Nutritional evaluation of different varieties of sorghum stovers in sheep

Nutritive value of stovers from 4 sorghum varieties (Pant Chari 5, PKV 809, CSV 17 and CSV 20) that were selected from a previous breeding program for their relative nutritive value was assessed using the in vitro and in vivo methods. Samples for in vitro and in vivo studies were harvested separately. For the in vivo studies, 16 adult Jalauni sheep (19.1 ± 0.35 kg) were randomly divided into 4 groups (n = 4) and offered chopped stover from CSV 20, PKV 809, Pant Chari 5 and CSV 17 varieties, respectively along with 200 g of concentrate mixture. After a 30-day feeding, 5 days of metabolism trial was conducted to determine dry matter intake (DMI), nutrients digestibility and nitrogen balance. For in vitro study, crude protein (CP) concentration of CSV 20 was lowest (P < 0.05) compared with the other varieties. The NDF and hemicellulose contents were highest (P < 0.001) in CSV 20. The CP content in chaffed stover used for the animal study increased marginally for all varieties except for Pant Chari 5 (45.3 g/kg DM) which had the lowest CP content. Buffer soluble protein (PB1), PA and PC fractions of the stovers were higher (P = 0.006) in CSV 17 compared with the other stovers. Although CSV 20 had the lowest (P < 0.001) PA and PC fractions, it had similar (P > 0.05) PB1, PB2 and PB3 fractions with one or more of the other stovers. In vitro dry matter digestibility was highest (P = 0.002) for CSV 17 and lowest for Pant Chari 5. Stover estimated DMI values varied between 0.0156 to 0.0164 of BW of the sheep with lower (P < 0.001) DMI noted for CSV 20 versus the other varieties. Greater (P < 0.05) cumulative gas production and rate of gas production (k) were noted for CSV 20 and Pant Chari 5 compared with others. Similar trend was also noted in the in vitro methane production, PF and SCFA concentration of the stovers. No difference was noted in the intake and digestibility of DM of the stover varieties. Sheep fed CSV 17 had significantly higher (P < 0.05) nitrogen intake and fecal nitrogen (11.2 and 4.18 g/d, respectively), and a tendency (P = 0.07) for higher urinary nitrogen and nitrogen balance. Overall, results showed that sheep had higher stover intake and better nutrients digestibility, more nitrogen balance and higher nutritive value (digestible CP and metabolizable energy) from CSV 17 and PKV 809 sorghum stover based diets.