The Effect Of Temperature And Artificial Wind On Energy Budget During Lactation In Swiss Mice

To some extent,animals can adapt to changes in the natural environment,which including temperature,photoperiod,seasonal changes in food quality and richness,through the adaptive adjustment of energy budgets.Ambient temperature is the main factor affecting the energy budget of lactating animals.With the frequent occurrence of heat waves,which threat many aspects of animal physiology and behavior.Animals,in lactation period,have reduced heat dissipation capacity at high temperatures and increased risk of hyperthermia.Most terrestrial animals have increased heat loss when exposed to the wind.However,the effect of high temperature and wind on the energy intake and reproductive performance of small mammals are still unclear.In order to explore the effect of temperature and wind on the energy budget of lactating mice we designed three experiments in this study.1)Divide non-reproductive Swiss mice into four groups randomly,named 21°C no-wind group,21°C wind group,32.5°C no-wind group,32.5°C wind group.After a week of normal rearing,the experimental mice were transferred to the above-mentioned experimental environment and reared until the 16 th day.During this period,we measured energy budget and tissue organ weight.2)The lactating Swiss mice were randomly divided into four groups,named 21°C no wind group,21°C wind group,32.5°C no wind group,32.5°C wind group.They are transferred into the above experimental conditions on the 7th day of the lactation period and until the 16 th day.We measured changes in food intake,maternal weight,fetal weight and lactation expenditure,and determine the expression of breast tissue and lactation-related genes.3)a.Divide lactating Swiss mice into two groups randomly,named 32.5°C without wind group and 32.5°C wind group.These mice can choose wind freely,they can stay on the side with wind or stay on the side without wind.And switch to the above-mentioned experimental environment on the 7th day of the lactation period and until the 16 th day.We measured changes in food intake,maternal weight,fetal weight and lactation expenditure.b.The lactating Swiss mice were randomly divided into four groups,named 21°C control group,21°C windy group,32.5°C control group,32.5°C windy group.All these mice can freely choose the wind.On the 7th day of the lactation period,they were transferred to the above-mentioned environment.During the peak period of lactation,the female mice and pups in the wind group at 21°C and 32.5°C were observed every 10 minutes from 6 to 10 in the morning and evening.Time and record the number of pups were recorded.The breast tissues of the four groups were collected on the 17 th day of lactation,and the morphology and size of breast cells in the breast tissue were measured by HE staining.The results we found showed: 1)The food intake,gross energy intake,digestive energy intake and resting metabolic rate of the 32.5? group were reduced by 47.5%(P<0.01),24.3%(P<0.01),and 24.0%(P<0.01),22.4%(P<0.01),compared with the 21? group.Besides,the weight of subcutaneous fat weight and perirenal fat weight in the 32.5? group increased by 33.1%(P<0.01)and 37.5%(P<0.05)respectively,and food intake was 20.6%higher than that in the no-wind group(P<0.05).2)The maximum food intake,fetal weight,lactation expenditure,Stat5 a and Stat5 a protein expression in the 32.5°C group were respectively reduced by 45.8%(P<0.01),15.6%(P<0.01),26.8%(P<0.01),38.2%(P<0.05),45.0%(P<0.05)compared to those in the 21°C group.The maximum food intake and lactation expenditure of the wind group increased by 21.6%(P<0.01),10.6% compared with the no wind group(P<0.01).The maximum food intake and lactation expenditure of the wind group increased by 21.6%(P<0.01)and 10.6%(P<0.01)compared with the no wind group.3)The animals in the windy group mainly took their food on the windy side.The food intake of the windy group was 37.6% higher than that of the no wind group(P<0.01),and the food intake on the side with the feeding wind was160.4% higher than that on the side with no wind.In addition,the maximum food intake,lactation expenditure,and breast weight of the wind group were 53.8%(P<0.01),49.8%(P<0.01),and 97.0%(P<0.01)higher than those in the no wind group,respectively.b.Female Swiss mice and pups like to live in a windless environment at 21?,but at 32.5?,they prefer to live in a windy environment.The mammary glands acinus in the32.5? group were smaller than those in the 21? group,and they were mostly oval.The mammary glands acinus in the wind group were more filled and larger than those in the control group,and they are all round in shape.The results suggested: 1)High temperature inhibits the surface heat dissipation of non-reproductive mice and reduces energy intake.Wind increases energy intake by increasing body surface heat dissipation in nonreproductive mice.But wind had no significant effect on the energy expenditure of non-reproductive mice.2)At high temperature,wind can improve the heat dissipation capacity of lactating mice,increase the energy intake and reproductive performance of lactating mice.And the expression of lactation regulatory protein in lactating mice was significantly downregulated,especially the regulatory factors in breast tissue,such as Stat5 a and Stat5 b.3)At high temperature,female mice prefer to feed their pups in a windy environment.High temperature can inhibit the lactation ability of the mammary glands,and wind can improve the lactation ability of the mammary glands.