Study On The Appropriate Energy/protein Ratio Of Lactation Feed For Breeding Pigeons In Different Seasons

Currently,research in the field of nutritional requirements for breeding pigeons in China is in its infancy,and there is limited study on the energy/protein ratio of diets during the lactation period for these pigeons.This greatly limits the production efficiency of the meat pigeon breeding industry.The nutritional needs of breeding pigeons are mainly influenced by physiological stages,feeding patterns,and environmental conditions.In order to clarify the effects of different seasons and feeding patterns on the appropriate energy/protein ratio level during the lactation period for breeding pigeons,this study selected the commonly used European Mimas white pigeons for the investigation of the appropriate energy/protein ratio level during the lactation period for breeding pigeons under the summer"2+4"pattern（one pair of breeding pigeons nursing four squabs）and winter"2+3"pattern（one pair of breeding pigeons nursing three squabs）.This research aimed to lay the foundation for the establishment of standardized feeding for breeding pigeons during the lactation period,and the main research contents are as follows:Part 1 Study on the appropriate energy/protein ratio level of breeding pigeon diets during the lactation period under the summer"2+4"feeding patternIn the present study,a two-factor experiment design was conducted during the summer season on 576 pairs of Mimas white pigeons,aged 12 to 14 months,with similar body weight and reproductive cycles.Factor A was different crude protein levels（15%,16%,17%,18%）,and factor B was different metabolic energy levels（12.6 MJ/kg,12.8MJ/kg,13.0 MJ/kg）.All pigeons were randomly divided into 12 treatment groups,with each pair of breeding pigeons nursing four squabs,and the experimental period was 28days.Through the analysis of breeding pigeon reproductive performance,breeding pigeon plasma biochemistry,squab growth performance,squab slaughter performance,and meat quality,the optimum energy/protein ratio level during the lactation period for breeding pigeons under the high production pattern in summer was determined.The main results are as follows:1.Breeding pigeon production:The ME level of the diet had little effect on breeding pigeon production during the lactation period,while the CP level and energy/protein ratio level significantly affected the growth and reproductive performance of breeding pigeons during the lactation period,with a small impact on egg quality.Among them,breeding pigeons fed with 18%CP had the lowest body weight loss（P<0.01）and the best reproductive performance（P<0.01）during the lactation period.2.Squab growth and development:Both ME and CP levels significantly affected squab growth and slaughter performance,and had a significant interactive effect.Among them,treatment group 11（18%CP 12.8 MJ/kg）had the fastest growth rate for squabs（P<0.01）,with the best carcass quality and organ weight（P<0.05）.This indicates that a energy/protein ratio value of 17.00 kcal/g in the diet can promote the growth and body development of squabs.3.Squab meat quality:Both ME and CP levels significantly affected the meat color,pH,and muscle fiber characteristics of the squab breast muscle,and had a significant interactive effect.Among them,18%CP significantly reduced the meat color（brightness L^*,redness a^*,yellowness b^*）and pH（P<0.01）,while the area and diameter of muscle fibers in the 12.8 MJ/kg group were the smallest（P<0.01）,and the muscle fiber density was the highest（P<0.01）.This indicates that a energy/protein ratio value of 17.00 kcal/g in the diet can greatly improve the quality of squab meat after slaughter.4.Lipid metabolism and oxidative stress in breeding pigeons:As the CP level in the diet increased,the plasma glucose（GLU）and triglyceride（TG）contents in female breeding pigeons decreased significantly（P<0.05）,and the albumin（Alb）content increased significantly（P<0.01）;the total cholesterol（T-CHO）,blood urea nitrogen（BUN）,and malondialdehyde（MDA）contents in the plasma increased and then decreased.Increasing the ME level,on the other hand,reduced the TG and hydrogen peroxide（H₂O₂）contents in the plasma of female pigeons（P<0.05）.5.Regression model prediction:In terms of squab slaughter rate and feed-to-gain ratio,the appropriate energy/protein ratio in summer was 17.94-18.49 kcal/g;in terms of breeding pigeon egg-laying interval and weight recovery,the appropriate energy/protein ratio in summer was 17.00 kcal/g.The results above indicate that the ME level of the diet had little effect on breeding pigeon production during the lactation period in summer,but the CP level significantly affected breeding pigeon production,and there was a significant interaction effect between ME and CP levels.When the energy/protein ratio of the diet was 17.00 kcal/g,treatment group 11（18%CP,12.8 MJ/kg）showed the best reproductive performance for breeding pigeons during the lactation period,the fastest growth for squabs,and better meat quality,which can be promoted and applied as the appropriate energy/protein ratio level during lactation period for breeding pigeons under the summer"2+4"pattern.Part 2 Study on the appropriate energy/protein ratio level of breeding pigeon diets during the lactation period under the winter"2+3"feeding patternDue to the high mortality rate of squabs during the winter high production pattern,reducing the number of squabs nuried by breeding pigeons has been attempted to improve animal welfare in actual production.However,there is limited research on the related nutrient requirements.In order to determine the appropriate energy/protein ratio level of breeding pigeon diets during lactation under the winter"2+3"feeding pattern,a two-factor experiment design was conducted with three CP levels（15%,16.5%,18%）and three ME levels（12.2 MJ/kg,12.4 MJ/kg,12.6 MJ/kg）in the diet.A total of 432 pairs of European Mimas white pigeons were randomly divided into nine treatment groups,with each pair of breeding pigeons nursing three squabs,and the experimental period was 28days.The impact of different energy/protein ratio levels on breeding pigeon reproductive performance,egg quality,squab growth performance,squab slaughter performance,squab intestinal development,and plasma biochemical indicators were comprehensively analyzed.The main results are as follows:1.Breeding pigeon production:The ME level of the diet and CP level had little effect on breeding pigeon body weight,feed intake,and egg quality during the lactation period in winter,but increasing the CP level could significantly improve breeding pigeon reproductive efficiency.Among them,feeding 18%CP significantly increased the egg production rate and hatching rate（P<0.01）,but there was no difference in egg production rate between the entire breeding cycle and 16.5%CP.The interactive effect also had a significant impact,and breeding pigeons in treatment group 9（18%,12.6MJ/kg）had a significantly earlier start of laying（P<0.05）.2.Squab growth and development:ME levels had little effect on winter squab growth performance,slaughter performance,and meat quality,but the CP level significantly affected the growth and body weight gain of squabs during the mid to late lactation period.Among them,treatment group 7（18%CP,12.2 MJ/kg）had the fastest growth rate for squabs（P<0.05）,and the corresponding carcass weight was also the best（P<0.05）.Although there were no significant differences in feed intake and body weight gain among the different treatment groups during the entire experimental period.3.Squab intestinal morphology:Feeding diets with different ME and CP levels affected the intestinal morphology of squabs,and the interactive effect was also significant.Among them,both 16.5%CP and 18%CP significantly increased the thickness of the squab intestinal epithelial cells（P<0.01）.Treatment group 8（18%CP,12.4 MJ/kg）significantly increased the VH/CD in the squab intestine（P<0.01）,but there was no significant difference compared to treatment groups 2,3,and 6.4.Glucose and lipid metabolism,and oxidative stress of breeding pigeons and squabs:Feeding diets with different CP and ME levels had the same impact on plasma biochemical status and production performance of all squabs,but had a smaller effect on female breeding pigeons.Male breeding pigeons showed a certain degree of oxidative stress with the increase of CP level.5.Regression model prediction:For daily squab weight gain and carcass quality,the appropriate energy/protein ratio in winter was 16.23 kcal/g.For breeding pigeon egg-laying production,the appropriate energy/protein ratio was 15.77-16.53 kcal/g.The results indicate that the ME level has little effect on the breeding pigeon production during lactation in winter,while the CP level significantly affects the reproductive performance of breeding pigeons and the growth performance of squabs,and there is a significant interaction between ME and CP levels.Treatment group 7（18%CP,12.2 MJ/kg）has the fastest growth rate for squabs and better reproductive performance of breeding pigeons and can serve as a reference for the energy/protein ratio level of breeding pigeon diets during lactation under the winter"2+3"pattern.In summary,the main conclusions of this study are as follows:The level of dietary ME affects the feed intake of breeding pigeons in the summer"2+4"feeding mode,which in turn affects the carcass development and meat quality of the squabs,while it has little impact on the breeding pigeon production and squab growth and development of squabs in the winter"2+3"feeding mode.The increase of the CP level to 18%significantly improved the breeding efficiency,accelerated the growth and development of the squabs and relieved oxidative stress in the feeding mode in winter and summer.However,the performance advantage was less at 18%CP compared to 16.5%CP after reducing the number of litters in the winter trial compared to the summer high yield model.Therefore,the study recommends a level of 17.00 kcal/g for the breeding pigeon’s energy/protein ratio during lactation in the summer"2+4"model,while in the winter"2+3"model the CP level can be reduced to about 16.5%,and the ME level should not be lower than 12.2 MJ/kg is enough.