Protein Conservation in Female Caribou (Rangifer Tarandus): Effects of Decreasing Diet Quality During Winter

Using ultrasound measurements of rump fat to assess nutritional condition of woodland caribou in northern British Columbia, Canada

“…Nutritional restrictions in late winter associated with decreased forage availability (e.g., increased snow depth or hardness) may increase both energetic costs (e.g., movement) and catabolism of energetic and protein reserves to maintain body processes (Parker et al, 2005). Fetal development and subsequently, fetal and neonatal viability [e.g., whitetailed deer (O. virginianus; Sams et al, 1995)] may be compromised when maternal protein is progressively depleted to meet energetic demands.…”

“…Monitoring changes in body protein, however, is challenging because of the relatively small changes that occur throughout the year (approx 9.5-11.2% of body mass for breeding female caribou, Chan McLeod et al, 1999). Recent use of nitrogen isotopes in snow urine to assess nitrogen balance in late winter (Parker et al, 2005;Barboza & Parker, 2006) is promising, but this technique requires validation in wild populations of caribou.…”

“…We were unable to make direct comparisons of our measurements of rump fat with those of Arctic populations because back fat of barren-ground animals mostly was measured manually and at different locations on animal carcasses. Ultrasonography with standardized protocols is now being used to determine thickness of rump fat in both live barren-ground and woodland caribou for captive (Parker et al, 2005;Barboza & Parker, 2006) and wild (E. Jones, unpublished data from British Columbia; M. Oakley, unpublished data from Yukon; this study) populations.…”

Modeling energy and protein reserves in support of gestation and lactation: glucose as a limiting metabolite in caribou and reindeer

“…Studies on reindeer and caribou suggest that about 78% of mobilized protein is derived from skeletal muscle and 22% from the viscera (e.g., liver, kidneys, alimentary tract; Reimers et al, 1982;Gerhart et al, 1996). Repeated measures of body composition calculated from estimates of body water using isotope studies (Cameron & Luick, 1972;Holleman et al, 1982;Chan-McLeod et al, 1994;Barboza & Parker, 2008) have import for use with live animals, and these studies on reindeer and caribou (Barboza & Parker, 2008;Parker et al, 2005; challenge the assumption that the ability of ruminants to catabolize body protein is limited (Reid et al, 1966;Nolan & Leng, 1968). Mobilized body protein as amino acids is used to satisfy gestation and lactation demands, and when oxidized, amino acids also are a source of energy.…”

“…Actual LPR and LFR vary annually and depend on the levels of body protein and fat of females entering winter. Fat reserves vary independent of protein among populations and are dependent on reproductive history of the female (Parker et al, 2005(Parker et al, , 2009. Although body protein is often thought to be only poorly mobilized, data from Rangifer populations would challenge this assumption since the seasonal change in body protein is about 26-42% (Huot 1989;Gerhart et al, 1996;Chan-McLeod et al, 1999) giving a LPR of 3-6 kg.…”