Effect of supplementing weaner goats with graded levels of Calliandra calothyrsus and Lucerne (Medicago sativa) on feed intake and weight gain

 M N Kinuthia, M M Wanyoike, C K Gachuiri and J W Wakhungu

Universityof Nairobi, College of Agriculture and Veterinary Sciences, Department of Animal Production. P.O. Box 29053-00625 Nairobi
kinuthiamn@yahoo.com

Abstract

A study was conducted to investigate the effects of supplementation with graded levels of two (2) protein-rich forages (PRFs), Calliandra calothyrsus and Lucerne (Medicago sativa) on nutrients intake and growth rate of dual-purpose weaner goats under two management systems [confined feeding (CF) and free-range (FR)]. Sixty (60), four (4) month old weaner goats (30 for each management system) were randomly allocated to 5 treatment diets with graded levels of Calliandra calothyrsus and Lucerne in a randomized complete block design. Composition of the 5 treatment diets as fed was as follows:- T1 (control) - Rhodes grass hay only or grazing only for CF or FR respectively, T2 and T3, 100 and 200 gd^-1 of Calliandra calothyrsus respectively; T4 and T5, 100 and 200 gd^-1 of Lucerne respectively.Feed intake was recorded daily, while the weaners were weighed weekly throughout the experimental period (8 months).

The overall mean post-weaning average daily gain (post-ADG) (gd^-1) and yearling live-weight (YWT) (kg) for all the weaners were 40.9 and 17.3 respectively. Weaners under FR system performed significantly (P<0.05) better in post-ADG and YWT than those under CF. The average post-ADG (gd^-1) and YWT (kg) for the two systems were 46.8 and 19.4; and 34.9 and 15.2 respectively. Increase in level of supplementation significantly (P<0.05) increased OMI (gd^-1) for both types of supplements under CF where this was assessed from 220, for the control to 351, 579, 317 and 484 for T2 to T5 respectively. Weaners on Calliandra had significantly (P<0.05) higher post-ADG and YWT than those on Lucerne based diets and the control. For CF, the respective values for post-ADG (gd^-1) for T1 to T5 were, 17.4, 30.8, 56.8, 26.1 and 40.1. The respective values for FR were, 32.2, 46.1, 61.3, 41.1 and 50.0. The values for YWT (kg) for CF were 12.0, 14.6, 20.0, 12.8 and 16.3 for T1 to T5 respectively. For FR the respective values were 15.6, 19.6, 23.0, 17.3 and 21.4. At both levels of supplementation under both management systems weaners on Calliandra performed significantly (P<0.05) better than those on Lucerne based diets in post-ADG and YWT.

Results from this study indicated that supplementation with PRFs improved weaner growth rate under both systems and that FR was superior to Rhodes grass hay offered under the CF system and Calliandra superior to Lucerne.

Key words: dual-purpose goats, post-weaning growth, protein-rich forages, supplementation

Introduction

Goats are found in many parts of Kenya and are an important source of income to many smallholder farmers, because, due to their small size they are more easily convertible to cash than cattle (Payne 1990). They provide higher off-take than cattle because of their shorter generation interval and higher prolificacy. Annual off-take can be as high as 60 % (Payne 1990). The goat has a high twinning rate and in favourable environments, they attain a twinning rate of over 70 % by second kidding. Awemu et al (1999) reported a high twinning rate of 62 % for Red Sokoto goats, and Alexandre et al (1999) reported a figure of 59.7 % for Creole goats.

In many parts of the tropics, animal productivity including that of goats is constrained by regular feed shortages occasioned by dry seasons and droughts. During such periods animals are mainly dependent on poor quality grasses and crop by-products with little or no supplementation, leading to low animal performance (Kariuki 1998). Supplementation of low quality grass based diets with legumes has been shown to increase dry matter intake and animal performance (Kaitho 1997). These responses have typically been attributed to the legume overcoming the depressing effect that the low N concentration in grass has on intake and by the legume providing ruminally degradable N or rumen escape N (Minson 1990). Feeding systems that make greater use of locally grown feed resources such as leaves of protein-rich forages (PRFs) would provide alternatives to the more expensive cereal based concentrates (Nguyen and Preston 1997).

Calliandra calothyrsus is a leguminous shrub, high in CP content (200 - 300 g kg^-1DM) (Paterson et al 1996). It yields well (12.4 - 26.2 t DM/ha/yr) in a range of environments and is tolerant to acidic soils (Palmer and Ibrahim 1996). Supplementation with Calliandra leaf meal has been shown to improve DMI and growth in goats (Ebong 1996). However, data on Calliandra supplementation in goats in the country is scarce. Lucerne is a well-established leguminous fodder in the country and has a high CP content (160 - 210 g kg^-1DM) (Kariuki 1998; Odongo et al 1999). It is mainly grown in medium and large-scale farms and fed as hay as a dairy cattle supplement especially during the dry season. Little information is available in Kenya on the use of Lucerne in goat production. Muhikambele et al (1996) recorded improved growth in Saanen goats supplemented with Lucerne. Therefore, the objective of this study was to investigate the effect of supplementing graded levels of Calliandra calothyrsus and Lucerne to weaner goats on growth and nutrients intake under two management systems.
 

Materials and methods

Experimental site

The confined feeding trial was conducted at the Kenya Agricultural Research Institute (KARI), Naivasha, Kenya, (0.40^oS, 36.3^oE, 1900 m altitude) located about 120 km Northwest of Nairobi. The mean annual rainfall is 620 mm received mainly from March to June and October to December for the long and short rains respectively. The mean annual temperature is 23^oC with daily variations between 7 to 26^oC, with higher temperatures pertaining during the dry months. The soils are of moderate fertility and slightly to moderately alkaline (Jaetzold and Schmidt 1983).

The free-range trial was conducted at the Ol-Magogo field-station, a sub-station of KARI Naivasha. The field-station is situated on the lower Eastern slopes of the Central Rift Valley in Kenya, in a natural thorn bush land savannah. The area lies on 0.37^oS, 36.3^oE, with an altitude of approximately 1700 m and has a semi-arid climate with strong desiccating winds during the dry season. The rainfall pattern is bimodal with the long rains in March to June and the short rains in October to December. The average annual rainfall stands at about 750 mm. The maximum temperatures are between 20^oC and 30^oC with the minimum between 12^oC and 18^oC with little variations between seasons. The soils are of moderate fertility and slightly to moderately alkaline (Jaetzold and Schimdt 1983).

Feed sources

Rhodes grass and Lucerne hay were purchased from a farm next to KARI-Naivasha station. During the entire feeding trial, these were purchased in 3 large batches to minimize variation. Prior to feeding the hay was chopped using a motorized Chaff cutter set to cut at 2.5 cm length. The chopping was done to minimize wastage, ease weighing, ensure uniformity and to minimize selection by the animals.

Calliandra leaves were harvested in previously established experimental plots at Kenya Agricultural Research Institute (KARI) - Muguga farm and the neighbouring Kenya Forestry Research Institute (KEFRI). After harvesting, the branches were cut-off to stumps 1 ft above the ground. This was done to facilitate quick re-growth for the next harvest, which was every four (4) months. After harvesting, the leaves were dried for one (1) week under shade by spreading on plastic sheets on the ground, with frequent turning to prevent rotting. The dry leaves were packed in gunny bags and stored ready for feeding.

Experimental diets

Composition of the 5 experimental treatment diets (T) as fed was as follows:- T1, control; T2 and T3, 100 and 200 g goat^-1 day^-1 of Calliandra calothyrsus respectively; T4 and T5, 100 and 200 g goat^-1 day^-1 of Lucerne (Medicago sativa) respectively. T1 was Rhodes grass hay only for confined feeding, while for the free range it was grazing only. All the goats on confined feeding were offered Rhodes grass hay ad libitum as the basal diet. Grazing in a natural thorn bush land savannah provided the basal diet for those on free-range.

Feeding and housing

Kids were weaned at the age of 4 months (16 weeks) and weaning weight recorded. The mean weaning weight for confined feeding was 9.95±0.41 kg, while that for the free-range was 11.8±0.46 kg. After this, they were housed in individual wooden pens measuring 1x3 m on a wooden slated floor and randomly allocated to the 5 treatment diets in a randomized complete block design (Steel and Torrie 1996). Each treatment group comprised of six (6) goats and were balanced for sex of the goats. The feeding trial was conducted for eight (8) months up to the age of one (1) year and yearling live weight recorded. For the confined feeding trial, Rhodes grass hay was offered ad libitum as the basal diet for all the treatments. The daily offer for hay was estimated using the previous day's intake and adding a 10 % allowance (Kariuki 1998). Each morning, the previous days residues (refusals) were removed and weighed before fresh feed and water were offered. The hay was fed in troughs and the supplement in plastic buckets, the supplement was always provided first. The hay and supplements were fed twice daily, half in the morning (08.00 hours) and the other half in the afternoon (14.00 hours). The animals consumed the entire supplement on offer. Water and mineral block (Maclik^R brick) were provided ad libitum.

For the free-range trial, the animals were housed in similar facilities as those on confined feeding and the supplement was similarly fed individually (in plastic buckets) in two meals half in the morning (08.00 hours) and the other half in the afternoon (16.00 hours). After the morning feeding (08.00 - 09.00 hours), the weaners were released for grazing. They were grazed for approximately 8 hours daily in a natural thorn bush land savannah. In the afternoon (16.00 hours) they were brought back to the night enclosure where the second half of the supplement was offered. As for the confined feeding the animals consumed the entire supplement on offer. Water and mineral block (Maclik^R brick) were provided within the night enclosure. At the beginning of the experiment all the animals were sprayed with an acaricide (Triatix^R) to control ecto-parasites and dewormed with an antihelminthic (Nilzan^R) to control endo-parasites. During the experimental period they were sprayed fortnightly and dewormed after every 3 months.

Estimation of dry matter intake (DMI)

Voluntary hay dry matter intake was estimated as the difference between the amount of hay offered and that refused, on daily basis, corrected for DM content. Intake of the supplement was the amount offered corrected for DM content as there were no refusals.

Feed sampling

From each of the three batches of Rhodes grass hay and Lucerne hay, about five bales were chopped, mixed thoroughly and a sample of about 500 g taken. The samples were stored in labeled plastic bags. At the end of the experiment they were milled in a Wiley mill to pass through a 1 mm screen and stored in labeled airtight sample bottles for subsequent chemical analysis. Calliandra was similarly sampled and stored.

Data collection

The weaners were weighed weekly (at same time and day in the morning before feeding) until they were one year old and yearling live weight recorded.

Chemical analysis of feed samples

Dry matter content was determined by drying approximately 1 g of each sample in an oven at 105°C for 12 hours. Ash content was determined by ashing the DM residue (AOAC 1990). Organic matter was calculated as the difference between the dry matter and the ash. Calcium (Ca) and Phosphorus (P) were determined by standard methods (AOAC 1990), using the '2380 Atomic Absorption Spectrophotometer' and the 'CE 4400 UV Visible Double Beam Scanning Spectrophotometer' for Ca and P determination respectively. Crude protein content was determined by macrokjeldahl method according to AOAC (1990). The NDF, ADF and ADL contents were determined by sequential analysis according to Van Soest (1994). Hemicellulose and cellulose were calculated by difference. Ether extract (EE) was determined by the Soxhlet Extraction method in di-ethyl ether (AOAC 1990).

Statistical analysis

The average daily weight gain (ADG) (g/d) over the experimental period was calculated by regressing body weight (kg) of individual animal measured at weekly intervals with time (in days). Feed utilization efficiency (FE) was calculated as the ratio of body weight gain in grammes (g/d) per gram of DM intake (g/d) (Kariuki 1998). The least squares and maximum likelihood procedures of Harvey (2000) were used to determine effect of treatment on nutrients intake, post-weaning growth rate (post-ADG), yearling live weight (YWT) and FE. Also analyzed were effects of management, type of birth, sex of weaner and parity of doe on post-ADG and YWT.

Factors fitted in the fixed statistical models included:- Treatment diet, sex, type of birth, management and parity. For the purposes of data analysis these factors were coded as follows:- Treatment diet 1-5 as described above. Sex 1 and 2 for male and female respectively. Type of birth 1 and 2 for singles and twins respectively (there were no triplet births). Parity 1-5. Management system 1 and 2 for free-range and confined feeding systems respectively.

Analysis of nutrients intake and post-weaning growth

Model I:- Y_ijk = m + T_i + e_ijk (To determine effect of treatment on nutrients intake and FE.)
Model II:- Y_ijklmn = m + T_i + S_j + TB_k + P_l + M_m + e_ijklmn
[To determine effects of treatment, sex, type of birth, parity and management on post-weaning ADG and yearling live weight (YWT)]

Where,

Y_ijk = Nutrients intake (g day^-1).

Y_ijklmn = Either, post-weaning ADG (g) or YWT (kg).

m = The underlying constant common to all observations.

T_i = Effect due to i^th treatment diet (i = 1,...,5)

S_j = Effect due to j^th sex of weaner (j = 1,2).

TB_k = Effect due to k^th type of birth (k = 1,2,)

P_l = Effect due to l^th parity (l = 1,…,5)

M_m = Effect due to m^th management system (m = 1,2)

e_ijklmn = The random error term, associated with each observation.
 

Results and discussion

The chemical composition of feed ingredients is presented in Table 1. The DM content of Rhodes grass hay, Calliandra and Lucerne were 924, 925 and 905 gkg^-1 respectively. The CP contents were 77, 248 and 194 g kg^-1DM for hay, Calliandra and Lucerne respectively. The CP content of hay was higher than 43 g kg^-1DM (Woyengo 2001), but lower than 83 g kg^-1DM (Biwott 2000). However, it was within the range of 40 - 112 g kg^-1DM for tropical grasses (Van Soest 1994). The fibre content of Rhodes grass hay was higher than the legumes.

The CP content of Calliandra was within the range of 200 - 300 g kg^-1DM reported by Paterson et al (1996), while that of Lucerne was within the range of 160 - 210 g kg^-1DM (Kariuki 1998; Odongo et al 1999). The ME (MJ kg^-1DM) values estimated from the chemical composition were higher for the legumes than that of hay (9.1 MJ kg^-1DM), Calliandra (9.9) being higher than Lucerne (9.5). The levels of Calcium (Ca) and Phosphorus (P) were higher in Lucerne than Calliandra and hay and in agreement with those reported elsewhere (Kaitho 1997; Kariuki 1998). The lower NDF in Lucerne and Calliandra compared to hay was consistent with the general observation of lower NDF in legumes than grasses (Minson 1990).

The chemical composition of the treatment diets is presented in Table 2.

This was estimated based on the ratio of hay to legume in each diet as consumed using the average composition values of each ingredient. DM and OM content increased progressively with increase in the proportion of Calliandra but decreased with increased levels of Lucerne. These differences reflect the lower DM and OM content of Lucerne compared to Calliandra and hay (Table 1). The ME (MJ kg^-1DM) of the treatment diets, estimated from the in-vivo OM digestibility, was significantly (P<0.05) lower for the control diet than the supplemented diets, which were similar (P>0.05). The CP content was significantly (P<0.05) higher for the supplemented diets than the control. It ranged from 77 (T1) to 123 g kg^-1DM (T3) and increased (P<0.05) with proportion of the supplement in the diet for both supplements. Supplementation reduced NDF and ADF levels due to lower NDF and ADF levels for the legumes than hay (Table 1). ADL differed significantly (P<0.05) across the diets decreasing with Calliandra but increasing with Lucerne supplementation. T5 had the highest levels of Calcium and Phosphorus. These compositional variations of the diets reflected the differences in composition of Calliandra and Lucerne (Table 1) and level of supplementation (Table 2).

Nutrients intake and post-weaning growth

The estimated nutrients intake and post-weaning growth are presented in Tables 3 and 4, and Figures 1 and 2. The overall mean post-weaning average daily gain (Post-ADG) and yearling live-weight (YWT) obtained in this study for all the weaners were 40.9 g day^-1 and 17.3 kg respectively.

For the confined feeding system, TDMI (gd^-1 and gkg^-1W^0.75) increased with level of supplementation (Table 3), it was highest for T3 and lowest for the control.

Similar trends were observed for TOMI. Metabolizable energy intake (MEI MJ day^-1) increased with level of supplementation and differed significantly (P<0.05) across the diets. The MEI for all the diets was above the minimum requirements for maintenance of a 10 kg live-weight goat estimated at 2.3 MJ day^-1 (Peacock 1996).

The total crude protein intake (TCPI) g day^-1 increased with level of supplementation.For the confined feeding it increased from 21 g day^-1 for the control to 48, 85, 40 and 67 for T2, T3, T4 and T5 respectively and differed significantly (P<0.05) between the diets (Table 3). TCPI was affected by level and type of supplement. These differences reflected the dietary CP content of the treatment diets (Table 2). Similarly, the DCPI (estimated from the in-vivo digestibility trial), increased with level of supplementation and was above the minimum requirements for maintenance of a 10 kg live-weight goat estimated at 12 - 15 g day^-1 (NRC 1981; Furber 1985; Peacock 1996) for all the diets.

Results on performance of weaners under the free-range management system (Table 4 and Figure 2), reflected those of weaners under the confined management system and the response to level of supplementation was similar under both systems.