Yu Zang

Date of Graduation

2016

Document Type

Thesis

Degree Type

MS

College

Davis College of Agriculture, Natural Resources and Design

Department

Animal and Nutritional Sciences

Committee Chair

Joseph W McFadden

Committee Co-Chair

Eugene E Felton

Committee Member

K M Krause

Abstract

Dairy cows experience extensive lipid mobilization in adipose tissue during the transition from gestation to lactation. A high amount of circulating non-esterified fatty acid (NEFA) results in fatty liver that is associated with reduced milk production (Duffield et al., 2009), metabolic diseases (Hammon et al., 2006), and decreased reproductive performance (Walsh et al., 2007). The function of VLDL is to export TAG from liver. Previous work suggested that micronutrients supplemented may elevated VLDL export. Choline has been shown to increase milk production and milk fat yield (Erdman et al., 1991) and decrease triacylglycerol (TAG) in the liver (Pomfret et al., 1990). Emmanuel et al. (1984) suggested that 28% of absorbed methionine (Met) is used for the synthesis of choline. Also, Met is the first limiting amino acid (AA) for milk protein synthesis of dairy cattle (NRC, 2001) and involved into synthesis of very low-density lipoprotein (VLDL). Furthermore, betaine is a methyl donor that recycles homocysteine to Met after Met is utilized to synthesize phospholipids within VLDL. The set of studies in this master thesis evaluated the effects of Met, choline and betaine on dairy cattle health and performance. In the first experiment, thirty multiparous Holstein cows independently housed were fed total mixed rations (TMR) with or without micronutrients (22 g/d Met, 10 g/d choline chloride, 3 g/d betaine) from -28 d prepartum to d 14 postpartum. All cows received 65 g/d of lipid encapsulate with 62% palmitic acid. Blood and liver samples were collected routinely prepartum and postpartum. Milk yields were recorded, milk samples were collected and milk components were measured after calving. Plasma circulating non-esterified fatty acids (NEFA), beta-hydroxybutyrate (BHBA), glucose, insulin, TAG, total cholesterol, free cholesterol, cholesterol ester, VLDL, and low-density lipoprotein (LDL), and serum total protein, albumin, globulin, hemoglobin, and AA concentrations were measured. Micronutrient supplementation had the tendency to improve milk total solids (TS) percentage (P = 0.11) and had significantly elevated the levels of serum Met at d 10 and 12 (P < 0.05), relative to no supplementation. Similarly, the ratio of lysine (Lys) to Met in cows with micronutrient supplementation was significantly lower than cows without supplementation (P < 0.05). No others treatment effects were observed for metabolites in blood and milk. In the second experiment, twelve multiparous Holstein cows (602 +/- 46 kg body weight (BW), 174 +/- 18 day in milk (DIM)) were used in a replicated 4 x 4 Latin square design with 21-d treatment periods. Dietary treatments included a corn silage and alfalfa haylage-based diet (control; no added Met) supplemented with one of three rumen protected (RP) Met sources (Novimet (Innovad), Smartamine M (Adisseo), and Mepron M85 (Evonik)). Treatments were designed to maintain a Lys:Met ratio of 2.9:1. For control, Lys (RP-Lys; AjiPro) was added at 0.025% ration DM. For RP-Met supplementation, Met (RP-Met) was added at 0.03% ration DM. Cows fed RP-Met were provided Lys (RP-Lys) at 0.20% ration DM. Milk yields were recorded, and samples were collected during each period (d 19 to 21). Blood samples were collected on d 21 at 2, 4, and 6 h following feeding. Milk protein content was elevated with Smartamine M, relative to control or Novimet (3.30% vs. 3.24%, and 3.24% respectively; P < 0.05). There was a tendency for milk urea nitrogen (MUN) to be modified by treatments. Smartamine M increased serum Met concentration (27.3 microM) as compared with control (21.2 microM), Novimet (22.7 microM), or Mepron M85 (23.3 microM) (P < 0.001). In a similar manner, Smartamine M lowered the serum Lys:Met ratio (4.5:1) as compared with control (5.2:1), Novimet (5.2:1), or Mepron M85 (5.1:1) (P < 0.05). Treatments did not modify other milk components and the serum levels of all other AA including Lys. Taken together, results in our studies demonstrate that RP-Met supplementation can increase circulating Met supply and milk protein percentage; however, addition of RP-Met (22 g/d), choline (10 g/d) and betaine (3 g/d) did not show obvious effects on milk production performance and health of dairy cows.

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