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Revista mexicana de ciencias pecuarias
versión On-line ISSN 2448-6698versión impresa ISSN 2007-1124
Rev. mex. de cienc. pecuarias vol.7 no.1 Mérida ene./mar. 2016
Reviews
Energy requirements of hair sheep in the tropical regions of Latin America. Review
a División Académica de Ciencias Agropecuarias, Universidad Juárez Autónoma de Tabasco. Carretera Villahermosa-Teapa, km 25, CP 86280. Villahermosa, Tabasco, México.
b Facultad de Medicina Veterinaria y Zootecnia, Universidad Autónoma de Yucatán. Mérida, Yucatán, México.
c Universidade Federal de Viçosa, Viçosa, MG 36571. Brazil.
d Instituto Tecnológico de Tizimín. Departamento de Investigación y Posgrado. Tizimín, Yucatán, México.
e Department of Animal Science, Texas A&M University, College Station. USA.
Breeds of hair sheep play an important role in animal production in tropical regions; however, their nutrient requirements have not been determined to the same extent as those of wool breeds. Due to the environmental conditions of the tropical regions (climate, quality and availability of feedstuffs), it is reasonable to hypothesize that energy requirements and efficiency of utilization of metabolizable energy (ME) may be different between hair and wool breeds of sheep. Information available on hair sheep shows a large discrepancy regarding energy requirements. Based on available literature data for female sheep, ME requirement for maintenance (MEm) was 419±129 kJ/ kg BW0.75 (mean ± standard deviation) and for the male 388±123 kJ/kg BW0.75. The requirement of net energy for gain (NE g ) ranged from 8.75 to 14.06 kJ/g (11.63±1.86 kJ/g). The efficiency of ME utilization for maintenance (km ) and gain (kg ) were 0.66±0.02 and 0.42±0.04, respectively. This review indicated also that information is scarce for adult ewes at different physiological stages (maintenance, lactation, or pregnancy). More work is required regarding estimates of nutrient requirements of hair sheep in order to develop adjustments to existing nutrition models to predict animal’s response under the conditions prevailing in the tropics (animal type, environment and feedstuffs available).
Keywords: Hair sheep; Energy requirements; Tropics; Maintenance; Gain; Efficiency
Los ovinos de pelo juegan un papel importante en la producción animal en las regiones tropicales; sin embargo, sus requerimientos nutricionales no se han determinado en la misma medida que los de las razas de lana. Debido a las condiciones ambientales de las regiones tropicales (clima, calidad y disponibilidad de alimentos), es razonable la hipótesis de que los requerimientos de energía metabolizable (EM) y la eficiencia de utilización de la EM pueden ser diferentes entre los ovinos de razas de pelo y de lana. La información disponible en ovinos de pelo muestra una gran discrepancia en cuanto a las necesidades de energía. Con base en datos de la literatura disponible para hembras ovinas, el requerimiento de EM para mantenimiento (EMm) fue de 419±129 kJ/kg PC0.75 (media ± desviación estándar) y para machos fue 388±123 kJ/kg BW0.75. El requerimiento de energía neta para la ganancia de peso (ENg ) varió de 8.75 a 14.06 kJ/g (11.63±1.86 kJ/g). Las eficiencias de utilización de la EM para el mantenimiento (km ) y la ganancia de peso (kg ) fueron de 0.66±0.023 y 0.42±0.044, respectivamente. Esta revisión también indicó que la información es escasa para ovejas adultas en diferentes etapas fisiológicas (mantenimiento, lactancia y gestación). Se requiere más trabajo de investigación con relación a la estimación de las necesidades de energía de los ovinos de pelo, con el fin de hacer ajustes a los modelos existentes de alimentación, con el objetivo de predecir la respuesta de los animales con la condición que prevalece en los trópicos (tipo de animal, medio ambiente y alimentos disponibles).
Palabras clave: Ovinos de pelo; Requerimientos de energía; Trópicos; Mantenimiento; Ganancia; Eficiencia
Introduction
Sheep production in the tropical regions of Latin America and the Caribbean has increased during recent years. Production systems in those regions are characterized by low-inputs, and breeds employed are mostly hair sheep. From a comparative standpoint with wool breeds, breeds of hair sheep are small, with a slow growth rate and poor muscular conformation, therefore, these have been crossed to improve rate of growth1. Hair breeds such as Dorper and Katahdin show high rates of growth and have been introduced in breeding schemes with the Pelibuey and Blackbelly breeds commonly used in Mexico2.
In spite of the importance of hair breeds in tropical and world sheep production, only few experiments have been carried out to assess their energy requirements3,4,5. Knowledge of nutrient requirements and efficiency of utilization of feed resources is important to optimize productivity and achieve expected performance5,6,7. However, frequently published values and prediction models of requirements, are based on breeds from temperate environments5,7,8,9 with results in animal performance different from what is expected and the inability to predict animal performance. In this sense10 recently demonstrated the importance of using specific equations to local conditions to ensure that accurate and reliable predictions of dry matter intake by Santa Inês sheep are made. Also, some studies have stated that hair sheep breeds have different energy requirements compared to wool breeds, but this assertion has been based on limited experimental data11.
On the other hand, energy intake by sheep is considered to be the first limiting nutrient for growth12. Moreover, insufficient energy supply to the animal results in slow growth, older age at puberty, reduced fertility, decreased milk production and greater susceptibility to nematodes. In adult animals, when energy intake is lower than that required for maintenance, the animal uses its own body energy reserves13, particularly fat and when this occurs in excess, metabolic diseases such as ketosis may arise. At the end of pregnancy and beginning of lactation, there may also occur an energy unbalance which induces the animal to use its own body energy reserves for milk production14.
At present, due to the fact that the main resources for animal production (land, feed, water) are more limited in some regions of the world, precise determination of nutrient required by the animals is of paramount importance to avoid waste of these resources12. The NRC15 includes hair sheep in the database used to predict daily weight gain (DWG). The Cornell Net Carbohydrate and Protein System for sheep (CNCPS-S) or Small Ruminant Nutrition Systems (SRNS)12,16 have been evaluated for the prediction of DWG in Pelibuey sheep6,17 and DWG and dry matter intake in Santa Inês sheep18,19,20, and adjustments to such models have been proposed to make them comparable to those of Pelibuey sheep6,17. Costa et al21 reported that it is necessary to have a database which can be updated frequently, by means of a meta-analysis in such a way that models developed have recent data incorporated. Tedeschi et al12 concluded that it is necessary more data which allow an improvement to be realized in the precision of prediction models based on the SRNS under different production conditions. However, the available information for hair sheep is scattered and outdated. Very little is known in Mexico regarding metabolizable energy (ME) requirements of hair sheep for maintenance and weight gain and the efficiency with which ME is utilized for both physiological functions. The knowledge of such information may help to improve the efficiency of sheep production under practical conditions in sheep farms thus improving farm profitability.
The aim of the present review was to analyze available information on ME requirements and efficiency of its utilization for maintenance and weight gain in hair sheep kept under tropical conditions in Latin America, in order to visualize potential areas of research which may lead towards a better understanding of nutrient requirement by hair sheep.
Situation of hair sheep production
In the main sheep producing countries in Latin America and the Caribbean, the phenotypes and breeds of sheep are diverse and they are generally described as “Creole”, and receive different names depending on where they are located and in some cases the same breed is named in different ways, for example the Pelibuey or Tabasco breed in Mexico, in the Virgin Islands the Pelo Blanco or Saint Croix breed, in Tobago West African or Roja Africana breed are the same. In Brazil there are three breeds of hair sheep: Morada Nova, Somali Brasileño and Santa Inês. Table 1 shows the breeds of hair sheep and their distribution in Latin America. Mature weight by sex of each breed was taken from the “Breeds of Livestock” website (www.ansi.okstate.edu/breeds/) of the Animal Science Department at Oklahoma State University15. According to NRC15, in order to obtain a more precise prediction of energy requirements, it is necessary to consider mature weight of the animals, as this is associated with composition of the retained tissue depending on the percentage of mature weight of the animal, which varies among breeds and genotypes. In sheep, it has been reported that ME requirements for maintenance decrease as the animal gets older, which is related with the proportion achieved of mature weight15.
Data on energy requirements for maintenance and growth of hair sheep
A literature review using the Science Direct (http://www.sciencedirect.com/), and Google Scholar (http://scholar.google.com/) search engines was conducted to create a database, and papers published in the scientific literature were obtained from journals such as: Tecnica Pecuaria en Mexico, Brazilian Journal of Animal Science, Ciência Agrotecnica, Small Ruminant Research, Semina: Ciências Agrárias and Italian Journal of Animal Science. The method by means the ME requirement for maintenance and growth was estimated is also presented in Table 2. It can be appreciated that the work carried out with hair sheep was performed with regression and comparative slaughter techniques; different to what has been done with wool sheep, since the energy requirements of these sheep has been obtained basically with calorimetric techniques23-26. There is a need to initiate calorimetric work with hair sheep in tropical regions to validate the data obtained by regression and comparative slaughter techniques.
Pb= Pelibuey; Ra= Rambouillet; SI= Santa Inês; MN= Morada Nova; Do= Dorper; BS= Brazilian Somali. CS= Comparative slaughter; REG1= Regression of ME intake on changes in live weight, in experiments published in the literature; REG2= Regression of ME intake on changes in live weight (with original data from the experiments).
Energy requirements and efficiency of ME utilization for maintenance (km)
Energy costs for maintenance represent between 60 and 80 % of total energy consumed by ruminants25. Energy requirements and in particular those for maintenance (Em), as well as the efficiency of feed utilization and the energy contained in tissues (adipose, muscular) in cattle has been a research subject during several decades25,27. The requirement of metabolizable energy (ME) for maintenance (MEm ), can be equated to the so-called “basal metabolism” (mostly used in human nutrition) and is defined as the amount of energy that the animal needs in order to maintain vital processes (basic functions [heart, lung, kidney, nervous, “work”] and cellular functions [fat and protein turnover; Na/K ion pump]) of the body under normal conditions. In a practical way, the ME m could be defined as the state in which the animal does not suffer changes in its body composition9,23. It has also been defined as the state in which ME intake (MEI) will not result in loses or gains of energy (RE) in the animal body tissues; Ferrell and Oltjen28 define this unit as, MEm= MEI at which RE= 0; or HP (heat production)= MEI.
Among the factors which influence Em: body weight (BW), breed, sex, physiological condition, nutritional level, environmental conditions, stress, exercise, or physical activity and parasitism can be listed9,15. The efficiency of utilization of MEm (km ) represents that fraction of ME which can be converted to net energy (NE), to support maintenance requirements of the ruminant. The fraction which is no converted to NE is lost as heat increment including fermentation in the gastrointestinal tract and biochemical reactions at the cellular level29. The efficiency of energy utilization of feedstuffs has an economic impact, and the best way to determine it is by means of feed conversion efficiency27,30.
Table 3 shows estimations of ME and NE requirements for maintenance (MEm and NEm respectively) and Table 4 shows efficiencies of ME utilization for maintenance (km ) estimated in hair sheep of different breeds under tropical conditions of Latin America.
Pb= Pelibuey; Ra= Rambouillet; SI= Santa Inês; MN= Morada Nova; Do= Dorper; BS= Brazilian Somali. CV= Coeficient of variation.
It is important to point out that for the case of ewes, in the present review only two experiments were found which were related to this information31,32 and the mean value (± standard deviation) for MEm was 419 ± 129 kJ/kg BW0.75. This information must be taken with reserve since it comes from a reduced number of observations. In this sense, Chávez et al33, found that supplying 506 kJ/kg BW0.75 to Pelibuey ewes during the first 100 d of pregnancy and 700 kJ/kg BW0.75 during the last 50 d of pregnancy was enough for the ewes to gain weight (36 g/d approximately). Along with this, they reported that for lactation, the supply of 1,000 kJ/kg BW0.75 was enough for the ewes to gain 4 to 20 g/d, producing 700 to 800 ml of milk and be able to sustain a weight gain by their lambs of 200 g/d.
For growing male sheep, data from nine experiments were used which involved Pelibuey3,32, Santa Inês4,18,20, Morada Nova8,34, 1/2 Dorper × 1/2 Santa Inês30) and Brazilian Somali lambs26. The mean value found in the present experiment for MEm was 388 ± 123 kJ/kg BW0.75; however, this data showed a relatively high coefficient of variation of 31.8 %, this variation can be attributed to differences between experiments, genotypes, and crosses, among several other factors.
In several experiments8,20,22,26,34 the values for MEm (kJ/kg BW0.75) were derived from the relation of BW/EBW and using the km reported by these authors. In relation to ME m , in growing Santa Inês sheep, some authors4,20 report a mean value for ME m of 342 (±107) kJ /kg BW0.75. for Morada Nova sheep8,34 an average ME m of 264 (±8.23) kJ/kg; for Pelibuey3,32, a mean value of 544 (±76.4) kJ/kg. While others26,30 reported only values available for 1/2 Dorper × 1/2 Santa Inês and Brazilian Somali lambs (Table 3).
In relation to km , it was found an average value of 0.7018. An average value of 0.67 was reported8 when estimating km in diets with forage proportions of 40, 55 and 704,7,20; in Santa Inês growing males reported a km value of 0.66. Recently30 it was found a km of 0.63 in 1/2 Dorper × 1/2 Santa Inês lambs. The mean value for km in the present review was 0.66. In this respect, even when ME of diets of medium quality (such as those commonly used in the tropics) is utilized with a low efficiency for maintenance and gain, km is relatively higher compared to kg 29. Furthermore, this author reported that km could be considered on average as 0.60 independently of the diet. This approximates to that found in this work, where an average km value of 0.66 was obtained (Table 4).
Lack of information is more evident for the case of ewes, for which there are very few reports regarding determination of energy requirements in their different physiological stages (maintenance, pregnancy, lactation), being these fundamental components of the production systems. Furthermore, it is known that feeding of ewes before and after parturition has an effect on survival and growth of the offspring. It is thus necessary to continue with work focused on the determination of the nutrient requirements of hair sheep and develop a feeding system based on characteristics of the ration, breed and environmental conditions prevailing in Latin American tropics. Ration formulation with precise knowledge of the energy requirements of hair sheep and the concentration of ME (and its efficiency of utilization), of the feedstuffs available in the tropics, will have an influence on improvement in sheep production, by giving sheep the precise amount of feed that require without over or under estimating its requirements nor the energy value of feedstuffs. Ration formulation for sheep based on the precise knowledge of their requirement for maintenance and production, will contribute to reduce production costs, since there would probably be a lower waste (as heat increment) arising from ME absorbed from the GIT. Knowledge of energy requirements of hair sheep for the different physiological stages (maintenance, growth, pregnancy and lactation), is of paramount importance since these could be readily incorporated in different programs for ration formulation (CNSPS-S/SRNS) and with these, formulates rations that will satisfy the energy requirements of hair sheep kept under tropical conditions.
Energy requirements for weight gain and estimated kg
The energy requirement for growth or weight gain (MEg or NEg), corresponds to the caloric value or gross energy of the protein and fat stored in the body23. The ARC23 mentioned that rate of growth affects protein deposition which in turn affects NE requirements. Composition of weight gain, expressed as empty body weight (EBW), is the main determinant of energy requirements for weight gain, which is estimated from energy retained in the body15. Moreover, the main factor determining the composition of gain in the mature stage, in which as the animal is closer to its adult weight, more fat (and energy) is stored in the gain.
Ferrell and Oltjen28 reported that ME in the ration is used with different efficiencies depending on the type of ration (ingredients), level of intake and the physiological function for which it is being utilized by the animal. Tolkamp29 reported that kg for rations of low to medium quality (such as those of tropical forages), is expected to be low. Tedeschi et al35) mentioned that there are factors which may affect kg , pointing out that ration (energy density and volatile fatty acids molar proportions) and the composition of the weight gain are the most important issues; these authors concluded that the use of a combination of chemical composition of the body and energy concentration of the ration may be a better approach for the assessment of efficiency of utilization of ME for maintenance and growth. Indeed, some authors36,37 demonstrated that the main factor affecting kg is the composition of gain in the EBW; even when the level of ME interferes with kg , a ration with a high ME concentration, will induce a high fat content in the gain, therefore, the effect of the energy content of the ration is considered in the composition of the gain.
On the other hand36,37 these same authors did not find evidence of genetic background on NE requirements for weight gain, concluding that the effect of breed or genotype on NE for gain can be attributed to the different mature weights and to the precocity of fat deposition in the different breeds of cattle. Different mature weights of breeds, may determine different degrees of maturity in animals with the same absolute weight and the same rate of gain, high energy concentrations are expected in the gain of animals of breeds with low weight at maturity compared to that of late maturity breeds. In the present review, works with Morada Nova lambs8,21 estimated values of 13.8 to 17.9 kJ NE/g gain and 7.0 to 9.2 kJ NE/g gain respectively, in animals weighing from 15 to 30 kg. Regadas-Filho et al22 in Santa Inês growing male lambs reported values of 10.0 to 14.5 kJ NE/g gain in animals between 15 and 30 kg. Nonetheless, in Santa Inês growing male lambs found values of 6.0 to 9.0 kJ NE/g gain7,20. Galvani et al30 and Pereira et al26 reported values of 9.3 to 14.7 and 9.2 to 11 kJ NE/g gain in 1/2 Dorper × 1/2 Santa Inês and Brazilian Somali lambs, respectively. Using the values described above, it was found a mean value of 8.75 to 14.06 kJ NE/g gain in hair sheep of different breeds under tropical conditions of Latin America. Table 5 shows NE requirements for daily weight gain (MJ/animal/d) of hair sheep according to live weight and expected weight gain.
As regard to the efficiency of ME utilization for growth, it has been reported that in growing Pelibuey sheep, this value varies according to age and weight, being higher during the first stages of growth and decreasing as the animal approaches mature weight, due to a greater fat deposition in body tissues32. However, those authors also suggested that the greater demand may be due to the higher requirement of energy per unit weight gain. Table 6 shows estimations of kg in hair sheep. The kg reported for hair sheep ranged from 0.388 to 0.4838. The average kg value obtained for the purpose of this review was 0.42 ± 0.04.
Based on the data obtained in this review regarding the energy requirement of weight gain (MJ NE/animal/d) and kg (0.42), it was found that the energy requirements for weight gain (kJ ME/g gain) ranged from 20.8 to 33.5 (mean: 27.7). Similarly, it was reported that the mean values for the energy requirements for gain (MJ ME/animal/d) derived, were higher by 26 % than those previously reported for growing Pelibuey sheep39, nonetheless, it is important to emphasize that the data of the present review and from others39, average daily gain were closer of 100 g (5 % higher on average), compared to higher rates of gain.
Energy requirements of grazing sheep
In tropical regions, sheep production systems are usually mixed, where in most cases, animals (ewes mainly) are maintained grazing with or without supplementary feed. Feeding is based on the use of native and introduced grasses and shrubs; sheep farms have low production and profitability parameters and low rate of adoption of new technologies. For that reason estimation of nutrient requirement of grazing sheep must be of paramount importance. However, there are few reports of experiments where nutrient requirements of grazing sheep have been determined. In this context40, with Rambouillet × Pelibuey sheep recently weaned of 13.5 kg grazing Buffel (Cenchrus ciliaris) grass, found an energy requirement for maintenance of 359 kJ ME/kg BW0.75/d. On the other hand7 considering a km of 0.66, reported a MEm of 470 kJ ME/kg, therefore NEm was 310 kJ/kg BW0.75. Similarly, reported that in lambs of 3 to 4 mo old (castrated males) of the Santa Inês breed of 15 to 30 kg live weight grazing buffel grass had a requirement of 18.2 kJ ME/g weight gain in lambs of 15 kg. In lambs of 20 kg, the requirement was 24 kJ, in lambs of 25 kg the requirement was 30 kJ and in animals of 30 kg it was 35 kJ. The estimated kg value was 0.42 for all weights evaluated.
Empty body weight (EBW)
Marcondes et al36 suggested that the first step in the determination of energy requirements of ruminants is the conversion of shrunk BW (SBW) to EBW. Also, some authors mention30, that the energy concentration in the body has usually been expressed as a function of EBW rather than SBW because interference by the gastrointestinal content is completely eliminated. The EBW is equivalent to SBW minus the weight of the gastrointestinal contents. SBW is also defined as 96 % of full BW (kg) and defines EBW as: EBW = 0.85 × SBW (kg)12,16,30.
Nonetheless, to determine the EBW, sheep have to be slaughtered; for this reason, regression equations have been developed to estimate EBW from BW or SBW and include this information and thus contribute to updating with the data for estimation of some parameters required by nutritional models such as SRNS in order to predict the performance of hair sheep breeds11,32.
Based on data reported8,22,26,30,34,38, a linear regression equation was fitted.
(Equation 1): EBW= -1.80(±0.59***) + 0.89 (±0.02***) × SBW (R2= 0.98; MSE= 1.669; RSD= 1.292; P<0.0001; n= 51).
It was found that gastrointestinal fill was 10 % and the EBW was 90 % of BW in male animals. The values found in the present work as regard to BW corresponding to EBW were higher to those reported in the literature16,32. Also it was found that the relation BW/EBW was on average 1.23 for males.
Regarding females, in adult Pelibuey ewes at different physiological stages the weight of the gastrointestinal content was approximately 19 % of SBW11. Recently, (Chay-Canul, unpublished data) used a data set of 28 adult Pelibuey ewes with different BW and body condition score and when analyzed, the data conformed an equation:
(Equation 2): EBW= -3.82 (±0.93***) + 0.92 (±0.02***) × SBW (R2= 0.96, MSE= 2.183, RSD= 1.477, P<0.0001; n= 71).
The EBW corresponded to 92 % of BW. Moreover, the relation BW/EBW was on average 1.22 for ewes.
Body composition and its relationship with energy requirements
In order to estimate nutrient requirements it is important to know body composition and weight gain of sheep because these are directly related. Fernandes et al41 suggested that knowledge of body composition of the animals is of great relevance in studies of animal nutrition to determine nutrient requirements. Costa et al21 and Maia et al19 reported that the first step for determining nutritional requirements is to measure the body composition of the sheep, which may be obtained by direct or indirect methods. Although the direct determination of body composition by grinding and analyzing all body tissues is the most reliable method, it is expensive, time consuming, and laborious.
Sheep body composition is an important factor when determining nutritional requirements, since the body is basically composed of water, protein, fat and minerals, in proportions that vary according to breed, age, rate of growth, sex and nutrition, among others34.
In Morada Nova lambs weighing 15.23 to 25.43 kg, reported that the body composition (% EBW) varied from 70.14 to 64.61 % water, 18.14 to 18.17 % crude protein, 6.7 to 12.1 % fat and 7.28 to 9.50 MJ/kg EBW8. Those authors also reported that the concentration of crude protein was reduced from 181.76 to 178.74 g/kg EBW when the BW of animals increased from 15 to 25 kg. Others34, informed that the energy and fat contents of the EBW increased from 6.86 MJ/kg and 79.38 g/kg EBW, to 8.83 MJ/kg and 123.73 g/kg of EBW, respectively, as the BW of the animals increased from 15 to 30 kg; a quadratic effect was also observed for the concentrations of water and fat with increasing EBW and the percentage of protein showed a tendency to decrease linearly, representing a decrease of 0.10 percentage points for each kilogram increase in EBW.
In Santa Inês lambs22, reported that the energy and fat contents of the EBW of the sheep increased from 7.99 MJ/kg and 85.16 g/kg of EBW, respectively, to 11.63 MJ/kg and 221.23 g/kg, as the BW increased from 15 to 30 kg; they also observed a quadratic effect for the concentrations of water, fat, and energy with increasing EBW and informed that the percentage of crude protein showed a tendency to decrease linearly, representing a decrease of 0.12 percentage points for each kilogram increase in EBW, from 15 to 30 kg. Those authors, concluded that the net energy requirement for EBW gain increased with increasing body weight, due to a parallel increase in the quantity of fat deposited per kilogram gained. Correspondingly, some authors38, found that the crude protein content of the body decreased but fat and energy body content increased as the EBW increased from 15 to 45 kg. Similar results7 mention that the positively DM content in the EBW from 31.15 to 35.18 and to 36.19 %. However, the crude protein content in the EBW decreased with supplementation (P<0.05). This can be explained by the higher BW gain and fat deposition with the increase in supplementation level. The energy content in the EBW ranged from 6.23 to 8.66 MJ/kg EBW. The crude protein concentration decreased from 212 to 180 g/kg EBW when the body weight increased from 15 to 30 kg. The fat contents in 15 to 30 kg BW lambs ranged from 17.3 to 103.2 g/kg EBW. These authors concluded that the protein requirement decreased and the energy requirement increased with the increase in body weight.
Galvani et al30 found that fat concentration in the gain (g/kg EBW gain), increased with an increase in the BW of the lambs and that the amount of crude protein in the gain was not affected by slaughter weight. Pereira et al26 with Brazilian Somali lambs, reported that the animal’s energy and EBW fat contents increased from 11.20 MJ/kg and 208.54 g/kg to 13.54 MJ/kg and 274.95 g/kg of EBW, respectively, as the BW increased from 13.0 to 28.70 kg.
Using the data obtained in the present review, the body composition of hair sheep was plotted against the EBW, and three equations were fitted to predict body composition (Figure 1). The equations fitted were:
Equation (3): % Water= 72.881 (±1.022***) - 0.385 (±0.044***) × EBW (R2= 0.67; MSE= 5.558; RSD= 2.357; P<0.0001; n= 39).
Equation (4): % Fat= 3.62 (±1.22***) + 0.460 (±0.05***) × EBW (R2= 0.67; MSE= 7.929; RSD= 2.815; P<0.0001; n= 39).
Equation (5): Energy (MJ/kg EBW)= 3.322 (±1.108***) + 0.449 (±0.098***) ×EBW -0.006 (±0.002***) ×EBW2 (R2= 0.71; MSE= 0.976; RSD= 0.988; P<0.0001; n= 39). Nonetheless, for body crude protein and ash, no equations were adjusted.
General conclusions and implications
There are few studies available concerning the assessment of the nutrient requirements of hair sheep. Those studies show great variation regarding the energy requirements for ewes, being the average MEm 419 ± 129 kJ/kg BW0.75 and for the male 388 ± 123 kJ/kg BW0.75. The efficiency of ME utilization for maintenance (km ) and gain (kg ) were 0.66 ± 0.02 and 0.42 ± 0.04, respectively.
Some authors have reported that such requirements are in some cases higher compared to those previously reported in North American and European energy systems15,23,24,42 for wool breeds. However, other authors have reported that these requirements are lower compared to those systems. Information regarding ME requirements for maintenance and production and the variation existing in such estimates is scarce for the breeds of hair sheep.
It has been reported that it is likely that differences exist in the ME requirements for maintenance in ewes of different breeds and type (hair vs wool); if this is so, then there would be an opportunity to select those ewes with the lowest ME requirement for maintenance and with this, increase the efficiency of mutton production. Thus, it is important to determine the energy requirement of different breeds of hair sheep and the efficiency with which they utilize ME absorbed from the gastrointestinal tract. To unravel some of the questions above, it will be required to build a calorimetric unit in Mexico with the appropriate infrastructure and equipment to measure indirectly heat arising from the different sources within the animal. This facility has not necessarily be extremely expensive, the head-boxes for calorimetric measurements in goats at the “Kika de la Garza” Research Institute in Langston University, United States, are a good example of a low-cost, efficient, calorimetric unit for small ruminants.
This review attempted to identify potential areas of research where fundamental knowledge is required in order to increase energetic efficiency of hair sheep production in the tropical regions of Latin America. It seems apparent that emphasis must be given to experimental approaches which allow identification of animals with the lowest residual feed intake and energy requirement for maintenance as well as the highest efficiency of ME utilization for maintenance, weight gain, pregnancy and lactation. The knowledge of those values may help nutritionists to formulate practical rations with a better scientific base than at present. The identification and incorporation of the most efficient sheep in production systems may eventually lead to an increase in productivity and profitability for farmers in developing countries of the tropical regions of the world.
Literatura citada
1. López-Carlos MA, Ramírez RG, Aguilera-Soto JI, Aréchiga CF, Rodríguez H. Size and shape analyses in hair sheep ram lambs and its relationships with growth performance. Livest Sci 2010;(131):203-211. [ Links ]
2. Cantón GCJ, Bores QR, Baeza RJ, Quintal FJ, Santos RR, Sandoval CC. Energy retention of F1 Pelibuey lambs crossed with breeds for meat production. J Anim Vet Adv 2009;8(12):2655-2661. [ Links ]
3. Cantón J, Moguel Y, Castellanos A. Estimación del requerimiento energético de mantenimiento del borrego Pelibuey en clima tropical. Téc Pecu Méx 1995;(33):66-73. [ Links ]
4. Silva A, da Silva Sobrinho A, Trindade I, Resende K, Bakke O. Net requirements of protein and energy for maintenance of wool and hair lambs in tropical region. Small Rum Res 2003;(49):165-171. [ Links ]
5. Cabral LDS, Neves EMDO, Zervoudakis JT, Abreu JGD, Rodrigues RC, Souza AL, et al. Estimativas dos requisitos nutricionais de ovinos em condições brasileiras. Rev Bras Saúde Prod Anim 2008;9(3):529-542. [ Links ]
6. Duarte VF, Sandoval CA, Sarmiento LA. Empleo del modelo SRNS para predecir la ganancia de peso en ovinos machos Pelibuey en crecimiento. Arch Zootec 2009;58(224):671-681. [ Links ]
7. Silva AMA, Santos EM, Filho JMP, Bakke OA, Gonzaga NS, Costa RG. Body composition and nutritional requirements of protein and energy for body weight gain of lambs browsing in a tropical semiarid region. Rev Bras Zootec 2010;(39):210-216. [ Links ]
8. Gonzaga-Neto SA, da Silva-Sobrinho AG, de Resende KT, Zeola NMBL, de Azevedo-Silva AM, Marques CAT, et al. Composição corporal e exigências nutricionais de proteína e energia para cordeiros Morada Nova. Rev Bras Zootec 2005;(34):2446-2456. [ Links ]
9. Resende KT, Silva HGO, de-Lima LD, Teixeira IAMA. Avaliação das exigências nutricionais de pequenos ruminantes pelos sistemas de alimentação recentemente publicados. Rev Bras Zootec 2008;37(Supl esp):161-177. [ Links ]
10. Vieira PAS, Pereira LGR, Azevêdo JAG, Neves ALA, Chizzotti ML, dos Santos, et al. Development of mathematical models to predict dry matter intake in feedlot Santa Ines rams. Small Rumin Res 2013;112(1):78-84. [ Links ]
11. Chay-Canul AJ, Espinoza-Hernández JC, Ayala-Burgos AJ, Magaña-Monforte JG, Aguilar-Pérez CF, Chizzotti ML, et al. Relationship of empty body weight with shrunken body weight and carcass weights in adult Pelibuey ewes at different physiological states. Small Ruminant Res 2014;(117):10-14. [ Links ]
12. Tedeschi LO, Cannas A, Fox DG. A nutrition mathematical model to account for dietary supply and requirements of energy and nutrients for domesticated small ruminants: The development and evaluation of the Small Ruminant Nutrition System. Small Ruminant Res 2010;(89):174-184. [ Links ]
13. Chay-Canul AJ, Ayala-Burgos AJ, Kú-Vera JC, Magaña-Monforte JG, Tedeschi L. O. The effects of metabolizable energy intake on body fat depots of adult Pelibuey ewes fed roughage diets under tropical conditions. Trop Anim Health Prod 2011;(43):929-936. [ Links ]
14. Chilliard Y, Bocquier F, Doreau M. Digestive and metabolic adaptations of ruminants to undernutrition, and consequences on reproduction. A review. Reprod Nutr Dev 1998;(38):129-150. [ Links ]
15. NRC. Nutrient requirements of small ruminants: Sheep, goats, cervids, and New World camelids, 6th ed. Washington, DC: National Academy Press; 2007. [ Links ]
16. Cannas A, Tedeschi LO, Fox DG, Pell AN, Van Soest PJ. A mechanistic model for predicting the nutrient requirements and feed biological values for sheep. J Anim Sci 2004;(82):149-169. [ Links ]
17. Duarte VF, Sandoval CA, Sarmiento LA. Evaluación del modelo CNSPS-S para predecir el crecimiento del borrego Pelibuey. Rev Cient-Fac Cien V FCV-LUZ 2008;(18):296-304. [ Links ]
18. Regadas-Filho JGL, Pereira ES, Villarroel ABS, Pimentel PG, Fontenele RM, Costa MRGF, et al. Efficiency of metabolizable energy utilization for maintenance and gain and evaluation of Small Ruminant Nutrition System model in Santa Ines sheep. Rev Bras Zootec 2011;(40):2558-2564. [ Links ]
19. Maia ISG, Pereira ES, Pinto AP, Mizubuti IY, de Azambuja-Ribeiro EL, et al. Consumo, avaliação do modelo Small Ruminant Nutrition System e predição da composição corporal de cordeiros Santa Inês alimentados com rações contendo diferentes níveis de energia. Semina: Sci Agric 2014;35(4):2579-2596. [ Links ]
20. Oliveira AP, Pereira ES, Pinto AP, de Azevêdo-Silva AM, de Souza-Carneiro M S, Mizubuti IY. et al. Estimativas dos requisitos nutricionais e utilização do modelo Small Ruminant Nutrition System para ovinos deslanados em condições semiáridas. Semina: Sci Agric 2014;35(4):1985-1998. [ Links ]
21. Costa MRGF, Pereira ES, Pinto AP, de Azevêdo Silva AM, de Medeiros AN, et al. Prediction of body chemical composition of Morada Nova lambs using the composition of ribs section between 9th and 11th. Semina: Sci Agric 2014;35(4):2019-2032. [ Links ]
22. Regadas-Filho JGL, Pereira ES, Pimentel PG, Villarroel ABS, Medeiros AN, Fontenele RM. Body composition and net energy requirements for Santa Ines lambs. Small Ruminant Res 2013;(109):107-112. [ Links ]
23. ARC. The nutrient requirements of ruminant livestock. Agr Res Council. London: Gresham Press; 1980. [ Links ]
24. AFRC. Technical Committee on Responses to Nutrients. Energy and protein requirements of ruminants. CAB International, Wallingford, UK; 1993. [ Links ]
25. Cannas A, Atzori AS, Teixeira IAMA, Sainz RD, Oltjen JW. The energetic cost of maintenance in ruminants: from classical to new concepts and prediction systems. In: Crovetto M editor. Energy and protein metabolism and nutrition. Netherlands: Wageningen Academic Publishers; 2010;531-542. [ Links ]
26. Pereira ES, Fontenele RM, Silva AM, Oliveira RL, Ferreira MR, Mizubuti IY, et al. Body composition and net energy requirements of Brazilian Somali lambs. Ital J Anim Sci 2014;13(4):880-886. [ Links ]
27. Reynolds CK, Crompton LA, Mills JAN. Improving the efficiency of energy utilization in cattle. Anim Prod Sci 2011;(51):6-12. [ Links ]
28. Ferrell CL and Oltjen JW. ASAS Centennial Paper: Net energy systems for beef cattle- Concepts, application, and future models. J Anim Sci 2008;(86):2779-2794. [ Links ]
29. Tolkamp BJ. Efficiency of energy utilization and voluntary feed intake in ruminants. Animal 2010;(4):1084-1092. [ Links ]
30. Galvani DB, Pires AV, Susin I, Gouvêa VN, Berndt A, Chagas LJ, et al. Energy efficiency of growing ram lambs fed concentrate-based diets with different roughage sources. J Anim Sci 2014;92(1):250-263. [ Links ]
31. Chay-Canul AJ, Ayala-Burgos AJ, Kú-Vera JC, Magaña-Monforte JG, Ferrell CL. Metabolizable energy intake and changes in body weight and body condition of Pelibuey ewes fed three levels of roughage diets under tropical conditions. Trop Subtrop Agroecosyt 2011;(14):777-786. [ Links ]
32. Duarte F, Sandoval-Castro CA, Sarmiento-Franco LA, Tedeschi LO, Santos-Ricalde RH. Energy and protein requirements of growing Pelibuey sheep under tropical conditions estimated from a literature database analyses. Trop Subtrop Agroecosyt 2012;15(1):97-103. [ Links ]
33. Chávez RG, Castellanos RA, Velásquez MP. Producción de las ovejas Pelibuey pre y posparto alimentadas con diversos aportes nutricionales. Tec Pecu Mex 1995;(33):183-191. [ Links ]
34. Costa MRGF, Pereira ES, Silva AMA, Paulino PVR, Mizubuti IY, Pimentel PG, et al. Body composition and net energy and protein requirements of Morada Nova lambs. Small Ruminant Res 2013;114(2):206-213. [ Links ]
35. Tedeschi LO, Fox DG, Carstens GE, Ferrell CL. The partial efficiency of use of metabolisable energy for growth in ruminants. In: Crovetto M, editor. Energy and protein metabolism and nutrition. Netherlands: Wageningen Academic Publishers; 2010:519-529. [ Links ]
36. Marcondes MI, Chizzotti ML, Valadares-Filho SC, Gionbelli MP, Paulino PVR, Paulino MF. Energy requirements of Zebu beef cattle. In: Valadares FS, et al editors. Nutrient requirements of Zebu beef cattle, BR. Corte. 2nd ed. Federal University of Vicosa, MG; UFV, DZO, Brasil. 2010;81-106. [ Links ]
37. Chizzotti ML, Tedeschi LO, Valadares-Filho SC. A metaanalysis of energy and protein requirements for maintenance and growth of Nellore cattle. J Anim Sci 2008;86(7):1588-1597. [ Links ]
38. Oliveira NA, Pérez JRO, Carvalho PA, Paula OJ, Baião EAM. Composição corporal e exigências líquidas em energia e proteína para ganho de cordeiros de quatro grupos genéticos. Ciênc Agrotéc 2004;(28):1169-1176. [ Links ]
39. Solís RG, Castellanos RA, Velázquez MA, Rodríguez GF. Determination of nutritional requirements of growing hair sheep. Small Ruminant Res 1991;(4):115-125. [ Links ]
40. Ramírez RG, Huerta J, Kawas JR, Alonso DS, Mireles E, Gómez MV. Performance of lambs grazing in a buffelgrass (Cenchrus ciliaris) pasture and estimation of their maintenance and energy requirements for growth. Small Ruminant Res 1995;(17):117-121. [ Links ]
41. Fernandes MHMR, Resende KT, Tedeschi LO, Fernandes-Jr JS, Teixeira IAMA, Carstens GE, et al. Predicting the chemical composition of the body and the carcass of 3/4 Boer x 1/4 Saanen kids using body components. Small Ruminant Res 2008;(75):90-98. [ Links ]
42. NRC. Nutrient requirements of sheep. 6th ed. Washington, DC: National Academy Press; 1985. [ Links ]
Received: January 23, 2015; Accepted: April 17, 2015