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Journal of Animal Science Abstract - Animal Nutrition

An insufficient glucose supply causes reduced lactose synthesis in lactating dairy cows fed rice straw instead of alfalfa hay1

 

This article in JAS

  1. Vol. 94 No. 11, p. 4771-4780
     
    Received: May 04, 2016
    Accepted: Aug 04, 2016
    Published: October 13, 2016


    2 Corresponding author(s): liujx@zju.edu.cn
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doi:10.2527/jas.2016-0603
  1. B. Wang*†,
  2. F.-Q. Zhao*‡,
  3. B.-X. Zhang* and
  4. J.-X. Liu 2*
  1. * Institute of Dairy Science, MoE Key Laboratory of Molecular Animal Nutrition, College of Animal Sciences, Zhejiang University, Hangzhou 310058, P.R. China
     Beijing Key Laboratory for Dairy Cow Nutrition, College of Animal Science and Technology, Beijing University of Agriculture, Beijing 102206, P.R. China
     Laboratory of Lactation and Metabolic Physiology, Department of Animal and Veterinary Sciences, University of Vermont, 211 Terrill Building, 570 Main Street, Burlington, VT 05505

Abstract

The objective of the present study was to investigate the nutrient availability for milk production in the mammary gland of lactating cows fed different forage-based diets. The 3 diets contained 30% corn stover (CS), 30% rice straw (RS), or 23% alfalfa hay plus 7% Chinese wild rye hay (AH) as a forage source. All diets contained 15% of DM as corn silage and 55% of DM as concentrate. The percentage of milk lactose was always lower in the RS-fed cows than in the cows fed AH or CS during the 12-wk feeding trial (P < 0.01). Ruminal propionate concentrations were lower in the RS group than in the AH group (P = 0.03). The ratio of insulin to glucagon in the mammary venous plasma was greater in the AH group than in the CS or RS group (P = 0.04). The abundance of the pyruvate carboxylase mRNA in the liver was lower in the RS group than in the AH or CS group (P = 0.04), and the abundance of mitochondrial phosphoenolpyruvate carboxykinase, IGF-1 receptor, and phosphofructokinase-liver, phosphofructokinase-muscle, and phosphofructokinase-platelet mRNA in the liver were lower in the RS group than in the AH group (P < 0.05). The mammary glucose uptake was greater in the AH-fed cows than in the CS- or RS-fed cows (P = 0.02). The mRNA abundance of the glucose transporters in the mammary gland was similar among the 3 treatments. The mRNA abundance of α-lactalbumin in the mammary gland of the cows fed RS tended to be greater compared with that of the cows fed AH or CS. The milk potassium concentration was greater in the cows fed RS than those fed AH or CS (P < 0.01). In summary, the insufficient ruminal propionate concentrations in the cows fed RS were associated with lower gluconeogenesis in the liver, resulting in the shortage of glucose supply for mammary utilization.

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