Area description
The climate of the region is sub-humid warm with summer rains. There were three collection sites with a distance of 35 km among them. Two sites (Tequila and San Cristobal) were located in the state of Jalisco and one site (Teul de Gonzalez Ortega) was located in the state of Zacatecas, México. In these sites, the annual mean rainfall is 600 mm and the average altitude was 1,750 MASL.
Harvest procedure and sample handling
Sampling was conducted the first day of each month, from April, 2014 until March, 2015. The foliage samples were collected manually from the same 15 trees located in a plot of about 50 m × 50 m at each collection site. Leaves were stored in identified paper bags and kept at 4°C on ice to preserve them until processing in laboratory. The leaves were placed in a circulating air oven at 60°C to constant weight, ground in a Wiley mill with a 2 mm mesh, and stored at ambient temperature in identified paper bags for subsequent determinations.
Chemical analysis
Samples were analyzed in triplicate to determine dry matter (DM) and ash (
AOAC, 1995) and neutral detergent fiber (NDF) and acid detergent fiber (ADF) (Van
Soest et al., 1991). Hemicellulose (NDF - ADF) and OM (DM - ash) were determined by difference. Non fiber carbohydrate (NFC) were calculated by the equation of
Sniffen et al., (1992). The Dumas method (
AOAC, 1995) was used for to determinate crude protein (CP) with a FP-528 LECO nitrogen analyzer. The ether extract (EE) was determined using the extractor of Ankom
xt15 (AOCS AM 5-04). The concentration of condensed tannins (CT) was estimated using the butanol-HCl method reported by
Porter et al., (1986).
In vitro digestibility
The
in vitro procedure adopted in the present study was as proposed by
Theodorou et al., (1994). Since the
in vitro production of gas is proportional to the DM degraded, the net yield of gas at 24 h (ml/700 mg) incubation of the substrate was used to calculate the metabolizable energy (ME) and IVOMD using the equations proposed by
Menke and Steingas (1998). The short chain fatty acids (SCFA) were calculated using the equation of
Makkar (2005).
Dynamics in situ degradability
The DM degradability was determined with the nylon bag technique (
Ørskov, 2000). Foliage samples (5 g) were introduced in nylon bags and incubated in the rumen of five rams equipped with ruminal cannula for 0, 6, 12, 24, 48, 72 and 96 h. To determine the parameters of
in situ degradability and passage rate, the data obtained were processed with the Neway computer program, applying the equation proposed by
Ørskov and McDonald (1979).
Intake and palatability
The cafeteria technique was used to estimate the intake and preference of diets by sheep
(Ganguli et al., 2010).
Test 1: Inclusion levels of Q. resinosa Liebm
The leaves used in this test were collected in the first week of October. Eight uncastrated Rambouillet lambs (41±1.2 kg) with no history of consumption of
Quercus leaves were used. The experimental diets consisted of incremental levels of foliage (0, 10, 20, 30 and 40%) that replaced sorghum hay of the basal diet (Table 1). The basal diet was formulated to meet the gain requirements of lambs (NRC, 2007).
Test 2: Harvest dates of Q. resinosa
The leaves of
Q. resinosa used in this test were the leftovers for the chemical composition procedures and were grouped by season of the year. Eight uncastrated Rambouillet lambs (42.0±0.8 kg) with no history of consumption of
Quercus leaves were fed four experimental diets containing a 40% monthly mixture of each season of the year of
Q. resinosa leaves and 60% of the basal diet described in Table 1.
In both tests, the feeder had eight dividers, at each of which were placed 0.1 kg of each one of the experimental diets, the position of the troughs was randomized each day to avoid “habit reflex”
(Brown et al., 2016). Observations were made for 30 minutes (0830-0900) each time. Once this time was elapsed, the diet leftovers that were in the different compartments of the feeder were removed, weighed and identified. Animal behavior was recorded with eight security cameras, one per each pen. Samples of approximately 100 g of diet offered and refusals were obtained and dried for 48 h at 60°C. The DMI by each animal was measured by subtracting the difference between the offered and refused, adjusting losses inherent in the spontaneous dehydration of forages in time.
The coefficient of consumption was estimated as the relationship between the consumption of each individual treatment, divided by the average consumption of all treatments. Those treatments with a coefficient of consumption greater than one, were considered greater than other treatments.
The coefficient of effective time consumption was calculated as the ratio between the time consumption of each individual treatment, divided by the average time of consumption of all treatments. Animals spend more time consuming than other animals, when the coefficient is greater than one. Data of DMI were used to determine the relative palatability index (RPI) of different treatments, which was obtained by dividing the data of the treatment with higher DM consumption with the other treatment, and multiplied by 100
(Abdulrazak et al., 2001).
Statistical analysis
Data were analyzed as a randomized block design using the GLM procedure of the SAS statistical software [SAS/STAT® User’s Guide (8.1Edition)], SAS Inst. Inc., Cary, NC, USA. The collection site was considered as block effect for the chemical composition,
in vitro and
in situ degradability studies. In the study of intake and palatability, the animals were used as block effect. When significant effects were observed, a comparison of means with the Tukey method using the MEANS statement was made.
P values observed were considered different if P<0.05.
