Comparison of a liquid supplement of nonprotein nitrogen with urea and soybean meal for lactating cows

Van Horn, H.H.; Mudd, J.S.

Journal of Dairy Science 54: 58-64


ISSN/ISBN: 0022-0302
DOI: 10.3168/jds.s0022-0302(71)85778-8
Accession: 014390730

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A 3 x 3 Latin square design experiment, with 3-wk periods, was carried out on 18 lactating Holstein-Friesian cows, the 3 diets being 10.4 kg of pelletted concentrate (14% protein) + maize silage ad lib. supplemented with (i) 0.9 kg soya bean meal, (ii) 0.9 kg or (iii) 1.8 kg/cow/day of a liquid supplement, containing 13.4% ammonium polyphosphate and 14.8% urea as N sources; all supplements were sprinkled over maize silage. Uncorrected and solids corrected (SCM) milk yields respectively were (kg/day): (i) 22.5 and 17.7; (ii) 22.2 and 17.3; and (iii) 20.8 and 16.1; all values were significantly different from each other (P <0.01). Cows receiving (iii) consumed less maize silage and retained more N (P <0.01) than cows fed (i) or (ii). In a 2nd 3 x 3 Latin square experiment, with 5-wk periods, 3 groups of 8 cows each were fed 76.7% maize silage together with (iv) 18.6% ground shelled maize + 4% soya bean meal + 0.7% mineral and vitamin supplement, (v) 21.2% ground shelled maize + 1% soya bean meal + 0.37% urea + 0.7% mineral and vitamin supplement or (vi) 20.2% ground shelled maize + 1% soya bean meal + 2.1% liquid supplement. Total DM intake and uncorrected milk yield were significantly lower (P <0.05) in cows fed (v) and (vi) than in those fed (iv), and N-retention was significantly higher in cows fed (vi) than (v); there were no significant differences in SCM yields or fat %. The order of plasma urea N levels according to dietary N source was urea > liquid supplement > soya bean meal.