Net requirements of calcium, phosphorus, magnesium, and sulphur for growth of nondescript breed hair lambs of different sex classes in the Brazilian semiarid conditions Ivonete Ferreira da Silva, Rafael Torres de Souza Rodrigues, Mário Adriano Ávila Queiroz, Mario Luiz Chizzotti, et al. Tropical Animal Health and Production ISSN 0049-4747 Trop Anim Health Prod DOI 10.1007/s11250-016-1035-4
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Author's personal copy Trop Anim Health Prod DOI 10.1007/s11250-016-1035-4
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Net requirements of calcium, phosphorus, magnesium, and sulphur for growth of non-descript breed hair lambs of different sex classes in the Brazilian semiarid conditions Ivonete Ferreira da Silva 1 & Rafael Torres de Souza Rodrigues 2 & Mário Adriano Ávila Queiroz 1 & Mario Luiz Chizzotti 3 & Marcus Antonio Zanetti 4 & José Aparecido da Cunha 4 & Karina Costa Busato 2
Received: 24 November 2015 / Accepted: 29 February 2016 # Springer Science+Business Media Dordrecht 2016
Abstract The aim of this study was to determine the net requirements of calcium (Ca), phosphorus (P), magnesium (Mg), and sulphur (S) for weight gain of non-descript breed hair lambs (NDBL) of different sex classes reared under Brazilian semiarid conditions. Sixty NDBL (20 intact males, 20 castrated males, and 20 females), with an average initial body weight of 18.1 ± 0.4 kg and average age of 5 months were used. The macromineral requirements were determined by the differences in body composition through comparative slaughter direct method. The animals were confined for 58 days, and the average fasting body weight (FBW) and average daily gain (ADG) of lambs fed ad libitum were 29.2 ± 0.6 and 0.19 ± 0.01 kg, respectively. The net requirements of macrominerals for gain of NDBL did not differ between sex classes (P > 0.05), and ranged from 1.83 to 1.46 g/day of Ca, 1.21 to 1.01 g/day of P, 37 to 30 mg/day of Mg, and 0.31 to 0.28 g/day of S, for lambs with an ADG of 0.200 kg and 15 or 30 kg of FBW, respectively (P < 0.05). The N to S net ratio reduced and increased, respectively, as the body weight and ADG increase. The net requirements of Ca, P, Mg, and S for
* Rafael Torres de Souza Rodrigues
[email protected]
1
Department of Animal Science, Universidade Federal do Vale do São Francisco—UNIVASF, Petrolina, Pernambuco 56300-990, Brazil
2
Department of Animal Science, Universidade Federal de Lavras—UFLA, P.O. Box 3037, Lavras, Minas Gerais 37200-000, Brazil
3
Department of Animal Science, Universidade Federal de Viçosa—UFV, Viçosa, Minas Gerais 36570-900, Brazil
4
Department of Animal Science and Food Engineering, Universidade de São Paulo—USP, Pirassununga, São Paulo 13635-900, Brazil
gain of NDBL slaughtered young and at the same age did not differ between sex classes and decreased as the body weight increased. The net requirements for gain of Ca and P were similar to those recommended by NRC (2007). Keywords Gender . Mineral . Nutrient balance . Semiarid . Sheep
Introduction Mineral nutrition should be a priority in small ruminant management as animal production, reproduction, immunity, and survival are all affected when a mineral is outside the adequate range (NRC 2007). Therefore, the determination of mineral requirements aims to prevent feeding excessive levels in the diet, subsequently, reducing the costs of production and the excretion of inorganic elements in the environment without negatively impacting on animal performance (Chizzotti et al. 2009). Nevertheless, the diets formulated for sheep in Brazil are based on information recommended by international committees on animal nutrition. Requirements in the current study were, therefore, established based on the studies with different breeds, feeds, and climates than those found in Brazil. Mineral requirements may be influenced by sex class, genotype, age, and physiological status of the animals. These factors affect body composition (Teixeira et al. 2013), because as mineral content changes between tissues, differences in body composition can also affect mineral retention (Chizzotti et al. 2009). Despite this, the feed systems do not consider the differences between breeds and sex classes to estimate mineral requirements in sheep. Furthermore, the comparative slaughter method was little used in sheep to study
Author's personal copy Trop Anim Health Prod
mineral requirements among sex classes (Bellof and Pallauf 2007). The comparative slaughter technique is a direct method to determine body composition. The animals are divided into two groups; one of them is slaughtered at the beginning of the experiment. The remaining animals are divided into other groups that are fed with different energy levels to achieve a range of variation in slaughter weight and body composition. The difference between the initial and final body composition corresponds to weight gain composition (Lofgreen and Garrett 1968). The direct method has been described as the more accurate form to assess the body composition (ARC 1980). Non-descript breed hair lambs (NDBL) originated from random mating between native and exotic breeds, and by several years of natural selection. These animals are well adapted to the semiarid conditions of the Brazilian Northeast and represent the majority of the flock in this region, which also has the largest sheep flock of the country (Rodrigues et al. 2014). Aside from its importance, NDBL have not been used in researches to determine mineral requirements of sheep in Brazil. Also, the values found in Brazilian studies differed from the values estimated by the main feed systems used for sheep (Gonzaga Neto et al. 2005; Cabral et al. 2008; Teixeira et al. 2013). Additionally, research to determine the net requirements for sulphur for weight gain in lambs using comparative slaughter has not been reported in the literature. The aim of the current study was to determine the net requirements of calcium (Ca), phosphorus (P), magnesium (Mg), and sulphur (S) for weight gain of NDBL of different sex classes reared under Brazilian semiarid conditions.
Materials and methods The experiment was conducted at the Universidade Federal do Vale do São Francisco—UNIVASF, Petrolina, Brazil, latitude 09° 19′ 28′′ S and longitude 40° 33′ 34′′ W. Throughout the experimental period, the temperature ranged from 20.6 to 31.4 °C and the relative humidity ranged from 40.0 to 84.9 %. The experimental procedures performed were approved by the bioethics committee for animal experimentation of UNIVASF (0010/040713). Sixty NDBL of three sex classes (20 intact males, 20 castrated males, and 20 females), with an average initial body weight of 18.1 ± 0.4 kg and an average age of 5 months were used. The lambs were subjected to a 30-day adaptation period to the facilities and the experimental diet. During this time, they were also weighed, identified, and treated against parasites. Following the adaptation period, a reference group of 15 animals (five of each sex class) was formed. These animals were slaughtered at the beginning of the experiment to estimate the initial body composition and the initial empty body
weight (EBW) of the final slaughter group. The remaining 45 lambs were distributed in a completely randomized design. Five animals of each sex class were assigned to one of the following feeding levels: ad libitum feeding and 70 or 80 % of feed restriction (Rodrigues et al. 2014). The feed restriction was calculated according to the intake of the last week of the adaptation period. The diet, composed of chopped elephant grass as fed (Pennisetum purpureum) and a ground corn and soybean meal-based concentrate at a roughage to concentrate ratio of 40:60, was offered as a total mixed ration twice a day, at 8 and 15 h (Tables 1 and 2). The animals were housed in individual covered stalls, with concrete floor and equipped with drinking and feeding troughs. Approximately 20 % of leftovers were allowed for the sheep fed ad libitum. The amount of feed supplied and the leftovers were weighed daily and recorded to calculate intake. Samples of the concentrate, elephant grass, and leftovers were collected and frozen at −20 °C. Analysis of chemicals in the feeds and leftovers were performed according to AOAC (1990). The animals were weighted at the beginning of the experiment and every 29 days to determine the average daily gain (ADG). The experimental period lasted for 58 days, after which all animals were slaughtered. Before slaughter, animals were fasted for 16 h and, subsequently, weighed to obtain the fasting body weight (FBW). The gastrointestinal tract was Table 1
Proportion of ingredients and composition of the diet
Ingredients
g/kg of dry matter
Elephant grass Ground corn Soybean meal Sodium chloride Commercial premixa Urea Composition Dry matter Organic matter Ash Crude protein Ether extract Neutral detergent fiber Non-fibrous carbohydrates Digestible energy Metabolizable energy
400 286 295 5 11 3
a
638 927 73 179 29 379 339 2.4b 1.9b
Contains 240 g Ca/kg; 71 g P/kg; 28.2 g K/kg; 20 g S/kg; 20 g Mg/kg; 30 mg Co/kg; 400 mg Cu/kg; 250 mg Fe/kg; 1,350 mg Mn/kg; 15 mg Se/ kg; 1,700 mg Zn/kg; 40 mg I/kg; 10 mg Cr/kg; 710 mg F/kg; 135,000 IU vitamin A/kg; 68,000 IU vitamin D3/kg, and 450 IU vitamin E/kg
b
Mcal/kg of dry matter
Author's personal copy Trop Anim Health Prod Table 2 Values of calcium (Ca), phosphorus (P), magnesium (Mg), sulphur (S), and nitrogen (N) in the ingredients and diet Ingredients
Caa
Pa
Mga
Sa
Na
Elephant grass
1.28
1.12
1.44
0.61
3.23
Ground corn Soybean meal
0.08 0.94
0.80 1.90
0.34 0.79
0.85 1.20
3.66 21.71
Commercial Premix
2.64
0.8
0.22
0.22
–
Diet
4.94
3.90
2.79
2.94
28.6
a
g/kg of dry matter
removed and washed. The EBW was obtained by the sum of the carcass, hide, head, feet, blood, tail, internal organs, and cleaned gastrointestinal tract weights. The initial EBW of the animals slaughtered at the end of the experiment was estimated by the ratio of the EBW to the FBW of the reference animals. The carcasses were split into two longitudinal halves. The left half carcass was separated into bones and soft tissues (muscles, fat, and tendons), which were cut into small pieces and separately ground in an industrial meat grinder. The viscera, blood, head, and feet of each animal were ground together. The hide was sampled and cut into small pieces. Samples were dried at 105 °C for 80 h, and then partially deffated by successive washings with petroleum ether (Kock and Preston 1979). Thereafter, the samples were ground in a ball mill (TE350, Tecnal, Piracicaba, Brazil). The minerals were quantified by inductively coupled plasma optical emission spectrometry (ICP-OES). The mineral content retained in the body was estimated by logarithmic regression equations according to the following statistical model: Y = a + b × X + e, where: Y = logarithm of the mineral content retained in the empty body; a = intercept; b = slope; X = logarithm of the EBW; and e = random error (ARC 1980). The logarithmic regression equations were derived to calculate the net requirements of minerals according to the following model (ARC 1980): Y = b × 10a × X(b-1), where: Y = net requirement of the mineral for gain; a and b = intercept and slope, respectively, of the prediction equation for mineral content of the body; and X = EBW. The EBW and Table 3 Macromineral concentrations in the empty body of lambs of different sex classes submitted to different feed levels
Item (g/kg EBW)
Calcium Phosphorus Magnesium Sulphur
EBG were estimated from the FBW and ADG, respectively, through a linear regression analysis between these variables. Statistical analyzes were performed using the SAS (2003) computer software. The PROC GLM procedure was used to obtain the regressions. The regression coefficients obtained for the different sex classes were compared using the solution tool at the level of significance of 5 %. The effects of feeding level and sex class on performance and mineral concentration were analyzed using the PROC GLM procedure, at the level of significance of 5 %, and according to the following statistical model: Y = μ + α + β + αβ + e, where: μ = mean; α = effect of feed level; β = effect of sex class; αβ = interaction between feed level and sex class; and e = random error.
Results There was no effect of sex class or interaction between sex class and feeding level on performance (P > 0.05). Conversely, there was an effect of feeding level on performance (P < 0.05). The dry matter intake, ADG, and FBW ranged from 0.23 to 1.17 kg/day, −0.05 to 0.190 kg/day, and 15.5 to 29.2 kg, in the 80 % of feed restriction and ad libitum intake treatments, respectively. The full performance and intake data of the animals used here can be seen in Rodrigues et al. (2014). The proportion of soft tissue and the bone in the carcass weight and the proportion of the internal fat (IF) in the EBW were not affected by sex class or interaction between sex class and feeding level (P > 0.05). However, ad libitum-fed animals had higher proportion of soft tissue and lower proportion of the bones in the carcass weight (P < 0.05) than the average values showed by restrictedfed sheep (76 vs. 66 % and 21.4 vs. 32.0 %, respectively). Moreover, ad libitum-fed lambs had a higher proportion of IF in the EBW (P < 0.05) than the average value of the restricted-fed animals (1.63 vs. 0.21 %). Neither sex class nor interaction between sex class and feeding level had any effect on the concentrations of Ca, P, Mg, and S in the empty body (P > 0.05). However, the
Sex classes
Feed level
IM
CM
F
AL
1.18
1.19
1.22
1.00b
0.75 0.02 0.16
b
0.71 0.02 0.16
0.75 0.02 0.16
0.64 0.02 0.16
Probability
30
20
SEM
S
F
S×F
1.22a 0.74a 0.02 0.16
1.37a 0.82a 0.02 0.17
0.092 0.046 0.002 0.014
0.81 0.42 0.56 0.80
