Kits Performance of Hyla, Hycole and its Reciprocal Crossbreds in Tropical Climates

Bram Brahmantiyo1*, Henny Nuraini2, Komarudin3, Nurul Pratiwi1 and

Ferdy Saputra1

1Research Center for Animal Husbandry, Research Organization for Agriculture and Food, National Research and Innovation Agency of The Republic of Indonesia (BRIN), Cibinong Sciences Center, Cibinong, Bogor 16915, West Java, Indonesia

2Department of Animal Production and Technology, Faculty of Animal Science, IPB University, Jalan Agatis, Kampus IPB Dramaga, Bogor 16680, West Java, Indonesia

3Balai Pengujian Standardisasi Instrumen Unggas dan Aneka Ternak, Ministry of Agriculture, Jalan Veteran III Ciawi, Bogor 16720, West Java, Indonesia

ABSTRACT

Fast growth can reduce production costs so that the price of rabbit meat is cheaper. In order to achieve rapid growth, crossbreeding programs are widely used to produce broiler rabbits. Evaluation of the growth of kits is needed to see their genetic potential in tropical climates. Body weights of kits from Hyla (n = 63), Hycole (n = 68), Hyla x Hycole (n = 72), and Hycole x Hyla (n = 66) rabbits were collected weekly. Weekly body weights were analysed using a general linear model and least square means computed with SAS 9.4. Hycole x Hyla birth weights (62.52 ± 1.55) were greater than birth weights from the other breed groups. However, Hyla had the highest body weights at one and five weeks of age. We also found Hyla to have better litter size (9.65 ± 0.25) than the other breed groups. The superior reproductive and growth performance of Hyla indicated that this breed is the most suitable of the four breed groups under Indonesian tropical climate conditions.

Article Information

Received 13 August 2022

Revised 20 July 2023

Accepted 03 August 2023

Available online 17 November 2023

(early access)

Published 07 April 2025

Authors’ Contribution

BB designed the study. FS interpreted the data. BB, HN, K, NP and FS drafted and revised the manuscript, and made improvements in it.

Key words

Hyla, Hycole, Kit performance, Rabbit, Tropical climate

DOI: https://dx.doi.org/10.17582/journal.pjz/20220813130825

* Corresponding author: brahmantiyo@gmail.com

0030-9923/2025/0002-0995 $ 9.00/00

Copyright 2025 by the authors. Licensee Zoological Society of Pakistan.

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

Rabbits are livestock that are easy to reproduce and have a large litter size. Rabbits are still widely used as pets, ornamental breeds that are widely kept in Indonesia are the Angora, Holland Lop, and the Netherland Dwarf. Several countries in the world have developed fast-growing meat-type rabbits, namely New Zealand White, Flemish Giant, Hyla, and Hycole which are widely grown in Indonesia. However, rabbit meat in Indonesia is not as popular as beef, chicken, goat and lamb. The food processing industry produces rabbit meat only on a small scale. However, the use of rabbit meat as a source of animal protein is very promising. The high potential of litter size in rabbits must be followed by rapid growth in the breeding program. Rapid growth can reduce production costs. Furthermore, rabbit meat is a more affordable option than beef. In order to achieve fast and efficient growth, crossbreeding programs are widely used to produce broiler rabbits.

The Indonesian Research Institute for Animal Production imported Hycole from France 2012, and Hyla from China in 2013. Brahmantiyo et al. (2017) indicated that Hycole is a rabbit that has the advantages of high growth and reproduction. Wang et al. (2016) stated that Hyla rabbits have a high percentage of intramuscular fat compared to Champagne and Tianfu Black, but Tianfu Black had higher commercial carcass percentage. High temperature or heat stress can complicate the maintenance of rabbits (Cervera et al., 1997). Indonesia is a country with a tropical climate where temperatures range from 21 oC to 34 oC, and humidity ranges from 60% to 95%. According to Marai et al. (2001), rabbits are in a comfort zone ranging from 18 to 21 oC. The aim of breeding programs is to increase productivity and lower production costs through fast growth and feeding efficiency. Thus, the objective of this study was to determine the growth performance of kits from Hyla, Hycole, and their crossbreds under tropical climate conditions.

Materials and methods

Body weights of kits from Hyla (n = 63), Hycole (n = 68), Hyla x Hycole (n = 72), and Hycole x Hyla (n = 66) rabbits were collected weekly. Rabbits were kept in individual wire cages. The cage height from the floor was 100 cm. Each cage was equipped with a diet trough made from pottery (15 cm x 12 cm x 60 cm), and drinking water was provided in the nipple made from metal. The size of the doe cage was 60 cm x 75 cm x 40 cm, while the size of the buck cage was 75 cm x 45 cm x 40 cm. The nesting cage size was 40 cm x 30 cm x 25 cm. Sawdust was used as flooring. Dams would lose their hair and use it as a nest for their kits. Nesting cages were cleaned when the kits were four to five weeks old and prepared for subsequent kits. The kits were weaned at five weeks and kept in a 45 cm x 75 cm x 45 cm wooden cage. The diet used in this study contained 18% crude protein, 2500 kcal/kg metabolic energy, and 14% crude fibre. The diet was made in the form of a pellet. Pellets were delivered in the morning and evening, and drinking water supplied ad libitum. This experiment was approved by the Animal Ethics Committee of the Indonesian Agency for Agricultural Research and Development, Ministry of Agriculture (Registration Number: Balitbangtan/Balitnak/Rd/01/2021).

The weekly body weight data were analyzed using a general linear model and least square means with SAS 9.4. The mathematical model was as follows:

Yijk = μ + Bi + Lj + eijk

where Yijk is the weekly body weight of the kth kit from the ith breed group, and jth litter size; μ is the overall mean; Bi is the effect of the ith breed group; Lj is the effect of the jth litter size; and eijk is the random residual.

Heterosis was calculated using the formula:

Heterosis was calcu

Where H% was the relative heterosis expressed as a percentage, Pc was the mean phenotypic value of the two crossbred groups, and Pp was the mean phenotypic value of the two purebred groups.

Growth curves were analysed using the Gompertz model with SAS 9.4. The following growth curve equations based on the Gompertz model were used to estimate the growth rate of the four breed groups:

Y=4889.17 exp (-exp (-0.14) (Age-10.13)) for Hycole ...(1)

Y=4052.47 exp (-exp (-0.13) (Age-10.02)) for Hycole x Hyla ..(2)

Y = 5008.96 exp (-exp (-0.14) (Age-10.33)) for Hyla ...(3)

Y=2157 exp (-exp (-0.19) (Age-6.24)) for Hyla x Hycole ...(4)

where Y is individual rabbit weekly weight in g; exp is base of natural logarithms; age is age of an individual rabbit.

Results and discussion 

Hyla (9.65 ± 0.25) had larger birth litter sizes than Hycole (8.29 ± 0.24) (Table I). The matings of Hyla males to Hycole female yielded smaller litter sizes at birth than matings of Hycole males to Hyla females. These birth litter sizes were smaller than those of Chinchilla rabbits (12.00±2.21) and comparable to those of New Zealand rabbits (8.33±2.13) in Nigeria (Egena et al., 2012). The birth litter size of Hyla in this study was lower than that reported for first generation Hyla rabbits in Tunisia (8.50; Hamouda et al., 1990). Conversely, the birth litter size of Hycole in this study was within the range of values for this breed estimated in Poland (8 to 10; Ludwiczak et al., 2020). Tůma et al. (2010) stated that season had a negative correlation with litter size at weaning (7.08±0.19) in Hyplus rabbits. Bhatt et al. (2010) found that grey rabbits had the largest litter sizes at birth, birth weights, and litter sizes at weaning in winter than in summer and the rainy season. Furthermore, Nuriyasa et al. (2012) reported that rabbits kept in cages in an underground shelter with a low temperature-humidity index (THI) showed better physiological responses. Unsuitable THI conditions as well as low doe milk yields can cause pre-weaning mortality (Rashwan and Marai, 2010). Therefore, improved nutrition and management of does is necessary for successful rabbit farming (Zapletal et al., 2021).

 

Table I. Least square means of weekly body weight (kits) and litter size of doe based on breed.

Traits	Breed (Means ± SEM) (g)
	Hycole	Hycole x Hyla	Hyla	Hyla x Hycole
BW0	60.36 ± 1.52a	62.52 ± 1.55a	60.87 ± 56.39a	56.39 ± 1.48b
BW1	145.27 ± 4.51b	141.42 ± 4.35b	162.66 ± 5.19a	143.94 ± 4.18b
BW2	244.22 ± 8.91a	212.83 ± 8.59b	261.93 ± 10.25a	223.67 ± 8.26b
BW3	369.546 ± 15.30a	320.00 ± 14.75b	393.15 ± 17.62a	362.14 ± 14.19a
BW4	536.39 ± 15.98a	476.61 ± 15.41b	568.36 ± 18.41a	496.51 ± 14.82b
BW5	747.23 ± 23.53a	642.05 ± 22.68b	797.98 ± 27.09a	679.91 ± 21.81b
LS	8.29 ± 0.24b	8.37 ± 0.24b	9.65 ± 0.25a	7.76 ± 0.23b

 

Description BW0-5: body weight of 0-5 weeks; LS, litter size at birth.

 

Table II. Least square means of weekly body weight based on litter size at birth.

Traits	Litter size at birth
	2	4	6	7	8	9	10	11	12
BW0	80.00± 8.17a	76.61 ± 2.98a	67.45 ± 2.98a	56.69 ± 1.43b	61.83 ± 1.60b	64.37 ± 2.80a	59.22 ± 1.92b	55.11 ± 1.51b	53.51 ± 3.85b
BW1	204.38± 20.57a	168.41 ± 7.65a	142.11 ± 7.70b	150.22 ± 3.88b	162.17 ± 4.19b	122.46 ± 7.127b	115.55 ± 4.96b	123.68 ± 3.88b	145.90 ± 9.87b
BW2	384.99± 40.61a	303.89 ± 15.11a	169.09 ± 15.20b	232.54 ± 7.67b	237.69 ± 8.29b	221.80 ± 14.058b	161.45 ± 9.80b	180.17 ± 7.67b	229.37 ± 19.48b
BW3	724.06± 69.77a	441.37 ± 25.97b	322.71 ± 26.12b	313.97 ± 13.17b	349.73 ± 14.24b	304.53 ± 24.15b	234.83 ± 16.84b	273.62 ± 13.18b	286.05 ± 33.47b
BW4	1102.95± 72.87a	631.76 ± 27.12b	487.11 ± 27.28b	468.24 ± 13.76b	478.52 ± 14.87b	443.33 ± 25.22b	323.60 ± 17.59b	358.03 ± 13.76b	381.65 ± 34.96b
BW5	1491.37± 107.27a	871.28 ± 39.93b	660.55 ± 40.16b	629.77 ± 20.25b	649.19 ± 21.89b	618.18 ± 37.13b	475.16 ± 25.90b	498.33 ± 20.26b	557.33 ± 51.46b

 

Table III. Heterosis effect of traits in crossbred.

Traits	Crossbred
	Hyla x Hycole	Hycole x Hyla
BW0	-7.124	2.203
BW1	-3.787	-4.816
BW2	-5.816	-7.487
BW3	0.748	-12.906
BW4	-1.211	-9.992
BW5	-4.859	-13.117
LS	-11.763	-5.140

 

Description BW0-5: body weight of 0-5 weeks; LS: litter size at birth.

 

Di Meo et al. (2004) obtained individual rabbit birth weights of 60 to 70 g, however they indicated that they could range from 35 to 40 g to 80 to 90 g. Individual birth weights decreased as litter size increased (Table II). Birth weight of kits was found to be determined by doe body weight and age (Szendrő et al., 2019). The birth weight of Hyla rabbits in this study was within the range obtained by Chrysostome et al. (2011), however it was greater than those of Fauve de Bourgogne (47.19 g), Chinchilla (50.95 g), British Spot (47.99 g), and New Zealand White rabbits (45.51 g) (Jimoh and Ewuola, 2017).

Hyla had better growth performance than Hycole and their crossbreds. In addition, kits coming from a litter of size 2 tended to have larger body weights than kits from other litter sizes. The negative values of heterosis for weekly body weights and litter size indicated that the performance of crossbred groups was not as good as that of the purebred groups (Table III). Conversely, Brahmantiyo et al. (2021) found that doe reproduction and kit growth performance from New Zealand White and Hyla crossbreds was superior to purebreds under tropical conditions. Conversely, Hyla had better performance than Hycole, and the two crossbred groups in this study. Therefore, it is necessary to evaluate crossbreeding programs to produce rabbits that are well adapted and productive under Indonesian tropical conditions.

 

Table IV. The estimation of inflection poin of body weight and age of Hycole, Hyla, and it’s reciprocal.

Breed	Inflection point of body weight (g)	Inflection point of age (week)	R2
Hycole	256.91	2.5	0.75
Hycole x Hyla	240.98	2.5	0.71
Hyla	266.89	2.5	0.73
Hyla x Hycole	262.72	2.5	0.73

 

The inflection points for kit bodyweight and age in Hyla, Hycole, and reciprocal crossbred groups is shown in Table IV. The coefficient of determination of the inflection points ranged from 0.71 for Hycole x Hyla kits to 0.75 for Hycole kits. Kits grew faster after 2.5 weeks of age indicating that 2.5 weeks is a crucial time for their growth.

Gompertz model was confirmed as better growth curve for body weight of birds than that of Logistic model due to lower of root mean square error (RMSE) value (Putra et al., 2021). Inflection point of body weight in reciprocal was lower than Hycole and Hyla. Despite, all breed had similar of inflection point of age value (approximately 2,5 weeks) and inflection point of body weight in reciprocal Hycole x Hyla (240.98) and Hyla x Hycole (262.72) was lower than Hyla (266.89). Szendrő et al. (2019) stated that the maternal effect has an important role for kits at 3 weeks of age because they only consume milk. Therefore, the selection of does that has good maternal effects, one of which is milk production is needed to get the ideal body weight in kits at 2.5 weeks of age. Hyla has a greater inflection point of body weight than other rabbits. This could be an indicator that Hyla has a better maternal effect.

Conclusions

Kits from smaller litter sizes tended to have higher body weights than kits from larger litter sizes in the four breed groups of this study. Hyla rabbits had higher weekly body weights than Hycole and reciprocal crossbred rabbits. The best rabbit breeding programs aim to produce large litters and kits that grow rapidly. Hyla had the largest litter sizes and weekly body weights indicating that this rabbit breed is the most suitable of the four breed groups under Indonesian tropical climate conditions.

Acknowledgement

Authors would like to thank all the breeding staff, Laurentius Hardi Prasetyo, and Yono Cahyanto Raharjo.

Funding

The authors thank Indonesian Research Institute for Animal Production for the funding. This work was supported by the Ministry of Agriculture of the Republic of Indonesia through the Agency of Agricultural Research and Development (No. 4585.SDA/051/B/B1/APBN/2021.)

Ethical statement and project approval

This experiment was approved by the Animal Ethics Committee of the Indonesian Agency for Agricultural Research and Development, Ministry of Agriculture.

Statement of conflict of interest

The authors have declared no conflict of interest.

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