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Asian-Australas J Anim Sci > Accepted
doi: https://doi.org/10.5713/ajas.16.0564    [Accepted]
Effect of Increasing Dietary Metabolizable Protein on Nitrogen Efficiency in Holstein Dairy Cows
Muhammad Imran, Talat Naseer Pasha, Muhammad Qamer Shahid1, Imran Babar2, Muhammad NAVEED UL HAQUE*
University Of Veterinary And Animal Sciences Lahore, Lahore, Pakistan
1Department of Livestock Production, University of Veterinary and Animal Sciences, Lahore, 54000, Pakistan
2Sharif Dairy Farms, Chiniot, Pakistan
* Corresponding Author: Muhammad NAVEED UL HAQUE ,Tel: 09242992113, Fax: 99211461, Email: mnaveedulhaque@gmail.com
Received: 24 July 2016;  Revised: 24 October 2016.  Accepted: 18 November 2016.  Published online 24 November 2016.

ABSTRACT
The objective of the study was to determine the effects of increasing levels of metabolizable protein (MP) on lactation performance and nitrogen (N) efficiencies in lactating dairy cows. Nine multiparous cows in mid lactation [113±25 days in milk (DIM)] received three treatments in a 3×3 Latin square design with a period length of 21 days. The treatments were three diets, designed to provide similar energy and increasing supply of MP (g/d)—2371 (low), 2561 (medium), and 2711 (high) with corresponding crude protein (CP) levels (%)—15.2, 18.4, and 20.9, respectively. Increasing MP supplies did not modify dry matter intake (DMI), however, it increased milk protein, fat, and lactose yield linearly. Similarly, fat corrected milk (FCM) increased linearly (9.3%) due to an increase in both milk yield (5.2%) and milk fat content (7.8%). No effects were observed on milk protein and lactose contents across the treatments. Milk nitrogen efficiency (MNE) decreased from 0.26 to 0.20; whereas, the metabolic efficiency of MP decreased from 0.70 to 0.60 in low to high MP supplies, respectively. The concentration of blood urea nitrogen (BUN) increased linearly in response to increasing MP supplies. Increasing MP supplies resulted in increased milk protein yield; however, a higher BUN and low MNE indicated an efficient utilization of dietary protein at low MP supplies.
Keywords: Dairy cows; Metabolizable protein; Milk production; Milk nitrogen efficiency
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