Melamine, from fertilizer to pasture to cow’s milk

Botha, Dawn Dorothy (2010-12)

Thesis (MScAgric (Animal Sciences))--University of Stellenbosch, 2010.

Thesis

ENGLISH ABSTRACT: The aim of this study was to determine the rate of transfer of melamine as fertilizer ingredient to kikuyu pastures and if melamine would be transferred from the fertilized pasture to cow’s milk. Three trials were conducted in the study, viz. a pilot pot plant trial, an applied pasture trial and a milk production trial. Melamine is a commercially available industrial chemical with a high nitrogen content. Large quantities of melamine waste can sometimes be incorporated into crop and pasture fertilizers due to the high N content. An initial pot plant trial with kikuyu was conducted to determine whether melamine would be absorbed as such from the soil to the plant material. The pots were fertilized in the form of melamine adulterated Chinese maize Gluten 60, at a rate equivalent to 8.8 kg of melamine/ha. Results indicated that melamine was indeed absorbed and 7 days after fertilization, the concentration of melamine in the grass was 228 mg/kg. An applied pasture trial was then conducted were three pastures of 0.3 ha each were used. One pasture served as a control and received N fertilization in the form of LAN at a rate of 40 kg N/ha. The other two pastures also received LAN, but with 10% (Treatment 1) and 20% (Treatment 2) of the LAN-N substituted with melamine-N. All three pastures also received P-fertilization in the form of Single Superphosphate at a rate of 20 kg P/ha and KCl fertilizer at a rate of 50 kg K/ha. Pasture samples were taken once a week for 10 weeks, each time at the exact same spot in each camp. Samples were dried and finely milled before analysis via LC-MS/MS for melamine content. The initial concentration of melamine in the grass of Treatment 2 was higher than that in the grass of Treatment 1. The rate at which melamine decayed in the plant material was found to be quite similar for the two melamine treatments. In this trial, melamine took around 10 weeks to reach undetectable levels in the grass. It was concluded that melamine was absorbed as such from the soil by pasture grass when included in a fertilizer. For the milk production study, eighteen lactating Holstein cows, 60 ± 5.1 (SE) DIM, with a daily milk production of 36.5 ± 2.0 (SE) kg/d and weighing 609 ± 12.8 (SE) kg, were stratified according to milk production and then randomly allocated to three groups of six cows. The groups were then randomly allocated to the three pastures used in the applied pasture trial. Cows were kept on the melamine fertilized pasture for 9 days, in which they were allowed to graze the pasture for approximately 10 hours each day. After the 9 day period, melamine was withdrawn by placing the cows on the control pasture that did not receive melamine contaminated fertilization for another 7 days. During these 16 days, milk was collected twice a day, viz. during the morning and afternoon milkings. Milk samples of each cow were sub-divided into two samples, one was preserved with potassium dichromate and analysed for milk composition and the other was frozen until analysed for melamine by LC-MS/MS. For the duration of the trial, melamine containing milk was destroyed in order to prevent it from contaminating milk collected from the rest of the herd. Results from the analysis for melamine confirmed that melamine was transferred from melamine fertilized pasture to milk. In this study, it took 6 days from melamine withdrawal for melamine to reach undetectable levels in the milk. It was also found that the melamine fertilized pasture did not have any significant effect on the average milk production and milk composition of the cows. The aim of the study was met and it was confirmed that melamine can be transferred from fertilizer to the soil, to the pasture and to the milk of cows grazing these pastures.

AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om die tempo van oordrag van melamien as bemestingstof na Kikuyu weiding te bepaal, asook om te bepaal of melamien oorgedra sal word vanaf die bemeste weiding na melk. Drie proewe is uitgevoer wat ‘n potplant loodsproef, ‘n toegepaste weidings proef en ‘n melkproduksie proef ingesluit het. Melamien is ʼn kommersieël-beskikbare industriële chemikalieë met ʼn hoë stikstof inhoud. Groot hoeveelhede van melamien-afval kan soms in kunsmis ingesluit word vir die bemesting van gewasse en weidings, weens die hoë stikstof inhoud van melamien. ʼn Potplant loodsproef met Kikuyu is uitgevoer om te bepaal of melamien vanaf die grond deur die plantmateriaal geabsorbeer word. Melamienbemesting is in die vorm van vervalste Chinese mieliegluten 60 toegedien teen ʼn hoeveelheid gelykstaande aan 8.8 kg melamien/ha. Die resultate van hierdie proef het getoon dat melamien wel deur die plantmateriaal geabsorbeer is en 7 dae nadat bemesting toegedien is, was die konsentrasie van melamien in die gras 228 of mg/kg. ʼn Toegepaste weidingstudie is uitgevoer waar drie kampe van 0.3 ha elk gebruik is. Een van die kampe het as ʼn kontrole gedien en het stikstof bemesting in die vorm van KAN teen 40 kg N/ha ontvang. Die ander twee kampe het KAN bemesting ontvang waar 10% (Behandeling 1) en 20% (Behandeling 2) van die KAN-N deur melamien-N vervang is. Al drie kampe het ook fosfaatbemesting in die vorm van Enkel Superfosfaat ontvang teen 20 kg P/ha, asook KCl kunsmis teen 50 kg K/ha. Weidingmonsters is eenmaal per week op dieselfde plek in elke kamp geneem vir 10 weke nadat bemesting toegedien is geneem. Monsters is gedroog en daarna fyngemaal voordat dit vir melamieninhoud geanaliseer is met behulp van LC-MS/MS. Die aanvanklike melamienkonsentrasie in die gras van Behandeling 2 was hoër as die in die gras van Behandeling 1. Die tempo waarteen die melamienkonsentrasie in die plant materiaal afgeneem het, was baie dieselfde vir Behandelings 1 en Behandeling 2. Dit het ongeveer 10 weke geneem voordat die melamien in die gras nie-waarneembare vlakke bereik het. Die gevolgtrekking is gemaak dat melamien wat in die vorm van kunsmis toegedien word, as sodanig uit die grond geabsorbeer word deur die gras. Vir die melkproduksiestudie is agtien lakterede Holsteinkoeie, 60 ± 5.1 (SE) dae in melk, met ‘n daaglikse melkproduksie van 36.5 ± 2.0 (SE) kg/dag en ‘n liggaamsmassa van 609 ± 12.8 (SE) kg, volgens hul melkproduksie gerangskik en ewekansig in drie groepe van ses koeie elk ingedeel. Die groepe is daarna ewekansig aan die drie kampe, wat in die toegepaste weidingstudie gebruik is toegedien. Die koeie is vir 9 dae op die melamienbemeste weidings gehou, waartydens hulle toegelaat is om vir ongeveer 10 ure elke dag te wei. Na die tydperk van 9 d, is die koeie vanaf die melamienbemeste weidings onttrek deur hulle op die kontroleweiding te plaas vir ʼn verdere 7 dae. Gedurende hierdie 16 dae is melkmonsters tweekeer per dag geneem, tydens die oggend- en die middagmelkings. Die melkmonsters van elke koei is vervolgens onderverdeel in twee monsters, waarvan een met kaliumdichromaat gepreserveer is vir die beplaing van melksamestelling, terwyl die ander een gevries is totdat dit later vir melamien inhoud ontleed is met behulp van LC-MS/MS. Melk van die koeie wat op die melamienweidings gewei het, is weggegooi om te voorkom dat melk van die res van die kudde gekontamineer kon word. Die resultate van die melamienanalises het getoon dat melamien oorgedra word vanaf die melamienbemeste weiding na die melk. Tydens hierdie studie het dit 6 dae geneem vandat koeie vanaf die melamienbemeste weidings onttrek is, totdat die melkmelamien nie-bepaalbare vlakke bereik het. Daar is bevind dat melamienbemeste weidings geen betekenisvolle uitwerking op die gemiddelde produksie en samestelling van die melk gehad het nie. Die doel van hierdie studie is bereik en daar is getoon dat melamien vanaf kunsmis na die grond, na die gras en na die melk oorgedra kan word wanneer koeie op weidings geplaas word wat melamienbemeste kunsmis ontvang het.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/5455
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