Effects of Different Dietary Protein Levels on the Growth Performance, Serum Biochemical Parameters, Fecal Nitrogen, and Carcass Traits of Huanjiang Mini-Pigs

The Huanjiang mini-pig is a Chinese local breed and, the optimal dietary crude protein (CP) level for this breed is still unknown. Therefore, the present study was conducted to investigate its optimum dietary CP level upon the growth performance, serum biochemical parameters, fecal nitrogen content, and carcass traits. Three independent trials with 360 pigs were included. A total of 220 pigs (5.32 ± 0.46 kg) were fed ad libitum, either a 14, 16, 18, 20, or 22% CP diet from about 5- to 10-kg (trial 1); 84 pigs (11.27 ± 1.43 kg) were fed either a 12, 14, 16, 18, or 20% CP diet from about 10- to 20-kg (trial 2); and 56 pigs (18.80 ± 2.21 kg) were fed either a 10, 12, 14, 16, or 18% CP diet from about 20- to 30-kg (trial 3). In trial 1, as dietary CP levels increased, the feed-to-gain ratio (F/G) quadratically decreased (p < 0.05) and was minimal at the 18.42% CP level. The average daily feed intake (ADFI) and final body weight (BW) were not affected by dietary CP levels while the fat percentage decreased (p < 0.05). Besides, a linear decrease in slaughter rate (p = 0.06) and a linear increase in bone percentage (p < 0.05), serum urea nitrogen (UN) (P < 0.05), and fecal nitrogen content (p = 0.07) of pigs were observed. In trial 2, as dietary CP levels increased, the average daily gain quadratically increased (p < 0.05) and was maximum at the 16.70% CP level. The slaughter rate linearly decreased (p < 0.05) whereas the skin rate, serum UN, and NH3-N increased (p < 0.05) linearly, as well as fecal nitrogen content (p = 0.06). In trial 3, as dietary CP levels increased, the F/G increased (p < 0.05), while the ADFI and ADG quadratically decreased (p < 0.05) and was maximum at nearly 14.00% CP level. The bone percentage and serum UN increased (p < 0.05) linearly but the slaughter rate decreased (P < 0.05) linearly, and the fecal nitrogen content quadratically decreased (p = 0.07) whereas the albumin increased (p < 0.05) quadratically. Taken together, the optimal dietary CP levels for growth performance of Huanjiang mini-pigs from 5- to 10-kg, 10- to 20-kg, and 20- to 30-kg were 18.42, 16.70, and 14.00%, respectively.

Photosynthetic pigments estimate diet quality in forage and feces of elk (Cervus elaphus)

Understanding the nutritional dynamics of herbivores living in highly seasonal landscapes remains a central challenge in foraging ecology with few tools available for describing variation in selection for dormant versus growing vegetation. Here, we tested whether the concentrations of photosynthetic pigments (chlorophylls and carotenoids) in forage and feces of elk (Cervus elaphus L., 1785) were correlated with other commonly used indices of forage quality (digestibility, energy content, neutral detergent fiber (NDF), and nitrogen content) and diet quality (fecal nitrogen, fecal NDF, and botanical composition of the diet). Photosynthetic pigment concentrations were strongly correlated with nitrogen content, gross energy, digestibility, and NDF of elk forages, particularly in spring. Winter and spring variation in fecal pigments and fecal nitrogen was explained with nearly identical linear models estimating the effects of season, sex, and day-of-spring, although models of fecal pigments were consistently a better fit (r2adjusted = 0.379–0.904) and estimated effect sizes more precisely than models of fecal nitrogen (r2adjusted = 0.247–0.773). A positive correlation with forage digestibility, nutrient concentration, and (or) botanical composition of the diet implies fecal photosynthetic pigments may be a sensitive and informative descriptor of diet selection in free-ranging herbivores.