Influence of maternal plane of nutrition on mares and their foals: determination of mare performance and voluntary dry matter intake during late pregnancy using a dual-marker system.

Thirty pregnant mares (538 to 695 kg BW; 4 to 19 yr of age) were used to evaluate the effects of plane of nutrition on DMI of hay and mare performance (BW, BCS, and rump fat) during the last third of pregnancy. Mares were divided into 4 blocks by their expected foaling date and randomly assigned within block to either a hay or concentrate plus hay diet (concentrate fed at 0.75% BW, as-fed basis) with 15 mares per treatment. Treatments began 110 d before expected foaling date (230 d of gestation) and terminated at parturition. Mares were housed by block and allowed ad libitum access to coastal Bermuda grass (C. dactylon) hay, and concentrate-supplemented mares were fed twice daily in individual stalls. Performance variables were recorded every 14 d, with the last measurements obtained before foaling being considered a prepartum measurement. To evaluate DMI of hay, a dual-marker system was used at 9, 10, and 11 mo of gestation. Titanium dioxide was dosed at 10 g for 14 d. Fecal grab samples were obtained on the last 4 d twice daily via rectal palpation at 12-h intervals with times advancing 3 h each day to account for diurnal variation and to ultimately represent a 24-h period. Fecal samples were analyzed for TiO2 using a colorimetric procedure. Fecal, concentrate, and hay samples were also analyzed for acid detergent insoluble ash. Treatment tended to influence prepartum BW (P = 0.09) and affected prepartum BCS (P < 0.01) and rump fat (P = 0.01), with hay-fed mares having decreased BW and BCS from d 0 (beginning of feeding trial or d 230 of gestation) until parturition, whereas mares fed concentrate gained BW and BCS (P < 0.01). Mares fed only hay consumed 2.3% BW of forage compared with 1.8% BW for concentrate-fed mares (P < 0.01). Regardless of treatment, month of gestation influenced forage intake (P < 0.06), with mares consuming less during the 10th month of gestation and more in the 11th month (1.9% and 2.2% BW, respectively). These data indicate that the altered plane of nutrition of mares in late gestation influenced mare performance. Furthermore, DMI of hay was influenced by both diet and month of gestation. Continued research investigating manipulation of maternal nutrition and its effects on DMI would be beneficial to completely understand the relationships of these observations.

Influence of an intra-articular lipopolysaccharide challenge on markers of inflammation and cartilage metabolism in young horses.

Nineteen weanling Quarter Horses (225 to 380 kg) were used in a randomized complete block design to investigate the effects of intra-articular lipopolysaccharide (LPS) to induce acute joint inflammation in young horses. Horses were blocked by age, BW, and sex and were randomly assigned to 1 of 3 treatments for a 35-d experiment. Treatments included intra-articular injection of 0.25 ng (n = 7) or 0.50 ng (n = 6) of LPS obtained from Escherichia coli O55:B5 or sterile lactated Ringer's solution (n = 6; control) into the radial carpal joint. Synovial fluid was obtained at preinjection h 0 and 2, 6, 12, 24, 168, and 336 h postinjection and was analyzed for PGE2, carboxypeptide of type II collagen (CPII), and collagenase cleavage neopeptide (C2C) biomarkers via commercial ELISA kits. Rectal temperature (RT), heart rate (HR), respiratory rate (RR), and carpal circumference were recorded before each sample. Lameness scores on a 0 to 5 scale were conducted after arthrocentesis. Data were analyzed using PROC MIXED procedure of SAS. Linear and cubic effects were tested in the form of contrasts. Clinical assessment of HR, RR, and RT were not influenced by treatment (P ≤ 0.16). All horses exhibited increased lameness scores over time (P ≤ 0.01), and horses receiving LPS, regardless of dose, had greater recorded lameness scores at 12 and 24 h postinjection (P ≤ 0.05). Joint circumference increased (P ≤ 0.01) across treatments in response to repeated arthrocentesis. Mean synovial fluid PGE2 concentrations increased linearly with increasing levels of LPS administration (P ≤ 0.01). Additionally, regardless of treatment, PGE2 increased over time and peaked at 12 h postinjection (P ≤ 0.01) and remained elevated above baseline at 336 h postinduction. Synovial concentrations of anabolic CPII increased linearly (P ≤ 0.01) with increasing dosage of LPS and increased (P ≤ 0.01) over 24 h in all horses, beginning at 6 h and peaking at 24 h postinjection. Concentrations of C2C in synovial fluid were not influenced by treatment and decreased from 0 to 6 h and steadily increased to 24 h in all horses (P ≤ 0.01). These results indicate that intra-articular LPS induced intra-articular inflammation and collagen synthesis in young horses and that the response is dose dependent. The use of this model to induce predictable joint inflammation may provide insight to the efficacy of preventative strategies relating to joint disease in the young horse.

Influence of dietary methionine concentration on growth and nitrogen balance in weanling Quarter Horses.

Twenty-four Quarter Horse weanlings (120 ± 10 d) were blocked by age into 4 groups (n=6) for a 56-d trial to evaluate the influence of dietary Met concentration on growth and N balance. Weanling horses were housed by block and individually fed concentrates twice daily at 1.75% BW (as-fed basis). Weanling horses were randomly assigned to 1 of 4 concentrate treatments: basal (0.20 Met), basal + 0.03% Met (0.23 Met), basal + 0.07% Met (0.27 Met), and basal + 0.11% Met (0.31 Met). Diets were formulated to be isonitrogenous and isocaloric and contained equal amounts of Lys and Thr. Coastal bermudagrass hay (Cynodon dactylon) was individually fed at 0.75% BW (as-fed basis). Growth measurements, BW, rump fat, and plasma were obtained every 7 d. The final 4 d consisted of total collection of urine and feces. Feed, fecal, and urine samples were analyzed for N content, and N balance was calculated. Urine was analyzed for urea and ammonia concentrations. Plasma was analyzed for urea concentration. Grain, hay, and fecal samples were analyzed for nutrient composition. Data were analyzed using the PROC MIXED procedure of SAS. Linear, quadratic, and cubic effects were tested in the form of contrasts. There was no influence (P>0.25) of treatment on growth measurements, N balance, or urinary urea or ammonia. Intake of Lys and Thr did not differ (P>0.08) among treatments. Methionine intake increased as expected with increasing Met inclusion in the diet (P<0.01). Plasma urea N responded quadratically (P=0.04) to treatment. An unexpected peak in PUN was observed with 0.27 Met. The results indicate future studies that can ensure Met as the only dietary variable are necessary to better explain the Met requirements of weanling horses.