Comparing feed use efficiency and enteric gas production of Holstein and Jersey cows in a kikuyu pasture-based system using mathematical models

Bangani, Noluvuyo Muriel (2020-03)

Thesis (PhDAgric)--Stellenbosch University, 2020.

Thesis

ENGLISH ABSTRACT: Feed use efficiency to synthesise maximum amounts of milk while ensuring responsible use and protection of the environment is of significance for sustainable milk production. The aim of this study was to compare factors affecting milk production, nutrient use and enteric gas production efficiencies of Holstein and Jersey cows that were reared under similar environmental conditions and management practices. Data used were lactation records of 122 Holstein and 99 Jersey cows, collected from 2005 to 2014. Records included cow birth date, calving date, lactation number, body weight (BW), kg milk yield (MY), % fat (MF) and % protein (Mprot). Cows were reared as one herd on kikuyu pasture and received on an as-fed basis 7 kg of concentrate containing 17% crude protein (CP) per day, fed in two equal portions after each milking. The total dry matter intake (DMI) was estimated using the National Research Council (NRC, 2001) method. Pasture intake was calculated as the difference between DMI and concentrate dry matter intake. The mean DMI, MY, kg MF and kg Mprot were higher in Holsteins while Jerseys had higher %MF and %Mprot. Jersey MY was 74% but when corrected to energy corrected milk (ECM), 85% that of Holsteins. Milk increase from primiparous to mature cows (parity ≥4) was 26.5% in Holsteins and 23.7% in Jerseys. Age at first calving (AFC) did not differ between breeds. The calving season (CS) did not affect mean test-date MY but cows that calved in summer had a flatter lactation curve. Mean lactation number was lower and the inter-calving period (ICP) longer in Holsteins than Jerseys. Cows with the ICP below 13 months tended to produce on average less 305-day milk yield. Jersey cows showed higher efficiency in DMI/kg BW, MF/kg DMI, Mprot/kg DMI, ECM/kg DMI, ECM/kg BW and MY/100 kg BW. Holsteins were efficient in MY/kg DMI. Both breeds were in negative energy balance (NEB) during the transition and early lactation stages, with Holsteins having longer and more intense NEB. The net energy intake (NEI)/kg ECM, NEI/kg metabolic BW (BW0.75) and net energy for maintenance (NEm)/kg BW0.75 were higher in Holsteins compared to Jerseys. However, after accounting for NEm, (NEI-NEm)/ECM, Holsteins had higher gross energy efficiency. Milk nitrogen (MN)/nitrogen intake (NI) was higher in Jerseys compared to Holsteins. The NI/kg BW0.75 did not differ between breeds. Jerseys had higher faecal nitrogen (FN)/100 g NI but lower urinary nitrogen (UN)/100 g NI, protein requirements for scurf losses (SPA) and therefore lower manure nitrogen (ManN)/kg NI than Holsteins. Holsteins produced more kg carbon dioxide (CO2)/day, but low CO2/kg DMI and CO2/100 kg BW than Jerseys. Breeds did not differ in CO2/kg ECM. Holsteins emitted less methane (CH4) g/kg DMI and CH4/100 kg BW, while Jersey emitted less CH4/kg ECM. Mature cows produced on average 16% more CH4 than their primiparous counterparts. With lactation stages, the highest CH4 emissions were observed during mid-lactation with cows producing on average 28% more daily CH4 when compared to the transition period. This indicates that accounting for production stages in estimating the methane emission factor (MEF, CH4/head/year) will bring more accuracy and can therefore be recommended for regional and national inventories for SA dairy breeds. From this study, it can be concluded that neither of the breeds were overall more efficient regarding all traits, but Jersey cows showed higher efficiency in most measured traits.

AFRIKAANSE OPSOMMING: Voerverbruik-doeltreffendheid om die maksimum hoeveelheid melk te sintetiseer, terwyl die verantwoordelike gebruik en beskerming van die omgewing is van belang vir volhoubare melkproduksie. Die doel van hierdie studie was om faktore wat melkproduksie, voedingstowwe en die doeltreffendheid van enteriese gasproduksie beïnvloed, te vergelyk tussen Holstein- en Jersey koeie wat onder soortgelyke omgewingstoestande en bestuurspraktyke grootgemaak is. Data wat gebruik is, het laktasierekords van 122 Holstein- en 99 Jersey-koeie onderskeidelik, wat van 2005 tot 2014 versamel is, ingesluit. Verslae het inligting oor die koeie se geboortedatum, kalwingsdatum, laktasienommer, liggaamsgewig (BW), kg melkopbrengs (MY), % vet (MF) en % proteïen (Mprot), ingesluit. Koeie is as een kudde op kikuju weiding grootgemaak en 'n 7 kg konsentraat wat 17% ru-proteïen (CP) per dag bevat, is in twee gelyke porsies na elke melking gevoer. Die totale droëmateriaal inname (DMI) is geskat volgens die NRC-metode. Weidingsinname is bereken as die verskil tussen DMI en konsentraat droëmateriaalinname. Die gemiddelde DMI, MY, kg MF en kg Mprot was hoër in Holsteins, terwyl die Jersey melk hoër MF en % Mprot gehad het. Jersey MY was 74%, maar as dit aangepas is vir energie-gekorrigeerde melk (ECM), was dit 85% van Holstein produksie. Melkverhoging van primêre en volwasse koeie (pariteit ≥4) was 26,5% in Holstein- en 23,7% in Jersey koeie. Ouderdom met eerste kalwing (AFC) het nie tussen die rasse verskil nie. Die kalfseisoen (CS) het nie die gemiddelde toetsdag MY beïnvloed nie, maar koeie wat in die somer gekalf het, het 'n vlakker laktasiekurwe gehad. Gemiddelde laktasie nommer was laer en die tussenkalfperiode (ICP) langer in Holstein- as in Jersey koeie. Koeie met die TKP onder 13 maande was geneig om gemiddeld minder melk op dag 305 te produseer. Jersey-koeie het ʼn hoër doeltreffendheid getoon in DMI / kg BW, MF / kg DMI, Mprot / kg DMI, ECM / kg DMI, ECM / kg BW en MY / 100 kg BW. Holstein koeie was doeltreffend in terme van MY / kg DMI. Albei rasse het ʼn negatiewe energiebalans (NEB) ervaar tydens die oorgangs- en vroeë laktasiefases, met Holsteins wat ʼn langer en strawwer NEB ervaar het. Die netto energie-inname (NEI) / kg ECM, NEI / kg metaboliese BW (BW0.75) en die netto energie vir onderhoud (NEm) / kg BW0.75 was hoër in Holsteins in vergelyking met truie. Na die inagneming van NEm, (NEI-NEm) / ECM, het Holsteins egter ‘n hoër bruto energie-doeltreffendheid gehad. Melk stikstof (MN) / stikstofinname (NI) was hoër in die Jersey koeie in vergelyking met die Holsteins. Die NI / kg BW0,75 het nie tussen rasse verskil nie. Die Jersey koeie het hoër fekale stikstof (FN) / 100 g NI, maar laer urien stikstof (VN) / 100 g NI, proteïenvereistes vir skurfverliese (SPA) en dus laer misstof stikstof (ManN) / kg NI as Holsteins gehad. Holstein koeie produseer meer kg koolstofdioksied (CO2) / dag, maar het 'n laer CO2 / kg DMI en CO2 / 100 kg BW wanneer vergelyk met Jerseys. Rasse het nie verskil in terme van CO2 / kg ECM nie. Holsteins het minder metaan (CH4) g / kg DMI en CH4 / 100 kg BW vrygestel, terwyl Jersey minder CH4 / kg ECM vrygestel het. Volwasse koeie produseer gemiddeld 16% meer CH4 as hul eweknieë. Met die laktasiefase is die hoogste CH4-emissies waargeneem tydens mid-laktasie, met koeie wat gemiddeld 28% meer daaglikse CH4 produseer in vergelyking met die oorgangstydperk. Dit dui daarop dat die berekening van die produksiefases in die beraming van die metaan-emissiefaktor (MEF, CH4 / kop / jaar) meer akkuraatheid sal meebring, en dit kan dus aanbeveel word vir streeks- en nasionale voorrade vir SA suiwelrasse. Uit hierdie studie kan die gevolgtrekking gemaak word dat geen van die rasse in die algemeen doeltreffender was ten opsigte van alle eienskappe nie, maar dat Jersey-koeie hoër doeltreffendheid getoon het in die meeste gemete eienskappe.

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