The farm gate carbon and water footprint of diverse beef cattle genotypes in South Africa and its environmental impact

Abstract

The aim of this study is to estimate the current farm-gate carbon and blue water footprint of the major beef breeds in South Africa that is representative of the different breed types e.g. Sanga (indigenous), Sanga derived, Zebu, Zebu derived, British and European breeds. A simulation programme was used to simulate the methane production (expressed as methane intensity) and blue water footprint of a weaner calf production system for 9 diverse beef cattle genotypes. The chosen genotypes were based on the number of animals and the availability of data. The breeds involved were: Afrikaner, Nguni, Bonsmara, Angus, Hereford, Brahman, Brangus, Charolais and Simmentaler. The simulation study also involved a farm size of 1200 hectares (ha), with a carrying capacity of 6 hectares per Large Stock Unit (LSU) which could carry 200 LSU’s. Frame size specific equations were used to estimate cow LSU units. The Tier 2 Intergovernmental Panel on Climate Change (IPCC) approach for the methane (CH4) emission values, as already published in the literature was used. Through this approach it was estimated that the enteric methane emissions factor (MEFenteric) of a LSU was equivalent/equal to 94kg methane/year. Furthermore, a 15% replacement rate, 2% pre-weaning mortality, 2% post weaning mortality and a 4% use of breeding bulls were assumed. The blue water use intensity can be estimated in the same way, and it was assumed that for every kg of dry matter intake, a ruminant animal needs 4 litres (L) of water, but it can be increased by 50 % when it is hot. Therefore, an average of 5 litres water intake was used. A LSU needs 9kg dry matter per day and therefore 45 litres of water per day. It was thus estimated that the litres of blue water consumed on the farm was 16 425 litres/year/LSU multiplied by 200 LSU’s which was equal to 3 285 kilolitres. Actual published production values (weaning weight, cow weight, fertility) for each breed was used. For the small frame Afrikaner and Nguni breeds, it was estimated that the methane intensity (kg methane per kg live weight leaving the farm) was 0.60kg and 0.68 kg, respectively. For the medium frame Bonsmara, Angus, Hereford, Brahman and Brangus, the methane intensity was 0.59kg, 0.59kg, 0.64kg, 0.61kg and 0.62kg, respectively. Lastly, for the large frame Charolais and Simmentaler, the methane intensity was 0.85kg and 0.73kg, respectively. The methane intensity varied from 0.59kg CH4 to 0.85kg CH4, which represents a 44% difference. However, when comparing different size breeds, assuming a 10% improvement in each trait, the methane intensity varied from 0.55kg to 0.75kg, vi respectively and a 55% difference was then observed. Moreover, when estimating the water use intensity, it varied from 103 to 148 kilolitres from small to large frame breeds and when a 10% improvement was applied it then ranged from 96 to 131 kilolitres per kg live weight leaving the farm. It was surprising that the Nguni had a medium methane and water intensity, since it is the most fertile breed. However, it should be taken into account that the Nguni was the smallest breed and 147 cows with calves could be kept on the 1 200ha farm. These cows and calves produce large quantities of methane and utilizes large/high water quantities as compared to some of the other breeds. The Afrikaner, Bonsmara, Angus, Brahman and Brangus breeds have low methane and water use intensities and can be regarded as environmentally friendly. The Nguni and Hereford breeds have medium methane and water use intensities while the Charolais and Simmentaler breeds have higher methane and water use intensities. This information can be used to develop a model that can estimate the farm-gate methane emission and water use intensity for different breed types, production levels and systems. Such a model will be valuable in the event that carbon taxes are introduced and total life cycle of water use can be fully analysed.

Xikongomelo xa phurojeke leyi i ku pima khaboni ya sweswi ya farm-gate na mati ya blue water footprint ya tinxaka letikulu ta nyama ya homu e Afrika Dzonga leswi yimelaka tinxaka to hambana ta tinxaka xikombiso Sanga (indigenous), Sanga derived, Zebu, Zebu derived, British na Tinxaka ta le Yuropa. Dyondzo yitirhisiwile ku tekelela vuhumelerisi bya methane (leswi kombisiwaka tani hi matimba ya methane) na blue water footprint ya weaner calf production system eka 9 wa ti genotypes to hambana hambana ta tihomu ta homu. Ti genotypes leti hlawuriweke ati seketeriwile eka nhlayo ya swifuwo xikan’we naku kumeka ka data. Tinxaka leti katsekaka akuri: Afrikaner, Nguni, Bonsmara, Angus, Hereford, Brahman, Brangus, Charolais na Simmentaler. Dyondzo ya simulation yitlhele yi katsa vukulu bya purasi ra 1200 wa ti hectares (ha), laha kungana vuswikoti byo rhwala bya 6 wa ti hectares hi Large Stock Unit (LSU) leyinga rhwala 200 wa ti LSU’s. Kutani ku tirhisiwile ti equations to hlawuleka ta vukulu bya furemu ku ringanyeta tiyuniti ta LSU ta tihomu. Endlelo ra Tier 2 ra Phanele ya le Xikarhi ka Mfumo eka ku Cinca ka Maxelo (IPCC) eka mimpimo ya ku humesiwa ka methane (CH4), tanihilaha se swi kandziyisiweke hakona eka matsalwa. Hiku tirhisa endlelo leri ku ringanyetiwe leswaku enteric methane emissions factor (MEFenteric) ya LSU ayi ringana/ringana na 94kg methane/lembe. Kuya emahlweni, 15% wa nhlayo ya ku cinciwa, 2% wa ku fa ka le mahlweni ka ku lumuriwa, 2% wa ku fa endzhaku ka ku lumuriwa na 4% wa ku tirhisiwa ka tinkunzi leti fuyiwaka swi tekiwile. Kutala ka matirhiselo ya mati ya wasi yanga ringanyetiwa hindlela leyi fanaka, naswona aku ehleketiwile leswaku eka kg yin’wana na yin’wana ya swakudya swo oma leswi dyiwaka xifuwo lexi dyaka swilava 4 wa tilitara (L) ta mati, kambe xinga engeteriwa hi 50 % loko xi hisa. Hikokwalaho, ku tirhisiwile xiringaniso xa 5 wa tilitara ta mati lawa ya dyiwaka. LSU yilava 9kg ya swakudya swo oma hi siku naswona hikokwalaho ka sweswo 45 wa tilitara ta mati hi siku. Xisweswo swiringanyetiwile leswaku tilitara ta mati ya wasi lawa ya tirhisiwaka e purasini akuri 16 425 wa tilitara/lembe/LSU ku andzisiwa hi 200 wa ti LSU leswi ringanaka na 3 285 wa tikhilolitara. Mimpimo ya xiviri ya vuhumelerisi leyi kandziyisiweke (ndzilo wa ku lumuriwa, ntiko wa tihomu, ku veleka) eka muxaka wun’wana na wun’wana wutirhisiwile. Eka tinxaka letintsongo ta frame, Afrikaner na Nguni, aku ringanyetiwa leswaku matimba ya methane (kg methane hi kg ya ntiko lowu hanyaka lowu humaka viii e purasini) akuri 0.60kg na 0.68 kg, hiku landzelelana. Eka furemu yale xikarhi, ya Bonsmara, Angus, Hereford, Brahman, Brangus, matimba ya methane akuri 0.59kg, 0.59kg, 0.64kg, 0.61kg, 0.62kg, hiku landzelelana. Naswona eka furemu leyikulu, Charolais na Simmentaler, matimba ya methane akuri 0.85kg na 0.73kg, hiku landzelelana. Nhlayo ya methane ayi hambana kusuka eka 0.59kg CH4 kuya eka 0.85kg CH4, leswi yimelaka ku hambana ka 44%. Hambiswiritano, loko ku pimanyisiwa tinxaka tohambana hambana ta vukulu, hiku tekela enhlokweni ku cinca ka 10% eka mfanelo yin’wana na yin’wana, matimba ya methane ya hambana kusuka eka 0.55kg kuya eka 0.75kg, hiku landzelelana. Naswona kwalomu ka 55% wa ku hambana ku tlhele ku voniwa. Ku tlula kwalaho, loko ku ringanyetiwa matimba ya matirhiselo ya mati, ya hambana kusuka eka 103 kuya eka 148 kilolitres kusuka eka tinxaka letintsongo kuya eka letikulu ta furemu naswona loko 10% wa ku cinca ku cheriwa kutani akuri kusuka eka 96 kuya eka 131 kilolitres hi ntiko lowu hanyaka lowu humaka e purasini. A swi hlamarisa kuva va Nguni ayiri na methane yale xikarhi xikan’we na mati yotala, tani hileswi kunga muxaka lowu noneke swinene. Hambiswiritano, swifanele ku tekeriwa enhlokweni leswaku Nguni akuri muxaka lowuntsongo swinene naswona 147 wa tihomu letingana marhole tinga hlayisiwa eka purasi ra 1 200ha. Tihomu leti na marhole ya humesa nhlayo leyikulu ya methane naswona ya tirhisa mati lamakulu/yale henhla loko ku pimanyisiwa na tinxaka ta Afrikaner, Bonsmara, Angus, Brahman na Brangus. Tinxaka ta Afrikaner, Bonsmara, Angus, Brahman na Brangus tina methane yale hansi na matirhiselo ya mati naswona tinga tekiwa tani hi letinga onhi mbango. Tinxaka ta Nguni na Hereford tina methane yale xikarhi xikan’we na matirhiselo ya mati kasi tinxaka ta Charolais na Simmentaler tina methane yale henhla xikan’we na matirhiselo ya mati. Mahungu lawa yanga tirhisiwa ku tumbuluxa modele lowu nga ringanyetaka ku humesiwa ka methane ya le purasini xikan’we na matimba ya matirhiselo ya mati eka tinxaka tohambana hambana ta tinxaka, swiyimo swa vuhumelerisi na tisisiteme. Modele wo tano wu ta va wa nkoka loko ko tshuka ku nghenisiwa swibalo swa khaboni naswona xirhendzevutani xa vutomi hinkwabyo xa matirhiselo ya mati xi ta xopaxopiwa hi ku hetiseka.