| Song Liao Black pig is a local breed bred in Jilin Province,which has the germplasm characteristics of good meat quality,unique flavor and strong fat deposition capacity.While improving the quality of pork,the characteristics of large amount of fat deposition in the middle and late growth period lead to the decrease of feed return and economic benefit.Feed restriction is a common method to reduce feed to gain ratio and improve carcass traits of pigs in the middle and late growth period.It is also an important factor affecting substance metabolism and energy supply and distribution of pigs.Therefore,this experiment takes Songliao black pigs in the middle and late growth period as the research object,and combines carbon and nitrogen metabolism with energy metabolism and growth metabolism with fasting metabolism to study the effects of dietary restriction on growth performance,nutrient digestion,blood biochemical indexes,carbon and nitrogen metabolism and energy metabolism of Songliao black pigs.It provides a theoretical basis for reducing nitrogen and emission reduction,exploring and optimizing Songliao black pig rearing methods and improving economic benefits.Eight healthy Songliao black pigs with similar initial body weight and the same genetic background at 150 days of age were randomly divided into two groups: 100% free feed intake group(Free feeding group)and 70% free feed intake group(Restricted feeding group).Four pigs in each group were placed in an open respiratory calorimetry chamber,respectively.Chapter 1: Effects of Restricted Feeder on Performance,Nutrient Apparent Digestibility and Blood Biochemical Indices of Songliao Black Pig.(1)The performance test results showed that compared with the free feed intake group,the feed/gain of Songliao black pigs in the restricted feeding group was significantly decreased(P<0.01),and the daily gain was significantly decreased(P<0.05).(2)Nutrient apparent digestibility results showed that dietary restriction had no significant effects on the digestibility of dry matter,crude fiber,crude protein and ether fat(P>0.05).(3)The results of blood biochemical indexes showed that the contents of serum urea nitrogen and fatty acid synthase in blood of Songliao black pigs in restricted feeding group were significantly decreased(P<0.05).Chapter 2: Effects of Restricted Feeding on Respiratory Indices,Carbon and Nitrogen Metabolism and Energy Metabolism of Song Liao Black Pigs During Growth Stage.(1)Respiratory data showed that CO2 emissions and O2 consumption of Songliao black pigs in the restricted feeding group were significantly decreased(P<0.05).Respiratory entropy in the restricted feeding group was less than 1.0,and that in the free-feeding group was more than 1.0.(2)The results of carbon metabolism showed that the carbon deposition and fat deposition in restricted feeding group were significantly decreased(P<0.01),while the carbon deposition rate had no significant effect(P < 0 0.05).(3)The results of nitrogen metabolism showed that the proportion of urinary nitrogen to total nitrogen loss was significantly decreased(P<0.05),and the nitrogen deposition rate was significantly increased(P=0.01),but there was no significant difference in protein deposition(P>0.05).(4)The results of energy metabolism showed that the total calories produced in restricted feeding group were significantly decreased,but the proportion of total calories produced to metabolizable energy was significantly increased(P<0.05).The total deposition energy was significantly decreased(P<0.01),but there was no significant difference in protein deposition energy(P BBB 0 0.05).The dietary restriction significantly reduced the amount of carbohydrate and protein oxidative energy supply(P<0.05),and the lipid oxidative energy supply appeared.Chapter 3: Effects of Restricted Feasting on Fasting Metabolism and Energy Supply and Distribution of Song Liao Black Pigs.(1)The results of fasting metabolism showed that feeding restriction at the growth stage had no significant difference on fasting metabolism of experimental pigs(P>0.05).Combined with the growth and metabolism data of experimental pigs and fasting metabolism data,the heat gain consumption of experimental pigs in restricted feeding group was significantly decreased(P<0.05).(2)The results of energy supply and distribution showed that restricted feeding changed the energy distribution in pigs,in which the proportion of urine energy to total energy was significantly decreased(P<0.05),the proportion of fecal energy,heat gain and production net energy had a certain trend of decrease(P BBB 00.05),and the proportion of maintenance net energy had an obvious trend of increase(P=0.07).The proportion of protein deposition energy to total energy was significantly increased(P=0.01).The research shows that Songliao black pigs were in a state of excess nutrition in the free feeding state in the middle and late growth period.At this time,more energy was deposited as fat and the utilization rate of protein deposition was low.Feeder restriction can significantly increase feed return and protein deposition ratio,change nutrient oxidation energy supply ratio and energy distribution in pigs,and effectively reduce carbon and nitrogen emissions and energy waste. |
