Transfer of Lauric and Myristic Acid from Black Soldier Fly Larval Lipids to Egg Yolk Lipids of Hens Is Low.

Implementing insects, such as the black soldier fly larvae (BSFL), as animal feed commonly includes the previous removal of substantial amounts of fat. This fat may represent an as yet underutilized energy source for livestock. However, transfer of lauric and myristic acid, prevalent in BSFL fat and undesired in human nutrition, into animal-source foods like eggs may limit its implementation. To quantify this, a laying hen experiment was performed comprising five different diets (10 hens/diet). These were a control diet with soybean oil and meal and a second diet with soybean oil but with partially defatted BSFL meal as protein source. The other three diets were based on different combinations of partially defatted BSFL meal and fat obtained by two different production methods. Lauric acid made up half of the BSFL fat from both origins. Both BSFL fats also contained substantial amounts of myristic and palmitic acid. However, in the insect-based diets, the net transfer from diet to egg yolk was less than 1% for lauric acid, whereas the net transfer for myristic and palmitic acid was about 30% and 100%, respectively. The net transfer did not vary between BSFL originating from production on different larval feeding substrates. The results illustrate that hens are able to metabolize or elongate very large proportions of ingested lauric acid and myristic acid, which are predominant in the BSFL lipids (together accounting for as much as 37 mol%), such that they collectively account for less than 3.5 mol% of egg yolk fatty acids.

Carcass and meat quality of finished and non-finished Limousin heifers from alpine livestock systems differing in altitudinal origin of the forage.

Effects of the alpine origin of the forage and of finishing on carcass and beef quality were quantified by modelling different alpine livestock system alternatives. Thirty-five Limousin heifers, initially weighing 383 ± 45 kg, were fed fresh grass at 400 or 2000 m above sea level, or a 1:1 mixture of alpine grass and lowland grass hay at 2000 m. After 9 weeks, the six heaviest and oldest animals per group were slaughtered. The remaining animals were finished for 8 weeks on a silage-concentrate diet in the lowlands to similar age and body weight as the first slaughtered group. Carcass and meat quality (M. longissimus thoracis) were assessed in various respects. The average daily gains achieved were of about 600 g/d and similar between forage-type groups. Dressing percentage was 53.5% in the alpine and 57.2% in the lowland group. Carcass conformation and fat cover scores did not differ between forage-type groups. The meat from the alpine groups had greater ultimate pH and smaller redness, yellowness and protein contents. Still, these differences were of minor practical relevance. There was no forage-type effect on water-holding capacity and shear force of the meat. The alpine systems enhanced the proportion of α-linolenic acid in intramuscular fat and decreased the levels of some volatile compounds in perirenal fat. Finishing resulted in compensatory growth, especially in the animals previously fed lowland grass. There was a trend for the finished compared with the non-finished groups towards greater carcass fat cover and intramuscular fat content. Additionally, ultimate pH was smaller and cooking loss was greater with than without finishing. Meat colour differences were also observed. Shear force was not affected by finishing. The finished animals had a smaller α-linolenic acid proportion in the intramuscular fat. In conclusion, the forage type had small effects on carcass and meat quality. Finishing did not substantially improve carcass and meat quality. The (alpine) grass-specific differences in fatty acid profile found in the unfinished cattle were not present in the finished animals.