Nutritional value of common oak (Quercus calliprinos) browse as fodder for goats: Experimental results in ecological perspective

June 29, 2017 | Autor: Mordechai Gutman | Categoria: Animal Production, Oak, Small Ruminant Production, Nutritional Value
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SmallRuminantResearch, 11 (1993) 95-106

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© 1993 Elsevier Science Publishers B.V. All rights reserved. 0921-4488/93/$06.00

Nutritional value of common oak (Quercus calliprinos) browse as fodder for goats: Experimental results in ecological perspective A. Perevolotsky ~, A. Brosh b, O. Ehrlich c, M. Gutman a, Z. Henkin c and Z. Holzer b aDepartment of Natural Resources, Agricultural Research Organization, The Volcani Center. Bet Dagan, Israel bDepartrnent of Beef Cattle, ARO, Newe Ya'ar Experiment Station, Haifa, Israel CGalilee Technological Center (MIGAL), Qiryat Shemona, Israel (Accepted 10 September 1992 )

ABSTRACT Feed intake, in vivo digestibility, and nitrogen balance of common oak (Quercus calliprinos) browse and vetch hay were determined in two trials using native Mamber black goats. Vetch hay served as a control treatment for evaluating the methodological accuracy of the experimental system. Individual average intake was 63 and 94 g/day/kg (W°TS), organic matter digestibility 46% and 61%, and the nitrogen balance (N retention as g/day/goat ) was - 0 . 6 and 4.9 for oak and vetch hay, respectively. Accordingly, Q. calliprinos, used as the sole feed for goats could supply the energy but not the protein requirements for maintenance. Intake, digestibility and nitrogen balance of the common oak were similar to values in studies of other oak species in the Mediterranean region, but deviated from data in studies in the USA. Possible reasons for this difference, such as different content of secondary compounds such as tannins, goat breed and duration of adaptive interactions between goats and plants, are discussed. Key words: Oak; Browse; Goat; Digestibility; Nitrogen balance

INTRODUCTION

C o m m o n oak (Quercus calliprinos Webb ) is a c o m m o n tree or shrub that occurs as a leading and d o m i n a n t c o m p o n e n t in the Mediterranean scrub woodland of Israel (Zohary, 1966 ). This oak is a vicarius species to the Quercus coccifera (Kermes oak) which is very c o m m o n in the central and western Mediterranean Basin (Zohary, 1959). Oak browse (leaves and twigs) are often readily grazed by livestock and can constitute a significant part of their diet. Correspondence to: A. Perevolotsky, Department o f Natural Resources, Agricultural Research Organization, The Voicani Center, P.O. Box 6, Bet Dagan 50250, Israel.

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Areas of natural scrub woodland in Israel, as in other Mediterranean regions, are characterised by a high percentage of woody growth, including trees, bushes and shrubs. Among these, the common oak (Quercus calliprinos) is an important and dominant element: approx. 70% of the vegetation cover in the Mediterranean scrub woodland in Israel consists of common oak (Zohary, 1959). Considerable areas of natural oak woodland in Galilee, Mt. Carmel and the Judean Hills may serve as pasture for cattle and goats (Seligman et al., 1959 ). Since the production of herbaceous species in Mediterranean woodland is relatively low, oak leaves and young stems are an important feed source for animals that graze this ecosystem. Oak leaves are important, especially in summer and fall when the remaining dry herbaceous plants have very limited nutritional value. The goat is the domestic animal most commonly found in areas in which the woody element is dominant (French, 1970; Harrington, 1982 ). The present study is an assessment of the nutritional value of oaks and their potential contribution to the diet of black Mamber goats, a common breed in the Mediterranean region. A digestibility and nitrogen balance trial was conducted, in which oak browse as the sole feed was compared with vetch hay, a good quality fodder. Goats perform reasonably well on scrub woodland (Vecht et al., 1990) despite low digestibility of this woody species, as determined by Tilley and Terry in vitro methods. This anomaly was the principal reason for conducting an in vivo study of the nutritional value of oak leaves (Nastis and Malechek, 1988 ). Oak leaves contain a significant amount of tannins (Feeny, 1970; Martin and Martin, 1983 ), which may affect the in vitro digestibility analysis (Sidahmed et al., 1981; Robbins et al., 1987), thus making the in vivo trial even more relevant. In the last decade there have been some attempts to determine the nutritional value of leaves from various species of oak (Nastis and Malechek, 1981; Sidahmed et al., 1981; Meuret, 1988; Villena and Pfister, 1990). In some cases the experiments assessed the nutritive value of oak leaves when fed together with a high quality supplement (alfalfa or sudangrass). In our experiment and related ones (Holzer et al., 1989; Vecht et al., 1989) an attempt was made to assess the feed value of oak as the sole forage source. This information can then be used to determine optimum supplementary feeding regimes for goats that graze natural scrub woodland. MATERIALS AND METHODS

The trials were carried out at the Newe Ya'ar Experiment Station located in northern Israel under typical dry Mediterranean climatic conditions. Each trial was conducted in two consecutive stages: adaptation to the new feed and

NUTRITIONAL VALUE OF OAK BROWSE AS FODDER FOR GOATS

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collection of data. The adaptation period for vetch hay was 12 days and for oak 21 days; data collection extended over 7 days for both trials. During the first stage, the digestibility of common oak browse as a sole feed was examined; in the second consecutive trial, the digestibility of vetch hay was determined. Both trials were conducted during winter (November-December 1989 ). By determining the digestibility of vetch hay, cut in the stage of early bloom, and compared to findings in the literature we were able to evaluate the methodological accuracy of our experimental system. Criticism of reliability of digestibility data (Goldman et al., 1987 ) makes this evaluation important in the quantitative determination of oak nutritional value. Five adult females (after at least two kiddings and at early pregnancy ), of the northern sub-species of Mamber goats, were employed in both trials. Average body weight was 32.00 + _ 1.50 and 36.70+-2.34 kg during the oak and hay trials, respectively. Average metabolic weight (kg t°-TS~) was 13.45 +-0.47 and 14.90 _+0.70 during the two stages, respectively. Goats were kept in metabolism cages, 1.Sx0.5X 1.0 m, designed for separate collection of faeces and urine. In the first stage, fresh mature oak browse was gathered by pruning manually twigs of up to 2 m m in diameter. The material was gathered in an area of natural scrub woodland at Mizpe Harashim in upper Galilee (32 ° 56' N, 35 °20'E, 820 m above sea level, 800 m m of annual rainfall mostly concentrated during November-March). The collected material consisted of 75% leaves and 25% twigs ( D M ) and corresponded to the parts usually selected by goats grazing oak woodland (Perevolotsky et al., 1992 ). Oak material was brought to Newe Ya'ar once every few days. Some material was fed the same day, without any pre-treatment; the rest was stored at 7 °C in sealed polyethylene bags. Goats were fed the experimental ration every day at 08 : 00 h, after removal of the food refused in the previous day. The dry matter content of the material fed was determined daily at feeding time. Care was taken to ensure that the feed would be available ad libitum. The goats had free access to water during the experiment. Residual feed was collected daily, sorted into its elements (leaves and twigs) according to material fed, weighed, and sampled for further analysis. Faecal output was measured by total collection and urine collected into concentrated hydrochloric acid. Goats were weighed at the beginning and end of the trial period. Chemical analysis of fodder, residue, faeces and urine was according to AOAC (1984). Fibrous constituents in the feed, residues and faeces were determined according to Goering and Van Soest (1970). The N content in the oak material, faeces and urine was determined according to AOAC (1984). Tannin content in samples of oak leaves was determined by protein precipitation and absorption in a spectrophotometer at 510 nm (Hagerman and Butler, 1978).

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RESULTS AND DISCUSSION

Content of oak or hay selected or rejected by the goats is presented in Table 1. Of 1600 g fresh material fed (984.8 g dry matter), 35 g dry weight of leaves and 101.8 g stems were left, totalling 136.8 g, or 13.9% of the total fed. Of the residual material, 26% was leaves and 74% stems, owing to selective eating of the goats, which preferred leaves to stems. Data on intake and various apparent digestibility coefficients are provided in Table 2. Energy and nitrogen balances of the two forage sources are in Table 3. Various studies of the nutritional value of leaves of different oak species, including digestibility coefficients, determined by in vitro and in vivo techniques, have been carried out in the last decade. Table 4 summarizes these findings. Generally, it could be concluded that in vitro analyses underestimate the digestibility of oak species from different geographical origins, both in the Old (France, Greece, Israel) and the New World (USA). Fig. 1 presents the relationship between in vitro and in vivo digestibilities, where both were measured on samples containing, exclusively, oak leaves from various species: [in vivo ] Digestibility = 30.774 + 0.513 × [in vitro ] Digestibility r2=0.784, n = 6 The equation indicates that in vitro analysis seriously underestimates low digestibilities. A line of in vivo = in vitro helps show that samples with a digestibility coefficient smaller than 60 will be underestimated by the in vitro TABLE 1

The chemical composition of common oak and vetch hay supplied, consumed and refused by black native Mamber goats (% D M ) D M (%) of fresh feed

Common oak Supplied 61.6 Remaining leaves 83.3 Remaining branches 79.9 Consumed, net Vetch hay Supplied Remaining Consumed, net ~N×6.25. *n.d. = not determined.

89.6 88.1

Ether Crude NFE Ash N D F A D F extract fibre

Cellu- Liglose nin

Tannin

6.5 6.7 5.3 6.6

4.4 2.7 3.8 4.6

25.9 23.4 23.5 26.3

57.8 60.6 57.4 57.7

17.8 14.1 18.5

4.3 4.1 4.4

27.4 21.8 28.6

38.4 35.2 39.1

CP ~

5.5 6.6 9.9 4.9

52.1 55.8 55.6 51.5

45.4 45.3 51.0 44.8

35.6 33.3 38.7 35.3

8.8 10.1 12.0 8.3

4.3 n.d.* 1.9 n.d.

12.1 48.5 24.7 45.5 9.5 49.2

41.2 46.3 40.2

28.8 33.6 27.8

11.3 10.5 11.5

n.d. n.d. n.d.

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NUTRITIONAL VALUE OF OAK BROWSE AS FODDER FOR GOATS TABLE 2 Feed i n t a k e ( m e a n s _ S D ) by goats a n d a p p a r e n t digestibility of oak browse and vetch hayt

Feed consumption Leaves, D M ( g / d a y ) DM g/kg W D M g / k g W t°'75~ D M (% o f b o d y wt. ) Apparent digestibility (%) DM OM CP C r u d e fibre

Ether extract N D F (cell w a l l ) ADF

Cellulose

Common oak

Vetch hay

847 + 57.2 b 26.5 + 1.6 b 63.05 + 3.8 b 2.6 b

1402 + 214.1a 38.2 _+4.9 a 94.0 _+ 12.4 a 3.7 a

45.37 + 1.9 b 46.10+2.0 b 32.95+_6.1 b 26.67 +_2.6 b 30.05 +_ 5.7 b 29.96_+ 2.1 b 30.11 _+3.6 b 36.18 +_4.6 b

60.07 + 1.8 a 61.04+_ 1.7 a 66.41 + 1.4 a 56.07 + 2.1 a 64.20 + 13.9 a 49.96 + 3.3 a 43.00 + 3.4 a 45.40 _+6.3 a

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