Effect of dietary protein supply on the reproductive performance of crossbred rabbits

Nguyen Thi Kim Dong*, Nguyen Van Thu* and T R Preston** 

* Cantho University, Cantho City, Vietnam

ntkdong@ctu.edu.vn

** UTA, TOSOLY, AA #48, Socorro, Santander, Columbia

** preston@lrrd.org

Abstract 

An experiment was conducted in the experimental farm of Cantho University to evaluate the effects of different dietary protein levels on the reproductive performance of crossbred rabbits in three parities. The experiment had a complete randomized design, with four treatments, three replicates and one female rabbit per experimental unit. The diets included para grass, supplemented with different amounts of water spinach (Ipomoea aquatica) leaves and concentrate in order to provide 28 (28CP), 31 (31CP), 34 (34CP) and 37 (37CP) g crude protein (CP) per rabbit per day, respectively. In three litters the results indicate that intakes of dry matter (DM) and CP significantly increased (p<0.03) with increasing the levels of CP in the diet, with the highest values for the 37CP diet.

Higher litter sizes at birth were found for rabbits fed higher CP levels, with the highest on the 37CP diet (P<0.05), and litter size at weaning had a similar tendency. Mean weights at birth were only slightly different among treatments, and mean weights at weaning in litters 1 and 2 were highest on the 34CP and 37CP diets. Weight gains in pregnancy were highest on 37CP (P<0.05) and milk yields increased (P<0.01) with increasing CP level in the diet, with the highest values on 37CP. A comparison between the three parities showed that litter size at birth and weaning and milk yield were better in the second litter, and significantly higher weight gains in pregnancy were found in the first litter.

It was concluded that a daily intake of 37g CP per day resulted in optimum reproductive performance of female crossbred rabbits.

Key words: birth weight, crossbred rabbits, dietary protein, litter size, milk yield, para grass, water spinach, weaning weight

Introduction

Rabbit meat production has increased considerably in Vietnam recent years in order to meet the increasing demand for human food from animal products, and to replace poultry meat, which has declined in importance as a result of Avian Influenza. Rabbit meat is also increasingly popular due to the fact that it is very nutritious, lean and low in fat and cholesterol. However, breeding rabbit stocks are still limited, so it is not possible for farmers to buy weaned rabbits for their production systems. Moreover, most studies have focused on feeding and diet digestibility of growing rabbits rather than of reproductive does. Improving the nutrition of breeding females is of primary importance for increasing the productivity of domestic rabbit farming. In particular determining the optimal level of protein supply for breeding rabbits is the key to making the best of the rabbit's production potential and has a direct relationship to the income of the rabbit keeper (Ren et al 2004). According to Lebas et al (1986) does require diets with levels of protein ranging from 17 to 18% in pregnancy and lactation.

Several kinds of locally available protein-rich forages are found in the Mekong Delta, and water spinach (Ipomoea aquatica) leaves (WSL) have been shown to be a very good source of plant protein for rabbits (Dong 2006), and provides adequate levels of protein and other nutrients essential for rabbits. Para grass is a good fibre source for rabbits and contains around 30% crude fibre (CF) (Trang 2006). The hypothesis of this study is that reproductive performance of crossbred does fed basal diets of para grass will be improved as the level of protein supplied is increased through supplementation with WSL and concentrate pellets. The objectives of the study are therefore to evaluate the effect of different levels of protein on the reproductive performance of crossbred rabbit does.

Materials and methods 

Animals and experimental design

The trial was carried out at the Experimental farm of Cantho University in Cantho City. Twelve crossbred rabbit does at five months of age were arranged in a complete randomized design, with 4 treatments and 3 replications. One animal was housed individually per wire mesh and wood cage, as an experimental unit. The dietary treatments included para grass ad libitum supplemented with 300g fresh WSL and with concentrate levels of 29, 46, 63 and 80g to give in total 28, 31, 34 and 37g CP per doe per day, corresponding with the 29CP, 31CP, 34CP and 37CP treatments, respectively. 

Feeds, feeding and management

Para grass was collected daily in the areas surrounding Cantho University. Water spinach leaves were bought from farmers who plant and sell WS stems for human consumption, with the WSL available as a by-product. Concentrate was bought at a local feed store on one occasion during the experiment. The animals were fed three times a day, at 8:00, 15:00 and 19:00h. Para grass was offered ad libitum, while 300g WSL per day was given to all does. Concentrate pellets were offered at levels of 29, 46, 63 and 80g/ doe/ day to give a total of crude protein supply of 28, 31, 34 and 37g per female per day. The WSL and pellets were adjusted weekly by increasing allowances by 5, 10 and 15% in the second, third and fourth week of pregnancy, respectively. During the lactation period allowances were increased by 10% in the first week, 30% in the second and third week, and 40% in the fourth week. All animals had access to fresh water at all times.

The does were kept individually in separate cages, and only one buck was used for mating. The breeding service was done at two weeks after birth. The new-born animals were weaned at the 30th day. Refusals and spillage were collected and weighed daily in the morning to calculate feed intake. Weights of rabbits at birth and weaning, and daily milk yields were measured. The does were weighed weekly from mating to parturition and their weight gains calculated during pregnancy. Before entering experiment all does were vaccinated to prevent some diseases, especially rabbit Hemorrhagic diarrhea and also parasite diseases.

Measurements

Reproduction criteria were recorded in 3 litters. Feeds and refusals were taken for analyses of DM, OM, CP, NDF and ADF following the procedure of AOAC (1990) and Van Soest et al (1991). The measurement taken including: daily feed and nutrient intakes for each litter, litter size at birth and weaning, weight gain of does in pregnant period and daily milk yield recorded by weighing the kids before and after suckling of kids.

Statistical analysis

The data of experiments were analyzed by analysis of variance using the ANOVA of General linear model of Minitab Reference Manual Release 13.20 (Minitab2000) to compare the differences among the treatments. For the comparison of the reproduction criteria between the litters the paired T test of Minitab Reference Manual was also used. 

Results and discussion 

Feed characteristics

Characteristics of feeds used in the trial are presented in Table 1.

The para grass (PG) contained higher DM, but lower CP concentrations as compared to water spinach leaves (WSL). The concentrate pellets had higher DM and moderate CP contents compared to other feeds. Supplementation of both WSL and pellets to para grass diets increased the protein content in the diets. The CP content of the WSL used in our experiment was similar to values reported by Phimmasan et al (2004) and Samkol et al (2006).

Feed and nutrient utilization and reproduction

Feed and nutrient intakes and performance of the does for the first, second and third litter are shown in Table 2, 3 and 4.

Daily DM intakes of the does increased with daily CP intakes, with the significantly highest value (P< 0.01) recorded for animals given the highest amount of CP (37CP) (Table 2, 3 and 4). These results are similar to those reported by Nicodemus et al (1999), which ranged from 134 to 174g per day. For all three litters, litter size at birth significantly improved with increasing CP intake (P=0.02), while the mean rabbit weight at birth was not significantly different among treatments, probably because of the negative relationship between mean litter size and mean birth weight. The number of live rabbits at birth and at weaning in all three litters significantly increased with increasing amounts of CP supplied, with the highest number on the 37CP diet. The mean litter size at birth was similar to the values cited by Arrington and Kelly (1976) (6-8 kids/litter), Mai (2005) (3-8 kids/litter) and Lebas et al (1986) (7-9 kids/litter). However, the results reported by Ren et al (2004), working with Rex rabbits, showed lower litter size at weaning and survival rate (from 3.0-6.1 rabbit and from 63.3 to 76.1%, respectively) than values obtained in the present study.

Weight gains, duration of pregnancy and milk yields of the does are shown in Table 5. 

Duration of pregnancy was similar between treatments for all three litters. Daily weight gain of the does during pregnancy was influenced by the supply of CP, and was lowest on the 28CP diet and highest on the 37CP diet, the difference being significant in the first and the third litters (P=0.02 and P=0.04, respectively). Daily milk production  was strongly affected by protein intake, and was lowest for the animals fed 28g CP (mean for 3 litters of 67.7 g /day), then significantly improved with increasing CP amount in the diet, and the highest milk yield (P<0.01) was for the 37CP diet (mean for 3 litters of 101 g /day). Daily milk yield recorded in our study is considerably higher than the values of 45.2-53.5g reported by Ren et al (2004).

A comparison of the reproductive criteria of the does among the three litters is presented in Table 6.

There was no significant difference in litter size at birth between the three litters, while number of weaned rabbits was significantly higher in the second litter than in the third. Mean weight at birth and at weaning was not statistically different among litters (P>0.05). Does had the highest daily weight gain during pregnancy in the first litter as they were immature, and would not have attained mature body size and weight. Daily milk yield was significantly higher in the second litter than in the other litters (P<0.05).

Figure 1 and Figure 2 illustrate that in the three litters the increasing protein supply had positive effects on the litter size at birth (R²=0.95) and daily milk yield of does (R²=0.93).

There was also a close relationship between milk production and litter weight of the kits at weaning (Figure 3) (R²= 0.92).

Thu (2004) reported that the CP requirement for breeding does was from 35-40g per day for the improved breeds, which is in agreement with the findings of the present study for crossbreed does.      

Conclusions and implications  

It is concluded that:

• Water spinach leaf is a good source of protein, with high acceptability and palatability for breeding rabbit does.

  
  

• Does given a diet that supplied 37g crude protein per day had better reproductive performance and economic returns than those given 28-34 g CP per day.

  
  

• Studies of a wider range of crude protein supply for crossbred breeding does than in the present study should be carried out.   

Acknowledgements 

Financial support of this work from SIDA-SAREC is gratefully acknowledged. The authors would like to thank the Department of Animal Science, Faculty of Agriculture and Applied Biology of Cantho University for infrastructure support..

References 

AOAC 1990 Official methods of analysis (15^th edition). Association of Offical Analytical Chemists. Washington, DC. Volume 1: 69-90

Arrington L R and Kelly K C 1976 Domestic rabbit biology and production. A University of Florida handbook

Dong N T K 2006 Study of biological characteristics and chemical composition of different water spinach varieties (Ipomoea aquatica) in the Mekong delta. Unpublished data

Lebas F, Coudert P, Rouvier R and Rochambeau H D 1986 The rabbit husbandry, health and production. FAO, Italy http://www.fao.org/docrep/x5082e/x5082e00.htm

Mai H T X 2005 Rabbit feeding and management. Agricultural Publishing House, Ho Chi Minh City, Vietnam

Minitab 2000 Minitab reference manual release 13.20. Minitab Inc.

Nicodemus N, Carabano R, Gacia J, Mendez J and de Blas C 1999 Performance response of lactating and growing rabbits to dietary lignin content. Animal Feed Science and Technology 80:43-54

Phimmasan H, Kongvongxay S, Chhay Ty and Preston T R 2004 Water spinach (Ipomoea aquatica) and Stylo 184 (Stylosanthes guianensis CIAT 184) as basal diets for growing rabbits. Livestock Research for Rural Development. Volume 16, Article #34. Retrieved, from http://www.lrrd.org/lrrd16/5/hong16034.htm

Ren  K L, Li Y P, Ren J L, He D C and Liang Q Z  2004 Study of dietary energy and protein levels for reproducing Rex rabbits from weaning to marketing. Procedings of the 8th Congress of the World Rabbit Science Association. Puebla City, México, September 2004. pp. 959-963

Samkol P, Preston T R and Ly J 2006 Effect of increasing offer level of water spinach (Ipomoea aquatica) on intake, growth and digestibility coefficients of rabbits. Livestock Research for Rural Development. Volume 18, Article # 25. Retrieved March 7, 2006, from http://www.lrrd.org/lrrd18/2/samk18025.htm

Thu N V 2004  Rabbit Husbandry. Faculty of Agriculture and Applied Biology, Cantho University Publication

Trang L N H 2006 Effect of sweet potato and water spinach as protein sources on the meat performance and digestibility of crossbred rabbits. Graduate Thesis, Faculty of Agriculture and Applied Biology, Cantho University

Van Soest P J, Robertson J B and Lewis B A 1991 Symposium: Carbohydrate methodology, metabolism and nutritional implications in dairy cattle: methods for dietary fiber, and non-starch polysaccharides in relation to animal nutrition. Journal of Dairy Science 74: 3583-3597 http://jds.fass.org/cgi/reprint/74/10/3583.pdf

Received 2 November 2006; Accepted 23 July 2008; Published 4 September 2008

Go to top