Factors influencing milk production of local goats in the Comarca Lagunera, México

J A Maldonado-Jáquez^1,2, H Salinas-González², G Torres-Hernández¹, C M Becerril-Pérez¹ and P Díaz-Rivera³

¹ Colegio de Postgraduados, Campus Montecillo. Programa de Ganadería. Km 36.5 Carretera México-Texcoco. C P 56230 Montecillo, México
glatohe@colpos.mx
² Centro de Investigación Regional Norte-Centro. Instituto Nacional de Investigaciones Forestales Agrícolas y Pecuarias.
Blvd. José Santos Valdez # 1200 Pte., Col. Centro. CP27440, Matamoros, Coahuila, México
³ Colegio de Postgraduados, Campus Veracruz. Km 88.5 Carretera Federal Xalapa-Veracruz. CCP 91700. Manlio Fabio Altamirano, Veracruz, México

Abstract

Factors influencing milk production (MP) of local goats in 14 flocks of 5 communities of the Comarca Lagunera, México, were evaluated. Management of goats was under extensive system conditions. MP was measured monthly by hand milking during four years. Twelve thousand ninety seven observations from 2229 lactations of 1125 local goats from 1 to 4 (or more) kiddings were analyzed. Independent variables in the statistical model were community, flock nested within community, production year, number of kidding, kidding season, number of milk measurements as a covariate, plus dam as a random effect. The statistical analysis was performed with the MIXED procedure of the SAS package. The overall mean for MP was 938±6 g/animal/day. Community (p≤0.01), flock within community (p≤0.01), production year (p≤0.01), and number of kidding (p≤0.01) influenced MP. Also, an effect (p=0.008) of the number of milk measurements (as a covariate) on MP was found, showing that for each extra milk measurement MP increased 27±3 g. Further research on additional factors influencing MP of local goats in the Comarca Lagunera is needed in order to keep this region positioned as the leading producer of goat milk in México.

Key words: community, flock, kidding number, kidding season, producers

Introduction

For many years goats have been adapted to adverse conditions, such as weather, aridity, topography, among others (Cantú 2008), and have the ability to survive and reproduce for long periods of time (Soma et al 2012). In rural areas they have the role of meeting essential needs for food, occupation, and settlement of human populations (Bedotti 2008). Mexico is the second largest producer of goats in the American continent (Galina and Pineda 2010) and 18th in milk production worldwide (FAOSTAT 2013).

In Mexico, goats have found their main habitat in the arid and semi-arid northern territory under extensive conditions (Galina and Pineda, 2010) where 64% of the goats are concentrated and they feed mainly shrub flora. These regions are characterized by low socioeconomic status, large water shortages and prolonged droughts (Baraza et al 2008). In Mexico, goat flocks are mostly made up of animals that farmers call "criollos" (Zavala 1993; Merlos-Brito et al 2008), a term that is now accepted and used in México as "locales" (Montaldo et al 2010). In his review of the criollo goat in Latin America, Mellado (1997) refers to its origin and some of its productive characteristics.

The Comarca Lagunera (states of Coahuila and Durango) ranks as the main producing region of goat's milk in México. However, available information on goat milk production is very scarce. This is largely attributed to producers because they do not keep production records, are not organized for the production, processing and marketing of milk (Maldonado-Jáquez et al 2014), they lack a lot of information and technical assistance (Salinas et al 2011; Escareño et al 2012), have a low technological level and, on the other hand, goats have a marked seasonality in milk production (Maldonado-Jáquez et al 2015). The aim of this study was to evaluate factors that influence milk production (MP) of local goats managed in extensive conditions in the Comarca Lagunera.

Materials and methods

The study was carried out in 14 goat production units (flocks) located in 5 communities, 4 in the Viesca Municipality and 1 in the Municipality of Matamoros, Coahuila, within the Comarca Lagunera. This region is located between coordinates 24° 22' and 26° 23' North Latitude and 102° 22' and 104° 47' West Longitude and at 1100 m above sea level. The climate, according to Köppen classification, modified by García (1988), corresponds to BWhw, which is characterized by being very dry or desert, semi-warm with cool winter. The average annual rainfall is 240 mm and average annual temperature in the shade is 25 °C, with ranges from -1 °C in winter to 44 °C in summer.

Flock management is typical for the extensive system, where the sanitary management is traditionally limited to vaccination of a campaign against brucellosis and a deworming against external parasites (either injected or immersed) each time the animals show signs of parasitism, which on average is every 6 months. Goats graze in the day and by the evening-night they are enclosed in pens to rest, where they have access only to blocks of mineral salts. The main diet consists of native plants of the region, such as grasses (Sporobolus spp. and Muhlenbergia spp.), shrubs such as huizache (Acacia spp.), mezquite ( Prosopis spp.) and gobernadora (Larrea tridentata) and sometimes manilla or agave inflorescence (Agave spp.). In the rainy season the diet of goats is largely based on herbaceous species, among which are the nightshade (Solanum elaeagnifolium), mallow Sphaeralcea angustifolia), and tumbleweed (Salsola kali). Occasionally goats may consume agricultural wastes such as those of melon ( Cucumis melo), watermelon (Citrillus lanatus), forage oats (Avena sativa) and sorghum (Sorghum halepense).

With the participation of goat producers, milk production data were collected from local goats over a period of 36 months for 4 years (June 2012 - May 2015. The goats were hand-milked once a day every month with schedules established between 04:00 and 07:00 hours. For this, kids were separated from their dams approximately 12 hs prior to milking and during milking they were not allowed to suckle their dams, instead, they suckled nurse dams to allow all available milk to be completely removed from their dams. Farmers did not apply restricted suckling of the kids. Once the milking procedure ended, kids went out with their dams to grazing. Neither the dams nor the kids were supplemented on the days of milking. The monthly production control was performed by measuring the MP with a commercial scale Torrey^® with capacity of 10 kg ± 1 g. Initial database included 3397 lactations with 13899 monthly production records from 1749 local goats from 1 to 4 (or more) kiddings. Individual and/or lactation records with less than 3 observations, corresponding to 13% of the total of the initial database, were discarded. The edited (final) database included 12097 observations pertaining to 2229 lactations of 1125 goats. It should me mentioned that in this study it was not possible to estimate milk production per goat for the entire lactation. This was because producers that participated in the study began to measure milk production either 4-5 days after kidding, or even up to one month after kidding because of lack of both time and required help; thus a true estimate of the average lactation length was not known. Therefore, only milk production goat ^-1 day^-1 could be estimated under these work conditions.

In order to make a diagnosis, data were initially analyzed with a fixed effects model using the GLM procedure of a statistical package (SAS 2002). All factors considered were included in this model. Once the behavior of the data was observed, the random effect of the animal was subsequently included in the model, in order to obtain better solutions for the fixed effects, because the database was unbalanced. The final statistical analysis was carried out under a mixed model with the MIXED procedure of the statistical package SAS. Where appropriate, differences between means were tested with the Tukey test. The general structure of the model was:

Y_ijklmnop=µ + ID_i + C_j + F _k(j) + PY_l + KN_m + KS_n + β (X_ijklmnop - _X^-_ijklmnop) + E_ijklmnop

where: Y_ijklmnop: average milk production/goat/day/lactation, µ: constant that characterizes the population, ID_i: random effect of the i-th animal (i=1,2,3, …, 1125), C_j: fixed effect of the j-th community (j=1, 2, 3, 4, 5), F_k(j): fixed effect of the k-th flock (producer) nested in the j-th community (k=1, 2, 3,…,14), PY_l: fixed effect of the l-th production year (l=1, 2. 3. 4), KN_m: fixed effect of the m-th kidding number (n = 1, 2, 3, 4 +), KS_n: fixed effect of the n-th kidding season (m = 1, 2), X: effect of the covariate number of measurements (weights) of MP during lactation, β: coefficient of regression associated to this covariate, E_ijklmnop: random error. All random components were assumed to be normally distributed with zero mean and common variance.

Results

Except for kidding season, the other factors included in the statistical model influenced (p≤0.01) milk production. Overall average MP was 938±6 g goat^-1 d^-1.

Table 1 shows the least-squares means for MP by community, where the greatest MP average was found in the Irlanda community. However, the most marked differences were those found at flock level within community. Goats with 4 (or more) kiddings produced the greatest amount of milk d^-1. The lowest MP were from goats with 1 and 2 kiddings, respectively (Table 1). There were no differences (p≥0.05) in MP between goats of 1 and 2 kiddings. Table 1 shows the least-squares means and standard errors for MP per production year and kidding season. The lowest MP was found in 2012, while the greatest in the period 2013-2015. There were no differences (p≥0.05) between the years of the period 2013-2015.

An effect (p=0.008) of the covariate milk measurement number (weighing) during lactation was found, noting that for each extra milk measurement MP increased 27±3 g.

Discussion

Mellado (1997) indicated that in desert areas, with annual precipitations between 200 and 400 mm the MP of criollo goats in lactation of 6-7 months during the rainy season is from 100 to 140 kg (470-550, 660-770 ml d^-1, for 6 and 7 months respectively), but in lactations during winter and spring (dry season) MP is only 141 to 386 ml d^-1). In goats from the Comarca Lagunera, Salinas et al (1990) reported a MP average of 554 g d^-1, a value substantially equal to that obtained by Vélez et al (2015), which was 550 g d^-1 in criollo goats with extensive management, also in a community of the Comarca Lagunera. Mellado et al (1991) found a higher average (770 g d^-1) in northern Mexico, utilizing native goats crossed with others of improved breeds. Sánchez de la Rosa et al (2006) obtained an average MP of 856 g d^-1 from criollo goats in the state of Guerrero, México, a dry tropic region. The high variability between these averages could be attributed to factors such as goat genotype, feeding, climate, lactation length, management, among others.

There was a high within-flock variability for MP, with a range between 613 and 1171 g. Such variability could be mainly attributed to goat genotype, feeding, and management; that is, specific factors that characterize flocks of goat producers in this region.

The higher MP goat^-1 day^-1 estimated in this study can be mainly attributed to extraordinary rainfalls during the study years, as will be explained when discussing the year effect. Both lower MP averages have been reported with different local types of goats (Makun et al 2008; Martínez-Rojero et al 2013), and higher (Bughio et al 2001; Pattanayak 2013) than the average obtained in this study. These differences can be attributed to factors such as goat genotype, feed level, production system, and selection effect, among others.

Salinas et al (2011) pointed out that the general goat management between producers in this region is similar. However, by means of frequent visits and field observations during the study some differences were observed between producers such as: grazing length, vegetation species, duration of milking, differences attributed to individual milkers, etc, that certainly need to be evaluated. In general, one should consider that the productive performance of goats, especially for MP, is due to both genetic and environmental factors (Paz et al 2007). On the other hand, although some authors (Mellado et al 2006) had pointed out that MP during lactation is not associated with any type of forage in particular, Stan et al (2011) indicated that the type of forage directly affects both quantity and quality of milk. Other authors (Mburu et al 2014) have indicated that poor dietary practices affect MP of goats, and it is known that MP is one of the variables that is initially affected by any nutritional or environmental change (NRC 1981).

The kidding number effect on MP has been extensively studied; Peña-Blanco et al (1999) and Selvaggi and Dario (2015) found that Florida and first kidding Jonica goats produced about 20% less milk than multiparous goats. Similarly, Carnicella et al (2008) mentioned that the lowest amount of milk was obtained from first kidding goats and then gradually increased until the fourth kidding in Alpine goats in Croatia and Slovenia and Maltese in Italy, respectively. This effect is explained because as kidding number increases the goat matures physiologically and, consequently, its mammary gland increases in size, reason why it is able to store more milk in its cistern, which finally translates into an increased MP (Salama et al 2004; Assan 2015).

Year is an erratic and low prediction variable (Salvador and Martínez 2007), therefore, with a great influence on the quantity and quality of milk. In this study, there were rainfalls of 255, 469, and 305 mm in 2013, 2014 and 2015 respectively (CONAGUA 2015), which, as already mentioned, they were higher values than the historical average of the region, which is 225 mm (SEMARNAT 2015), and also higher than the average found in 2012, which was 108 mm (CONAGUA 2015). This suggests a higher availability of forage on the rangeland those years. This hypothesis is reinforced by the studies of Lauenroth and Sala (1992) and Bai et al (2008), who indicated that an increase in the average annual precipitation increases both production and abundance of forage species, and in this region 94% of goats based feeding only on pasture resource (Maldonado-Jáquez et al 2014).

There were no differences (p≥0.14) in MP between kidding seasons 1 and 2, although in this study it was observed that the distribution of kiddings in kidding season 2 (November to February) was 70%, whereas in kidding season 1 (June and July) was 30%, a result in agreement with Salinas and Martínez (1988). The irregular distribution between both kidding seasons was evidenced by the higher standard error in the mean of MP in kidding season 1 (Table1). This irregularity in the distribution of kiddings is because goats in this region go into sexual rest from March to August due to a photoperiod effect (Delgadillo et al 2003; Delgadillo et al 2015). Moreover, kidding season 2 coincides with the season where forage is in a state of senescence (Delgadillo et al 2015), reason why goats are under poor nutrition in this season (Escareño et al 2012). Thus, at the beginning of the year there is a delay in MP due to an insufficient amount of food in the rangeland (Salinas and Martínez 1988).

Studies in goats regarding the effect of the number of measurements on milk production analyzed as a covariate were not found in the literature. In buffaloes from Colombia and Cuba, Hurtado-Lugo et al (2005) and Mitat et al (2008), respectively, found that the number of milk measurements influenced (p<0.01) the estimation of MP per day of control. This indicates that producers should be aware of the importance of this factor in the evaluation of MP, which is a very important criterion for estimating the genetic quality of their goats.

Conclusion

• Community, flock within community, kidding number and production year were factors that greatly influenced milk production of local goats in the Comarca Lagunera.
  
  
• These results emphasize the importance of conducting further research on factors influencing various productive indexes of the extensive production system of these goats, since this genetic group is the one that for many years has been adapted to the difficult desert conditions of the Comarca Lagunera and that, in spite of it, keeps this region positioned as the leading producer of goat milk in Mexico.

Acknowledgments

We thank the Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias (INIFAP) for partial funding support through “fondos fiscales” and to CONACYT for the scholarship granted to the first author to carry out Master of Science studies.

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Received 7 October 2017; Accepted 4 April 2018; Published 3 July 2018

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