| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
1 Department of Animal Husbandry and Production, Faculty of Veterinary Medicine and
2 Department of Animal Science and Production, Faculty of Agriculture, University College Dublin, Belfield, Dublin 4, Ireland
3 Dairy Production Department, Teagasc, Moorepark Research Centre, Fermoy, Co. Cork, Ireland
Corresponding author: F. Mulligan; e-mail: finbar.mulligan{at}ucd.ie.
These experiments were designed to investigate nutritional means of reducing urine N excretion by grazing cows. In experiment 1, 36 Holstein-Friesian cows averaging 92 d in milk were fed either 1 or 6 kg of a high protein concentrate or 6 kg of a low protein concentrate. Pasture dry matter (DM) intake was higher for cows fed 1 kg of high protein concentrate (15.4 ± 0.62 kg/d) than for cows fed 6 kg of low protein concentrate (13.4 ± 0.55) but not for cows fed 6 kg of high protein concentrate (13.9 ± 0.96). The reduction in pasture intake per kg of concentrate DM ingested amounted to 0.35 and 0.47 kg of pasture DM for cows fed 6 kg of high protein and 6 kg of low protein concentrate, respectively. Milk yield and milk protein yield were higher for cows fed 6 kg of high protein concentrate than for cows fed 1 kg of high protein concentrate. Cows fed 6 kg of high protein concentrate had the highest levels of N intake, total N excretion, and urine N excretion. The proportion of N excreted in the urine was lowest for cows fed 6 kg of low protein concentrate. Milk N excretion as a proportion of ingested N was higher for cows fed 6 kg of low protein concentrate than for cows fed 6 kg of high protein concentrate but not for cows fed 1 kg of high protein concentrate. In experiment 2, 24 Holstein-Friesian cows averaging 211 d in milk were supplemented with 4 kg of rolled barley or 4.32 kg of NaOH-treated barley. Milk yield and milk protein yield tended to be higher for cows fed rolled barley than for cows fed NaOH-treated barley. There was no difference in N intake, fecal N excretion, urinary N excretion, or milk N output between diets. Milk urea N concentration was lower for cows fed rolled barley. Significant positive linear relationships were found between N intake and fecal N excretion, urine N excretion, and milk N excretion in experiment 1. In experiment 2, the relationships between N intake and fecal N excretion and urine N excretion were curvilinear, with urine N excretion increasing at a decreasing rate, and fecal N excretion increasing at an increasing rate, as N intake increased. The N excreted by dairy cows may be partitioned to fecal N if supplements based on high concentrations of fermentable organic matter and low concentrations of N are fed. Refinement of this nutritional strategy may allow reduced N excretion without reducing animal performance.
Key Words: dairy cow • nitrogen excretion • milk production • grazing
Abbreviation key: DMD = dry matter digestibility, HP6 = pasture-based diet containing 6 kg/d of high protein concentrate, HP1 = pasture-based diet containing 1 kg/d of high protein concentrate, LP6 = pasture-based diet containing 6 kg/d of low protein concentrate, RB = pasture-based diet containing rolled barley, NaB = pasture-based diet containing sodium hydroxide-treated barley.
This article has been cited by other articles:
|
|
 |
|
  O. A. Rego, S. M. M. Regalo, H. J. D. Rosa, S. P. Alves, A. E. S. Borba, R. J. B. Bessa, A. R. J. Cabrita, and A. J. M. Fonseca Effects of Grass Silage and Soybean Meal Supplementation on Milk Production and Milk Fatty Acid Profiles of Grazing Dairy Cows J Dairy Sci, July 1, 2008; 91(7): 2736 - 2743. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
F. Burke, J. J. Murphy, M. A. O'Donovan, F. P. O'Mara, S. Kavanagh, and F. J. Mulligan Comparative Evaluation of Alternative Forages to Grass Silage in the Diet of Early Lactation Dairy Cows J Dairy Sci, February 1, 2007; 90(2): 908 - 917. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
