Effect of Restricted Pasture Access on Pasture Dry Matter Intake Rate,Dietary Energy Intake,and Fecal pH in Horses

Eight mature horses were used in a 4 × 4 Latin square design to determine the effect of restricted pasture access on dry matter intake rate (DMIR), energy intake, and fecal pH. Horses were randomly assigned to one of four groups (HGRPs), each containing two horses. HGRPs were randomly assigned to one of four treatments consisting of 3, 6, 9, or 24 hours of pasture access, for a period of 7 days. Treatments were switched every 7 days. The 3- and 6-hour groups were fed free choice mature grass hay while not grazing. Daily pasture dry matter intake (DMI) for each HGRP was estimated by calculating the difference between initial herbage mass of the grazing cell before grazing and residual herbage mass after 7 days of grazing. Total dry matter intake was the sum of pasture and hay DMI for the 3- and 6-hour treatments. Fecal pH was measured on day 7 of each period. Response variables were analyzed using analysis of variance for Latin square design. Restricting pasture access decreased mean pasture DMI (P = .02), pasture dietary energy (DE) (P = .02), and fecal pH (P < .001), but increased DMIR (P = .02). Mean total dry matter intake was not different (P = .16) among treatments. In conclusion, restricting pasture access accelerates pasture DMIR and decreases fecal pH, and although restricting pasture access decreases DE intake from pasture, it did not result in a decrease in total DE intake for horses having ad libitum access to hay.     

Validation and Implementation of an Automated Chew Sensor–Based Remote Monitoring Device as Tool for Equine Grazing Research

Field studies characterizing equine grazing activity primarily rely on observational protocols, limiting the quantity and accuracy of collected data. The objectives of this study were to validate an automated chew sensor technology, the EquiWatch System (EWS), for detecting grazing behaviors and to demonstrate potential applications of the EWS in equine grazing research. Eight mature standardbred mares were used in this study. EquiWatch System validation was completed in two phases: grazing time was evaluated in experiment 1 and chew counts in experiment 2. The correlation between visual observations and system-recorded grazing time was high (concordance correlation coefficient [CCC] = 0.997). There was also a high agreement between the sum of manually counted bites and chews and total chew counts reported by the EWS (CCC = 0.979). Following validation, a pilot study was conducted using the EWS to assess feeding behaviors of horses with unrestricted pasture access (PAS) versus horses offered ad libitum hay (HAY). Horses spent more time engaged in feeding behavior on PAS (14.79 ± 0.48 hr/d) than HAY (11.98 ± 0.48 hr/d; P < .0001). Chewing rate also differed by forage (PAS 83.92 ± 1.61; HAY 68.50 ± 1.61 chews/min; P < .0001). However, although the magnitude of these behavioral parameters was influenced by treatment, the underlying 24-hour patterns were largely preserved regardless of forage type. These results demonstrate that the EWS can generate data necessary for characterizing feeding behavior in horses. Future studies implementing this tool could provide a greater understanding of biological, environmental, and nutritive factors driving grazing behavior in horses.     

Effect of Sward Height on Pasture Nonstructural Carbohydrate Concentrations and Blood Glucose/Insulin Profiles in Grazing Horses

Six mature stock-type geldings with maintenance only requirements were used in a randomized cross-over design to determine the effect of sward height on pasture plant nonstructural carbohydrate (NSC) concentrations and blood glucose and insulin concentrations. Horses were randomly assigned to one of two tall fescue (Lolium arundinaceum Schreb cv Max-Q, Pennington Seed, Madison, GA) grazing cells (0.37 ha) having two different sward heights for a period of 7 days: (1) short (approximately 15 cm; n = 3) or tall (between 30 and 40 cm; n = 3). After the first 7-day period, treatment groups were reversed by moving horses to ungrazed cells having similar characteristics to those used in the first 7 days, so that all horses receive all treatments resulting in six observations per treatment. Both short and tall grazing cells were mowed to a height of approximately 15 cm 32 days before the experiment starts. The short grazing cells were removed to approximately 15 cm at 11 days before the start of the first 7-day period and again 1 day before the start of each 7-day period. All horses had access to pasture for 10 h/d beginning at 8 AM and ending at 6 PM. Although not at pasture, all horses were individually housed in 3.7 × 12.2 m partially covered pens containing automatic water troughs and a crushed stone surface. Herbage mass (kg DM/ha) was determined by use of a falling plate meter for each pasture to ensure that both groups of horses had adequate dry matter to provide grazing for at least 7 days. On day 7 of each period, jugular venous blood samples were collected from each horse before being turned out to pasture, and then at 2, 4, 6, and 8 hours after turn-out. Pasture samples were also collected from each grazing cell at the same time blood samples were taken. Serum and plasma from blood samples were harvested and analyzed for insulin and glucose concentrations, respectively. Pasture samples were analyzed for water soluble carbohydrate (WSC), ethanol soluble carbohydrate (ESC), and starch. The sum of WSC and starch were used as an estimate of NSC. Area under the curve (AUC) and peak concentration were calculated for both plasma glucose (PPG) and serum insulin (PSI) concentration and were analyzed using analysis of variance for randomized cross-over designs. Pasture WSC, ESC, starch, and NSC concentrations were analyzed using analysis of variance for randomized complete block design. A P value of < .05 was considered significant. Mean pasture plant NSC, WSC, and ESC concentrations were lower (P < .001) in short as compared with tall. Pasture plant starch concentration was not different between treatments. Mean pregrazing plasma glucose concentrations, PPG concentrations, and plasma glucose AUC were not affected by treatment. Mean pregrazing serum insulin concentrations were not affected by treatment. Mean PSI and insulin AUC were greater (P < .01) when horses grazed tall, as compared with short. In conclusion, decreasing the sward height by mowing pasture decreased NSC, WSC, and ESC concentrations and subsequently decreased the postprandial insulin response of horses grazing the pasture. These findings may be important in developing strategies aimed at preventing insulin resistance in grazing horses.     

Assessment of Gastric Ulceration and Gastrin Response in Horses with History of Crib-Biting

It was hypothesized that horses exhibiting crib-biting (CB) have a greater degree of gastric mucosal damage and higher serum gastrin response to concentrate feeding than non-crib-biting (NCB) horses. Eighteen mature horses, 9 CB and 9 NCB, were used to determine prevalence and severity of gastric mucosal damage and effect of concentrate feeding on circulating gastrin. Horses were maintained on pasture with free access to hay and fed a pelleted concentrate diet twice daily. Number of crib-bites and duration of cribbing bouts were recorded in a 24-hour period. Endoscopic examinations (EE) of the squamous mucosa were performed and gastric fluid sampled after 24 to 28 hour feed removal. Following EE, horses were returned to pasture for 72 hours. Blood was collected following 12-hour feed removal (0 minutes), and at 60 and 120 minutes after consuming 1 kg of concentrate. Mean number of crib bites in 24 hours was 1,558 ± 303 with CB peaking prior to and during the afternoon feeding (3:30 PM, P < .05). There were no differences in the number or severity of ulcers, prevalence of hyperkeratosis, or baseline gastric pH between CB and NCB. Serum gastrin concentration at 60 and 120 minutes was greater (P < .05) and tended to be greater (P < .06), respectively, in CB than in NCB horses following feeding of concentrate. Crib-biting behavior in horses maintained on pasture was not associated with gastric mucosal damage; however, consumption of concentrate feed resulted in greater serum gastrin concentration in CB horses.     

Effect of Restricted Grazing on Hindgut pH and Fluid Balance

Six mature idle geldings were used in a crossover design to determine the effects of restricted grazing on hindgut pH and fluid balance. Initially, horses were randomly assigned to a control group (CTRL: n = 3) having access to warm-season grass pasture continuously, or a restricted grazing (RG: n = 3) group having access to pasture for 12 consecutive hours (1900-700 hours) per 24-hour period for 7 days; they were then reassigned to the opposite treatment for an additional 7 days (i.e., CTRL: n = 6; RG: n = 6). Fecal samples were collected from each horse at 700 hours on day 7 of each period and analyzed for pH and dry matter (DM) as indicators of hindgut pH and fluid balance, respectively. Jugular blood samples were also collected at 700, 1300, and 1900 hours on day 7 and were analyzed for plasma protein as an indicator of systematic fluid balance. Fecal pH and DM data were analyzed using a paired t test. Plasma protein data were analyzed as a repeated-measures design. The mean (± SE) difference between CTRL and RG for fecal pH (.01 ± .16) and fecal DM (.68 ± .6%) was not significant (P = .93 and .52, respectively). Mean plasma protein concentrations were not affected by treatment or by treatment × sample time interaction, but tended to increase (P = .07) during the sampling period regardless of treatment. In conclusion, 12 hours of grazing restriction followed by 12 hours of grazing did not negatively impact hindgut pH or fluid balance.     

The Effect of Hay Net Design on Rate of Forage Consumption When Feeding Adult Horses

Modern horse management systems tend to limit a horse's opportunity to forage. The objective of this experiment was to investigate the effect of hay net design on the rate of forage consumption when feeding horses. Eight adult horses were fed in individual stalls in a replicated Latin square design, with two horses per treatment per week. Horses were fed hay off the stall floor (control), or from one of three hay nets: large (15.2 cm openings), medium (4.4 cm openings), and small (3.2 cm openings). Horses had access to hay for two 4-hour periods each day. When horses could not consume all forage from the medium and small hay nets in 4 hours, a second study using a crossover design gave horses an unlimited amount of time to feed from the hay nets. Stopwatches were used to calculate time to consumption and dry matter intake rates (DMIR). Mean time to consumption was 3.1 and 3.4 hours for the control and large hay net, respectively, in study 1, and 5.1 and 6.5 hours for the medium and small hay nets, respectively, in study 2. Mean DMIR during the 4-hour feeding period were 1.5, 1.3, 1.1, and 0.9 kg/hr for the control, large, medium, and small hay nets, respectively; all treatments were different (P < .0001). These results demonstrate that hay nets were effective at decreasing the rate of forage consumption when feeding adult horses. Long-term studies are warranted to determine if horses will adapt to feeding from hay nets.     

Interaction of Grazing Muzzle Use and Grass Species on Forage Intake of Horses

The impact of horse preference and grass morphology on grazing muzzle effectiveness has not been investigated. The objective of this study was to determine the effectiveness of grazing muzzle use at reducing forage intake when horses grazed grasses with different morphology and preferences. The study was conducted in 2012 and 2013. Four horses were grazed in 2012, and three horses were grazed in 2013. Four species of perennial cool-season grasses were grazed in 2012 including Kentucky bluegrass (Poa pratensis L.), meadow fescue (Schedonorus pratensis Huds.), perennial ryegrass (Lolium perenne L.), and reed canarygrass (Phalaris arundinacea L.). In 2013, only Kentucky bluegrass and reed canarygrass were grazed because of winter kill of other species. Horses were allowed to graze a small pasture seeded with an individual species for 4 hours each day in June and August of 2012 and August and September of 2013. Horses grazed the same grass species for two consecutive days, one day with a muzzle and one day without. Before and after each grazing, a strip was mechanically harvested to determine initial and residual herbage mass. The difference was used to estimate forage intake. The effectiveness of a grazing muzzle was not affected by forage species (P ≥ .05). Use of a grazing muzzle decreased the amount of forage consumed by an average of 30% compared with not using a grazing muzzle (P < .0001). Results will aid horse owners and professionals in estimating forage intake of muzzled horses on pasture.     

Digestible energy intake, dry matter digestibility and mineral status of grazing New Zealand Thoroughbred yearlings

AIM: To measure the nutritive value of pasture in terms of digestible energy intake (DEI) and dry matter (DM) digestibility, and to determine the effect of Ca, P, Cu, Zn, and Se supplementation on growth rate and degree of physeal swelling in Thoroughbred yearlings grazed on pasture. METHODS: Fourteen yearling horses were randomly allocated to 1 of 2 groups and rotationally grazed on a ryegrass/white clover pasture for 7 months. One group was supplemented daily with a mineral mix. Liveweight changes were recorded at fortnightly intervals and pasture mineral composition determined at monthly intervals. The DM intake (DMI) was determined from daily faecal DM outputs divided by the indigestible DM fraction (1 - digestible DM) determined from a digestibility study. The DEI was determined from the difference between the gross energy intake and the gross energy faecal output. The DM, gross energy content, crude protein (CP), soluble carbohydrate, acid detergent fibre (ADF), neutral detergent fibre (NDF), lipid and mineral composition of pasture offered and faeces were analysed and their digestibility or apparent absorption calculated. RESULTS: The DM digestibility of pasture averaged 0.64 while the daily DMI and DEI of a 350 kg yearling, gaining 0.6 kg liveweight/day, averaged 6.9 kg DM/day and 78 MJ DE/day, respectively. The mineral supplement had no significant effect on the growth of yearlings grazing pasture that had a mineral composition of (g/kg DM) Na 0.17, K 32.8, Ca 3.6, P 3.4, Mg 2.1, S 3.0, and (mg/kg DM) Cu 7.9, Fe 177, Mn 83, Zn 28 and Se 0.016. Plasma Se was elevated (e.g. 40-218 microg/l) by Se supplementation while Cu supplementation had no effect on plasma and liver Cu concentrations. Physeal swelling was observed in all horses, regardless of treatment. CONCLUSION: Good quality ryegrass/white clover pasture that had a DE content of 11.3 MJ/kg DM and adequate mineral composition (as observed in this study, with the possible exception of Se) will provide an adequate intake of nutrients to ensure good growth in yearling horses.     

Determination of the digestible energy intake and apparent absorption of macroelements in pasture-fed lactating Thoroughbred mares

AIM: To measure the nutritive value of pasture in terms of digestible energy (DE) intake (DEI) and dry matter (DM) digestibility, and to determine the apparent absorption of macroelements in lactating Thoroughbred mares grazed on pasture. METHODS: DM intake (DMI) and DEI were determined from daily faecal DM output measured in grazing mares, divided by the DM indigestible fraction (1-digestible DM), measured in a digestibility trial using pasture-fed mares. Eight lactating mares and their foals, that had a mean age of 40 days, were grazed separately on 50x100 m areas of pasture and daily faecal DM outputs were recorded for 8 days. Five mares and their foals were then placed in individual bare 20x20 m corrals containing custom-made feeding stations for 14 days to determine the indigestible DM fraction. DM, gross energy content, crude protein (CP), soluble carbohydrate, acid detergent fibre (ADF), neutral detergent fibre (NDF), lipid, and macroelement composition of the pasture offered and faeces were determined and their digestibility and/or apparent absorption calculated. RESULTS: DM digestibility of the pasture was 0.6 and the DMI and DEI of a grazing 560 kg mare in early lactation nursing a foal growing at 1.34 kg/day was 13.6 (SE 0.8) kg/day and 146.9 (SE 8.4) MJ DE/day, respectively. Apparent absorptions of the macroelements measured were: Ca 0.75, P 0.43, Mg 0.63, Na 0.78, and K 0.72. CONCLUSIONS: Good quality ryegrass-white clover pasture that had a DE content of 10.8 MJ/kg DM, and a macroelement composition (g/kg) of Ca 3.33, P 3.0, Mg 1.67, Na 1.67, and K 24.2, will provide adequate DMI, DEI, and macroelement intake to lactating Thoroughbred mares.     

Protein, energy and dry matter consumption by racing standardbreds: A field survey

A field survey involving 112 Standardbred race horses in 14 stables at a Detroit racetrack was conducted to determine feeding practices of the Standardbred trainers, to estimate crude protein (CP), digestible energy (DE), and dry matter (DM) consumption by racing Standardbreds, and to compare those intakes with 1989 recommendations of the National Research Council (NRC), “Nutrient Requirements of Horses.” Trainers were interviewed regarding: 1) the age and sex of the horses; 2) their feeding practices, and 3) the horse's training and racing schedule. Only adult horses which were actively racing and continuously stabled at the track were included.

Body weights (BW) estimated using a chest girth measurement resulted in an overall mean BW of 449 kg. Body condition scores were established for each horse with an overall mean score of 5.7 which indicated average body condition for a racing Standardbred at this track. Typical rations from each stable were weighed, and feed samples of hays and concentrates were analyzed at a commercial laboratory to determine CP, DM, acid detergent fiber (ADF), and estimated energy density. A computer program calculated CP, DE, and DM values for each horse's ration based on amounts fed. The software program included with the 1989 NRC publication was used to compare estimated nutrient intakes with current NRC recommendations for a horse of a given BW.

All trainers fed a variety of hays and commercial grain mixes, and five trainers fed oats separately. The mean total intake of feed for all horses on an “as fed” basis was 16.1 kg. The estimated mean DM intake for all horses was 14.4 kg vs. NRC recommended 10.6 kg. The mean percentage of rough-age in the ration for all stables was 64% vs. a NRC recommendation of 35%. The mean CP% on a DM basis for all stables' rations was 14.5% vs. the NRC recommendation of 11.4%. The mean daily CP and estimated DE intakes for all horses were 2113 g and 37.6 Meal, respectively, in contrast to current NRC recommendations of 1189 g CP and 29.7 Meal DE. These data indicate that estimated CP, DE, and DM consumption are above the recommendations of NRC in 1989.     

Supplementation of cottonseed,linseed, and noug seed cakes on feed intake,digestibility, body weight,and carcass parameters of Sidama goats

A digestibility, feed intake, and carcass evaluation experiment using 20 yearling intact male Sidama goats weighing 16.4 ± 0.63 kg (mean ± SD) was conducted in Ethiopia with the objectives to determine feed intake, digestibility, body weight (BW) gain, and carcass parameters. The treatments included feeding natural pasture hay (T1, control) and supplementation with cottonseed cake (284 g—T2), linseed cake (250 g—T3), and noug seed cake (296 g—T4) on dry matter (DM) basis to supply 85 g crude protein (CP) per head per day. Randomized complete block design for feed intake and BW parameters and complete randomized design for digestibility and carcass parameters were used. Hay DM intake was higher (P < 0.01) for T1 than for the other treatments. T3 promoted higher (P < 0.01) DM (29.3 g/kg W^0.75/day) and CP (14.1 g/kg W^0.75/day) intake than T4 (8.9 g/kg W^0.75/day DM and 4.1 g/kg W^0.75/day CP). T3 showed better (P < 0.05) organic matter and CP digestibility than T2. Goats in T3 had higher nitrogen intake (P < 0.01) and retention (P < 0.05) than those in T1. Goats in T2 and T3 showed higher (P < 0.05) daily BW gain and final BW than those in T4 and T1. Goats in T2 and T3 had higher (P < 0.05) slaughter weight, empty BW, hot carcass weight, rib-eye muscle area, and dressing percentage on slaughter weight basis than those in T1. The results showed that T2 and T3 had similar effect on CP intake, daily BW gain, and carcass parameters for growing Sidama goats fed natural pasture hay.     

Effect of feeding increasing quantities of starch on glycaemic and insulinaemic responses in healthy horses

The aim of this study was to investigate the effect of increasing the intake of starch on the glycaemic and insulinaemic responses of horses. A cross-over study design was used in which four horses were fed increasing amounts of a compound feed (0.5–3.5 kg) to provide 0.3, 0.6, 0.8, 1.1, 1.4 and 2 g starch/kg bodyweight (BW)/meal. The glycaemic response increased with starch intake (P < 0.05), while feeding <1.1 g starch/kg BW resulted in a lowered response, compared to when 1.1–2 g starch/kg BW was fed (P < 0.01). The results suggested that insulin responses may be more appropriate to define the effect of feeding different starch levels than glycaemic responses. A starch intake of <1.1 g/kg BW/meal produced only moderate glucose and insulin responses, even though highly processed cereals were used. It is therefore recommended that a starch intake of <1.1 g/kg BW/meal or a meal size of 0.3 kg/100 kg BW (starch content of 30–40%) is used for horses.     

Digestible energy intake, dry matter digestibility and effect of increased calcium intake on bone parameters of grazing Thoroughbred weanlings in New Zealand

AIMS: To measure the nutritive value of pasture in terms of digestible energy intake (DEI) and dry matter (DM) digestibility, and the effects of increased calcium (Ca) intakes on apparent mineral absorption and bone characteristics in grazing weanling Thoroughbreds. METHODS: DM intake (DMI) and DEI were determined in 16 weanling Thoroughbreds grazing pasture from their daily faecal DM output, measured over 8 days, divided by the DM indigestible fraction (1-digestible DM) determined in a 6-day digestibility trial. The DM, gross energy content, crude protein, soluble carbohydrate, acid detergent fibre, neutral detergent fibre, lipid, Ca, phosphorus (P), sodium (Na), potassium(K), sulphur (S) and magnesium (Mg) composition of perennial ryegrass/white clover pasture and faeces were determined and their digestibility and/or apparent absorption calculated. Calcium intake and bone growth studies used 17 weanlings, randomly divided into three groups and fed perennial ryegrass/white clover pasture and 0.5 kg grain, with or without a CaCO3 supplement, for 84 days. The animals in Group 1 (n=6) were on a low Ca diet (3.5 g/kg DM) and were fed pasture only; those in Group 2 (n=5) were on a medium Ca diet (6.3 g/kg DM);and those in Group 3 (n=6) were on a high Ca diet (12.0 g/kg DM). After 44 days the apparent absorption of Ca was determined from the differences between the Ca intakes and faecal Ca outputs. At periods just before and after Ca supplementation the horses were anaesthetised and the left radius, third metacarpus(Mc3) and first phalanx of the left foreleg were scanned using a peripheral quantitative computed tomography scanner to determine cortical mineral content, density, area, periosteal circumference and bone strength. To investigate gastrointestinal tract transit time and DM digestibility, five randomly selected horses were administered Swiss screen bags on several occasions via a nasogastric tube. Each 60 x 10mm bag contained 3.21 (SE 0.37) g of frozen minced grass. Bags were recovered from the freshly passed faeces and frozen until analysis. RESULTS: The DM digestibility of the pasture was 0.62, while the DMI and DEI of weanlings (300 kg, gaining 0.7 kg/day) were 5.5 kg/day and 63 MJ/day, respectively. Increasing Ca intake had no significant effect on DEI, DM digestibility or on the apparent absorption of Ca, P, Na and K, but decreased the apparent absorption of Mg from 0.50 to 0.38. Regardless of Ca intake, the apparent absorption of Ca was 0.56. During the Ca administration trial there were significant increases overtime in the bone strength (strain stress index) of the proximal phalanx, Mc3 and radial diaphysis. However, the increase in bone strength was not associated with increase in dietary Ca, as neither the medium- nor high-Ca intake groups differed significantly from the low-Ca controls. The mean transit time for the Swiss screen bags was 25.46 (SE 0.09) h, and transit times were similar whether the horses were grazing or confined in loose boxes, being 26.64 (SE 0.23) h and 24.33 (SE 0.13) h, respectively. The DM digestibility determined using the bags was 0.54, which was significantly lower than the 0.62 determined by direct faeces collection. CONCLUSIONS: Good growth rates were achieved in Thoroughbred weanlings grazing perennial ryegrass/white clover pasture containing 3.5 g Ca/kg DM and a DE of 11.4 MJ/kg DM. Increasing dietary Ca intake 3.5-fold for 3 months had negligible impact on bone growth and development.     

The Effect of Feeding Two or Three Meals Per Day of Either Low or High Nonstructural Carbohydrate Concentrates on Postprandial Glucose and Insulin Concentrations in Horses

Eight mature idle gelding horses (mean body weight [BW], 558 ± 45 kg) were used in a replicated 2 × 2 Latin square design study. Horses received either two or three meals per day (MPD) for 7 days, of either a high (H; 43%; 215 g/100 kg BW) or low (L; 18%; 90 g/100 kg BW) nonstructural carbohydrate (NSC) concentrate feed to achieve four treatment groups: low NSC in two MPD (L2), low NSC in three MPD (L3), high NSC in two MPD (H2), and high NSC in three MPD (H3). On day 7 of the treatments, blood was collected before (baseline) and for 5 hours after feeding the morning meal (10, 20, 30, 40, 50, 60, 90, 120, 150, 180, 210, 240, 270, and 300 minutes after feeding). Baseline insulin concentrations tended (P = .093) to be higher for horses fed high NSC than low NSC, and horses fed two MPD tended (P = .092) to have higher baseline insulin concentrations than horses fed three MPD. In addition, baseline glucose-to-insulin ratio (GIR) was higher in horses fed high NSC compared with low NSC (P < .001). Horses fed high NSC had higher area under the curve of insulin and higher peak insulin after feeding than those fed low NSC. These findings suggest that NSC content of a concentrate feed has an impact on baseline insulin and GIRs and on postprandial insulin concentrations. Meanwhile, the number (and therefore size) of MPD had fewer impacts on glucose metabolism.     

Effects of diet and climate on growing horses

The effects of diet and climate were assessed in 42 light horse weanlings over 30 wk. Horses were fed diets varying in energy and phosphorus content. Diets were predominantly forage (73 to 77.5%) or concentrate (62 to 62.25%) and had 2.65 or 3.09 Mcal DE/kg DM, respectively. Horses were weighed every 14 d. Group feed intakes and climatic variables were recorded daily. Dietary phosphorus content did not affect intake or gain. Horses fed forage diets ate 18% more (P less than .001) DM than horses fed concentrate, but DE intakes did not differ. Average DE intakes, 21.5 Mcal daily, were 33% more than those given in 1978 National Research Council (NRC) tables. Overall ADG by forage- and concentrate-fed horses were .83 and .89 kg, respectively. These values were 23 and 32% above mean ADG values given for horses at 6 and 12 mo in 1978 NRC tables. Average daily gain declined (P less than .01) with age, although daily DE intake increased (P less than .01). Total DM and DE intakes were determined largely by body weight, but age was the main determinant of weight-scaled DE intake. Weight- and age-scaled DE intakes were reduced (P less than .001) by 6.1% at temperatures below -10 degrees C compared with temperatures above -10 degrees C. Temperatures below -20 degrees C had no greater effect on DE intake than those between -10 to -20 degrees C. Neither precipitation nor wind alone affected weight- and age-adjusted DE intake. In conclusion, weanling horses fed readily digested diets ad libitum gained weight at or above expected values even at severely cold ambient temperatures.     

Evaluation of bovine rumen contents as a feed for lambs

This study evaluated effects of increasing levels of dried rumen contents (DRC) on voluntary intake, growth performance, digestibility, nutritive value, N utilization, microbial protein supply (MPS), and purine derivatives excretion (PDE) of lambs fed with Afzelia africana basal forage. Sixteen lambs (13.7?±?0.1 kg body weight (BW)) were randomly assigned to one of the four eight diets containing 0, 200, 400 and 600 g DRC/kg dry matter (DM) in a completely random design. Intakes of concentrate, DM, crude protein (CP), organic matter (OM), digestible CP (DCP), digestible OM (DOM), digestible energy (DE) and metabolizable energy (ME), CP and OM digestibility, DOM, DCP, DE, ME, N intake and retention, weight gain, cost/kg BW gain, MPS and PDE increased with increasing DRC level up to 400 g/kg DRC and declined at 600 g/kg DRC (P?<?0.05; 0.01). Feed conversion ratio and DM digestibility declined as DRC level increased from 0 to 400 g/kg and peaked at 600 g/kg DRC (P?<?0.05; 0.01). Forage intake and DE/DCP ratio decreased (P?<?0.05; 0.01) progressively with increasing DRC level. Results indicate that DRC can be incorporated up to 400 g/kg in a compounded ration for sheep.     

Reducing phosphorus inputs for grazing Holstein steers

A 2-yr study was conducted to confirm that managed pastures can provide Holstein steers adequate P to meet their daily requirement. Treatments offered were trace mineralized salt with or without additional P. In the first year, 80 Holstein steers (248 kg of BW) were assigned to 4 grazing groups. Treatments were trace mineralized salt only or a 67:33 mixture of trace mineralized salt and dicalcium phosphate. Steers rotationally grazed a cool-season grass/legume mixture for 137 d. Fecal bags were placed on 3 steers from each grazing group (n = 12) over a 4-d period for estimation of forage DMI and forage contribution to daily P intake twice during the grazing season. Analyzed pasture samples contained 3.28 mg of P/g of DM. During the second year, 72 Holstein steers (297 kg of BW) were blocked into 2 BW groups and subsequently assigned to 1 of 4 pasture groups. Steers rotationally grazed the same forage base as the first year for 126 d. Pasture samples contained 3.27 mg of P/g of DM. No significant differences (P > 0.10) were detected for BW, ADG, or free-choice supplemental mineral intake. Forage provided 126% of the recommended NRC P requirement. Thus, supplemental phosphorous was not required for Holstein steers grazing mixed, cool-season, grass/legume pastures.     

Corn oil supplementation to steers grazing endophyte-free tall fescue. I. Effects on in vivo digestibility, performance, and carcass traits

Eighteen Angus steers (438 +/- 4 kg of BW) were supplemented with varying levels of corn oil (0 g/kg of BW, none; 0.75 g/kg of BW, MED; or 1.5 g/kg of BW, HI) on rotationally stocked, endophyte-free tall fescue to determine the effect of supplemental oil level on in vivo digestibility, intake, performance, and carcass traits. Pelleted cottonseed hulls were used as a carrier for the oil supplements, and all supplements were offered to steers using Calan gate feeders for individual intake determination. On d 49, each steer was dosed with a controlled-release capsule containing chromium sesquioxide, and fecal samples were obtained 12 d later over a 7-d period to estimate fecal output that, with forage, supplement, and fecal indigestible NDF concentration, was used to estimate DMI and in vivo total diet digestibility. Steers were slaughtered at the end of the 116-d grazing period, and carcass data were collected at 24 h postmortem. Total fatty acid intake linearly increased with corn oil supplementation, and forage DMI, total DMI, and total DE intake were linearly decreased (P < 0.01). The decrease in total DMI was reflected in forage substitution rates greater (P < or = 0.01) than 1, with a trend (P = 0.09) for a greater substitution rate in HI than in MED. In vivo DM, OM, and NDF digestibility were linearly decreased (P < 0.01) by corn oil supplementation. Average daily gain and final BW tended (P = 0.09) to increase linearly in response to oil level. Oil conversion (0.36 kg of BW gain/kg of corn oil) was greater (P < or = 0.05) than zero and did not differ (P = 0.15) between MED and HI. Dressing percent (P = 0.09), carcass weight (P = 0.01), and carcass backfat thickness (P = 0.01) increased linearly with oil supplementation. No treatment effect was observed for carcass LM area, KPH percentage, marbling score, or yield grade (P > 0.10). Oil supplementation to grazing steers linearly reduced forage DMI intake; however, animal performance was maintained and tended to be greater for oil-supplemented cattle. Oil supplementation increased carcass fat thickness and weight without altering other carcass quality parameters.     

Evaluation of Factors Contributing to Daily Within-Horse Variation of Plasma Alpha-Tocopherol Concentration

The current study was conducted to evaluate daily within-horse variation of plasma alpha-tocopherol concentration (TOC) (Experiment 1 [EXPT1]) and to determine the effect of a single meal on plasma TOC (Experiment 2 [EXPT2]). In EXPT1, venous jugular blood samples were collected from four pregnant (6–7 months of gestation), light horse mares (8.8 ± 2.9 years of age, mean ± SD; range, 5–11 years of age) between 7:30 AM and 8:30 AM, followed by eight hourly samples, and analyzed for plasma TOC. All horses were fed 5 kg dry matter (DM) grass hay 18 hours before sample collection and received no additional feed during the sampling period. Mean within-horse coefficient of variation for TOC was 3.5% ± 0.01%. In EXPT2, seven mature light horses, four mares and three geldings (4.9 ± 4.4 years of age, mean ± SD; range, 2–14 years of age), were randomly assigned to one of two treatments (fasted [FST; n = 7] or fed [FD; n = 7]), followed by reversal of treatments 24 hours later. At 7:30 AM, FD horses were fed 2.1 kg DM grain-mix concentrate (187 IU vitamin E/kg DM) plus 3.3 kg DM mixed-grass hay, whereas FST horses received no feed. Neither group received any feed for 18 hours before 7:30 AM. Venous jugular blood samples were collected at 10:30 AM from all horses and analyzed for plasma TOC. The mean (±SD) within-horse paired-treatment difference was not significant (0.05 ± 0.12 μg/mL). The results suggest that variation in within-horse plasma TOC is relatively small over an 8-hour period in fasting horses and is unaffected 3 hours after a hay grain meal.     

Fecal pH and Microbial Populations in Thoroughbred Horses During Transition from Pasture to Concentrate Feeding

Abrupt dietary transitions and feeding of rapidly fermentable diets are common practices in the horse industry and have been associated with digestive and metabolic disorders that can impair the performance of horses. The present study investigated the effect of dietary transition from pasture grazing to confinement with concentrate feeding, and back, on fecal pH and bacterial populations of Streptococcus spp and Lactobacillus spp. Six Thoroughbred fillies, previously grazing perennial ryegrass and white clover-based pasture, were housed in individual stalls and fed an increasing ratio of concentrate to conserved forages for 13 days (days 1-13), followed by an abrupt transition back to only pasture-grazing for 3 days (days 14-16). The concentrate was initially offered at 0.83 kg dry matter (DM)/d and increased to 5 kg DM/d, whereas ensiled alfalfa was initially offered at 0.61 kg DM/d, increasing to 1.22 kg DM/d. Meadow hay was initially offered at 6.73 kg DM/d, decreasing to 1.6 kg DM/d. Fecal specimens were collected daily for determination of pH, and every 2 days for quantitative analysis of Streptococcus spp and Lactobacillus spp. Mean fecal pH increased significantly from pasture baseline values (pH 6.18) during the initial confinement and supplementation on day 1 (6.37), day 2 (6.52), day 3 (6.58), and day 4 (6.43) (standard error of mean [SEM]: 0.056; P < .001). By day 5, mean fecal pH values had decreased to, and remained at, baseline values until the horses returned to pasture, when another increase occurred at day 15 (6.45). Fecal colony forming units (cfu) of Streptococcus spp and Lactobacillus spp increased linearly (r = 0.94; P < .001) from 6.0 and 6.1 log₁₀ cfu/g on day -4, to 7.8 log₁₀ cfu/g on day 14 (SEM: 0.2 P < .001), respectively. Fecal cfu decreased on return to a pasture-only diet (P < .001). In this study, the increment of bacterial populations was associated with a relatively stable fecal pH and highlights the difficulty in identifying the effects of dietary transition on the equine hindgut health, without microbial culture.