Effect of the gestation and lactation on fiber diameter and its variability in Peruvian alpacas

Highlights

• Lactation reduced fiber diameter in 1.2 µm in Huacaya and 1 µm in Suri.

• Physiological states have to be fitted in models for genetic evaluation.

• Age, color and year importantly influenced fiber performance.

• Year influence on fiber was only recently attributable to genetics.

Abstract

A study was conducted to know the influence of the pregnancy and lactation states on the fiber performance in alpacas at Pacomarca experimental farm in the Peruvian highlands. Records obtained from the regular performance recording software of the farm were used, gathering 8648 records of 1541 females and 366 males of Huacaya ecotype, and 2410 records of 374 females and 132 males of Suri ecotype, registered from 2001 to 2015 and belonging to animals of three or more years. A mixed linear model for fiber diameter, standard deviation and coefficient of variation fitted the physiological state with five categories (milking, pregnant, milking and pregnant, open females and males) as an effect jointly with others such as year of recording, age from 3 to 9 or more years old and coat color. Huacaya and Suri ecotypes were independently analyzed. All the effects included in the model appeared as highly significant, being the paired differences less significant in Suri because of the lower number of records. Lactation physiological state appeared as an important effect affecting fiber performance, explaining a difference of 1.2 and 1.0 µm of differences in respectively Huacaya and Suri pregnant females, while pregnancy appeared with a much less relevant influence. Other factors greatly influenced the fiber diameter. Thus, age had a very important effect increasing 3.71 µm from 3 to 9 years of age in huacaya and 4.52 µm en Suri. A difference of 3.09 µm in huacaya and 5.93 µm in Suri was found between dark and white coat colored alpacas. These results recommend modifying the genetic evaluation model by fitting the physiological state of females to increase the accuracy of the breeding values used to select animals in the breeding scheme of the farm.

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.