Effects of Stocking Density on Milk Fatty Acids Composition and Oxidative Stability of Mid- and Late-Lactating Dairy Cows

Shixin Lin; Jianxin Liu; Kaiying Wang; Diming Wang

doi:10.3390/ani8090148

Effects of Stocking Density on Milk Fatty Acids Composition and Oxidative Stability of Mid- and Late-Lactating Dairy Cows

Animals (Basel). 2018 Aug 21;8(9):148. doi: 10.3390/ani8090148.

Authors

Shixin Lin¹, Jianxin Liu², Kaiying Wang³, Diming Wang⁴

Affiliations

¹ Institute of Dairy Science, MoE Key Laboratory of Molecular Animal Nutrition, College of Animal Sciences, Zhejiang University, Hangzhou 310058, China. linshixin@zju.edu.cn.
² Institute of Dairy Science, MoE Key Laboratory of Molecular Animal Nutrition, College of Animal Sciences, Zhejiang University, Hangzhou 310058, China. liujx@zju.edu.cn.
³ College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou 310058, China. zjuwky@zju.edu.cn.
⁴ Institute of Dairy Science, MoE Key Laboratory of Molecular Animal Nutrition, College of Animal Sciences, Zhejiang University, Hangzhou 310058, China. wdm@zju.edu.cn.

Abstract

The objective of the current study was to investigate the effects of stocking density (SD) on the milk fatty acid profile and oxidation stability in mid- and late-lactating cows. Twenty-four multiparous mid-lactating Holstein dairy cows (milk yield = 34.5 kg/d (standard deviation 0.68), days in milk = 106 (standard deviation 2.2)) and 24 multiparous late-lactating animals (milk yield = 31.8 kg/d (standard deviation 0.98), DIM = 201 (standard deviation 3.5)) were allocated into 12 blocks based on parity, milk yield, and DIM and were randomly assigned to one of four treatments: mid-lactating cows with high SD (HSD, 100%), mid-lactating cows with low SD (LSD, 75%), late-lactating cows with HSD, and late-lactating cows with LSD. The experiment lasted for eight weeks. Lactation performance (milk yield and composition including fat, protein and lactose) was measured weekly. The milk fatty acids (FAs) profiles and oxidation stability indexes in milk were measured in the fourth day of the eighth week. Plasma variables were measured in the fourth day of fourth and eighth experimental weeks. Yield and composition (protein, fat and lactose) were not affected by SD in neither mid- nor late-lactating dairy cows. Among mid-lactating cows, LSD cows had higher contents of unsaturated FAs (total, C18:1 cis-9 and C18:2 cis-9 cis-12) and lower concentrations of saturated FAs (total, C14:0 and C16:0) in milk fat than those of the HSD animals. Moreover, LSD lowered SOD, GSH-px, and T-AOC activities and reduced the malonaldehyde content in the milk of mid-lactating cows compared with those of HSD cows. Mid-lactating cows under LSD had reduced cortisol and greater MDA contents in plasma than those of HSD cows. Our results suggested that the effect of SD on the milk FA profile and stability varied depending on lactation stages. In mid-lactating cows, although cows with LSD were less stressed, the milk they produced had lower oxidation stability due to the higher unsaturated FAs levels compared with that of HSD cows.

Keywords: dairy cows; milk fatty acids; oxidative stability; stocking density.