Abstract
ObjectiveThe present study aimed to evaluate the effects of varying standardized ileal digestible lysine:threonine (SID Lys:Thr) ratio in the diet on the performance and meat quality of finishing pigs.MethodsIn total 192 crossbred pigs ([Landrace×Yorkshire]×Duroc, 17 weeks old), with an initial body weight (BW) of 70.6±3.9 kg were used in an 8-wk trial. Pigs were randomly allotted to one of six dietary treatments based on their initial BW and sex (8 replications; 4 pigs per pen, 2 barrows and 2 gilts). The pigs in the 6 treatments were fed diets having different SID Lys:Thr ratios such as 1:0.65, 1:0.66, 1:0.67, 1:0.68, 1:0.69, and 1:0.70.ResultsA linear increment (p<0.05) in average daily gain (ADG) and trends in reduction in feed conversion ratio (FCR) were observed during day 29 to 56 of the experiment and the apparent total tract digestibility (ATTD) of dry matter tended to increase linearly (p = 0.094) at the end of the experiment (day 56) with the increase in the dietary SID Lys:Thr ratios. The backfat thickness and lean percentage increased (linear effect, p<0.05) on day 28. In addition, at day 56, a linear (p<0.05) increment in lean percentage was observed. Significant quadratic responses (p = 0.02) for pH and drip loss at day 7 (p = 0.02), a linear increase (p<0.05) in cooking loss and drip loss at day 7, and a trend in quadratic response (p = 0.07) in the lightness of meat color (L*) were observed, whereas other meat quality indices were unaffected by varying the SID Lys:Thr ratios.ConclusionThe SID Lys:Thr ratio for maximum ADG, minimum FCR and enhanced digestibility was found to be 0.70. However, for carcass trait and meat quality, the SID Lys:Thr ratio of 0.65 was enough.
Highlights
Threonine is an essential amino acid (AA) that is not synthesized by animals and is required for both maintenance and growth
The present study aimed to evaluate the effects of increasing the level of Thr by 1% unit from 65% of Lys requirements in CON/basal diet to 5 different levels (66%, 67%, 68%, 69%, and 70% of Lys) to evaluate the optimal standardized ileal digestible lysine:threonine (SID Lys):Thr ratio which enhances the performance and carcass quality of finishing pigs
Growth performance Increasing the SID Lys:Thr ratio of finishing diets did not exert any significant effects in average daily gain (ADG), average daily feed intake (ADFI), and feed conversion ratio (FCR) during day 1 to 28 and in the overall experiment period numerical increase in ADG and a slight reduction in FCR was observed during these periods
Summary
Threonine is an essential amino acid (AA) that is not synthesized by animals and is required for both maintenance and growth. A previous study suggested that the ideal AA ratios for Thr range from 65% of Lys for 5 to 20 kg live weight to 70% of Lys requirement for 50 to 100 kg live weight [11]. This implies different AA requirements for different BWs. In another study by Plitzner et al [12], the total dietary Lys:Thr ratio was estimated to be 1:0.65 or higher for modern crossbred finishing pigs (68 to 113 kg) based on the concept of ideal protein. The present study aimed to evaluate the effects of increasing the level of Thr by 1% unit from 65% of Lys requirements in CON/basal diet to 5 different levels (66%, 67%, 68%, 69%, and 70% of Lys) to evaluate the optimal SID Lys:Thr ratio which enhances the performance and carcass quality of finishing pigs
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