Performance of Yearling Goats Fed Alfalfa and Florigraze Rhizoma Peanut Hay

S. Gelaye, E. A. Amoah and P. Guthrie

Agricultural Research Station, Fort Valley State University, Fort Valley, GA 31030-3298

ABSTRACT

Gelaye, S., Amoah, E. A. and Guthrie, P., 1990. Performance of yearling goats fed alfalfa and florigraze rhizoma peanut hay. Small Rumin. Res. . 3: 353-361.

Two trials comparing the nutritional value of peanut ( P ) hay (Arachis giabrata Benth. ) and alfalfa (A ) (Medicago sativa L. ) hay were conducted. The first involved 45 growing goats (24 Saanen, 11 Alpine, seven Toggenburg and three Nubian ) averaging 18.3 kg body weight ( BW ). Goats had free access to feed and water throughout the 20-week study and were weighed at weekly intervals. They were offered equal amounts of A, P or AP twice daily. Goats fed P consumed approximately the same amount of dry matter (DM) but gained more BW (P<0.10) and were more efficient (P<0.10) in converting DM into gain than those fed A or AP. A balance trial with 16 wether goats (12 Saanen, three Toggenburg and one Alpine) averaging 25.6 kg resulted in higher digestible DM (P<0.05) and digestible cell wall fractions for goats fed P than A. All goats were in positive nitrogen balance, and nitrogen retained as a percentage of intake declined (P< 0.08) from 31.0% for goats fed A to 18.4% for those fed AP, with an intermediate value of 26.5% for goats fed P. In these studies, goats utilized the dry matter of P more efficiently for body weight gain.

INTRODUCTION

Alfalfa (Medicago sativa L. ) is the preferred leguminous forage for most classes of livestock. It can be fed ensiled or air dry ( Horner and Ruelke, 1980; Bouton et al., 1987) . However, most cultivars of alfalfa are not well adapted to subtropical and tropical climates. Peanut hay (Arachis giabrata Benth. ) appears to be a good substitute for alfalfa in subtropical and tropical areas because it is resistant to the insect pests and diseases which are detrimental to alfalfa (Prine et al., 1981; Bouton et al., 1987). Prine et al. (1981) have shown that peanut yields about 10.3 t/ha in subtropical areas of the southeast of the U.S.A. and has nutritional value similar to alfalfa for heifers (Romero et al., 1987). Sheep fed peanut hay digested about the same amount of the organic matter (OM) as those fed alfalfa ( Prine et al., 1981) . In dairy cows, milk yield and milk fat were similar when 20% of the corn silage was replaced with peanut haylage (Staples et al., 1987).

The nitrogen content of peanut hay is comparable to that of a good quality alfalfa. However, long term growth and nitrogen utilization trials assessing the significance of protein and other nutrients in peanut hay have not been conducted. Therefore, the objective of this experiment was to compare growth rate and nitrogen utilization by goats fed alfalfa or peanut hay.

MATERIALS AND METHODS

Growth trial

Forty-five (24 Saanen, 11 Alpine, seven Toggenburg and three Nubian ) goats averaging 18.3 kg body weight (BW ) and 4-5 months of age were randomly divided into three treatment groups with three replications of five goats per pen. Goats were housed in open-sheds with free access to water and feed throughout the 20-week study period.

Animals were offered twice daily similar amounts of alfalfa (A), peanut (P) or equal parts of the two hays in separate feeders (AP). Their position was reversed weekly for goats offered AP and refused hay was weighed weekly for all goats. Samples of A and P were taken during every feeding, weekly samples were composited and stored at room temperature.

Goats were weighed at the beginning of the trial and at weekly intervals thereafter. Feed samples were ground through a Wiley mill to pass a 2-mm screen and were analyzed for dry matter (DM), crude protein (CP) and organic matter (OM) (A.O.A.C., 1984). Feed samples were also analyzed for neutral detergent fiber (NDF), acid detergent fiber (ADF), acid detergent lignin (ADL), cellulose and hemicellulose concentrations (Goering and Van Soest, 1970). Gross energy (GE) of the feed samples was measured with a 1241 Parr adiahatic homh calorimeter.

Balance trial

After the growth trial, 16 wether goats (12 Saanen, three Toggenburg and one Alpine) with an average BW of 25.8 kg and 11-12 months of age were transferred to metal metabolism crates allowing for separate total collection of feces and urine ( Briggs and Gallup, 1949) . Goats were maintained on their previous respective forages throughout the balance trial. Goats were weighed for 2 consecutive days at the beginning and before the end of the collection period.

For this study, the forages were ground to obtain a mean particle size of approximately 4.0 cm. Animals were housed in a temperature controlled (22·C) metabolism room with constant fluorescent lighting. There was a 7 day adjustment period, a 7-day preliminary period and a 21 -day total collection of feces and urine. Goats (A, n = 6; P, n = 6 and AP, n = 4) were offered at 10.00 h a measured quantity of the forages once daily allowing 10% refusal throughout the collection period. Goats fed AP were offered a mixture of equal amounts of the two forages and all animals had free access to water. Twenty percent aliquot samples of feces and urine were composited for each goat and stored at--20 " C.

The fresh feed, refusal, urine and fecal samples were analyzed for CP and GE. Feed, refusal and fecal samples also were analyzed for DM, NDF, ADF, ADL and OM using cited procedures. Ruminal fluid samples were taken by stomach tube 4 h after feeding on the last day of collections to determine pH (electrometrically), ruminal NH3-N (Beecher and Whitter, 1970) and volatile fatty acids (VFA) (Erwin et al., 1961). The gas liquid chromatograph was a Hewlett Packard Model 5880 and the 3 m glass column was packed with 10% SP 1200/ 1 % H3PO4 on 80/ 100 Chromosorb WAW.

Blood samples were taken by jugular puncture, 4 h after feeding, for determination of plasma urea (Chaney and Marbach, 1962) and glucose with autoanalyzer (Technicon SMA, Tarrytown, NY).

Data were analyzed statistically by the GLM Procedure of SAS (1985) . In the growth trial, feed intake, rate of BW gain and final BW were adjusted using initial BW as a covariate in the model. Means were separated using LSD.

RESULTS AND DISCUSSION

Feed composition

Chemical composition of feed was similar during growth and balance trials (Table 1) . However, P contained slightly less ADF, CP, lignin and total minerals than A. The P was a thin-stemmed forage with less lignified cell walls but with 15% more hemicellulose than A. Prine et al. (1981) reported that protein in P varies with cutting seasons ranging between 15.8% in June to 19.1% in October. Romero et al. (1987) reported higher NDF values for A (56.1 % ) and P (55.6% ) than data reported in this study.

Growth trial

Daily DM intake was not influenced by type of hay (Table 2). At the termination of the study, goats fed P were heavier (P< 0.10) and rate of gain was higher (P<0.10) for those fed P than those fed A or AP. Goats fed P were more efficient (P<0.10) in converting feed DM to gain and thus required about 29% less DM per unit gain than those fed either A or AP. Goats that had free access to equal amounts of both A and P in the same pen (AP ) tended to consume more P than A (495.3 vs. 469.5 g day-'). For 9 weeks, these goats voluntarily consumed more (P<0.07) P than A and the same trend persisted throughout the remaining 11 weeks (Fig. 1). Romero et al. (1987) observed more rumen by-pass CP from P than A. The preformed pro tein could be digested post-ruminally to supply essential amino acids needed for growth.

Balance trial

Daily DM and water intakes were unaffected by forage type (Table 3). However, P and AP goats consumed 33% more (P< 0.05) hemicellulose than those fed A. Goats consumed an average of 3.0% and 8.1 % of BW in feed and water, respectively. The goats fed P and AP consumed slightly more feed and water than those offered A. Brown and Johnson (1985) reported 2.5% for goats weighing 27.0 kg but Quick and Dehority (1986) found 2.2% for goats weighing 45.5 kg while Louca et al. (1982) reported 4.4% BW for goats fed various roughages and browses. Average water consumption for the group fed P was higher than AP because of excessive amounts consumed by one goat fedP (8.1 kgday-').

Nitrogen intake and excretion in feces and urine were similar for goats fed A and P (Table 4). All goats were in positive nitrogen balance with more nitrogen retained (P< 0.08) by groups fed A and P than by AP. When the retained nitrogen was expressed as a percentage of nitrogen consumed, goats fed A retained the largest amount (P<0.08) followed by P, and the least amount for AP. For goats fed P or AP, there was a trend for more of the nitrogen consumed to be excreted in urine, resulting in a decline in the percentage nitrogen retained.

Digestibilities of DM, OM, NDF, GE and cell wall fractions were consistently higher (P< 0.05) for goats fed P than for those fed A (Table 5) . Similarly, Holstein cows digested more DM, NDF and ADF from fall P than A (Romero et al., 1987) . When goats were fed AP instead of A or P, CP digestibility was depressed (P< 0.05) by 5 percentage points.

Ruminal concentration of propionate was depressed and valerate elevated (P< 0.05) when goats were fed P instead of A or AP possibly due to differences in forage cell wall (Table 6) . However, plasma urea and glucose were unaffected by the two hays.

When goats were given free access to both forages during the growth trial, they voluntarily consumed more P than A for 9 weeks. Goats selectively consumed the less fibrous portion of a feed (Van Soest, 1982; Pfister and Malechek, 1986) and there was a negative relationship between NDF content and forage intake (Mertens, 1973). Since the amount of NDF in A and P was similar, such relationship probably did not apply in this study.

Goats fed P digested fiber and other nutrients more efficiently than those fed A. Schneider and Flatt (1975) reported a negative association between fiber content and digestibility of nutrients. High concentrations of ADF and lignin in feed depress digestibility of DM and other nutrient fractions (Mertens, l 973; Van Soest et al., 1979; Van Soest, 1982) . The P had lower concentrations of ADF, ADL and higher concentration of OM than A.

CONCLUSIONS

Peanut hay is either comparable or better in nutrient composition than a good quality alfalfa hay. It contains similar amounts of neutral detergent fiber but the fiber in peanut tends to be lower in lignin and acid detergent fiber, and higher in hemicellulose and organic matter than the fiber in alfalfa.

Goats fed peanut hay were heavier and had better feed to gain ratio than those fed the alfalfa hay. However, they absorbed and retained comparable amounts of nitrogen as those fed alfalfa hay.

More dry matter, organic matter, neutral detergent fiber, acid detergent fiber, hemicellulose, cellulose and gross energy were digested by goats fed florigraze rhizoma peanut than by those fed alfalfa hay.

These series of investigations demonstrated that peanut was a good replacement for alfalfa in the diet of goats. Goats offered peanut hay utilized more nutrients for a greater BW gain than those fed a good quality alfalfa.

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