Livestock Research for Rural Development 14 (6) 2002

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Feedlot performance of various breed groups of cattle fed low to high levels of roughage

D Norris*, J Macala, J Makore and B Mosimanyana

Department of Agriculture Research, Private bag 0033, Gaborone, Botswana
*School of Agricultural & Environmental Sciences
Private Bag X1106, Sovenga, South Africa.
norrisd@unin.unorth.ac.za

Abstract

Beef production in Botswana relies mainly on the range using local and foreign breeds as either pure breeds or for crossbreeding. The foreign breeds and their crosses are large and do not usually finish well on the range. Supplementation has not been used extensively in Botswana due to high cost of imported feeds. This study investigated the use of locally available agricultural by-products for feedlot finishing of young crossbred males commonly used in Botswana. The low, medium and high roughage diets were balanced for crude protein and mineral content but differed in digestible energy.

Animals fed the low and medium roughage diets had average daily gains above 1.0 kg per day, except for Brahman and Santa Gertrudis crosses which had daily gains of 0.8 kg per day when fed the low roughage diet. Crosses of South-Devon, Charolais, Santa Getrudis and pure Brahman fed the low roughage diet had cold dressed mass above 200 kg, whilst the Sussex crosses had cold dressed mass of 188 kg.

Based on this information, it is recommended that for animals raised on the range, finishing off should be done using low roughage diets for all breeds. Medium roughage diets can be used but will result in lower gains. Further research is needed to evaluate the digestibility of diets by the animals and to carry out the economics of intensive fattening using locally available feed resources.

Keywords: Beef cattle, carcass grade, conversion, crossbreeds, feedlot, growth, roughage,

Introduction 

The beef industry in Botswana is made up of two production systems; the commercial sector which accounts for 20 percent of the total beef cattle population and the traditional sector which accounts for the remaining 80 percent.  The traditional sector is characterized by low production inputs and low rates of off-take (7%), whilst the commercial sectors off-take accounts for 18% (Bostwana Agricultural Development Policy 1993). For both sectors, beef production is mainly off range with little or no supplementation. This has resulted in a marketing age of 2 and 5 years for the commercial and traditional sectors, respectively (Botswana Meat Commission, personal communication).  Although the majority of slaughter cattle are finished on natural grazing, this does not provide adequate nutrition to enable the large and fast growing animals to express their genetic potential for growth. Nutrition is especially limited during the long dry season and drought years, when both dry matter availability and protein content of natural pasture are very low.  Therefore, it may be necessary to supplement slaughter animals with suitable diets that would allow them to grow faster and attain a good carcass finish at marketing age.  The market price for slaughter stock in Botswana is based mainly on carcass weight and carcass grade, which in turn is determined by age and finish of the animal. The advantage of using breeds with faster growth rates and high mature weights can not be sufficiently exploited  unless adequate  feed resources  in  both quantity and quality  are  available to support such growth  rates.  

Although the indigenous Tswana cattle provide the base for beef production in the country, the use of exotic breeds for crossbreeding purposes, to take advantage of potential heterotic effects, has long been popular.  However, very little information was available on performance of such introduced breeds and their crosses in the country (Lethola et al 1984).  Since the early 1970’s, the Animal Production Research Unit (APRU) has been involved in the evaluation of indigenous and some exotic beef breeds and their crossbreds for beef production.  The breeds evaluated as sire breeds include Tswana and Tuli, Brahman, Africander, Bonsmara, Simmental, Charolais, Sussex, South Devon and Santa Gertrudis.  The result of these studies from some of the above breeds and their crosses showed that only when nutrition and health were not limiting, did the use of exotic breeds and their crosses increase productivity above that of the indigenous Tswana and Tuli cattle.   

Despite the large variation in the quality and quantity of the range, feedlot fattenting is not popular in Botswana (Machacha 1993) because of high cost of conventional feedlot rations, which have to be imported  from neighboring  countries. In 1973/75 APRU conducted a feedlot experiment using imported Rumevite winter and summer concentrate on Brahman, Simmental crosses, purebred Tswana, Afrikaner and Tuli cattle. The study showed that growth rate for crossbred animals was increased during the feedlot period. However, financial benefits from the increase in live weight gains did not justify the higher cost of the feed. The use of locally available crop residues and agro-industrial by- products provides an opportunity for improving the livestock feed resources for use in feedlots. Sorghum stover, a readily available by-product from sorghum grain production can be used as a source of roughage in feedlot diets.  However, since sorghum stover has low nitrogen and higher fibre content , there is need to include feed grade urea in the diets to provide fermentable nitrogen to increase microbes that digest fibre. Other locally available feed resources include wheat bran from milling companies and feed grade sorghum and maize grain available at the Botswana Agricultural Marketing Board (BAMB). These ingredients can be utilized to formulate feedlot diets that will give the required finish for slaughter cattle.  

This paper presents results of a study on the feedlot performance of crosses of Tswana and Tuli cattle fed three different levels of roughage from locally available feed resources. 

The objectives of the study were:

• to evaluate diets of different roughage levels from locally available feed resources for use in feedlot systems.
• to compare growth rates, feed conversion efficiency and cold dressed mass of different types of Tswana crosses fed rations with three levels of roughage from locally available feed resources.   

Material and methods 

Animals 

The study was carried out as part of the beef cattle evaluation program of APRU to assess the performance of crossbreds of the local Tswana and Tuli cattle with exotic beef breeds. The Tuli was included in the cross breeding project because of its close genetic similarity to the Tswana cattle. The study was conducted using 113 entire F1 males of the following breed groups; Brahman (BR), Sussex x Tswana (SUTS), South Devon x Tswana (SDTS), Charolais x Tswana (CHTS) and Santa Gertrudis x Tuli (SGTU). These animals were originally used in the evaluation of sire breeds on range and received only dicalcium phosphate and salt as supplement. At the age of 21 months they were transferred to a central testing station for this study. Due to lack of facilities, the experiment was started in 1994 and repeated in 1995 and 1996.  Due to low numbers of purebred Tswana and Tuli cattle in the experimental stations, the Brahman which is very popular with beef producers in both farming sectors, was used as a base line for comparison.  

Feeding and Management 

At the start of the experiment, animals were given a high roughage diet for an adaptation period of 10 days, drenched orally with Valbazen for internal parasites and injected intramuscularly with vitamins A, D and E. They were then randomly assigned to three groups and allocated to three diets consisting of low (40%), medium (55%) and high (65%) content of sorghum stover roughage, the rest being cracked maize grain and wheat bran (Table 1). The diets were balanced for protein and mineral content. These diets represent the anticipated feedlot production scenarios for the smallholder commercial sector in Botswana. 

During the test period, the animals were individually fed ad libitum for 7 days to determine dry matter intake and thereafter group fed for 35 days.  This cycle was repeated during the 90-day feeding period. Feed offered and refusals were weighed to determine daily feed consumption. Animals were weighed monthly to determine daily gain.  

Slaughter and carcass grading 

After three months in the feedlot, at the age of 24 months, the animals were sent for slaughter at Botswana Meat Commission (BMC). The slaughter and grading of the carcass were done as per Government Livestock and Meat Industry Grading of Carcass Regulation (1982).  The grades are sound super grade (SS) which refers to carcasses with very good conformation, well finished and fleshed with 3-4 permanent incisors, sound grade 1 (S1) are carcasses with good conformation, reasonably finished and fleshed with 2-6 permanent incisors and  under 5 years; sound grade 2 (S2) are carcasses with a fairly good conformation, poorly to well finished and well  fleshed and of age; sound grade 3 (S3) are carcasses with fair conformation, poor finish and fleshing; and detained (D) carcasses are those which have been infested with measles (Cysticercus bovis disease). 

Data analysis

Data on individual feed intake, feed conversion efficiency, daily weight gain and cold dressed mass were subjected to analysis of variance (ANOVA) using the Generalized Linear Model (GLM) of SAS statistical package (SAS 1996). The least significant difference (LSD) test was used to test differences between means for a significant "F" test. The model fitted was:  

Yijkl  =   µ + yeari + breedj + dietk + (year x breed)ij + (year x diet)ik+ (breed x diet)jk + (year x breed x diet)ijk + errorijkl 

Where:    - Yijkl is feed intake, feed conversion efficiency, daily weight gain, cold dressed  mass,
                - µ is the common mean,
                - yeari is the effect of ith year of evaluation (1994, 1995, 1996),
                - breedj is the effect of the jth breed group (BR, CHTS, SDTS, SGTU, SUTS),
                - dietk is the effect of the kth diet (low, medium, high roughage diets),
                - year x breed is the effect of interaction of year by breed,
                - year x diet is the effect of interaction of year by diet,
                - breed x diet is the effect of interaction of breed by diet,
                - year x breed x diet is the effect of year by breed by diet, and error is the residual error. 
 

Results and Discussion 

Diet effects 

The effects of diet on animal performance are shown in Table 2.  Average daily gain for animals fed the low roughage diet were higher (P < 0.05) than gains for those fed the medium and high roughage diets. These results are in agreement with findings of Slabbert et al (1992) who reported a decrease in daily gain as the concentrate: roughage ratio was decreased from (80:20 to 30:70). 

The target live weight gain was considered to be 1.0 kg/day (Weisenburger and Mathison 1987) and was achieved by both the low and medium roughage diets.  Animals fed the low roughage diet had better feed conversion rate than those fed the medium and high roughage diets.  Higher cold dressed mass (CDM) and grades were obtained for animals on the low roughage diet. Due to the very low sub-class numbers for carcass evaluation, a statistically meaningful analysis could not be carried out.  However, it was observed that a higher proportion of animals (54%) on the low roughage diet had grades S2 and higher, compared to 26% and 7% for medium and high roughage diets, respectively.  

Breed effects 

Daily live weight gains

Daily live weight gains were higher in all the crosses than in the purebred Brahman animals. The average daily gains for SDTS, CHTS, SUTS were similar and higher (P < 0.05) than those of SGTU and Brahman (Table 3). The high growth rates observed in the crosses were probably due to both heterotic and additive gene effect for growth and adaptational characteristics. The results observed in this study also indicated that the diets were adequately balanced and of sufficient nutrient density  to enable the crosses to express their growth potential.

Feed intake

Feed intake for the SDTS and CHTS was much higher (P < 0.05) than that of the BR and SGTU. The feed conversion rates for the SGTU, SDTS, CHTS and SUTS crosses were better (P < 0.05) than for purebred Brahman.

Carcass characteristics 

The cold dressed mass for South Devon, Charolais and Santa Gertrudis crosses was higher (P< 0.05) than those for the Sussex crosses and the purebred Brahman, which did not differ from each other (P > 0.05). The Charolais, Santa Gertrudis and South Devon (in this order) are large breeds with a high mature weight while the Sussex breed has the lowest.

Very few carcasses were graded at SS, S1 and S2 since the animals were slaughtered at an older age than required for these grades.  The frequency of the S2 or better was higher for Brahmans (58%), compared to 34% for South Devon, 21% for Charolais and 13% for Sussex.  The Sussex breed is an early-maturing breed and such breeds when fed low roughage diets soon reach a stage of development where a substantial proportion of the energy storage is fat and are therefore downgraded (Allen 1990).  When the diet is poor (high roughage), the animals may not grow fast enough to reach a good finish.  The monetary value of the carcass is determined by cold dressed mass and carcass grade. Santa Gertrudis, South Devon and Charolais had the highest cold dressed mass, and the Brahman, and Sussex had similar but lower cold dressed mass.  Although the Brahman had lower cold dressed mass, most of the Brahman type animals had  higher carcass grade.  The South Devon and Sussex had 3 and 13% of detained carcasses due to Cystisercus  bovis disease.  Cystisercus bovis is the intermediate stage of the human tape worm Taenia saginate which is influenced by sanitary conditions on the farm.

Diet by breed interactions: 

Due to the small number of subclass numbers for diet by breed interactions, a meaningful statistical analysis that permits meaningful discussion cannot be made.  However, it can be reported that the interaction was significant (P < .05) only for daily gain which seems to suggest that the performance of the different breeds differed with diets. 

For the low roughage diet, the CHTS ranked higher than the SDTS and SUTS, followed by SGTU then BR. When the roughage content increased, the weight gain of Charolais crosses decreased and was lower than that of South Devon crosses but was comparable to the Sussex crosses for the medium roughage diet. The weight gains of the Brahman and Santa Gertrudis crosses were similar but lower than daily gains for the South Devon, Charolais, and Sussex crosses for the medium roughage diet. For the high roughage diet, all the crossbreds performed the same and better than the Brahman with the Santa Gertrudis ranking highest. 

Conclusions 

Ultimately, what the farmer looks for are the financial returns of the beef cattle enterprise. The economic and financial viability of feedlot fattening is largely determined by the beef-feed price ratio. This is due to the fact that feed is the major single cost item of the variable costs in a feedlot enterprise. In Botswana, the value of the carcasses in monetary terms depends on its grade and cold dressed mass. These production traits are in turn influenced by the breed group (its potential for growth and mature size) and will vary depending on the specific production environment. The final weight of an animal at slaughter also depends on the rate of growth prior to finishing, particularly when animals are reared on range. Although during the finishing period, some compensatory growth may be observed in previously disadvantaged animals, in this study, this phenomenon has not been high enough to enable the crossbred animals to achieve a better finish.  Due to limitations in feed resources on the range, crosses of large temperate breeds did not have any advantage over Bos indicus type animals in terms of producing carcasses with good finish in the feedlot. Therefore, it may be better to use Bos indicus for feedlot fattening, when the level of nutrition in feedlot diets is limited.

In this study, the low or medium roughage diets are recommended for Charolais, South Devon and Sussex crosses, bearing in mind the need to produce carcasses with adequate conformation and finish, for which the live weight gain should be a minimum of 1.0 kg per day. For Brahman or Santa Gertrudis crosses (tropical breeds), a medium to high roughage diet may be adequate. For animals raised on the range from weaning to 18 months, a daily live weight gain of 0.3 kg has been reported (Animal production and range research unit 1988) and this will probably decline as the animals mature. In this study daily gains of 0.8 kg were obtained for animals fed a high roughage diet, which indicates that such diets would give animals a better finish than those which are marketed off range. However an economic analysis, that compares animals sold off range with those that are finished under feedlot conditions needs to be done to determine if intensive fattening on locally available feed resources is profitable.

Acknowledgements 

Funds for this research were provided by the Botswana Government (GOB). We extend our thanks to the technical staff of the animal nutrition program for collecting the data and entering it to the computer. Lastly, we also wish to extend our appreciation to the industrial staff for mixing the experimental diets and feeding the animals. 

References 

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Animal production and range research unit (APRU) 1988 Livestock and Range Research in Botswana. Government printers, Gaborone, Botswana. 

Botswana Agricultural Development Policy 1993 Government Printers, Gaborone. Botswana. 

Lethola L L,  Buck N G and Light D E 1984 Beef Cattle Breeding in Botswana. Botswana Notes and Records. Volume No. 1. 

Livestock and Meat Industry Grading of Carcass Regulation 1982 Government Printers, Gaborone, Botswana. 

Machacha T F 1993  The future of the livestock industry in Botswana. In: Proceeding of the livestock production workshop on the potential for increasing livestock productivity in Botswana. 14 –17 October 1991 Gaborone, Botswana 

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