Dry Lot Research Articles

Influence of dairy housing on freshwater usage on commercial dairies in western Kansas (2011)

Fresh water pumping records were obtained from 24 western Kansas dairy farms for a 10-year period from 2000 through 2009. Farms were divided by facility type: dry lot (DL), free stall (FS), or a combination (DL+FS). Of the facility types studied, DL averaged smaller (P < 0.05) demand for water at 52.6 gal/cow per day compared with FS at 61.3 gal/cow. Both DL and FS facilities had less water demand than the combination facilities of DL+FS at 71.1 gal/cow of water daily. In all cases, average freshwater pumping was less than the daily amount of 134.7 gal/cow commonly used in dairy facility design. The difference may result from water conservation efforts of the dairies and the efficiency gained from operating larger milking parlors.

Residual feed intake, body composition, and fertility in yearling beef heifers12

One hundred thirty-seven spring-born yearling beef heifers of British breed types were used to determine the relationships between residual feed intake (RFI) and growth rate, body composition, mature size, and fertility. Heifers were housed in a dry lot facility during the experimental period, and data were collected over a 2-yr period (yr 1, n = 67; yr 2, n = 70). Individual feed intake, BW, BCS, hip height, and ultrasonic measurements [subcutaneous rib fat (UBF), rump fat (URF), LM area (LMA), and intramuscular fat (IMF)] of body composition were recorded. Individual feed intakes (kg of TDN consumed/d) were used to calculate RFI combining both years of data. Heifers averaged 387.0 ± 19.4 d of age and 337.1 ± 29.9 kg of BW at initiation of the experiment. Mean ADG was 1.14 ± 0.21 kg/d during the trial. Based on RFI, with year of test and farm of origin included in the model as covariates, heifers were classified into groups: positive (POS; 0.74 kg of TDN/d) or negative (NEG; -0.73 kg TDN/d) for first analysis and high (HI), medium (MED), or low (LO; mean RFI = 1.06, -0.01, and -1.13 kg of TDN/d, respectively) subsequently. An initial phenotypic relationship (P < 0.05) between RFI and both UBF and URF (r = 0.19 and 0.17, respectively) was sustained (P < 0.01) with UBF (r = 0.27) and URF (r = 0.24) to trial conclusion. No other correlations with RFI were significant. Heifers classified as POS reached puberty earlier than those classified as NEG (414 ± 3.83 vs. 427 ± 4.67 d of age, P = 0.03), and possessed greater LMA per 100 kg of BW (LMACWT) at conclusion of the trial (P < 0.01). Medium heifers exhibited less URF (P < 0.05) compared with either HI or LO heifers at trial initiation. Low heifers possessed less LM area (cm(2)) per 100 kg of BW (P < 0.05) than HI but did not differ (P > 0.10) from MED heifers at either the beginning or the end of test. Additionally, a negative linear relationship was observed between RFI and age at puberty (P < 0.05). Each 1-unit increase in RFI corresponded to a decrease of 7.5 d in age at puberty, but did not affect pregnancy or conception rates (P > 0.10). Differences in body fat and rate of metabolism associated with RFI could delay reproductive maturity.

Age related decreases in thermoregulation and cardiovascular function in horses

Older horses have an increased risk of hyperthermia due to impaired cardiovascular function. While many studies have investigated thermoregulation in horses during exercise, none have investigated the effects of ageing. To test the hypothesis that there is a difference in thermoregulation during exercise and plasma volume (PV) in young and old horses. Study 1: 6 young (Y, 7.7 ± 0.5 years) and 5 old (O, 26.0 ± 0.8 years) unfit Standardbred mares (507 ± 11 kg, mean ± s.e.) ran on a treadmill (6% grade, velocity calculated to generate a work rate of 1625 watts) until core temperature reached 40 °C. Core (CT), skin (ST), rectal temperature (RT) and heart rate (HR) were measured every min until 10 min post exertion. Packed cell volume (HCT), lactate (LA) and plasma protein (TP) were measured in blood samples collected before, at 40 °C and every 5 min until 10 min post exercise. Sweat loss was estimated using bodyweight. Study 2: Plasma volume was measured in 26 young (8.2 ± 0.7 years) and 8 old (26.6 ± 0.7 years) Standardbred mares (515 ± 12 kg) using Evans Blue dye. Pre-exercise blood (rBV) and red cell (rRCV) volumes were calculated using PV and HCT. Data analysis utilised repeated measures ANOVA and t tests and data are expressed as mean ± s.e. Old horses reached 40 °C faster (998 ± 113 vs. 1925 ± 259 s; P < 0.05) with a greater HR at 40 °C (184 ± 6 vs. 140 ± 5 beats/min; P < 0.05) and greater sweat losses (P < 0.05). Heart rate did not differ (P > 0.05) post exercise. Age did not alter (P > 0.05) CT, ST, RT, LA, HCT or TP. Plasma volume was greater in Y vs. O horses (P < 0.05, 28.5 ± 1.4 vs. 24.1 ± 1.6 l) as was rBV (41.3 ± 2.0 vs. 35.3 ± 2.3 l) and rRCV (13.3 ± 0.6 vs. 11.1 ± 0.8 l). Ageing compromises the ability to handle the combined demand of exercise and thermoregulation in part due to decreased absolute pre-exercise PV.

Patterns of Pen Stocking Density on Dry lot and Freestall Dairy Farms in the Western United States

Stocking density in dairy cattle pens appears to affect resting time, feed intake, milk production, lameness, reproduction, hygiene, behavior, and health of the cows. Stocking density can be calculated by the number of linear feet of bunk space per cow, number of cows per freestall, or number of cows per drylot area. Stocking density measures are part of animal welfare auditing guidelines and are important for veterinary investigation of herd health and performance concerns. The purpose of this project was to describe the features of all the cattle pens on large dairy farms in the west and assess farm-level stocking density by pen.

Anthelmintic resistance of Ostertagia ostertagi and Cooperia oncophora to macrocyclic lactones in cattle from the western United States

In June 2008, 122 yearling heifers with a history of anthelmintic resistance were obtained from pastures in northern California and transported to a dry lot facility in southwestern Idaho, USA. Fifty heifers with the highest fecal egg counts were selected for study enrollment. Candidates were equally randomized to treatment with either injectable ivermectin (Ivomec ®, Merial, 0.2 mg kg −1 BW), injectable moxidectin (Cydectin ®, Fort Dodge, 0.2 mg kg −1 BW), oral fenbendazole (Safe-Guard ®, Intervet, 5.0 mg kg −1 BW), oral oxfendazole (Synanthic ®, Fort Dodge, 4.5 mg kg −1 BW), or saline. At 14 days post-treatment, nematodes were recovered from the abomasum, small intestine, and large intestine. Parasitism was confirmed in the control group when 10/10 animals were infected with adult Ostertagia ostertagi and 9/10 animals with both developing and early L 4 stages of O. ostertagi. Similarly, 9/10 animals were parasitized with adult Cooperia spp. Fenbendazole and oxfendazole efficacy verses controls were >90% against adult Cooperia spp., while moxidectin caused an 88% parasite reduction post-treatment ( P < 0.05). Ivermectin treatment resulted in no reduction in adult Cooperia spp. Based on geometric mean percent reduction versus saline controls, all four treatments were ≥90% efficacious against adults of O. ostertagi, while moxidectin and fenbendazole were equally effective against developing and inhibited early L 4 stages ( P < 0.05). Ivermectin was not efficacious for developing or inhibited early L 4 stages of O. ostertagi. Oxfendazole failed to decrease O. ostertagi developing L 4 larvae by >90% but was efficacious for inhibited early L 4 larvae. Based on the results of this study, a source of multi-species anthelmintic resistance in cattle has been identified in the western United States.

The effect of training and cessation of training on plasma total carbon dioxide in Standardbred horses

Twenty-seven mature Standardbred mares (9–27 years, ~522 kg) were used to test the hypothesis that training and short-term cessation of training would alter total plasma total carbon dioxide (tCO2) concentrations. Plasma tCO2 concentrations were measured in blood samples (20 ml) collected at rest from the same ten unfit mares that were used in two separate studies that were conducted 1 month apart. Comparisons between the samples obtained from the two trials were made to demonstrate the consistency of plasma tCO2 concentrations in the untrained population. Another set of resting blood samples was collected from an additional 17 mares that were being utilized in a training study that was under way during the same period. All the mares were housed in groups on dry lots, and were fed approximately 12 kg of mixed alfalfa-grass hay divided into two feedings per 24 h period. During the ‘detraining’ period, the 17 horses were housed in 5 × 5 m stalls, and were fed the same hay ration. Water and trace-mineral blocks were available ad libitum. Blood samples were collected from the mares prior to the last session of their 12 weeks of training at 60% HRmax (maximum heart rate), as well as on the third day following 2 days of detraining (simulated quarantine). Plasma tCO2 concentrations were measured in duplicate using a Beckman EL-ISE analyser. For data analysis, t-tests with the a priori level of statistical significance set at P 0.05) due to cessation of training. It was concluded that training causes a decrease in plasma tCO2 concentrations that is not reversed by limited cessation of training.

Evaluation of a Neck Mounted 2-Hourly Activity Meter System for Detecting Cows About to Ovulate in Two Paddock-Based Australian Dairy Herds

Two studies were conducted to assess the performance of a commercially available neck-mounted activity meter to detect cows about to ovulate in two paddock-based Holstein-Friesian dairy herds. The activity monitoring system recorded cow activity count in 2-hourly periods. Study I investigated the ability of the system to detect cow ovulatory periods in dairy herds managed in two different Australian environments and breeding systems using five activity alert algorithms. Herd 1 consisted of approximately 130 milking cows calving year-round in a sub-tropical environment and kept in a single dry lot paddock. Herd 2 consisted of approximately 400 milking cows calving seasonally in a temperate climate and fed pasture by rotation through multiple grazing paddocks. Ovulatory periods and non-ovulatory days were identified using milk progesterone monitoring alone or in combination with ovarian ultrasonography; using these 'gold standards' 141 and 135 ovulatory periods were identified in 64 and 135 cows in Herds 1 and 2 respectively. Sensitivity of the activity monitoring system for detecting cow ovulatory periods ranged from 79.4% to 94.1%, specificity from 90.0% to 98.2% and positive predictive value from 35.8% to 75.8%. Study II investigated the ability of the activity meter system to predict the timing of ovulations in paddock-based pasture-fed dairy cattle (Herd 2). The time of ovulation was estimated by repeat trans-rectal ovarian ultrasonography at approximately 0, 12, 24 and 36 h after artificial insemination (AI). The mean times (± SD) from onset and end of increased activity to ovulation were 33.4 ± 12.4 and 17.3 ± 12.8 h respectively (n = 94). Fifty per cent of cows (n = 47) ovulated within the 8-h period between 30 to 38 hs after the onset of increased activity, 76.6% (n = 72) within the 16 h between 24 to 40 h, 85.1% (n = 80) within the 24 h between 18 and 42 h and 90.4% (n = 85) within the 32 h from 19 to 51 h after the onset of increased activity. Results from these studies show that in paddock-based dairy cows in two diverse management systems, this neck-mounted activity meter system detects high proportions of cows that are about to ovulate and provides a useful indication of when ovulation is likely to occur. However, the specificities and positive predictive values using the algorithms assessed may be lower than desirable.

Physical composition, primary cuts and meat cuts of carcasses from Zebu and Bos taurus X Bos indicus crossbred cattle

Data on hot carcass weight, hot carcass yield, hindquarter weights and physical components, forequarter and spare ribs, and the weights of the main commercial cuts from the hindquarters of twenty young intact bulls were assessed. The animals, belonging to four genetic groups (Nellore, ½ Guzerath + ½ Nellore (½ G + ½ N), ½ Red Angus + ½ Nellore (½ R + ½ N) and ½ Marchigiana + ½ Nellore (½ M + ½ N)), were raised on pastures, finished in dry lot and slaughtered at live weights ranging from 445 to 517 kg, and at ages ranging from 679 to 863 days. During the dry lot period, which lasted 114 days, animals were fed sorghum silage offered ad libitum, and a concentrate (13.5 MJ of ME, 18% CP in the DM) at 1% live weight per day. Genetic group influenced hot carcass weight, forequarter weight, meat weight in the spare ribs, as well as meat and bone weights in the forequarter. Animals in the ½ M + ½ N group were superior both to those in the Nellore and in the ½ G + ½ N groups for hot carcass weight, forequarter weight and meat weight in the spare ribs. The ½ M + ½ N group also differed from the ½ R + ½ N and from the ½ G + ½ N groups in terms of forequarter weight and meat weight in the forequarter, respectively. Conversely, forequarter bone weight of ½ M + ½ N animals was higher than in animals from the Nellore and the ½ R + ½ N groups, respectively. There was no effect of genetic group on hindquarter cuts, except for higher shank and knuckle weights in the ½ M + ½ N group compared to the ½ G + ½ N and Nellore groups, respectively.

Effect of a feed/fast protocol on pH in the proximal equine stomach

Risk factors for the development of gastric squamous ulcers include various management procedures, such as intermittent feed deprivation that can occur during weight management regimens or stall and dry lot confinement. To investigate the effect of intermittent feed deprivation relative to continuous feed intake on proximal intragastric pH, specifically in the region of the squamous mucosa of the lesser curvature. In 6 horses, pH electrodes were placed just inside of the oesophageal sphincter in the stomach for each of two 72 h protocols (A and B) in a randomised, cross-over design. Protocol A consisted of 12 h fed, 12 h fasted, 24 h fed and 24 h fasted, in sequence. Protocol B consisted of 72 h fed. During the fed periods of each protocol, horses had ad libitum access to coastal Bermuda hay and were fed sweet feed (1 kg, b.i.d.). Horses had ad libitum access to water at all times. Proximal intragastric pH was significantly lower during protocol A, than during protocol B. However, hourly mean pH was significantly different only during the day and evening hours between protocols. During protocol B, mean proximal pH decreased significantly from 03.00 to 09.00 compared to 19.00 to 23.00 h. A moderate positive correlation of hay intake vs. proximal gastric pH could be established. Intermittent feed deprivation decreased proximal gastric pH in horses relative to those horses for which feed was not restricted. However, the effect was only significant when fasting occurred during the day and evening hours, as a nocturnal decrease in pH occurred simultaneously in the fed horses. Episodes of daytime feed deprivation should be avoided if possible, as proximal gastric acid exposure rapidly increases during such events.

Influence of Distillers Dried Grain Supplementation Frequency on Forage Digestibility and Growth Performance of Beef Cattle

<h2>ABSTRACT</h2> Three experiments evaluated the influence of supplementation frequency of distillers dried grains plus solubles (DDGS) on forage digestibility (Exp. 1) and growth of yearling heifers (Exp. 2) and steers (Exp. 3). In Exp. 1, 6 steers (371 ± 30 kg) were used in a replicated 3 × 3 Latin square design with three 21-d periods. Treatments were DDGS fed at 16.7% of the diet (DM) either 1) daily, 2) every other day, or 3) every third day. In Exp. 2, 48 heifers (193 ± 20 kg) were fed hay and supplemented with the daily equivalent of 1.3 kg/heifer of DDGS, either 3 or 6 d/wk. In Exp. 3, 48 steers were assigned to replicated supplementation groups. Treatments were 1) hay and supplement fed 6 d/wk in a dry lot (control); 2) native winter range and supplement fed 6 d/wk; 3) native winter range and a DDGS supplement fed 6 d/wk; and 4) native winter range and the same DDGS supplement fed 3 d/wk. In Exp. 1, diet DM (<i>P</i> = 0.06), OM (<i>P</i> = 0.07), and hay NDF (<i>P</i> = 0.03) digestibility decreased linearly as DDGS supplementation frequency decreased. In Exp. 2, heifers fed DDGS 6 d/wk gained more BW (<i>P</i> = 0.01) than heifers fed 3 d/wk. In Exp. 3, steers fed the control diet, native winter range and supplement fed 6 d/wk, and native winter range and DDGS supplement fed 6 d/wk performed similarly, but performance was decreased when steers were fed native winter range and the DDGS supplement 3 d/wk. Improved animal growth may result from more frequent supplementation of DDGS when fed in excess of 15% of the diet.

Relationships of Milk Production of Beef Cows to Postweaning Gain of the Calves

Milk yield from 158 Brangus cows bred to 6 sire breeds (Bonsmara, Brangus, Charolais, Gelbvieh, Hereford, Romosinuano) was measured for 3 yr to estimate relationships of milk yield of cows and postweaning ADG of their calves on 2 postweaning systems (dry lot or wheat pasture). Milk yield was measured monthly 6 times per year and averaged over 1 mo. Calf postweaning ADG was calculated from the initiation of postweaning management treatments in the fall to the end of spring grazing in April. Calf ADG was regressed on dam 24-h milk yield, and interactions of linear and quadratic regression coefficients with calf sire breed and postweaning treatment of calf were evaluated. In general, regression analyses indicated that calf postweaning ADG was linearly related to dam milk yield, but the relationships depended on the calf sire breed and postweaning treatment (P < 0.01). On dry-lot management, greater cow milk production was associated with lesser postweaning ADG in Gelbvieh- (P < 0.05) and Bonsmara-sired (P < 0.01) calves, whereas greater cow milk production was associated with greater postweaning ADG in Brangus-sired calves (P < 0.01), and a similar trend was observed in Charolais-sired (P < 0.19) calves. On wheat pasture management, greater cow milk production was associated with greater postweaning ADG in Gelbvieh-sired calves (P < 0.11), with a trend for greater cow milk production to be associated with lower postweaning ADG in Romosinuano-sired calves (P < 0.25). Results indicate that accurate determination of the relationship of dam milk production and calf postweaning ADG will require consideration of both calf postweaning management and calf sire breed.

Endurance Training Has Little Impact on Mineral Content of the Third Metacarpus in Two-Year-Old Arabian Horses

Although previous research suggests that short bouts of high-speed exercise will increase bone mass in horses, little research has been conducted to determine the impact of endurance exercise on bone. Although many in the equine industry believe that months of slow training will increase bone strength, we hypothesized that endurance training would not alter bone mineral content as determined through optical density. Eleven 2-year-old Arabians were split into two groups, Exercised (E, 6 geldings) or Control (C, 5 fillies), with radiographs taken on day 0 for estimation of bone mineral content by radiographic bone aluminum equivalence (RBAE). The E horses were then trained on a high-speed treadmill for 90 days; training consisted of walking (1.6 m/second), trotting (4 m/second) and cantering (8 m/second) at increasing distances until the target of 60 km/day was met. On day 90, E horses were confined to 9 × 14 m dry lots and placed on a regular exercise schedule, including a 60-km endurance test once every 3 weeks. The C horses remained on pasture throughout the study. On day 162, radiographs were made again on all 11 horses. No differences between treatments, days, or interactions were noted in any cortex or the total RBAE, suggesting that endurance exercise does little to alter bone optical density compared with free-choice exercise on pasture.

Parenteral Selenium and Vitamin E Supplementation of Weaned Beef Calves

The weaning process in beef calves elicits physiological stress responses that can negatively affect performance and health. Supplementation of vitamins and minerals, particularly selenium (Se) and vitamin E, might be warranted. That parenteral administration of Se or vitamin E would correct or prevent deficiencies of these nutrients in postweaned beef calves during a backgrounding period (42 days after weaning). One hundred and forty-four weaned steers (200-250 kg) in 3 trials. One trial was conducted with cattle on a dry lot fed a total mixed ration and 2 trials were conducted on cattle on pasture. Selenium was administered at 0.05 mg/kg BW (SC) and vitamin E was administered at 1500 IU on days 0 and 28 (SC). A treatment effect attributable to Se or vitamin E supplementation on average daily gain was not detected in any trials. Parenteral supplementation with Se on days 0 and 28 resulted in higher serum Se concentrations as compared with controls on day 42. Parenteral supplementation with Se on days 0 and 28 improved Se status from marginal to adequate in 1 trial. Parenteral supplementation with vitamin E did not improve serum vitamin E concentrations in any experiment. Supplementation with vitamin E or Se or a combination of both did not have a significant effect on calf performance during the 42-day backgrounding period.

Catalogue of the dry specimens in the carcinological collection of the Museu de Zoologia da Universidade de São Paulo, Brazil

The carcinological Collection of the Museu de Zoologia da Universidade de São Paulo (MZUSP) contains more than 400,000 specimens. Among these are 67 lots of dry specimens. This material possesses great historical value, having been collected, identified and studied by eminent researchers. The dry specimens have now been restored by cleaning, dehydration, assembly and sealing. We provide a list of the dry lots, with information on the collection locality, collector and record number. The collection comprises 53 species in 5 infraorders: Brachyura (44 species), Anomura (3), Caridea (1), Palinura (1) and Astacidea (4).

Effects of stocking rate and corn gluten feed supplementation on performance of young beef cows grazing winter-stockpiled tall fescue-red clover pasture1

A winter grazing experiment was conducted to evaluate the effects of stocking rate and corn gluten feed supplementation on forage mass and composition and the BW and BCS of bred 2-yr-old cows grazing stockpiled forage during winter. Two 12.2-ha blocks containing Fawn, endophyte-free, tall fescue and red clover were each divided into 4 pastures of 2.53 or 3.54 ha. Hay was harvested from the pastures in June and August of 2003 and 2004, and N was applied at 50.5 kg/ha at the initiation of stockpiling in August. On October 22, 2003, and October 20, 2004, twenty-four 30-mo-old Angus-Simmental and Angus cows were allotted by BW and BCS to strip-graze for 147 d at 0.84 or 1.19 cow/ha. Eight similar cows were allotted to 2 dry lots and fed tall fescue-red clover hay ad libitum. Corn gluten feed was fed to cows in 2 pastures to maintain a mean BCS of 5 (9-point scale) at each stocking rate and in the dry lots (high supplementation level) or when weather prevented grazing (low supplementation level) in the remaining 2 pastures at each stocking rate. Mean concentrations of CP in yr 1 and 2 and IVDMD in yr 2 were greater (P < 0.10) in hay than stockpiled forage over the winter. At the end of grazing, cows fed hay in dry lots had greater (P < 0.05) BCS in yr 1 and greater (P < 0.10) BW in yr 2 than grazing cows. Grazing cows in the high supplementation treatment had greater (P < 0.10) BW than cows grazing at the low supplementation level in yr 1. Cows in the dry lots were fed 2,565 and 2,158 kg of hay DM/cow. Amounts of corn gluten feed supplemented to cows in yr 1 and 2 were 46 and 60 kg/ cow and did not differ (P = 0.33, yr 1; P = 0.50, yr 2) between cows fed hay or grazing stockpiled forage in either year. Estimated production costs were greater for cows in the dry lots because of hay feeding.

Case Study: Changes in Body Weight, Fill, and Shrink of Calves Grazing Wheat Pasture in the Winter and Spring

AbstractAlthough wheat pasture (Triticum aestivum L.) contains high concentrations of digestible CP and DM, calves may have very low or negative BW gains until they can adapt to this new nutrientrich diet. The objectives of these experiments were to determine changes in BW in stocker calves during the first 28-d period of grazing wheat pasture in the winter and spring and the impact of grazing wheat pasture on the amount of fill lost during fasting. During the spring grazing season, the adaptation period was much shorter than during the winter grazing season. During the winter grazing season, calves grazing wheat forage for the first time had negative BW gains for the first 14 d, but positive BW gains the next 14 d. By d 28 of the winter grazing season, the amount of BW lost during a 16-h fast was less (P < 0.01) for calves on wheat pasture as compared to calves in dry lot (3.99% of BW vs. 5.73% of BW), indicating that they had less GI tract fill. From these data, it is concluded that stocker calves need 14 to 20 d toadjust to the unique chemical com-position of wheat forage during the winter season and less than 14 d in the spring season. Pre-grazing management practices that reduce the duration of the adaptation period will increase overall performance of growing calves.

Dietary protein influences acid-base balance in sedentary horses

Summary The objective of this study was to evaluate acid-base balance of sedentary horses fed 2 levels of dietary protein to determine if protein intake influences acid-base balance. Ten horses of Thoroughbred type were randomly assigned to 2 daily rations with different overall protein concentrations (7.5% low protein [LP] and 12% high protein [HP]). Their rations consisted of 3 meals of a LP or HP concentrate along with grass hay (timothy/orchard grass). Horses were fed to maintain body weight and condition. They were housed in box stalls during the day and turned out in a dry lot at night over an 8-week period. Body weights, body condition score, and venous blood samples were taken every 2 weeks. Plasma was analyzed for total protein, albumin, creatinine, urea-N, pH, lactate, potassium (K+), sodium (Na+), chloride (Cl−), and partial pressure of carbon dioxide (pCO2). Bicarbonate, strong ion difference (SID), and total weak acids (Atot) were calculated. Diets did not have differences in dietary cation-anion difference (DCAD); however, protein intake was different. Horses fed the LP diet had lower urea-N (P = .001), higher blood pH (P = .037), and higher HCO3− (P = .011) compared with the HP group. The LP group had higher SID at the last sampling period (P = .029) and higher K+ at day 42 (P = 0.011). No difference was found for body weight or body condition score. No differences due to diet were found for plasma total protein, albumin, creatinine, lactate, Na+, Cl−, pCO2, and Atot. The difference in pH appeared dependent on SID, with no effect of pCO2 or Atot on pH; however, this may not completely explain the lower pH in the HP group. Since there was no difference in DCAD between the diets, the effect on acid base may be due to dietary protein intake. Excess intake of protein results in oxidation of amino acids and an overall amino acid imbalance that contributes to the acid load and lowering of blood pH as observed in this study.

Effects of short-term feed deprivation and melatonin implants on circadian patterns of leptin in the horse1

Leptin is a protein hormone produced by adipose tissue that influences hypothalamic mechanisms regulating appetite and energy balance. In species tested thus far, including horses, concentrations of leptin increase as animal fat mass increases. The variables and mechanisms that influence the secretion of leptin are not well known, nor is it known in equine species how the secretion of leptin is influenced by acute alterations in energy balance, circadian patterns, and/or reproductive competence. Our objectives were to determine in horses: 1) whether plasma concentrations of leptin are secreted in a circadian and/or a pulsatile pattern; 2) whether a 48-h period of feed restriction would alter plasma concentrations of leptin, growth hormone, or insulin; and 3) whether ovariectomy and/or a melatonin implant would affect leptin. In Exp. 1, mares exposed to ambient photoperiod of visible light (11 h, 33 min to 11 h, 38 min), received treatments consisting of a 48-h feed restriction (RES) or 48 h of alfalfa hay fed ad libitum (FED). Mares were maintained in a dry lot before sampling and were tethered to a rail during sampling. Analyses revealed that leptin was not secreted in a pulsatile manner, and that mean leptin concentrations were greater (P < 0.001) in FED vs. RES mares (17.20 +/- 0.41 vs. 7.29 +/- 0.41 ng/mL). Plasma growth hormone was pulsatile, and mean concentrations were greater in RES than FED mares (2.15 +/- 0.31 vs. 1.08 +/- 0.31 ng/mL; P = 0.05). Circadian patterns of leptin secretion were observed, but only in FED mares (15.39 +/- 0.58 ng/mL for morning vs. 19.00 +/- 0.58 ng/mL for evening; P < 0.001). In Exp. 2, mares that were ovariectomized or intact received either a s.c. melatonin implant or a sham implant. Thereafter, blood was sampled at weekly intervals at 1000 and 1700. Concentrations of leptin in samples collected at 1700 were greater (P < 0.001) than in those collected at 1000 (28.24 +/- 1.7 vs. 22.07 +/- 1.7 ng/mL). Neither ovariectomy nor chronic treatment with melatonin affected plasma concentrations of leptin or the circadian pattern of secretion. These data provide evidence that plasma leptin concentrations in the equine are sensitive to acute changes in nutritional status and vary in a circadian pattern that is sensitive to fasting but not to melatonin treatment or ovariectomy.

Protected canola meal increases milk protein concentration in dairy cows fed a grass silage-based diet

Low concentrations of protein in milk occur during the summer–autumn in south-west Australia. This is the period, on dryland farms, when the diet of lactating cows typically consists of grass silage and a mixture of crushed lupins and cereal grain. This experiment was conducted to test the hypothesis that supplying protected canola meal would increase the protein concentration of milk and, possibly, milk yield in cows fed grass silage and a lupin–cereal concentrate. Sixty Holstein cows in mid lactation were allocated to 2 equal-sized dietary treatment groups: control (lupin) or protected canola meal. The control diet consisted of 14.5 kg DM grass silage (annual ryegrasses–subterranean clover) and 5.4 kg DM of crushed lupins and barley (4:1) per head per day. For the protected canola meal diet, 2.15 kg DM protected canola meal replaced 2.15 kg lupins. The protected canola meal was produced by treating solvent-extracted canola meal with formaldehyde, to produce a product with an in sacco fractional degradability of 0.29 at a rumen fractional outflow rate of 0.08/h. The equivalent degradability of untreated canola meal was 0.80 and of lupin was 0.83. Cows were individually fed the concentrate ration twice daily, after each milking, then were managed as a single herd in dry lots and fed grass silage. By the end of 8 weeks, cows fed the protected canola meal diet had higher milk protein concentrations (30.7 v. 29.2 g/L; P&lt;0.05) and higher liveweights (604 v. 593 kg; P&lt;0.05). Milk yield (L/day) was increased by 1 L/day, but this effect was not significant (P&gt;0.10). Fat concentration was unaffected by diet (P&gt;0.05). Since the only difference in treatment was the replacement of a portion of lupins with protected canola meal, the results indicate that a deficiency of metabolisable amino acids contributes to the low milk protein concentrations recorded during summer–autumn in south-west Australia. Whether this was acting primarily through a stimulus of appetite, or directly on milk components, could not be determined because silage intakes were not recorded.

IMPACT OF ANAEROBIC LAGOON MANAGEMENT ON SLUDGE ACCUMULATION AND NUTRIENT CONTENT FOR DAIRIES

The contents of twelve primary dairy lagoon cells under different management practices in three central Texascounties were evaluated for sludge accumulation and physicochemical characteristics. Composite samples were comprisedof the wastewater column from the top of the lagoon to the top of the dense sludge layer. The composite samples were thoughtto represent a slurry mix typical of agitated lagoon material intended for land disposal. Analyses included pH, total solids(TS), volatile solids (VS), total Kjeldahl nitrogen (TKN), total ammonium-nitrogen (NH4 -N), phosphorus (P), potassium (K),calcium (Ca), magnesium (Mg), sodium (Na), zinc (Zn), copper (Cu), manganese (Mn), and electrical conductivity (EC).<br><br>Statistically, lagoon management practices and treatment effectiveness in terms of reduced sludge accumulation andnutrient content were not strongly linked. However, some practices appear to influence the physicochemical properties of theslurry mix, including use of fresh flush water, increasing the number of treatment cells, and separation of dry lot runoff. TotalKjeldahl nitrogen, P, and K were linearly correlated to TS, indicating higher nutrient concentrations in the anaerobic lagoonsludge. The resultant elevated nutrient levels in the slurry mix, compared to supernatant values, will require greater land areasto meet P-based regulations. Land applying a lagoon slurry mix will require approximately two and a half times as much landarea compared to N-based application rates. Consideration of best management practices (BMPs) may be advised to alleviatelagoon clean-out and sludge disposal challenges.