Mary A. McNiven

Growth, rate, body composition and feed digestibility/conversion of growth-enhanced transgenic Atlantic salmon (Salmo salar)

Although dramatic improvements in growth rates have been documented in growth-enhanced transgenic salmonid fish, prior to commercial implementation of this technology, there is a need for further information relating to the physiology of a number of commercially important production traits. Growth rate, feed digestibility, feed conversion, and body composition of F 2 generation growth-enhanced transgenic Atlantic salmon were therefore compared with that of non-genetically modified salmon, over a presmolt growth interval of 8-55 g. The growth-enhanced transgenic fish exhibited a 2.62- to 2.85-fold greater rate of growth relative to non-transgenic salmon over the body weight interval examined. Daily feed consumption over this body weight interval was 2.14- to 2.62-fold greater for the transgenic fish compared to the control fish. Transgenesis did not affect the extent to which protein and energy were digested, with digestibility coefficients 88% and 81%, respectively for transgenic fish, and 90% and 84%, respectively for control fish, both measured over comparable body weight intervals. However, transgenic salmon relative to control fish exhibited a 10% improvement in gross feed conversion efficiency. Body protein, dry matter, ash, lipid and energy were significantly lower in the transgenic salmon relative to controls while moisture content was significantly higher. The transgenic experimental subjects used throughout the present study possessed the physio- logical plasticity necessary to accommodate an acceleration in growth well beyond the normal

Effect of food deprivation on oxygen consumption and body composition of growth-enhanced transgenic Atlantic salmon (Salmo salar)

Abstract The influence of food deprivation on the rate of oxygen consumption and the rate of mobilization/utilization of energy reserves in F 2 generation growth-enhanced transgenic Atlantic salmon were compared relative to their non-transgenic counterparts, over a pre-smolt weight interval of 8 to 55 g. Throughout most of the 8 weeks of food deprivation, transgenic fish exhibited a greater rate of oxygen consumption compared to control salmon, but also exhibited a more rapid decline in oxygen consumption as starvation progressed. Consequently, depending on initial weight and length of food deprivation, the rate of oxygen consumption of transgenic fish declined to where it equaled or was less than the oxygen consumption of control fish. Transgenic fish depleted body protein, dry matter, lipid and energy at a faster rate than did the controls. Additionally, in both groups, lipid was catabolized faster than was protein. Although transgenic fish demonstrated the ability to reduce their metabolic rate during starvation, as also observed in the non-genetically modified control salmon, their persistence in maintaining a higher metabolic rate, combined with their lower initial endogenous energy reserves, suggests that the likelihood of growth-enhanced transgenic salmon achieving maximum growth or even surviving outside intensive culture conditions may be lower than that of non-transgenic salmon.

Evaluation of protein quality in fish meals by chemical and biological assays

Abstract Fish meals (herring, menhaden, and anchovy), commercially available in Atlantic Canada and a Norwegian fish meal (Norse-LT94 ® ) were evaluated for their protein quality by in vitro assays and by growth studies with Atlantic salmon ( Salmo salar ) fingerlings. Pepsin digestibility and multienzyme digestibility were useful in predicting protein quality. Assays for total volatile basic-nitrogen, available lysine, sulphydryl groups, and disulphide bonds, particularly when used alone, were of limited value. Atlantic salmon fingerlings (initial weight 7.65±0.14 g) fed diets containing two steamdried herring meals and Norse-LT94 ® for 70 days were evaluated on the basis of weight gain, PER, NPR, NPU, and slope assay. Fish fed Norse-LT94 ® gained 11–60% more weight than fish fed the Canadian meals. The protein quality of the Canadian fish meals was lower than that of Norse-LT94 ® . Pepsin digestibility ranked the fish meals in the same order as the biological tests, but the biological testing of feedstuffs to determine protein quality is recommended as the final method of comparison. Biological evaluation is the preferred method of measuring the overall quality of a feedstuff, since in vitro tests usually miss-rank the quality of some feedstuffs.

Metabolic rate of pre-smolt growth-enhanced transgenic Atlantic salmon (Salmo salar).

Abstract The rates of routine oxygen consumption of growth-enhanced transgenic Atlantic salmon were compared with that of non-transgenic salmon, over a pre-smolt body interval of 8–55 g to determine whether or not the transgenic salmon also expressed a greater metabolic rate. Routine oxygen consumption rates (mg O 2 /h), inclusive of the heat increment associated with feeding, were 1.54- to 1.70-fold higher for transgenic fish compared to the controls. However, integrated over time from first feeding to smolt size, the transgenic salmon actually consumed 42% less total oxygen than the non-genetically modified controls to reach smolt size. In a post-absorptive state (24 h starvation), corresponding oxygen consumption rates of transgenic fish were 1.58- to 2.30-fold greater than that of regular salmon. The added cost to smolt producers for the short-term delivery of more water or oxygen to support the elevated metabolism of such growth-enhanced fish would appear to be justified in light of the benefits in reducing smolt production time.

Effect of dietary lipid level on fatty acid β-oxidation and lipid composition in various tissues of haddock, Melanogrammus aeglefinus L.

Haddock (Melanogrammus aeglefinus) is a gadoid fish species that deposits dietary lipid mainly in the liver. The fatty acid (FA) beta-oxidation activity of various tissues was evaluated in juvenile haddock fed graded levels of lipid. The catabolism of a radiolabelled FA, [1-(14)C]palmitoyl-CoA, through peroxisomal and mitochondrial beta-oxidation was determined in the liver, red and white muscle of juvenile haddock fed 12, 18 and 24% lipid in the diet. There was no significant increase in the mitochondrial or peroxisomal beta-oxidation activity in the tissues tested as the dietary lipid level increased from 12 to 24%. Peroxisomes accounted for 100% of the beta-oxidation observed in the liver, whereas mitochondrial beta-oxidation dominated in the red (91%) and white muscle (97%) of juvenile haddock. Of the tissues tested, red muscle possessed the highest specific activity for beta-oxidation expressed on a per mg protein or per g wet weight basis. However, white muscle, which forms over 50% of the body mass in gadoid fish was the most important tissue in juvenile haddock for overall FA catabolism. The total lipid and FA composition of these tissues were also determined. This study confirmed that the liver was the major lipid storage organ in haddock. The hepatosomatic index (HSI; 10.0-15.2%) and lipid (73.8-79.3% wet wt.) in the liver increased significantly as dietary lipid was increased from 12 to 24% lipid. There was no significant increase in the lipid composition of the white muscle (0.8% wet wt.), red muscle (1.9% wet wt.) or heart (2.5% wet wt.).

Nutritive value of raw and roasted sweet white lupins (Lupinus albus) for lactating dairy cows

Abstract Nine multiparous cows in early lactation were fed alfalfa silage ad libitum twice daily, a grain-based concentrate five times daily, and one of three protein sources five times daily. Supplemental proteins were soya-bean meal, raw coarse-ground sweet white lupins or roasted coarse-ground sweet white lupins. Roasting of lupins increased the calculated undegraded intake protein (UIP) proportion from 7.2 to 33.3% of total nitrogen. Intake of dry matter and organic matter was lower for lupin-supplemented cows, but intake of neutral detergent fibre was similar for all cows. Production of milk, and milk components, was similar among treatments although milk protein concentration was lower, and milk protein yield tended to be lower, for lupin-supplemented cows. Cows on all diets used dietary protein much more efficiently than calculations based upon National Research Council recommendations would suggest. Although lupin oil only comprised 1.1–1.2% of dry matter intake, changes in milk composition were typical of those associated with fat feeding as de novo synthesis of C 10 to C 16 fatty acids was suppressed, transfer of long-chain fatty acids was increased and protein percentage was decreased in milk from lupin-supplemented cows. Roasting appeared to increase protection of lupin oil from ruminal hydrogenation, as evidenced by increased concentrations of long-chain fatty acids in milk from cows supplemented with roasted lupins. The changes in fat composition are positive for the public perception of a more hypocholesterolemic milk fat, but the decrease in protein percentage is a concern both for the manufacture of milk products and with respect to changes in milk pricing formulae that assign a higher value to milk protein than to milk fat.

In vitro methods of assessing the viability of rainbow trout spermatozoa

The accuracy of three in vitro methods for estimating the proportion of dead rainbow trout (Onchorhynchus mykiss) spermatozoa was investigated. Motility rating, fluorometry using ethidium bromide, and lactate dehydrogenase (LDH) activity in seminal plasma were compared. Semen samples were prepared to contain 0, 25, 50, 75 and 100% killed spermatozoa. All three methods demonstrated highly significant relationships (P<0.001) with the percentage of killed spermatozoa. Motility rating was found to be quick and accurate but required experienced workers and the results thus could vary between evaluators. Fluorometry was rapid and relatively simple to perform and required only a small amount of semen. Measurement of LDH activity in seminal plasma was accurate but time-consuming and required large amounts of semen.

DIMETHYL-ACETAMIDE AS A CRYOPROTECTANT FOR RAINBOW TROUT SPERMATOZOA

Dimethyl-acetamide was evaluated as a cryoprotectant for rainbow trout (Oncorhynchus mykiss ) semen on the basis of motility, percentage of dead spermatozoa as determined by fluorometry, and fertility of frozen-thawed spermatozoa. Dimethyl-acetamide performed significantly better (P<0.05) than the conventional cryoprotectant, dimethyl sulfoxide, by all evaluation methods. An extender comprised of 0.137 M NaCl, 0.011 M KCl, 0.004 M Na(2)HPO(4) 7H(2)O, 7.5 g/l L-alpha-lecithin and 10 % DMA showed promise for cryopreserving rainbow trout spermatozoa. Future evaluation of new extenders should be carried out by several in vitro techniques and fertility measurements to present a complete assessment of an extenders ability to cryopreserve sperm cells.

Evaluation of raw and roasted lupin seeds as protein supplements for lactating cows

Lupin seeds, raw or roasted, were compared with soybean meal as protein supplements for dairy cows by determination of crude protein fractions, rumen fermentation characteristics, digestibility of nutrients, and lactation performance. Roasting increased the estimated undegraded crude protein fraction of lupins from 37.7% to 44.7% compared to that of soybean meal at 36.0%. Acid detergent insoluble nitrogen in roasted lupins did not increase markedly compared to raw lupins, indicating minimal protein damage due to roasting. Isonitrogenous substitution of raw or roasted lupins for soybean meal in lactation diets did not substantially change rumen fermentation characteristics or whole tract digestibility of nutrients. However, cows fed roasted lupins produced more milk than those fed raw lupins. Higher yields of fat, protein and lactose from cows fed roasted versus raw lupins were primarily due to increased milk yield. Milk fat from cows fed lupins had higher concentrations of long-chain fatty acids compared with milk from cows fed soybean meal. Improved lactational performance of cows fed roasted versus raw lupins was probably due to more sustained release of protein in the rumen, increased undegraded protein supply, and increased efficiency of utilization of dietary energy for milk energy output.

Raw or roasted lupin supplementation of grass silage diets for beef steers

Raw or roasted lupins were evaluated as protein supplements in rations for growing and finishing beef steers. Lupins were roasted in a flame roaster with an exit temperature of 105°C. The effect of heating on protein solubility and rumen degradability of lupin was evaluated by chemical and Dacron bag procedures. The solubility of N in buffer was reduced from 69.8% in raw lupin to 35.8% in roasted lupin. Effective degradability of crude protein (CP) and rate of CP degradation predicted by the Dacron bag procedure were lower for roasted lupin (82.3% and 9.2% h−1, respectively) than for raw lupin (86.7% and 11.9% h−1, respectively). Heat damage measured by acid detergent insoluble N did not differ between raw (3.31% of total N) and roasted lupin (3.46% of total N). Twenty-eight Charolais cross steers with an average weight of 235 kg (± 35 kg) were fed grass silage only (SIL) or silage plus supplements, to supply CP at 6.5% of the silage dry matter intake (DMI), with raw lupin (RL), roasted lupin (ROL) or soybean meal (SBM) as the source of supplementary protein. When the steers reached 330 kg liveweight they were placed on a finishing diet of chopped hay, barley and protein supplements at a rate of 4.5% of barley DMI. In the growing phase, steers fed RL, ROL or SBM had significantly higher (P 0.05) different. Silage DMI was significantly lower on diets supplemented with RL and ROL compared with SIL. In the finishing phase, there were no significant differences in daily gain, carcass weight, dressing percentage, loin eye area or DMI among the diets. Heat treatment of lupins decreased solubility and ruminal degradability of CP. Growth performance of beef steers fed roasted lupin was similar to that of steers fed SBM.