The effects of human milk fortification on nutrients and milk properties.

OBJECTIVE: To investigate the effects of fortification and storage on nutrients and properties of various human milk (HM) types. STUDY DESIGN: Mother's own milk (MOM) and pasteurized donor human milk (DHM; n=118) were analyzed pre- and post fortification with Enfamil and Similac human milk fortifier (EHMF and SHMF) before and after 24 h of refrigerated storage. RESULTS: Milk fortified with SHMF had significantly greater osmolality, pH and lipase activity than EHMF. Changes in protein, pH and osmolality following refrigerated storage differed between fortifiers. When milk type was factored into the analysis, protein and lipase activity changes in fresh MOM differed significantly from DHM and frozen MOM. Analysis of UNF HM found higher protein levels in preterm vs term samples and in MOM vs DHM. CONCLUSION: Nutrient composition of HM varies significantly by milk type. Although fortifiers enhance select nutrients, each has the potential to affect HM properties in a unique way and these affects may vary by milk type.

Bone mineralization in male commercial broilers and its relationship to gait score.

Broilers selected for increased body size and breast muscle have imposed stress on the skeletal system, resulting in poorer walking ability. Our objectives were to determine the relationship between bone mineralization and gait score in 4 crosses of commercial broilers and to ascertain if mineralization of the toe is correlated to the tibia. Three chickens per pen each with good (gait score of 0 or 1) or poorer (gait score of 3) walking ability were killed and weighed. The left humerus, the left middle toe, and both drumsticks were collected for determination of bone mineral density (BMD), bone mineral content, and bone size traits using dual-energy x-ray absorptiometry. The BMD and bone size traits were similar among the 4 crosses of commercial broilers at 6 wk of age. However, gait scores differed among genotypes, with cross C having better gait scores than crosses A and B, but did not differ from cross D. The bone mineral content and bone size traits did not differ between birds with good walking ability as compared with those broilers of poorer walking ability. However, birds with poorer walking ability had higher BMD (P<0.05) and BW (P<0.001) than males with good walking ability. Within a cross, the correlation between gait score and BMD was not significant except for cross D birds. Broilers of cross D with better walking ability had decreased bone mineralization (r=0.19, P=0.03). The stronger correlation between gait score and BW for all crosses of commercial broilers (r=0.38, P<0.0001) suggests that the low association between gait score and bone mineralization for cross D was mainly due to BW. The BMD of the left toe was correlated to the BMD of the left tibia (r=0.91, P<0.0001) and right tibia (r=0.87, P<0.0001). In conclusion, bone mineralization was similar among crosses of meat-type chickens, and it had little influence on the gait score of male broilers.

The effect of feeder space allocation on productivity and physiology of Hy-Line W-36 hens housed in conventional cages.

Insufficient feeder space for laying hens could increase competition at the feed trough, leading to disrupted feeding, inadequate nutrient intake, stress, and reduced productivity. The effects of feeder space allocation (FSA) on physiology and productivity were evaluated in beak-trimmed Hy-Line W-36 hens (n=480). They were obtained at 16.5 wk of age and housed on 4 tiers of shallow conventional cages. Five pullets/cage were housed at a stocking density of 434 cm2/hen and a feeder space of 12.2 cm/hen. After 1.5 wk of acclimation, baseline measurements were taken for feed utilization, bone mineralization, and heterophil:lymphocyte ratios. At 20 wk of age, pullets were given 5.8, 7.1, 8.4, 9.7, 10.9, or 12.2 cm of feeder space/bird (16 cages/treatment). Physiological and production measures were calculated monthly or twice a month for 12 mo. The heart, spleen, and right adrenal gland were collected from each hen at the end of the study. Data were analyzed using a repeated measures GLM incorporating cage, tier, FSA, and hen age. There were no effects of FSA on total egg production, bone mineral density, bone mineral content, heterophil:lymphocyte ratios, or organ weights. Hens with reduced FSA utilized more feed (P<0.001), had poorer feed conversion (P<0.001), and laid eggs with slightly thicker and heavier shells (P<0.001). There were effects of FSA on total egg weight (P<0.001) and hen-day egg production (P<0.001), but they were of low magnitude and not linear (P>0.05). Because BW was similar among FSA treatments, the results suggest that reduced feeder space did not limit feed intake. In addition, reduced FSA did not lower bone mineralization or cause physiological stress in W-36 hens housed in shallow cages, suggesting that it did not impair hen welfare. However, it did result in poorer feed efficiency, possibly related to greater feed wastage, predictive of an adverse economic effect from reducing feeder space.

Variability in bone mineralization among purebred lines of meat-type chickens.

The variability of bone traits was assessed in purebred lines of meat-type chickens using dual-energy x-ray absorptiometry. Experiment 1 evaluated changes in bone mineralization and size traits of the tibia and humerus in 4 purebred lines from 6 to 24 wk of age. Experiment 2 compared the same traits of the tibia, radius, and ulna of 9 purebred lines at 6 wk of age. Differences in bone traits among purebred lines were apparent in both experiments. Of the 4 purebred lines compared in experiment 1, line C demonstrated the best phenotypic traits relative to bone quality. Even though line C had the longest tibia, one of the largest bone areas, one of the heaviest BW, and one of the highest bone mineral content (BMC) at 24 wk of age, the tibia of line C did not become less dense in mineral as this line of chickens approached sexual maturity as did the tibia of the other purebred lines of chickens. Specifically, its tibial bone mineral density (BMD) showed age-related increases unlike the other purebred lines of chickens, which showed little change in tibial BMD from 6 to 24 wk of age. In experiment 2, all bone traits as well as BW were different among purebred lines (P<0.001). The 2 purebred lines (7 and 8) with the lightest 6-wk-old BW (2,033 and 2,055 g, respectively) had diverse skeletal traits. Birds of line 7 had the lowest BMD (0.1131 g/cm2), BMC (1.05 g), shortest bone length (69.2 mm), and smallest bone area (8.0 cm2); however, the other purebred line low in BW (line 8) showed the opposite trend in that bones from these birds were the highest in BMD (0.1276 g/cm2), BMC (1.38 g), bone length (74.6 mm), and area (9.2 cm2) when compared with all of the other lines. In conclusion, several purebred lines of meat-type chickens expressed large differences in bone traits, suggesting the potential to genetically select birds for increased BMD.

Life cycle changes in bone mineralization and bone size traits of commercial broilers.

Life cycle changes in bone mineralization and bone size traits of the tibia and humerus were evaluated in commercial male and female broilers using dual-energy x-ray absorptiometry (DEXA). Experiment 1 evaluated weekly changes in bone traits from 2 to 7 wk of age, whereas experiment 2 compared the bone traits of 4 strains of commercial meat-type chickens from 4 to 8 wk of age. Birds were restrained without anesthesia, and the humerus and tibia were scanned in vivo. After each scan, individual BW was determined. From the DEXA scans, bone mineral density (BMD), bone mineral content (BMC), as well as bone length, width, and area were determined. Bone mineralization and size traits were analyzed as an analysis of covariance with BW as the covariate. If BW was NS as a covariate, then an ANOVA was used. The BMD reached its peak at 4 wk of age. The BMC of the humerus changed little from 2 to 8 wk of age, whereas tibial BMC increased as the birds aged, especially in males (P < 0.0001). In experiment 1, bone length, width, and area also increased with age (P < 0.0001), with the tibia growing in length at a faster rate than the humerus. In experiment 2, the BMD did not differ among the 4 strains of commercial broilers. Interactions with strain of chicken were also NS, indicating that all strains of chickens responded similarly with respect to age (4, 6, and 8 wk of age), sex, and type of bone (humerus vs. tibia). Coefficients of variation for BMD ranged from 15 to 16%, indicating a potential use of DEXA for selection to improve skeletal integrity. In conclusion, the tibia continued to grow, especially after the initiation of the growth spurt at 3 to 4 wk of age, as indicated by bone length, width, and BMC, but it did not become denser in mineral after 4 wk of age as its surface area increased.