South African Mutton Merino Lambs Research Articles

The effects of age of castration on carcass characteristics, meat quality and fatty acid profile of finishing South African Mutton Merino lambs

This study compared the effect of either keeping South African Mutton Merino (SAMM) ram lambs intact, or castrated with age applicable methods on their carcass characteristics, meat quality and fatty acid composition of subcutaneous fat (SCF) and intramuscular fat (IMF). Ten lambs per treatment were castrated early at one week of age (EAR) with an elastrator band (4.4 kg ± 0.78 kg: mean ± SD), another 10 lambs at eight weeks of age (late castration - LAT) with a burdizzo (23.6 kg ± 2.26 kg: mean ± SD), whereas another ten lambs were left intact (CON). The two castration methods used were based on cost, ethical prescriptions and to mimic commercial operations. The lambs were housed individually in 30 pens (1.404 m2) for the duration of the study. Animals were housed on an elevated slatted wooden floor in the same metabolic building with an extractor fan to promote ventilation. At the start of the feeding trial, the age of the lambs was on average two and a half months with a live weight of 24.3 kg ± 4.10 kg (mean ± SD). The lambs were fed a standard commercial finishing diet for 67 days and slaughtered when they reached approximately 44.2 kg ± 6.35 kg (mean ± SD) live weight. After slaughter, carcass characteristics (cold carcass) and meat quality were evaluated. The left 3-rib cut was dissected (9th through 11th rib) and the muscle percentage for CON lambs was higher compared to both EAR and LAT lambs. Therefore, CON lambs produced leaner carcasses compared to EAR and LAT lambs. Castration status had no effect on meat Warner-Bratzler shear force (WBSF), consumer sensory analysis nor colour. For proximate composition, CON lambs had higher moisture compared to LAT lambs while LAT had higher dry matter compared to CON lambs. Both, EAR and LAT lamb’s meat had higher organic matter compared to CON lamb’s meat, but these differences were negligible. For IMF in the longissimus thoracic et lumborum muscle, CON lambs’ meat had higher total PUFA, α-linolenic acid, total PUFA n-6, linoleic acid, PUFA:SFA ratio and PUFA:MUFA ratio than meat from both EAR and LAT lambs. Eicosapentaenoic acid (EPA) and total PUFA n-3 were both higher for meat from CON lambs than LAT lamb’s meat, while palmitic acid and conjugated linoleic acid (CLA) were higher for EAR lamb’s meat than CON lamb’s meat and EAR lambs than LAT lamb’s meat, respectively. For SCF, CON lambs had higher heptadecenoic acid and linolelaidic acid than LAT lambs. The calculated atherogenicity index (AI) of SCF was higher for LAT lambs compared to CON lambs. Limited effects of castration age on the possible health benefits of SAMM lamb meat were proven in the current study. It is however suggested that for a higher production response and carcass muscle content, to either keep SAMM rams intact or at least postpone castration for as long as possible.

The Effect of Monensin vs. Neem, and Moringa Extracts on Nutrient Digestibility, Growth Performance, Methane, and Blood Profile of Merino Lambs.

Plant secondary compounds are potential rumen modifiers that can improve nutrient utilization in ruminant animals. This study evaluated the effect of Moringa (Moringa oleifera) and Neem (Azadirachta indica) leaf extracts on nutrient digestibility, growth performance, and enteric methane production in South African Mutton Merino lambs. Forty 4-month-old ram lambs with a mean body weight of 35 ± 2.2 kg were blocked by weight and from each block, lambs were randomly allocated into one of the following treatments: (i) diet only (fed a total mixed ration TMR-negative control), (ii) Monensin (fed TMR containing Monensin sodium, 15 mg/kg DM), (iii) Moringa (fed TMR, drenched with Moringa extract 50 mg/kg feed DM intake), and (iv) Neem (fed TMR, drenched with Neem extract 50 mg/kg DM intake). Extracts were administered via oral drenching at a concentration determined based on the previous week's feed intake. There were no differences in dry matter intake, average daily gain, feed conversion efficiency, digestibility, and nitrogen retention across the treatments. However, the extracts tended to reduce methane emitted both in g/head/day (p < 0.08) and g/ kg dry matter intake (p < 0.07). Extracts did not influence any of the blood metabolites in the ram lambs. Although the benefits of utilizing these medicinal plants as rumen modifiers under prolonged feeding conditions is justified, further evaluation is recommended to test Moringa and Neem leaf extracts at higher inclusion levels. Our research group is currently exploring a variety of phytogenic tools for the identification and standardization of key bioactive compounds linked to methane inhibition, in these leaf extracts.

Effect of Dietary Inclusion of Azadirachta indica and Moringa oleifera Leaf Extracts on the Carcass Quality and Fatty Acid Composition of Lambs Fed High Forage Total Mixed Rations.

Simple SummaryFeed additives based on medicinal plants, such as neem and moringa plant extracts, are used to mitigate rumen methane emissions, but data regarding their effects on lamb meat quality are scarce. This study investigated the effects of oral supplementation of neem and moringa leaf extracts on the carcass quality and meat fatty acid composition of lambs. Neem leaf extracts had no effect on carcass fat and meat fatty acid composition. Whereas, Moringa leaf extract improved the meat fatty acid composition of lambs compared to the monensin treatment. There is an increased interest in the use of medicinal plants as alternatives to antibiotic growth promoters and as agents for methane production mitigation. This study investigated the effects of Azadirachta indica and Moringa oleifera feed additives on the carcass and meat quality of lambs. Forty South African Mutton Merino lambs, weighing between 29 and 43 kg, were randomly assigned to four treatment groups (n = 10 lambs/treatment) and fed a basal total mixed ration (TMR) containing soybean meal (17%), yellow maize (28%), Alfalfa hay (20%), Eragrostis curvula hay (22.2%), molasses (6.0%), wheat offal (5%), urea (0.8%) and vitamin premix (0.5%) on a DM basis. The dietary treatments: TMR diet (control); TMR diet with A. indica leaf extract (A. indica leaf extract at a dosage of 50 mg per kg of feed: neem); TMR diet with M. oleifera leaf extract (M. oleifera leaf extract at a dosage of 50 mg per kg DM of feed: moringa); TMR diet with monensin (at a dosage of 50 mg monensin sodium per kg of feed: positive control). After an adaptation period of 10 days to the experimental conditions, the lambs from all treatment groups were fed ad libitum with the experimental diets. The lambs were slaughtered at a live weight of 60–65 kg after a 23 week trial period. The plant extract dietary additives had no significant effects on the carcass characteristics of the lambs. In comparison to monensin, supplementing with moringa leaf extracts resulted in a higher proportion of C18:1n9c (45.0% ± 0.57 vs. 40.5% ± 0.80; p < 0.05), total MUFAs (47.3% ± 0.66 vs. 42.6% ± 0.87; p < 0.05), and UFA:SFA ratio (1.01 ± 0.03 vs. 0.85 ± 0.03; p < 0.05), which may be beneficial for human health. Our results suggest that natural feed additives, such as A. indica and M. oleifera leaf extracts, can be included in lamb diets without compromising meat fatty acid composition. The negative economic impacts of such technologies on animal production and farm profitability should not be expected.

Wool production in Dohne Merino, Dormer, Merino and South African Mutton Merino lambs

In this study, the wool growth of Dohne Merino, Dormer, Merino and South African Mutton Merino (SAMM) lambs reared on a feedlot diet (10.62 MJ ME/ kg feed, 20.7% crude protein) was monitored from about two months old until the lambs were shorn as yearlings. The 100 cm2 patches on the left sides of the lambs were sheared monthly and the clippings were weighed to determine the wool growth rate. At approximately one year old, the lambs were shorn and the fleeces were weighed. A mid rib fleece sample was also retrieved from each lamb for quality analysis. Merino lambs presented the highest wool growth rates (12.943 g/day) and fleece weights (6.140 kg), whereas Dormer lambs exhibited the lowest values for these traits (8.487 g/day and 3.330 kg, respectively (P &lt;0.05)). The lack of differences between Dohne Merino (9.720 g/day and 4.671 kg) and SAMM (10.553 g/day and 4.158 kg) lambs for these wool growth rate and fleece weight traits was attributed to disparities in live weight (86.8 kg and 105.2 kg, respectively (P &lt;0.05), with heavier SAMM lambs offsetting the expected variations in fleece weight. Wool from Dohne Merino and Merino sheep had the finest fibre diameters (&lt;21 μm), followed by SAMM wool (22–23 μm), with Dormers producing coarse wool (&gt;27 μm). These results could be used as guidelines in sheep production to predict the income contribution of wool from these breeds.

Replacing urea with nitrate as a non-protein nitrogen source increases lambs' growth and reduces methane production, whereas acacia tannin has no effect

This study investigated the effect of urea or calcium nitrate with or without the inclusion of Acacia tannin extract on dry matter intake, nutrient digestibility, growth performance, and methane emission in growing lambs. Forty South African Mutton Merino lambs (95 days old, average body weight of 34.7 kg) were blocked by weight and sex and randomly allocated to four groups and fed diets supplemented with: urea (control); nitrate; urea + tannin; and nitrate + tannin. The concentration of urea and nitrate source in the diet was 10 g/kg and 32 g/kg, respectively, while the tannin was an extract of Acacia mearnsii added at 42 g/kg DM. Lambs were gradually adapted to the diets for 21 days after which growth performance was monitored for 60 days. At the end of the experimental period, methane was measured in open-circuit respiratory chambers, and digestibility was carried out inside metabolic cages. Dry matter and other nutrient intakes of lambs were not influenced by NPN source or the inclusion of tannin extract in the diet with the exception of the crude protein intake, which was higher (P ≤ 0.05) in lambs receiving urea-containing diets. Tannin inclusion reduced (P < 0.05) digestibility of dry matter, crude protein, neutral detergent fibre and acid detergent fibre of diets but did not affect methane emission of lambs. Tannin inclusion shifted N-excretion from urinary-N to faecal-N although overall N-retention was not affected. Tannin inclusion reduced acetate and increased propionate proportion in the urea-containing diet (P < 0.01), whereas, it had no such effect in the nitrate-containing diet. Higher (P ≤ 0.05) average daily gain and lower methane emission (P < 0.01) were recorded in lambs fed the nitrate-containing diets. In contrast, the inclusion of tannin reduced (P < 0.05) the average daily gain without any reduction in methane production. This study demonstrated that nitrate could be used as a source of non-protein nitrogen with the additional benefit of reducing enteric methane emission and improving the average daily gain of lambs. In contrast, tannin extract did not show any positive effect to justify its use under the dietary conditions of this study.

Growth performance and carcass characteristics of south african mutton merino fed diets with different levels of macadamia oil cake or baobab seed cake

This experiment was conducted to evaluate the effects of supplementing 10% or 15% of baobab seed cake (BSC) or macadamia oil cake (MOC) in fattening diets for lambs on feed intake, growth performance and carcass characteristics. Thirty-two lambs aged between 150 and 180 days were randomly allocated to 4 diets (10% MOC; 15% MOC; 10% BSC and 15% BSC diets) in an experiment arranged as a 2x2 factorial design and sex as a block. The results showed that there were significant protein source and inclusion level interactions on average daily feed intake, average daily gain, and total weight gain, warm and cold carcass mass. Males were significantly superior in all parameters except for feed conversion ratio, dressing percentage and rib-eye area. It was concluded that 10% MOC and 15% BSC can be incorporated in diets for fattening of growing South African Mutton Merino lambs without compromising on their growth performance and carcass characteristics.

Effects of different dietary inclusion levels of macadamia oil cake on growth performance and carcass characteristics in South African mutton merino lambs.

Growth performance and carcass characteristics of South African mutton merino fed graded levels of macadamia oil cake were assessed. A total of 60 South African mutton merino lambs were used in the experiment (initial live weight 25.0 ± 0.45kg). Five diets with different inclusion levels of macadamia oil cake (MOC) were formulated: T1 (0% MOC, control), T2 (5% MOC), T3 (10% MOC), T4 (15% MOC) and T5 (20% MOC). Effects of inclusion level of MOC on average daily gain (ADG) and average daily feed intake (ADFI) were not significant (P > 0.05). Effects of inclusion levels of MOC on feed conversion ratio (FCR) of sheep were significant (P < 0.05). Highest proportion (71.2%) of sheep in the study had a carcass fat classification of 2, followed by a proportion of 17.3% sheep with a carcass fat classification of 3 and lastly 11.5% sheep had carcass fat classification of 4. Warm and cold carcass mass, chest circumference, carcass length and dressing percentage were higher in sheep fed on 5% MOC compared to other treatment diets (0, 10, 15 and 20% MOC) (P < 0.05). Fat rib eye had a greater area in sheep fed on 5% MOC (P < 0.05). It was concluded that 5% MOC provided the best results in terms of carcass characteristic measurements in sheep.

Behaviour response of Namaqua Afrikaner, Dorper and South African Mutton Merino lambs towards humans

The response of Namaqua Afrikaner, Dorper and South African Mutton Merino lambs, of approximately four months of age, towards a human being situated between them and their flock mates was studied in an arena test. The objective of the study was to determine whether the unimproved Namaqua Afrikaner, with an arguably shorter history of selection, would react differently to humans in an arena test compared to commercial breeds. A total number of 305 animals, born in 2010 and 2011 and raised under extensive veld conditions, were assessed in a modified arena test when the lambs born in each year were approximately four months old. From the test results it was possible to calculate the following parameters of the behaviour of the sheep: (i) The mean distance from the human operator, (ii) the time a lamb spent in a specific zone situated either close to or far from the human, and (iii) the total number of boundaries crossed, which gives an indication of the total distance travelled by an individual lamb. Other data recorded were the number of bleats and the number of times an animal urinated or defecated. There were no significant sex and birth type differences for any of the behaviour traits. No conclusive breed differences were found for any of the traits describing the behaviour of the lambs, except for the number of bleats. Namaqua Afrikaner lambs bleated significantly (24.0 ± 1.2) more in the three minute testing period than Dorper (8.2 ± 0.9) and South African Mutton Merino lambs (11.9 ± 2.5). Further research is necessary to see if this slight indication of anxiety could be related to other traits such as lamb survival or product quality.

The effect of dietary lipid saturation and monensin-Na on the CLA content of lambs’ meat

A study was conducted to investigate the influence of an ionophore antibiotic and lipid saturation within a standard finishing diet on the conjugated linoleic acid (CLA) content of lambs’ meat. Two identical sheep grower diets containing 145 g CP, 282 g NDF and 45 g EE per kg DM were formulated. One diet contained no ionophore antibiotic and the other monensin-Na included at 165 g/ton. These two basal diets were supplemented, according to a 2 x 3 factorial design, with three lipid sources [i.e. 20 g/kg of either beef tallow, sunflower oil or a CLA oil concentrate] differing in saturation level and fatty acid profile. Sixty South African Mutton Merino lambs (31.15 ± 2.83 kg) were randomly allocated to the six treatments. After dietary adaptation of 10 days, the lambs received their respective treatment diets for the remaining period of 51 days. At the end of the study seven lambs (45.11 ± 2.99 kg) were randomly selected per treatment and slaughtered. Muscle and subcutaneous fat tissue from loin chops of each carcass were used for lipid extraction and fatty acid analysis. The supplementation of CLA oil in the diet resulted in a significantly lower vaccenic acid concentration of lamb muscle tissue. In contrast, supplementing sunflower oil increased the linoleic acid concentration of only the subcutaneous fat tissue significantly. Sunflower- and CLA oil supplementation increased the cis-9, trans-11 CLA isomer of both subcutaneous fat and muscle tissues, whereas only the CLA concentrate increased the trans-10, cis-12 isomer of both mentioned tissues significantly. The dietary inclusion of monensin-Na decreased the vaccenic-, linoleic- and CLA (cis-9, trans-11 isomer) concentrations of both lamb subcutaneous fat and muscle tissues significantly. The manipulation of the CLA content of lamb seems to be effective when adding either sunflower oil or a CLA oil concentrate to the finishing diet of lambs. However, this effect is inhibited by the addition of monensin-Na to the same diet.Keywords: Conjugated linoleic acid, cis-9, trans-11 CLA isomer, tallow, sunflower oil, subcutaneous fat

The effect of dietary energy and the inclusion of a β-adrenergic agonist in the diet on the meat quality of feedlot lambs

β-adrenergic agonists are commonly used in livestock production to enhance meat production and decrease the fat content of the body. β-adrenergic agonists normally improve growth performance. Recent increases in meat prices and the change in consumer preference towards leaner meat have resulted in more lamb producers opting to finish leaner mutton/lamb on farms in a feedlot system. The aim of this trial was to determine the effect of dietary energy, as well as the inclusion of a β-antagonist, on the meat quality of feedlot lambs. South African Mutton Merino lambs (108) of different sexes (rams and ewes) were weaned at 120 days of age and were randomly divided into six groups (18 lambs per group). The treatment consisted of three different dietary energy levels (high 12.7 MJ ME/kg feed, medium 12.0 MJ ME/kg feed and low 11.3 MJ ME/kg feed) with either the inclusion of a β-adrenergic agonist (zilpaterol hydrochloride) at 8.4 g/ton or not. Data were analysed according to a 3 (dietary energy) x 2 (inclusion of a stimulant) x 2 (sex) factorial analysis. No interaction occurred between treatments and the data were presented as the effect of dietary energy level, the inclusion of a stimulant and sex on proximate components, fat thickness and the tenderness of the meat. The factors β-adrenergic agonists and dietary energy level had no effect on the proximate components, fat thickness or the tenderness of the meat. The ewe lambs’ 9-11th rib-cut had a significantly higher fat content than the ram lambs (27.9% vs. 23.1%, respectively). Meat from ram lambs was less tender (63.60N) compared to that from ewe lambs (57.82N). Neither the inclusion of the β-adrenergic agonist (59.8N vs. 61.9N) nor the dietary energy level (59.3N vs. 63.5N vs. 59.3N) had an effect on the tenderness of meat from lambs in this study.Keywords: Meat quality, β-agonist, energy, South African Mutton Merino

Effects of dietary energy content and provision of β-adrenergic agonist on the production of feedlot lambs

Recent increases in mutton lamb prices have resulted in many lamb producers opting to finish more and more lambs on the farms in a feedlot system rather than marketing directly from the field. The aim of this trial was to determine the effect of dietary energy, as well as the inclusion of a β-adrenergic agonist, on the production of feedlot lambs. South African Mutton Merino lambs (108) of different sexes were weaned (± 36.4 kg) at ca. 120 days of age and were randomly divided into six experimental groups (18 lambs per group), which were adapted to each treatment. Lambs were housed in individual pens. The treatments consisted of three diets (diet 1: 11.3 MJ ME/kg food, diet: 2 12.0 MJ ME/kg food and diet 3: 12.7 MJ ME/kg) with either the inclusion or absence of a β-adrenergic agonist at 8.5 g/ton. The experimental design was a 3 x 2 x 2 factorial design with dietary energy level, the provision of a β-adrenergic agonist and sex as main factors. No interaction occurred between treatments and data are presented as the effect of dietary energy level and the inclusion of a stimulant on the intake, growth and feed conversion ratio (FCR). Neither the dietary energy content nor the β-adrenergic agonist had an effect on FCR. Neither one of the main factors had a significant effect on feed intake. The sex of the lambs had a significant effect on the average daily gain of the lambs with the ewes growing faster than the rams.

Effects of dietary replacement of maize grain with popcorn waste products on nutrient digestibility and performance by lambs

A study was conducted to evaluate the effects of dietary replacement of maize with popcorn waste (PW) on the intake, nutrient digestibility and growth performance of lambs. Diets replacing 0, 25, 50, 75 and 100% maize with PW were formulated and fed ad libitum to 40 South African Mutton Merino lambs (25.0 ± 0.45 kg live-weight). The diets had similar intake and nutrient digestibility of dry matter (DM), organic matter (OM) and neutral detergent fibre (NDF). Lambs fed the 25 and 50% PW diets had higher intakes of crude protein (CP), metabolizable energy and ether extract compared to the other diets. Growth rate was highest (226 g/d) on the 25% diet and lowest (109 g/d) on the 75% PW diet. Best feed conversion ratio (FCR), of 5.1 (kg feed/kg live weight) was obtained with the 0% PW diet. Improved digestibility of CP and EE occurred in the 25 and 75% PW diets. Higher intake of nitrogen (N) and N retention were obtained in the 25 and 50% PW diets. Dietary replacement of >75% of maize resulted in poor animal performance (ADG < 150 g/d and FCR >7.00). It was concluded that PW can replace up to 50% of the maize in diets for growing lambs.Keywords: Average daily gain, by-products, lambs, maize, popcorn

Amino acid requirements of South African Mutton Merino lambs 2. Essential amino acid composition of the whole empty body

Amino acid requirements of South African Mutton Merino lambs 2. Essential amino acid composition of the whole empty body

Effects of a fungal enzyme cocktail treatment of high and low forage diets on lamb growth

A study was completed to determine effects of exogenous enzyme treatment of high and low forage diets on growth performance of lambs. South African Mutton Merino lambs, 42, that were 5 ± 0.2 months of age and 33.6 ± 2.4 kg body weight (BW), were used. All lambs received an adaptation diet, containing 750 g/kg forage and 250 g/kg concentrate, for the first 2 weeks. Lambs were then re-weighed to obtain the initial BW and randomly divided into six treatments with seven blocks/treatment. The high forage diets contained 920 g/kg forage, while the low forage diets contained 600 g/kg forage. The extracellular enzyme fraction (supernatant) of a fungal strain, ABO 374, isolated from South African soil was used as the feed additive. The supernatant was used in a liquid lyophilized form, which was reconstituted with water immediately before application to the diets. Liquid supernatant was applied to high and low forage diets (LIQ-HF and LIQ-LF), lyophilized supernatant applied to high and low forage diets (DRY-HF and DRY-LF) and high and low forage control diets treated with water instead of supernatants (CON-HF and CON-LF) constituted the six treatments. Supernatants were applied to the treatment diets at a concentration of 7.5 ml/kg air dry feed, diluted with water to allow for a final application of 300 ml liquid/kg feed. In the control diets, 300 ml water/kg feed was used. Diets were allowed to equilibrate for 15 min before being fed to the lambs. The experiment was 12 weeks and lambs were weighed every fortnight. The liquid supernatant treatment improved BW gains and feed conversion ratios in both the high and low forage groups. Cumulative gain was 3.5 kg for the HF groups and 9.0 kg for LF groups. Within forage levels, cumulative gains were 4.4, 2.9, 3.3, 9.9, 8.9 and 8.3 kg for LIQ-HF, DRY-HF, CON-HF, LIQ-LF, DRY-LF, and CON-LF, respectively. Dry matter (DM) intake was lower for the HF groups than for the LF groups, but within forage levels, treatment had no effect on DM intake. Mean feed conversion ratio (FCR) was 18.5 kg DM/kg gain for the HF groups and 9.8 kg DM/kg gain for the LF groups. Within forage levels, mean FCR values were 14.5, 22.1, 18.9, 8.8, 9.7 and 10.8 kg DM/kg gain for LIQ-HF, DRY-HF, CON-HF, LIQ-LF, DRY-LF, and CON-LF, respectively. We conclude that the enzyme cocktail derived from the ABO 374 fungal strain improved lamb performance when used as a feed additive. The lyophilized product showed limited potential in low forage diets.

Production efficiency of South African Mutton Merino lambs and Boer goat kids receiving either a low or a high energy feedlot diet

Individual feed consumption, utilisation, digestion efficiency and growth of 32 Boer goat (BG) kids and 32 South African Mutton Merino (MM) lambs were investigated after weaning. Two pelleted diets (fed to 16 animals per species) with either a low (LE, 9.89 MJ kg −1 DM) or a high (HE, 12.11 MJ kg −1 DM) metabolisable energy level were fed individually, ad lib, for either 28 or 56 days. MM had significantly higher average daily gains (ADG) than BG. Within a diet there was no significant difference in feed conversion efficiency (FCE) between BG and MM and only the MM FCE differed between the LE- and HE-diets. BG fed LE digested DM, CP and energy more efficiently and had a higher energy retention than MM fed LE. Neither species, nor diet affected N retention. The average daily gain of the MM on the LE-diet for 28 days was significantly lower than for those on the HE-diet. However, there was no significant difference between the ADG of BG on the high or low energy diets. These trends were similar in the group of animals that were fed for 56 days. These results indicate that Boer goats may be finished on a diet with a lower ME-value than is usually formulated for sheep, without a reduction in performance. This may render the BG economically viable for feedlot finishing.

Nitrogen retention response to the abomasal infusion of amino acids in South African Mutton Merino lambs

The nitrogen (N) retention response to the abomasal infusion of amino acids in South African Mutton Merino ram lambs fed a standard finishing diet was investigated. The basal diet consisted of (g/kg air dry weight): 300 lucerne, 80 wheat straw, 561.5 maize meal, 35 molasses meal, 10 urea, 5 salt, 7.5 ammonium chloride, 1.0 vitamin/mineral premix and 0.29 taurotec(r). Twenty-eight lambs (ca. 38 kg live weight) were randomly allocated to four treatments consisting of different abomasal infusion rates of an amino acid mixture, formulated to contain essential amino acids in the same ratio as that of the whole empty body. The mixture consisted of (g/kg): 119.7 arginine, 154.9 histidine, 22.1 isoleucine, 106.5 leucine, 91.5 lysine, 146.9 methionine, 105.6 phenylalanine, 133.8 threonine and 118.7 valine. The mixture was infused at levels of (g/d): 0.00, 38.27, 51.02 or 63.78. Glycine was used to balance the various mixtures on an iso-nitrogenous basis. Infusion of 51.02 g/d of the essential amino acid mixture resulted in a significant increase in N retention, expressed as a percentage of N intake, compared to the control group which received the test diet and glycine (Phase 1). The omission of histidine, methionine or threonine from the infusate (Phase 2) had no significant decrease in N retention or plasma amino acid concentrations compared to the infusion of the mixture of nine essential amino acids. South African Journal of Animal Science Vol.32(2) 2002: 106-112

Full-fat canola as protein source in diets for finishing lambs

Full-fat canola seed (22.5% crude protein (CP) and 42.4% crude fat on a dry matter (DM) basis) was evaluated in the diets of finishing South African Mutton Merino lambs. Four diets were formulated on an iso-protein basis (approximately 15.2% CP on an as-fed basis) so that fishmeal and barley were gradually substituted by increasing levels of full-fat canola (0, 6, 12 and 18%). The lambs ( n=60) were fed ad libitum from 18 to 41 kg while housed individually. No significant differences occurred in the daily DM intake (DMI) of lambs consuming the four different diets. Lambs on the diet with 0% full-fat canola tended to grow 14% ( P<0.10) slower than lambs on the diet with 6% full-fat canola and had a 21% lower ( P<0.05) feed conversion ratio (FCR) than lambs on diets with 6, 12 or 18% full-fat canola. It is concluded that although DMI decreased by 36 g per lamb per day with every 6% increment of full-fat canola inclusion, an increase in full-fat canola inclusion of up to 18% had no negative influence on the average daily gain (ADG) or FCR of lambs.

Performance responses of lambs of various ages to Italian ryegrass (&lt;i&gt;Lolium multiflorum&lt;/i&gt;) fertilized with various levels of nitrogen

Italian ryegrass (Lolium multiflorum cv. Midmar) is often fertilized with high levels of nitrogen (N) in order to ensure maximum dry matter (DM) yields. This practice also increases the N content of herbage. This study was conducted to determine whether differences in the nitrogen (N) content of Italian ryegrass would have an effect on the performance of South African Mutton Merino lambs. Fertilizer levels of 100, 200, 400, 600 or 800 kg N/ha were applied to the pastures in order to produce herbage containing varying concentrations of N. Nitrogen fertilization increased the total N and nitrate-N in the plant material and decreased non-structural carbohydrate concentrations. An increase in rumen ammonia-N concentration with increasing pasture N concentration was observed in twelve and four-month-old lambs. A quadratic relationship was found to exist between the N content of ryegrass and DM intake for twelve-month-old lambs, and a negative linear relationship was observed for four-month-old lambs. A quadratic relationship was observed between the N content of ryegrass and average daily gain for lambs of both age groups. The equations derived in this study illustrate the potentially negative effects of high concentrations of N and nitrate-N in Italian ryegrass on intake and growth rate of lambs. South African Journal of Animal Science, Vol 31, Issue 3, Oct – Dec (2001): pp. 142-148Key Words Average daily gain, Dry matter intake, Italian ryegrass, Lambs, Nitrogen, Nitrate-nitrogen

The effect of a lactic acid bacterial inoculant on maize silage

Maize silage is an important forage in South Africa and it is often made without the use of any additives. Very little information on the fermentation dynamics of maize silage under local conditions is presently available. The aim of this study was to determine if the adding of a lactic acid bacterial inoculant to maize at ensiling will improve the fermentation dynamics of maize silage and to determine the effect of the inoculant on the intake and growth of lambs. Maize was harvested at the hard dough stage with a Feraboli 930 silage chopper and ensiled with or without the addition of a lactic acid bacterial inoculant in 18 laboratory silos for each treatment. Silos were 1.5 l glass jars, equipped with a special lid with springs which enables gas release only. The fermentation dynamics during ensiling was determined by opening three silos on day 1, 2, 4, 10 and 95 of ensiling. The adding of the inoculant to maize at ensiling did not result in a more rapid drop in pH and higher levels of lactic acid. For the intake and growth study maize was ensiled in thirty 210 l drums lined with a plastic bags for each treatment. The material was compacted, the bags were closed and a concrete paving stone (20 kg) was placed on top of the bag. The intake and growth of South African Mutton Merino lambs fed inoculated and untreated maize silage was determined. 2 groups of 14 lambs weighing 26.4±1.9 and 26.4±1.6 kg were randomly allocated to the control and the inoculant treatment, respectively. The average daily gain of lambs fed a diet consisting of either 60% control or inoculated maize silage over a growth period of 60 days was 239±26 and 255±44 g day −1, respectively. The feed conversion efficiencies were 4.94 and 4.93 kg DM feed kg −1 live weight gain for lambs fed the control and inoculated silage diets, respectively. Although the laboratory study showed very little effect of adding a lactic acid bacterial inoculant to maize at ensiling, lambs tended to consume more of the inoculated silage.