Effects of transport stress on physiological responses and milk production in lactating dairy cows

Abstract

Objective: This study was conducted to investigate the effect of transport stress on physiological and hematological responses and milk performance in lactating dairy cows.

Methods: Ten lactating dairy cows were randomly divided into 2 groups. The treatment group (TG) was transported 200 km for 4 h by truck, and the control group (NTG) was restrained by stanchion for 4 h in Konkuk University farm. Blood and milk samples were collected at 24 h pre-transport; 1, 2, and 4 h during transport; and 2, 24, and 48 h post-transport. Milk yields were measured at 24 h pre-transport, 0 h during transport, and 24, 48, and 72 h post-transport.

Results: Leukocyte, neutrophil, and monocyte numbers in the TG were significantly higher than those of the NTG at each experimental time point. Lymphocyte numbers in the TG were significantly (p<0.05) higher than those of the NTG at 48 h post-transport. Additionally, the neutrophil:lymphocyte ratio of the TG was 45% and 46% higher than that of the NTG at 4 h during transport and 2 h post-transport, respectively. There were no significant differences in erythrocyte numbers, hemoglobin concentrations, platelet numbers, and hematocrit percentages between two groups. Cortisol levels in the TG were significantly (p<0.05) higher than those in the NTG. Milk yields in the TG were lower than those in the NTG. The somatic cell count (SCC) of the TG was significantly (p<0.05) higher than that of the NTG at 1 and 2 h during transport; that of the TG increased dramatically at 1 h during transport and gradually decreased subsequently.

Conclusion: Transport stress increased blood parameters including leucocyte, neutrophil, and monocyte numbers by increased cortisol levels, but did not affect erythrocytes, hemoglobin and hematocrit levels. Additionally, transport resulted in a decrease in milk yield and reduced milk quality owing to an increase in milk SCC.

Keywords: Hematological Responses; Milk Production; Physiological Response; Transport Stress.

Figure 1

Schematic diagram of the experiment. Blood and milk samples were collected 7 times: pre-transport (−24 h), during transport (1, 2, 4 h), and post-transport (+2, +24, +48 h). Milk yields were measured every morning for 4 days.

Figure 2

Effects of transport stress on white blood cell and differential counts in lactating cows. White blood cell count (A), numbers of neutrophils (B), lymphocytes (C), monocytes (D), and eosinophils (E), and neutrophil:lymphocyte ratio (F) were measured for the pre-transport (−24 h), during transport (1, 2, 4 h), and post-transport (+2, +24, +48 h). NTG, non-transported group; TG, transported group. ■ ●: Represent the significant difference (p<0.05) in the data after transport periods compared with pre-transport (−24 h). Asterisks mean significant difference between NTG and TG (* p<0.05, ** p<0.01, *** p<0.001).

Figure 3

Effects of transport stress on blood parameters in lactating cows. Erythrocyte (A), hemoglobin (B), hematocrit (C), and platelet (D) were measured for the pre-transport (−24 h), transport (1, 2, 4 h), and post-transport (+2, +24, +48 h). NTG, non-transported group; TG, transported group. ■ ●: Represent the significant difference (p<0.05) in the data after transport periods compared with pre-transport (−24 h).

Figure 4

Effects of transport stress on serum cortisol in lactating cows. Serum cortisol was measured for the pre-transport (−24 h), transport (1, 2, 4 h), and post-transport (+2, +24, +48 h). NTG, non-transported group; TG, transported group. ■ ● : Represent the significant difference (p<0.05) in the data after transport periods compared with pre-transport (−24 h). Asterisks mean significant difference between NTG and TG (* p<0.05, ** p<0.01, *** p<0.001).

Figure 5

Effects of transport stress on daily milk yields and milk composition in lactating cows. Milk yield (A) was measured for the pre-transport (−24 h), transport (0 h), and post-transport (+24, +48, +72 h). Milk fat (B), protein (C), lactose (D), solid-not-fat (E), and milk urea nitrogen (F) were measured for the pre-transport (−24 h), transport (1, 2, 4 h), and post-transport (+2, +24, +48 h). NTG, non-transported group; TG, transported group. ■ ●: Represent the significant difference (p<0.05) in the data after transport periods compared with pre-transport (−24 h). Asterisks mean significant difference between NTG and TG (*p<0.05, ** p<0.01, *** p<0.001).