Dairy Replacement Heifers Research Articles

The role of extensionists in Santa Catarina, Brazil, in the adoption and rejection of providing pain relief to calves for dehorning

The majority of dairy calves around the world are dehorned with methods that cause them pain and distress. In some dairy production systems, extensionists may influence dehorning practices used on farm through their advisory and knowledge-transfer role. The aims of this study were to investigate Brazilian extensionists’ knowledge, beliefs, and behavior regarding dehorning dairy calves. As little research has addressed this question, a qualitative, theory-building approach was used and the theory of planned behavior was used as a conceptual framework to guide data collection and analysis. In-depth, semi-structured interviews were undertaken with 15 extensionists working in Santa Catarina, Brazil, to examine their role in the adoption and rejection of pain-mitigation strategies at dehorning. The interview transcripts were free coded, identifying 9 major themes within and across interviews. Transcribed interview responses were then coded to constructs in the theory of planned behavior. The themes and constructs that emerged through analysis of the interview responses were combined to develop a conceptual model of extensionists’ beliefs, attitudes, and behavior toward recommending protocols for dehorning aimed at minimizing pain. The extensionists interviewed believed that it was necessary to dehorn all dairy replacement heifers. Despite being aware of methods to minimize pain during and after dehorning, all of the interviewees recommended or used the hot cautery method, with no pain control. This method was described as the most effective, cheapest, safest, and fastest method of dehorning. The majority (12) of interviewees rejected the caustic paste method, citing negative past experiences or unfamiliarity with the method and the belief that the method is less practical and riskier for farmers. More than half of the interviewees did not recognize dehorning as painful or expressed the belief that the pain associated with the procedure did not justify the use of pain control. Although a small number of extensionists (4) recognized potential sources of social pressure to change, including the rejection of pain-inflicting practices by some farmers, the Brazilian general public, and animal-protection societies, they did not identify these factors as a reason to change their existing practices. Interviewees expressed the belief that the adoption of practices to minimize pain and stress, such as dehorning very young calves, using caustic paste and pain control, would increase labor and costs associated with dehorning. Extensionists’ negative attitudes toward recommending practices that minimize pain during and after dehorning appear to be embedded in the production-focused political and economic agriculture environment and a lack of education, research, and legislation regarding farm animal welfare.

Effects of co-grazing dairy heifers with goats on animal performance, dry matter yield, and pasture forage composition1

Mixed livestock grazing can offer an alternative management system for rearing dairy replacement heifers (Bos taurus). A 2-yr study was conducted during 2009 (yr 1) and 2010 (yr 2) to determine the effects of co-grazing Holstein heifers under rotational stocking with Boer × Kiko goats on animal performance, pasture DM yield, and botanical composition. Each year, 24 heifers (134 ± 6 d of age and 147.4 ± 31.2 kg BW in yr 1; 166 ± 11 d of age and 168.0 ± 27.6 kg BW in yr 2) and 6 goats (2 yr old and 39.7 ± 16.2 kg BW in yr 1; 1 yr old and 33.7 ± 7.4 kg BW in yr 2) were divided into 6 paddocks with 4 heifers and 2 goats, where applicable, per group. Low endophyte-infected tall fescue (Festuca arundinacea Schreb.) and white clover (Trifolium repens L.) pastures were used to evaluate 2 grazing strategies (heifers grazed alone [HO] or heifers co-grazed with goats [HG]). In addition, 6 goats were assigned to 2 paddocks and grazed alone (GO) each year to estimate goat pasture forage intake and compare Haemonchus contortus infection to co-grazed goats. Forage samples were taken monthly to assess DM yield and botanical composition. Samples collected for botanical composition were manually sorted into grass, legume, and weed species. Forage DMI was estimated using a rising plate meter before and after grazing. Heifer BW at the conclusion of yr 1 and yr 2 did not differ between HO and HG (P = 0.40 and P = 0.12, respectively). Likewise, overall ADG did not differ between HO and HG, averaging 0.65 kg/d and 0.63 kg/d over both grazing seasons (P = 0.70). Grazing strategy did not affect forage or total DMI in yr 1; however, HO consumed 2.3 kg/d more forage DM than HG (P < 0.01), resulting in greater total DMI for HO in yr 2 (P < 0.01). Heights at the hip and withers were greater for HO than for HG during both grazing seasons (P < 0.05). Weed presence did not differ between grazing strategies over both grazing seasons as determined by manual harvesting, but visual estimation of botanical composition at the end of yr 2 showed that HO paddocks had 3.5 times more weed presence than HG pastures (P < 0.01). Within the confines of this study, co-grazing did not affect overall heifer BW gain, but it decreased DMI, suggesting that dairy heifers can be co-grazed with goats without negative effects on ADG or feed efficiency.

Using eastern gamagrass to construct diets that limit intake and caloric density for dairy replacement heifers

Previous research has shown that eastern gamagrass (EGG; Tripsacum dactyloides L.) will survive winter climatic conditions common throughout central Wisconsin, and will produce yields of dry matter (DM) ranging approximately from 7,000 to 10,000kg/ha annually when managed with a 1-cut harvest system. The objective of this research was to determine whether the fibrous nature of this perennial warm-season grass could be effective in reducing the caloric density and DMI of corn silage/alfalfa haylage diets for replacement dairy heifers. A total of 120Holstein dairy heifers were blocked by body weight (heavy, 424±15.9kg; medium, 369±11.8kg; light, 324±22.4kg), and then assigned to 15 individual pens containing 8heifers each. Eastern gamagrass forage was harvested, ensiled, and subsequently incorporated into blended corn silage/alfalfa haylage diets at rates of 0, 9.1, 18.3, or 27.4% of the total dietary DM (EGG0, EGG9, EGG18, and EGG27, respectively). These diets were offered during a 105-d evaluation period for ad libitum intake; however, the EGG0 diet also was offered on a limit-fed basis (LF), which was set at 85% of the voluntary intake of EGG0. Serial additions of EGG increased concentrations of neutral detergent fiber in blended diets from 39.6 (EGG0) to 48.7% (EGG27), and simultaneously reduced corresponding estimates of total digestible nutrients (TDN) from 68.2 to 61.3%, and net energy for gain from 1.07 to 0.83Mcal/kg. Dry matter intakes for all diets offered ad libitum were greater than observed for LF (9.06 vs. 8.07kg/d); however, DM intakes for diets containing EGG were reduced relative to EGG0 (9.40 vs. 8.94kg/d). Similarly, intakes of TDN were greater for diets offered for ad libitum intake than for LF (5.84 vs. 5.50kg/d); however, inclusion of EGG reduced TDN intakes relative to EGG0 (6.41 vs. 5.65kg/d). This reduction was explained by both linear and quadratic effects of the inclusion rate of EGG in the diet. Over the 105-d trial, total weight gains ranged from 89kg (0.85kg/d) for heifers offered EGG27 up to 114kg (1.09kg/d) for those offered EGG0. Performance was similar between heifers offered EGG27 and LF diets (0.85 vs. 0.88kg/d). Eastern gamagrass haylage proved to be a completely nonsortable additive within corn silage/alfalfa haylage diets. It also was effective in limiting the caloric density and DM intake of these diets, as well as undesirable weight gains by dairy heifers.

Bovine abortion Part 2: Appraising the laboratory evidence to identify the risks on-farm

A small hill farm milked 80 Friesian-cross cows: it reared most of its dairy replacement heifers, but bought-in a few mature cows from auction each year. All breeding cattle were vaccinated once yearly against bovine viral diarrhoea virus (BVDv), bovine herpesvirus-1 and Leptospira hardjo. During a six week period at the beginning of 2011, four cows aborted and a full investigation was carried out on the last of these. Radiological examination of the fetal tibia showed the pregnancy had been disrupted first about five weeks before the cow aborted. The fetus died from hypoxia, probably associated with multiple focal myocarditis of either viral or parasitic origin. Results from serological examination of acute and convalescent blood samples obtained from the dam, interpreted within the context of her previous vaccination history, suggested that recrudescence of N. caninum infection together with re-exposure to BVDv were the main risk factors for abortion occurring in this case.

Evidence of the genetic trend for secondary sex ratio in Iranian Holsteins

Calving records from the Animal Breeding Center of Iran collected from January 2000 to December 2007 and comprising 520964 Holstein calving events from 2135 herds were analysed using animal and sire models to estimate variance components, heritabilities and genetic trends for secondary sex ratio (SSR) in the first, second and third parities. Direct heritabilities for SSR ranged from 0.00004 to 0.001 over the parities. The linear sire model estimate of heritabilities for SSR in the present study was from 0.0002 to 0.0008 over the parities. There were positive phenotypic and genetic trends for female rate in Iranian Holsteins over the years. Exploitable genetic variation in SSR can take advantage of sexual dimorphism for economically important traits, which may facilitate greater selection intensity and thus greater response to selection, as well as reducing the replacement costs. On the other hand, increasing genetic and phenotypic trends for female rate in the population under study could be partly assigned to increased use of new reproductive technologies in dairy herds; therefore, dairy farmers have the option to select from among their herd's potential dams and produce dairy replacement heifers from only the genetically superior animals, thus promoting enhanced rates of genetic gain.

Factors Affecting High Mortality Rates of Dairy Replacement Calves and Heifers in the Tropics and Strategies for Their Reduction

The tropics is not an ideal location for calf rearing as the high temperatures and humidities introduce many potential disease problems to milk fed calves. In addition, the type of dairy farming (generally poorly resourced small holder farming) and the general lack of awareness of the long term implications of poorly reared stock do not encourage farmers to pay close attention to their calf and heifer rearing systems. Surveys of calf rearing systems in Asia, tropical Africa and South America highlight the high calf and heifer mortalities. A range of 15 to 25% pre-weaning calf mortality is typical on many tropical dairy farms. It is often as high as 50%, indicating very poor calf management. This contrasts with US findings of less than 8% mortality from birth to 6 months while surveys of Australian farmers report only 3% losses. Simple extension programs on farms in Sri Lanka and Kenya have drastically reduced calf mortalities and improved pre-weaning growth rates. Improved management strategies leading to lower calving intervals, higher calving rates, reduced still born and pre-weaned calf mortalities and fewer non pregnant heifers can supply many more dairy herd replacements than currently occurs. Such strategies can increase the number of replacement heifer calves in the herd from 15 to over 35%, thus allowing farmers to increase their herd sizes through natural increases. Simple management procedures such as ensuring adequate intake of good quality colostrum within the first 12 hours of life, housing and good hygiene to minimise disease transfer, providing clean drinking water, developing appropriate feeding protocols to encourage early rumen development and paying closer attention to climate control and animal health can all lead to improved calf vigour and performance. Good record keeping is also important so farmers can more easily identify susceptible calves and quickly treat potential problems.

Orchardgrass Ley for Improved Manure Management in Wisconsin: II. Nutritive Value and Voluntary Intake by Dairy Heifers

Confinement dairy feeding operations in the Upper Midwest could benefit from using a wider range of forages than alfalfa (Medicago sativa L.) and corn silage (Zea mays L.). A short‐term ley of orchardgrass (Dactylis glomerata L.) (OG) frequently treated with manure, was compared with corn silage (CS) in a 2 × 2 factorial trial conducted across 3 yr at two locations in Wisconsin. Nutrients were applied as either manure (M) or fertilizer (F) to meet crop N needs. Weighted on the basis each cut contributed to the total annual yield of OG, concentrations of crude protein (163 g kg−1) and 48‐h neutral detergent fiber (NDF) digestibility (657 g kg−1 NDF) were suitable for incorporation into the diets of dairy cows (Bos taurus) and replacement heifers. Tissue concentrations of P and K were 3.7 and 32.0 g kg−1, respectively. High tissue concentrations of P can help with soil‐test P drawdown, and reduce purchases of supplemental dietary P. Although heavy manuring resulted in high tissue K, especially in late‐season cuts, K concentrations were not significantly greater in the hay‐production years relative to the seeding year in either M or F. Based on results with 483 ± 37.6 kg Holstein heifers, there were no differences in voluntary intake by heifers offered commercially fertilized compared to manured OG hays. These results indicate that an OG ley system could be part of a larger alfalfa–corn silage rotation, providing confinement dairies with an alternative forage option, and additional manuring opportunities during summer months.

Bio-economic model to evaluate twinning rate using sexed embryo transfer in dairy herds

A stochastic bio-economic model has been used to determine the effects of new reproductive technologies over a 15-year period. A strategy of using conventional artificial insemination (AI) or embryo transfer (ET) using two sex-controlled embryos at different conception rates (CRs) and herd sizes resulted in a 24 state model. The genetic means of AI population increased over the years, and the genetic means of milk production for all of the embryo strategies were greater than those of AI. In addition, the genetic means of milk yield using different embryo-based scenarios in the expanding herds were greater than those for the fixed herds. The net profit of using sexed ET in the expanding herds was greater (P < 0.05) than that of fixed size herds. In general, there was a roughly consistent trend in net profit per cow for sexed ET strategies in the expanding herds over the years, but there was an increasing trend in net profit per cow for sexed ET strategies in the fixed herds over the years. Medium to high CRs for ET and the use of sex-controlled embryo systems, especially for induction of twin births to produce dairy replacements, will be critical elements of a system that produces significant numbers of female calves. The greater number of female calves produced in the sex-controlled scenarios allows the farmer to select animals with the best genetic potential as dairy replacement heifers; therefore, the rate of genetic gain increased in the dairy herd. Results of sensitivity analyses showed that a significant decrease in the production costs and increase in the ET performance are essential for embryo-based technologies to be profitable.

Unique Dairy Applications of Eastern Gamagrass Forages in Central Wisconsin: II. Nutritive Value and Energy Density

Recently, perennial warm‐season grasses have received considerable interest, largely through bioenergy initiatives, but their suitability for limiting caloric intake by fiber‐demanding livestock classes, such as dairy replacement heifers (Bos taurus) and/or dry cows has not been explored. Our objectives were to evaluate eastern gamagrass [Tripsacum dactyloides (L.) L.] forages harvested from nine single‐ or double‐harvest systems with four N fertilization regimes for macromineral, protein, and fiber composition, and then to estimate the energy densities for these forages by the summative approach. Across the 3‐yr trial, concentrations of neutral‐detergent fiber (NDF) from single‐harvest systems increased with mostly linear (P &lt; 0.001) and quadratic (P = 0.010) effects of harvest date, reaching maximum concentrations ranging from 746 to 801 g kg−1 by early or mid‐August. Similarly, concentrations of lignin increased with delayed harvest dates across single‐harvest systems in predominantly linear (P &lt; 0.001) patterns. Generally, concentrations of lignin were lower than reported for eastern gamagrass forages grown at more southerly latitudes, and ranged from 37.5 to 46.0 g kg−1 in mid‐August. As a result, estimates of total digestible nutrients (TDN) determined by the acid‐detergent lignin option for calculating truly digestible fiber remained relatively high through mid‐August (582 g kg−1). Adjusting truly digestible fiber on the basis of the alternate in vitro 48‐h neutral‐detergent fiber digestibility (NDFD) approach resulted in reduced TDN estimates for eastern gamagrass. In northern climates, eastern gamagrass forages have large concentrations of NDF, and could be used to dilute dietary energy for livestock species with low or moderate energy requirements.

Unique Dairy Applications of Eastern Gamagrass Forages in Central Wisconsin: I. Yield Potential

Replacement dairy heifers (Bos taurus) offered diets comprised largely of corn (Zea mays L.) silage or other high‐energy forages often become overconditioned, which may damage their future performance as lactating cows. Our objective was to assess the yield potential of a perennial C4 grass, eastern gamagrass [Tripsacum dactyloides (L.) L.], for incorporation into fiber‐demanding, dairy‐heifer or dry‐cow diets. Replicated field plots of ‘Pete’ eastern gamagrass were evaluated within nine harvest systems and four N fertilization regimes. For single‐harvest systems, dry matter (DM) yields increased across harvest dates, reaching numerical maximums of 7192, 9764, and 7554 kg ha−1 by mid‐August of 2007, 2008, and 2009, respectively. During each year, there was a strong linear (P &lt; 0.001) effect of harvest date; however, higher‐ordered effects varied within year. Relatively large yield increases (≥1812 kg ha−1) between early and mid‐August during 2008 and 2009 suggest that better yields could be achieved by delaying single harvests of eastern gamagrass beyond mid‐August. Yields of DM from double‐harvest systems were not competitive with single‐harvest systems timed in mid‐August. Nitrogen fertilization increased (P &lt; 0.001) DM yields, exhibiting both linear (P &lt; 0.001) and quadratic (P = 0.027) effects of application rate. However, efficiency of N usage was reduced as fertilization rates increased.

Review: Behaviour and its role in the nutritional management of the growing dairy heifer

There has recently been a significant increase in the amount of scientific research relating dairy cattle behaviour to nutritional management, particularly with respect to the interaction with health. Much of this research has been focused on using information on the natural behavioural patterns of dairy cattle to improve management practices. As with calves and mature dairy cattle, the behaviour of growing replacement dairy heifers interacts with various nutritional management practices. For replacement dairy heifers, much of the research in this area has been focused on how these interactions relate to different feed delivery methods, the amount of feed provided, and stocking density at the feed bunk. This review describes empirical work focused on understanding how nutritional management practices affect heifer behaviour, and how these practices may affect the health, productivity, and welfare of these animals. In particular, evidence will be provided for those practices (such as total mixed ration feeding, feeding for ad libitum intake, and reducing feed bunk competition) that promote feeding behaviour patterns related to more consistent nutrient intake and improved rumen health. Even though the behavioural effects of these nutritional practices are known, additional research is still needed to further demonstrate the possible physiological consequences (e.g., rumen pH, growth rate) of these changes in behaviour. This information is needed so that further recommendations can be made on these practices so these animals may be raised for maximum production potential, while maintaining their behavioural needs, health and overall welfare.Key words: Behaviour, nutritional management, replacement dairy heifer

Nutritional Management of the Dairy Heifer to Maximize Growth and Productivity

The dairy replacement heifer has historically been considered to be only a cost to the dairy operation and not a potential profit center. Dairy heifers have a tremendous genetic capability to utilize nutrients in their diet to maximize growth and reach puberty at a much earlier age than previously thought. If heifers are provided with sufficient amounts of protein and energy in the right ratios, they can reach puberty and breeding height and weight by 11 months of age without adverse affects on ease of calving, reproductive efficiency or milk production. Heifers on this higher plane of nutrition also have a lower incidence of morbidity and mortality, thus increasing the number of heifers available as replacements on the dairy. This allows the dairy to expand internally without the purchase of outside animals for replacements, as well as increase the rate of voluntary culling.

Contract Rearing Programs for Replacement Dairy Heifers

The demand for contract heifer-rearing business is growing because environmental, land, capital, and labor requirements on producing dairy farmers is increasing, especially among larger farms. Specialized growers that offer cost competitive services that return a quality heifer are in demand. Growers that provide good facilities and management can prevent common heifer diseases and provide consistent gains so heifers will calve at 24 months or less. Good accounting and record systems allow for the goals of the grower and dairy to be monitored and achieved.

Feed delivery method affects the learning of feeding and competitive behavior in dairy heifers

The objective of this study was to determine how different feeding methods may affect the learning of feeding, sorting, and competitive behavior of growing dairy heifers. We hypothesized that heifers previously fed a total mixed ration (TMR) would distribute their feeding time more evenly throughout the day, sort the new ration less, compete less for feed, maintain a more solid fecal consistency, and continue to grow rapidly compared with heifers previously fed a top-dressed ration (TDR). Thirty-two Holstein heifers (237.2±21.9 d of age) were divided into 8 groups of 4 and exposed to 1 of 2 treatments for 13 wk: 1) TMR or 2) TDR, with each containing 65% grass/alfalfa haylage and 35% textured concentrate on a dry matter (DM) basis. Following this feeding period, all heifers were switched to an unfamiliar TMR containing 56.1% grass/alfalfa haylage, 21.0% corn silage, 21.0% high-moisture corn, and 1.9% mineral supplement (DM basis) for 7 wk. Group DM intakes were recorded daily throughout the experiment. Feeding behavior, recorded using time-lapse video, and sorting behavior were measured for 7 d during wk 1, 4, and 7 after the dietary change. Feeding competition was measured on d 2, 4, and 6 of each recording week. Sorting activity was determined through particle size analysis of the fresh feed and orts. The particle size separator separated feed into 4 fractions (long, medium, short, and fine). Sorting of each fraction was calculated as actual intake expressed as a percentage of predicted intake. Animals were scored for fecal consistency twice weekly, using a scale from 1 (liquid) to 4 (solid). Heifers were weighed every 2 wk. Neither DM intake (9.0 kg/d) nor average daily gain (1.2 kg/d) differed between treatments. Sorting also did not differ between treatments. Heifers tended to spend more time feeding if they had previously been fed a TDR (198.8 vs. 186.8 min/d). As they had done before the dietary change, heifers previously fed the TDR spent more time at the bunk in the 2h following feed delivery (40.6 vs. 25.9 min/d). Heifers previously fed the TDR were displaced from the feed bunk more frequently than heifers previously fed the TMR (23.0 vs. 13.1 times/d), particularly during the 2-h period following feed delivery. Fecal scores were lower (more fluid in consistency) for heifers originally fed the TDR (3.2 vs. 3.7). The continued difference in feed bunk competition suggests that heifers previously fed the TDR had learned these patterns in the past, retaining them even when switched to an unfamiliar ration. Furthermore, lower fecal scores for heifers previously fed the TDR suggest altered rumen fermentation, possibly because of altered diurnal consumption patterns. These results show that feeding a TMR to replacement dairy heifers from a young age promotes a more even diurnal feeding pattern, minimizes feed bunk competition, and promotes a more solid fecal consistency.

Effect of feed delivery method on the behavior and growth of dairy heifers

The objective of this study was to determine the effects of feed delivery method on growth, feeding competition, feeding, and sorting behavior of dairy heifers. Thirty-two Holstein heifers (146.2±21.9 d of age) were divided into 8 groups of 4 and exposed to 1 of 2 feed delivery treatments for 13 wk. The treatment rations contained 65% grass/alfalfa haylage and 35% textured concentrate (on a dry matter basis) fed as a 1) total mixed ration (TMR) or 2) top-dressed ration (TDR). Group dry matter intakes were recorded daily throughout the experiment. Feeding behavior, recorded using time-lapse video, and sorting behavior were measured for 7 d during each of wk 1, 5, 9, and 13. Sorting activity was determined through particle size analysis of the fresh feed and orts. The particle size separator separated feed into 4 fractions (long, medium, short, and fine). Sorting of each fraction was calculated as actual intake expressed as a percentage of predicted intake. Heifers were fecal scored for consistency of stool twice weekly using a scale from 1 (liquid) to 4 (solid); heifers were weighed every 2 wk. Neither dry matter intake (7.3 kg/d) nor average daily gain (1.3 kg/d) differed between treatments. Heifers fed the TDR tended to consume less neutral detergent fiber than heifers fed the TMR (4.77 vs. 4.91 kg/d). Heifers fed the TDR sorted against long particles (98.9 vs. 96.0%) and consumed short particles (100.3 vs. 101.1%) to a greater extent than did heifers fed the TMR. Daily feeding time did not differ between treatments (201.0 min/d), but heifers on the TDR did spend more time at the bunk in the 2h following feed delivery (50.1 vs. 32.0 min/d). Heifers fed the TDR were displaced from the feed bunk more frequently than heifers fed the TMR (17.6 vs. 8.6 times/d), particularly during the 2-h period following feed delivery. Fecal scores were lower for heifers on the TDR (2.7 vs. 3.4). These results suggest that feeding a TMR to replacement dairy heifers may promote a more even diurnal feeding pattern, minimize feed sorting and feed bunk competition, and promote more solid fecal consistency.

The effect of treatment with long-acting antibiotic at postweaning movement on respiratory disease and on growth in commercial dairy calves

Bovine respiratory disease (BRD) is a major concern when raising replacement heifers because of the high incidence and long-term effects of this disease, such as decreased growth and increased time to first calving. The objective of this study was to determine the effect of tulathromycin (TUL) treatment at postweaning movement on the incidence of BRD in dairy replacement heifers. A total of 1,395 heifers were enrolled between November 2006 and June 2007 at a commercial heifer-raising facility. Calves were randomly assigned either to treatment with TUL or to a positive control group treated with oxytetracycline (TET). Calves treated with TUL were 0.5 times (95% CI: 0.4 to 0.7) less likely to be treated for BRD in the 60 d following enrollment than calves treated with TET. For calves that had no history of BRD in the pre-enrollment period, TET calves weighed 4.9±0.5kg less than TUL calves after 6 wk in group housing. If calves were treated for BRD in the pre-enrollment period, there was no treatment effect on growth. Calves with clinical BRD in the 60 d following movement weighed 7.9±0.6kg less than calves without BRD after 6 wk in group housing. Treatment with TUL at the time of movement to group housing had a beneficial effect on the health and performance through the prevention of BRD in dairy calves with no prior history of the disease. Moreover, BRD after movement to group housing after weaning had a significant effect on the growth of dairy calves.

The effect of winter diet on the weight gain and body condition score of weanling dairy replacement heifers

The effect of winter diet on the weight gain and body condition score of weanling dairy replacement heifers

Evaluation of the performance of in-calf dairy heifers either housed or out-wintered on forage brassicas (stubble turnips)

There is increased interest in out-wintering systems which have the potential to reduce costs and hence increase farm profitability. Out-wintering also offers the potential to increase herd size, within the constraints of Nitrate Vulnerable Zone (NVZ) restrictions without the substantial capital costs associated with waste storage. The majority of out-wintering research has focused on kale and its utilisation by dry dairy and suckler cows where relatively modest performance levels are required. In a comprehensive review on forage brassica for out-wintering stock (MDC 2007) it was stated that “despite the developments in New Zealand in the use of brassica based out-wintering systems for dry dairy cows, there seems to be no detailed studies on the use of these systems for growing (0.7-0.85kg daily live weight gain [DLWG]) dairy heifers”. The objective of this experiment was therefore to evaluate the performance of replacement dairy heifers either housed or out-wintered on forage brassicas (stubble turnips).

Risk factors associated with Neospora caninum infections in cattle in Argentina

From 2003 through 2007, serum samples from 5594 dairy and beef heifers and cows in Argentina were assessed to quantify the association between presence of Neospora caninum antibodies and history of abortion, type of exploitation, and age category of animals. Animals with a history of abortion were 85% more likely ( P < 0.01) to be positive to N. caninum than animals without a record of abortion. For a given category (age) of animals, being in a dairy operation increased the odds of being N. caninum-positive. Replacement dairy heifers were 76% more likely ( P < 0.01) to be N. caninum-positive than beef cows. These results suggest that postnatal exposure may be more frequent in dairy operations than in beef herds and provide insight into the epidemiology of the disease in one of the most important livestock production regions of the world.

Effects of Fescue Type and Sampling Date on the Nitrogen Disappearance Kinetics of Autumn-Stockpiled Tall Fescue ,

Two tall fescue [Lolium arundinaceum (Schreb.) Darbysh] forages, one an experimental host plant/endophyte association containing a novel endophyte that produces low or nil concentrations of ergot alkaloids (HM4) and the other a typical association of Kentucky 31 tall fescue and the wild-type endophyte (Neotyphodium coenophialum; E+), were autumn-stockpiled following late-summer clipping and fertilization with 56kg/ha of N to assess N partitioning and ruminal disappearance kinetics of N for these autumn-stockpiled tall fescue forages. Beginning on December 4, 2003, sixteen 361±56.4-kg replacement dairy heifers were stratified by weight and breeding, and assigned to one of four 1.6-ha pastures (2 each of E+ and HM4) that were strip-grazed throughout the winter. Pastures were sampled before grazing was initiated (December 4), each time heifers were allowed access to a fresh pasture strip (December 26, January 15, and February 4), and when the study was terminated (February 26). Generally, fescue type and the fescue type×sampling date interaction exhibited only minor effects on total forage N, or partitioning of N within the cell solubles or the cell wall. For pregrazed forages, concentrations of N and N partitioned within the cell solubles both declined in a strongly linear relationship with sampling dates. In contrast, concentrations of cell-wall–associated N changed in erratic and often higher-ordered relationships with time, but the magnitude of these responses generally was limited. Unlike the partitioning of N within cell-wall and cell-soluble fractions, kinetic characteristics of ruminal N disappearance frequently exhibited interactions of fescue type and sampling date. For pregrazed forages, these included interactions for all response variables, and for postgrazed forages, fractions B and C, as well as rumen degradable protein. Ruminal disappearance rate for pregrazed E+ and HM4 exhibited quadratic (range=0.057 to 0.082/h) and cubic (range=0.057 to 0.075/h) relationships with time, respectively. For postgrazed E+ and HM4 forages, ruminal disappearance rate was unaffected (mean=0.066/h) or only tended to be affected by sampling date (mean=0.065/h), respectively. Concentrations of rumen degradable protein exhibited various curvilinear relationships with sampling dates, but disappearance was consistently extensive, and the overall range was relatively narrow (71.3 to 78.9% of N). These findings suggest that ruminal disappearance of N for autumn-stockpiled tall fescue forages remains extensive throughout the winter months and is only affected minimally by fescue type, sampling date, and grazing status.