Alexander Mackay Mackenzie

Dr. Alexander Mackay Mackenzie

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Research Focus & Metrics

Academic Career Length

24Years (2003-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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23 September 2019 in Archives of Animal Nutrition
Verified
Journal Article
Closed access
EWEmilea Sarah Watts
Emilea Sarah Watts
SRStephen Paul Rose
Stephen Paul Rose
AMAlexander Mackay Mackenzie
Alexander Mackay Mackenzie
VPVasil Pirgozliev
Vasil Pirgozliev
The chemical characteristics of rapeseed meal (RSM) produced from two cultivars of UK-grown rapeseed, by both supercritical carbon dioxide extraction (ScCO2) and cold-pressed hexane extraction (CpHe) were examined. Their nutritional value, with and without protease, was then assessed in a broiler digestibility trial. Basal feed was substituted with one of four RSM batches (200 g/kg) following adjustments for dry matter (DM) and ether extract (EE) content. Half of each diet was supplemented with a mono-component protease derived from Bacillus subtilis (Axtra®PRO, Danisco Animal Nutrition, Malborough, UK) giving a total of eight test diets. Two control diets, with and without protease were also fed. At 13 d age male Ross 308 broilers were randomly allocated to seven replicate pens (five birds per pen) and assigned to one of 10 diets. Total excreta were collected from 17 to 21 d age and feed intake was recorded. Pre-caecal protein digestibility (pcPd) was determined using TiO2 as an indigestible marker. Colourimetrically CpHe RSM was substantially darker than ScCO2 counterparts. The influence of oil recovery method (ORM) was also evident in DM, EE, ash free neutral detergent fibre (aNDFom), neutral detergent insoluble crude protein (NDICP) and glucosinolate content (GLS). The content of DM, EE and GLS was higher in ScCO2 RSM whereas aNDFom and NDICP levels were greater in CpHe RSM. Protein solubility in KOH was greater in ScCO2 RSM whilst levels of NDICP were lower. Collectively these results suggest that less heat damage was incurred to the RSM during ScCO2 extraction. There was no significant main effect of cultivar nor were any significant interactions observed between treatment factors. Rapeseed meal ScCO2 produced greater metabolisable energy, pcPd, nitrogen retention and energy metabolisability (p < 0.05). Protease supplementation increased pcPd (p < 0.05) irrespective of ORM and cultivar. The key implications of these findings are that by adopting oil recovery methods that minimise the exposure of RSM to thermal treatments and by adding a compatible protease there is scope to increase the nutritional value of RSM for broilers and increase its utilisation in modern poultry production.

1 October 2020 in Journal of Dairy Science
Verified
Journal Article
Closed access
.M.James Hugh McCaughern
.James Hugh McCaughern
AMAlexander Mackay Mackenzie
Alexander Mackay Mackenzie
LSL.A. Sinclair
L.A. Sinclair
To test the hypothesis that Cu metabolism in dairy cows is affected by dietary starch concentration and additional sulfur S and Mo, 60 Holstein-Friesian dairy cows that were [mean ± standard error (SE)] 33 ± 2.5 days postcalving and yielding 41 ± 0.9 kg of milk/d were fed 1 of 4 diets in a 2 × 2 factorial design experiment over a 14-wk period. The 4 diets had a Cu concentration of approximately 15 mg/kg of dry matter (DM), a grass silage-to-corn silage ratio of 1:1, a dietary starch concentration of either 150 g/kg of DM (low starch, LS) or 220 g/kg of DM (high starch, HS), and were either unsupplemented (-) or supplemented (+) with an additional 0.8 g of S/kg of DM and 4.4 mg of Mo/kg of DM. We found an effect of dietary starch concentration on mean reticular pH, which was 0.15 pH units lower in cows fed the high starch diets. The addition of S and Mo decreased intake by 1.8 kg of DM/d, an effect that was evident beginning in wk 1 of the study. Mean milk and fat yields were 37.0 and 1.51 kg/d, respectively, and were not affected by dietary treatment. We found an effect of dietary starch concentration on milk protein concentration, protein yield, and urea nitrogen, which were increased by 2.8 g/kg, 0.09 kg/d, and 2.1 mg/dL, respectively, in cows fed the high starch diets. We found no effect of dietary treatment on either cow live weight or body condition. Mean plasma Cu, Fe, and Zn concentrations were 15.3, 42.1, and 14.4 µmol/L, respectively, and were not affected by dietary treatment. In contrast, we found an interaction between dietary starch concentration and Cu antagonists on plasma Mo, where feeding additional S and Mo increased plasma Mo to a greater extent when cows were offered the high versus low starch diet. We also found that increasing dietary starch concentration increased serum ceruloplasmin activity, but serum haptoglobin concentration was not affected by dietary treatment. The addition of S and Mo decreased hepatic Cu concentration, whereas in cows fed the higher dietary starch concentration, hepatic Cu concentration was increased over the period of our study. We concluded that increasing dietary starch concentration decreases rumen pH and increases milk protein yield and hepatic Cu concentration, whereas feeding additional S and Mo decreases intake and hepatic Cu concentration.

4 May 2021 in Archives of Animal Nutrition
Verified
Journal Article
Closed access
EWEmilea Sarah Watts
Emilea Sarah Watts
SRStephen Paul Rose
Stephen Paul Rose
AMAlexander Mackay Mackenzie
Alexander Mackay Mackenzie
VPVasil Pirgozliev
Vasil Pirgozliev
A study was conducted to 1) investigate the influence of rapeseed cultivar on the range of variation in the chemical composition and feed value of rapeseed meals (RSM) for broilers and 2) to compare between single-cultivar RSM and a batch of UK-sourced proprietary rapeseed meal. Chemical composition was determined for a total of 10 single-cultivar RSM produced via prepressed solvent-extraction and a proprietary RSM. To investigate RSM digestibility a total of 360 birds were housed, six birds per pen, and between day 13 to 21 of age they received a diet containing per kg 250 g RSM and 750 g basal feed based on wheat and soybean meal. Titaniumdioxide (7 g/kg) was added as an inert marker. For the determination nitrogen-corrected metabolisable energy (AMEn) total excreta and feed intake were quantified over the last 4 d of the experiment. On the final day of the experiment ileal digesta were collected for determination of preceacal crude protein digestibility (pcCPD). With the exception of neutral detergent fibre (NDF), glucosinolates and soluble non-starch polysaccharides the coefficients of variation (CV%) for all major components were similar across all RSM (0.5 < CV% < 0.6). Glucosinolate contents were highest in the 10 single-cultivar RSM whereas NDF levels were greater in the proprietary RSM. Across the 10 single-cultivar RSM there was no significant effect of cultivar on AMEn or pcCPD. Pre-planned orthogonal contrasts indicated that the mean AMEn content and pcCPD of the proprietary RSM was significantly lower than the 10 single-cultivar RSM (p < 0.001). In view of the above, processing rather than cultivar appears to be the main driver of nutritional value in RSM fed to broilers.

4 November 2020 in British Poultry Science
Verified
Journal Article
Closed access
JAJ. M. Abdulla
J. M. Abdulla
SRS. P. Rose
S. P. Rose
AMAlexander Mackay Mackenzie
Alexander Mackay Mackenzie
VPVasil Pirgozliev
Vasil Pirgozliev
1. The chemical composition and physical characteristics of 10 different UK-grown field bean cultivar samples from the same harvest year were determined. 2. Diets included each bean sample at a level of 200 g/kg, and were used to compare broiler growth performance and determine N-corrected apparent metabolisable energy (AMEn) and nutrient utilisation. The AMEn and nutrient retention coefficients for the bean samples were obtained via the slope-ratio method. The relationships were examined between variation in nutritive value for broilers and the laboratory analysis of the bean samples. 3. The data showed significant differences (P < 0.05) among the bean cultivar samples for feed conversion ratio, AMEn and dry matter retention (DMR) coefficients. Further analysis showed that the feeding quality of different field bean cultivar samples, measured as AMEn, was highly correlated to crude protein (CP) (P < 0.05) and colour (P < 0.001) of the samples. Thus, beans with higher CP and pale colour had superior feeding value for broilers.

8 April 2025 in Animals
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Journal Article
Open access
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GMGergana Yordanova Marcheva
Gergana Yordanova Marcheva
RNRadka Dimitrova Nedeva
Radka Dimitrova Nedeva
AAApostol Petrov Apostolov
Apostol Petrov Apostolov
Stephen Charles MansbridgeStephen Charles Mansbridge
Stephen Charles Mansbridge
IWIsobel Whiting
Isobel Whiting
VPVasil Pirgozliev
Vasil Pirgozliev
The production of soybean meal (SBM) can be linked to various issues related to the environment (e.g., deforestation, water waste, and transportation costs), and reducing its inclusion in pig diets by using alternative protein sources, such as insect meal, is an important challenge for nutritionists. This study aimed to compare the productive performance, dietary digestible energy (DE), nutrient digestibility, and some blood indices of growing Danube White pigs fed graded levels of Black Soldier fly (Hermetia illucens L.) larvae meal (BSFLM) at 0, 30, 60, 90, and 120 g/kg of diets, in replacement of SBM for 38 days, from 119 to 157 d old. Each diet was fed to eight pigs in individual boxes following randomization. Pigs grew according to breeders’ recommendations and did not have any clinical health problems. Replacing SBM did not change (p > 0.05) the pigs’ growth performance and DE, as only dietary fat digestibility increased in a linear fashion (p < 0.001), possibly due to the high BSFLM, i.e., the high-fat inclusion rate. There was a simultaneous rise in some oxidative damage indicators and an increase in antioxidant status, thus suggesting that further research involving longer feeding periods is needed to identify a potential time sequence of events. Overall, BSFLM is a promising ingredient in pig nutrition.

1 November 2024 in Journal of Dairy Science
Verified
Journal Article
Open access
AWAnnie Williams
Annie Williams
JBJames J. Bennison
James J. Bennison
AMAlexander Mackay Mackenzie
Alexander Mackay Mackenzie
LSLiam A. Sinclair
Liam A. Sinclair
The apparent absorption of copper (Cu) in ruminants is low, with between 0.01 and 0.07 g/g absorbed from sources such as copper oxide (CuO) under typical feeding conditions, resulting in high levels of excretion. Improving the bioavailability of Cu could reduce the supplemental amount required to maintain Cu status and reduce excretion, particularly in the presence of dietary antagonists such as sulfur (S) and molybdenum (Mo). The objective of our study was to determine the Cu status of cows when fed nanoparticle CuO coated with Lys compared with conventional CuO when fed without or in combination with antagonists to Cu absorption (S and Mo) in the diet of dairy cows. Fifty-six multiparous Holstein-Friesian cows that were 48 d ± 17.4 (mean ± SD) post calving and yielding 40.6 ± 6.9 kg milk/d were used in a 2 × 2 factorial design. The 4 treatment groups were; CuO (O-), CuO with added antagonists (O+), nano CuO with a lysine coating (N-), and nano CuO with a Lys coating with added antagonists (N+), fed for 16 wks. We formulated the diets to contain approximately 17 mg Cu/kg dry matter (DM) and diets with antagonists contained an additional 1 g S/kg DM and 6 mg Mo/kg DM, with Lys added to O- and O+ to provide the same daily supply as N- and N+. Blood samples were collected at wk 0, 2, 4, 6, 10 and 16, and liver biopsy samples at wk 0 and 16. We found no effect of dietary treatment on DM intake, milk yield, live weight or body condition score, with mean values of 23.3 kg/d, 40.1 kg/d, 646 kg and 2.68, but milk SCC was higher in cows fed conventional compared with non CuO, or with added antagonist. We also found no effect of treatment on blood activity of gamma glutamyl transferase, superoxide dismutase or ceruloplasmin, hematology profile, or plasma Cu and iron concentration. We found that plasma Mo concentration was increased from 0.36 µmol/L in cows fed O- or N- to 0.80 µmol/L in those receiving O+ or N+. Additional dietary antagonists also decreased the concentration of Cu in the liver of cows fed conventional CuO (C+) over the study period by 1.3 mg/kg DM/d, but in cows fed dietary antagonists and nano CuO coated with Lys (N+), liver Cu concentration was increased by 1.1 mg/kg DM/d. Our study is the first to demonstrate that reducing the particle size of CuO into the nano scale with a lysine coating improves the bioavailability of CuO in the presence of dietary antagonists in dairy cattle, and we did not observe any negative effects on performance or health.