How Nutrition Shapes Alpaca Fleece Quality and Fiber Production

By Robert Van Saun, DVM, MS, PhD, DACT, DACVIM (Nutrition)

Introduction

As the camelid industry has matured in many parts of the world outside of South America, the focus of camelid production is appropriately targeting the fiber industry and producing a high-quality product for consumers. Transitioning from a reproduction-oriented to a fiber production industry requires more selective pressure on fleece quality issues and factors influencing fleece yield and quality. The most obvious pathway to improving fleece yield and quality is through genetic selection (Allain and Renieri, 2010). Of interest is how fleece production and quality can be influenced by nutrition. There are conflicting opinions as to whether excess energy, protein, or both can negatively impact fiber micron size leading to lower quality fleece. Fiber diameter is the most important driving factor for the economic value of alpaca fiber (Frank et al., 2006). The objective of this presentation is to review the available information regarding the role of nutrition in alpaca fleece production, much coming from extrapolation of sheep data, and provide further guidance on nutrient requirements in support of fleece production.

What is Fiber or Fibre?

More times than not, when I address the topic of fiber, I am addressing the nutritional perspective of dietary fiber, measured as neutral or acid detergent fiber, and its impact on animal health, intake, and productivity. For this presentation, I am treading into new territory, with much trepidation, in addressing the production of alpaca fiber and the influences of nutritional factors.

Alpacas differ from other South American camelids in that their fiber is composed exclusively of fine hair with no coarse guard hair as in llamas (McGregor, 2006). Fiber is produced from primary and secondary hair follicles in the dermis. Both primary and secondary hair follicles generate the same texture fiber (Antonini, 2010; McGregor, 2006). The ratio of secondary-to-primary (S:P) follicles is considered an important aspect of producing high-quality alpaca fleece. Follicle density averages 17 /mm2 and this declines with age, due to growth, and body condition (Russel, 1994). The S:P ratio averages 5.5:1 in alpacas, and it is suggested that secondary follicles are only formed during fetal development, in contrast to what is reported in sheep (Russel, 1994).

Alpaca fleece production (weight) peaked at 2 and 3 years for Huacaya and Suri breeds, respectively (McGregor, 2006). The fleece weight was more controlled by longitudinal growth rate than fiber diameter, though not all studies are in agreement. Fiber diameter also increases with age, nutrition, and season (summer vs. winter), though no difference due to gender (Frank et al., 2006). Lower growth rates and finer micron size were found in alpaca fleece during July to October in a New Zealand study, which equates to late winter to early spring (Wuliji, 1993). In a feeding trial performed over two different seasons, fiber growth rates were 25% higher in summer compared to winter, and the fiber was coarser in the summer (Newman and Paterson, 1994).

Nutritional Impacts

Alpaca fiber consists essentially of α-keratin proteins in a helical configuration similar to what is found in sheep wool (Antonini, 2010). The mineral component is minimal at 0.42% if alpaca fleece is similar to sheep wool in its composition (Burns et al., 1964). As one might expect, sulfur comprises the largest proportion of minerals in wool (3.21%) due to the high content of sulfur amino acids responsible for cross-linkages (Burns et al., 1964). Nutrition can potentially influence alpaca fleece in two distinct modalities: nutrition of the pregnant female affecting fetal development and nutritional management during fiber production.

Fetal Programming and Follicle Development

Work specific to alpacas regarding the impact of maternal nutrition during critical fetal development periods has not yet been fully elucidated. There are many studies in sheep showing that nutritional deprivation during a critical period of secondary follicle development will impact the number of secondary follicles in the offspring (Edwards, 1999; Faichney and White, 1987; Hutchinson and Mellor, 1983; Kelly et al., 1996). This concept of maternal nutritional status impacting fetal development throughout life is an intensive area of research in production animals, termed epigenetics or fetal programming.

The description of camelid follicular development has suggested that both primary and secondary hair follicles are mature at an earlier age compared to sheep (Antonini, 2010). Secondary follicles seem to be sensitive to maternal nutritional status in contrast to primary follicles. Secondary follicle development in alpacas occurs in utero, and the maximum S:P ratio occurs by 4 months of age (Antonini, 2010; Russel, 1994). Sheep studies have shown that underfed pregnant ewes had lambs with lower fleece weights and lower S:P follicle ratio with higher fiber diameter and variation (Kelly et al., 1996). In an exquisite sheep feeding study, pregnant ewes were fed adequate or underfed throughout or within targeted gestation time windows to determine the impact on follicle development (Hutchinson and Mellor, 1983). Pregnant ewes underfed during 112-135 days of gestation had reduced S:P ratio, suggesting a critical window of fetal development where secondary follicles were highly sensitive to maternal nutrition. Extrapolating this to the length of gestation in an alpaca would suggest that the 7th and 9th months would be this critical period.

Nutritional Status Effects

A limited number of studies with alpacas have been performed to assess nutritional status (energy and protein) on fleece production and quality. Alpaca studies investigating the role of nutrition on fleece production have either restricted energy and protein or supplemented protein. One of the first alpaca studies fed adult male alpacas a diet providing either 0.67 × maintenance or 2.0xmaintenance energy over a 6-week period, then transferred to the opposite dietary treatment (Russel and Redden, 1997). This study assumed an energy requirement for the alpacas as the same of sheep and ultimately fed approximately 96% and 280% of their energy requirement. Both diets provided adequate protein relative to the requirement. Findings of the study suggested nutritional supplementation had a greater effect on fiber longitudinal growth and no impact on fiber diameter or yield. Opposite findings were reported for another study of a similar design. This second study also used 12 male alpacas and fed one of two diets meeting 0.73 or 1.23x maintenance energy. Study results reported that the higher feeding level had higher fleece yield and fiber diameter compared to the restricted diet (Franco F et al., 2009). Both studies have limitations in design and explanation of feeding methods; thus, further studies are required to better address this impact on alpaca fleece production.

With fiber being predominantly composed of protein, there has been interest in determining if either protein or selected amino acid supplementation might impact fleece yield or quality. One study feeding additional protein supplements (soybean meal and rapeseed meal) to weanlings and yearlings on pasture found no effect on fleece yield or quality (Way, 2023). Two other studies supplemented a methionine analog or a protein source that varied in its degradability. Supplementing a heat-treated canola meal protein source in varying amounts had no effect on fleece yield but increased fiber diameter compared to the control (no undegraded protein) diet (Lund et al., 2012). Of concern in this study was the lack of documented nitrogen fractions and the low plasma urea nitrogen concentrations with supplementation. Another study supplemented a methionine analog in attempting to increase sulfur amino acid supply to support fleece production, but no effects were observed (Moore et al., 2013).

With the high sulfur content of wool and fleece due to the presence of cystine residues forming the disulfide bonds, one would think adding sulfur amino acids (methionine, cysteine) would be beneficial to fleece production. In comparing the amino acid composition of mixed rumen microorganisms of sheep and cattle to the amino acid composition of wool, methionine is adequately provided by microbial protein; however, cysteine is very low relative to its content in wool and fleece (NRC, 2007; Sok et al., 2017; Villarroel Leon, 1959). The prioritization of methionine conversion to cysteine relative to fiber production is unknown. It would seem that supplementing the nonessential amino acid cysteine might be a better option given the lack of response to methionine dietary supplementation.

Mineral Effects

As indicated, minerals comprise a very small component of alpaca fleece. One study determined the trace mineral content of alpaca fleece (Holasová et al., 2017). In comparison to the trace mineral content of sheep wool (Szigeti et al., 2020), alpaca fiber seemed to have higher copper, selenium, and nearly double the zinc content of sheep wool. If these observations are repeatable and consistent across more measures, the higher zinc content of alpaca fleece is quite intriguing. Both copper and sulfur are responsible for the cross-linkage of amino acids, giving the crimp quality of fleece and wool. Copper is also contributing to the coloration of the fleece. Zinc most likely plays a role in growth relative to its involvement in RNA and DNA polymerase activities. One might wonder if this higher zinc content of alpaca fleece might contribute to the observed issues of zinc metabolism and lower zinc status of camelids compared to other ruminants.

Nutritional Requirements in Support of Fleece Production

Specific requirements in support of wool production were not fully detailed until the most recent National Research Council publication for small ruminants (NRC, 2007). Van Saun had originally used data from the previous sheep NRC to generate suggested energy and protein requirements in support of camelid fleece production (Van Saun, 2006). In reviewing the new sheep wool production requirements, there is potential for modification of these previous camelid models that were not very descriptive. The energy requirement to support fleece growth was averaged from that value documented for sheep wool and goat cashmere (NRC, 2007). The suggested protein requirement was 1.65 g MP/g wool, and this was converted to a CP equivalent. Of interest was the addition of mineral requirements, namely trace minerals. With the larger zinc content of alpaca fleece, this model adds additional zinc to the previous maintenance equation and uses the sheep absorption coefficient for zinc. More research is needed to further refine and improve upon these early models in helping to better estimate true nutrient requirements of alpacas in support of quality fleece production.

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