Browsing by Author "Bangani, Noluvuyo Muriel"

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    Comparing feed use efficiency and enteric gas production of Holstein and Jersey cows in a kikuyu pasture-based system using mathematical models
    (Stellenbosch : Stellenbosch University, 2020-03) Bangani, Noluvuyo Muriel; Dzama, Kennedy; Muller, C. J. C.; Cruywagen, C. W.; Nherera-Chokuda, F.; Stellenbosch University. Faculty of AgriSciences. Dept. of Animal Science.
    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.