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Abanico veterinario

On-line version ISSN 2448-6132Print version ISSN 2007-428X

Abanico vet vol.11  Tepic Jan./Dec. 2021  Epub May 21, 2021 

Original Article

Growth of hair lambs in the semiarid highlands of Zacatecas during winter season

Marco López-Carlos1

Ricardo Fernández-Mier1

Carlos Aréchiga-Flores*  1

Pedro Hernández-Briano1

Carlos Medina-Flores1

Juan Ramírez-Chéquer1

1Unidad Académica de Medicina Veterinaria y Zootecnia, Universidad Autónoma de Zacatecas, Zacatecas, México.


The aim of the study was to assess the effect of sex, birth type, breed, growth retardation, condition and month of birth on weight of birth (WB), and pre- and post-weaning growth of hair lambs that born during winter (n = 416). Male lambs showed better overall growth performance (P <0.05) than female lambs. Single born lambs weighed more (P <0.05) than multiple born lambs at birth and at weaning, although multiple born lambs had greater (P <0.05) average daily gain (ADG) post-weaning. Blackbelly lambs showed little weight (P <0.05) and growth. Dorper-sired lambs had greater (P <0.05) sale weight (SW) and ADG after weaning than Katahdin-sired lambs. Lambs with growth retardation had lower weight (P <0.05) and general performance. Although lambs born in December had greater (P <0.05) PN, lambs born in February had greater (P <0.05) pre-weaning ADG and SW. In conclusion, the evaluated factors significantly affect both PN and overall growth performance of lambs born in winter in the semi-arid plateau of Mexico.

Keywords: lamb; hair sheep; growth; growth retardation; Mexico


El objetivo del estudio fue determinar el efecto del sexo, tipo de parto, raza, condición de crecimiento retardado y mes de nacimiento sobre peso al nacimiento (PN), crecimiento pre- y post-destete de crías ovinas de pelo nacidas en invierno (n=416). Los corderos mostraron mejor (P<0.05) desempeño que las corderas. Las crías de parto sencillo pesaron más (P<0.05) que las de parto múltiple al nacimiento y al destete, aunque las crías de parto múltiple obtuvieron mayor (P<0.05) ganancia diaria de peso (GDP) post- destete. Las crías de madre Blackbelly mostraron menor (P<0.05) peso y crecimiento. La progenie de sementales raza Dorper obtuvo un mayor (P<0.05) peso de venta (PV) y GDP post-destete que la progenie de sementales Katahdin. En las crías valoradas clínicamente con crecimiento retardado se observó un menor (P<0.05) PN y crecimiento en general. Aunque las crías nacidas en diciembre tuvieron mayor (P<0.05) PN, las crías nacidas en febrero presentaron mayor (P < 0.05) GDP pre-destete y PV. En conclusión, los factores evaluados afectan significativamente tanto el PN, y el crecimiento general de las crías nacidas en época invernal en el altiplano semiárido de México.

Palabras clave: corderos; ovinos de pelo; crecimiento; retraso del crecimiento; México


Sheep have the ability to convert coarse forages into animal protein and produce more efficiently than older ruminants (San et al., 1998). Traditionally, the semi-arid region of Mexico located in the northern mesa of the highlands is recognized for the production of sheep, mainly with the Rambouillet breed in extensive systems, and recently with hair breeds such as the Blackbelly, Pelibuey, Katahdin, Dorper and their crosses. , in semi- intensive production systems (Partida et al., 2013). The cost of production in the semi- intensive system is higher than in the extensive system, due to the necessary investments in facilities, equipment, labor and food so these systems must have a high level of productivity to be economically profitable. Therefore, the adequate selection of breeds (paternal and maternal) and the appropriate management of productive indicators from birth to the sale of the lambs should be emphasized (Partida et al., 2013).

The hair sheep breeds show great variability in terms of genotypes and productive characteristics (Wildeus, 1997). Indeed, the genotype and other characteristics affect the reproductive and productive performance of the species. In this sense, the advantages of hair sheep are their low reproductive seasonality, greater prolificacy (Galina et al., 1996), resistance to parasites (Vanimisetti et al., 2004) and the reduction of costs derived from production and wool shearing (Notter, 2000). However, hair breeds are smaller, have a lower growth rate, and muscle mass, compared to wool sheep breeds. They were developed to be exploited under conditions of warm tropical climates (Wildeus, 1997; Notter, 2000), where winter temperatures are less cold than those prevailing in the Mexican Highlands region, in whose winters polar air mass and night temperatures below 0 °C are recorded (Vidal, 2005).

However, there are no studies in this region that identify the main factors that influence the weight at birth and the development of lambs of hair breeds in winter. Therefore, the objective of the present study was to evaluate some factors such as the effect of sex, type of delivery, the race of the parents, the condition of growth retardation and the month of birth on the birth weight (PN). Besides the pre-weaning and post-weaning growth in hair lambs born in winter in a semi-intensive system in the northern region of the Mexican Highlands.


Place of study

The present study was conducted during the months of December 2017 to February 2018 at the San Isidro ranch, located in the municipality of Calera de Víctor Rosales, Zacatecas, Mexico. The region belongs to the Mexican highlands and is geographically located at 22° 58'47 "north latitude and 102° 40'49" west longitude. The climate is semi-arid cold BSk, with an annual mean temperature of 17 °C, mean maximum temperature of 30 °C in May, and mean minimum temperature of 3 °C in January, although temperatures are below 0 °C during winter reached (García, 1988).

Animals and measurements

In the present study, 416 offspring born during the winter season were used (single birth n = 242 offspring, 58.2%; double birth n = 135 offspring, 32.4%; triple birth n = 39 offspring, 9.4%). The date of birth, sex (male, female), father's race (Dorper or Katahdin), mother's race (Blackbelly, Dorper, Katahdin and Pelibuey) and type of delivery (single, double or triple) were recorded). In addition, a clinical assessment was carried out from which the offspring were classified as healthy and with growth retardation condition according to the description made by Shelton (1964). It consisted of identifying the offspring with delayed growth characterized due to the presence of shaggy fur, low body development, less vitality and physical strength; while the lambs considered clinically healthy were those that showed a soft coat, good general condition, adequate body development and general vigor. The pups were weighed at birth, at weaning (WW) and at the time of sale (SW) using a digital scale for their completion in other farms. WW were adjusted at 75 d and SW at 145 d of age. The adjusted weights were calculated as WW at 75 d = [(weaning weight-birth weight)/age at weaning in days] × 75 + birth weight, and SW at 145 d = [(final weight - observed weight at weaning)/days elapsed from weaning to final weighing in days] × 70 + weaning weight adjusted to 75 d (Thompson, 2006).

Food and accommodation

The females were fed in daytime grazing (meadow composed of annual rye grass (Lolium multiflorum Lam.), Perennial rye grass (Lolium perenne), bromine grass (Bromus willdenowii cv. Matua), fescue (Festuca arundinacea), orchard potomac (Dactylis glomerata). All this with night confinement and supplementation based on corn stubble, corn silage, alfalfa hay and oats and receiving 300 to 350 g/d of commercial feed (13% CP and 3.4 Mcal ME/kg DM) in the last third of gestation and beginning of lactation. Females were housed in roofed pens at birth where they were kept with their young during the first week of life. The young were at birth weighed and they were within the first 24 h of life identified. Subsequently, the calves went out to graze with their mothers for four to six hours a day, with an initiation supplement "creep feeding" (20% CP and 2.9 Mcal ME/kg DM) in the afternoon. Weaning was carried out at 75 d (two and a half months old), and from at this stage the offspring were fattened with 65% of commercial feed (16% CP and 3.4 Mcal ME/kg DM) and 35% of a mixture of alfalfa hay and oats or ground corn stubble. It was until they were to market sent with an average weight of 34.9 ± 0.4 kg. The animals had free access to fresh water and a mixture of mineral salts in the pen.

Statistical analysis

The statistical analysis of the data was performed with the GLM procedure of the SAS statistical package (SAS Institute, Cary N.C., U.S.A.) version 9.1. The initial statistical model included the main effects and interactions, although since the interactions between simple effects were not significant. In the reduced model only the fixed effects of calf sex (male, female), type of calving (simple, multiple), maternal race (Blackbelly, Dorper, Katahdin, Pelibuey), paternal race (Dorper, Katahdin), clinical assessment (with or without growth retardation) and month of birth (December, January, February). Differences between means were established using Tukey's test (P <0.05).


The sex of the offspring affected (P <0.05) all the evaluated characteristics. Males were heavier (P <0.05) than females at birth (4.0 vs. 3.6 kg), at weaning (19.0 vs. 16.0 kg) and at 145 d of age (36.0 vs. 29.0 kg). Furthermore, they showed a higher (P <0.05) pre- weaning ADG (194 vs. 169 g), post-weaning ADG (246 vs. 181 g) and average ADG (219 vs. 175 g). Males gained 4.5 kg more weight (P <0.05) than females between 75 and 145 d of age (Table 1).

Table 1 Effect of calf sex and type of parturition on birth weight, at weaning adjusted to 75 d, adjusted to 145 d, the pre-weaning and post-weaning weight gain (mean ± SD) in lambs of hair born in winter in a semi-intensive system of the Mexican Highlands. 

Lamb sex Type of delivery
Characteristics Male (n = 160) Female (n = 256) Simple (n = 242) Multiple (n = 174)
Body weight, kg
At birth 4.0±0.09a 3.6±0.06b 4.0±0.06a 3.5±0.08b
At weaning adjusted to 75 d 19±0.4a 16±0.2b 18±0.4a 16±0.2b
Adjusted to 145 d 36±0.6a 29±0.4b 32±0.5a 31±0.5a
Daily weight gain, g/d
Pre-Weaning (0 a 75 d) 194±6a 169±3b 188±5a 165±3b
Post-weaning (75 a 145 d) 246±5a 181±3b 202±4b 213±5a
Average (0 a 145 d) 219±4a 175±3b 195±3a 188±3b

a,bDifferent literals between columns indicate significant differences (P <0.05).

The type of delivery affected (P <0.05) the growth of the offspring. Single calving pups obtained higher (P <0.05) WB (4.0 vs. 3.5 kg), at weaning (18 vs. 16 kg) and at 145 d of age (32 vs. 31 kg), in addition to a higher (P <0.05) pre-weaning ADG (188 vs. 165 g) and average ADG (195 g vs. 188 g) than calves from multiple births. However, the multiple calving pups compensated for the lower previous growth and obtained a higher (P <0.05) post-weaning ADG (213 g vs. 202 g), thus achieving a higher (P <0.05) weight gain among the 75 at 145 d of age (15 vs. 14 kg) compared to single calving pups (Table 1).

The breed of the mother affected (P <0.05) the characteristics of body weight and pre and post-weaning ADG (Table 2). Regarding WB, the breeds from Pelibuey mothers (4.0 kg) and Dorper (3.9 kg) were heavier (P <0.05) compared to the young from Katahdin females (3.7 kg), while the lambs from Blackbelly mother obtained the lower (P> 0.05) weight (3.0 kg). The WW adjusted to 75 d was higher (P <0.05) for lambs from sheep of the Dorper and Katahdin breeds (18 kg and 17 kg, respectively), followed by lambs from mother Pelibuey (16 kg) and Blackbelly (15 kg). On the other hand, the SW adjusted to 145 d was similar (P> 0.05) among the lambs of the Dorper, Katahdin and Pelibuey breed mothers (32, 32 and 31 kg), and lower (P <0.05) in the breed lambs Maternal Blackbelly (28 kg).

Table 2 Effect of maternal and paternal breed on weight at birth, at weaning adjusted to 75 d, adjusted to 145 d, the pre-weaning and post-weaning weight gain (mean ± SD) in hair sheep pups born in winter in a semi-intensive system of the Mexican Highlands. 

Maternal race Paternal race
Characteristics Blackbelly (n = 36) Dorper (n = 240) Katahdin (n = 104) Pelibuey (n = 36) Dorper (n = 172) Katahdin (n = 244)
Body weight, kg
At birth 3.0 ± 0.13c 3.9 ± 0.07a 3.7 ± 0.09b 4.0 ± 0.11a 3.8 ± 0.08a 3.8 ± 0.07a
At weaning adjusted to 75 d 15 ± 0.5b 18 ± 0.4a 17 ± 0.3a 16 ± 0.3b 17 ± 0.3a 17 ± 0.3a
Adjusted to 145 d Daily weight gain, g/d 28 ± 1.1b 32 ± 0.5a 32 ± 0.6a 31 ± 0.8a 32 ± 0.5a 31 ± 0.5b
Pre-Weaning (0 a 75 d) 164 ± 6b 187 ± 5a 171 ± 5b 167 ± 5b 180 ± 4a 177 ± 4a
Post-weaning (75 a 145 d) 182 ±11b 213 ± 4a 219 ± 6a 214 ± 10a 212 ± 5a 202 ± 4b
Average (0 a 145 d) 173 ± 8c 198 ± 3a 194 ± 4a 189 ± 6b 196 ± 3a 189 ± 3b

a, b, c Different literals between columns indicate significant differences (P <0.05).

The pre-weaning ADG (0 to 75 d of age) was higher (P <0.05) in the lambs of Dorper mothers (187 g) and similar between the Katahdin (171 g), Pelibuey (167 g) and Blackbelly (164 g). However, the post-weaning ADG (75 to 145 d of age) was higher (P<0.05) in the offspring of mother Katahdin (219 g), Pelibuey (214 g) and Dorper (198 g) in relation to the offspring from Blackbelly mothers (173 g). In addition, the average ADG (0 to 145 d of age) was higher (P <0.05) in the lambs of Dorper (198 gr), Katahdin (194 g) and Pelibuey (185 g), in relation to the offspring of mothers Blackbelly (173 g).

The breed of the father did not affect (P> 0.05) the WB, the WW, or the pre-weaning ADG (0-75 d of age). Dorper sire lambs were heavier (P <0.05) at 145 of age (32 kg vs. 31 kg) and obtained higher (P <0.05) post-weaning ADG (212 vs. 202 g) and average ADG (196 vs. 190 g) than lambs of the Katahdin sire breed (Table 2).

Clinically healthy calves obtained a higher (P <0.05) PN than lambs with growth retardation (3.9 vs. 3.4 kg), this difference was also observed at weaning (18 vs. 13 kg) and at 145 d of age (34 vs. 21 kg). In the post-weaning period (between 75 and 145 d), the healthy lambs gained on average 7 kg more (P <0.05) than the stunted lambs (Table 3).

Table 3 Effect of clinical condition and month of birth on birth weight, at weaning adjusted to 75 d, adjusted to 145 d, the pre-weaning and post-weaning weight gain (mean ± SD) in hair lambs born in winter in a semi-intensive system of the Mexican Highlands 

Clinical assessment Birth month
Característica Clinically healthy (n =332) Growth retardation (n= 84) December (n = 20) January (n = 316) February (n = 80)
Body weight (kg)
At birth 3.9±0.05a 3.4±0.13b 4.6±0.25a 3.8±0.06b 3.6±0.13c
At weaning adjusted to 75 d 18±0.3a 13±0.2b 16±0.3b 16±0.2b 20±0.8a
Adjusted to 145 d 34±0.3a 21±0.5b 30±0.7b 31±0.4b 35±0.9a
Daily weight gain (g / d)
Pre-weaning (0 to 75 d) 192±3a 124±3b 156±4b 169±3b 223±11a
Post-weaning (75 to 145 d) 227±3a 123±5b 192±8a 206±4a 212±7a
Average (0 to 145 d) 209±2a 124±4b 173±5b 187±3b 218±6a

a, b Different literals between columns indicate significant differences (P <0.05).

On the other hand, it was observed that lambs born in December (4.6 kg) were heavier (P <0.05) than those born in January (3.8 kg), followed by those born in February (3.6 kg). At weaning and at 145 d of age, lambs born in December and January obtained similar weights (P <0.05), although those born in February (P <0.05) were 4 kg heavier. Furthermore, lambs born in February had higher (P <0.05) pre-weaning ADG and average ADG. No differences were found (P> 0.05) in the post-weaning ADG, nor (P> 0.05) in the adjusted weight at 75 and 145 d of age (Table 3).


In correspondence with the results of the present work, several authors (Carrillo and Segura, 1993; Garduño et al., 2002; Vicente-Pérez et al., 2015) have previously reported the greater weight and development that lambs generally present on the lambs. In this regard, Bores-Quintero et al. (2002) observed that during the post-weaning stage the ADGf males exceeded (P <0.05) by 27% the ADG of females. While De Vargas Junior et al. (2014), Schanbacher et al. (1980), Ghafouri-Kesbi and Notter (2016) conclude that the differences in the weight and development of lambs and ewes that reflect the difference in the endocrine environment and nutrient requirements between the sexes.

The calves born in single birth presented a higher pre-weaning growth rate compared to those born in multiple births, which coincides with that previously reported by Garduño et al. (2002), Mellado, et al. (2016) and Simeonov et al., (2014). However, the multiple calving lambs compensated for the lower pre-weaning growth and obtained a higher post- weaning ADG to end up with a weight adjusted to 145 d similar to that of the lambs born in single calving. Similar results have been reported by Galaviz-Rodríguez et al. (2014) and Simeonov et al 2014, and it is considered that during the pre-weaning period, growth is largely determined by the amount of mother's milk. However, once multiple calving lambs are weaned, they consume more feed and they grow at a rate that allows them to reach a weight similar to single-calving lambs at slaughter weight age.

The results obtained in the present study in relation to the maternal breed demonstrate the importance of choosing the bellies that will constitute the maternal base in sheep farms. The weight and development of the lambs will depend on this, mainly taking into account the climatic conditions that occur in this region where the annual thermal oscillation presents differences between the average temperatures at different times of the year from 12 ºC to more than 20 ºC (FAO, 2020). In this regard, Grepe (2001) mentions that the first step in sheep production begins with the choice of breed and the main objective of exploitation.

In this sense, the Dorper breed has shown adaptation and better growth speed (210 to 330 g/d) under grazing conditions in the South African desert (Cloete et al., 2000). For its part, the Katahdin breed, developed in the northeast of the United States of America, has been characterized by good productive development (236 g/d) in arid and tropical conditions (Burke and Apple, 2007). Additionally, López-Carlos et al. (2010) carried out a study in the Mexican highlands comparing post-weaning growth in sheep of hair breeds. They reported that the Dorper breed offspring (238 g/d) obtained a higher ADG than the Katahdin breeds (226 g/d), Pelibuey (218 g/d) and Blackbelly (188 g / d), with Blackbelly being the one with the lowest productive performance. In this regard, Wildeus et al. (2005) mention that the Blackbelly breed offspring have a lower ADG than the Katahdin and Santa Cruz breed lambs (73 g/d vs. 109 and 86 g/d, respectively) fed with forage-based diets.

The Dorper and Katahdin paternal breed lambs presented similar WB and WW, in agreement with that reported by Macías-Cruz et al. (2010) who observed that the crosses of Dorper and Katahdin studs with Pelibuey females produce offspring for supply with acceptable growth rates, as well as good adaptation in arid climates. However, the progeny of Dorper stud obtained a higher post-weaning ADG and a higher SW (P <0.05) compared to the Katahdin sire lambs, which coincides with that reported by Macías-Cruz et al. (2010). He reported that the crossbred lambs of the paternal Dorper breed obtained 16 and 25% more weight per day than those of the paternal Katahdin or Pelibuey breed respectively. In this sense, it is assumed that larger breeds have a higher growth speed than breeds of smaller size or weight at maturity (Owens et al., 1993). Although the breeds known as hair have not been evaluated as widely as the wool-producing breeds, it has been reported that the Dorper breed has excellent growth characteristics, for which its use as a terminal breed is recommended, being competitive even when compared with sheep-type meat breeds (Notter et al., 2000; Snowder and Duckett, 2003).

On the other hand, in the present study a frequency of 25% of offspring that presented the condition of growth retardation was observed. The foregoing represents the first scientific report that this condition occurs in sheep in Mexico due to the low winter temperatures. However, this condition is of great importance in pigs and has been reported as an important cause of mortality and low productivity in piglets (Wu et al., 2006). The stunted growth condition has been reviewed by Wang et al. (2017), who indicate that it can manifest itself in all species, being caused by a combination of factors that start from the prenatal period, and is known as “intrauterine growth retardation”. This problem is caused by genetic, epigenetic, maternal maturity, and environmental factors such as the mother's nutritional status, stress, illnesses, toxins, etc. According to these authors, intrauterine growth restriction has permanent negative effects on neonatal adaptation, survival and pre-weaning growth, feed utilization efficiency, general lifelong health, body composition, as well as reproductive performance in adult life, and therefore has important implications for animal production.

In relation to the differences obtained in the weight of lambs in winter, it has been shown that pregnant ewes exposed to low ambient temperatures undergo metabolic adaptations to meet the increased energy expenditure associated with the cold. It leads to mobilize body fat and releasing glucose through the liver, which crosses the placenta and increases glucose supply to the fetus, stimulating insulin secretion and fetal growth without apparent risk of clinical ketosis (Kenyon et al., 2006; Norouzian, 2015; Symonds et al., 1986; Thompson et al., 1982). Recently, Piquer et al. (2017), explain that the exposure of pregnant rats to 4 °C for 3 h per day caused an increase in the levels of norepinephrine and corticosterone in the maternal circulation, and a decrease in the placental capacity to eliminate norepinephrine from the fetus towards the circulation of the mother. It caused an increase in the weight of the placenta and the body weight of the offspring. The environmental temperatures under which the present study was carried out were colder in December (mean of 10.5 °C and minimum of -9 °C) than in January (mean of 11.6 ° C and minimum of -2 ° C) and February ( mean of 13.9 ° C and minimum of -2 ° C). It probably explains why higher birth weights were obtained in lambs born in December.

Adverse environmental conditions due to the combined effect of low temperature, precipitation and wind in the lambing season are the main cause of mortality in hair lambs due to starvation-exposure syndrome (Refshauge et al., 2016). In addition, Mellor and Stafford (2004), mention that hair sheep show greater susceptibility to cooling than wool sheep, making them more susceptible to respiratory diseases under cold and humid conditions. In this sense, Saravia and Cruz (2003) mention that, by lowering the air temperature below the minimum critical temperature (10 °C), the point where the production of metabolic heat is insufficient to maintain body temperature and achieve weight gains in lambs. The foregoing would explain why the lambs born in the month of December, despite having obtained a higher WB, subsequently observed a lower weight gain than the lambs born in January and February.

It is important to consider the maternal race, the paternal race and the month of birth in the planning and management of semi-intensive farms with hair sheep, particularly in the climatic and production conditions of the northern part of the Mexican Highlands.


The lambs born in single and multiple births, despite showing different WB, reach a similar weight after weaning, the mother's breed determines the WB and the growth of the lambs, and it is not recommended to program Blackbelly female births in the winter months. The breed of the stallion (Dorper or Katahdin) does not affect the birth weight or the initial growth of the lamb, although it determines the post-weaning growth, so the use of the Dorper breed is recommended to improve the weight of sale at 145 d old. Lambs with growth retardation have a lower productive performance than lambs that do not present this delay. Therefore, it is advisable to minimize the incidence of lambs with growth retardation. Lambs born in December have a higher birth weight, although later they obtain lower weight gains than the obtained ones by lambs born in January or February.


It is important to consider the maternal race, the paternal race and the month of birth in the planning and management of semi-intensive farms with hair sheep, particularly in the climatic and production conditions of the northern part of the Mexican Highlands. In addition, provide better nutritional conditions to the females during gestation, parturition and lactation, to promote better development of lambs and avoid the condition of growth retardation, since these factors significantly affect the weight at birth and the development of the lambs before and after weaning.


Bores-Quintero RF, Velázquez Madrazo PA, Heredia, Aguilar M. 2002. Evaluación de razas terminales en esquemas de cruza comercial con ovejas de pelo F1. Técnica Pecuaria en México. 40(1): 71-79. ISSN: 0040-1889. htpps:// ]

Burke JM, Apple JK. 2007. Growth performance and carcass traits of forage-fed hair sheep wethers. Small Ruminant Research. 67(2-3): 264-270. ISSN: 0921-4488. [ Links ]

Carrillo L, Segura JC. 1993. Environmental and genetic effects on preweaning growth performance of hair sheep in México. Tropical Animal Health and Production. 25(3): 173- 178. ISSN: 1573-7438. [ Links ]

Cloete SWP, Snyman MA, Herselman MJ. 2000. Productive performance of Dorper sheep. Small Ruminant Research. 36(2): 119-135. ISSN: 0921-4488. [ Links ]

De Vargas Junior FM, Martins CF, dos Santos Pinto G, Ferreira MB, de Almeida Ricardo H, Leão AG, Mendes Fernandes AR, Teixeira A. 2014. The effect of sex and genotype on growth performance, feed efficiency, and carcass traits of local sheep group Pantaneiro and Texel or Santa Inês crossbred finished on feedlot. Tropical Animal Health and Production. 46(5):869-875. ISSN: 0049-4747. [ Links ]

FAO. 2020. Estado de la diversidad biológica de los árboles y bosques en el Norte de México. 1. Características ecológicas y socio-económicas. ]

Galaviz-Rodríguez JR, Ramírez-Bribiesca JE, Vargas-López S, Zaragoza-Ramírez JL, Guerrero-Rodríguez JD, Mellado-Bosque M, Ramírez RG. 2014. Effect of three production systems of central Mexico on growth performance of five lamb genotypes. Journal of Animal and Plant Sciences. 24(5): 1303-1308. ISSN: 1018-7081. ]

Galina MA, Morales R, Silva E, López B. 1996. Reproductive performance of Pelibuey and Blackbelly sheep under tropical management systems in Mexico. Small Ruminant Research. 22(1): 31-37. [ Links ]

García E. 1988. Modificaciones al sistema de clasificación climática de Köppen. Instituto de Geografía, UNAM. Offset Larios. México, D.F. ISBN: 970-32-1010-4 ]

Garduño RG, Hernández GT, Álvarez MC. 2002. Crecimiento de corderos Blackbelly entre el nacimiento y el peso final en el trópico húmedo de México. Veterinaria México. 33(4): 443-453. ISSN: 0301-5092. ]

Ghafouri-Kesbi F, Notter. 2016. Sex influence on genetic expressions of early growth in Afshari lambs. Archives Animal Breeding. 59(1): 9-17. ISSN: 0003-9438. [ Links ]

Grepe N. 2001. Crianza de Ovinos. Centro de Estudios Agropecuarios. Editorial Iberoamericana S.A. de C.V. ISBN:970-62-5264-9. htpp:// ]

Kenyon PR, Revell DK, Morris ST. 2006. Mid-pregnancy shearing can increase birthweight and survival to weaning of multiple-born lambs under commercial conditions. Australian Journal of Experimental Agriculture. 46(7): 821-825. ISSN: 1446-5574. https://doi:10.1071/EA05329 [ Links ]

López-Carlos MA, Ramírez RG, Aguilera-Soto JI, Aréchiga CF, Rodríguez H. 2010. Size and shape analyses in hair sheep ram lambs and its relationships with growth performance. Livestock Science. 131(2-3): 203-211. ISSN: 1871-1413. [ Links ]

Macías-Cruz U, Álvarez-Valenzuela FD, Rodríguez-García J, Correa-Calderón A, Torrentera-Olivera NG, Molina-Ramírez L, Avendaño-Reyes L. 2010. Growth and carcass traits in pure Pelibuey lambs and crosses F1 with Dorper and Katahdin breeds in confinement. Archivos de Medicina Veterinaria. 42(3): 147-154. ISSN: 0301-732X. ]

Mellado M, Macías U, Avendaño L, Mellado J, García E. 2016. Growth and pre-weaning mortality of Katahdin lamb crosses. Revista Colombiana de Ciencias Pecuarias. 29(4): 288-295. ISSN: 0120-0690. [ Links ]

Mellor DJ, Stafford KJ. 2004. Animal welfare implications of neonatal mortality and morbidity in farms animals. The Veterinary Journal. 168(2): 118-133. ISSN: 1090-0233. [ Links ]

Norouzian MA. 2015. Effects of lambing season, birth type and sex on early performance of lambs. New Zealand Journal of Agricultural Research. 58(1): 84-88. ISSN: 0028-8233. [ Links ]

Notter DR. 2000. Potential for hair sheep in the United States. Journal of Animal Science. 77(suppl_E): 1-8. ISSN: 1525-3163. [ Links ]

Owens FN, Dubeski P, Hanson CF. 1993. Factors that alter the growth and development of ruminants. Journal of Animal Science. 71(11): 3138-3150. ISSN: 1525-3163. [ Links ]

Partida JA, Braña-Varela D, Jiménez-Severiano H, Ríos-Rincón FG, Rodríguez-Germán B. 2013. Manual de Producción de Carne Ovina. Libro Técnico No. 5. Centro Nacional de Investigación Disciplinaria en Fisiología y Mejoramiento Animal. Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias, México. ISBN: 978-607-37-0036-8. ]

Piquer B, Fonseca JL, Lara HE. 2017. Gestational stress, placental norepinephrine transporter and offspring fertility. Reproduction. 153(2): 147-155. ISSN: 1741-7899. [ Links ]

Refshauge G, Brien FD, Hinch GN, van de Ven R. 2016. Neonatal lamb mortality: factors associated with the death of Australian lambs. Animal Production Science. 56(4): 726-735. ISSN : 1836-5787. [ Links ]

San C, Sanchez A, Alfonso M. 1998. Small ruminant production systems and factors affecting lamb meat quality. Meat Science. 49: S29-S64. [ Links ]

Saravia C, Cruz C. 2003. Influencia del ambiente atmosférico en la adaptación y producción animal. Montevideo. Universidad de la República Facultad de Agronomía, Nota Técnica 50. Universidad de la República de Uruguay, Montevideo, Uruguay. academicaarchivo.pdfLinks ]

Schanbacher BD, Crouse JD, Ferrell CL. 1980. Testosterone influences on growth, performance, carcass characteristics and composition of young market lambs. Journal of Animal Science. 51(3): 685-691. ISSN: 1525-3163. ]

Shelton M. 1964. Relation of environmental temperature during gestation to birth weight and mortality of lambs. Journal of Animal Science. 23(2): 360-364. ISSN: 1525-3163. [ Links ]

Simeonov M, Todorov N, Nedelkov KA, Kirilov A, Harmon DL. 2014. Influence of live weight, sex and type of birth on growth and slaughter characteristics in early weaned lambs. Small Ruminant Research. 121(2-3): 188-192. ISSN: 0921-4488. [ Links ]

Snowder GD, Duckett SK. 2003. Evaluation of the South African Dorper as a terminal sire breed for growth, carcass, and palatability characteristics. Journal of Animal Science. 81(2): 368-375. ISSN: 1525-3163. [ Links ]

Symonds ME, Bryant MJ, Lomax MA. 1986. The effect of shearing on the energy metabolism of the pregnant ewe. British Journal of Nutrition. 56(3): 635-643. ISSN: 1475-2662. [ Links ]

Thompson GE, Bassett JM, Samson DE, Slee J. 1982. The effects of cold exposure of pregnant sheep on foetal plasma nutrients, hormones and birth weight. British Journal of Nutrition. 48(1): 59-64. ISSN: 1475-2662. [ Links ]

Thompson JM. 2006. Sheep Production Guide, EM 8916-E. Oregon State University. ]

Vanimisetti HB, Greiner SP, Zajac AM, Notter DR. 2004. Performance of hair sheep composite breeds: resistance of lambs to Haemonchus contortus. Journal of Animal Science. 82(2): 595-604. ISSN: 1525-3163. [ Links ]

Vicente-Pérez R, Avendaño-Reyes L, Álvarez FD, Correa-Calderón A, Meza-Herrera CA, Mellado M, Quintero JA, Macías-Cruz U. 2015. Comportamiento productivo, consumo de nutrientes y productividad al parto de ovejas de pelo suplementadas con energía en el preparto durante verano e invierno. Archivos de Medicina Veterinaria. 47(3): 301-309. ISSN 0301-732X. [ Links ]

Vidal ZR. 2005. Las regiones climáticas de México. Instituto de Geografía, Universidad Nacional Autónoma de México (UNAM), México, D.F.Pp. 76. ISBN: 970-32-2394-X. ]

Wildeus S. 1997. Hair sheep genetic resources and their contribution to diversified small ruminant production in the United States. Journal of Animal Science. 75(3): 630-640. ISSN: 1525-3163. [ Links ]

Wildeus S, Turner KE, Collins JR. 2005. Growth Performance of Barbados Blackbelly, Katahdin, and St. Croix Hair Sheep Lambs Fed Pasture- or Hay-based Diets. Sheep and Goat Research Journal. 20:37-41. ISSN: 1535-2587. ]

Wang J, Feng C, Liu T, Shi M, Wu G, Bazer FW. 2017. Physiological alterations associated with intrauterine growth restriction in fetal pigs: causes and insights for nutritional optimization. Mol. Reprod. Dev. 84:897-904. ISSN: 1098-2795. [ Links ]

WU G, Bazer FW, Wallace JM, Spencer TE. 2006. Board-invited review: intrauterine growth retardation: implications for the animal sciences. Journal of Animal Sience. 84(9): 2316-2337. ISSN: 1525-3163. [ Links ]

Received: February 24, 2020; Accepted: November 25, 2020; Published: January 04, 2021

Code: 2020-18.

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