Feeding to the limits: efficient early weaning of lambs on solid feed at four weeks

C Milis, A Seidavi¹, V Tufarelli², M Ahmadi³, S Milioudis⁴, A Hatzikas⁴ and D Liamadis⁴

Ministry of Rural Development and Foods, Greece
milischrysostomos@gmail.com
¹ Department of Animal Science, Rasht Branch, Islamic Azad University, Rasht, Iran
² Department of DETO, Section of Veterinary Science and Animal Production, University of Bari ‘Aldo Moro’, Valenzano, Bari, Italy
³ Department of Animal Science, Ilam Branch, Islamic Azad University, Ilam, Iran
⁴ Aristotle University of Thessaloniki, Department of Animal Nutrition, Greece

Abstract

One 2x3 factorial experiment (two weaning ages x 3 rations differing in energy level) was carried out in order to examine the effect of the weaning age (30 or 45 days) and the dietary energy level (12.0, 10.8 and 9.9 MJ/kg DM) on average daily live weight gain (ADG), feed conversion ratio (FCR), carcass quality and growth rate of the total volume and weight of quadrolocular stomach. A second trial to evaluate the effects of protein source on early weaned lambs was performed. Lambs can be weaned at an age of 30 d instead an age of 45 d without significant effect on production parameters. Amino acid (ΑΑ) profile of the diet proved critical, since the addition of rumen protected lysine (first limiting AA) significantly improved FCR. Sorter weaning age and high fiber content of the ration affected positively the weight of the stomach, but this was not positively correlated with growth performance. Therefore, the most crucial factors at early weaning, inclusively on solid feed, is the palatability, energy density, CP/ME ratio, and AA profile of the diet.

Keywords: energy density, protein quality, palatability

Introduction

Weaning age of the lambs plays catalytic role to the amount of milk available to be traded. Early weaning of lambs is feasible without any problems on productivity and carcass quality traits at 42 days of age (Galvani et al 2014). Dietary energy level is the most important factor at early weaning (Mahgoub et al 2000), affecting positively feed conversion ratio (FCR) and average daily gain (ADG). Extreme early weaning on milk replacers is feasible on d 1 (Lanza et al 2006) but with adverse effects on meat quality. Meanwhile, high energy density of milk replacer positively affects liver and kidney weights as though as productivity traits (ADG, FCR), indicating that internal organ growth is relating with productivity traits. Additionally, Chai et al (2015) reported that weaning on milk replacers and creep feeding is feasible at 10 d of age, whilst shorter age of early weaning boosted creep feed intake, leading to better growth and health later in life. Hence, two weaning ages of 30 d and 45 d were selected to test the scenario whether weaning, inclusively on solid feed, at four weeks of age is feasible and what is the optimum energy level of the ration to make this extreme scenario feasible. Three energy levels of 12.0; 10.8 and 9.9 ME/kg DM, respectively (MAFF 1990) were applied in a 2x3 factorial design and the parameters under study included productivity parameters (producer), carcass quality (consumer), and growth of quadrolocular stomach and internal organs related with metabolism of early weaned lambs (animal).

Lately, Danso et al (2014) have reported that protein to energy ratio of the diet in pre-weaning lambs is a key factor affecting productivity traits. Anyhow, this ratio was only significant concerning milk replacer composition and not solid feed (creep -pellet), probably due to low pellet feed intake, indicating that milk replacer negatively affects creep intake, and, in consequence, that solid feed intake is crucial for early weaning. Even though diet’s protein level has been taken into account in previous studies, the effect of the quality of protein has never been studied in lambs with immature rumen, having digestive system similarities with that of monogastric animals. Thus, a second trial was performed to evaluate the effects of the nature of main protein source (soybean meal vs maize gluten meal) differing in solubility and degradability (Milis et al 2007) and the quality of protein source (amino acid; AA profile) on growth performance of lambs weaned inclusively on concentrate feed at 4 weeks of age.

Materials and methods

Experimental design and procedure

Trial 1

Lambs were allocated into three groups and were fed individually, ad libitum, with three rations differing in crude fiber (CF) content (Table 1), and thus different energy level. Every group consisted by two subgroups which were different on weaning age (30 or 45 days). 24 male fattening lambs were used in a 2x3 factorial experimental design (2 weaning ages x 3 rations differing in energy level). Productive traits parameters were measured weekly. The animals were slaughtered at a fixed final body weight of 32 kg. Before slaughter the lambs were not feeding for 24 hours. Carcasses were weighed, without head, tail, testicles, bowels and legs (separation at wrist metatarsus and tarsus-metatarsus joints), suspended through the achilles tendon, and then chilled at 4 ^◦C for 24 h. The factors under study were: warm and cold carcass yield, kidney and channel fat, warm carcass yield without internal fat (%) and lean content of cold carcass without internal fat (%) (Lean content = 0.896 + 0.549 cold carcass weight – 0.086 J – 0.141 ^oC), and total volume and weight of quadrolocular stomach.

Trial 2

A second trial, in a 3x2 factorial design (3 sources of protein x two sexes) 30 early (28 days after birth) weaned lambs were used. Lambs were allocated into three groups of 10 animals (5 male and 5 female) each and were fed individually and ad libitum with three isocaloric-iso nitrogenous rations having a different source of protein, but the same digestibility (Milis and Liamadis 2008). The 1^st (SBM group) contained SBM 15%, wheat bran 8% and skimmed milk 6% as protein sources, the 2^nd (MGM group) maize gluten meal 8%, maize gluten feed 8% and skimmed milk 3%, and the 3^rd (MGM-L) the same protein sources as the 2^nd supplemented with rumen protected lysine (0.4%), calculated and considered as the first limiting AA in MGM group, in order to have the same lysine content as the SBM ration (Table 2). Daily feed intake was calculated as the difference between feed offered and refused. Body weights of lambs were recorded twice every week.

Chemical analysis

Chemical composition of the diets is shown in Tables 1 and 2. Feed samples were ground to pass through a 1 mm screen (AOAC, 2006; official method 950.02B). The dry matter (DM) was determined by drying in an oven (AOAC, 2006; official method 934.01). The crude protein (CP) was measured as Kjeldahl N × 6.25 (AOAC, 2006; official method 984.13). CF contents were determined according to AOAC (2006). For all the methods, measurements were made in triplicate and standards were included in each run of each method.

Statistical analysis

Data were analyzed in a complete randomized design using the GLM procedure of SAS (SAS Inst. Inc., Cary, NC). The CF level of the diet fed to lambs and weaning age was taken as the fixed effects in the model. The same procedure was applied in the second trial with fixed effect being protein source of the diet, and sex. Means were obtained by using the LS MEANS option of SAS, and differences among treatments were explored by using the Tukey test for multiple-comparison analysis. Differences were declared significant when p < 0.05 (Tables 3–5).

Results

Effect of weaning age and energy level of the ration on productive parameters and stomach development of early weaned lambs

ADG was not significantly affected by the weaning age (Table 3), but the high energy ration obtained better results (p<0.05; Table 4). FCR and lean content were increased by higher energy ration. Warm and cold carcass yield were affected only by the weaning age. Kidney and channel fat were not affected by the weaning age; but the lambs in HEL group had more kidney and channel fat than the other ones (p<0.05). Warm carcass without internal fat (%) and lean content of cold carcass without internal fat (%) were not significantly affected by the ration, but they were affected by the weaning age. Total volume of quadrolocular stomach was higher in 30 d weaning than the 45 d, and in LEL group compared to MEL. Total weight of quadrolocular stomach was, also, higher in the 30 d weaning lambs and in MEL group compared to HEL.

Effect of main protein source and amino acid profile of the ration on productive parameters of early weaned lambs

ADG of lambs in SBM group was higher (p<0.05; Table 5) compared to MGM. Feed intake in SBM group was higher compared to MGM and MGM-L. FCR was inferior to MGM group compared to SBM. Significant interaction between the two factors (protein x sex) was not observed.

Discussion

Early weaning of lambs has significant effect on DM intake (the earlier the highest), and in the same line, positively affects quandrolocular stomach volume and weight. It has been reported that early weaning positively affects internal organs (Chai et al 2015) related to metabolism (liver, pancreas). Probably, higher creep intake in early weaned lambs positively affects rumen development (Ghorbani et al 2007; Alvarez-Rodriguez et al 2010) and this leads to a greater growth rate (Chai et al 2015). Present study reveals that high fiber content (low energy ration) of the diet has positive effect on stomach development (Table 4), as though as age of weaning (the sorter the higher; Table 3) but this development is not positively correlated with FCR neither ADG. In the same line, Danso et al (2014) reported that feeding milk replacers plus creep compared to lambs suckling their dams, significantly increased growth performance and organ development of lambs, however, did not affect the efficiency of feed utilization. Nutrient digestibility and metabolism of lambs weaned at different ages varies as gastrointestinal development is affected due to weaning stress (Zhong et al 2014), but it may be possible for artificially-reared or ewe-reared lambs to have a similar gastrointestinal development (Chai et al 2015).

HEL ration had positive effect on growth rate irrespective weaning age. The weight of stomach of lambs fed the LEL ration was higher compared to that of HEL and MEL rations. Kidney and channel fat were higher in HEL group compared to MEL and LEL. This is in line with recent reports, stating that the body composition can be affected mainly on fat content when high energy level diets are fed (Cranston et al 2015; Wong et al 2018).

Interactions between weaning age and energy level of the ration were not found on carcass traits. According to Wong et al (2018), hot – carcass weight is not affected by weaning age, under different feeding rations, when lambs are slaughtered at a fixed weight.

The lambs in group MGM did not performed as well compared to group SBM, taking into account ADG. This parameter was affected by the lower feed intake of lambs fed MGM. It seems that the palatability of the diet is the most crucial factor for a successful early weaning. Lower feed intake could be attributed to undesirable flavor of MGM (Wu et al 1994). A new feeding index should be induced in feed composition tables reflecting palatability index.

Meanwhile, the addition of lysine (the first limiting AA in MGM group) in ration MGM-L had positive effect on FCR since group SBM and MGM-L, with better AA profile, had better FCR compared to group MGM. Additionally, SBM and MGM-L groups did not different in ADG, even though MGM-L group had lower DM intake in comparison with SBM group. Similar effect has been noticed on lactating ewes as well (Milis et al 2005).

The drop of ewe milk prices (appr. 0.7 euro/lt) has led the producers into financial exhaustion, because cost of production is higher than gross income. Since the cost of feeding is about 70% of total production cost, the only way to keep producers into business is to reduce feeding cost, or to increase end product production with the same cost. Since lambs weaned on milk replacers at 10 d perform as well (Chai et al 2015) compared to lambs suckling their dams, the most economical approach is to weaning lambs on milk replacers until 4 weeks and then feeding them with a high quality TMR.

Conclusions

• Lambs can be weaned at an age of 30 d instead of 45 d without effect on ADG, FCR and lean content.
  
  
• High energy content of the ration positively affects ADG and FCR.
  
  
• Earlier weaning age and high fiber level of the ration promote stomach development, but this is not positively correlated with growth performance.
  
  
• Palatability and AA profile of the diet are crucial factors for efficient early weaning of lambs.

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Received 4 June 2019; Accepted 8 June 2019; Published 1 September 2019

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