The present experiment was performed in the educational-research station of Agricultural Sciences and Natural Resources University of Khuzestan (ASNRUKH) according to The Care and Use of Agricultural Animals in Research and Teaching guidelines (FASS 2010), and the study was approved by the ASNRUKH Animal Care Committee
Twenty-seven Arabi male lambs 6 ± 1.3 months old and a weight of 28.8 ± 1.99 kg were selected for the present experiment. The feeding and management conditions of the selected lambs were the same, and lambs were randomly divided into three groups with no significant difference in mean initial weight. The duration of the experimental period was 75 days, including 15 days for adaptation to the diet and environment and 60 days for the sampling and data recording and collecting. The experimental diets (Table 1) were formulated according to the standard requirements of small ruminants (NRC 2007).
Table 1
Feed ingredients and chemical composition of the experimental diets fed to lambs
| Treatments |
| Percentage of Siris replacement with alfalfa (Siris in the whole ration) |
Feed ingredients (%DM) | Control (without Siris ) | 50% Siris | 75% Siris |
Alfalfa hay | 30 | 15 | 7.5 |
Siris | 0 | 15 | 22.5 |
Wheat straw | 20 | 20 | 20 |
Barley grain | 20 | 20 | 20 |
Corn grain | 3.5 | 3.5 | 3.5 |
Canola meal | 5 | 5 | 5 |
Wheat bran | 20 | 20 | 20 |
Salt | 0.5 | 0.5 | 0.5 |
Mineral + Vitamin premixa | 1 | 1 | 1 |
Chemical composition | | | |
Dry matter (%) | 96.52 | 97.00 | 97.08 |
Ash (%) | 9.50 | 9.04 | 9.04 |
Crude protein (%) | 13.37 | 13.67 | 13.82 |
NDF (%) | 54.03 | 54.73 | 55.09 |
ADF (%) | 24.10 | 23.17 | 22.70 |
ME (Mcal/Kg)b | 2.41 | 2.41 | 2.42 |
NEl (Mcal/kg)c | 2.54 | 2.48 | 2.39 |
Percentage of digestibility of organic matter (DOM)d | 60.09 | 58.47 | 56.66 |
Apparent digestibility of organic matter (IVOMAD)e, (%) | 59.85 | 58.12 | 56.33 |
Short Chain Fatty Acids (SCFA) (mmol/200 mg DM)f | 0.81 | 0.77 | 073 |
a Premix contained (per kg): Vitamin A, 500,000 IU/mg; vitamin D3, 100000 IU/mg; vitamin E, 100 mg/kg; Ca, 180 g/kg; P, 60000 mg/kg; Na, 60000 mg/kg; Mg, 19000 mg/kg; Zn, 3000 mg/kg; Fe, 3000 mg/kg; Mn, 19000 mg/kg; Cu, 300 mg/kg; Co, 100 mg/kg; Se, 1 mg/kg; I, 100 mg/kg; antioxidant, 400 mg/kg; carrier, up to 1000 g b ME (MJ/Kg DM) = 0.04 + 0.1639GP + 0.0079CP + 0.0239EE (Mixed feed) c NEL (MJ/Kg DM) = -1.04 + 0.1195GP + 0.0051CP + 0.0152EE (Mixed feed) d DOM (%) = 0.9042 GP+ 0.0492CP+ 0.0387CA+16.49 (n=85/r2=0.93) (Forage) e IVOMAD (%) = 14.88 + 0.8893GP + 0.0448CP + 0.0651 Ash f SCFA (mmol/200 mg DM) = 0.0222 GP – 0.00425 |
The three experimental treatments were diets 50 and 75% replacement of Siris foliage instead of alfalfa forage in the control diet (no Siris), including 1- control diet (no Siris), 2- diet 50% replacement (or ration containing 15% Siris) and 3- diet 75% replacement (or ration containing 22.5% Siris). During the experimental period, the lambs were kept in metabolic cages, fed ad libitum and had free access to drinking water.
Lamb feed intake was measured daily by weighing the feed, and the remaining amount was measured after 24 hours. In order to determine the digestibility of feed nutrients, in the last days of the experimental period (days 49-56), the method of collecting whole feces was used. The feces of lambs and the rest of their feed were collected, weighed, and recorded every 24 hours. A constant percentage of them were then stored in the cold storage for seven days. At the end of the seventh day, samples from each animal were mixed and used for subsequent measurements. Nutrient digestibility was calculated from differences in feed, residue, and feces.
For in vitro digestion and fermentation measurement, the samples were dried (48 hours, 60°C) with an oven (Fanazma Tajhiz Gostar Co., 24 liters, Iran) and ground (2 mm mesh (2). (AOAC 2012). Chemical composition of experimental diets containing Siris, including crude protein (CP, FOSS kjeltec 2300 analyzer, Sweden; method 990.03- AOAC 2012) (Kajeldal method, Automatic Kajeltec V50, Tehran Laboratory Industries, Iran. method 990.03- AOAC 2012), ether extract (Soxhlet method, method 954.02- AOAC 2012), dry matter, ash (method 942.05- AOAC 2012), acid detergent insoluble fibers (ADFom, AOAC 2012 # 973.18) and total tannin It was measured by standard methods (AOAC 2012). Neutral detergent insoluble fibers (NDFom, corrected for ash, without alpha-amylase, and with sodium sulfite) were measured by the usual method (Van Soest et al. 1991).
In the last days of the experiment (on the 56th day), the rumen fluid of lambs was sampled via stomach tube at 3 hours after the morning feeding. The rumen pH (pH meter, WTW, Germany) was recorded immediately to measuring ammonia nitrogen using the phenol-hypochlorite method (Spectrophotometer, Bio-Rad, Libra S22, Cambridge, England), the ruminal fluid was filtered with four layers of Cheesecloth and acidified with an equal proportion of 0.2M hydrochloric acid (Broderick and Kang 1980).
On the 56th day, rumen fluid of all lambs was collected via stomach tube before the morning feeding. In order to stabilize protozoa, an equal amount from ruminal fluid was mixed with 37% formaldehyde solution (diluted 50: 50 with distilled water), and protozoa were counted by the Neubauer counting chamber (Dehority 2003) using an optical microscope (NIS-Elements F 3.0, Japan).
On the 65th day, to evaluate the effect of experimental diets on blood parameters, the blood samples were taken from the jugular vein in tubes containing EDTA-Ca 10%, about 3 hours after the morning meal. Blood samples were centrifuged at 3000 rpm. for 15 minutes (Hermel 236 HK, Germany), and the plasma was separated. Blood parameters were measured using an auto-analyzer (Mindray BS200, Guangzhou, China).
The lambs were weighed before the experiment and then every 15 days before morning feeding with 14-16 hours of fasting, to study growth and fattening performance. Considering the amount of feed consumed and weight changes, feed conversion ratio, feed efficiency, and average daily gain and final weight were calculated (Eynipour et al. 2019).
On the last day of the experiment, the lambs were slaughtered after about 12 hours of starvation, and then differents carcass parts were weighed (Fisher and de Boer 1994).
After slaughtering the lambs, the color of the order muscle, located between ribs 12 and 13, was measured according to the L* (brightness), a* (redness), and b* (yellowness) systems using a colorimeter (Konica, model CR 400, Japan), with three replicates for each sample. The chromaticity and hue were calculated according to the colorimetric indexes (AMSA 2012).
Data were statistically analyzed using GLM procedure of SAS (version 9.4). The means were compared by Duncan's multiple range test at the error level of 0.05 for significant effects.
Yij = µ + Ti + Ɛij
In this model, Yij: the observed value, µ: the population mean, Ti: the effect of the ith treatment, Ɛij: the residue error.