Supplementing high fibre concentrates to Jersey cows grazing kikuyu pastures during summer

Cawood, Jennifer Gail (2016-03)

Thesis (MSc)--Stellenbosch University, 2016.

Thesis

ENGLISH ABSTRACT: Dairy cattle grazing kikuyu pastures are faced with several challenges in nutrient shortages to achieve high milk production. With energy being the first limiting nutrient in kikuyu pastures, supplementation is essential. Currently, high-starch concentrates are used as conventional dairy concentrates. These concentrates are, however, expensive and could affect rumen parameters negatively. Improving the efficiency of production and reducing the cost of supplements could be achieved by replacing energy and protein with cheaper by-products. High fibre by-products can be an economically viable option during periods of high maize and high protein prices. Hominy chop, wheat bran and gluten 20 were used in this study to reduce the price of the supplement. There are many different variables that influence the price of raw materials and these should be taken into account when looking at this study. The objective of the current study was to determine the effect of replacing maize with high fibre by-products in the supplement fed to dairy cows grazing kikuyu pasture on milk production responses and selected rumen parameters. The study was conducted at the Outeniqua Research Farm situated near George in the Western Cape during the summer. A randomised block design was used to allocate 51 cows as follows to the respective treatments (low, medium and high fibre supplement) on the basis of milk yield (kg): 19.8 ± 2.2 (SD), 19.6 ± 1.9, 19.6 ± 1.9, days in milk (DIM): 95.5 ± 41.7, 91.5 ± 46.8, 87.7 ± 40.4, lactation number: 3.9 ± 1.7, 3.9 ± 1.1, 3.9 ± 1.6 and body weight (kg): 387 ± 30.1, 384 ± 23.0, 386 ± 28.7. The low, medium and high fibre treatments contained 78.5, 50.8 and 22.7% maize. Maize was partially replaced by high fibre by-products such as hominy chop, wheat bran and gluten 20. Additionally, six ruminally cannulated Jersey cows were randomly allocated to two treatments (low fibre and high fibre) in a cross-over design. Rumen parameters that were measured included rumen pH, volatile fatty acid (VFA) profile and rumen ammonia nitrogen (NH3-N). Cows were fed 6 kg (split over two milkings per day) concentrate per day and were allocated fresh kikuyu pasture after each milking. Cows grazed the allocated pasture as one group. There were no differences found in milk yield, milk fat, kg fat, fat corrected milk, milk urea nitrogen, and total solids amongst treatments. The milk protein, lactose and solids non-fat (SNF) were 36.6a, 35.3ab, 34.5b g/kg; 47.3a, 47.3a, 44.9b g/kg and; 90.4a, 89.0ab, 87.2b g/kg for the low, medium and high fibre treatment, respectively. Somatic cell count was lower in the low fibre treatment (P < 0.05) 141a, 145b, 230b x103 cells/mLmilk. The rumen pH and rumen NH3-N did not differ between treatments. Total VFA and VFA proportions did not differ between treatments, however, the iso-valeric acid was higher in the high fibre treatment (1.49 vs. 1.23 mmol/dL P < 0.05). There were no signs of clinical acidosis which indicates that rumen health was maintained. It was concluded that by partially substituting maize with high-fibre by-products, milk yield can be sustained. However milk protein, lactose and SNF composition may be lower. The partial substitution of maize with high fibre by-products in dairy concentrates can be used to overcome energy shortages as well as maintain rumen activity and health.

AFRIKAANSE OPSOMMING: Melkkoeie wat permanent op kikoejoeweiding aangehou word, staar vele uitdagings in die gesig ten opsigte van voedingstekorte ten einde hoë melkproduksies te bereik. Aangesien energie die eerste beperkende voedingstof op kikoejoeweiding is, is aanvulling noodsaaklik. Hoëstyselkragvoere word konvensioneel vir melkkoeie gebruik, maar dit is duur en het die potensiaal om die rumenomgewing negatief te beïnvloed. Melkproduksievlakke en die koste van aanvullings kan verbeter deur die energie en proteïen te vervang met goedkoper produkte. Hoëveselprodukte kan ‘n ekonomiese alternatief wees ten tye van hoë mielie- en proteïenpryse. “Hominy chop”, koringsemels en mieliegluten 20 is in die huidige navorsing gebruik om die koste van die aanvulling te verlaag. ‘n Verskeidenheid faktore kan grondstofpryse beïnvloed en dit moet in ag geneem word wanneer hierdie studie in oënskou geneem word. Die doel van die studie was om die invloed van hoëvesel neweprodukte as plaasvervanger vir mielies in aanvullings van weidende koeie op melkproduksie en bepaalde rumenparameters na te gaan. Die navorsing is gedurende die somer op die Outeniqua Proefplaas naby George in die Wes-Kaap gedoen. ‘n Ewekansige blokontwerp is gebruik om 51 koeie as volg aan die onderskeie behandelings (lae-, medium- en hoë-vesel aanvulling) toe te ken op grond van melkproduksie (kg): 19.8 ± 2.2 (SD), 19.6 ± 1.9, 19.6 ± 1.9, dae in melk (DIM): 95.5 ± 41.7, 91.5 ± 46.8, 87.7 ± 40.4, laktasienommer: 3.9 ± 1.7, 3.9 ± 1.1, 3.9 ± 1.6 en liggaamsmassa (kg): 387 ± 30.1, 384 ± 23.0, 386 ± 28. Die lae-, medium- en hoëveselbehandelings het onderskeidelik 78.5, 50.8 en 22.7% mielies bevat. Die mielies is gedeeltelik vervang met “hominy chop”, koringsemels en mieliegluten 20. Verder is ses rumen-gekannuleerde Jerseykoeie ewekansig aan twee behandelings (lae- en hoëvesel) in ‘n omswaai-ontwerp toegeken. Rumenparameters wat gemeet is, sluit in rumen pH, vlugtige vetsure (VVS) en rumen-ammoniakstikstof (NH3-N). Die koeie het elk daagliks 6 kg kragvoer ontvang (3 kg per melkings) en vars kikoejoeweiding was beskikbaar na elke melking. Die koeie het as een groep op die geallokeerde weiding gewei. Geen verskille in melkoproduksie, bottervetinhoud, kg vet, vetgekorrigeerde melkproduksie, melkureumstikstof en melkvastestowwwe is tussen behandelings waargeneem nie. Die melkproteïen, laktose en vetvrye vastestofinhoud was 36.6a, 35.3ab, 34.5b g/kg; 47.3a, 47.3a, 44.9b g/kg and; 90.4a, 89.0ab, 87.2b g/kg vir die lae-, medium- en hoëvesel behandelings. Somatise seltelling was laer in die laeveselbehandeling (P < 0.05) en waardes was onderskeidelik 141a, 145b, 230b x103 selle/ml melk. Die rumen pH en rumen-NH3-N het nie verskil tussen behandelings nie. Totale VVS en VVS proporsies het ook nie tussen behandelings verskil nie, maar die iso-valeriaansuurinhoud was hoër in die hoëvesel behandeling (1.49 vs. 1.23 mmol/dL P < 0.05). Daar was geen tekens van kliniese asidose nie, wat aandui dat rumengesondheid gehandhaaf is. Die gevolgtrekking is gemaak dat melkproduksie gehandhaaf kan word deur die gedeeltelike vervanging van mielies met hoëvesel neweprodukte. Die melkproteïen-, laktose- en vetvrye vastestofinhoud mag egter laer wees. Die gedeeltelike vervanging van mielies met hoëvesel neweprodukte in kragvoeraanvullings vir melkkoei op weiding kan gebruik word om energietekorte te oorbrug en terselfdertyd rumenaktiwiteit en rumengesondheid te behou.

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