Influence of benzoic acid and phytase in low-phosphorus diets on bone characteristics in growing-finishing pigs

In 2 simultaneous experiments (Exp. 1 and Exp. 2), the effects of benzoic acid (BA) and phytase (Phy) in low-P diets on bone metabolism, bone composition, and bone stability in growing and growing-finishing pigs were examined. Experiment 1 was conducted with 16 crossbred gilts in the BW range of 25 to 66 kg of BW, whereas in Exp. 2, 32 crossbred gilts (25 to 108 kg of BW) were used. All pigs were individually housed in pens and restrictively fed 1 of 4 diets throughout the experiment. Total P content of the wheat-soybean diets was 4 g/kg (all values on an as-fed basis). The experimental diets were 1) unsupplemented control diet; 2) control diet with 0.5% BA; 3) Phy diet with 750 Phy units (FTU) of Phy/kg and no BA; and 4) PhyBA, control diet with 750 FTU of Phy/kg and 0.5% BA. Blood samples were taken at the beginning of the experiment, wk 3 (only for pigs in Exp. 1), wk 6, and before slaughter to determine P and Ca in serum and concentrations of total alkaline phosphatase, serum crosslaps (marker for bone resorption), and osteocalcin (marker for bone formation). Ash, P, and Ca contents of bones and bone stability were examined using the left metatarsal bones and tibia of the pigs after slaughter. Benzoic acid did not influence any of the blood variables (P > 0.09). The addition of Phy increased (P < or =0.03) P concentration in serum from 2.71 +/- 0.08 to 3.03 +/- 0.07 mmol/L at wk 3 and content of serum crosslaps from 0.39 +/- 0.02 to 0.45 +/- 0.02 ng/mL at wk 6 and decreased (P < 0.05) osteocalcin at wk 6 by 160 ng/mL. No long-term effect of diets on serum mineral concentrations, alkaline phosphatase, and bone markers in serum could be detected. Benzoic acid negatively affected (P < or = 0.03) Ca content in bones and distal bone mineral density, especially in the younger pigs. In the control diet with 0.5% BA and the control diet with 750 FTU of Phy/kg and 0.5% BA, the CA content in bones and distal bone mineral density were reduced by 6 and 11%, respectively. Throughout the whole growing and finishing period, Phy increased (P < or =0.02) ash, P, and Ca contents in bones by 29.4, 4.8, and 11.6 g/kg of DM, respectively. Bone mineral density and bone mineral content were greater in diets with Phy (P < or = 0.03), as well as breaking strength of tibia (+22%) and metatarsal bones (+27%; P < 0.01). The results of this study indicate that for a healthy skeleton, BA should not be used in low-P diets without the addition of Phy

Feeding transition cows with oilseeds: Effects on fatty acid composition of adipose tissue, colostrum and milk

The present investigation was aimed to test whether α-linolenic acid (ALA) concentrations in the adipose tissue can be increased by linseed feeding of dry cows and whether ALA is preferentially mobilized during the catabolic phase after parturition. The second objective was the determination of the influence of mobilization on fatty acid composition of colostrum and mature milk. For this purpose, four groups of six cows were fed diets supplemented either with crushed linseed (rich in ALA; two groups) or sunflower seed (rich in linoleic acid (LA)) or a 1:1 mixture of both for 6weeks. This supplementation was either kept post partum or switched shortly before calving from linseed or the mixture to sunflower seed. The post partum experimental period lasted for another 40d. Samples of blood were obtained in weeks −6, −2, 3 and 6 pre/post calving, those of backfat adipose tissue in weeks −2 and 6 pre/post calving (by biopsy) and milk samples on days 1, 2, 10, 20, 30 and 40 of lactation. Clear changes over time occurred in blood plasma metabolites and hormones as well as in body weight, body condition scores and backfat thickness, especially during the transition before and after calving. Milk yield and composition showed the typical time trends as well. Proportions of long-chain polyunsaturated fatty acids in the colostrum compared to the mature milk were clearly higher. This appeared similarly in all groups and was not influenced by the oilseed treatment. Compared with the physiological time effects, the effects of the oilseed treatments were weak. It was possible to load the adipose backfat tissue with ALA by supplementing linseed in the dry period, but the magnitude of this increase was small. Milk fat profile was not affected accordingly, although the changes found in adipose tissue post partum suggested the preferential mobilization of ALA during early lactation. Supplementing sunflower seed instead of linseed in the dry period did not elevate LA proportion in adipose tissue nor affected linoleic acid in milk. By contrast, direct transfer of LA, and especially of ALA, from feed to milk happened when sunflower seed or linseed was fed in the lactation period of the experiment. Overall this suggests that strategies aiming at changing n−3 fatty acid concentrations in milk fat composition by loading the adipose tissue of dry cows with ALA are not effective