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Recent progress in the assessment of mineral requirements of
goats
*
F. Meschy
Laboratoire de Nutrition et d’Alimentation INRA INA-PG, 16, rue Claude Bernard F-75231 Paris Cedex 05, France
Abstract
For a long time, mineral requirements of goats have been extrapolated from those of cattle and sheep. To date advances in goat nutritional research allow more specific mineral recommendations. Endogenous losses of calcium and phosphorus might be more related to dry matter intake than to the bodyweight. True absorption coefficient of P is probably higher for goats (70–75%) than for other ruminant species. Calcium and phosphorus requirements for pregnancy are higher because of the frequency of multiple foetuses. The requirements for growth are lower than for calves. Nevertheless, calcium and phosphorus content of goat milk (1.3 g Ca / l, and 0.9 g P/ l, respectively) are very close to those of cow milk. A special attention must be given to sulphur according to fibre production needs. Several results indicate that goats are less sensitive to copper toxicity than sheep and cattle and can tolerate higher levels of Cu in their diets. Goats can also tolerate Mo levels 10 times higher than sheep. The goat sensitivity to iodine deficiency seems to be higher. Particular attention must be given to selenium and copper status of pregnant goats and / or new-born kids because of risk of white muscle disease or swayback. 2000 Elsevier Science B.V. All rights reserved.
Keywords: Goat; Mineral nutrition; Requirements
1. Introduction below this value will result in pathological con-ditions. The apparent minimal requirement is higher For a long time, mineral requirements of goats than the deficiency threshold value. It represents an have been considered as a halfway between those of intake that avoids possible decreases in production cattle and sheep. During the 10 last years, advances levels during a given period; the length of the period in mineral nutrition of goats have occurred and allow under consideration is generally short. This intake more specific recommendations for this ruminant level is often used in practice, but seems too species for macro-elements and trace elements. restrictive as it does not take into account the mineral Before beginning, it should be stressed that nutri- reserves. An intake level that is insufficient will not tional requirements can be rather variable. The have any short term effects on animal production, its deficiency threshold value corresponds to the mini- effects will be over the long term. The optimal mum requirement of a given nutrient. Intake levels requirement corresponds to an intake level that assures a zero balance in adult animals, and is sufficiently positive for growing animals. Finally, the
*Tel.: 131-14-408-1764.
E-mail address: [email protected] (F. Meschy) recommended dietary allowance is even higher than
the optimal level because it includes a safety margin, (Pfeffer, 1989) leads to a lower estimation of the PM
which takes into consideration the large inter-in- in goat: 0.08110.88 DMI. This latter equation dividual variations that exist. confirmed by Deitert and Pfeffer (1993) seems to be The aim of the present paper is to review the suitable for the P maintenance calculations in goats. recent goat mineral nutrition studies with the inten- This lower strict maintenance requirement of P for tion of proposing a more suitable mineral dietary goats could be explained by a better P recycling recommendations for this species. Normally macro- through the saliva as it was shown for urea (Tis-and micro-elements are discussed separately, par- serand and Alrhamoun, 1998). This hypothesis could ticularly as each employs different methodologies in be supported by a higher P concentration in the order to determine the requirement levels. saliva in goats than in other ruminant species
(Kes-sler, 1981).
There is no recent work on maintenance
require-2. Macro-element requirements ments for the other macro-elements, the data retained for sheep should still be used for goats (AFRC, 1991, Macro-element requirements are evaluated by the 1997; Kessler, 1991) calcium: 0.623 DMI10.228, factorial method. This method establishes the net magnesium: 3.5 mg / kg LW, potassium 50 mg / kg physiological requirement levels for an animal LW and sodium 15 mg / kg LW.
(maintenance, growth, gestation and production). It
also estimates the proportion of the intake that is 2.1.2. Growth requirement
actually available to meet these needs or true absorp- Several investigations (Pfeffer and Keunecke, tion coefficient (TAC). 1986; Pfeffer, 1989; Pfeffer et al., 1995) now allow specific recommendations for growing goats. The Ca 2.1. Net physiological requirements and P accretion seems to be slightly lower than those in sheep. Through these experiments, a good rela-2.1.1. Maintenance requirement tionship has been found between empty body weight The net physiological requirement for maintenance (EBW) and the P content of empty body mass is often assimilated with the endogenous faecal and (P ):
EBM
urinary losses (the latter are often negligible for Ca
and P in ruminants). It is convenient to consider this PEBM5 0.4416.89 EBW aspect from a relative standpoint. The endogenous
this corresponds to 5.8 g of P/ kg of LW gain, faecal loss of P actually corresponds to an irreducible
corresponding value for calcium was 9.4 g. Never-fraction that may represent the actual net
mainte-theless, these values must be considered with care nance requirement and also an excretory component
because of the wide range of variation according to that permits the organism to eliminate the P absorbed
the dietary level of P intake (Pfeffer et al., 1996). On in excess. This explains the quasi-linear relationship
the other hand, no difference was found according to between the endogenous faecal loss and the level of
the diet especially with milk fed kids up to 30 kg P intake in sheep (Grace, 1981; Braithwaite, 1985;
(Pfeffer and Rodehutscord, 1998). Values for other Scott et al., 1985, 1995; Ternouth, 1989). It is now
minerals may be assessed as 0.4 for Mg, 1.6 for Na well established that the maintenance requirement is
and 2.4 for K (Kessler, 1991). more closely related to the quantity of dry matter
intake (DMI) than to the body weight (BW) of the
animals (Braithwaite, 1983; Field et al., 1985; Pfef- 2.1.3. Net pregnancy requirement
mineral composition are 11.5 Ca, 6.6 P, 0.3 Mg, 2.1 Koddebusch (1988) appears to be somewhat high, ¨
K and 1.7 Na (Ludke, 1971; Pfeffer and Keunecke, and only possibly obtained with deficient animals. 1986; Kessler, 1991; Pfeffer and Rodehutscord, The true absorption coefficient of P is probably 1998). According to the size of the litter, these between the value of 75% (Pfeffer, 1989) and 65% values correspond to a net transfer from the goat to (Kessler, 1991). From our own observations (un-the kid(s) of more or less 40–90 g of Ca and 25–50 published data) from 65 individual balance trials
g of P. with lactating goats (BW 60 kg, milk yield 4.5
kg / day) the mean apparent absorption coefficient of 2.1.4. Net lactation requirement P was 44.5%. From these data the theoretical calcu-This requirement is much easier to determine than lated TAC (on the basis of endogenous loss accord-the ones previously discussed because it can be ing to Pfeffer, 1989 equation) was 70.7%. For the determined directly from the milk’s mineral com- calculation of P requirements in goats a TAC of 70% position, which can vary depending on stage of can be retained.
lactation (Table 1), breed or sanitary conditions Published TAC values of Ca for goats show a (mastitis). The goat milk mineral composition during wide range of variation. The value of 30% is the middle of lactation of all breeds pooled has been generally adopted (INRA, 1988; Kessler, 1991;
´
reviewed recently (Gueguen, 1997); the values are FAG, 1994) except by AFRC, 1997 (55%). In the given in Table 2. goat, the level of Ca intake (Maraval et al., 1984) markedly affects the efficiency of intestinal absorp-2.2. True absorption tion. Our own data (unpublished) show an important depression of Ca absorption with high levels of Ca in The true absorption coefficient or TAC (INRA, the diet (Table 3). That underlines that the TAC 1989) is the percentage of dietary intake truly value of 30% must only be used with normal calcium absorbed. The intestinal absorption depends on the supply.
absorptive capacity of the intestine and also on the There are no published results on true absorption potential absorbability of the mineral in feed. TAC of magnesium in goats available. Apparent absorp-of P seems to be higher for goats than for cows or tion studies show great variations. For example ewes; nevertheless, the value of 90% obtained by Kessler (1981) reported a range of 18–57%. With semi-synthetic diets we obtained quite high values of apparent absorption of Mg ranking from 41 to 57%
Table 1 with inorganic sources of Mg for in growing lamb
Effect of stage of the lactation upon Ca and P content (Meschy, 1998) as well as for lactating goats (un-(mean6SEM) of Saanen and Alpine breeds milk (unpublished
published). As demonstrated for cattle high
potas-data)
sium intake depresses Mg absorption in goats, but
Stage of the lactation n Calcium (g / l) Phosphorus (g / l) starch, not glucose or cellulose, supplementation Early 28 1.4060.04 1.0560.02 fully counteracts the inhibitory effect of potassium
Middle 27 1.2660.04 0.9560.03 on magnesium absorption (Schonewile et al., 1997). Late 26 1.,1560.04 0.8960.02
The TAC value of 20% derived from specific studies
Table 2
´
Mean mineral composition of goat’s milk (Gueguen, 1997) Table 3
Effect of Ca level of intake upon Ca availability in goats
Macro elements (g / l) Trace elements (mg / l) a
(mean6SEM,unpublished data)
Calcium 1.26 Zinc 3.8
n Intake (% requirement) AAC (%) TACc (%)
Phosphorus 0.97 Iron 0.46
Potassium 1.9 Copper 0.22 Exp. 1 65 160 17.8560.96 23.2361.02
Sodium 0.38 Manganese 0.06 Exp. 2 33 106 28.2260.97 38.8360.94
Magnesium 0.11 Iodine 0.07 a
AAC, apparent absorption coefficient; TACc, true absorption
Chlorine 1.1 Selenium 0.02
Table 4
in goats proposed by Kessler (1991) and adopted by
Recommended trace element allowances for goats (literature
FAG (1994) seems to be adequate for Mg
require-synthesis)
ment calculations in goats.
Element Recommended dietary level
TAC of K and Na has not been documented but
(mg / kg DM)
the values of 90 and 80%, respectively, for goats as
Copper 8–10
´ for other ruminants might be adequate (Gueguen et
Cobalt 0.1
al., 1987).
Iodine 0.4–0.6
Manganese 40–50
Zinc 50
3. Sulphur and trace-element requirements Selenium 0.1
Molybdenum 0.1
For technical reasons, the factorial method is not generally used to determine either the sulphur or
trace element requirements. A more global method including a safety margin to take individual differ-such as the dose–response method is generally ences into account. These values are given in the employed. This consists of evaluating the optimal Table 4. Only elements that differ in goat nutrition concentration of a given component of the diet based will be discussed. Likewise, essentiality of a number on either global criteria (performances) or more of other trace elements (F, As, Li, Ni, V, Al, Br) has specific ones as clinical signs of deficiency or been demonstrated (studies of Anke, reported by enzymatic activities. Haenlein, 1998). This studies were conducted with very low levels of these elements which are often far 3.1. Sulphur requirements from practical conditions, where natural diets and air and water contents allow generally sufficient supply. In ruminants, sulphur is mainly required to
opti-´
mise rumen microbial activity (Stevani et al., 1992), 3.2.1. Copper
but growth, lactation and fibre production also need As for other ruminants, the copper requirement of specific sulphur supply. The optimal S diet con- goats may be assessed at 8–10 mg per kg of DM of centrations (on a DM basis) reported in the literature the diet (Kessler, 1991; AFRC, 1997). The goats, are as follow: 2.2–2.5 g / kg (Durand and Komisar- especially young animals seem to be less sensitive to czuck, 1988) and 2.6 g / kg (Qi et al., 1992b) for copper toxicity than sheep are. This could be ex-microbial activity; 2.2 g / kg for growth (Qi et al., plained by a lower hepatic uptake by kids fed high 1993); 2.6 g / kg for lactation and 2.7 g / kg for fibre Cu content diets (6–9 times less according to Zervas production (Qi et al., 1992a, 1993). All these values et al., 1989). On the other hand, hepatic storage of are slightly higher than the requirements adopted for goats is ten times lower than in other ruminants other ruminants (NRC, 1989). (Anke and Szentmihalyi, 1986), which may lead to higher susceptibility of new-born kids for swayback 3.2. Trace mineral requirements or ataxia, especially in the case of multiple births.
It is possible to define deficiency threshold values 3.2.2. Cobalt
(the value above which the symptoms of a deficiency The goats seem to be less sensitive to cobalt disappear) and a toxicity level also considered a deficiency than other ruminants (Clark et al., 1987). ‘safety range’. Depending on the element in ques- In spite of this observation and because the Co tion, the range between these two values may be toxicity level is quite high a 0.1 mg / kg DM value quite variable: for example, there is a factor of 100 may be adopted for goats.
between them for cobalt, while only a factor of 3–5
for copper and selenium. 3.2.3. Iodine
Clark, R.G., Mantleman, L., Verkerk, G.A., 1987. Failure to obtain
for dairy cow (0.3 mg / kg DM) diets if fed to goats
a weight response to vitamin B12 treatment in young goats
were not sufficient to prevent goitre in kids (Lamand,
grazing pasture that was cobalt deficient for sheep. NZ Vet. J.
1981). According to Kessler (1991), the minimum 35, 38–39.
recommended dietary level of I for goats is assessed Deitert, C., Pfeffer, E., 1993. Effects of reduced P supply in combination with adequate or high Ca intake on performances
at 0.4 mg / kg DM and must be increased up to 0.6
and mineral balances in dairy goats during pregnancy and
mg / kg DM for high yielding dairy goats.
lactation. J. Anim. Phy. Anim. Nut. 69, 12–21.
Durand, M., Komisarczuck, S., 1988. Major minerals and rumen microbiota. J. Nut. 118, 249–260.
3.2.4. Molybdenum
´
FAG. 1994. Apports alimentaires recommandes et tables de la
In ruminants, Mo excess is generally more
docu-valeur nutritive des aliments pour les ruminants. Station
mented than deficiency, particularly its effect on Federale de Recherches sur la Production Animale Zollikofen´ ´ copper bioavailability. The goats are sensitive to Mo LMZ.
Falke, H., Anke, M., 1987. The reaction of goats to molybdenum
deficiency (growth depression, reproduction troubles)
loads. In: Proceedings of Macro- and Trace Element Seminar,
and the minimum dietary level is about 0.1 mg / kg
University Leipzig-Jena, Germany, Dec. 21–22, p. 448.
DM (Kessler, 1991). On the other hand, the goats
Field, A.C., Woolliams, J.A., Dingwall, R.A., 1985. The effect of
can tolerate much higher levels of Mo without dietary intake of calcium and dry matter on the absorption and showing toxicity symptoms in contrast to cattle and excretion of calcium and phosphorus by growing lambs. J.
Agric. Sci. 105, 237–243.
sheep (Falke and Anke, 1987).
Grace, N.D., 1981. Phosphorus kinetics in sheep. Br. J. Nut. 45, 67–374.
´ ´
Gueguen, L., 1997. La valeur nutritionnelle minerale du lait de
4. Conclusion chevre. In: Freund, G. (Ed.), Interets nutritionnels et dietetique` ´ ˆ ´ ´ `
du lait de chevre, INRA, Niort, pp. 67–80. ´
Gueguen, L., Durand, M., Meschy, F., 1987. Apports
recom-With the research data available now, it becomes
´ ´ ´ ´
mandes en elements mineraux majeurs pour les ruminants.
possible to have a more specific approach in mineral Bull. Tech. CRVZ Theix INRA 70, 105–112.
nutrition of goats at least for Ca, P, S and several Haenlein, G.F.W., 1998 Recent advances in mineral nutrition of
trace elements. Nevertheless, more research is goats. Web page http: / / bluehen.ags.udel.edu / deces / goatmgt / gm-03.htm.
needed to assess in goats some aspects still
extrapo-INRA, 1988. Alimentation des bovins, ovins et caprins. In:
lated from cattle and especially from sheep. Calcium
Jarrige, R. (Ed.), Institut National de la Recherche
Ag-and phosphorus bone mobilisation at the onset of ronomique, INRA, Paris.
lactation is a good example. INRA, 1989. Ruminant Nutrition, recommended allowances and feed tables. In: Jarrige, R. (Ed.), Institut National de la Recherche Agronomique, INRA, Paris.
´ ´ `
Kessler, J. 1981. Elements mineraux majeurs chez la chevre.
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