Effect of the gestation and lactation on fiber diameter and its variability in Peruvian alpacas
Introduction
International market of natural fibers based on natural fiber is highly competitive for the textile industry. Pacomarca experimental farm was created to face this, developing a successful breeding program while addressing profuse research (Gutiérrez et al., 2009, 2011, 2014, Cervantes et al., 2010, Pérez-Cabal et al., 2010, Paredes et al., 2014, Cruz et al., 2015, 2016). The main objective selection in alpacas is the reduction in fiber diameter to produce fine fiber. Genetic improvement should also be encompassed with improvement in other areas such as nutrition, health, reproduction and management as part of an integrated business management strategy (McGregor et al., 2013(aa, McGregor et al., 2013(bb, McGregor et al., 2016). The estimated heritabilities for fiber traits in alpacas have been moderate to high, so the responses to artificial selection have been relevant for these traits (Cruz et al., 2015, Gutiérrez et al., 2014, Gutiérrez et al., 2009). Efficient selection has to be based in top-rated animals according to reliable breeding values for the desired traits, and the reliabilities depend on the amount of information provided by both each individual and its parents. In addition the fitted model for evaluation of the animals would have to include all effects that have influence on the traits (Gutiérrez, 2010). The current statistical model used for genetic evaluation in Pacomarca experimental farm includes, among other effects, the sex, although this has not ever seemed to be highly relevant in the fiber diameter and its variability. However, across their life, the females undergo significant changes in weight, body condition, feeding habits and feed requirements according to pregnancy and lactation periods.
The female alpaca starts reproduction at two years of age, reaching three years usually with a younger animal on its care. From this age onwards a female can be clearly identified under periods of gestation and lactation. A female becoming pregnant has usually a gestation of about 342 days of length, not coming back open until the next breeding season. After calving, the baby will suckle about five or six months (Cruz et al., 2015), representing an overlapping of gestation and lactation in which the female mobilizes the nutrient reserves according to their physiological needs, which may affect fiber performance (low fiber diameter and variability). Then, two very different stages can be defined within pregnancy period. The starting half of the gestation period with increase in the levels of anabolic hormones, and a consequent increase of blood volume, increase in the cardiac output in turn, also an increase in the nutrient reserves, fat and liver glycogen and appetite, and also increasing the food intake. The rest of the pregnancy carries an increase in catabolic hormones, leading to the mobilization of fat reserves and nutrients, decreasing the hepatic glycogen and increasing the metabolism, even in the absence of food intake. Similarly to pregnancy, the energy expenditure is sensitively increased during lactation, resulting in mobilization of energetic reserves to turn them into components of milk. Liesegang et al. (2006) reported mobilizations of the total bone mineral content occur at the end of gestation and beginnings of lactation in goats and sheep.
Metabolic adaptation has been found important for fiber production during pregnancy in sheep when raised in intensive system (Duehlmeier et al., 2011). Likewise the nutrition influences the milk production and the formation of fetal exoskeleton during the gestation, increasing metabolic mobilization of some components, especially the calcium (Liesegang et al., 2007). Also animals under gestation and lactation are more susceptible to diseases, especially parasites that were detrimental in milk production and production of fiber (González-Garduño et al., 2014). Nutritional effects on alpacas and merino sheep have also been reported on fiber yields (McGregor, 2002) and goats (McGregor et al., 2013(aa, McGregor et al., 2013(bb).
Routine annual estimation of genetic parameters and breeding values prediction are currently being carried out independently for the two defined ecotypes in Pacomarca. The model used to perform such analyses includes the month-year of sampling, the coat color with three levels (white, light fawn and dark) and the age (linear and quadratic covariate) as effects (Cervantes et al., 2010, Cruz et al., 2015, 2016; Gutiérrez et al., 2009, 2011). However, physiological status of the female concerning gestation and lactation can importantly influence on the fiber features, and could be interesting to take part of the model. Quantifying gestation and lactation influence seems to be needed. Thus, this research aimed to study the effect of gestation and lactation on fiber diameter, standard deviations and coefficient of variation of the fiber diameter to evaluate their inclusion in the models used for the prediction of breeding values. As a secondary objective, influence of color, year and age on fiber diameter and its variability was also addressed.
Section snippets
Material and methods
The data were collected between 2001 and 2015, in the Pacomarca experimental farm, and correspond to 1907 (1541 females and 366 males) Huacaya ecotype individuals and 506 (374 females and 132 males) Suri ecotype animals, three or more years old. Alpaca females are suitable for reproduction at two years of age, but they only can become lactating or sufficiently advanced pregnant from three years old. Therefore, animals younger than three years were ignored in these analyses because they are much
Results
Table 2 shows the significance of the different effects fitted in the model on fiber traits, as well as the estimated repeatabilities of the traits for both Huacaya and Suri ecotypes. All main effects were highly significant except for CV in Suri ecotype in which only the year effect become significant. Physiological state by age interaction was always significant, but interactions involving coat color were not always significant. Repeatabilities were between 0.45 and 0.66 being particularly
Discussion
Mean fiber diameter was generally found much higher than in previous works for this population (see for instance Cruz et al. (2016) for the last values) because only animals older than three years were considered in this analysis in order to avoid the influence of the extreme thinness of younger animals unable to be under pregnant and lactation status.
The results showed that there was an important influence of the physiological state effect of pregnancy and lactation on the fiber traits in
Conclusion
The physiological state of the females had an important effect on the fiber performance, non-lactating females having the largest fiber diameter and pregnant lactating females the thinnest. Methodology has been developed in order to adjust the influence of the physiological state of the animal but it has been proven here not completely correct it. The relevant differences found in this study among physiological states, mainly lactation, suggests that these states should have to be accounted in
Conflict of interest
There is no conflict of interest for this paper.
Acknowledgment
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
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