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Please note this is a comparison between Version 1 by Guillermo Ripoll and Version 2 by Yvaine Wei.
Since goat milk has a higher value than kid meat in Europe, some farmers rear kids with milk replacers, although some studies have stated that kids raised on natural milk yield higher-quality carcasses. The previous studies showed some interactions between breed and rearing system on carcass and meat quality.
- rearing system
- tissue composition
- breed
1. Introduction
Goats are important species due to their contributions to the development of rural areas [1], provisioning meat and milk, which are among the most valuable services of livestock [2]. Spain ranks second in the European Union in terms of number of goats, producing 20% of the goat milk and 10.9% of the kid meat in the European Union [3]. In addition, the sale of suckling kids makes up 20% of the total income per goat on the dairy farm [4], and 80% of this kid meat originates from the suckling kid category (cabrito) [5], whilst the other 20% of meat comes from adult goats that are no longer in dairy production. These suckling kids have a live weight of 6–13 kg and a carcass weight of 3.5–7 kg and are perceived by consumers to be a high-quality meat [6].
Eighty-eight percent of European Union goats are raised extensively and slaughtered as kids, with carcass weights between 5 and 11 kg [7]. When kid goats are reared with their dams, the availability of milk for cheese production is decreased. In addition, the milk from goats with feeding kids has less fat and protein than milk from lactating goats without suckling kids [8]. Therefore, some goat farmers remove the kids from their dams at a very young age and rear them with milk replacers. Milk replacers specifically formulated for kids can result in high daily weight gain, but some authors [9][10][11][9,10,11] have pointed out that suckling kids better metabolize nutrients from natural milk, yielding higher-quality carcasses.
2. Carcass, Head, Viscera, and Kidney Fat Weights
There were significant interactions between breed and the rearing system for all variables. Hence, to achieve a hot carcass weight (HCW) of 5 kg, Majorera and Palmera kids fed MR and all Tinerfeña kids were slaughtered with the greatest SW. Conversely, Florida and Verata kids fed NM and Guadarrama kids were slaughtered with the lowest SW. The least square in the table has been adjusted for an HCW of 4.965 kg. Because the HCW was the same for all kids, breeds with greater SW had a lower dressing percentage (DP). Within breeds, Guadarrama and Retinta fed MR had greater DP than their counterparts fed NM (p < 0.05), while Majorera, Palmera, and Verata fed NM had greater DP than their counterparts fed MR (p < 0.05). Independent of the rearing system, the three Canarian breeds (Palmera, Tinerfeña, and Majorera) presented the lowest DP. In the MR rearing system, Guadarrama presented the highest DP values, whereas in the NM rearing system, Verata presented the highest values, although they were no different from Florida. The use of MR increased the head weights (p < 0.05) of Majorera, Palmera, and Payoya, while the other breeds were not affected by the rearing system (p > 0.05). Verata from the two rearing systems had the lightest head, while Majorera fed MR had the heaviest head. The use of MR increased the viscera weights (p < 0.05) of Florida, Payoya, and Retinta, while the other breeds were not affected by the rearing system (p > 0.05). Verata reared on both systems had the lightest viscera. According to the results of this study, the influence of the rearing system is clearly conditioned by the breed but there is no pattern associated with the dairy or meat-production aptitude of the breeds used, that is, the differences are due to the breed and not to its usefulness. Differences in dressing percentage and head and visceral weights between breeds of suckling kids have been reported previously [12][13][15,16], although some inconsistencies can be found in the literature. Since dressing percentage is mainly affected by the weight of the digestive tract [14][21], some authors have reported that natural milk increases the ruminal and intestinal weights in lambs because these lambs have a lower rumen functionality [15][22], whereas other authors reported opposite findings. Panea, Ripoll, Horcada, Sañudo, Teixeira, and Alcalde [13][16] and Perez, et al. [16][24] found that the use of milk replacer did not affect the DP and head weights of Creole, Malagueña, and Murciano-Granadina suckling kids, but other studies reported that the visceral weight of Murciano-Granadina changed with the rearing system [13][16]. The KF weight increased when animals were fed NM in Florida, Guadarrama, and Retinta breeds, without changes in the other breeds. This increase is especially noticeable in the Guadarrama breed. Florida from NM system presented the highest KF weights whereas Payoya from MR presented the lowest values, although without differences with Payoya fed NM, Palmera fed MR, and Guadarrama fed MR. The effect of rearing system on fat carcass content agreed with the results from other authors [10][17][10,25] as well as the fact that in natural milk feeding regimes, dairy breeds presented higher fat amounts than meat-specialized breeds [10][13][10,16].3. Kidney Fat Colour
The colour of kidney fat is not a quality cue per se because it is not an eaten fat, but since goats have very little subcutaneous fat, kidney fat is a good option to measure the influence of the rearing system on fat colour. Therefore, there were statistical interactions between the rearing system and the breed for all colour variables (p < 0.001). Colour L* and Hab parameters are depicted in Figure 1. In general, L* values were higher for the NM rearing system, although no differences between rearing systems were detected in FL and GU. The hab was affected only in the Florida and Majorera breeds, with MR values higher than those of the NM breeds.
Figure 1. L* versus Hab colour parameters of the kidney fat of kids reared with milk replacer (MR) or natural milk from their dams (NM).
4. Carcass Measurements
Means for carcass measurements are presented in Table 12. There were significant interactions between effects for all studied variables (p < 0.005). Both the round perimeter (RP) and the hind limb width (LWI) were affected by the rearing system only in the Majorera breed, with NM presenting higher values than MR. Florida presented the lowest values for both variables, independent of the rearing system, whereas Verata presented the highest values. The use of MR resulted in longer carcasses in the three Canarian breeds (Majorera, Palmera, and Tinerfeña), without influence on the other breeds. Majorera, Payoya, and Palmera presented lengthier carcasses than the other breeds, especially in animals from the Payoya breed fed NM. The rearing system affected forelimb length only in Majorera and Tinerfeña breeds, with NM values lower than MR values. The Payoya breed presented a longer forelimb, whereas Palmera and Tinerfeña presented shorter forelimbs. Finally, the rearing system affected the carcass compacity index in all breeds except in Majorera, Payoya, and Verata, with NM presenting higher values than MR.
Table 12. Carcass measurements of kids reared with milk replacer (MR) or natural milk from their dams (NM).
| Breed (B) | RS | n | RP (cm) |
LWI (cm) | CL (cm) |
LL (cm) |
CI (g/cm) |
|||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Florida | MR | 15 | 29.8 | h | 8.3 | f | 40.6 | cde | 28.8 | bc | 122.3 | cd |
| NM | 15 | 30.3 | gh | 8.2 | f | 39.0 | e | 28.4 | bc | 126.7 | a | |
| Guadarrama | MR | 15 | 34.0 | def | 9.4 | de | 41.6 | bcd | 28.7 | bc | 119.0 | e |
| NM | 16 | 37.0 | abcd | 10.2 | cde | 39.7 | de | 28.0 | bc | 124.2 | ab | |
| Majorera | MR | 16 | 35.4 | cde | 9.2 | ef | 44.7 | a | 28.6 | bc | 111.1 | gh |
| NM | 16 | 39.7 | a | 10.3 | cd | 41.7 | bcd | 20.4 | de | 117.8 | g | |
| Palmera | MR | 15 | 37.4 | abc | 10.5 | cd | 43.1 | ab | 20.4 | de | 113.9 | h |
| NM | 16 | 38.7 | ab | 10.0 | cde | 40.9 | cd | 20.5 | de | 120.2 | fg | |
| Payoya | MR | 16 | 34.9 | cdef | 10.6 | c | 43.1 | ab | 30.5 | a | 114.8 | ef |
| NM | 14 | 35.9 | cbde | 10.2 | cde | 43.1 | ab | 29.7 | ab | 115.0 | ef | |
| Retinta | MR | 15 | 32.1 | fgh | 10.9 | c | 40.6 | cde | 27.6 | c | 121.1 | ef |
| NM | 15 | 33.2 | efg | 11.1 | bc | 40.1 | de | 27.1 | c | 122.8 | c | |
| Tinerfeña | MR | 16 | 37.7 | abc | 10.1 | cde | 42.4 | bc | 20.9 | d | 116.1 | gh |
| NM | 16 | 37.8 | abc | 10.2 | cde | 39.1 | e | 19.2 | e | 125.7 | ef | |
| Verata | MR | 15 | 33.9 | def | 12.3 | a | 40.2 | de | 27.6 | c | 123.1 | bc |
| NM | 15 | 36.8 | abcd | 11.9 | ab | 40.2 | de | 27.6 | c | 123.5 | c | |
| s.e. | 0.23 | 0.10 | 0.15 | 0.30 | 1.44 | |||||||
| B | 0.0001 | 0.0001 | 0.0001 | 0.0001 | 0.0001 | |||||||
| RS | 0.0001 | 0.473 | 0.0001 | 0.0001 | 0.0001 | |||||||
| B*RS | 0.006 | 0.001 | 0.0001 | 0.0001 | 0.0001 |
RS, rearing system; RP, round perimeter; LWI, forelimb width, CL, carcass length, LL, forelimb length, CI, carcass compactness index. s.e., standard error. Least square means were adjusted for an HCW of 4.965 kg. Different superscripts (a,b,c,d,e,f,g,h) indicate significant differences (p < 0.05).
In general, the MR rearing system increased the length measurements, whereas the NM rearing system increased compactness. Rodríguez, et al. [18][26] reported greater quality carcasses from kids reared with milk replacers, which agreed with the current results for carcass length and forelimb length.
The forelimb is often dissected into different tissues because it is easily disjointed, and it is said to be well related to the tissue composition of the carcasses of suckling kids [19][20][27,28]. The influence of the rearing system on tissue composition is not conclusive because it is conditioned by breed. De Palo, et al. [21][29] and Todaro, et al. [22][30] reported no effect of feed on limb weight or tissue composition, whereas Napolitano, et al. [23][31] did not find differences in muscle or bone percentages, but forelimb fat was greater when natural milk was used. Similarly, other authors [24][25][32,33] reported greater intramuscular amounts when animals were fed natural milk. Finally, Panea, Ripoll, Horcada, Sañudo, Teixeira, and Alcalde [13][16] reported that natural milk increased the subcutaneous and intramuscular fat percentages of Malagueña, while Murciano-Granadina was not affected by the rearing system. TAccording to our results, the percentages of subcutaneous, intermuscular, and total fat of forelimbs are highly correlated among themselves, but as expected, the higher the bone percentage is, the lower the muscle percentage due to a well-known process called repartition [20][21][28,29]. These relationships can be clearly observed in Figure 2.
Figure 2. Biplot of the principal component analysis of tissue composition of forelimbs from kids reared with milk replacer (MR) or natural milk from their dams (NM).
The usefulness of multivariate analysis to study variable relationships has been demonstrated by several authors [11][26][11,34]. The two axes of the biplot explained 82.27% of the variability. The first dimension separates the muscle percentage, on the left, to the fat percentages, on the right. Dimension 2 was explained by the bone percentage. Thus, the three Canary breeds were more muscled than the others, although Verata presented the heaviest carcasses. NM was related to fatness percentages, whereas MR was related to muscle percentage. As expected, muscle percentage was inversely related to fatness degree.
