3.1. Description of the Rearing Managements Defined
Four rearing managements (RM) applied during the heifers’ whole life were defined by hierarchical clustering on principal components.
The first rearing management (RM-1) was performed on 44 heifers. The main characteristics of RM-1 compared to the other managements were:
There was the highest percentage of artificial insemination (
Table 1). During PWP, the calves had the longest pasture duration and the shortest period with concentrates in their diet. The calves did not receive concentrates in pasture. At housing, 70.5% and 79.5% of the calves did not receive forages and concentrates in their diet, respectively. The heifers were weaned at the oldest age.
The heifers had the longest GP duration and the longest outside and pasture durations during this period (
Table 2). Outside, the heifers received forage complementation during a longer period than the heifers from RM-2 and RM-4. In their housing diet, the heifers had a higher percentage of hay than RM-2 and RM-3, and the lowest percentage of grass silage. Moreover, 90.9% of the heifers did not receive corn silage in their housing diet, and 43.2% received above 50% of wrapped haylage. During GP, the heifers received concentrates for the shortest period and ingested the lowest concentrate quantity. The average concentrate consumed by the heifers during this period had the lowest CP and NE contents. Outside, 97.7% of the heifers did not receive concentrates.
During FP, the heifers were the oldest at the beginning of the fattening and at slaughter (
Table 3). The FP duration was shorter than RM-2 and RM-3, and 70.5% of the heifers were fattened in pasture. In RM-1, for 61.4% of the heifers, the pasture duration was below 100 days, and 45.5% of the heifers were fattened with only grass as fiber source. During FP, the heifers consumed the lowest concentrate quantity. The average concentrate consumed by the heifers during this period had the lowest CP and NE contents.
The second rearing management (RM-2) was performed by 59 heifers. The main characteristics of RM-2 compared to the other managements were:
The calves received forages in their diet during a longer period than the calves from RM-4, and 62.7% of the calves received forages during the housing period (
Table 1). The calves received concentrate in their diet during a longer period than the calves from RM-1 and RM-3, and 62.7% of the calves received concentrate during the pasture. During PWP in housing, a high proportion of the calves (52.5%) received an average concentrate with a CP content lower than the calves from RM-3 and RM-4. However, in pasture, the majority of the calves received the average concentrate with the highest CP content. During the housing period and the whole PWP, the majority of the calves received an average concentrate with the highest NE content.
The heifers had the shortest GP and a shorter pasture period than RM-1 and RM-3 (
Table 2). During the housing period, the heifers received on average a lower proportion of hay and a higher proportion of grass silage than the heifers from RM-1 and RM-4. Moreover, 64.4% of the heifers did not receive wrapped haylage and 50.8% received below 25% of corn silage. The duration of concentrate distribution in the heifers’ diet was intermediate compared to the other managements, throughout GP. Moreover, the heifers ingested a lower concentrate quantity than the heifers from RM-3 and RM-4. During the housing period, the average concentrate intake had a higher CP content than RM-1 and RM-3. During the pasture, 81.4% of the heifers did not receive concentrates.
In RM-2, the heifers were the youngest at the beginning of FP and were slaughtered younger than those from RM-1 and RM-3 (
Table 3). In RM-2, the heifers’ fattening duration was longer than in RM-1 and RM-4, and 54.2% of the heifers were fattened in a stall. However, 44.1% of the heifers had a period above 100 days during their fattening. In RM-2, the majority of heifers (44.1%) were fattened with corn silage as main conserved forage in their diet. The heifers consumed a higher concentrate quantity than those from RM-1 and RM-4. The average concentrate intake had a high CP and NE contents.
The third rearing management (RM-3) was performed by 32 heifers. The main characteristics of RM-3 compared to the other managements were:
The calves (78.1%) received forages in their diet in stall (
Table 1). Throughout PWP, the concentrate distribution was shorter compared to RM-2 and RM-3. At pasture, 68.8% of the calves did not receive concentrate. During PWP in housing, a high proportion of the calves (78.1%) received an average concentrate with a CP content higher than the calves from RM-1 and RM-2.
The GP duration of the heifers was intermediate compared to the other managements. Similarly, the outside and pasture durations were also intermediate (
Table 2). During the housing period, the heifers received a lower proportion of hay than the heifers from RM-1 and RM-4. Although 50% of the heifers did not receive corn silage, 31.2% received the highest corn silage percentage (between 25% and 40%). Moreover, 43.8% of the heifers received below 50% of wrapped haylage. At pasture, the heifers were complemented with forages during a higher duration than heifers from RM-2 and RM-4. Throughout GP, the heifers ingested a higher concentrate quantity than those from RM-1 and RM-2. During the outside period, 53.1% of the heifers consumed above 150 kg of concentrates. The average concentrate intake during GP had high CP and NE contents. In RM-3, all heifers received concentrates in pasture and 68.8% received an average concentrate with the highest NE content.
The heifers were slaughtered older than the heifers from RM-2 and RM-4 (
Table 3). The heifers started the fattening with an intermediate age compared to the other RM. They had a longer fattening duration than the heifers from RM-1 and RM-2. The fattening was mainly performed in a stall (62.4% of the heifers) and the diet can be compounded by different main forages. The heifers consumed the highest concentrate quantity. For FP, the average concentrate had contents of CP and NE, intermediate and high, respectively.
The fourth rearing management (RM-4) was performed by 36 heifers. The main characteristics of RM-4 compared to the other managements were:
The majority of the calves (>63%) did not have a complementation with conserved forages, throughout PWP (
Table 1). Moreover, the calves received concentrate during the longest period. All calves received concentrate in pasture. Throughout PWP, the majority of calves (66.7%) received an average concentrate with a high CP content (>17%) and a NE content below 7.5 kJ.
The heifers had an intermediate GP duration compared to the other RM but they had the longest period in a stall (
Table 2). In the housing diet, the heifers received a higher percentage of hay than heifers from RM-2 and RM-3. Moreover, the heifers did not receive wrapped haylage and the majority of heifers (61.1%) received corn silage in this diet. The heifers received concentrates during the longest period and consumed the highest quantity. At pasture, 44.5% of the heifers did not receive concentrates and 47.2% received above 150 kg. During the housing period, the average concentrate had a higher CP content than in RM-1 and RM-3. Outside, all heifers receiving concentrate consumed an average concentrate with an NE below 7.5 kJ.
The heifers were slaughtered younger than the heifers from RM-1 and RM-3 (
Table 3). The fattening duration was shorter than this in RM-2 and RM-3. The fattening was performed mainly in a stall. The heifers were mainly fattened with diets based on corn silage or straw. The heifers ingested a lower concentrate quantity than the heifers from RM-2 and RM-3. During FP, the average concentrate had high contents of CP and NE.
The main characteristics of the four rearing managements are summarized in
Figure 2. In summary, the heifers performing RM-1 had a long duration outside during their life and consumed few concentrates. These heifers were weaned, fattened, and slaughtered older. In the RM-2, the heifers had a short GP, and they were fattened and slaughtered younger. These heifers were mainly fattened in housing; however, some heifers had a period on pasture during their fattening. The RM-3 was intermediate compared to the three other RM. The heifers had a longer FP with diet based mainly on conserved grass (hay, silage, wrapped haylage) and a high concentrate quantity. The heifers performing the RM-4 had a long duration in housing and ingested a high concentrate quantity throughout their life. These heifers were slaughtered young with a short fattening duration based on straw or corn silage.
3.2. Effects of the Rearing Managements on the Carcass Traits
According to our results, the RM influenced carcass traits related to conformation and color (e.g., fat color, homogeneous color of the cut section, and LM color) (
Table 4). In the literature, few works studied the effect of cattle’s whole life on the carcass properties.
Carcasses with higher conformation scores were obtained when the heifers performed the RM-2 compared to those performing RM-1. However, the carcass conformations of RM-2, RM-3, and RM-4 were not significantly different (
p > 0.05). Our results are in accordance with Soulat et al. [
12,
22] showing that RM with the longest pasture duration during the heifers’ whole life as RM-1 (
Figure 2) produced carcasses with low conformation. However, for these authors similar conformation could be reached with different RM. As previously observed, the combination of different rearing practices [
22] or rearing factors [
40] applied throughout the heifers’ life can allow to produce carcasses with a similar weight, conformation, and/or dressing.
At the 6th rib level, the LM and overall meat grains were not significantly impacted by RM (
Table 4). The meat grain was mainly related to the muscle properties, in particular the muscle fiber size [
41]. To our knowledge, the effect of RM on the meat grain has not been studied. However, the effect of some individual rearing factors on the fiber size was observed [
42]. The slaughter age above 19 months [
43], the fattening diet [
44], and the physical activity [
45] had no effect on the LM fiber size, in young bulls. However, the RH had a grain meat rougher for carcasses from heifers performing the RM-2 compared to carcasses from heifers performing the RM-1. The RH grain meat was not significantly different between the RM-1 and the managements RM-3 and RM-4. Compared to the LM, the RH muscle have a higher proportion of type slow I fibers and a lower proportion of fast type II fibers [
46]. The RH muscle is a postural muscle. It is possible that RM had an effect on the fiber size of this muscle. To our knowledge, it is the first time that the effect of RM was studied on the grain meat of this muscle. This result will have to be confirmed by other results.
The color of the cut section was significantly more homogeneous for heifers performing the RM-2 than those performing the RM-4 (
Table 4). At 24 h
post-mortem, the LM was significantly darker for heifers from the RM-1 than those from the RM-2. In the RM-1, the heifers had a longer pasture duration than those performing the RM-2. In accordance with this result, many studies showed that the meat redness (lower a* value) was lower for the young bulls fattened in pasture than those fattened in stall [
47,
48]. However, it was difficult to compare our results with previous published works because they were mostly carried out on FP and observe the individual effect of rearing factor. Nevertheless, Soulat et al. [
49] also showed that the heifers performing an RM with a long pasture duration and fattening in pasture produced a darker LM meat than those performing an RM with a fattening only in housing. Cozzi et al. [
50] observed an opposite effect in heifers. The LM color was not significantly different between, RM-2, RM-3, and RM-4 (
Table 4). In these three RM, although the heifers were mainly fattened in housing, some heifers were fattened in pasture or in pasture and housing. Moreover, the fattening diets were different between the three RM. As observed in this study, many studies did not observe a significant effect of the fattening diet on the LM redness (a* parameter) [
16,
51]. Other studies showed that the LM redness can also be similar to RM with different fattening systems (pasture, housing, pasture and housing, and outside) [
12,
49]. Concerning the fat color at the cut section level, heifers from the RM-1 produced carcasses with yellower fat than those from RM-2 and RM-4. The fattening diet in the RM-2 and RM-4 was mainly based on corn silage or straw (
Table 3). The fat color of carcasses was not significantly different between RM-1 and RM-3. In RM-3, 46.9% of the heifers received a fattening diet based only on grass-conserved forages (hay, grass silage, and/or wrapped haylage). Our results are in accordance with those of Velik et al. [
52] and Duckett et al. [
53] who observed that the fat was yellower when heifers or steers were fattened in pasture compared to those fattened in housing. Moreover, Varela et al. [
54] and French et al. [
55] observed that the subcutaneous fat was yellower when the cattle ingested grass in fattening diet compared to those consuming fattening diet based on corn silage plus concentrate, or grass silage, or hay. Contrary to these authors, the fat color was not significantly different when the heifers were fattened in pasture or with fattened diet based on grass-conserved forages, in our study. According to our results, RM did not significantly affect the other carcass traits related to fat (
Table 4).
According to our results, RM had no significant effect on the weight, the LM seepage, the LM proportion, and the nerve abundance (
Table 4).
Our results must be confirmed by others because there are few results that consider heifers and the whole life of cattle. Consequently, it is difficult to compare our results with other published results.
According to the carcass quality target, considering joint carcass traits, different RM could be prioritized. From RM-1 and RM-3, the carcass traits were not significantly different (
Table 4). The effects of RM-2 and RM-3 on the carcass traits were not significantly different. The management RM-2 allowed the production of carcasses with high conformation and a wither fat than the RM-1. According to our results, it is difficult to favor an RM. The significant difference for each trait was generally only between two RM. It is necessary to carry out trade-off according to the quality target.
3.3. Effects of the Rearing Managements on the Meat Traits
According to our results, the RM had few effects on the analyzed meat traits (
Table 6). These results are in accordance with Soulat et al. [
12,
22,
49] in heifers.
After aging, only the L* color parameter of raw LM meat was significantly different between the four RM and tendencies were observed for both other color parameters (
Table 6). The LM meat from heifers performing the RM-2, was lighter compared to RM-1 and RM-3. In the RM-2, the heifers were slaughtered younger than those from RM-1 and RM-3. Moreover, in the RM-2, most of heifers were fattened in housing compared to those from the RM-1 that were fattened in pasture. Other studies showed that the LM meat aged 14 days had a higher L* values when the animals (steers or young bulls) were fattened in housing than those fattened in pasture [
47,
56]. In heifers, Cozzi et al. [
50] obtained the same results with LM meat aged 8 days. As for our results on the carcass, it is difficult to compare our results because there are few published results considering the heifer’s whole life. The heifers performing the RM-4 had the tendency to produce a redder raw meat than the other RM. The heifers performing the RM-2 had the tendency to produce a raw meat with a lower b* value than the other RM. It was possible that the effect of RM observed at 24 h
post-mortem on LM meat color (
Table 4) was mitigated by ageing. Some studies observed an effect of the aging on the meat color [
16,
57]. However, Moloney et al. [
57] did not observe an effect of the interaction between aging and fattening growth rate strategy.
The toughness of the LM (measured by texture profile analysis) and SV (measured by shear force) raw meats were not significantly different between RM (
Table 6) as observed in previous results of Soulat et al. [
11,
49], in heifers. According to the results of the texture profile analysis, RM did not influence texture traits of the LM raw meat (
Table 5). In accordance with our results, Marino et al. [
58] did not observe an effect of the fattening system (pasture vs. housing) on the texture profile of raw meat, in young bulls. However, Garcia-Torres et al. [
59] observed that the cooked LM was significantly tougher when the young bulls were fattened in pasture than those in housing pens.
In accordance with the results about raw meat toughness, the tenderness of the cooked LM meat evaluated by the trained panel did not display significant differences between RM (
Table 6). Among the 10 sensory descriptors studied, only the atypical flavor (
Table 5) of LM meat was significantly different between RM. It was higher when the heifers performed the RM-1 compared to those performing the RM-4. Soulat et al. [
49] observed also an effect of RM on the typical flavor of LM meat, in heifers. Concerning the sensory descriptors related to the texture (e.g., initial and overall tenderness, overall juiciness), no significant effect of RM were observed in previous results of Soulat et al. [
12,
49]. However, in previous studies, Soulat et al. [
12] did not show a significant effect of RM observed on the overall juiciness on the mean of two muscles LM and
rectus abdominis. The heifers performing RM-1 and RM-2 had the tendency to produce an LM meat with more nerves than those performing RM-3 and RM-4 without consequence on the tenderness of raw and cooked LM meat (
Table 6). This tendency could be explained by the pasture effect on the connective tissue. The pasture duration was more important in the RM-1 and RM-2 than the RM-3 and RM-4. Duckett et al. [
53] and Serrano et al. [
60] observed an increase of the total collagen content or of the soluble collagen/total collagen ratio, respectively, when grass was included in the fattening system.
Regarding the overall acceptability (hedonic descriptor), the heifers performing the RM-4 with a lower pasture duration produced an LM meat, which was appreciated significantly more by the trained panel than those performing RM-1 and RM-2 (
Table 6). In a previous study, a trained panel appreciated the LM meat more from heifers performing the fattening without pasture than those having a long pasture duration during only FP or during the heifers’ whole life [
12].
To produce the highest overall meat quality (considered the whole traits), the RM-3 and RM-4 would be prioritized. These RM allowed the production of LM meat with less lightness (weak L* value), with weak atypical flavor and highly appreciated, as the other meat traits were not impacted by RM (
Table 6).
Our results showed that RM can have little influence on LM meat properties (e.g., lightness, atypical flavor, and overall acceptability) and also that different RM can produce LM meat with similar properties (e.g., tenderness, juiciness, and flavor intensity). As observed for the carcass, our results need to be confirmed by others because there are few results on meat quality in heifers and considering the whole life of cattle.
To jointly manage carcass and meat properties from RM, the RM-3 allows an interesting trade-off to produce carcasses and LM meat with the highest overall qualities. RM-3 allowed the production of carcasses with a high conformation and smooth meat grain. The rib section was more homogeneous, the fat was yellower, and the LM was redder. RM-3 was characterized as being intermediate of the other RM (
Figure 2). In RM-3, the heifers received a fattening diet based on conserved grass forages with a high concentrate quantity during a long period.