Growth study

The study used 18 Pelibuey lambs with an average age of 4 mo and a live weight of 21 ± 1.0 kg. They were randomly distributed to one of three treatments (six lambs per treatment). A completely randomized design was used with measures repeated in a factor¹⁷. The first factor was the type of diet [unfermented feed with canavalia (UFC), fermented feed with canavalia (FC), unfermented feed without canavalia (UFWC)]. The second factor was the number of evaluation period (five periods of 14 d to evaluate changes in live weight or 10 periods of seven days to evaluate changes in the nutrient intake). The experimental unit was the lamb. During the study, a lamb of the treatment without canavalia died by causes not related to treatments (pneumonia).

Lambs were individually fed throughout the study with isoenergetic and isoproteinic diets (Table 1). At the beginning of the study, each lamb received 500 g d^-1 of feed according to the treatments. Subsequently, the amount was adjusted daily, based on the intake, trying to maintain at least 10 % of refused feed. The feed was offered from 0800 to 1800 h. Lambs had free access to water.

The FC treatment included within its composition, meal of raw seeds of C. ensiformis; Vitafert (biologically active, rich in Lactobacilli and yeast, product obtained by liquid fermentation); soybean meal 4.0 %, rice polish 4.0 %, 15 %, mineral salt 0.5 molasses %, urea 0.4 %, 0.3 % ammonium sulfate, natural yoghurt 5.0 %, water 70.8¹⁵ and subjected to the process of solid fermentation¹⁴ for a minimum of 10 d. UFC treatment was included as part of the meal of raw seeds of canavalia (this type of diet was only used with a maximum of 3 d of preparation).

The components determination in diets were: dry matter (DM), crude protein (CP), organic matter (OM)¹⁸; neutral detergent fiber (NDF) and acid detergent fiber (ADF)¹⁹in situ degradation of the DM (IDDM)²⁰ and metabolizable energy (ME, Mcal kg DM^-1)²¹. The IDDM of the three experimental diets was determined at 36 h in two hybrids bovines (Bos indicus x Bos taurus), castrated and provided with a rumen cannula, with an average weight of 500 kg, housed in individual pens with water and mineral salt at freedom. Animals adapted for 21 d with a ration based on grazing in a meadow mixed wi th humidicola pastures (Brachiaria humidicola) and camalote (Paspalum fasciculatum).

The variables evaluated in animals were: live weight (LW), average daily gain (ADG), DM daily feed intake (kg lamb^-1), CP (g lamb^-1), ME (Mcal lamb^-1), NDF (g lamb^-1), ADF (g lamb^-1), as well as feed conversion rate (FCR) and feed efficiency (FE). Sheep were weighed by three consecutive days at 14 d intervals during six times. On each occasion, the average number of LW corresponded to the average weight of the three consecutive weightings. An electronic scale was used (Tru-Test Pro II version 3.2 ®), with an accuracy of 0.100 kg.

Feed intake by lamb was determined during three consecutive days every 7 d. Daily intake of DM, CP, ME, NDF and ADF was determined in 10 wk; for this it was considered the feed intake (humid basis) and the mean values of DM, CP, ME, NDF and ADF determined in ten samples (in duplicate) of each one of the experimental diets (Table 2). The FCR was determined through the DM intake:weight gain ratio. The FE corresponded to weight gain:DM intake relationship.

Analysis of variance with the MIXED procedure was used^(22)-I in the LW, ADG and DM intake CP, ME, NDF and ADF variables with support of the computer program²³. Comparison of means was performed with the "t" test by square means using the SAS pdiff option. FCR and FE data were analyzed with the Wilcoxon rank sum test for non-paired data²³.

Carcass study

At the end of the growth stage all lambs were slaughtered at the Federal Inspection Slaughterhouse 51 in Villahermosa, Tabasco, Mexico. Carcasses were weighed and introduced (for 24 h) in a cooling chamber (0 to 4 °C). Commercial hot carcass yield (carcass weight/ slaughter weight x 100) was calculated. The Longissimus dorsi muscle area was measured in the cold carcass between the 12^th and 13^th rib vertebra by means of a square plastic film grid in centimeters²⁴. Likewise, measured the distance of the greater diameter in middle lateral way (A) and the diameter in back-ventral direction (B)²⁵. Cold carcass was divided into five primal cuts: neck, arm, thorax, abdomen and leg²⁶.

The variables evaluated were: carcass weight hot and cold (kg), hot carcass yield (%), area, greater and lesser diameters of the L. dorsi muscle, fat (mm) and weight of the primal cuts (kg). Analysis of variance with the GLM procedure¹⁷ with support in a computer program was used for the data²³. The comparison of means was performed with the "t" test by square means with the pdiff²³. Carcass yield data were analyzed using the Kruskal Wallis test. When influence of treatment on the response variable was detected, it was applied the Wilcoxon rank sum test for non-paired data²³.

The given chemical composition of the three experimental diets are shown in Table 2. The IDDM in the two canavalia diets was less than expected normally in sheep at 24 h (80 %)²⁷ and 48 h (89 %)¹², as well as lower than expected in cattle at 36 h (98.9 %)²⁸. The differences between studies are probably attributed to the time used to determine the IDDM. There is evidence¹ about a tendency to reduce the IDDM as the canavalia seeds level increases in the diet of sheep (62 % in diets containing 0 % of canavalia; 59 % with 22 % of canavalia and 57 % with 32 % of canavalia). IDDM values in FC and UFC diets are similar to the UFWC diet. This circumstance favors the use of canavalia as an ingredient for ruminants.

Feed and nutriments intake

Type of diet, number of period and their interaction affected (P<0.01) intake of all nutrients studied, but without difference in the intake level (P>0.05) due to feed fermentation. The higher increased nutrients intake (P<0.05) was detected in UFWC treatment (Table 3).

Sheep fed FC and UFC diets showed a lower DM intake (and therefore of its components) in at least 27 % vs the UFWC diet. This result is not consistent with that reported in sheep^1,12,29 where it was noted that the inclusion of canavalia seeds in levels from 10 to 32 % did not affect feed intake. On the other hand, there are not studies who evaluate the influence of the level of canavalia seeds meal in feedstuff for sheep on its palatability. Only, it has been suggested³⁰ that canavalia shows low palatability when used as complement forage for sugar cane juice in comparison with other fiber sources (bran wheat, forage of sweet potatoes and Brachiaria decumbens). It is likely that lower DM intake detected in diets with canavalia seeds meal is attributed to a low palatability.

Intake of DM, ME, CP, NDF and ADF were influenced by the number of period (P<0.01). In particular, ME intake remained similar in the first two periods. Subsequently increased and remained almost constant in the rest of the periods, with the exception of the period 8 where increased to 2.8 Mcal d^-1 lamb^-1 (Figure 1).

^abc (P<0.01)

Figure 1 Effect of number of period on metabolizables energy (ME) intake in finishing Pelibuey lambs 

Intake of DM, CP, NDF and ADF considering the number of period, showed a similar trend as the DM. The increase in ME intake showed by lambs as the study advanced, was attributed to the type of diets used, who allowed to obtain a positive ADG and therefore the animals reached a higher LW. A higher LW increases DM and ME requirements³¹.

The interaction type of diet x number of period influenced (P<0.01) intake level of all nutrients studied. Lambs fed UFWC diet showed greater intake of DM, ME, CP, NDF and ADF through the entire period of study vs FC and UFC treatments.

Figure 2 shows ME intake considering the type of diet and period number, as well as the values of maximum temperature in the shelter (average temperature in each period). Lambs in the UFWC treatment had higher ME intake during the entire period of study with respect to the FC and UFC treatments.

Least squares means (± standard error) (P<0.01). * Maximum shelter temperature.

Figure 2 Effect of fermentation and number of period on metabolizable energy intake in finishing Pelibuey lambs 

In the UFWC treatment ME intake increased through the study, detecting the higher intake in the period 8. However, between the period 5 and 10 a steady ME intake with small variations was registered. The voluntary intake in the ruminant is affected by multiple factors, including physical (distension of the reticulum-rumen), hormonal (gastrointestinal hormones) and chemicals (volatile fatty acids)³².

It is likely that the higher maximum temperature recorded at the site where lambs stayed, limited ME intake (Figure 2). In this respect, it has been documented that an increase in temperature is associated with a reduction in feed intake³³. Additionally, the digestibility value of a diet limits energy intake, when DM digestibility (in diet with high fiber content) is between 67 and 80 %, the DM intake decreases as digestibility is increased after adjusting for body weight and energy produced³². In the present study the IDDM of diet UFWC was greater than 67 %.

In several studies^1,12 where canavalia seeds were evaluated in lambs, reported no changes in feed intake in intermediate periods of the study. However, in a work with sheep¹² considering two stages of growth (15 to 24 kg and 24 to 28 kg), was detected an influence of the level of canavalia in the feed. Results that do not match with findings identified in this study, where the lambs of the UFWC treatment showed marked differences in ME intake, from the third period, to the end of the study vs FC and UFC diets. This may be due to the presence of anti-nutritional factors in the canavalia seeds, which could be related to reduction of DM intake. In this regard, it has been proposed³⁴ that the ruminal medium is a place of detoxification of substances present in the feed for ruminants. However, it is possible that for the case of the antinutritional factors present in the canavalia seeds, the ruminal environment was not fully effective to minimize the negative effects of these factors.

With the exception of the period 8, ME intake in FC and UFC diets within the same period was similar (P>0.05). The above situation indicates that fermentation applied to the feed with canavalia did not affect intake of this type of diet.

Growth

Type of diet affected LW (P<0.05) and ADG (P<0.01) of lambs. The UFWC diet allowed a higher LW and ADG in relation to UFC and FC diets. The least squares means (± SE) were 29.9 ± 1.6 kg and 195 ± 14.6 g, 23.0 ± 1.6 kg and 62 ± 13.4 g, 24.4 ± 1.4 kg and 107 ± 13.4 g, respectively. ADG obtained in treatments with canavalia was less than that reported in other studies with sheep^1,12. In Pelibuey males¹² ADG varied between 190 and 220 g in animals fed with canavalia, while in diets where canavalia seeds meal replaced partially the soybean meal, the ADG was between 98 and 127 g¹.

The lower ADG detected in FC and UFC diets can be attributed to lower DM intake compared to the UFWC diet, which meant an intake reduction of 32 and 37 % ME and CP respectively. In addition, it is important to consider that an increase in the level of canavalia seeds meal reduces digestibility of cell wall components; with canavalia levels of 0, 22, and 32 % digestibility values were 59, 58 and 48 %, respectively¹. Some others agree³⁵ that sheep fed with Pennisetum purpureum and a dietary supplement (cotton seeds meal or C. ensiformis seeds meal) fibrous DM digestibility was 20 % greater for the treatment with cotton seeds with respect to canavalia treatment. In the present study, the experimental diets had between 27.0 and 30.6 % of NDF, and it is likely that in FC and UFC diets the digestibility of the cell walls had been reduced with respect to UFWC, situation that could help to explain the lower ADG. On the other hand, application of the fermentation process to feed with canavalia favored a greater ADG compared to UFC diet. This indicates that fermentation increased feed efficiency, since DM intake was similar in diets with canavalia.

The number of period influenced (P<0.01) LW and ADG. The LW was increased from the period 1 to 5 (21.3 ± 0.9 to 29.1 ± 0.9 kg). However, there was no difference (P>0.05) during the periods 5 (29.1 ± 0.9) and 6 (29.4 ± 0.9). The largest ADG was recorded between periods 2 to 3 (164 ± 18 g) and 4 to 5 (165 ± 18 g) and the lowest in the last period of 5 to 6 (165 ± 18 g). The changes detected through time in LW and ADG agrees with a study conducted in Pelibuey sheep male³⁶, who states that initially the production will have a fast growth as feed supply increases, then, it will be a point where the sheep weight will tend to decrease at unsatisfactory levels.

Additionally, when sheep achieved a feed intake level allowing to meet maintenance and growth requirements (measured through a positive ADG), the response is a sustained over time weight gain^31,37,38. In this regard, it has been suggested³¹ that to obtain an ADG of 150 g, lambs with 20, 25 and 30 kg, should consume 2.7, 3.0 and 3.4 Mcal ME d^-1, respectively. In the present study although the lambs showed lower ME daily intake, they achieved an ADG exceeding 150 g, likely attributed to the energy density of the diets used (Table 2), which was exceeding the recommendation for hair sheep³¹.

The interaction diet type x number of period affected (P<0.01) LW and ADG. Lambs in UFWC diet showed greater ADG at the beginning of the study (periods 1 to 2), and in the middle of the study (periods 3 to 4) with respect to FC and UFC diets (Figure 3). Sheep fed FC diet showed a greater ADG with respect to UFC diet only in period 2 to 3; ADG was similar in the other periods.

^abc (P<0.01)

Figure 3 Effect of fermentation and period on average daily gain (ADG) in finishing Pelibuey lambs 

With the exception of the last period, in the UFC diet, the ADG recorded throughout the study was positive. However, a tendency to reduce the ADG as the study advanced was detected in the three diets. This has been previously reported³⁷ in Pelibuey sheep grazing and receiving a feed complement. In the present study, the lamb continued growing (increases in LW and positive ADG) through the study, regardless of the diet. However, the máximum weight of the lamb (when the weight of the animal is a function of time), did not represent the maximum biological efficiency, which is consistent with previously data described in Pelibuey lambs³⁶.

The total ADG, FCR and FE were affected (P<0.05) by type of diet (Table 4). Although ADG was grater in lambs fed by the UFWC vs FC and UFC diets, AC and FE in the UFWC and FC treatments were similar (P>0.05). Lambs with the UFC diet showed the lower ADG and FE, as well as greater AC with respect to UFWC and FC diets.

AC obtained with UFWC diet was similar to those reported previously in Pelibuey lambs¹² and lower to indicated in hair sheep¹. However, the FCR in the UFC diet was higher than indicated by Dixon et al¹ who showed a FCR of 8.9 and 10.8 for inclusion levels of canavalia of 22 and 32 %, respectively. For his part, Mamani¹² reported a 7.2 AC when the canavalia was included in a 28.2 %. Apparently, the low DM intake and the smaller ADG detected in sheep fed UFC diet explains the high AC obtained. In support to this, there are indications that suggest that an increase in the level of raw canavalia seeds in sheep's feed tends to increase the weight of ruminal contents, and possibly reduce its change rate¹.

It is likely that inclusion of canavalia seeds, affects not only the digestibility of the diet³⁰ and the fibrous fraction of DM digestibility³⁵, but that the various antinutritional factors (e.g., concanavalin A and canavanine) present in the seeds limit intake of this type of diet. It has been suggested that the lectin (concanavalin A is a lectin) present in C. ensiformis and in Phaseolus vulgaris reduces absorption of nutrients by joining the surface of the epithelial cells of the small intestine⁴. No studies were found that addressed the possible damage that causes the concanavalin A to the rumen epithelium. While in a study performed in vitro with canavanine³⁹ was observed that this amino acid inhibits the growth of media of the lactic acid bacteria Lactobacillus arabinosus 175 (8014). The extent of the possible damage of canavanine to bacteria in the rumen will need to be addressed in future studies.

The results obtained in the intake of CP, ME, NDF and ADF, as well as the ADG, FCR and FE suggests that application of fermentation in solid state to canavalia diets allowed lambs to show higher growth efficiency in relation to UFC diet. It is suggested that this increased efficiency could be related to a reduction or inhibition of the negative effects of antinutritional factors present in the C. ensiformis seeds. Previous studies¹⁵ show that application of the fermentation process in solid state at the meal of raw C. ensiformis seeds reduces the canavanine concentration 12 % with respect to unfermented seeds, 3.7 vs 4.2 g 100 g DM^-1, respectively.

Application of fermentation to feedstuffs with canavalia allowed to increase the productive efficiency of lambs compared to a diet without fermentation, situation that increases the possibilities to include canavalia seeds in finishing diets for sheep in tropical regions.

Carcass features

With the exception of the hot carcass yield and lower L. dorsi muscle diameter, the rest of the variables studied were affected (P<0.01) for the type of diet (Table 5). Lambs receiving the UFWC diet showed greater fat carcass weight and fat coverage, as well as greater weight of the five primal cuts vs FC and UFC diets. However, the area and the greater diameter of the L. dorsi muscle were similar in lambs fed UFWC and FC diets.

The carcass weight is important because it represents the economic value of the products obtained when lamb are slaughtered; the carcass weight of the FC and UFC diets represented the 73.8 % and 67.3 %, respectively, of the carcass weight of UFWC diet. This response can be explained, partially, by the increased ME intake that showed the lambs with the UFWC diet. Partida and Martinez⁴² mention that an increase in the energy level (from 2.6 to 2.9 Mcal ME kg DM^-1) allows to get a heavier carcass in Pelibuey lamb.

In the present study the diets contained a similar ME level, however, lambs with UFWC diet showed greater daily ME intake.

The hot carcass yield was less than 50 % in all treatments, which is consistent with reports in Blackbelly⁴⁰ and Pelibuey⁴¹ grazing with feed supplementation; and Pelibuey in confinement⁴². However, it was lower to intact^43,44 and castrated²⁴, Pelibuey fed indoors. Apparently, the carcass yield differences between studies can be attributed to breed, feeding system, diet energy density and slaughter weight.

The primal cuts weight were higher in lambs with UFWC diet. This type of response is attributed to the increased nutrients intake in UFWC, that favors a greater synthesis of muscle tissue. It has been suggested⁴² that the higher energy density in the diet promotes a steady increase in muscle tissue up to 44 kg of weight, after which decreases. In the present study the lambs with the UFWC diet showed a higher and consistent nutrient intake with respect to lambs fed diets that included canavalia, which explains the greater weight of their primal cuts.

The area and greater diameter of L. dorsi muscle were similar in diets UFWC and FC, probably due to the similar FE detected between these two diets. While lambs with UFC diet had lower values in both parameters, as well as a lower FE; the latter is an indicator of the ability of the animal to gain weight depending on feed intake.

With the exception of dry matter, solid state fermentation process did not alter the chemical composition of the diets that included canavalia. However, lambs fed diet fermented with canavalia obtained greater feed efficiency and daily weight gain with respect to those who consumed feed non-fermented with canavalia, which indicates that the application of this process to a feed with raw canavalia meal seeds allows to increase the efficiency of production of finishing lambs. The lambs fed with diet non-fermented and without canavalia, showed greater nutrient intake that favored better growth efficiency, as well as higher carcass weight. The addition of meal from canavalia seeds in finishing diets of lamb allowed positive changes in growth, weight and carcass composition. However, these changes were smaller with respect to those obtained in lambs fed with a diet without canavalia seeds.