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Cows fed diets consisting primarily of stored forages and concentrates may be at risk for vitamin A deficiency because these feedstuffs are low in ß-carotene. Furthermore, dietary vitamin A concentrations of the cow during late gestation will affect vitamin A concentrations in colostrum, which calves rely on at birth to supply vitamin A. The objective of this study was to evaluate how level of vitamin A supplementation from mid-gestation to early lactation affected cow and subsequently, liver retinol concentrations of their calf. Multiparous beef cows (n = 54) were stratified by body condition score and previous source and assigned to pen (n = 9); 3 pens were assigned to each of the following treatments: current NASEM recommendation (31,000 IU/d; 1X), 3 times (93,000 IU/d; 3X), or 5 times (155,000 IU/d; 5X) the current NASEM recommendation for supplemental vitamin A. Cows were limit-fed a diet consisting of wheat straw, corn silage, and wet distillers grains. Liver biopsies were collected on cows 3 weeks before treatment initiation, d 40 and d 81 of supplementation, and both cows and calves were sampled 32 days post-calving (165 ± 22 d SD of supplementation). No differences (P=0.86) in initial cow liver retinol (mean 186 μg/g DM) were observed between treatments. A significant treatment × day interaction (P < 0.01) was observed for cow liver retinol. On d 40, cows in 1X had liver retinol concentrations (178 μg/g DM) that were not different (P = 0.12) from 3X (213 μg/g DM) but less (P = 0.02) than 5X (241 μg/g DM), while 3X and 5X did not differ (P = 0.21). Liver retinol on d 81 was less (P < 0.05) in 1X (189 μg/g DM) compared with 3X (334 μg/g DM) and 5X (412 μg/g DM), which did not differ (P = 0.20). For cow liver retinol post-calving, 1X (187 μg/g DM) was less (P< 0.05) than 3X and 5X, and 3X (454 μg/g DM) was less (P< 0.05) than 5X (674 μg/g DM). Liver retinol concentrations of 1X cows remained below adequate reference ranges (300-700 μg/g of DM) throughout the study, whereas 3X and 5X were increased into the adequate range by d 81. Calf liver retinol concentration also differed among treatments (P = 0.01), as calves of cows in 1X had less (P < 0.05) liver concentrations than 3X and 5X calves which did not differ (P=0.12). Liver retinol concentrations considered adequate for calves at 32 days of age (100-350 μg/g of DM) were not observed in 1X calves (51 μg/g DM) but were observed in calves from 3X and 5X cows (119 and 165 μg/g DM, respectively). Supplementing cows with 93,000 IU/d of vitamin A for 165 days brought liver retinol concentrations of cows and their calves up within adequate reference ranges. [ABSTRACT FROM AUTHOR]

In the young calf, vitamin A is particularly important for immune system maturation, and calves rely on colostrum at birth to supply vitamin A. Cow vitamin A status may influence colostral vitamin A concentrations, which can impact vitamin A status of their calves. Very little is understood about this relationship between beef cow and calf vitamin A status. Furthermore, limited data is available on how plasma and liver retinol concentrations in cattle are related to one another. The objective of this study was to examine relationships between liver and plasma retinol concentrations in the cow, calf, and within cowcalf pairs. Multiparous MARC II beef cows (n = 120; 6.4 ± 1.2 SD years of age; 592 ± 58 SD kg BW) in mid-gestation were provided supplemental vitamin A as retinyl acetate in a supplemental pellet at a rate of 21,125 ± 8,560 SD IU/d (current NASEM recommendation = 33,000 IU/d). Cows were individually fed using Calan gates a diet consisting of alfalfa hay, corn silage, and supplemental pellet for 144 d (111 d pre-calving and 32 d post-calving). Basal diet vitamin A concentration was 490 IU/kg of DM. Mean initial liver concentration of cows was 830 μg retinol/g of DM. To assess vitamin A status, liver biopsies and plasma samples were collected on cows and calves at the end of the supplemental period when calves averaged 32 ± 7 days of age (DOA). Pearson correlations were used to test for linear relationships between cow liver and plasma retinol concentrations, calf liver and plasma retinol concentrations, and liver and plasma retinol concentrations between the cow and her calf. No linear relationship (P = 0.10; r=0.16) was observed between liver and plasma retinol in cows. In the present study, mean cow liver retinol concentration (482 ± 182 SD μg/g of DM) fell within the current adequacy reference range of 300–700 μg/g of DM. Cow plasma retinol (272 ± 40 SD ng/mL) was slightly below the reference range of 300–800 ng/mL. A positive correlation (P < 0.01; r=0.37) was detected between calf liver (51 ± 27 SD μg/g of DM) and plasma (190 ± 47 ng/mL) retinol concentrations. Both were below what would be considered adequate (100–350 μg/g of DM in liver; 225–325 ng/mL in plasma) for calves at 32 DOA. There was a positive correlation (P < 0.01; r=0.31) between cow and calf liver retinol, suggesting that as cow retinol liver concentrations increased, calf liver retinol concentrations increased. It appears that despite cows having adequate liver retinol concentrations when 21,125 IU vitamin A/d was fed, it did not result in calf liver retinol stores that would be considered adequate given current reference ranges. USDA is an equal opportunity employer and provider. [ABSTRACT FROM AUTHOR]

A two-yr study was conducted to measure reproductive responses of an alternative cow-calf production system. Multiparous, crossbred cows (n = 160; average age = 5.7 ± 2.8 yrs-old) were utilized, per yr, in a generalized randomized bock design and unstructured treatment design. In yr one, cows were blocked by origin source and age, randomly assigned to one of two production systems, each with four replicates (n = 20 cows/rep). Once allotted to treatment and replicate, cows remained in assigned treatment for the duration of their productive life. Treatments were: 1) traditional extensive spring calving system utilizing perennial pasture and corn residue grazing (TRAD); 2) alternative fall-calving system utilizing confinement, summerplanted oats, and corn residue grazing (ALT). Breeding body condition score (BCS) was greater (P < 0.01) for TRAD compared to ALT (6.45 vs. 5.47 ± 0.159, respectively). There were no differences (P ≥ 0.24) in conception rates (93.86 vs. 94.14 ± 2.26 %), pregnancy loss (4.37 vs. 5.62 ± 1.86 %), calving rates (89.50 vs. 88.49 ± 3.06 %), and weaning rates (86.88 vs. 82.50 ± 3.08 %) for TRAD and ALT, respectively. There was no difference (P = 0.47) in calf body weight at birth (40 vs. 39 ± 1.0 kg) for TRAD and ALT, respectively. Weaning BCS was greater (P < 0.01) for TRAD compared to ALT (5.71 vs. 5.27 ± 0.048). Calves in the TRAD system had greater (P < 0.001) wean BW (237 vs. 185 ± 3.7 kg) compared to ALT calves. Cows from TRAD system had greater (P < 0.001) kg weaned per cow exposed to bulls (208 vs. 151 ± 6.3 kg) compared to ALT cows. Results indicate no difference in reproductive performance among systems. The extensive spring-calving system produced heavier calves at weaning, leading to more kg of calf weaned per cow exposed. [ABSTRACT FROM AUTHOR]