Trop Anim Health Prod DOI 10.1007/s11250-017-1250-7
REGULAR ARTICLES
Effects of different dietary inclusion levels of macadamia oil cake on growth performance and carcass characteristics in South African mutton merino lambs Owoahene Acheampong-Boateng 1 & Archibold G. Bakare 1 & Douglas B. Nkosi 2 & Khanyisile R. Mbatha 1
Received: 21 July 2016 / Accepted: 30 January 2017 # Springer Science+Business Media Dordrecht 2017
Abstract Growth performance and carcass characteristics of South African mutton merino fed graded levels of macadamia oil cake were assessed. A total of 60 South African mutton merino lambs were used in the experiment (initial live weight 25.0 ± 0.45 kg). Five diets with different inclusion levels of macadamia oil cake (MOC) were formulated: T1 (0% MOC, control), T2 (5% MOC), T3 (10% MOC), T4 (15% MOC) and T5 (20% MOC). Effects of inclusion level of MOC on average daily gain (ADG) and average daily feed intake (ADFI) were not significant (P > 0.05). Effects of inclusion levels of MOC on feed conversion ratio (FCR) of sheep were significant (P < 0.05). Highest proportion (71.2%) of sheep in the study had a carcass fat classification of 2, followed by a proportion of 17.3% sheep with a carcass fat classification of 3 and lastly 11.5% sheep had carcass fat classification of 4. Warm and cold carcass mass, chest circumference, carcass length and dressing percentage were higher in sheep fed on 5% MOC compared to other treatment diets (0, 10, 15 and 20% MOC) (P < 0.05). Fat rib eye had a greater area in sheep fed on 5% MOC (P < 0.05). It was concluded that 5% MOC provided the best results in terms of carcass characteristic measurements in sheep.
* Khanyisile R. Mbatha
[email protected] 1
Department of Agriculture and Animal Health, University of South Africa, Private Bag X6, Florida 1710, South Africa
2
Agricultural Research Council, API, Private Bag X2, Irene, Pretoria, South Africa
Keywords Non-conventional protein source . Feed intake . Weight gain . Carcass yield
Introduction Feed shortages and cost are the most important obstacles facing animal production in South Africa. In pursuit of sustainable and economically viable livestock systems, many farmers worldwide are under increasing pressure to maximize the use of available agro-industrial by products as feed for their livestock. Protein source in livestock feeds has been considered to be the limiting factor, especially under resource poor farming conditions. Oil cakes (e.g. Soybean and Sunflower) and urea are protein sources mostly used in animal feeding in South Africa. The purchase of these protein sources is, however, expensive, and their supply is diminishing because of the persistent droughts. In addition, the use of protein sources of animal origin in animal diets has been banned (Fertilizer, Farm Feeds, Agricultural Remedies and Stock Remedies Act No. 36 of 1947) and has raised interest in finding alternative protein sources for feeding livestock. Thus, non-traditional oil seeds available in South Africa can also be used as substitutes for conventional protein sources. Macadamia oil cake is one of such sources and is obtained from the extraction of oil from macadamia nuts at Royal Macadamia, Limpopo, South Africa. According to Skenjana et al. (2002), MOC contains 24.5% crude protein and a subsequent study (Skenjana et al. 2006) confirmed that MOC could be used as ingredients in diets of ruminants. Moreover, the study of AcheampongBoateng et al. (2008) confirmed that up to 20% MOC can be added into diet of beef cattle without adverse impacts on animal performance. It is important to establish the effects of dietary inclusion of MOC on sheep, which also play a vital role in the economy of South Africa. The objective of the
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study was, therefore, to determine the effect of different dietary inclusion levels of MOC on the growth performance and carcass characteristics of growing lambs.
Materials and methods Sheep and housing and experimental design The study was conducted at Agricultural Research Council, Irene; Pretoria. The station is situated at longitude 29° 13′ S: latitude 25° 55′ E, altitude 1524 m. A total of 60 South African mutton merino lambs were used in the experiment. Upon arrival, lambs were ear tagged and treated against external and internal parasites and bacterial infections. Initial live weight before the start of the experiment for the lambs was 25.0 ± 0.45 kg. The lambs were blocked by weight into five equal groups, and there were 12 lambs per group. Each group was allocated to each diet randomly using random number tables. All lambs were clinically healthy before the start of the experiment. Table 1 Composition of experimental diets
Feed ingredient
Diets and feeding Macadamia oil cake (MOC) was collected from Royal Macadamia (Levubu, Limpopo Province, South Africa) and brought to the ARC-Irene Institute, South Africa for chemical analyses, feed formulation and animal feeding trials. Five diets with different inclusion levels of MOC were formulated (Table 1). The diets were T1 (0% MOC, control), T2 (5% MOC), T3 (10% MOC), T4 (15% MOC) and T5 (20% MOC). The diets were formulated according to the NRC (1985) recommendations for lambs on an iso-nitrogenous basis (14% CP) to contain 11–12 MJ/kg DM calculated metabolizable energy (ME) level. Feed and water were provided on an ad libitum basis. A 21-day adaptation period was offered and feeding trial lasted for 77 days. Chemical analyses After drying, the samples were ground to pass through a 2-mm screen (Wiley mill, Standard Model 3, Arthur H. Thomas Co., Philadelphea, PA) for chemical analysis. The chemical
Treatment 1
Treatment 2
Treatment 3
Treatment 4
Treatment 5
(0% MOC)
(5% MOC)
(10% MOC)
15% MOC
20% MOC
Soyabean 48 Eragrostis hay Lucerne hay
5.00 10.00 5.00
0.00 10.00 10.00
0.00 12.60 10.00
0.00 13.00 12.00
0.00 15.00 12.90
Hominy chop Maize meal (white grade 2) Wheat bran Vitamin mineral premix Limestone
32.70 25.00 10.00 0.20 0.70
32.40 20.00 10.00 0.20 0.70
30.00 15.00 10.00 0.20 0.70
25.00 12.80 10.00 0.20 0.70
20.00 10.00 10.00 0.20 0.70
Salt
0.50
0.50
0.50
0.50
0.50
Urea Molasses meal Ammonium sulphate Macadamia (%) Nutrient density of diets Crude protein (%) Crude fibre (%) Estimated NDF g/kg Estimated ADF g/kg Estimated ME (kg/MJ) Fat (%) Ca P Na K Mg
0.50 10.00 0.40 0.00
0.80 10.00 0.40 5.00
0.65 10.00 0.40 10.00
0.45 10.00 0.40 15.00
10.00 0.40 20.00
13.88 11.30 285.75 116.93 11.39 5.24 0.61 0.39 0.29 1.06 0.05
13.85 13.92 325.72 143.13 11.85 5.69 0.69 0.38 0.29 1.06 0.04
13.86 16.14 359.58 165.33 11.84 5.92 0.70 0.39 0.29 1.10 0.03
13.82 17.93 386.88 183.23 11.86 6.01 0.74 0.38 0.26 1.12 0.03
13.86 20.04 419.07 204.33 11.84 6.07 0.75 0.37 0.28 1.14 0.02
0.30
MOC macadamia oil cake, NDF neutral detergent fibre, ADF acid detergent fibre, ME metabolisable energy
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composition of diets is shown in Table 1. Ash (method 942.05), dry matter (DM) (method 2001.12), crude protein (CP) (method 990.03) and crude fibre (CF) (method 2001.12) were determined according to the procedures of AOAC (2005). The ME was determined by using the gas production techniques of Pienaar (1994). Neutral detergent fibre (NDF) and acid detergent fibre (ADF) were estimated according to formulas described by Vervuert et al. (2010) and Agricultural Service Laboratory (1996), respectively.
Data collection Voluntary feed intake (VFI), live weight gain (LWG) and feed conversion ratio (FCR) of South African mutton merino lambs fed on MOC-based diets were measured. The initial weight of the lambs was taken on the first day using a digital scale and recorded. The lambs were weighed weekly and weight (live weight gain) recorded on the record sheet till the day of slaughter. Known weights of feed were offered to the lambs, and refusals were weighed daily for determination of feed intake. After the feeding trial, all animals were sacrificed following the regulations of the Animal Ethics Committee of the APIIrene, South Africa. The head, skin, limbs, viscera, reproductive organs, as well as lungs and trachea were separated and warm carcass was recorded. Warm carcass mass was recorded within 30 min of slaughter, and cold carcass weight was determined after chilling in refrigerator for 24 h at 4 °C. Dressing percentage was calculated as weight expressed as percentage of the live weight of the animal according to the following formula as used by Warriss (2000). Dressing percentageð%Þ ¼
Carcass weight 100 Live body weight
Carcass length was measured as the distance along the anterior edge of the spinous process on the first thoracic vertebra to the posterior edge of the pin bon (Tuber ischii). Following a visual assessment of carcass fat content and fat distribution by a trained official, carcasses were assigned to one of seven fat classes (National Department of Agriculture 1990).
Statistical analyses The variables of interest were analysed by analysis of variance for a randomized complete block design (SAS 2008) and significance was declared at 5% probability level. The PROC FREQ (SAS 2008) was used to generate frequencies on sheep in different carcass fat classes.
Results Weights of the sheep increased in the first week, remained constant for 2 weeks and thereafter started to increase steadily to the end of the trial for all the treatment diets (Fig. 1). Table 2 shows the effects of inclusion level of MOC on ADG, ADFI and FCR of lambs. Effects of inclusion level of MOC on ADG and ADFI were not significant (P > 0.05). Effects of inclusion levels of MOC on FCR of sheep were significant (P < 0.05). Lambs fed on 10% MOC had a significantly lower FCR when compared to lambs fed on 0, 15 and 20% MOC, but same low FCR when compared to lambs fed on 5% MOC. Most sheep across all treatment diets fell in class 2 of carcass fat classification (Fig. 2). The highest proportion of 80% of the sheep feeding on 10% MOC fell in fat carcass class of 2 whilst remaining 20% fell in class 3. No sheep fell in class 4. For sheep feeding on diet with 5% MOC, 66.7% of the sheep fell in class 2 whilst the remaining 33.3% sheep were in class 3. Greater proportion of sheep feeding on diets with 15% and 20% MOC fell in class 4 compared to fat carcass class 3. Overall, highest proportion of sheep had a carcass fat classification of 2, followed by a proportion of 17.3% sheep with a carcass fat classification of 3, and lastly 11.5% sheep had carcass fat classification of 4. Warm and cold carcass mass, chest circumference, carcass length and dressing percentage were higher in sheep fed on 5% MOC compared to other treatment diets (0, 10, 15 and 20% MOC) (P < 0.05; Table 3). Fat rib eye had a greater area in sheep fed on 5% MOC and less area in sheep fed on 15% MOC (P < 0.05; Table 3).
Discussion Inclusion of MOC increased acid detergent fibre (ADF), neutral detergent fibre (NDF) and crude fibre (CF) content in diets of lambs in the study. It was expected that high fibre content in diets reduce ADFI at higher MOC inclusion level. This is mainly because physical fill is the predominant factor in the regulation of intake when sheep are fed high fibrous diets. This was not the case in the study. It is highly likely that protein content (CP) in the diet might have influenced ADFI in the study. Diets in the study were iso-nitrogenous; hence, this might have accounted for similarities obtained on ADFI. The observation that feed intake in growing lambs changes as its size increases was expected. Pittroff and Kothmann (2001) reviewed intake models to be directly proportional to body weight. The correlation between intake and weight gain in the study was however not analysed. Although there were no differences in ADG of lamb across treatment, the results concerned agree with the predicted averages of the NRC (2007). Similarities in ADFI and ADG across all treatments are an indication that increasing inclusion level of MOC did
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Fig. 1 Weekly weights of sheep fed on diets containing graded levels of Macadamia oil cake (MOC)
40
Weight (kg)
35
30 0% MOC 5% MOC 25
10% MOC 15% MOC 20% MOC
20
0
1
2
3
4
5
6
7
8
9
10
11
Week
not affect nutrient intakes. Intake of nutrients in the study were not determine, hence warrants further investigations. The results are consistent with results obtained by Obeidat et al. (2011) were sheep were fed graded levels of carob pods (Ceratonia silique L.). In the study, no carcasses were frequently excessively lean (class 0 and 1), which may have a negative effect on commercial value. The observation that most of the lambs fell in carcass fat classification of 2 was expected. It can be due to the fact that the lambs were growing; hence most of the energy in the feed was channelled towards growth, that is, the building up of muscle tissues (Bathaei and Leroy 1996; McPhee et al. 2008; Wood et al. 2008). If there is excess energy, it can be deposited as fat. Difference in carcass fat classifications can also be attributed to differences in precocity or maturation of
Table 2 Effects of inclusion levels of macadamia oil cake (MOC) on average feed intake (ADFI), average daily gain (ADG) and feed conversion ratio (FCR) (mean ± standard error)
Performance parameters
ADFI (kg) ADG (kg) FCR a, b
individual animals (McPhee et al. 2008). The grades scored in the study represent leaner carcasses which are in big demand in South Africa due to their health benefits. We can affirm that the efficiency in the transformation of the feed consumed into body weight and carcass weight was similar, because there was not much reduction in carcass yield in relation to body weight in lambs across treatments. Gut contents and other non-carcass components probably contributed to differences in dressing percentages across treatment diets (Shija et al. 2013). In the study, as inclusion level of fibre increased, fibre content of diet increased as well. Lambs fed on high fibrous diets loose gut fill more slowly that lamb on low fibre diets. This partly explains the low dressing percentages at higher MOC inclusion levels. Typical dressing percentages of tropical sheep breeds fall within the range of 40
Inclusion level (g/kg) 0
50
100
150
200
1.54 ± 0.097a 0.22 ± 0.012a 6.97 ± 0.380a
1.54 ± 0.061a 0.24 ± 0.018a 6.48 ± 0.321ab
1.39 ± 0.108a 0.24 ± 0.014a 5.97 ± 0.492b
1.51 ± 0.065a 0.22 ± 0.015a 6.92 ± 0.297a
1.59 ± 0.063a 0.23 ± 0.015a 7.24 ± 0.507a
Means within the same row sharing the same superscript are not significant (P > 0.05)
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Fig. 2 Fat carcass classification of sheep fed on diets containing graded levels of macadamia oil cake (MOC)
Class2 80
80
Proporon of sheep (%)
70
66.7
Class3 72.7
70
66.7
Class4
71.2
60 50 40
33.3
30 20
16.7
10 0
20
20
18.2
16.7
0
5
10
10
9.1
15
20
17.3 11.5
Total
Inclusion levels of MOC (%)
to 48% (Cloete et al. 2004a; Shija et al. 2013). In this study, the values obtained for sheep fed on varying inclusion levels of MOC are in the same range. Rib eye area is a measurement that reflects the amount of carcass muscle. It is positively correlated with muscularity of a carcass. Balci and Karakas (2007) found rib eye area of between 10 and 12 cm2 of Karayaka lambs slaughtered at different ages and fed concentrates. Cloete et al. (2004b) observed rib eye area of between 8 and 10 cm2 in Merino sheep descended from two lines that were divergently selected for maternal multiple rearing ability. Perlo et al. (2008) observed rib eye area of 6.5 cm2 in sheep relying on grass pasture, 11.9 cm2 in sheep fed on ground alfalfa and 8.7 cm2 in sheep fed on alfalfa-linseed pellet. Low values obtained for rib eye Table 3 Carcass characteristics of sheep fed diets with five levels of Macadamia oil cake (MOC) Carcass characteristics
Warm carcass mass (kg) Cold carcass mass (kg) Dressing percentage (%) Chest Circumference (cm) Carcass length (cm) Fat rib eye (cm2)
Inclusion levels (g/kg)
SE
0
50
100
150
200
19.6b 19.1b 48.3b 62.1b 63.8a 6.9b
21.1a 20.6a 49.2a 65.2a 64.2a 7.4a
19.4b 18.9b 48.7a, b 62.3b 62.9b 6.1d
19.1b 18.6b 47.4c 62.3b 62.4b 5.6e
19.9b 19.4b 47.2c 62.6b 62.6b 6.4c
0.42 0.42 0.38 0.64 0.35 0.04
muscle area may be attributed to age of slaughter, breed and type of supplement offered to sheep. Tellam et al. (2012) further describes genes to contribute to genetic muscling in sheep. These genes have been confirmed in independent sheep populations. According to Pereira Filho et al. (2008), animals of similar weight imply similar carcass weight, chest circumference and rib eye area.
Conclusion Feeding graded levels of MOC as opposed to control diet had no effect on ADFI and ADG. However, substituting MOC had an effect on sheep carcass characteristics. It may be concluded from results of this study that MOC can be used in sheep feeding without causing any adverse effects on performance of the animals. Inclusion of 5% MOC in diet of sheep provided the best results in terms of carcass characteristic measurements. Nevertheless, more sheep should be used per treatment to increase the degree of precision on the growth performance parameters in a feeding trial.
Acknowledgements The authors extend their profound gratitude to ARC-API (Irene) for their outstanding contribution.
Compliance with ethical standards SE standard error a b
Means within the same row sharing the same superscript are not significant (P > 0.05)
Conflict of interest The authors declare that they have no conflict of interest.
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