Zendri, Francesco (2008) Indici produttivi, caratteristiche delle razioni e bilancio dei nutrienti (N e P) di 89 allevamenti di vacche da latte in Provincia di Padova. [Laurea triennale]
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In recent years the field of animal husbandry has evolved radically thanks to better management and development of ever more intensive and specialised production systems. The higher quantity of produce has affected the qualitative and quantitative characteristics of manure excreted. Current legislation has indicated as 83 kg/head/year the value of “nitrogen in manure” for dairy cows, however a recent DGR for the Veneto region n. 2439/2007 gives farmers the possibility to draft their own nitrogen balance to estimate the excretion. With the present study nutrient balances were edited for 89 farms located in the province of Padova. An average of “ex storage N” was estimated at 84 kg/head/year. The values for each farm present altogether a high variability, in fact 25% of the total presented a value of only 64 kg/head/year. By filling out the optional nitrogen balance instead of following the MD n. 152 07/04/2006, farmers can use 18% less land for manure disposal. The limited level of nutrient emission for these farms depends on reduced milk production for each head and on reduced values of protein in the animal’s diet. The present research has also defined a few highly productive farms (31,1 kg/head/d) that use reduced crude protein in diets (14,5%). The parameters collected for diet quality and composition for each farm were not sufficient to identify or to study the nutritional strategies that enabled these farms to reach high efficiency in retention of diet N. This research aimed in studying the variability in levels of urea in milk and verify the possibility to use this parameter instead of diet crude protein content to estimate N excretion. With the knowledge available today, the low correlation between the two parameters (R2 = 0,22) does not allow use of the MUN values in the algorithm required to calculate the N balance.
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