Effects of grain type and conditioning temperature during pelleting on growth performance, ruminal fermentation, meat quality and blood metabolites of fattening lambs
Citation
Ran, T., Fang, Y., Wang, Y.T., Yang, W.Z., Niu, Y.D., Sun, X.Z., Zhong, R.Z. (2021). Effects of grain type and conditioning temperature during pelleting on growth performance, ruminal fermentation, meat quality and blood metabolites of fattening lambs. Animal, [online] 15(3), http://dx.doi.org/10.1016/j.animal.2020.100146
Plain language summary
Ruminants can tolerate moderate concentrations of dietary tannin, making it feasible to replace corn with high tannin contained sorghum grain in ruminant diets; however, conditioning temperature of pelleted total mixed ration greatly affects nutrient digestibility. A study was conducted to evaluate the effects of grain type and conditioning temperature of preparing pelleted total mixed ration on growth performance, ruminal fermentation, meat quality and blood metabolites of fattening lambs. Lambs fed sorghum- versus corn-based pelleted total mixed ration had greater propionate proportion, lower acetate to propionate ratio, greater protein digestibility and higher blood glucose in fattening lambs. These results indicated that sorghum can be used for replacing corn in lamb diets for its beneficial effects on favorable fermentation pattern, and enhancing protein and glucose availability. The high temperature and pressure during pelleting will damage the tannins in sorghum, thus have no benefit on improving meat quality. Conditioning temperature during pelleting is critical for growth performance and nutrient digestibility. As the lambs fed both sorghum- and corn-based diets pelleted at 75oC improved averaged daily gain, feed efficiency and the digestibility of protein and starch, we recommend 75oC as the conditioning temperature during pelleting for either sorghum- or corn-based diets.
Abstract
Ruminants can tolerate moderate concentrations of dietary tannin, making it feasible to replace corn with sorghum in ruminant diets; however, conditioning temperature of pelleted total mixed ration (PTMR) greatly affects nutrient digestibility. The objective was to determine effects of grain type and conditioning temperature during pelleting on growth performance, ruminal fermentation, meat quality and blood metabolites of fattening lambs. This was a 2 × 3 factorial study, with corn and sorghum and three conditioning temperatures (65, 75 and 85 °C) in a randomized complete design, with 36 lambs (120 ± 10.2 d and 24.9 ± 3.3 kg) grouped by weight and randomly allocated. The resulting six PTMRs were referred to as 65-S, 75-S and 85-S for sorghum-based diets, and 65-C, 75-C and 85-C for corn-based diets, for low, medium and high pelleting temperatures, respectively. There was no grain type × conditioning temperature (Grain × Temp) interaction on growth performance and apparent nutrient digestibility. Furthermore, grain type did not affect DM intake (DMI), average daily gain (ADG) or feed conversion ratio (FCR) of fattening lambs. Pelleting at 75 °C improved ADG (P < 0.03) and FCR (P < 0.02) of fattening lambs compared to other temperatures. There was a Grain × Temp interaction (P < 0.01) on ruminal pH (lowest in lambs fed 75-S). There tended (P = 0.07) to be a Grain × Temp interaction for total volatile fatty acid (VFA), and there were Grain × Temp interactions for molar proportions of acetate (P < 0.04), butyrate (P < 0.03) and branch-chained VFA (P < 0.01). Lambs fed sorghum-based PTMR had greater molar proportion of propionate (P < 0.03) and lower acetate to propionate ratio (A:P, P < 0.04). Lambs fed sorghum-based PTMR had higher plasma concentrations of urea nitrogen (N) (P < 0.03), glucose (P < 0.01) and alkaline phosphatase (P < 0.05), whereas other blood metabolites were not affected by treatments. There were Grain × Temp (P < 0.03) interactions for color coordinates of longissimus and mid-gluteal muscle. Lambs fed sorghum-based PTMR had lower (P < 0.01) dressing percentage and meat quality than those fed corn-based PTMR. We concluded that sorghum can replace corn in lamb diets without compromising growth performance and feed efficiency; furthermore, feeding sorghum vs corn improved rumen fermentation, with reduced A:P ratio and enhanced N and glucose utilization. Finally, pelleting at 75 °C increased feeding value of either sorghum- or corn-based PTMR for fattening lambs.