The two myostatin genes of Atlantic salmon (Salmo salar) are expressed in a variety of tissues.

Two myostatin isoforms were identified in Atlantic salmon (Salmo salar) by RT-PCR, and genomic sequences encoding this negative muscle growth factor were for the first time isolated from a nonmammalian species. Salmon myostatin isoform I is transcribed in white skeletal muscle as a 2346-nucleotide mRNA species that encodes a precursor protein of 373 amino acids. Salmon myostatin I shows 93% sequence identity with isoform II which was isolated from white muscle as a partial cDNA sequence of 1409 nucleotides. In contrast to the restricted gene expression of myostatin in mammals, salmon myostatin I and II mRNAs were identified by RT-PCR in multiple tissues, including white muscle, intestine, brain, gills, tongue and eye. In addition, isoform I mRNA was found in red skeletal muscle, heart, spleen, and ovarian tissue. Using polyclonal antibodies against both isoforms, a 55-kDa precursor protein was detected by Western blot analysis in the red and white skeletal muscle, heart, intestine, and brain. Immunoreactive peptides of 35-40 kDa were identified in the gills, tongue, spleen, and head kidney, while the 25-kDa mature myostatin was found in the eye and serum, and in vitro expressed in rabbit reticulocyte lysate. Salmon myostatin was immunohistochemically localized in the sarcoplasma of red and white muscle fibres, in intestinal epithelial cells, at the basis of the branchial primary lamellae, and in odontoblasts and ameloblasts of the tongue teeth. The results indicate that the role of fish myostatin may not be restricted to muscle growth regulation, but may have additional functions similar to the growth/differentiation factor-11 in mammals.     

The use of whole barley diets fortified with solutions of urea,minerals and vitamins for lambs

For one experiment 45 early-weaned lambs were given one of the following five diets from weaning to slaughter: (1) whole barley with urea, minerals and vitamins added as a concentrated solution; (2) as diet (1) plus 4 g/kg of sodium sulphate in solution; (3) as diet (2) plus 1.2 g of methionine-hydroxyanalogue (MHA)/kg; (4) as diet (2) plus 2.5 ml of 40% formaldehyde added per kg; (5) a control diet containing whole barley and 100 g/kg of a pelleted supplement based on fish meal. Growth rates (g/d) for the five treatments were 218, 253, 253, 256 and 292. Addition of sulphate significantly increased growth rate and food utilization while MHA had no effect; formalin treatment reduced digestibility and food utilization.In a second experiment 58 lambs were used to study the effect of protein supplements for lambs weaned at various ages and weights. Diets similar to (2) and (5) from Expt. 1 were used, while an intermediate diet (6) was made from an equal mixture of diets (2) and (5). As weaning age increased and as live weight at weaning increased, the difference in growth rate and food utilization between lambs receiving diet (2) and those receiving diets (5) and (6) decreased.It is suggested that for most sheep production systems in which concentrates are used either as the sole feed or as supplements, simple fortification of whole grain with the necessary nutrients is all that is required to achieve optimum results.     

Utilization of alkali-treated grain. 1. Alkali-treated grain in complete diets for steers and lambs

In one experiment, 32 lambs were offered (ad libitum) diets based on whole or NaOH-treated barley, or whole or NaOH-treated oats. The live-weight gains from 17 to 35 kg live weight were 371, 290, 258 and 229 g/day, respectively, while the calculated carcass weight gains were 190, 161, 86 and 118 g/day, respectively. There were large differences in the gut contents at slaughter which were 5.0, 3.3, 9.2 and 3.0 kg for the four diets, respectively.Forty-eight, Hereford-cross steers were allocated to six dietary treatments which consisted of unrestricted access to one of the following diets: NaOH-treated barley; rolled barley; NaOH-treated oats; rolled oats; NaOH-treated wheat; or NaOH-treated maize. The steers were fattened from 325 to 425 kg live weight. The average live weight gains were 1.56, 1.91, 1.37, 1.38, 1.49 and 1.42 kg/day, respectively. The steers receiving rolled barley achieved the greatest live weight gains (P < 0.05). The rumen contents at slaughter were 19.8, 32.2, 24.2, 46.0, 20.8 and 18.4 kg, respectively. Because of differences in gut contents, the only significant differences in carcass weight gain were found for the steers receiving rolled oats, for which carcass gain was lower than that for any other treatment (P < 0.001).Sixteen, Hereford-cross steers were allowed free access to diets containing either NaOH-treated barley alone, or NaOH-treated barley mixed with 10% of chopped straw. The live weight gains from 325 to 425 kg live weight were 1.55 and 1.07 kg/day, and food conversion was 5.7 and 8.4 kg feed/kg gain respectively.