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Cuban Journal of Agricultural Science

Print version ISSN 0864-0408On-line version ISSN 2079-3480

Cuban J. Agric. Sci. vol.54 no.1 Mayabeque Jan.-Mar. 2020  Epub Mar 01, 2020

 

GENETICS

Performance of the fertility and prolificacy at birth in the current populations of three rabbit breeds in Artemisa, Cuba

D. García1  * 
http://orcid.org/0000-0001-9155-1040

Yoleisy García1 

Raquel. E. Ponce de León1 

Odalys Ginorio2 

1Instituto de Ciencia Animal, Apartado Postal 24, San José de las Lajas, Mayabeque, Cuba

2Empresa de Ganado Menor, Unidad Empresarial de Base “Alquízar” Municipio Alquízar, Artemisa, Cuba

Abstract

In order to study the performance of fertility and prolificacy traits at birth (total born and live born), a total of 14 659 records of mating and 8 296 kindlings of the current rabbit populations of California, Chinchilla and New Zealand breeds were used between 2014 and 2017, belonging to a genetic unit. A mixed generalized linear model was used, which considered the fixed effects of breed, month, year and the interactions breed x month and breed x year, in addition to the random effect of the reproducers in its different mating or kindlings. It was found that all sources of variation considered in the model influenced on the analyzed traits, except the interaction of breed per month of mating in fertility, so the studied traits vary depending on the interaction between breeds and environmental conditions (month and year). The highest fertility occurred in the mating of April, March, May and July, and the lowest in January and August. California showed stability over time and remained the most fertile, when there were differences between breeds in the same year. There were divergences between breeds in the kindlings of February, June, September, October, November and December, with superiority of New Zealand, while Chinchilla had a worse performance for 70 % of those months. New Zealand remained the best in three years, with more than 5.6 total born and live born. This breed is ratified as the most promising for reproductive indicators that determine the rabbit productivity.

Key words: reproduction; breeds; rabbits; productivity

Introduction

At present, the management capacities of animal genetic resources need to be strengthened, due to their importance for the feeding and agriculture. One of the actions included in this management is the characterization of breeds to establish programs of improvement, effective and sustainable, to take advantage of the available biological diversity and to ensure that livestock populations adapt to their productive environments and to the needs of society (FAO 2019). Specifically in those species of economic interest, such as the rabbit, the characterization of the reproductive traits that guarantee the perpetuity of the species, and those that are most affected by the climatic variations, is of vital importance.

In Cuba, the populations with control and sustained genetic improvement, belonging to the genetic units from the western region have been characterized by Ponce de León et al. (2002, 2003a b). Due to the outbreaks of the Rabbit Viral Hemorrhagic Disease (Dihigo and Ponce de León, 2006), these populations have been considerably reduced (Dihigo and Ponce de León, 2006), which caused the repopulation of the genetic units with animals of different breeds and origins, without undergoing a process of genetic improvement. Given these conditions, it is necessary to characterize the performance of the fertility and prolificacy traits at birth of the current rabbit populations from California, Chinchilla and New Zealand breeds in a genetic unit of western Cuba, as a starting point for their genetic improvement.

Materials and Methods

A total of 14659 records of mating and 8296 kindlings were used, from California, Chinchilla and New Zealand breeds, during the period 2014-2017. The animals, reared in a farm, belonged to a rabbit genetic unit from Empresa de Ganado Menor (EGAME), located in Alquízar municipality, Artemisa province.

Each breed was in a building and the animals were housed in individual, commercial-type cages. The mating occurred between animals of the same breed through a rotational system with four family lines. An average ratio of 8 to 10 females per male was established, with the purpose of keeping the inbreeding levels low.

The animals received a mixed diet, consisting of commercial feed and forages. The feed was offered as meal (17-18 % of crude protein, 10-10.8 MJ of digestible energy and 7-10 % of crude fiber). Sometimes it was mixed with wheat bran and accounted for approximately 70-80 % of the requirement, depending on the category (Lebas et al. 1996). It is a bulky food, feasible to pawing, that did not fulfill the requirements of the animal. When there was availability, grass forage was supplied, mainly lignified king grass (Cenchrus purpureus) and protein plants, such as tricantera (Trichantera gigantea) and titonia (Tithonia diversifolia). Additionally, water ad libitum.

A semi-intensive rearing system was applied, with mating at 11d after kindlings and weaning at 35 d of age. The heating detection was based on the coloration of the vulva and was carried out at the earliest hours by transferring the female to the cage of the corresponding male. The palpations were carried out after 11 d post-mating to verify pregnancy. At 28 days of proven gestation, wooden nests, with hay or shavings, were placed in the reproducers cages until 15 d after kindlings. The nests were daily checked to detect the kindling and ensure hygiene.

On the day of kindling detection, the living and dead animals were counted, the sum was considered as the number of total born. The litters were not regrouped at birth so as not to affect the genealogy of the animals.

With the total records of mating (14 659) fertility (FERT) was studied as an all or nothing character (FERT = 0 when the mating was not effective, it did not give birth and FERT = 1 when the reproducer was pregnant and gave birth). The variables total born (TB) and live born (LB) were analyzed based on the information of the litters born in each kindling (8 296). As total born, the amount of young rabbits in the litter (alive + dead) was considered at the time of kindling. The live born (LB) were considered as the number of young rabbits at kindling.

The statistical analysis was performed with Statistical Analysis System (SAS) software, version 9.3 (2013). With the help of the PROC MEANS of this package, the general mean descriptive statistics, coefficient of variation and standard deviation for all studied traits were determined. For the characterization of these traits, a mixed generalized linear model was applied using the PROCGLIMMIX. A binomial distribution and logit link function was used for fertility. For total born and live born, the gamma distribution and its corresponding linking function, the log was applied.

For fertility, the model considered the genetic effect of the breed (California, Chinchilla and New Zealand), the environmental effects of the twelve months and four years of mating, in addition to the interactions breed per month and breed per mating year. It also considered the random effect of the reproducer on each reproductive event. For the number of total born and live born, the model was the same, but the month or mating year was replaced by the month or kindling year. In the random effect, the reproducer was considered in each kindling. To determine the differences between means, the Tukey multiple means comparison test, modified by Kramer (Kramer1956), was used.

Results and Discussion

The descriptive statisticians of the studied traits are showed in table 1. The general means obtained are lower than those reported by Ponce de León et al. (2002, 2003a b) in the national populations of these breeds, reared with restricted feeding and grasses forage. These populations were in the range of 65-71 % fertility, 5.8-6 total born and 5-5.6 live born.

Table 1 Descriptive statisticians of the pre-weaning traits 

Traits General mean Coefficient of variation , % Standard deviation
Fertility, % 58.3 84.5 0.5
Total born 5.3 41.2 2.2
Live born 5.1 46.3 2.4

Chino and Zamora (2009), in a study developed in Spain with these three breeds, reported for these traits means higher than those of this study. These authors reported values between 68 and 75 % for fertility, while prolificacy at birth reached 8.2 young rabbits.

Baltazar et al. (2014), in Mexico, and Gallego (2016), in Colombia, when using a feed that fulfill the nutritional requirements of the species, obtained averages of more than 7.7 total born and 7.4 live born. These results are also higher to those of this research, because it did not fulfill the nutritional requirements.

The fact that the commercial food provided to the populations under study did not fulfill the nutritional requirements of the rabbit implies the deterioration of the reproductive performance of these animals (de Blas and Wiseman 2010 and Naturil et al. 2016).It may also have influenced the characteristics of the studied populations, although these are the same breeds. Kontsiotis et al. (2014) and Asemota et al. (2017) have related factors such as those mentioned with the decrease in reproductive performance in the species.

Table 2 shows a summary of the analysis of variance, for fertility and prolificacy traits at birth. It was verified that all sources of variation (genetic and non-genetic) considered in the model influenced on the analyzed traits (P˂0.001), with the exception of the interaction of breed per mating month for fertility. This reaffirms the influence of the effects of breed, month and year on these reproductive traits, since the results coincide with the causes of variation referred to in studies carried out with the same breeds by Ponce de León et al. (2002, 2003a) in the western national and imported populations (Ponce de León et al. 2003b). They also correspond to those of Vaillant (2012) in the eastern region of the country, and those of Baltazar et al. (2014) in Mexico.

Table 2 Analysis of variance, F value and probability for fertility, total born and live born. 

Sources of variation gl Fertility, % No.Born
Total Live
F value P value F value P value F value P value
Breed 2 17.98 ˂.0001 76.48 ˂.0001 56.93 ˂.0001
Mating month/kindling 11 8.46 ˂.0001 13.72 ˂.0001 12.91 ˂.0001
Mating year/kindling 3 9.33 ˂.0001 33.49 ˂.0001 23.62 ˂.0001
Breed x month of mating/kindling 22 1.31 0.1475 2.48 0.0008 2.22 0.0008
Breed x year of mating/kindling 6 3.15 0.0044 11.23 ˂0.0001 11.35 ˂.0001

Fertility. The effect of the breed on this indicator is shown in figure 1. Out of the breeds in this unit, California was the one that achieved the highest fertility average with respect to the other two, which had approximately 5% fewer effective mating. Ponce de León et al. (2003a b) found another performance pattern for these breeds. The New Zealand, in both cases, was the breed with the highest fertility rate, followed by California and Chinchilla. It should be highlighted that, in both cases, the fertility referred by these authors was superior to what was found in this study.

ab Means with non coinciding superscripts in the same column differ at P < 0.05 (Kramer 1956).

Figure 1 Effect of breed on fertility 

The performance of this indicator in the different mating months studied is shown in figure 2. The highest fertility (66.4 %) occurred when the mating were made in April, although the one obtained for March, May and July does not differ from the highest average, with values higher than 61 %. The lowest fertility occurred when the mating occurred in January and August, with a difference of 13 percentage units compared to April. In the rest of the months of the year, fertility did not differ from that reported in January and August.

abcde Means with non coinciding superscripts differ at P < 0.05 (Kramer 1956).

Figure 2 Effect of mating month on fertility  

The low fertility found in eight of the twelve mating months studied is due to deficiencies in reproductive management and constant variations in diet. Ponce de León et al. (2003b) reported for fertility values of 56.7 and 60.8 % in the bimesters May-June and July-August, respectively. Two of the mating months with the lowest fertility (June and August) identified in this study are among the bimesters referred by these authors, who attribute the low fertility to the worsening of the nutritional level, in terms of quality, composition and requirements, as well as the inadequate reproductive management and health problems. Asemota et al. (2017) relate the low fertility to the influence of high temperatures.

Although in this study July and August correspond to the rainy season, the unit where these populations were reared did not have forage areas to replace the fiber deficit in the diet. Therefore, the forage supplied did not satisfy the volumes necessary for the animal mass of the unit.

The breed per mating year interaction was analyzed based on the differences between breeds in the same year (figure 3). These differences were found only in the years 2014 and 2015, in which California maintained its merit order, as the breed of highest percent of pregnant females with respect to covers, while Chinchilla and New Zealand varied their pattern. In 2014, Chinchilla had the same fertility as California, and it was New Zealand with the lowest average. While in 2015, Chinchilla obtained nine percentage units less than California, while New Zealand did not differ from these two.

ab Means with non coinciding superscripts in the same year differ at P<0.05 (Kramer 1956).

Figure 3 Effect of the interaction breed per mating year on fertility. 

In 2016 and 2017, there were no differences between breeds, which may be due to an improvement in the quality of the received feeding and in the reproductive management. It may also be due to the incorporation of replacement animals, selected by a behavioral test performed at the reproducers stock, and to the stability of the unit's technical personnel.

In general, for this trait, advantages were identified in the California breed, due to its stability over time (years of kindlings) and superiority in performance with respect to the other two, despite being inferior in relation to the potential of the species.

Prolificacy at birth. The three breeds generally showed a similar performance for total born and live born in the different months of kindlings, due to the high correlation between these traits (Mantovani et al. 2008). When analyzing the differences between breeds in the same month of kindlings, these differences were showed, when kindlings occurred in February, June, September, October, November and December (figures 4 and 5).

ab Means with non coinciding superscripts in the same month differ at P<0.05 (Kramer 1956).

Figure 4 Effect of the interaction breed per month of kindling on total born. 

ab Means with non coinciding superscripts in the same month differ at P<0.05 (Kramer 1956).

Figure 5 Breed per month of kindling interaction for live born  

In the months in which there were differences between breeds, New Zealand always showed superiority, with more than 5.6 total born young rabbits and 5.3 live born. In February, September and October, California had the same performance as New Zealand and Chinchilla. The latter showed the lowest values, with almost a young rabbit born less than the New Zealand. In June, California, with 4.6 total born and live born, moved to last place in merit order, moving away from Chinchilla and New Zealand in more than one young rabbit born.

In the kindling of the last two months of the year, the Chinchilla and California breeds did not differ among themselves, but from New Zealand, which exceeded 5.5 total born (figure 4). For live born, the performance described above was only in December, since in November Chinchilla had the same performance as New Zealand, both different from California, with live litters of 4.7 (figure 5). The Chinchilla, in 70 % of the six months in which there were differences between breeds, was the worst performance for these prolificacy indicators.

The differences found in the performance of these two indicators (total born and live born) for the three breeds in the months of kindlings February, June, September, October, November and December, can be mainly attributed to the effect of technical staff on reproductive management, in addition to the instability in the persons that worked in the unit during the study time. To these conditions were added the changes in the formulation of the concentrated food, which did not allow an adaptation period by the animals to the new diet, and had restrictions and problems in the feeding, as well as the decrease of the reproductive performance of these breeds. According to Naturil et al. (2016), prolificacy at born can reach 33.3 %.

The breeds in interaction with the four years of kindlings, for total born and live born, revealed differences between them for the conditions existing in the same year (figures 6 and 7). In 2014, feeding and management conditions affected the three breeds equally, while for both traits these differences were found in the last three years of kindlings (2015, 2016 and 2017).

ab Means with non coinciding superscripts in the same year differ at P<0.05 (Kramer 1956).

Figure 6 Effect of the interaction breed per year of kindling for total born  

ab Means with non coinciding superscripts in the same year differ at P < 0.05 (Kramer 1956).

Figure 7 Breed per year of kindling interaction for live born. 

New Zealand was the first in merit order in those three years, with more than 5.6 total born and live born. The California and Chinchilla, without differences between them, had the worst averages, with litters of less than 5.4 young rabbits born (figure 5 and 6). Only in 2015, for live born were differences between the performance of California and Chinchilla, being the latter the one with the lowest means (figure 7).

The differences between breeds in the last three years for these two prolificacy traits were contrary to that found for fertility, where the differences occurred in the first two years of kindling. This is due to that the poor reproductive management of animals was affected in fertility, an aspect that was subsequently improved with technical advice and staff training. For prolificacy at born, divergences between breeds may be due to the way in which each of breeds faced constant changes in feeding, differences in work with the replacement of the reproducers stock and the appearance of health problems.

When making a comprehensive evaluation of the obtained results in this study, it can be concluded that the performance of fertility and prolificacy at birth in the current populations of three rabbit breeds also vary depending on the interactions between breeds and environmental conditions (month and year). Out of the three breeds, California was the one that showed some potential advantage for fertility, showing a more stable performance over time (month and year). For those of prolificacy at born, reproductive indicators that determine the productivity of the species, New Zealand is ratified. As in previous racial populations, the need to stabilize and improve the nutritional and management environment to increase production levels is evident.

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Received: June 06, 2019; Accepted: February 03, 2020

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