Performance and nutrient digestion of lambs fed incremental levels of wild cactus (Opuntia leucotrichia)

Abstract

In a performance trial, 50 intact Rambouillet×Dorper male lambs (19±2.8 kg), were randomly assigned to experimental diets containing 0, 10, 20, 30 or 40%, Opuntia leucotrichia (O. leucotrichia; dry matter basis). At day 91 animals were slaughtered for carcass and meat quality evaluation. In trial two, five ruminal cannulated Rambouillet male rams were used in a digestion study. Dry matter intake, average daily gain and feed efficiency of lambs decreased (P<0.05) generally with increasing levels of O. leucotrichia. Carcass dressing was increasing as O. leucotrichia was augmented. Water intake decreased as consumption of O. leucotrichia increased. Crude protein was digested higher (P<0.05) in lambs fed 40% diet than other lambs. Ruminal pH and ammonia-N were not significantly different among treatments. Inclusion of O. leucotrichia on feedlot lamb diets is a good option for production systems if this resource is available.

Keywords:

• Opuntia leucotrichia
• lambs
• growing performance
• nutrient digestibility

Introduction

Water scarcity, poor quality soils and inadequate supply of feed are the major constraints of grazing livestock developed in arid and semiarid regions of Mexico. In certain regions of northeastern Mexico, cladodes of Opuntia plants are used by domestic livestock and wildlife animals as food and water supply (Reynolds and Arias 2001).

Opuntia leucotricha (O. leucotrichia) is the most widely distributed and is an extremely drought tolerant, highly productive and multipurpose succulent plant (Serna and Echavarría 2002). However, when cactus pear is fed excessively as the sole feed it may cause weight loss, decreased milk fat (Santos et al. 1990) diarrhoea and bloating can occur (Tegegne et al. 2007).

In Mexico cladodes of O. leucotrichia are traditionally used as emergency feed for livestock, especially during drought periods; however, scarce research has been carried out using O. leucotrichia on high production systems. Thus, the aim of the study was to evaluate growing, digestion and carcass responses by feedlot lambs fed diets containing graded levels of cladodes of O. leucotrichia.

Materials and methods

Two simultaneous trials were conducted to evaluate five isoenergetic and isonitrogenous diets containing: 0, 100, 200, 300 or 400 g/kg of O. leucotrichia cladodes on dry matter basis.

In a growth trial, 50 recently weaned intact male lambs (19±2.8 kg) of the cross Rambouillet×Dorper were randomly and equally allotted to one of five treatment diets. After a period of 10 days for adaptation lambs were fed for an experimental period of 90 days. Diets were offered to lambs twice a day (08:30 and 16:00 hour) considering a 5% more than the previous day. Lamb intakes were recorded daily. At the beginning of adaptation and experimental periods, individual lamb weights were measured and recorded and subsequently every 15 days. Weight of lambs at the beginning of adaptation period was used as a covariate to adjust average daily gain (ADG). On day 91, all animals were food deprived overnight with free access to water and slaughtered. Body weights were obtained immediately before slaughter and carcass and non-carcass components weights were obtained immediately after slaughter. Carcass were hanged and refrigerated at 4°C. Non-carcass components weights were recorded. Carcass pH was taken at 45 min post mortem from semimembranosus muscle. A semimembranous muscle cut was obtained at 6 and 24 hour, for cooking loss after cooking meat at 76°C during 45 min in water (Destefanis et al. 2003), moreover, hand water-holding capacity was determined by the modified Grau and Hamm technique proposed by Alarcón et al. (2005).

In the digestion trial, five ruminal cannulated Rambouillet rams (80.5±2.3 kg) were used in a 5×5 Latin Square design that lasted 21 days in each period (14 days of adaptation and 7 days for collections). Samples were grouped by period and composites were stored for further analyses. On day 15 of each period, after morning feeding, rumen fluid samples were obtained at 0, 1.5, 3, 6, 9, 12, 15 and 18 hour, strained through two layers of cheesecloth, pH measured immediately after sampling, and then samples of 30 ml were acidified with eight drops of sulphuric acid 97% and stored in a freezer (−4°C). Afterwards, samples were analyzed for ammonia-N following the procedures described by Food and Agriculture Organization (1986).

Concentrations of dry matter, organic matter, crude protein (Association of Official Analytical Chemists 1997), neutral detergent fibre and acid detergent fibre (Van Soest et al. 1991) in diets, orts, and faeces were determined and their apparent digestibility coefficients were calculated using formulas by Van Soest (1994).

Data of the growing performance of lambs were statistically analyzed using a completely block design, and rumen fermentation and digestion data with a replicated 5×5 Latin Square design using the General Linear Model (GLM) procedure of Statistical Analysis System (2000). The Tukey's test was used to adjust for multiple comparisons (Steel and Torrie 1980).

Results and discussion

Lambs without O. leucotrichia showed about 40% better performance compared to lambs fed O. leucotrichia (Table 1). The dry matter intake (DMI) was less as O. leucotrichia was increased in diets. Lambs without O. leucotrichia or with 40% O. leucotrichia required less feed to gain weight (Table 1). In this study, the addition of O. leucotrichia to lamb diets decreased weight gain.

Table 1.  Growing performance parameters and carcass characteristics of lambs fed diets with graded levels of Opuntia leucotrichia cladodes.

	Percentage in diets (DM)
Item	0	10	20	30	40	SEM
Initial weight (kg)	19.2	19.3	19.3	19.2	19.2	0.2
ADG (g d^−1)	329^a	254^b	213^c	185^c	227^bc	14.0
Dry matter intake (g day^−1)	1344^a	1153^b	1099^b	955^c	982^c	22.0
Feed efficiency	4.1^c	4.5^b	5.2^a	5.2^a	4.3^bc	0.1
Carcass characteristics
Hot carcass dressing (%)	46.9^c	47.2^c	48.6^b	48.4^b	49.6^a	0.3
Cold carcass dressing, 24 hour (%)	45.4^c	45.6^c	47.2^b	46.9^b	48.2^a	0.3
Pluck (%)	7.5	7.6	7.7	7.4	7.6	0.3
Liver (%)	4.5	4.5	4.4	4.4	4.3	0.1
Empty rumen^1 (%)	6.8^b	7.3^a	7.3^a	7.5^a	7.6^a	0.1
pH	6.2	6.3	6.1	6.3	6.4	0.1
Adjusted fat thickness^2 (mm)	5.1^a	4.9^a	4.4^b	4.4^b	3.8^b	0.2
Cooking loss (%)	27.6	28.6	27.9	28.2	27.5	0.2
Water holding capacity (%)	61.7	61.5	62.3	61.9	61.9	0.4
Drip loss (%)	5.1	5.2	5.1	5.3	5.2	0.1
Note: Means in a row with different superscript letters are significantly different; SEM=standard error of the mean.
^1As percent of carcass weight.
^2Variable adjusted for hot carcass weight.

The inclusion of O. leucotrichia enhanced carcass dressing, the highest percentage was obtained with O. leucotrichia 40 diet (Table 1) similar to the report of Tien and Beynen (2005). On the other hand, Veras et al. (2005), Einkamerer et al. (2009) and Fuentes-Rodriguez et al. (2009) on lambs found similar carcass dressing and organs weight on diets with and without cactus.

Rumen as a percent of the carcass weight was higher in lambs with O. leucotrichia diets (7.4%) compared with control diets (6.8%). Some changes at the histological structure of the rumen was reported by Neiva et al. (2006), who found more developed papillae in rumen of sheep fed 30–60% diets compared with no cactus diet. Adjusted fat thickness decreased as O. leucotrichia was included in the diet.

In this study, as O. leucotrichia was increased in diets, DMI of lambs was reduced (Table 2). However, all treatment diets satisfied maintenance requirements for DMI; meanwhile, diets with 0, 10 or 20% O. leucotrichia provided additional nutrients for growth. Conversely, Tegegne et al. (2007) in sheep reported DMI improvement as cactus level increased. However, in former studies, cacti substituted grass hay or straw, and in this study corn grain and oat hay were replaced by cactus.

Table 2.  Nutrient feed intake, ruminal parameters and apparent digestion coefficients of lambs fed diets with graded levels of Opuntia leucotrichia cladodes.

	Percentage in diets^a
Item	0	10	20	30	40	SEM
Dry matter intake (g kg^0.75 d^−1)	114^a	108^b	99^c	85^d	83^d	0.9
Water intake (ml kg^0.75 d^−1)	308^a	273^b	170^c	105^d	65^e	6
Rumen parameters
Ammonia N (mg dl^−1)	14.8^a	14.2^a	14.4^a	12.9^b	13.0^b	0.3
pH	5.9	5.9	6.2	6.3	6.1	0.2
Digestion coefficients (%)
Dry matter	65	65	64	64	64	2
Organic matter	68	67	68	68	67	2
Crude protein	69^b	68^b	68^b	68^b	72^a	1
Neutral detergent fibre	58	61	59	58	61	1
Acid detergent fibre	47	45	46	46	44	2
Note: Means in a row with different superscript letters are significantly different; SEM = standard error of the mean.

Water intake of lambs decreased as O. leucotrichia increased in diets (Table 2). This finding was also reported by Tegegne et al. (2007) in sheep. It seems that water from cactus food represented an important water supply for body needs. De Kock (2001) reported that wool sheep survived for 500 days on cactus cladodes alone. Thus, O. leucotrichia as a supplemental feed is of paramount importance in arid and semiarid like Central-North part of México where water quality and provision are limited (Aguilera et al. 2007).

Ruminal NH₃-N decreased on higher supplementation levels of O. leucotrichia without change in pH. Bispo et al. (2007) in sheep also reported reduction in ruminal NH₃-N as spineless cactus consumption increased.

The crude protein (CP) was digested in higher amounts by lambs fed 40% O. leucotrichia (Table 2). As discussed above higher inclusion of fish meal in the 40% O. leucotrichia diet could have caused the lambs to digest more CP.

Inclusion of O. leucotrichia to feedlot lamb diets supported reasonable growing performance and nutrient digestibility. Thus, O. leucotrichia could be considered as a good alternative that provides nutrients and water to ruminants in production systems under scarcity conditions where this resource is available.

Acknowledgements

We would like to thank to the National Council for Science and Technology (CONACyT), for the economic support provided in the graduate program at UANL.