Meat: Young or Older Animals? Male or Female?

Is the healthiest meat from younger or older animals? Male or female animals? In my research, I've found that it seems generally across many species, female animals are higher in bodyfat. This would be beneficial for following a keto diet, since we are always seeking higher fat foods!

How about from younger or older animals? I found yesterday that older animals will have higher bodyfat. http://advances.sciencemag.org/content/3/2/e1601833.full

The composition of protein and fat was found to be different in young (90.0% protein and 2.1% fat) and old (57.8% protein and 38.0% fat) muscles (table S3), in agreement with previous studies, which found that the muscle fat increases during aging in mammals (18). 

However, in that same study, they came to the conclusion that meat from younger animals increased lifespan, but only for the females in the study.

Together, the data suggest that the diet containing the old skeletal muscle may shorten the mouse life span, although sexual dimorphism was apparent under the conditions used. 

I will just eat as large a variety of meat that I can, from both young and old animals, male and female animals, including organ meats, and keep my fat intake over 70% of calories!

Grassfed lamb heart with beef marrow and sea salt flakes