Pepper as a phytogenic additive in finishing lambs diets

Pimenta como aditivo fitogênico em dietas para ovinos em terminação

ABSTRACT

The objective of this study was to evaluate the effect of a phytogenic additive on nutrient intake, diet digestibility, nitrogen balance, and ruminal parameters of lambs. Four lambs with an average body weight of 27.6 ± 2.9 kg were distributed in a 4 × 4 Latin square design and fed a basal diet composed of 600 g DM/day of corn silage and 400 g DM/day of concentrate. The basal diet was supplemented with no additive 0.0, 2.0, 4.0, and 6.0 g/kg DM of pepper. The intake of DM, crude protein (CP), organic matter (OM), and neutral detergent fiber (NDF) in g/day decreased linearly (P < 0.05). No effects (P > 0.05) were observed for the apparent digestibility of DM, OM, NDF, and ether extract. There was a quadratic effect (P < 0.05) on the digestibility of CP and non-fibrous carbohydrate, with maximum digestibility estimated at 707.7 and 924.8 (g/kg DM) at levels of 2.55 and 0.27 g/kg DM of pepper, respectively. There was no effect (P > 0.05) on urinary nitrogen and retention nitrogen. Increasing levels of pepper did not alter (P > 0.05) the pH value and N-NH₃ concentration of the ruminal fluid. However, there was an effect (P < 0.05) of time on the pH and N-NH₃ value of the rumen. The inclusion of pepper in the diet of confined lambs negatively alters dry matter and NDF intake without impairing nutrient digestibility, nitrogen utilization, and other ruminal parameters.

Keywords
capsaicin; digestibility; intake; nitrogen balance; ruminal parameters

RESUMO

Objetivou-se avaliar o efeito de aditivo fitogênico sobre o consumo de nutrientes, digestibilidade da dieta, balanço de nitrogênio e parâmetros ruminais de ovinos. Quatro cordeiros com peso corporal médio de 27,6 ± 2,9 kg foram distribuídos em delineamento quadrado latino 4 × 4 e alimentados com uma dieta basal composta por 600 g MS/dia de silagem de milho e 400 g MS/dia de concentrado. A dieta basal foi suplementada com nenhum aditivo 0,0; 2,0; 4,0 e 6,0 g/kg MS de pimenta. O consumo de MS, proteína bruta (PB), matéria orgânica (MO) e fibra em detergente neutro (FDN) em g/dia reduziu linearmente (P < 0,05). Não foram observados efeitos (P > 0,05) para a digestibilidade aparente da MS, MO, FDN e extrato etéreo. Houve efeito quadrático (P < 0,05) sobre a digestibilidade da PB e do carboidrato não fibroso, estimando-se a digestibilidade máxima de 707,7 e 924,8 (g/kg MS) nos níveis de 2,55 e 0,27 g/kg MS de pimenta, respectivamente. Não houve efeito (P > 0,05) para o nitrogênio urinário e o nitrogênio de retenção. Níveis crescentes de pimenta não alteraram (P > 0,05) o valor de pH e a concentração de N-NH₃ do fluido ruminal. Entretanto, houve efeito (P < 0,05) do tempo sobre o valor de pH e N-NH₃ ruminal. A inclusão de pimenta na dieta de cordeiros confinados altera negativamente o consumo de matéria seca e FDN, sem prejudicar a digestibilidade dos nutrientes, a utilização do nitrogênio e outros parâmetros ruminais.

Palavras-chave
capsaicina; digestibilidade; ingestão; balanço de nitrogênio; parâmetros ruminais

1. Introduction

Owing to a greater concern for the quality of animal products (Ducatelle et al., 2015), human health (Anadon et al., 2019), and restrictions on meat products in important consumer markets (Forsythe, 2013), there is a growing interest in the use of natural products as food additives to the detriment of antibiotics commonly used in animal feed. Thus, probiotics, prebiotics, organic acids, and secondary plant compounds have been evaluated for their ability to mitigate the negative effects of high-concentrate diets on the rumen ecosystem and improve feed efficiency (Wencelová et al., 2015).

Phytogenic plants and their plant extracts have been evaluated as natural metabolism-modulating additives (Zheng et al., 2017) and for their effects on rumen fermentation (Cobellis et al., 2016). Indeed, some phytogenic additives have been shown to affect intake (Santos et al., 2010), digestibility of nutrients (Beauchemin & McGinn, 2006), and rumen parameters (Torres et al., 2020). However, the available information is limited, and more studies are necessary to evaluate the effects of potential phytogenic additives in ruminant animal feed.

Essential oils, saponins, flavonoids, tannins, and polyphenols are the main active compounds in medicinal plants tested as ruminal fermentation modifiers (Wencelová et al., 2015). However, the fruits of Capsicum spp., commonly used in human food, have shown promising results in medicine for their antioxidant, antimicrobial, anti-inflammatory (Pinto et al., 2013), and anti-obesity (Konstantinidi & Koutelidakis, 2019) activities. Additionally, they are rich in vitamins A, E, and C, folic acid, zinc, and stock potassium, lycopene, and phenolic compounds (Aguiar et al., 2014). These fruits contain capsaicin as the main compound of interest, an active compound classified as an aromatic terpenoid with a pungent nature (Geron et al., 2024), and antimicrobial activity (Orndorff et al., 2005).

Studies have suggested that the pungent power of capsaicin increases water and DM intake in ruminants (Cardozo et al., 2006; Rodríguez-Prado et al., 2012). For diets with high concentrate content, where there is a reduction in the ruminal pH value (Arteaga-Wences et al., 2021; Westphalen et al., 2021), the capsaicin molecule is in a hydrophobic state, thus activating its antimicrobial effect (Burt, 2004).

Two studies from our group showed that the addition of pepper extract to the diet of dairy sheep increases water intake and maintains lactation persistence (Cunha et al., 2020) while lactating lambs show more significant body weight gain (Cécere et al., 2022). The current study was designed to evaluate the effects of pepper inclusion in the diet on the intake and digestibility of nutrients, nitrogen balance, and ruminal parameters in lambs.

2. Material and methods

The experiment was performed in the Animal Metabolism sector and in the Laboratory of Food Analysis and Animals belonging to the State University of Mato Grosso, Pontes e Lacerda Campus, MT, Brazil (15° 19' 29.1" S, 59° 13' 59.0" W; height of 254 meters). The predominant climate is humid tropical, with an average annual temperature of 25 °C and an average annual rainfall of 1,500 mm. The animals were cared for in accordance with the guidelines outlined in the Guide for the Care and Use of Agricultural Animals in Research and Teaching (FASS, 2010). Ethical approval for the research protocol and animal welfare was obtained from the Animal Research Ethics Committee of the State University of Mato Grosso under protocol number 001/2017.

2.1. Animals, diets, and experimental design

Four Santa Inês crossed uncastrated male lambs with 25.0 kg ± 3.0 kg initial body weight were used in a 4 × 4 Latin square design. The animals were housed separately in metabolic cages for 88 days, consisting of a 15-day acclimation and a 7-day data collection period. The experimental diets were formulated to have equal amounts of crude protein and energy (Tables 1 and 2) and were provided twice daily (7:00 and 16:00 h). The lambs had free access to food and water.

The evaluated treatments were: (1) control, with no inclusion of pepper; (2) 2.0 g/kg DM inclusion; (3) 4.0 g/kg DM inclusion; and (4) 6.0 g/kg DM inclusion of pepper in the diet, corresponding to 0, 8.9, 17.9, and 26.8 mg of capsaicin per g of diet, respectively. The fruits of four pepper species (Capsicum frutescens, Capsicum baccatum, Capsicum chinense, and Capsicum annum) were used in equal proportions in the dry matter to compose the phytogenic additive. The ripe pepper fruits were dried in a kiln at 55 ºC for 96 h and subsequently processed through a crusher with a 0.7-mm sieve.

Table 1
Chemical composition of the ingredients.

Chemical composition (g/kg)	Experimental ingredients (g/kg of DM)
	Corn silage	Ground corn	Soybean meal	Pepper
Dry matter	318.6	900.8	913.1	256.7
Organic matter	968.0	939.1	980.5	949.2
Crude protein	89.6	86.9	492.6	178.2
Ether extract	29.1	37.9	25.5	46.8
Neutral detergent fiber	672.9	172.2	129.7	335.2
Acid detergent fiber	351.6	68.6	150.9	160.3
Non-nitrogen extract	568.0	759.4	341.7	570.0
Total carbohydrates	849.3	814.2	462.4	724.2
Non-fibrous carbohydrates	176.4	642.0	332.7	563.9
Ash	32.0	60.9	19.5	50.8
Total digestible nutrients	601.0	860.3	807.3	691.0
Capsaicin mg/g DM	-	-	-	4.47

2.2. Handling and data collection

The experiment lasted for 88 days, with 15 days for adaptation to the diet, environment, and management and 7 days for sample collection. From the second to the sixth day of collection, food, leftovers, feces, and urine were collected, forming a sample composed of animals per experimental period. The last day of the experimental period was used to collect the ruminal fluid.

A napa bag was used to collect feces from each animal. Every morning, the feces of each animal were weighed, homogenized, and sampled at 10% of their total weight. These samples were packed in plastic bags, identified by animal and experimental periods, and stored in a freezer for further processing and analysis. The food provided and leftovers from the animal diets were quantified and sampled daily. Clean and chlorinated water was provided to the animals in plastic buckets with a capacity of 8 liters. The water intake of each animal was measured for five days by weighing the difference of the buckets before and after intake, discounting the losses by evaporation. Losses by evaporation were determined by weighing two buckets with water that were distributed in the installation.

Plastic buckets covered with mesh were used to collect urine to avoid contamination by hair, feed, and feces. In each bucket, 30 mL of H₂SO₄ was added to avoid N volatilization and possible fermentation (Rufino et al., 2013). Urine collection was performed simultaneously each morning, and the total volume was measured as described by Zeoula et al. (2003). Samples of 5% of the total urine were placed in a single glass bottle duly identified by the animal in each experimental period (composite sample). The flasks were stored in a refrigerator at approximately 5 °C for later analysis of nitrogen concentration.

Table 2
Ingredient proportion and chemical composition of the experimental diets.

Ingredients of diets (g/kg of DM)	Pepper (g/kg DM)
	0.0	2.0	4.0	6.0
Corn silage	600.00	600.00	600.00	600.00
Ground corn	265.0	263.0	261.0	259.0
Soybean meal	135.0	135.0	135.0	135.0
Pepper	0.00	2.00	4.00	6.00
Chemical composition of diets (g/kg)
Dry matter	553.2	551.9	550.6	549.3
Organic matter	962.0	962.0	962.0	962.1
Crude protein	143.3	143.5	143.7	143.8
Ether extract	30.9	31.0	31.0	31.0
Neutral detergent fiber	466.9	467.2	467.5	467.9
Acid detergent fiber	249.5	249.7	249.8	250.0
Total carbohydrates	787.8	787.6	787.4	787.2
Non-fibrous carbohydrates	320.9	320.7	320.6	320.4
Total digestible nutrients	697.6	697.2	696.9	696.5
Capsaicin (mg/g DM of Pepper)	0.00	8.94	17.9	26.80

On the seventh day of collection, five rumen fluid collections were performed per animal at 0 (before feeding), 2, 4, 6, and 8 h (after the first feeding). Rumen fluid was collected using a vacuum pump with pressure and a silicone probe lubricated with mineral oil before being introduced into the animal's mouth. Approximately 100 mL of liquid was removed from the rumen of each animal and filtered with a double cotton cloth so that approximately 80 mL remained. The collected fluid was homogenized, and the pH was measured with a potentiometer immediately after each collection. Approximately 50 mL of ruminal fluid was transferred to a properly labeled bottle with 1 mL of H₂SO₄ to stop fermentation (Geron et al., 2019). The ruminal fluid sample was used to determine the concentration of ammoniacal nitrogen (NH₃-N) according to the recommendations of Fenner (1965).

To obtain the exact time of the estimated minimum and maximum point of the pH values and the concentration of ammoniacal nitrogen (NH₃-N) of the rumen fluid as a function of time after feeding, 60 min was used to represent a unit (1), such that every 6 min represented 0.1 unit of the time in the pH equations and NH₃-N of ruminal fluid.

The food, leftover, and fecal samples were dried in a kiln at 55 °C for 72 h and processed in a knife mill (Willey) using a sieve 1 mm. The samples were then mixed in equal amounts to form samples composed of feces and leftovers per animal for each experimental period.

2.3. Laboratory analysis

The analyses of DM (934.01), OM (924.05), CP (920.87), and EE (920.85) of the food samples were conducted according to AOAC (1990). Neutral detergent fiber (NDF) and acid detergent fiber (ADF) were determined according to Van Soest et al. (1991) and the 973.18 method (AOAC, 1990), respectively. The total carbohydrates (TC) of food, leftovers, and feces were determined using the following equation: TC = OM – [EE + CP] (Sniffen et al., 1992). The non-fibrous carbohydrate content (NFC) of food, leftovers, and feces was determined using the equation NFC = 100 – (CP + NDF + EE + ash) according to Sniffen et al. (1992). Total digestible nutrients (TDN) were calculated considering the intake and fecal excretion of nutrients using the following equation: TDN (%) = DTC + DCP + (2.25 × DEE), in which DTC is total digestible carbohydrates; DCP, the digestible crude protein, and DEE, the digestible ether extract (Brody, 1945). Capsaicin analyses were performed according to the methodology described by Wahyuni et al. (2011).

The N content in the urine was calculated using the Kjeldahl method as described by AOAC (1990), and the N balance was obtained using the formula: NB = [(N provided g – N leftover g) – (N fecal g + N urinary g)], as described by Geron et al. (2015). The absorbed nitrogen (AN) was calculated using the equation: AN = [(N provided g – N leftover g) – (N fecal g)], and the intake N (IN) was calculated using the equation: IN = [(N provided g – N leftover g)], according to Moreno et al. (2010).

2.4. Statistical analysis

All variables were analyzed using the MIXED procedure of SAS (version 9.4). Measures of pH and ammonia were analyzed as repeated measures in time, with treatment, time, and the treatment × time interaction as fixed effects and animal and experimental period as random effects. Based on the Bayesian information criterion, the data had an “unstructured” covariance structure. When the interaction between treatment and time was significant, the effects of time within a treatment were investigated as linear, quadratic, and cubic. Orthogonal contrasts were used to partition the effects of treatment levels (0.0, 2.0, 4.0, and 6.0 g in DM) across the linear, quadratic, and cubic equations. Effects were considered significant when P < 0.05. The following model was used in the analyses: yijk = µ + Ti + Pj + Ak + e ijk, where: µ is the mean of the experiment; Ti is the effect of treatment i; Pj is the effect of period j; Ak is the effect of animal k; eijk is the experimental error; where i, j, k = 1, 2, 3, 4.

3. Results

Dry matter, OM, CP, and NDF intake (g/day) decreased linearly (P < 0.05) with an increase in pepper (PP) concentration in the diets (Table 3); the intake, measured as a proportion of the animal’s body weight of DM (Ŷ = 3.3755 – 0.05225 * PP) and CP (Ŷ = 0.5120 – 0,008375 * PP), was also altered by pepper addition. Thus, according to the generated regression equations (Ŷ = 1045.0745 – 14.29025 * PP) and (Ŷ = 158.5295 – 2.169625 * PP), each g/kg of pepper inclusion decreased the DM and CP intake by 14.3 and 2.2 g, respectively. There was no influence (P > 0.05) on NDF intake values (kg body weight).

However, the inclusion of pepper in the lambs’ feed did not influence (P > 0.05) EE, NFC, and water intake, which had an average value of 33.8 g/day, 365.66 g/day, and 3039 mL/day, respectively. Quadratic behavior was observed (P < 0.05) for total carbohydrate intake (Ŷ = 835.8727 – 52.08675 * PP + 7.24 * PP2) and ADF, with an estimated minimum value of 742.2 g/day of total carbohydrates with the inclusion of 3.6 g/kg pepper in the diet. The NFC represents the highly digestible part of the diet; therefore, the animal controls intake to satisfy its energy requirements, which remained unaltered in the present study.

The inclusion of pepper in the diet did not affect (P > 0.05) the digestibility of DM, OM, EE, NDF, ADF, or TC (Table 4), with average values of 755.3, 746.1, 817.0, 609.8, 392.0, and 761.8 g/kg, respectively. However, there was a quadratic effect (P < 0.05) on the digestibility of CP and non-fiber carbohydrate, estimating (Ŷ = 668.859 + 31.0484 * PP – 62.0359 * PP²) 707.7 (g/kg DM) and (Ŷ = 92.2085 + 19.8149 * PP – 36.5734 * PP²) 924.8 (g/kg DM) maximum digestibility levels of 2.55 and 0.27 g/kg DM pepper, respectively.

Table 3
Intakes of dry matter, water, and nutritional components by lambs fed diets with different pepper levels.

Item	Pepper (g/kg DM)				SEM	p-values
	0.0	2.0	4.0	6.0		L	Q
Intake (g/day)
Dry matter	1061.4	1017.4	959.1	989.8	65.9	0.025	0.060
Organic matter	1023.0	988.9	940.3	957.3	72.3	0.001	0.044
Crude protein	156.49	158.76	146.85	145.70	10.188	0.002	0.466
Ether extract	34.35	34.83	32.80	33.27	2.080	0.418	0.998
NDF	454.74	415.30	375.54	402.91	33.709	0.027	0.068
ADF	241.86	232.95	201.10	233.95	21.369	0.070	0.010
TC	827.65	785.34	718.69	792.22	50.405	0.032	0.006
NFC	372.55	370.47	328.99	390.65	25.148	0.862	0.090
Water, mL/day	3087.25	2773.50	3189.50	3105.83	358.32	0.660	0.632
Intake (kg/body weight)
Dry matter	3.38	3.33	3.12	3.11	0.055	0.005	0.064
Crude protein	0.50	0.52	0.47	0.46	0,010	0.013	0.599
NDF	1.45	1.37	1.22	1.27	0,140	0.253	0.628

• NDF = neutral detergent fiber; ADF = acid detergent fiber TC = total carbohydrates NFC = non-fibrous carbohydrates. SEM: standard error of the mean; L: linear effect; Q: quadratic effect.

Table 4
Coefficients of total digestibility of dry matter (DM), organic matter (OM), crude protein (CP), ether extract (EE), neutral detergent fiber (NDF), acid detergent fiber (ADF), total carbohydrate (TC) and non-fibrous carbohydrate (NFC) in lambs fed diets containing pepper.

Digestibility   (g/kg DM)	Pepper (g/kg DM)				SEM	p-values
	0.0	2.0	4.0	6.0		L	Q
DM	736.2	768.4	772.6	744.1	1.83	0.738	0.124
OM	742.7	772.4	731.5	737.8	2.30	0.334	0.361
CP	657.7	739.6	660.3	643.0	2.71	0.155	0.026
EE	842.4	818.4	792.0	815.2	4.06	0.344	0.352
NDF	600.3	648.1	593.5	597.4	3.58	0.286	0.119
ADF	306.0	468.9	354.8	438.2	4.48	0.183	0.392
TC	759.9	776.6	750.0	760.2	1.48	0.898	0.975
NFC	913.5	923.4	918.5	875.5	1.20	0.376	0.026

• SEM: standard error of the mean; L: linear effect; Q: quadratic effect.

Despite altered nitrogen intake (P < 0.05; Table 5), the pepper inclusion levels did not alter (P > 0.05) the urinary nitrogen and retention of nitrogen. Fecal nitrogen (FN) showed a quadratic effect (P < 0.05, Table 5), with an estimated level of pepper (Ŷ = 8.0183 – 8.4164 * PP + 15.931 * PP²) of 2.4% g/kg DM giving a minimum value of 6.57 g/day. Increasing levels of PP caused a reduction (Ŷ = 17.735 – 3.993 * PP) in the absorbed nitrogen (P < 0.05; Table 5). The diets tested in this experiment provided a positive nitrogen balance, with an average value of 5.70.

Table 5
Effect of pepper on nitrogen (N) utilization by confined lambs.

Variable	Pepper (g/kg DM)				SEM	L	Q
	0.0	2.0	4.0	6.0
NI, g/day	25.04	25.40	23.50	23.36	1.63	0.003	0.472
FN, g/day	8.40	6.58	7.84	8.32	0.52	0.537	0.011
UN, g/day	9.08	10.51	12.36	11.41	2.53	0.236	0.459
RN, g/day	7.56	8.31	3.30	3.63	2.45	0.073	0.908
AN, g/day	16.64	18.82	15.65	15.03	1.70	0.011	0.030
NB/NI	0.30	0.32	0.15	0.16	0.08	0.085	0.943

• NI: nitrogen intake; FN: fecal nitrogen; UN: urinary nitrogen; RN: retained nitrogen; AN: absorbed nitrogen; NB: nitrogen balance. SEM: standard error of the mean; L: linear effect; Q: quadratic effect.

Increasing levels of PP did not alter (P > 0.05) the pH and NH₃-N concentration of the ruminal fluid. However, there was an effect (P < 0.05) of time on the pH value and NH₃-N ruminal (Table 6). The minimum pH value of the rumen fluid was estimated (Ŷ = 6.9528 − 0.2152 * PP + 0.0208 * PP²) at 5 h and 17 min after feeding (Figure 1). The maximum production of NH₃-N in ruminal (38.32 mg/100 mL) was estimated (Ŷ = 23.6699 + 7.3847 * PP – 0.9255 * PP²) at 4 h 00 min after the morning feeding, that is, 1 h and 15 min before the lowest pH values of the rumen fluid.

Table 6
Ruminal fluid pH and concentration of ammoniacal nitrogen (NH₃-N) values of lambs fed rations containing pepper.

Item		Pepper (g/kg DM)				SEM	P value
	0.0		2.0	4.0	6.0		L	T	L*T
pH	6.66		6.53	6.54	6.64	0.205	0.734	0.000	0.546
NH3-N	29.89		29.02	31.22	33.65	4.135	0.694	0.002	0.114

• SEM: standard error of the mean; L: levels of pepper; T: time after feeding; L*T: Interaction between levels and time.

4. Discussion

The reduction in DM intake of the animals was attributed to the pepper pungency factor, which is associated with the presence of capsinoids in the fruits of this plant (Aguiar et al., 2014). Capsinoids limit food intake in animals (Rodriguez-Prado et al., 2012). The amounts of pepper used in this research resulted in concentrations of 0.0, 8.9, 17.9, and 26.8 mg of capsaicin in the diet at 0.0, 2.0, 4.0, and 6.0 g/kg DM of inclusion of pepper in the diet of lambs, respectively. According to Chen et al. (2015), capsaicin can also alter satiety regulation mechanisms through the vanilloid transient potential receptor (TRPV1), which is a cellular sensor channel linked to touch, smell, sight, and taste.

Figure 1
Ruminal fluid pH and concentration of ammoniacal nitrogen (NH₃-N) values as a function of collection times after morning feeding of lambs fed diets containing pepper.

However, in studies carried out on beef cattle, Rodriguez-Prado et al. (2012) and Fandiño et al. (2008) reported a linear increase in the intake of DM with the addition of 125–500 mg and 375–500 mg of capsaicin and other essential oils. The reductions in the intake of OM, NDF, and CP with the inclusion of pepper in the diets are justified by the negative linear behavior of DM intake, as these fractions are contained in DM (Whiting et al., 2014). The water intake in the present study corroborated with that found in the study by Rodriguez-Prado et al. (2012) that using 0, 125, 250, and 500 mg of capsaicin associated with other essential oils did not result in an increase in water intake.

Additionally, when beef cattle were supplemented with a product containing 1.1% capsaicinoids a trend toward an increase in the average daily gain of the animals was observed (Westphalen et al., 2021). When lambs were supplemented with 300 mg/kg of pepper extract, no difference was observed in weight gain, average daily gain, or the consumption of dry matter (Ünlü et al., 2021). Eidsvik et al. (2022) found that dietary supplementation of rumen-protected capsicum did not affect dry matter intake, growth, or carcass weight for finishing steers; however, increasing the dose of capsicum may negatively affect carcass yield, quality grade, and marbling score.

The increase in crude protein digestibility up to 2.5 g/kg DM of inclusion of pepper in the diet was attributed to the reduction in the intake of rations and, consequently, a longer time of permanence of the ingestion in the gastrointestinal tract which is therefore related to the NDF content of the diet and ruminal microorganisms (Mertens, 1994). However, after this point, there was a reduction in the CP digestibility coefficient of the diets containing pepper, which was justified by the effect of pepper on rumen bacterial activity.

Capsaicin has antibacterial effects on gram-positive and gram-negative microorganisms (Deans & Ritchie, 1987). However, in some ruminant studies, this effect was not observed (Westphalen et al., 2021). Cardozo et al. (2006) indicated that the capsaicin present in pepper extract stimulated peptidolysis in cattle, providing a greater supply of small peptides and amino acids for the synthesis of ruminal bacteria. The greater availability of N in the rumen of lambs with lower levels of pepper inclusion in the diets may have contributed to greater microbial activity and, consequently, greater digestion of soluble carbohydrates for the initial levels of pepper inclusion in the lambs’ rations.

The reduction in N intake with the addition of PP in the diets was caused by the reduction in DM intake, which was associated with the effect of capsaicin on the control of satiety in lambs (Aguiar et al., 2014). The fecal N minimum point coincided with the increase in protein digestibility up to the level 2.4 g/kg DM of inclusion of pepper in the diet. The opposite was described by Costa et al. (2021) in a study with the inclusion of tannins in the diets of lambs, in which there was a decrease or slow degradation of the digestibility of crude protein; however, the lambs increased the excretion of fecal N.

Losses with urinary N should be smaller than those of fecal N, as this considers N from the oxidation of amino acids and the cost of maintenance associated with nitrogen recycling (Jennings et al., 2018). However, in this study, urinary N excretions (10.84 g/day) surpassed fecal N excretions (7.79 g/day). This result can be explained by the increase in ruminal NH₃-N level as a function of time. Capsaicin also contributes to the breakdown of the peptide chains in proteins (Cardozo et al., 2006).

Excess dietary non-protein nitrogen and fermented protein in the rumen are converted to ammonia, absorbed, and converted to urea by the liver and excreted in urine (Van Soest, 1994). The positive nitrogen balance demonstrated a balance between protein and energy in the diets, even with the inclusion of different levels of pepper in the diets.

The reduction in ruminal pH as a function of time after feeding was probably caused by a higher production of volatile fatty acids. The lowest ruminal pH value obtained at 5 h 17 min after feeding is in agreement with the data obtained by Geron et al. (2013), who observed lower ruminal pH values between 2 and 6 h after food intake. The type of feed influences ruminal pH, with lower values obtained at 0.5 and 4 h after feeding (Van Soest, 1994). The non-alteration of the ruminal pH value as a function of pepper levels in the lambs' diet differs from the results described by Rodríguez-Prado et al. (2012), who evaluated the inclusion of capsaicin extract in cattle (0, 125, 250, and 500 mg/animal/day) in high-grain diets and found a reduction in the ruminal pH value, which in turn ranged from 6.03 to 5.84. Differences in animal species, forage-to-concentrate ratio, and characteristics of the additives used influence ruminal pH.

The ammonia nitrogen value of the experimental diets remained above the optimal range of 15 to 23 mg/100 mL for maximum rumen fermentative activity (Geron et al., 2015) and above the concentration of 5.0 mg/100 mL established in the literature to avoid limiting microbial growth (Satter & Slyter, 1974). The inclusion of pepper in the diet of lambs, despite not influencing the concentration of NH₃-N in the rumen fluid, may have helped in the peptidolysis of dietary protein, providing more peptides and amino acids in the rumen environment (Cardozo et al., 2006) and, consequently, a greater amount of N in the rumen.

5. Conclusions

We conclude that the results obtained indicate that the inclusion of pepper in the diet of confined lambs negatively alters the dry matter and NDF intake without impairing nutrient digestibility, nitrogen utilization, and other ruminal parameters. Future research is recommended to better evaluate the use of pepper and capsaicin as phytogenic additives in feedlot lambs' diets.

Acknowledgments

The authors are grateful to Mato Grosso Research Foundation (FAPEMAT) for financially supporting this study and CAPES foundation for the first author scholarship.

References

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Edited by

• Editor:
  Tadeu Silva de Oliveira

Publication Dates

• Publication in this collection
  03 Feb 2025
• Date of issue
  2025

History

• Received
  19 Sept 2024
• Accepted
  13 Jan 2025