The effect of dietary protein levels on body weight gain, carcass production, nitrogen emission, and efficiency of productions related to emissions in thin-tailed lambs

Aim:

This study was aimed to evaluate dietary crude protein (CP) level on performance of body weight (BW) gain, carcass production, and nitrogen emission on lambs.

Materials and Methods:

A total of 12 male thin-tailed lambs (15.2±1.8 kg initial BW and aged 3-4 months) were assigned to completely randomized design for 84-day feeding trial. The animals were divided into three different levels of CP (i.e., 14%, 16%, and 18% with isocaloric diets and 60% total digestible nutrients) with four replications.

Results:

Increasing CP level was not significantly affected on average daily gain (ADG), carcass production, N and N₂O emissions, and efficiency of emissions related to the productions. The average of ADG, carcass production, meat production, meat protein production, N emission, and N₂O emission was 141.4 g, 11.6 kg, 6.8 kg, 0.9 kg, 53.1 g/day, and 0.3 g/day, respectively. The efficiency of ADG, carcass production, meat production, and meat protein related to N emissions were 119.7 g/kg, 4.4 g/kg, 2.5 g/kg, and 56.6 g/kg, respectively, while N₂O emissions related to ADG, carcass production, meat production, and meat protein were 2.4 g/kg, 0.027 g/kg, 0.36 g/kg, and 0.34 g/kg, respectively.

Conclusions:

It can be concluded that the increase of CP level up to 18% did not affect productivity, N emissions, and efficiency of emissions per unit product because the increase of CP was not balanced by energy content in feed.

Additivity of standardized ileal digestibility of amino acids in mixed diets containing multiple protein sources for growing pigs fed three crude protein levels

This study was conducted to investigate the effect of dietary crude protein (CP) levels of semi-purified diets on the additivity of values for standardized ileal digestibility (SID) of amino acids (AA) in mixed diets from multiple protein sources for growing pigs. A total of 28 barrows (initial BW, 66.4 ± 1.3 kg) were surgically fitted with simple T-cannulas at the distal ileum and assigned to a replicated 14 × 4 incomplete Latin square design with 14 diets and 4 periods. The 14 experimental diets consisted of a nitrogen-free diet; a corn-based diet (80 g CP/kg); nine semi-purified diets containing soya bean meal (SBM), canola meal (CM) or corn distillers dried grains with solubles (cDDGS), each type (protein source) of semi-purified diets supplied 80, 120 or 160 g CP/kg, respectively; three mixed diets based on corn, SBM, CM and cDDGS formulated to contain 120, 160 and 200 g CP/kg respectively. Pigs were fed each of the 14 diets during a seven-day period, and ileal digesta were collected from 08:00 a.m to 6:00 p.m on day 6 and 7. Chromic oxide was added as an indigestible marker. Results indicated that the SID of CP and AA were not affected by CP levels (p > .05). Values for SID of AA were additive (p > .05) with the exception of His and Lys; Arg and Lys; Arg, Lys, Thr, Asp, Cys and Gly in the mixed diets containing 120, 160 and 200 g CP/kg respectively (p < .05). In conclusion, additivity of SID values of AA in the mixed diets at different CP levels was not affected by the CP levels of semi-purified diets for growing pigs. Therefore, it is recommended that SID values of AA should be used to formulate practical diets containing multiple ingredients for pigs.