(DMI) of leaves of Quercus calliprinos (from 660 to 900 g/head per day), of P. lentiscus(from 470 to 800 g/head per day) and ofCeratonia siliqua(from 800 to 1250 g/head per day). PEG supplementation generally increased DMI and protein and energy digestibility of browsing goats, and the production responses differed among breeds. For example, higher live weight gain of pregnant goats and higher birth weight of their kids occurred in the Mamber breed (Gilboa, 1996), while marked increases of milk yield were observed in Anglo-Nubian (Gilboaet al., 2000) and, to a lower extent, in Sarda goats (Decandiaet al., 2000a,b).
as the product of bite frequency (BF; bites/min), bite mass (BM; g DM/bite) and the time spent grazing according to the following equation:
DMI=
∑
(BFi ×BMi ×GTi)where DMI is dry matter intake (g), BFiis bite frequency (number of bites per minute of grazing) of theith species, BMiis mean bite mass (g DM) of theith spe- cies and GTiis grazing time (min/24 h) of theith species.
Table 8.6 shows some examples of bite frequency and corresponding intake rate (IR, g/min) measured in Sarda goats (M. Decandia, unpublished data), using the method of direct observation of bites (Kababyaet al., 1998). The observed mean intake rate of 6.3 g/min was similar to that found in other Mediterranean regions (Perevolotskyet al., 1998).
BF changes according to: (i) animal requirements; (ii) forage availability;
and (iii) nutritional and morphological characteristics of the species selected by goats. Mid-lactation goats usually have higher BF and, consequently, higher IR than late-lactation goats, because of their higher nutritive requirements. During summer, due to the higher proportion of browse plants in the diet of goats (Cabidduet al., 2000), even if BF is lower, IR is almost the same as that in spring.
The latter is attributed to the higher BM in woody than herbaceous species.
Degree of preference is usually positively correlated with BF. In some cases, low BF of less palatable species, such asP. lentiscusL., is due to their high tannin level. The morphological and physical characteristics of the plants also affect BF and IR. For example, the presence of spines in some species (Rubus spp.) reduces BF. BM is influenced by the same parameters discussed above.
Forage intake of goats (local breed) browsing on Mediterranean shrublands (Q. cocciferaL.) in northern Greece was determined by total faecal collection andin vitrodigestibility (Yiakoulaki and Nastis, 1995). For successful faecal col- lection, a faecal harness was specially designed for goats (Yiakoulaki and Nastis, 1998), which did not disturb their movements through the dense shrubs, their
Spring Summer
Forage species BFa IR BF IR
Herbaceous species 45 7.4 33 4.3
Lonicera implexa Aiton 44 10.3 42 6.0
Myrtus communis L. 38 5.2 33 3.1
Pistacia lentiscus L. 29 9.8 30 7.7
Quercus ilex L. 37 13.0 31 13.6
Ramnus alaternus L. 39 8.5 38 8.8
Rubus spp. 31 4.4 25 5.5
aIncluding chew-bites.
Table 8.6. Bite frequency (BF; bites/min) and dry matter intake rate (IR; g/min) observed in Sarda goats in middle and late lactation grazing on Mediterranean shrublands. (Adapted from M. Decandia, unpublished data.)
bipedal stance and their feeding behaviour. In another study conducted in the same area, the Cr2O3marker was dosed (Yiakoulaki, 1992). The Cr2O3concen- tration in goat faeces was determined by a combination of the alkali fusion method (Na2O2) with atomic absorption spectrophotometry (Yiakoulaki et al., 1997). Intake values of browsing goats measured in different Mediterranean regions are shown in Table 8.7.
Variables that explain better the variability of DMI in browsing goats are 4%
fat-corrected milk (FCM) yield, CP and polyphenolic tannin (PT) level in the diet.
Experimental data of lactating Sarda goats browsing a lentisk-based shrubland for 7 h/day were used to calculate the following prediction equations for pasture intake (Decandiaet al., 2005a):
DMI =−18.63 + 6.75 CP + 0.02 FCM; n= 38;
R2= 0.77;P< 0.001 (8.1)
DMI = 52.54 + 0.037 FCM−16.44 PT/CP; n= 40;
R2= 0.59;P< 0.001 (8.2)
where DMI is dry matter intake (g/kg BW0.75per day), FCM is 4% fat-corrected milk yield (g; Sandrucci et al., 1995), CP is crude protein in the diet (%), and PT/CP is the percentage ratio between polyphenolic tannins and crude protein.
Breed Country Period
Intake (g DM/kg
BW0.75)
Main browsed species
Rovea France 44–76 Quercus coccifera, Rosa
officinalis, Juniperus oxycedrus Mamberb Israel Dec–Aug 64–88 Quercus calliprinos, Stirax
officinalis, Pistacia palaestina Native breed×
Alpinec
Tunisia 102 Acacia cyanofilla, Atriplex
nummularia, Ceratonia siliqua, Pistacia lentiscus
Sardad Italy Mar–Jun 71–104 P. lentiscus, Quercus spp., Myrtus communis
Sardae Italy Mar–Jul 48–123 P. lentiscus, Quercus spp., M. communis
Sardaf Italy Jun–Jul 55–91 P. lentiscus, Quercus spp., M. communis
Native breedg Greece Nov–Feb 42–66 Q. coccifera, Carpinus orientalis, Fraxinus ornus, Cistus spp.
DM, dry matter; BW, body weight.
Data source:aDumontet al. (1995);bKababyaet al. (1998);cBen Salemet al. (2000a);
dDecandiaet al. (1997a,b);eDecandiaet al. (2000a,b);fDecandiaet al. (2004a);
gYiakoulaki and Nastis (1995).
Table 8.7. Dry matter intake values of browsing goats in different Mediterranean regions.
In those experimental conditions, CP and PT/CP in the diet were related to the percentage of grass in the pasture, determined by the method of Daget and Poissonet (1969), and milk urea (MU), as follows:
CP = 5.10 + 0.20 Grass + 0.119 MU; n= 31;
R2= 0.82;P< 0.001 (8.3)
PT/CP = 1.21 + 0.019 MU−0.012 Grass; n= 29;
R2= 0.49;P< 0.001 (8.4)
where CP is crude protein in the diet (%), PT/CP is the percentage ratio between polyphenolic tannins and crude protein, Grass is the percentage of herbaceous species in the pasture and MU is milk urea level (mg/100 ml).
The regression equations (8.1) and (8.3) have higherR2than equations (8.2) and (8.4) and seem more suitable for application at farm scale. Using these rela- tionships, a prediction model of DMI of browsing goats on shrublands rich in high- tannin species is proposed (Fig. 8.7). By estimating the percentage of herbaceous species in the pasture, and measuring the urea level in the milk, CP (%) in the diet can be predicted using Eqn (8.3) (Fig. 8.7a). If the dietary CP level is known, the measurement of FCM yield allows the prediction of DMI on pasture (Eqn (8.1);
Fig. 8.7b). For instance, if the grass component in the pasture is 20% and milk urea is 25 mg/100 ml, the predicted CP (%) should be 12 (Fig. 8.7a). If the FCM is on average 1200 (g), the DMI should be 80 (g/kg BW0.75per day; Fig. 8.7b). Even if this model is not general, it can be applied in conditions similar to those in which the experiments used to fit the equations were conducted, that is: (i) goat breed of low–medium production level; (ii) limited access time to the pasture (5–7 h/day);
(iii) shrubland with high-tannin species (e.g. based onP. lentiscusL.); (iv) low con- tribution of grass in the botanical composition of shrubland (10–30%); and (v) low–moderate supplementation level (200–400 g DM/head per day).