Jetana, T.1*, S. Usawang1 & M. Techakampu2
1Research and Development Centre for Livestock Production Technology,
2Department of Obstetrics, Gynaecology and Reproduction, Faculty of Veterinary Science, Chulalongkorn University, Bangkok 10330, Thailand
*Email of corresponding author: [email protected]
Introduction
The rain tree (Saman samanea) is a tropical legume and the pods of the rain tree are easily available in the dry season. It is generally known that these pods have been appreciatively eaten by cattle (Staples and Elevitch, 2006). Studies demonstrated that the rain tree pod has the advantage of enhancing microbial growth in the rumen of buffaloes (Jetana et al., 2011a,b) and cattle (Jetana et al., 2010). The objectives of the experiment were to determine and compare the effects of supplementation with either commercial pellets (CCP) or the pellets produced from rain tree pods (RTPP) on the whole tract apparent digestibility of DM, OM and fibre, ruminal microbial production, milk production, quality of milk and capital cost of milk production.
Materials and methods
The experiment was conducted with 14 Saanen dairy goats (weighing 29.0–58.0 kg). The animals were randomly divided into two groups of 7 animals each. Group 1 (38.4 0.62 kg) was fed ad libitum with 2.46 kg corn silage (fresh weight) and supplemented with 1 kg of CCP (fresh weight), and Group 2 (40.9 0.74 kg) was fed ad libitum with 2.46 kg corn silage (fresh weight) and supplemented with 1 kg of RTPP (fresh weight). The crude protein content in CCP (15.0%) and RTPP (15.2%) was similar. The CCP contained 865 g DM/kg, 31 g ash and 440 g NDF based on g/kg DM basis while RTPP contained 764 g DM/kg, 62.3 g ash, 200 g NDF, 45.3 g phenolic compounds, 10.8 g condensed tannins, 170 g total sugar and 90 g sucrose per kg DM basis.
Two studies were conducted over 35 days. The first study determined milk production and milk quality for 35 days, whilst the second study determined the nutrient digestion and microbial production in the rumen. The samples were collected for digestion and microbial production in the rumen for 7 days, during day 28 to 35 of experimentation. The animals were housed in individual pens during the experimental period with facilities for separate urine and feces collections. The feed intake and milk production of each goat were recorded daily and 20 mL of milk were taken as a sub-sample into each plastic container for chemical analysis. Total fat was determined by a simple UV spectrophotometric method (Forcato et al., 2005); milk protein was calculated by total N in milk (Micro Kjeldahl, AOAC 2000) multiplied by 6.38. Total solids were determined by taking 10 g of milk samples in 50-ml Erlenmeyer flasks and kept at 80ºC in a hot air oven for 24 hours. The ash in the milk samples was determined by burning them to a constant weight in a muffle furnace at 550ºC for 8 hours. Milk lactose was calculated by subtracting total fat, protein and ash from total solids.
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On day 28 to 35, urine was collected in plastic bags containing 100 mL of 7% HCl to maintain a pH below 3. Total daily urine was weighed and sub-samples were taken, diluted 5 times with distilled water, and stored at 4ºC for PD analysis (IAEA-TECDOC-495, 1997).
Total daily faeces were weighed and sub-samples (20%) were then stored at 4 ºC for chemical analysis. Ten percent of the representative aliquots of offered feed, refused feed and faecal samples were collected and stored at –20ºC. At the end of each sampling period, samples from each animal were pooled and dried in a hot air oven at 65ºC, for 72 hours, prior to analysis for dry matter (DM), ash, nitrogen (N), and neutral detergent fibre (Van Soest et al. 1991). Fresh drinking water was provided throughout the experiments. Purine derivatives in the urine were measured as allantoin, uric acid, xanthine and hypoxanthine and microbial- N in the rumen was calculated using equation of Jetana et al. (2003).
Results and Discussion
Table 1 shows that the RTPP intake was greater than that of CCP intake, but none of the supplemental diets affected corn silage intakes. However, digestibility coefficients of DM and OM were generally lower in goats in the RTPP than those in the CCP group. It is possible that the rain tree pods contained higher available sugar (sucrose) than the CCP diet decreasing the pH in the rumen (Hindrichsen and Kreuzer, 2009) and thus the activity of cellulolytic microbes leading to depressed fibre digestion (Table 1) (Hoover, 1986).
Lower microbial production recorded in goats supplemented with RTPP (Table 1) was in contrast with the reports by Jetana et al. (2010, 2011a,b) who demonstrated that a high sugar and protein content in the rain tree pod has advantages of enhancing the efficiency of microbial yield in the rumen of buffaloes and cattle. The contradicting results may be due to i) different animal species used, ii) different processing methods for the rain tree pods, iii) the rate of passage in animals fed the RTPP diet may be faster than in those fed the CCP diet resulting in excess non-fermentable N sources in the rumen to be fermented in the hindgut, iv) binding of condensed tannins to available nutrients (N) in the RTPP supplemental diet and v) the high content of tannins inhibiting some microbial activity (Waghorn, 2008). Though the average milk production (mL/day/BW0.75) (Figure1) and capital cost of milk production (US dollar/kg milk) were lower (Table 1), the contents of protein, lactose and total solids in the milk were higher in goats supplemented with RTPP than in those supplemented with CCP (Table 1). The high lactose in milk is not surprising as there is high sucrose in the RTPP while the high protein in milk is probably due to the escape of tannin-protein complexes in RTPP diet from rumen fermentation, subsequently digested in the small intestine and absorbed for production of protein in milk.
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Table 1. Intake, coefficient of digestion, ruminal microbial nitrogen production, milk composition and capital cost of milk production in Saanen goats fed corn silages and supplemented with two types of concentrate pellet
Type of concentrate pelletCCP RTPP SED1
Body weight live(kg) 38.4 40.9 1.56
Metabolic body weight (kg) 15.4 16.1 0.46
Total dry matter (DM) 1.30b2 1.44a 0.03
Concentrate pellet DM 0.70b 0.83a 0.02
Corn silage DM 0.59 0.60 0.01
Total organic matter (OM) 1.22b 1.35a 0.02
Total neutral detergent fibre (NDF) 0.69b 0.75a 0.02
The coefficients of (decimal)
DM 0.76a 0.68b 0.02
OM 0.80a 0.72b 0.02
NDF 0.84a 0.78b 0.02
Purine derivatives in urine (mmol/day)
Allantoin 19.2 15.5 1.92
Uric acid 7.40a 1.11b 0.58
Xanthine + Hypoxanthine 0.89 1.01 0.11
Total Purine derivatives 27.4a 17.6b 1.91
MN in the rumen (N g/day)3 29.1a 17.2b 2.30
Chemical composition of milk (g/kg)
Fat 45.6 42.1 4.62
Protein 34.0b 39.7a 2.76
Lactose 23.3b 34.7a 2.94
Total ash 9.56 9.97 0.50
Solids non fat 64.0b 84.4a 2.69
Total solids 110b 127a 4.88
Capital of milk produced
Milk yield (g/day) 922a 570b 1.92
Milk produced capital (US dollar/kg milk) 0.40a 0.35b 0.02
1 Standard error of difference
2abValues within the same row with different superscripts are significantly (P<0.05) different. Values within the same row without superscripts are not significantly (P<0.05) different
3 Purine derivatives in milk was not included for calculation
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Figure 1. The average milk production (mL/day/BW0.75) of dairy Saanen goats fed different types of concentrate pellets.