their metabolic well-being (Bailoni and Andrighetto, 1995; Economides, 1998;
Goetschet al., 2001; Fedeleet al., 2002).
Indeed, once goats perceive the metabolic effects of a diet very rich in con- centrates, they change their feeding behaviour to have small and numerous daily meals (Abijaoudéet al., 2000), thereby avoiding the dangerous effects of exces- sive starch in the rumen. Several experimental trials have been carried out on
content than that of Saanen goats. This was attributed to the higher microbial density and dietary degradation rate in the Black Bedouin breed compared with the Saanen. This allowed the Black Bedouin breed to have similar intake to the Saanen, despite the longer rumen retention time. Other authors (Lindberg and Gonda, 1997) also observed better digestive capacity in wild goats (Nubia ibex) and in the Bedouin breed compared with Saanen goats.
The results obtained from our analysis could be related to the better dietary conditions of Alpine goats compared with Mediterranean ones.
Prediction of pasture intake of grazing goats
Short grazing is a widely adopted system for small dairy ruminants. This system consists of taking the animals to pasture, on sown swards or natural pastures, for
Experimental variable Group Breed
Total DM intake (g/day)
Lucerne/sorghum ratioa 80:20 Nubian 1470
70:30 1530
60:40 1450
50:50 1550
Type of grain and maize, 1 dose/day Damascus 2490
number of doses/dayb maize, 3 doses/day 2445
barley, 1 dose/day 2461
barley, 3 doses/day 2446
Percentage of 20 Alpine 1950
concentratec 35 2221
50 2170
65 2100
RDP/RUP ratio and 72:28; CP = 21.0% Alpine×Beetal 1140
CP leveld 55:45; CP = 21.0% 1080
55:45; CP = 17.5% 1090
Protected fat inclusion, 0 Alpine 1860
percentagee 1.5 1800
3.0 1990
4.5 2170
6.0 1960
Protected fat inclusion, 0 Granadina 1395
percentagef 9 1349
12 1274
RDP, rumen-degradable protein; RUP, rumen-undegradable protein; CP, crude protein.
Data source:aAndradeet al. (1996);bHadjipanaioutou (2004);cGoetschet al. (2001);dMishra and Rai (1996);eBrown-Crowderet al. (2001);fSanz Sampelayoet al. (2002).
Table 7.1. Dry matter (DM) intake of lactating goats (g/day). Data from various experimental trials carried out in different feeding conditions.
4 to 8 h per day between the two milkings. During milkings or during the night, the animals normally receive a feed supplement based on concentrates and/or by-products, and straw or hay.
Estimating pasture intake is desirable for correct feed management, in order to optimize the utilization of feed supplements. In fact, the supplement can cause a substitution effect on herbage intake, sometimes making this practice too costly.
The systems available to estimate feed intake of goats have been developed mainly for stall-fed goats (Luoet al., 2004; Morand-Fehr, 2005). In a detailed study on Mediterranean goat intake at pasture, Fedeleet al. (1993) proposed some equations to estimate DM intake. In particular, when variables affecting selectivity (chemical and botanical composition of the pasture) were included in the prediction models, intake was predicted more accurately than when only animal variables (e.g. BW and milk production and composition) were used. Since the equations were derived from a limited number of animals grazing in a restricted
Item BW (kg)
Milk yield (g/day)
DM intake (g/day)
CP (% of DM)
NDF (% of DM) Alpine breeds
n 64 64 64 64 41
Mean 53.4 2084 1984 15.5 39.4
SD 9.6 1122 626 2.8 8.1
Min 37.0 469 889 10.0 18.0
Max 70.0 4900 3440 22.3 48.2
Mediterranean breeds
n 69 69 69 59 43
Mean 49.4 1311 1408 15.9 35.8
SD 12.5 522 474 4.2 7.1
Min 24.0 300 572 10.1 18.0
Max 77.7 2630 3000 25.0 49.4
BW, body weight; CP, crude protein; NDF, neutral-detergent fibre;SD, standard deviation.
Table 7.2. Description of the database used to develop regression equations to predict dry matter (DM) intake in stall-fed goats.
Alpine breeds Mediterranean breeds
Independent variable n R2 P n R2 P
Milk (g/day) 64 0.734 <0.001 69 0.396 <0.001
BW (kg) 64 0.754 <0.001 69 0.635 <0.001
Diet CP (% DM) 64 0.204 <0.001 59 0.008 0.504
Diet NDF (% DM) 41 0.001 0.991 43 0.462 <0.001
BW, body weight; CP, crude protein; NDF, neutral-detergent fibre.
Table 7.3. Results of simple linear regression analysis with dry matter intake (g/day) as the dependent variable for Alpine and Mediterranean breeds.
area, characterized by a peculiar botanical composition, they should not be applied to other conditions.
With the aim of formalizing an intake model for lactating goats in short grazing systems, 600 individual pasture intake data were collected over 3 years of trials, together with information on milk production, milk composition, live weights, body condition score and different variables characterizing the pasture, and were statistically analysed.
Milk production (g/day)
y= 921.06 + 0.47x
5000 4000
3000 2000
1000 0
DM intake (g/day)
4000
3000
2000
1000
0
R2= 0.73
Fig. 7.1 Regression between dry matter (DM) intake and milk production in goats of Alpine breeds (n = 64; P < 0.01).
BW (kg)
80 70
60 50
40 30
DM intake (g/day)
4000
3000
2000
1000
0
y = –977.51 + 54.69x R2 = 0.75
Fig. 7.2 Regression between dry matter (DM) intake and body weight (BW) in goats of Alpine breeds (n = 64; P < 0.01).
The statistical analysis showed that the marked individualistic feeding behav- iour of grazing goats did not allow clear identification of a single key factor affect- ing voluntary intake of DM at pasture. Positive relationships were found between intake and production level or BW, probably owing to the animal’s capacity to adjust feed intake to nutritive requirements and rumen volume. Similarly, most reported equations estimating intake for cattle, sheep and goats include BW and/or milk production among the independent variables (Pulinaet al., 1996; Peyraud et al., 1998; Pittroff and Kothmann, 2001; Avondoet al., 2002; Luoet al., 2004).
Milk production (g/day)
3000 2000
1000 0
DM intake (g/day)
2500
2000
1500
1000
500
0
y = 910.21 + 0.44x R2= 0.40
Fig. 7.3. Regression between dry matter (DM) intake and milk production in goats of Mediterranean breeds (n = 69; P < 0.01).
BW (kg)
80 70
60 50
40 30
20
DM intake (g/day)
2500
2000
1500
1000
500
0
y= 307.26 + 24.42x R2= 0.64
Fig. 7.4. Regression between dry matter (DM) intake and body weight (BW) in goats of Mediterranean breeds (n = 69; P < 0.01).
Pasture intake, as expected, was negatively correlated with diet supplements, due to the substitution effect that the latter generally cause on herbage consump- tion. Such correlation was higher when supplement intake was expressed as grams of CP than when expressed as grams of DM. This had already been observed in sheep and was attributed to their ability to self-regulate intake on the basis of their protein needs (Avondoet al., 2002). Similar results were also found in trials on rams (Avondoet al., 2004a) and goats (Fedeleet al., 1993). Recently, the ability of lactating goats to reduce protein intake from pasture when receiving supple- ments rich in CP was clearly demonstrated (Avondoet al., 2004b). Thus, since goats are highly selective and choose parts of the pasture rich in protein even in very poor feeding conditions, the negative effects of protein supplement on pas- ture intake should be attributed, with greater likelihood, to the self-regulating protein theory hypothesized for sheep.
In our statistical analyses, all of the variables that were not co-associated, and which were significantly correlated with intake and were biologically mean- ingful, were included in multiple regression prediction models. The most signifi- cant prediction equation (R2= 0.41;P< 0.01) is as follows:
Pasture intake (g DM/day) = 822.11 – 6.188CPS + 0.138FCM + 9.131BW where CPS is the quantity of CP given with supplement (g/day), FCM is the pro- duction of 5% fat-corrected milk (g/day) (Pulinaet al., 1991) and BW is animal body weight (kg).
Pasture characteristics did not have significant effects on goat intake capacity in our study. Indeed, Garcíaet al. (1995) observed an increase in goat pasture intake when NDF and lignin content increased. In fact, the poor quality of the pas- ture is usually not a limiting factor for intake, thanks to the abundant rumen microflora of goats, associated with their intense selective activity. Only in extreme conditions, such as on a pasture containing more than 30% of DM and with a very poor chemical–nutritive composition, was pasture utilization by goats limited.
Figure 7.5 shows that DM intake at pasture tends to decrease as DM percentage of herbage increases, particularly over 30%. In these conditions, none of the vari- ables was significantly correlated with intake levels and it was clear that dietary supplements did not have any substitution effect, as normally occurs in good pasture conditions. It is well known that if the herbage is poor in quality, the administration of a supplement does not reduce intake but, in certain circum- stances, can actually increase it. Since only a few data on herbage DM content over 30% were available, a specific equation could not be developed. For this reason, it is recommended to use the equation proposed above only for pastures with DM content below 30%.