Effect of zinc source on performance, zinc status, immune response, and rumen fermentation of lactating cows.

Two experiments were conducted to examine the effect of zinc (Zn) source on the performance, Zn status, immune response, and rumen fermentation of lactating cows to find the most available Zn source for dairy production. In Experiment 1, a total of 30 multiparous Holstein cows were randomly allocated by body weight and milk yield to one of five treatments in a completely randomized design. Cows were fed a total mixed ration (TMR) with no Zn addition (containing 37.60 mg Zn/kg TMR by analysis), and the basal TMR supplemented with 40 mg Zn/kg TMR from either Zn sulfate or one of three organic Zn chelates with weak (Zn-AA W), moderate (Zn-Pro M), or strong (Zn-Pro S) chelation strengths, respectively for 55 days. In Experiment 2, the in vitro rumen fermentation method was used in a completely randomized design involving a 4 × 3 factorial arrangement of treatments. The four Zn sources were the same as those used in Experiment 1, and the three supplemental Zn levels in the rumen fluid were 0, 10, and 20 µg/mL, respectively. The feed intake, milk composition, and somatic cell count (SCC) were unaffected (P > 0.05) by treatments. However, the milk yield was increased (P < 0.05) by addition of Zn from both the Zn-AA W and Zn-Pro S. Plasma Zn level at the end of the experiment was increased (P < 0.05) by addition of Zn from all three organic sources. Serum antibody titers on day 21 after vaccination with foot and mouth disease (FMD) vaccine were increased (P < 0.05) by both supplemental Zn-AA W and Zn-Pro S. The organic Zn sources with different chelation strengths supplemented at the added Zn level of 10 µg/mL were more effective (P < 0.05) in improving the rumen fermentation than Zn sulfate, with the most effective being Zn-AA W. In conclusion, Zn source had no influence on the feed intake, milk composition, and SCC; however, both the Zn-AA W and Zn-Pro S were more effective than Zn-Pro M and Zn sulfate in enhancing the rumen fermentation, Zn status, and humoral immune response as well as improving milk yield of lactating cows. The improved milk production might be attributed to the improved rumen fermentation, Zn status, and immune function.

Effects of soybean oil and linseed oil on fatty acid compositions of muscle lipids and cooked pork flavour.

This study was conducted to investigate the effects of dietary oil on the fatty acid compositions of the longissimus and biceps brachii muscles and its effects on cooked muscles flavour. Seventy-two crossbred barrows (Duroc×Landrace×Large White), were blocked by weight and randomly assigned to one of three treatments. The three dietary treatments were: (a) no oil supplement (CON); (b) 3% soybean oil supplement (SO3); (c) 3% linseed oil supplement (LO3). Dietary linseed oil and soybean oil significantly increased the contents of C18:3 and C18:2 in the neutral lipids and phospholipids in both longissimus muscle and biceps brachii muscle, respectively. Aroma compounds analysis indicated only few aroma compounds were affected significantly by dietary oil in both cooked longissimus muscle and biceps brachii muscle. The flavour attributes of cooked longissimus muscle and biceps brachii muscle were not influenced by feeding 3% soybean oil. Feeding 3% linseed oil did not deleteriously affect the flavour of cooked longissimus muscle but cooked biceps brachii muscle from LO3 had significantly lower pork flavour and higher abnormal flavour than CON and SO3.