Influence of non-genetic factors on growth and reproductive traits of sheep Santa Inês in extensive systems

E L Aguirre Riofrio, J B S Ferraz and E C Mattos

Grupo de Melhoramento Animal e Biotecnologia, Faculdade de Zootecnia e Engenharia de Alimentos da Universidade de São Paulo, Pirassununga, SP, Brasil.
leninaguirrer@usp.br

Abstract

The objective of this study was to investigate the influence of some non-genetic factors on growth and reproductive performance of Santa Ines sheep, raised in different regions of Brazil. Records of 13.186 animals belonging to 33 farmers from 11 states of Brazil were analyzed. The database was kept and maintained using Microsoft Visual FoxPro 9.0. The following reproductive characteristics were analyzed: age at first lambing, lambing interval (CI), prolificacy, female productivity; besides the following growth traits were analyzed: weights at birth, 60 days, 180 days and 270 days of age. The non- genetic effects like sex, year (2003-2014), season (dry and rainy), herd, region, type of parturition (single or twins) and maternal age were included in the evaluation.

The average age at first lambing was 22 ± 1.5 months, suffering influence (P <0.05) of herd and region. The lambing interval was 363 ± 160 days and was significantly influenced by year, season, type of lambing, herd, region and ewe’s age. The average of prolificacy was of 1.36 lambs/birth, being lower in primiparous ewes (1.2 ± 0.04) than in ewes with two or more parities (1.4 ± 0.03) and it was influenced by the herd, region and season, while ewe productivity at an average age of 87.8±32.8 months, in the entire productive life was 3.2±0.5 lambs/ewe. Birth weight and adjusted weights at 60, 180 and 270 days in this population had averages of 3.64 ± 0.8, 14.6 ± 5, 31.7 ± 10.7 and 38.5 ± 13.7 kg, respectively. Birth weight was significantly influenced by sex, ewe's age, type of lambing, herd, region and year of birth. The other weight traits were influenced by sex, type of lambing, herd and region. It was conclude that non-genetic factors notoriously affect the productive and reproductive performance of Santa Ines ewes, therefore, they should be included in genetic analysis models and to take technical and administrative decisions for better performance in extensive systems of those animals.

Key words: Brazil, environment, extensive management, pasture

Introduction

In Brazil the traditional setting of sheep breeding was the Northern and Northeastern regions, however in the last decade the number of herds increased greater in the Southeastern and Midwestern regions. The sheep herd size in Brazil is close to 17 million (FAOSTAT 2016). Under that scenario it is important to study the Santa Ines sheep, a hair sheep breed, which is currently the most numerous in Brazil (Silva et al 2011, Luis Vaz et al 2009). DNA studies have helped to identify its probable origin, recognizing the strong influence of Bergamacia and Morada Nova breeds (Paiva et al 2005, Pedrosa et al 2010).

Both growth and the reproductive traits are important in the determination of economic efficiency of any production system, that is why the farmer and/or technician search throught selection the best animals that can transmit these characteristics to their progeny. However, without the right environment the genetic component is hidden and it is not expressed and precisely the characteristics of growth, fertilization and lactation are the most susceptible to environmental influences (Pereira 2012).

So, animal-environment interaction should be considered as a key element when seeking greater efficiency in any livestock system, moreover in the tropical area, because the different responses of the animal to edaphoclimatic condition of each region is crucial in the success of animal production. Then the importance of considering the material already adapted to such environment as in the case of Santa Ines sheep but the zootechnical information about prolificacy (Boucinhas et al 2006, Pinheiro 2004), lambing interval and daily weight gain (Oliveira et al 2014), birth weight and at different ages (Malhado et al 2008, Pinheiro 2004, Sousa et al 1999), are all made under controlled environmental conditions. So, the aim of this study was to investigate the influence of some non-genetic factors on productive and reproductive performance of Santa Ines sheep, handled extensively in different regions of Brazil, it will allow us to have guidelines and practical recommendations in the management of this animal.

Materials and Methods

The database used in this research belonged to the Associação Sergipana dos Criadores de Caprinos e Ovinos, ASCCO (Sergipe State Association of Goat and Sheep Breeders), used for the ASCCO/USP Program for Animal Genetic Evaluation, led by the Breeding and Biotechnology Group of FZEA-USP, Pirassununga, State of Sao Paulo. The phenotypic records of 13.186 animals were analyzed from 33 breeders in 11 states of Brazil: Sergipe (SE), Bahia (BA), Distrito Federal (DF), Goiás (GO), Espirito Santo (ES), Mato Grosso (MG), Mato Grosso do Sul (MS), Paraná (PR), Rio de Janeiro (RJ) and São Paulo (SP). The database was managed using Microsoft Visual FoxPro 9.0 program. The following reproductive characteristics were analyzed: age at first lambing, lambing interval, prolificacy, and female productivity. The growth traits considered were birth weight, at 60 days, 180 days and 270 days. The non- genetic effects, sex, birth year (2003-2014), birth station: dry (September to March) and rainy (April to August), breeder, region, type of lambing (single and twin) and mother’s age at lambing were considered. A ages ranged from 9 months to 205 months, so mothers were grouped into 16 classes (A≤1, B≤1.5, C≤2, D≤3, E≤4, F≤5, G≤6, H≤7, I≤8, J≤9, K≤10, L≤11, M≤12, N≤13, O≤14, P≥15 years). Several statistical analysis were performed under The R Project for Statistical Computing, an open source software set of programs: ANOVA, correlation, regression.

Results and Discussion

Reproductive traits

The average age at first lambing of 22.0 ± 1.5 months, which is consistent with what was expressed by Silva et al (2011) that has a low precocity and it needs more time to reach maturity, being significantly affected by non-genetic effects breeder and region (Table 1).

According to Balaro et al (2015), Santa Ines sheep has a low reproductive seasonality, with a slightly higher reproductive performance in the rainy season by the increased availability and quality of grass (Figure 1), as the deliveries occurred throughout the year, with a slight higher percentage in the rainy months (April, May, August) than in the dry months.

Figure 1. Percentage of births occurring during different months of the year

The lambing interval (CI) of a selected total of 6282 data, the average was 363 ± 160 days, very large interval and that contradicted what was shown by Oliveira et al. (2014) what stated that the Santa Ines sheep has three lambing every two years. However, Eloy et al. (2011), Mwaanga and Janowsky (2000) and Oliveira et al (2014), indicate that CI extends (linear effect) by the age of weaning, and it is believed that precisely the lack of early weaning in extensive systems causes this long CI, being significantly influenced by several factors such as: year, region (Table 1), breeder. The season has also influenced that trait (Pinheiro. 2004), because the ewes had longer lambing interval (375 days) in the dry season than in the rainy season (364 days). That was expected and due to the higher availability of pasture. Type of parturition also affects that trait, because ewes with single parturition had a CI of 359 days and in multiple parturition it was of 385 days.

Another factor that influenced CI was the ewe's age (Figure 2), because, as ewe’s age increases the CI also increases, being it a progressive behavior until the age of 8 years, after this time the CIs become irregular and with wide variability, when they get to older ages the CIs in some years are shorter, we believe this may happen because the ewe that stays longer in the herd are exactly "the best females", that means those females that did not have reproductive problems.

Figure 2. Effect of ewe’s age on the lambing interval of the Santa Ines sheep (rounded point=mean, vertical lines=SEM)

Prolificacy of Santa Ines sheep was 1.36 ± 0.14 lambs/birth, results similar to those presented by Pinheiro (2004) and Sousa et al. (2003) and lower when compared to those reported by Siqueira and Araujo (1992) in supplemented sheep (1.57 lambs/birth). That trait was affected (P <0.05) by herd, region, season (rainy = 1.24; dry = 1.34) and number of parturitions (primiparous = 1.2; multiparous = 1.4), showing that with better management and food availability (Boucinhas, et al., 2006), better results are achieved. In the productivity of females the average was 87.8 ± 32.8 months for an average of 3.2 ± 0.5 lambs/mother; another date obtained in this research was that 79% of births was simple, double 20.3% and 0.7% triple or quadruple, confirming what was said by Barros et al. (2005), that this breed has a low multiple birth rate.

Growth traits

The weight at birth of Santa Ines sheep after analyzing a database of 11.918 animals was of 3.64 ± 0.84 kg, value and effects similar to those reported by Malhado et al. (2008), Sousa et al. (1999). That trait was affected (P <0.05) by the sex of lambs (males = 3.75 kg; females = 3.55 kg), by the season of birth (rainy = 3.7 kg; dry = 3.6 kg), by the type of parturition (single = 3.85 kg; multiple = 3.33 kg). It was also influenced by herd, region, year and ewe’s age (Figure 3), so that the younger ewes (up to one year old) and older ewes, it calved lighter lambs with a wide variability, while the calved heavier lambs in some ages (13, 15 years old) were just by the phenotypic selection criteria performed by the breeders to leave in the flock the “best ewes”, influence on this trait was considered.

Figure 3. Effect of ewe’s age on the lamb weight at birth of the Santa Ines sheep (rounded point=mean, vertical lines=SEM)

A total of 7.627 weight data adjusted to 60 days records were analyzed, with an average was 14.6 ± 5 kg and a weight gain of 0.175 kg/ day. When weighted at 180 days the adjusted mean weight was 31.7 ± 10.7 kg with a daily gain (60 to 180 days) of 0.143 kg. As concerned to weight at 270 days, data from 3.829 were adjusted and the average was 38.5 ± 13.7 kg, an increase (180 to 270 days) of 0.093 kg weight/day. All those weight gains were similar to the ones reported by Silva et al. (2011) and are higher to those presented by Malhado et al. (2008) that studied crossbred lambs (Santa Ines x Texel). With these measurements of average weight achieved the growth curve was elaborated (Figure 4), it has presented a polynomial tendency of second order with a very reliable R². It has a slight decrease in phase of 60-180 days and we believe this is related to the curve of milk production by the ewes, because 75% of milk production occurs within 8 weeks after birth (Negrão et al. 2001; Pacheco and Quirino. 2008). Probably the gradual decrease of weight gain is due to the maternal effect, because in this management system maybe the weaning is done later causing a reduction in the body condition of the ewe and larger CI.

Figure 4. Growth curve of Santa Ines sheep up to 270 days of age

Table 2 shows that the effect of the season did not influence in the weight after birth, probably because the lactation canceled the same. The factors like sex, type of lambing (Silva et al. 2011; Sousa et al. 1999) affected (P <0.05) in weight development of post-birth lambs, disagreeing with Carneiro et al. (2007) who says that sex does not affect the performance. The effects of breeder that has to do with the handling of the animal, the region and year of birth that has to do with the humidity in a certain place and year, significantly influence these traits.

Another effect that influences it was the ewe's age (Figure 5), because as the ewe's age increases the weights of lambs decrease, presenting this trait an irregular behavior and high variability. We believe it is due a selection process and also for the lifetime curve of sheep (El-Saied et al. 2005), so in these management systems it would not be convenient to have ewes over 8 years of age or have a compensatory measure that would be the supplementation of food for the lambs.

Figure 5. Effect of ewe’s age on the lamb weight at 180 day age in the Santa Ines sheep (rounded point=mean, vertical lines=SEM)

Conclusions

• Non-genetic factors notoriously affect the growth and reproductive performance of Santa Ines sheep, in genetic analysis models, and in making technical and administrative decisions should be included for better performance in the extensive systems of this sheep.

Acknowledgments

Associação Sergipana de Criadores de Caprinos e Ovinos ASCCO and Grupo de Melhoramento Animal e Biotecnologia, FZEA-USP, Pirassununga, that supplied the data set.

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Received 19 March 2016; Accepted 10 June 2016; Published 1 July 2016

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