Supplementation of cottonseed meal on feed intake, digestibility,
live weight and carcass parameters of Sidama goats
Matiwos Solomon
a, Solomon Melaku
b,⁎
, Adugna Tolera
ca
Dilla ATVET College, P.O. Box, Dilla, Ethiopia
bDepartment of Animal Sciences, Haramaya University, P.O. Box 138, Dire Dawa, Ethiopia cDepartment of Animal and Range Sciences, Hawassa University, P.O. Box 5, Awassa, Ethiopia
Received 4 January 2008; received in revised form 15 March 2008; accepted 17 March 2008
Abstract
The experiment was conducted at Dilla Agricultural Technical Vocational Education and Training (ATVET) College in Ethiopia using twenty-four yearling intact male Sidama goats with a mean body weight (BW) of 16.8 ± 1.14 kg (mean ± SD). The objective of the experiment was to examine the effect of different levels of cottonseed meal (CSM) supplementation on the feed intake, digestibility, BW gain, and carcass parameters of Sidama goats. The experiment consisted of 90 days of feeding trial and 10 days of digestibility trial followed by evaluation of carcass parameters at the end of the experiment. The treatments includedad libitum
feeding of hay (T1, control) and daily supplementation of CSM at 200 g (T2), 300 g (T3) and 400 g (T4) per head on dry matter (DM) basis. The experimental design was a completely randomized block design. The experimental goats were blocked on initial BW and six goats were randomly assigned to each treatment. Hay DM, crude protein (CP) and neutral detergent fiber (NDF) intake were higher (Pb0.001) in the non-supplemented than in the supplemented goats, however, the contrary was true for total CP intake. Total DM intake was higher (Pb0.001) for goats supplemented with the high level of CSM than those on the control treatment. Among CSM supplemented goats, the intake of CSM DM, CP, NDF (Pb0.001) and total CP (Pb0.01) were higher in the order of T4NT3NT2. The high level of supplementation with CSM resulted in better (Pb0.05) apparent digestibility coefficient (DC) of DM and organic matter (OM) compared to the non-supplemented goats. The apparent DC of CP was higher (Pb0.01) for supplemented than non-supplemented goats. The non-supplemented goats had lower daily BW gain, empty BW, dressing percentage on slaughter weight base, rib-eye muscle area (Pb0.01), BW change (Pb0.001), final BW (Pb0.05) and higher feed conversion ratio (Pb0.01) than the supplemented ones. The medium level of supplementation resulted in higher daily BW gain (Pb0.01), BW change (Pb0.001), final BW (Pb0.05) and lower feed conversion ratio (Pb0.01) than the lower level of supplementation, but with no differences (PN0.05) in these parameters with the high level of supplementation. Therefore, it is concluded that supplementation of CSM at 300 g DM per head per day resulted in better animal performance parameters in Sidama goats.
© 2008 Elsevier B.V. All rights reserved.
Keywords:Feed intake; Digestibility; Body weight; Cottonseed meal; Sidama goats Livestock Science 119 (2008) 137–144
⁎ Corresponding author. Tel.: +251 915 74 72 18. E-mail address:solmelay@yahoo.com(S. Melaku).
www.elsevier.com/locate/livsci
1. Introduction
Goats are among the important domestic animals of value to man in the drier regions of the tropics. They have multiple functions and display a unique ability to adapt to harsh environments with wide ecological range. In the tropics, goats serve mostly as a source of meat and skins (Devendra and Burns, 1983), while in the temperate zone they are primarily reared for milk and to a lesser extent for meat production. Feeding behaviour, prolificacy, small body size are important characteristics of goats that enable them to be easily integrated in pastoralist as well as mixed crop livestock production systems in the tropics. Conse-quently, about 52% of the world's goat population is found in the developing countries of the tropics (FAO, 2003) due to their concentration in dry tropical areas of poor agricultural potential and even on marginal lands (Morand-Fehr and Boyazoglu, 1999). Indeed, mutton and goat meat as compared to beef account for a large share of the domestic meat consumption in many tropical countries (Gryseels and Anderson, 1983).
However, the meat production potential of goats is low compared to the population size. This low level of
productivity of goats in tropical countries could be attributed to animal diseases, poor genetic potential, lack of proper management, and poor nutrition, among which the latter plays a significant role. Generally, goats reared by smallholder farmers and pastoralists in the tropics rely entirely on poor quality natural grass-land, crop residues with crude protein (CP) contents of less than 8% and neutral detergent fiber (NDF) content of more than 55%. Feedstuffs of such composition hardly meet the maintenance requirements of goats throughout the year. Hence, supplementation with agro-industrial by-products such as oil seed meals that are produced abundantly in tropical countries and rich in CP (200–500 g/kg DM) is among the possible measures to improve the productivity of goats. Among the various oil seed residues, cottonseed meal (CSM) is one of the protein supplements commonly used in animal feeding, though its utilization may be limited by its content of gossypol, the main anti-nutritive factor in CSM. However, according to Wolf et al. (1980), gossypol in CSM cannot present problems to animals with a functional rumen. Therefore, this experiment was conducted with the objective to examine the effect of different levels of CSM on feed intake, weight change and carcass parameters of Sidama goats.
2. Materials and methods
2.1. Description of the experimental area
The experiment was conducted at Dilla Agricultural Technical Vocational Education and Training (ATVET) College, Ethiopia. The study site is located at 6° 27′N and 38° 30′E and at an altitude of 1550 m above sea level, and receives annual precipitation of 1200–1800 mm with annual temperature range between 13 and 23 °C.
2.2. Management of animals
Twenty-four yearling male Sidama goats with mean initial body weight (BW) of 16.78 ± 1.14 kg (mean ± SD) were used for the study. The goats were quarantined for 3 weeks, and during this period they were de-wormed and sprayed against internal and external parasites, respectively. They were also vaccinated against pasteurelosis and anthrax, and penned individually.
2.3. Experimental design and treatments
The experimental goats were blocked into six blocks of four animals based on initial BW and randomly assigned to one of the four dietary treatments in a randomized complete block design giving six animals per treatment. The dietary treatments consisted of sole grass hay (control, T1), and supplementation with 200 g (low, T2), 300 g (medium, T3) and 400 g (high, T4) CSM on DM basis. The natural grass hay used in the study consisted of mainlyDigitaria nodosa,Sporobolus natalensis andEragrostis papposa
species.
2.4. Feed intake and body weight
(FCR) was calculated as a proportion of daily DM intake to daily BW gain. The substitution rate (SR) of the basal feed by the concentrate mix was calculated using the following equation (Ponnampalam et al., 2004).
SR¼Tef straw intake of control treatment gð Þ tef straw intake of the supplemented treatment gð Þ
Concentrate mix intake gð Þ
Initial BW of each goat was determined by taking the mean of two consecutive weights after overnight fasting, and BW was subsequently measured every 10 days after overnight fasting. The mean daily BW gain was calculated by regressing BW measurements on days of feeding.
2.5. Digestibility trial
Four animals from each treatment were randomly selected and fitted with faeces collection bags to measure the digestibility of the treatment feeds they were fed on during the feeding trial. After allowing an adjustment period of 3 days to carrying the faeces collection bags, daily total faecal excretion per animal was collected for seven consecutive days. The daily collected faeces was weighed, 20% sub-sampled and stored frozen at−20 °C. The digestion coefficient of nutrients was calculated as a proportion of
nutrients consumed and not recovered in the faeces.
The digestibility of CSM was estimated by difference as described byMcDonald et al. (2002)using the equation:
Nutrient DC¼Nutrient in test f eed ðNut:in f aeces of mixed diet Nutrient in f aeces of basal f eedÞ
Nutrient in test f eed
2.6. Carcass parameters
Five goats from each treatment were randomly slaughtered after overnight fasting. Blood, head, skin, feet, heart, lungs and trachea, liver with gall bladder, spleen, testis, penis, kidneys, abdominal gut, reticulo-rumen, omasum–abomasum, small and large intestine were weighed and recorded. Empty BW was determined by difference between BW at slaughter and gut content. Hot carcass weight was computed by excluding edible and non-edible offals. Dressing percent was calculated as proportion of hot carcass weight to slaughter as well as empty BW. The rib-eye muscle area was measured by tracing the cross section area of the 10th and 11th ribs after cutting perpendicular to the back bone (Kyomo, 1978cited inLegesse, 2001). The left and right rib-eye muscle area was traced on a water proof transparent plastic foil and the area was measured using a planimeter.
2.7. Chemical analysis
Samples of feed offered, refused and faeces were dried at 55°C in a forced draft oven to constant weight and ground to pass 1 mm mesh screen size and used for determination of chemical composition. Dry matter (DM), organic matter (OM), CP, ether extracts (EE) and ash were analysed according to theAOAC (1990). The NDF, acid detergent fiber (ADF), and acid detergent lignin (ADL) were analysed by the procedures ofVan Soest et al. (1991).
2.8. Statistical analysis
The data collected were subjected to the analysis of variance using the general linear model procedure ofSAS (1998). Treatment means were separated by least significant difference (LSD). The model used for feeding trial wasYij=μ+Ti+Bj+eij,while the model
used for the digestion trial and carcass parameters wasYij=μ+Ti+eij.
Where;Yijis response variable,μoverall mean,Tiis treatment effect,Bjis block effect, andeijis random error.
3. Results
3.1. Chemical composition of the treatment feeds
The CP content of hay used in this study was markedly lower than CP contained in CSM, whereas the NDF and ADF contents were higher in the grass hay (Table 1). The CSM contained more ADL than the grass hay.
3.2. Feed intake
while the total DM intake increased. There was no significant difference (PN0.001) in total DM intake among supplemented goats. The total CP intake increased (Pb0.01) with increasing level of supple-mentation. The daily DM, CP and NDF intakes of CSM increased (Pb0.001) with level of supplementation. Treatment differences (PN0.05) were not observed in NDF and ADF intake as well as in total DMI as percent of BW. Supplementation with CSM caused a partial substitution of the grass hay with the CSM, which was
higher (Pb0.05) at the highest than the lowest level of supplementation.
3.3. Apparent digestibility of nutrients
The apparent digestibility of CP in supplemented goats was higher (Pb0.01) as compared to that in non-supplemented goats, even though there was no differ-ence (PN0.01) among the supplemented treatments
(Table 3). The high level of supplementation resulted in higher (Pb0.01) apparent OM digestibility compared to the control treatment. Moreover, the high level of supplementation promoted higher (Pb0.05) apparent digestibility of DM as compared to the control and the low level of supplementation. Organic matter, CP and NDF digestibility increased numerically with level of CSM supplementation, though statistically non signifi-cant (PN0.05). The apparent digestibility of NDF and Table 2
Daily feed intake of Sidama goats fed grass hay supplemented with different levels of cottonseed meal Total NDF intake 45.9 46.3 46.0 48.0 1.48 ns ADF intake 25.1 27.0 27.5 29.1 0.81 ns Total DM intake
abcdMeans in the same row with different superscripts differ sig-nificantly (Pb0.05);*** (Pb0.01); ** (Pb0.01); * (Pb0.05); ADF = acid detergent fiber; BW = body weight; CP = crude protein; CSM = cottonseed meal; DM = dry matter; NDF = neutral detergent fiber; ns = not significant; SEM = standard error of mean; SL = significance level; T1 = sole grass hay; T2 = grass hay + 200 g DM CSM; T3 = grass
ADF = acid detergent fiber; ADL = acid detergent lignin; CP = crude protein; CSM = cottonseed meal; DM = dry matter; EE = ether extract; NDF = neutral detergent fiber; OM = organic matter.
Table 3
Nutrient digestion coefficient in Sidama goats fed grass hay supplemented with different levels of cottonseed meal
Treatments Digestion coefficient
SEM 0.022 0.012 0.022 0.06 0.020
SL * ** ** ns ns
ab
Means with different superscripts in column are significantly dif-ferent; *** (Pb0.001); ** (Pb0.01); * (Pb0.05); ADF = acid deter-gent fiber; CP = crude protein; DM = dry matter; NDF = neutral detergent fiber; ns = not significant; OM = organic matter; SEM = standard error mean; SL = significance level; T1 = sole grass hay; T2 = grass hay + 200 g DM CSM; T3 = grass hay + 300 g DM CSM; T4 = grass hay + 400 g DM CSM.
Table 4
Nutrient digestion coefficient determined by difference for different levels of cottonseed meal in Sidama goats fed hay basal diet
Treatments Digestion coefficient
DM OM CP NDF ADF
T2 0.77 0.75 0.75 0.69 0.54
T3 0.75 0.75 0.78 0.70 0.55
T4 0.82 0.83 0.82 0.78 0.67
SEM 0.33 0.27 0.18 0.37 0.38
SL ns ns ns ns ns
ADF were not different (PN0.05) between the control and supplemented goats and among different levels of supplementation. The apparent digestibility of nutrients in CSM was similar (PN0.05) for the different levels of CSM supplementation (Table 4).
3.4. Body weight parameters
The final BW, total BW change and daily BW gain were higher (Pb0.01) at medium than at low level of
supplementation and all these variables were lower (Pb0.01) in the non-supplemented than in the
supple-mented animals (Table 5). The BW of the experimental goats in all the treatments increased through time with more prominent increase in animals supplemented with the medium and high level of CSM supplementation. The grass hay used in this study also promoted positive daily BW gain. On the other hand, the feed FCR was
higher (Pb0.01) in the non-supplemented than the supplemented animals.
3.5. Carcass components and offals
The medium and high level of supplementation re-sulted in higher BW at slaughter, empty BW (Pb0.01) and hot carcass weight than the control treatment. More-over, supplementation with the different levels of CSM promoted higher dressing percent on BW at slaughter basis (Pb0.01) and higher rib-eye muscle area (Pb
0.001) compared to non-supplemented animals (Table 6). In the current study, small intestine and large intestine, reticulo-rumen, lungs and trachea and penis were not affected by different levels of supplementation Table 5
Body weight parameters of Sidama goats fed grass hay supplemented with different levels of cottonseed meal
Parameters T1 T2 T3 T4 SEM SL
Initial BW (kg) 16.0 16.6 17.3 17.2 0.54 ns Final BW (kg) 16.9c 20.3b 23.2a 22.2ab 0.65 * BW change (kg) 0.9c 3.8b 5.9a 5.0ab 0.27 *** Daily BWG 10.2c 41.7b 65.3a 55.6ab 3.10 ** FCR (g DMI/g BWG) 47.9a 13.7b 9.7b 12.3b 1.62 **
abcMeans with different superscripts in the same row are significantly different (Pb0.05);*** (Pb0.001); ** (Pb0.01); * (Pb0.05); BWG = body weight gain; DMI = dry matter intake; FCR = feed conversion ratio; ns = not significant; SEM = standard error of mean; T1 = sole grass hay; T2 = grass hay + 200 g DM CSM; T3 = grass hay + 300 g DM CSM; T4 = grass hay + 400 g DM CSM.
Table 6
Carcass parameters of Sidama goats fed grass hay supplemented with different levels of cottonseed meal
Parameters T1 T2 T3 T4 SEM SL
BW at slaughter (kg) 16.7b 20.0ab 23.0a 21.5a 0.92 ** Empty BW (kg) 12.0b 16.6ab 19.1a 17.8a 0.79 ** HCW (kg) 6.2b 9.2ab 10.6a 9.7a 0.54 ***
Dressing percentage
BW at slaughter basis 37.2b 45.8a 45.9a 45.1a 1.17 ** Empty BW basis 51.6 55 55.2 54.5 1.35 ns Rib-eye area (cm2) 3.5b 5.1a 5.6a 5.4a 0.21 ***
abMeans with different superscripts in rows are significantly different (Pb0.05);*** (Pb0.001); ** (Pb0.01); BW = body weight; HCW = hot carcass weight; ns = not significant; SEM = standard error of mean; SL = significance level; T1 = sole grass hay; T2 = grass hay + 200 g DM CSM; T3 = grass hay + 300 g DM CSM; T4 = grass hay + 400 g DM CSM.
Table 7
Edible carcass offals of Sidama goats fed grass hay supplemented with different levels of cottonseed meal Reticulo-rumen 428 405 459 369 24.58 ns Omasum–
abomasum
123b 129ab 155a 119b 5.37 **
Small and large intestine
491 598 567 561 37.74 ns
Tail 23b 34ab 39a 33ab 2.85 *
Abdominal fat 108c 343b 662a 450b 30.56 *** Testis 128b 169ab 194a 186a 10.35 ** Blood 867b 986ab 1061a 979ab 40.82 * Total edible offals 7312b 9866a 10925a 10371a 421.63 **
abcMeans with different superscripts in rows are significantly different (Pb0.05); *** (Pb0.001); **Pb0.01); * (Pb0.05); ns = not sig-nificant; SEM = standard error of mean; SL = significance level; T1 = sole grass hay; T2 = grass hay + 200 g DM CSM; T3 = grass hay + 300 g DM CSM; T4 = grass hay + 400 g DM CSM.
Table 8
Non-edible carcass offals of Sidama goats fed grass hay supplemented with different levels of cottonseed meal
Non-edible offals (g) T1 T2 T3 T4 SEM SL
Skin with feet 1590b 2400a 2560a 2580a 155.8 ** Lungs and trachea 186 201 231 207 11.7 ns
Spleen 20b 33ab 36a 31ab 3.45 *
Penis 31 34 35 40 3.34 ns
Total non-edible offals 1828b 2668a 2863a 2859a 162.0 **
(Tables 7 and 8). Heart, head, omasum–abomasum, tail, abdominal fat and spleen weight were higher (Pb0.05) in goats supplemented with the medium level of CSM compared to the non-supplemented goats (Tables 7 and 8). Medium and high level of supplementation resulted in higher (Pb0.05) liver and kidney weight than in the control goats. Generally, supplemented goats produced higher (Pb0.01) total edible offals and total non-edible offals (Pb0.05) than the non-supplemented ones.
4. Discussion
4.1. Chemical composition of the treatment feeds
The CP content of CSM used in the present study was comparable to the CP content of CSM reported by
McDonald et al. (2002) which was 239 g kg−1 DM. Contrary to the result of the current study, high CP content of 480 g kg−1DM was reported for CSM by Khan et al. (2000). The low CP content of CSM in the present study could be due to using undecorticated cottonseed for oil extraction. According to McDonald et al. (2002), undecorticated CSM contains lower CP (239 g kg−1DM) than CSM produced from decorticated meal (460 g kg−1DM). The NDF and ADF content of CSM in this study were comparable to the result of
Moges (1992). High NDF and ADF in the CSM used in the current study are related to its lower CP content. Indeed, Moges (1992) reported low CP content in oil seed cakes with high cell wall contents. The CP content of grass hay used in the present study (92 g kg−1DM) is comparable to the CP content (110 g kg−1DM) of good quality grass hay (McDonald et al., 2002). The relatively high CP content of hay in the present study is due to the species composition as well as harvesting at early stage of growth.
4.2. Feed intake
The DM intake as percent of BW in the present study (2.71–2.94%) is in agreement with that reported (1.7–
4.8% BW) for various breeds of goats in the tropics (Devendra and Burns, 1983). The high NDF and ADF intake in the non-supplemented than the supplemented goats could be due to high intake of grass hay in the non-supplemented goats since NDF content was higher in the grass hay. The higher total DM intake with the high level of CSM supplementation in this study was similar to the result of Bonsi et al. (1996) in which sup-plementation with a protein source increased total DM intake in sheep. Consistent with the result in this study,
DM intake and growth rate in Alpine and Nubian goats increased correspondingly as the level of protein in the diet increased (Lu and Potchoiba, 1990). The reduction in hay intake with increasing level of the supplement in the present study could be due to the substitution effect of the basal diet with the concentrate feed. Other studies (Mosi and Butterworth, 1985; Tolera and Sundstøl, 2000) also reported partial substitution of the basal ration by forage legume supplementation.
4.3. Apparent digestibility
The apparent digestibility of CP observed in this study agrees with the result of Ash and Norton (1987)
that demonstrated better CP digestibility in goats fed high protein compared to low protein diet. Generally, concentrate feed which is rich in protein content promotes high rumen microbial population (McDonald et al., 2002) which facilitates rumen fermentation. Similar to the current study, supplementation with CSM, leucaena or sesbania to Menz sheep did not affect the apparent digestibility of NDF and ADF (Bonsi et al., 1996). The lack of significant difference in digestibility (PN0.05) of NDF and ADF between the treatments in the present study was also in agreement to the result ofMcRae and Armstrong (1969)who reported little or no effect of supplementation on digestibility of NDF and ADF. The absence of effect of supplementa-tion on NDF and ADF digestibility could be explained by possible reduction in rumen pH which has a de-pressing effect on the population of cell wall fermenting rumen microbes as a result of feeding more digestible supplement to the animals. Increased CP digestibility in supplemented treatments might be due to higher dietary CP supply. Crude protein digestibility of CSM in the present study was comparable to the value of 77–86% reported byMcDonald et al. (2002).
4.4. Body weight parameters
supplemented goats could be due to high energy and protein intake. The daily BW gain observed in the present study was comparable to 36–53 g day−1 BW gain in Somali goats fed grass hay supplemented with concentrate mix of 200 g DM day−1(Urge et al., 2004).
Shapiro et al. (1985)reported mean daily BW gain of 33 and 70 g during the dry and wet seasons, respectively in grazing sheep supplemented with 300 g wheat bran and 300 g CSM, which is comparable to the results of the present study. The decreased FCR with the high level of supplementation in this study was in agreement to the results ofZinn et al. (1997)that showed decreased FCR with increasing level of CSM in cattle.
4.5. Carcass component and offals
The positive effect of supplementation on hot car-cass, empty BW, dressing percentage (slaughter basis) and rib-eye muscle area in the present study was similar to that reported byOkello and Obwolo (1994)in goats supplemented with CSM and maize bran. Low dressing percentage (slaughter weight basis) in the non-supple-mented goats could be due to high gut fill which accordingly reduced the dressing percentage. Slaughter weight, hot carcass weight, empty BW and dressing percentage observed for the non-supplemented goats in the present study was in agreement with the results reported byLegesse (2001)for mid-rift valley goats in Ethiopia. The average slaughter weight, empty BW and hot carcass weight of goats supplemented with 300 g DM CSM showed heavier weight which was similar to the trend observed in final BW. Consistent to the present study,Bhuyan et al. (1996)observed that low and high protein supplementation had no effect on the rib-eye muscle area in goats.Zinn et al. (1997)also reported that different levels of CSM supplementation to cattle did not affect dressing percentage and rib-eye muscle area. The lack of significant difference in dressing percentage on empty BW basis might be due to the exclusion of the contribution of gut fill. The dressing percent observed in this study was within the range of dressing percent (37–
55%) for goat carcass (Enseminger, 2002). Similar to the present study,Legesse (2001)reported that most of the non-carcass components of supplemented treatments showed significant difference for extensively managed goats.
5. Conclusions
The medium level of supplementation resulted in higher daily BW gain (Pb0.01), BW change (Pb0.001), final BW (Pb0.05) and lower feed conversion ratio
(Pb0.01) than the lower level of supplementation, but with no differences in these parameters with the high level of supplementation. Therefore, it is concluded that supplementation of CSM at 300 g DM per day resulted in better animal performance parameters in Sidama goats.
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