Effect of 2,4-thiazolidinedione treatment in milk production and leukocytes phagocytosis after sub-clinical mastitis induction in lactating dairy goats
Mastitis is one of the most costly diseases for the dairy industry. There is indirect evidence suggesting that peroxisome proliferator-activated receptor gamma (PPARγ) regulates milk fat synthesis and may help to prevent mastitis.
We postulate that continuous activation of PPARγ in the mammary gland can improve response to sub-clinical mastitis and increase milk fat synthesis.
To test this, 25 lactating Saanen goats received either 8 mg/kg BW daily intravenous injections of the PPARγ activator 2,4-thiazolidinedione (TZD) or saline. Following one week of treatment, half of the TZD and half of the saline treated goats received intramammary infusion (IMI) of 1.7×108 CFU/mL of Streptococcus uberis (S. uberis)in both mammary halves (MTZD and MCTR) while the remaining goats in each group received IMI of saline (CTZD and CTRL). Animals were monitored for 12 days after IMI. Milk was collected daily during the trial to measure yield and composition, including somatic cell count (SCC). Bacteriological analysis of the milk was performed before infusion and 24 h after IMI. Rectal temperature (RT) was assessed daily after IMI. Blood was collected during the trial to assess leukocytes phagocytosis. Body weight and body condition score (BCS) were assessed weekly. Data were analyzed using GLIMMIX of SAS with TZD, IMI, time and all interactions as main effect and goat ID as random. Significance was determined with a Tukey-adjusted P<0.05.
Milk SCC increased significantly after IMI in goats infused with S. uberis but the goats receiving TZD had an overall lower SCC. There was a significant decrease in milk yield in mastitis groups but no effect of TZD. There was a decrease in milk fat (mg/d) after IMI in MCTR, while the MTZD group maintained milk fat comparable to non-mastitis groups. The mastitis groups had a much higher percentage of milk protein than non-mastitis groups but no TZD effect was observed. Compared to two days before, after IMI we observed a decrease in % blood neutrophils and increase in % lymphocytes which was larger in goats infused with S. uberis. The phagocytic activity of monocytes increased more in groups infused with saline compared to S. uberis.No effect on body weight, BCS, and rectal temperature was observed. The results confirmed successful induction of sub-clinical mastitis, uncovered a positive effect of TZD on SCC and in preventing milk fat depression due to sub-clinical mastitis, but TZD treatment did not affect leukocytes.
Keywords: PPARγ, Goat, Subclinical mastitis