, A., L6pez-Bote, C., Rota, A., Martfn, L., Rodriguez, P.L. and Tovar, J.J., 1994. Fatty acid composition of Verata goat kids fed either goat milk or commercial milk replacer. Small Rumin. Res., 14: 61~6. Se ha estudiado la composici6n en dcidos grasos de la grasa perirenal de cabritos de raza Verata alimentados con leche natural o con tres concentraciones de lactorremplazantes. No se hart encontrado efectos asociados al sexo. La dnica diferencia se encontr6 en los ficidos pentadecanoico (C15:0), heptadecanoico (C17:0) y heptadecenoico (Cl7:l), que alcanzaron valores mds elevados en animales de lactancia natural (P < 0,05 ). En el trabajo se discute el posible origen de estos ~icidos grasos, considerando el posible papel de los microorganismos del rumen o la incorporaci6n directa a trav6s de la grasa de la leche. La baja concentraci6n de dcido estefirico (alrededor del 15%) hace suponer una baja actividad ruminal. La determinaci6n de dcidos grasos impares puede permitir identificar el tipo de alimentaci6n suministrada a los cabritos.
Small Ruminant Research 14 (1994) 61-66
Fatty acid composition of Verata goat kids fed either goat milk or commercial milk replacer A. Rojas ~', C. L6pez-Bote b'*, A. Rota a, L. Martin a, P.L. Rodrfguez a, J.J.
Tovar a ~Departamento de Zootecnia, Facultad de Veterinaria, Universidad de Extremadura, 10071 Cdceres, Spain hDepartamento de Produccidn Animal, Facultad de Veterinaria, Universidad Complutense de Madrid. 28040 Madrid. Spain Accepted 3 September 1993
Abstract
Fatty acid composition of perirenal fat of young Verata male and female kids fed with natural milk and with three concentrations of commercial milk replacer was studied. There was no effect associated with sex. In each gender the only statistical difference in fatty acid composition between the tour feeding groups under study were pentadecanoic acid (C15:0), heptadecanoic acid (C17:0) and heptadecenoic acid (C17:l) which were higher in all cases in naturally fed kids (P < 0.05). The origin of oddnumbered fatty acids in depot fats of goat kids is discussed considering the possible role of microbial rumen synthesis in goat kids or the direct incorporation from the milk (or milk replacer) fat. The relatively low stearic concentration in perirenal fat in all groups (around 15%) suggest low ruminal activity. Determination of C15:0, C17:0 and C17:1 in perirenal fat could help differentiate the feeding system of young kids and might be useful for identification purposes of goat kid carcasses. Kew~'or&: Goat kid: Milk replacer; Artificial rearing; Fatty acids, odd-numbered
1. Introduction In Spain and other Mediterranean countries, goat meat from milk-fed kids is traditionally in high demand. Kids from the Verata breed are among the most valued. Although this breed can be utilized as milk producers because of its good milk production performances (Rota et al., 1993), traditionally milk production has been low since the main objective was kid-meat production, that was obtained from naturally nursing kids. In recent years, artificial rearing of goat kids has become more important and allows commercialization of milk and kid meat, with higher economic returns. Utilization of milk and milk replacers has been stud*Con'espondence author. 0921-4488/94/$07.00 :t'~ 1994 Elsevier Science B.V. All rights reserved SSDI092 I - 4 4 8 8 ( 93 ) E 0 1 0 7 - 4
ied in lambs, calves (Walker and Stokes, 1970; Penning et al., 1977; Neergaard, 1980; Abe et al., 1981 ) and young goats (Sanz Sampelayo et al., 1990). Young pre-ruminant animals can utilize fat, protein and carbohydrates of milk as efficiently as can young mammals of other species (Porter, 1969). Although growth and carcass characteristics are not negatively affected by milk-replacer administration in Verata goats (Rojas et al., 1992), some consumers claim lower meat acceptability, which limits the generalization of artificial rearing of goat kids (Rojas, 1990). The objective of this paper was to study the relationship between milk feeding systems and fatty acid composition of goat kid tissues, and to assess the possibility of using the analysis of fatty acids to differentiate the origin of kid meat.
62
A. Rojas et al. / Small Ruminant Research 14 (1994) 6 1 ~ 6
2. Materials and methods
We used 48 Verata goat kids (24 males and 24 females) that were randomly distributed in four groups of 12 animals, with six of each gender. Animals were separated from their mothers 2 d after birth and were kept in separated cages according to feeding treatment. Temperature was 2 2 _ 3 ° C and relative humidity around 60%. Group 1 received commercial milk replacer solution ( 17% solids, w/v) ; group 2 received milk replacer at the solution 17% solids for 21 d and 23% solids for the remaining time; group 3 received 12% solids ( w / v ) for 2 wk, then 17% for 2 wk and 23% for the remaining time. Commercial milk replacer included animal and vegetable lipids in its formulation. An extra group (group N) received natural goat milk and was used as control. In all cases feeding was done ad libitum twice a day (at 9 a.m. and 7 p.m., approx.). Naturally nursed kid were allowed to suckle from their mothers and then were separated again. Milk replacer was given by means of a bottle. Temperature of the milk replacer solution was 32 + I°C. Goat milk chemical composition was determined weekly by conventional laboratory techniques; N content by the Kjeldahl method; fat by the Gerber method (Egan et al., 1987); ash content incineration in a muffle furnace at 600°C (AOAC, 1984). Chemical composition of milk replacer was taken from the supplier correcting for total DM. In all cases, energy (MJ/1) determination was carried out in an adiabatic bomb calorimeter on freeze-dried samples (IKA Calorimeter C4000, Janke and Kunkel). Animals were weighed prior to slaughter at 45 d of age. Carcass weight was also recorded and samples from perirenal fat were taken, vacuum packed and kept frozen at - 2 2 ° C until analyses for fatty acid composition. Lipids from the perirenal fat depot were extracted by an automatic Soxhlet apparatus (Btichi-810) using petroleum ether (b.p. 40--60°C) and then methylated in the presence of sulfuric acid for gas chromatography identification of fatty acids (AOAC, 1984). This was done on a 5890 Hewlett Packard gas chromatograph with a 2 m OV-1 column. The oven temperature was 200°C, the injector and detector were maintained at 220°C. Nitrogen carrier gas flow was 24 Ml/min. All
fatty acids were identified by means of external standards provided by Sigma (St. Louis, MO, USA). The data were analyzed by a four (feeding regimen) X two (males and females) factorial analysis of variance. Data were presented as means and standard deviations for individual treatment groups. Statistical significance of the difference between means was assessed by the multiple range test of Tukey.
3. Results and discussion
Chemical composition and gross energy of goat milk and commercial milk replacer solutions used for this experiment are shown in Table 1. There was no effect of sex or feeding regime on live weight at slaughter (around 8.8 kg in all groups) and carcass weight (around 4.9 kg), although naturally nursed kids had values 5-7% higher in all cases. In a previous paper (Rojas et al., 1992) we reported higher fat content in dissected carcasses from naturally fed kids ( P < 0.01). This may be associated with better meat acceptability (and market price) of the meat, since some portions of the fat (particularly intramuscular fat) is closely related to meat quality characteristics (flavor, juiciness) and in general there is a direct relationship between total carcass fat and intramuscular lipids (L6pez-Bote, 1992). Fatty acid composition of the perirenal fat showed differences between groups. Means and standard deviations of the percentage of fatty acids in the different feeding groups for males and females are shown in Table 2. There were some minor fatty acids that were not identified and appear in the table as UFA (unidentified fatty acids). There was no effect associated with sex. The fatty acid composition of perirenal fat tended to reflect dietary fatty acid concentration (Table 3 ). This is in agreement with Jenkins et al. (1986) who reported a direct relationship between fatty acid composition of major blood plasma, liver and perirenal lipids and dietary fatty acid concentration in young pre-ruminants. Also, Semlek and Riley (1975) found that changes in nutrition and ruminant physiology, which occur during growth,
A. Rojas et aL / Small Ruminant Research 14 (1994) 6 1 4 6
63
Table 1 Chemical composition and gross energy content of goat milk and commercial milk replacers fed to experimental groups 1, 2 and 3 (expressed as percentage) Goat milk
DM CP Fat Ash Ca P Gross energy ( M J / l )
Milk replacer
1
2
3
14.00 3.55 4.53 1.19 -
12.00 2.93 2.85 0.77 0.12 0.09
17.00 4.15 4.04 1.09 0.17 0.13
23.00 5.61 5.47 1.47 0.23 0.18
3.71
3.04
4.31
5.83
Table 2 Means and standard deviations of fatty acid composition of the per±renal fat from Vemta goat kids fed with commercial milk replacers (groups 1-3) or with natural goat milk (group N)' Group l
Group 2
Group 3
Group N
4.33±0.56 10.90 ± 0.57 0.49 ± 0.12 a 22.89 ± 0.65 2.69±0.19 0.87±0.17 a 0.48 ± 0.12 a 12.38 ± 0.49 35.24 ± 1.23 4.98 ± 0.71 4.75 ± 0.47 h
1.38±0.13 8.35 ± 0.24 0.74 ± 0.08 h 26.59 ± 1.00 2.93 ±0.12 1.25+_0.12 h 0.83 ± 0.08 t' 14.63 ± 0.98 34.94 ± 1.37 3.92 ± 0.51 4.44 ± 0.84 t'
3.62 + 0.32 10.46 ± 0.40 0.52 + 0.06 a 24.00 ± 1.17 2.94+0.25 0.83 + 0.12 a 0.50 ± 0.14 a 12.68 ± 1.00 36.58 ± 2.42 4.00±0.46 3.87 ± 0.72 r'
1.40 ± 0.06 8.64 ± 0.33 0.81 ± 0.11" 26.56 ± 0.63 2.76_+0.07 1.22 + 0.09 b 1.27_+0.18 b 15.36 ± 0.35 32.77 ± 0.9 I 3.23 ± 0.51 5.98 ± 0.97 a
males C12:0 C 14:0 C 15:0 C 16:0 C16:1 C17:0 C 17:1 CI 8:0 C 18: l C 18:2 UFA 2
3.40+_0.52 10.61 ± 0.42 0.46 ± 0.06 a 24.43 ± 0.19 2.91 ±0.07 0.79 ± 0.07 a 0.40 ± 0.04 a 14.86 ± 0.73 35.35 ± 0.17 4.02 ± 0.23 2.77 ± 0.38 a
2.67±0.24 10.04 ± 0.29 0.45 ± 0.10 a 23.25 ± 0.45 3.19±0.15 0.81 ±0.14 a 0.43 ± 0.02 a 14.19 ± 0.81 36.18 ± 0.44 4.83 ± 0.46 3.96 ± 0.56 ~' females
C 12:0 C 14:0 C 15:0 C 16:0 C16:1 C 17:0 C17:1 C 18:0 C 18:1 C18:2 UFA 2
2.73 + 0.45 9.26 _+0.93 0.51 ± 0.04" 24.40 + 0.23 3.41 ±0.32 0.80 ± 0.09" 0.62±0.11" 12.46 ± 0.58 35.69 ± 0.73 5.14 ± 0.64 4.98 ± 0.73"
3.09 + 0.31 10.52 + 0.19 0.47 ± 0.05 a 23.56 _+0.28 3.21 _+0.04 0.84 + 0.11 a 0.41 ±0.04 a 13.93 _+0.87 35.98 ± 0.24 4.31 ±0.15 3.68 ± 0.62 h
EAII results are expressed as a percentage. 2UFA = unidentified fatty acids. ~'bMeans with different superscript within row are statistically different (P < 0.05 ).
64
A. Rojas et al. / Small Ruminant Research 14 (1994) 61-66
Table 3 Means and standard deviations o f fatty acids in g o a t milk and c o m mercial milk replacers used in the e x p e r i m e n t ' G o a t milk
Milk replacer
C12:0 C14:0 C15:0 C16:0 C16:1 C 17:0 C17:1
5.08 + 0.96 a 11.68 _+ 0.80 1.04 + 0.43 a 32.01 -t- 1.27 a 2.47+0.41 a 1.06 5:0.25 a 1.13 + 0.07 a
15.47 + 0.30 b 10.26 + 0.24 0.59 + 0.12 b 23.88 + 0 . 4 1 b 3.77+0.18 ° 0.57 + 0.11 b 0.61 + 0 . 1 1 b
C18:0 C18:1
10.35 ± 1.48 30.15 + 1.14 a
12.71 + 0 . 3 8 26.67 + 0 . 2 3 b
C 18:2
3.49 + 0.32 a
4.45 + 0.14 °
~All results are expressed as a percentage. a'bMeans with different superscript within a r o w are statistically different ( P < 0 . 0 1 ) .
are the main reasons for changes in the fatty acid composition of fat depots in ruminants. The C 16 and C 18 components (palmitic, C 16:0; palmitoleic, C16:1; stearic, C18:0; oleic, C18:1 and linoleic, C 18:2) together comprised in all cases the greatest proportion of fatty acids that were present in perirenal fat, although there were no statistical differences in the proportions of these fatty acids between the four feeding groups. Concentration of C18:0 in perirenal fat was relatively low (around 15% in all cases) compared with common values reported for ruminants. Sauvant et al. (1979) observed in young goats that after weaning perirenal fat becomes rich in saturated fatty acids in general, and stearic acids in particular rise from 19.4 to 28.26%. Also, Semlek and Riley (1975), in a study of fatty acid composition of perirenal fat of growing lambs, showed an increasing concentration of C18:0 from around 15% in neonatal lambs to approx. 30% at 4.5 months of age. The relative low stearic acid concentration compared with common values reported for adult ruminants suggests low overall ruminal activity in all cases. It is also remarkable that long chain saturated fatty acids (C16:0 and C18:0) had in general higher concentrations in naturally nursed than in artificially reared kids, and unsaturated (C 16:1, C 18:1 and C18:2) fatty acids had lower values. The index (C16:0+C18:0/C16:1 +C18:1 +C18:2) was lower in artificially reared than in naturally nursed kids (P<0.01), which suggests higher microbial activity
in naturally ted kids. Also, the tendency to higher proportions of unidentified fatty acids in naturally fed kids (Table 2) suggests higher microbial activity in kids nursed with their mothers, since bacterial metabolism may produce trace amounts of a variety of non-common fatty acids in animal tissues (Sauvant et al., 1979; Minato et al., 1988). Concentration of medium chain fatty acids in perirenal fat was relatively high compared to common values reported for ruminants (Sauvant et al., 1979; Semlek and Riley, 1975; Byers and Schelling, 1988). In all cases, animals that received goat milk had lower lauric (C12:0) and myristic (C14:0) acids than groups that received milk replacer. However, this difference did not reach significant levels, probably due to the relatively small number of animals and variation. When considering both genders together, differences in C 12:0 and C14:0 became apparent (P < 0.01 ). Differences in medium chain fatty acids in perirenal fat of artificially reared kids may be due to the high concentration of C12:0 in commercial milk replacers (15.47%) in comparison to goat milk (5.08%). Odd-numbered fatty acid (C15:0, C17:0 and C17:1) concentrations in perirenal fat were higher in animals that received goat milk than in those that received milk replacer in all cases (P < 0.05). Odd-carbon fatty acids constitute a very small proportion of the total fatty acid composition of animal fat and have been proposed to derive from fatty acid ofrumen microorganisms (Byers and Schelling, 1988; Minato et al., 1988; O'Kelly and Spiers, 1991 ) or from condensation of propionate as a result of bacterial fermentation in the rumen (James et al., 1956; Duncan and Garton, 1978; Massart-Le6n et al., 1983). Enhanced amounts of odd-numbered fatty acids have been reported in adipose tissue of lambs and goats (Linzell et al., 1976; Duncan and Garton, 1978) when they were fed cereal rich diets. Kurtz (1965) reported that neonatal lambs with no functional rumen and fed commercial milk replacers, have smaller concentrations or even non-detectable amounts of odd fatty acids in fat depots than adults, and that proportion rise when the rumen becomes functional. Also, Semlek and Riley (1975), in an experiment with growing lambs, found a small proportion of C15 and C17 in fatty tissues of newborn lambs (0.08% and 0.49% respectively). The proportion of odd-chain fatty acids increased gradually with age up to 0.56% and 1.44%, respectively, when the rumen became func-
A. Rojas et al. / Small Ruminant Research 14 (1994) 6 1 ~ 6
tional. Sauvant et al. (1979) reported an increase of odd-numbered fatty acid concentration in goat kid fat after weaning, which they attributed to ruminal activity. In our experiment, concentrations of odd-numbered fatty acids in naturally nursed kids are close to data reported by these authors for fully weaned ruminants. However, as previously discussed, ruminal activity in our experiment seemed to be relatively low in all groups, and consequently it is questioned whether the relatively high concentration of odd-numbered fatty acids in animal tissues may have exclusively ruminal origin. On the other hand, both goat milk and commercial milk replacers contain relatively high proportions of odd-numbered fatty acids (Table 3), the concentration being higher in natural milk ( P < 0 . 0 1 ) . Since young pre-ruminant animals utilize tat without much digestive modification, as in non-ruminant mammals, it is reasonable to assume that the odd fatty acids detected in depot fat of young kids may have an origin, to some extent, in the composition of the milk. The concentration of odd-numbered fatty acids in milk replacer was approx. 45% less than the concentration of these fatty acids in goat milk, and the concentration in animal tissues of artificially reared kids is approx. 42% lower than in naturally nursed animals. This small difference suggests an important role of nutrition on odd-numbered fatty acid concentration of fat tissue in young pre-ruminants. The possible limited higher ruminal activity in naturally led kids previously propossed, based on the tendency to the more elevated saturation of the lipids and higher concentration of unidentified fatty acids in perirenal fat, may help to widen the difference in oddnumbered fatty acid concentration between naturally fed and artiticially reared kids. Probably the close presence of the mother in naturally fed kids facilitates natural inoculation of the kid rumen with microbes and also may promote the natural tendency in the kid to take small amounts of solid feeds. This helps develop rumen functionality quicker in naturally fed kids than in artificially reared and could aid to some extent the higher concentration of odd-numbered fatty acids in fat depots (Hamada et al., 1977; Bonhomme, 1990). Consequently, we propose that the determination of C15:0, C17:0 and C17:1 fatty acids could provide a reliable method to differentiate raising systems of young goat kids.
65
References Abe, M., Takase, O., Shibui, H. and lriki, T., 1981. Neonatal diarrhoea in calves given milk substitutes differing in fat source and fed by different procedures. Br. J. Nutr., 46: 543-548. AOAC, 1984. Official Methods of Analysis. 14th edn. Assoc~ Offic. Agric. Chem. Washington, DC, USA. Bonhomme, A., 1990. Rumen ciliates: their metabolism and relationship with bacteria and their host. Anim. Feed Sci. Technol., 30: 203-266. Byers, F.M. and Schelling, G.T., 1988. Lipids in ruminant nutrition. In: D.C. Church (editor). The Ruminant Animal. Digestive Physiology and Nutrition. Prentice Hall, Englewood Cliffs, N J, pp. 298-312 Duncan, W.RH. and Garton, G.A., 1978. Differences in the proportions of branched-chain fatty acids in subcutaneous triacylglycerols of barley-fed ruminants. Br. J. Nutr, 40:29 34. Egan, H., Kirk, R.S. and Sawyer, R., 1987. An~ilisis qufiuico de alimentos de Pearson. (Chemical analysis of feeds after Pearson. ) Compafifa editorial continental SA. M6xico, pp. 443-518. Hamada, T., Maeda, S. and Kameoka, K., 1977. Factors influencing growth of rumen, liver and other organs in kid weaned from milk replacers to solid foods. J. Dairy Res., 59:11 t0-1118. James, A.T., Peters, G. and Lauryssens, M., 1956. The metabolism of propionic acid. Biochem. J., 64:726-73 I Jenkins, K.J., Kramer, J.K.G. and Emmons, D.B., 1986. Effect of lipids in milk replacers on calf performance and lipids in blood plasma, liver and perirenal fat. J. Dairy Sci., 69: 447459. Kurtz, F.E., 1965. The lipids of milk: composition and properties. Fundamentals of dairy chemistry. AVI Publishing Inc., Westport. Linzell, J.L., Mepham, T.B. and Peaker, M., 1976. The secretion of citrate into milk. J. Physiol., 260:739 742. L6pez-Bote, C., 1992. Calidad de la came. ( Properties of Meat. ) In: Martin, S. (Editor), Manual Prfictico de la Came. Martin Macias Publisher, Madrid, pp. 143-180. Massart-Le6n. A.M., Roets, E., Peeters, G. and Verbeke, R., 1983. Propionate for fatty acid synthesis by the mammary gland of the lactating goat. J. Dairy Sci., 66:1445-1454 Minato, H.; Ishibashi, S. and Hamaoka, T., 1988. Cellular fatty acid and sugar composition of representative strains of rumen bacleria. J. Gen. Appl. Microbiol. 34: 303-319. Neergaard, L., 1980. Influence of specially extracted soya meal on nitrogen and energy metabolism in the preruminant calf. In: L.E. Mount (Editor), Energy Metabolism. Proc. 8th Symposium on Energy metabolism. Butterworth, London, pp. 43~47. O'Kelly, J.C. and Spiers, W.G., 1991. Influence of host diet on the concentrations of fatty acids in rumen bacteria from cattle. Australian J. Agric. Res., 42:243-252 Penning, P.D., Penning, 1. and Treacher, T., 1977. The effect of temperature and method of feeding on the digestibility of two milk substitutes and on the performance of the lambs. J. Agric. Sci. Cambr., 88: 579-589. Porter, J.W.G., 1969. Digestion in the pre-ruminant animal. Proc. Nutr. Soc., 28: 115-12t. Rojas, A. 1990. Contribuci6n al estudio de la lactancia artilicial en la especie caprina. ( Artificial rearing of goat kids. ) Ph. D. Thesis. Universidad de Extremadura, 260 pp.
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Rojas, A., Rota, A., Martin, L., Rodriguez, P. and Tovar,J., 1992. Influencia del tipo de lactancia en cabritos sobre las caracterfsticas de su canal al sacrificio. (Effect of the type of lactation in young kids on the carcass characteristics.) Arch. Zootech., 41: 131-139. Rota, A., Rodriguez, P., Rojas, A., Martin, L. and Tovar, J., 1993. Evoluci6n de la cantidad y calidad de la leche de cabra Verata a 1o largo de la lactaci6n. (Evolution of milk quantity and quality in the Verata breed along the lactation period.) Arch. Zootech., in press. Sanz Sampelayo, M.R., Hemandez-Clua, O.D., Naranjo, J.A., Gil, F. and Boza, J. 1990. Utilization of goat milk vs. milk replacer
for Granadina goat kids. Small Rumin. Res., 3: 37-46. Sauvant, D., Bas, P. and Morand-Fehr, P., 1979. Production de cheveaux lourds: II.- Influence du niveau d'ingestion de lait sur les performances et la composition du tissu adipeux. (Production of heavy goat meat. II. Influence of level of milk feeding on performance and composition of adipose tissue.) Ann. Zootech., 28: 73-92. Semlek, M.A. and Riley, M.L., 1975. Fatty acid composition in growing lambs. Proceedings, Western Section, American Society of Animal Science, 26: 58-59. Walker, D.M. and Stokes, G.B., 1970. The nutritive value of fat in the diet of the milk-fed lamb. Br. J. Nutr., 24: 425-433.
Resumen Rojas, A., L6pez-Bote, C., Rota, A., Martfn, L., Rodriguez, P.L. and Tovar, J.J., 1994. Fatty acid composition of Verata goat kids fed either goat milk or commercial milk replacer. Small Rumin. Res., 14: 61~6. Se ha estudiado la composici6n en dcidos grasos de la grasa perirenal de cabritos de raza Verata alimentados con leche natural o con tres concentraciones de lactorremplazantes. No se hart encontrado efectos asociados al sexo. La dnica diferencia se encontr6 en los ficidos pentadecanoico (C15:0), heptadecanoico (C17:0) y heptadecenoico (Cl7:l), que alcanzaron valores mds elevados en animales de lactancia natural (P < 0,05 ). En el trabajo se discute el posible origen de estos ~icidos grasos, considerando el posible papel de los microorganismos del rumen o la incorporaci6n directa a trav6s de la grasa de la leche. La baja concentraci6n de dcido estefirico (alrededor del 15%) hace suponer una baja actividad ruminal. La determinaci6n de dcidos grasos impares puede permitir identificar el tipo de alimentaci6n suministrada a los cabritos.