Effect of sequential implanting with zeranol on steer lifetime performance

Three trials involving 513 exotic crossbred steers were conducted to determine the effect of zeranol implanting in the suckling and growing phases on subsequent feedlot performance and carcass characteristics. Treatments were 1) unimplanted control, 0000; 2) implanted twice in the finishing phase, 00II; 3) implanted in the growing phase and twice in the finishing phase, 0III; 4) implanted in the suckling phase and twice in the finishing phase, I0II; 5) implanted in the suckling and growing phases with a single implant in the finishing phase, III0; and 6) implanted in the suckling and growing phases and twice in the finishing phase, IIII. Implanting in the suckling period did not significantly affect preweaning gain. Implanting in the growing period produced a treatment x trial interaction (P less than .05), but zeranol increased gains by an average of 8.4% over the three trials. Growing period gain was not influenced by implanting during suckling. Implanting twice during the finishing period increased gain (P less than .05) over unimplanted and III0 steers. Finishing gain was not influenced by previous suckling and(or) growing implant treatment. Lifetime ADG of steers was increased (P less than .05) by all implant treatments compared with unimplanted controls. Zeranol tended (P = .14) to improve feed conversion in the finishing phase. All implant treatments increased hot carcass weight (P less than .05), and all but III0 reduced fat deposition, as indicated by lower quality grade (P less than .05). Other carcass characteristics were not significantly affected by treatment. These trials demonstrated that implanting in the suckling and(or) growing phases of production did not reduce performance in the finishing phase.     

Weight gain in steer and heifer calves treated with zeranol or oestradiol 17 beta

Male and female Hereford and Hereford cross beef calves between 2.5 and 4.5 months of age were implanted with 36 mg zeranol, 24 mg oestradiol 17 beta or left untreated, and then weighed every 4 to 5 weeks. Calves treated with zeranol or oestradiol 17 beta gained 9.6 kg (8.2%) and 12.9 kg (11.0%) more weight respectively than untreated calves. Steer calves gained more weight than heifer calves. There was no response to either growth promotant in heifers or in zeranol-treated steers beyond 35 days after implantation, and the only significant further gains in the next 31 days were made by steers treated with oestradiol 17 beta. After this time growth of treated and control calves was similar. The lack of a continued response to the growth promotants was not associated with significantly lower growth rates in any weighing interval.     

The effects of zeranol on growth and fattening in beef calves before weaning

Four-month-old beef calves were implanted with 36 mg zeranol, and their growth compared with untreated calves. Treated steer and heifer calves gained 10 kg more bodyweight to weaning at 7.5 months of age. The trial was conducted at 2 research centres and calves at both centres showed significant responses for the first 45 days (P less than 0.001) after treatment but during the following 30 days only calves at one centre showed a continued response (P less than 0.05). No differences in growth rate occurred between treated and untreated calves over the final 30 days before weaning at either centre. The backfat measurement of untreated animals increased more than that of the implanted animals (P less than 0.05) at one centre but not at the other.     

Effect of pre- and postweaning zeranol implant on steer calf performance

One hundred ninety-five steer calves were assigned to five zeranol implant treatment (trial 1). Treatments were no implants (0000), two implants during the finishing period (00XX), three implants during growing and finishing periods (0XXX), one implant at 1 to 2 mo of age during the suckling period and two during the finishing period (X0XX) or four implants (XXXX). The growing period implant was administered at weaning. Weaning weights (211 vs 208 kg) of implanted and nonimplanted suckling calves were not different (P greater than .05). Calves implanted at weaning, before shipment to the feedlot, had greater (P less than .05) weight loss in shipment than nonimplanted calves. In the feedlot, finishing-period daily gains of steers implanted in the growing and finishing period (0XXX) were greater (P less than .05) than gains of steers that had received a suckling period implant (X0XX and XXXX). Nonimplanted steer gains were less (P less than .05) than gains of steers from the other four treatment groups. Postweaning daily gains and final weights were 1.18 and 517 (0000), 1.26 and 533 (00XX), 1.32 and 551 (0XXX), 1.26 and 540 (X0XX) and 1.25 and 533 kg (XXXX), respectively. Gains and final weights of nonimplanted steers were less (P less than .05) than gains of steers implanted only in the feedlot growing and finishing periods (0XXX). In a second trial, 82 steers were assigned either to a 0XXX or XXXX implant scheme. Weaning weights were 11 kg greater (P less than .05) for the implanted steers.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of photoperiod on hepatic growth hormone receptor 1A expression in steer calves

Photoperiod manipulation, specifically a long-day photoperiod (LDPP), increases milk production in lactating cattle. We have previously reported that the galactopoietic effect of LDPP is associated with an increase in circulating IGF-I, which seems to occur independently of changes in concentrations of GH, IGFBP-2, and IGFBP-3. This study tested the hypothesis that LDPP increases the expression of GH receptor (GHR) 1A messenger RNA (mRNA) in the liver. Two groups of Holstein steer calves (98 +/- 4 d old) were maintained indoors and exposed to LDPP (16-h light: 8-h dark; n = 6) or short-day photoperiod (SDPP; 8-h light: 16-h dark; n = 6) for 60 d. Calves were individually fed a grain- and alfalfa-based diet. Jugular blood samples were collected weekly and via cannula at 15-min intervals for a 4-h period on d 1, 26, and 55 of the study to monitor pulsatile hormone secretion. Serum was harvested and assayed for IGF-I, prolactin (PRL), and GH using RIA. Liver biopsies were obtained at 3-wk intervals to quantify changes in hepatic IGF-I and GHR 1A mRNA using real-time PCR. Steer BW increased during the study but did not differ between treatments. No differences in ADG or total DMI were observed. Relative to SDPP, calves on LDPP had higher (P < 0.05) serum IGF-I concentrations. Concentrations of PRL increased (P < 0.01) in calves exposed to LDPP compared with calves exposed to SDPP. Differences (P < 0.05) in pulsatile GH secretion were also detected. Hepatic IGF-I and GHR 1A mRNA were positively correlated with circulating IGF-I concentrations, and although both increased with time, they were not affected by photoperiod treatment. These results confirm that LDPP increases circulating concentrations of IGF-I, but this occurs independently of changes in IGF-I synthesis and GHR 1A mRNA expression in the liver. Therefore, our hypothesis that LDPP increases the expression of GHR 1A mRNA in the bovine liver is rejected.     

Effects of zeranol implants on post-castration response in calves

SUMMARY Suckling and yearling calves were surgically castrated and one half of each group implanted with 36 mg zeranol at time of castration. Both treated and control cattle of each class were maintained as a group and evaluated for swelling of the scrotum, inflammation and healing, plasma prostaglandin levels and weight gain. Swelling and inflammation of the scrotum were less in treated suckling calves than in controls at both 7 and 14 d after castration, though this difference was not statistically significant. In yearlings at 7 d after castration, treated cattle had more swelling than controls; however at 14 d, treated cattle had less swelling and inflammation with only one treated yearling having an open scrotal wound versus 6 (P <.03) in the control group. Plasma prostaglandin levels as indicated by plasma malondialdehyde increased from d 0 to 14; however no significant treatment differences were observed for either age group. Suckling calves treated with zeranol gained 9.79 kg more (P <.03) than non-treated calves during the 97 d of trial while the yearlings treated with zeranol gained 16.78 kg more (P <.01) than controls during 102 d. It is concluded from the increased growth and reduced scrotal swelling and inflammation in treated cattle that zeranol implantation could possibly have a beneficial effect in improving the healing process after castration.     

Growth response of steer calves treated with zeranol, oestradiol 17β or progesterone-oestradiol benzoate implants before and after weaning

This experiment compared the growth response of untreated steer calves with those given a long acting oestradiol-silicone rubber implant or implants of zeranol or oestradiol-progesterone pellets either singly, or repeated after 79 days. The experiment extended through the 6 weeks prior to weaning at 8 months of age, 5 weeks of grazing oat stubble and a 16-week finishing phase on a feedlot. The oestradiol-silicone rubber implant was the only product to significantly increase weight gains compared to controls (0.69 vs 0.52 kg/head/day, 18.2% advantage) in the pre-weaning phase. All anabolic agents produced higher weight gains ranging from increases of 0.16 to 0.19 kg/head/day (18.2-21.6%) above controls in the first 60 days of the feedlot phase. Responses did not differ significantly among the products and were the same whether or not steers had been previously implanted. Lower planes of nutrition in the late suckling and post-weaning periods were accompanied by smaller and non-significant responses to both the short acting anabolics, zeranol and oestrogen-progesterone, compared to the increased weight gains of steers given oestradiol-silicone rubber implants. Implanting with oestradiol in a silicone rubber matrix resulted in similar increases in weight gain both before and during the feedlot phase. This may have been due to the implant maintaining a continuously high level of circulating anabolic agent for the 190 days of the experiment.     

Preparing Holstein steer calves for the feedlot.

It is increasingly common to raise Holstein steer calves for entry to feedlot production systems rather than more traditional milk-fed veal production systems. Providing adequate nutritional support for the maintenance and growth of Holstein calves is essential in preparing them for a commercial feedlot environment. In this article, the dietary requirements of preruminant calves are reviewed and examples of evaluating milk diets for Holstein calves are detailed. The importance of the transition between milk feeding and grain-forage diets is discussed. Aspects of disease prevention, such as coccidiosis control and colostrum feeding, are also discussed. The reader will gain practical tools to use in preventive medicine programs involving Holstein steers being prepared for commercial feedlots.     

The effect of a preassembly zeranol implant and post-transit diet on the health performance and metabolic profile of feeder calves

A total 262 Angus steer calves averaging 207 kg from none (trial 1) and five farms (trial 2) were identified on the farm of origin and one-half of the calves on each farm was implanted with 36 mg of zeranol before entering the feeder calf assembly and marketing system. Calves were assembled, fasted for 24 h and fed hay for 72 h, then shipped 1,368 km. Upon arrival, the following receiving diets were fed for 4 wk to one-third of the calves from each farm and implant group: 1) control diet, 2) high-potassium diet, 3) escape-protein diet using corn gluten meal, which can escape ruminal degradation as a protein source. Implanted calves gained more weight (P less than .10) than nonimplanted calves while on the farm, but changes in weight during assembly, transit and the 28-d receiving period were not different (P more than .10). Plasma glucose and total protein concentrations were higher (P less than .05), while urea nitrogen concentration was lower (P less than .05) for implanted calves following transit. Increasing the potassium concentration of the receiving diet increased (P less than .05) post-transit weight gains, but had no affect on dry matter consumption. Corn gluten meal replaced soybean meal in the escape-protein diet and resulted in similar weight gains. Plasma urea nitrogen concentrations were higher (P less than .05) at 2 wk post-transit in the escape-protein diet group as compared with the control group. Receiving diet had no effect on the incidence or severity of bovine respiratory disease, but affected (P less than .05) performance during the subsequent 69-d stocker phase of ad libitum access to medium quality hay and 2.27 kg of supplement per day.     

Toxocara vitulorum in suckling calves in The Netherlands

A Dutch farmer with beef cattle and suckling calves noticed one of the calves suffering from diarrhoea and observed large white worms near the perineum. In the faeces of this calf, eggs of Toxocara vitulorum were found. The majority of the cows in the herd were of the Piemontese breed previously imported from southern France. Treatment with albendazole was successful. Two other calves had positive faecal egg counts. One month after treatment of these calves with doramectin, no eggs were found. To prevent further infections on the farm and dissemination of this uncommon infection to other farms, the farmer decided to have all his cattle slaughtered.     

Studies on immunisation of suckling calves with dictol

The immunisation of young milk-fed calves with two doses of the commercially available Dictyocaulus viviparus irradiated larval vaccine, Dictol, was studied. In the first experiment, vaccination of groups of pail-milk-fed calves at 3 and 7 weeks of age resulted in 96.7% reduction of lungworm burdens upon challenge when compared with non-vaccinated controls. Contemporaneous vaccination of calves aged 8 and 12 weeks resulted in a reduction in lungworm burden of 98.9% compared with controls of the same age. The clinical reaction upon challenge of both age groups was minimal compared with their respective controls.In the second experiment a group of six suckling calves were vaccinated with Dictol at 3 and 7 weeks of age and then challenged with infective larvae of D. viviparus together with non-vaccinated controls. At subsequent post-mortem examination the mean lungworm burdens of the vaccinates was 87% less than that of the controls. Some clinical reaction evidence by increased respiratory rates and bodyweight loss occurred in the vaccinates but this was not as severe as in the controls. At necropsy a concurrent pneumonia due to Mycoplasma spp. was present and it is suggested that this contributed to the poorer protection obtained compared with the pail-milk-fed calves of the fist experiment.In the third experiment a group of suckling calves were again vaccinated at 3 and 7 weeks of age and then exposed to a natural challenge together with parasite-naive controls. Although the level of challenge was relatively low, immunisation was apparently high successful as lungworms were completely absent in the vaccinates when examined at necropsy.In all three experiments numerous pulmonary lymphoid nodules, which are a useful guide to the immune status of calves, were present in the vaccinates and absent or scarce in the controls. It is concluded that the cumulative evidence from the three experiments suggest that immunisation against infections of D. viviparus of young milk-fed calves in the field may be a practical proposition.     

Effect of diseases on the nutrient intake by suckling calves

An energy and protein intake test was applied to 341 female nursed calves under production conditions. Their daily intakes of skim milk enriched with milk substitute, fodder concentrates, and hay were recorded and their daily energy and protein intakes calculated. Their feed consumption was characterised by cumulative nutrient intake curves, depending on the time of foremilk feeding (K-I-period). Energy and protein intake figures were related to the findings obtained from daily health control, with the view to defining the effects of pneumonia or diarrhoea on feed intake. Both diseases were found to cause significant reduction in nutrient intake, depending on the given type of disease and severity, with their negative impact having been most markedly shown in the context of dry feed intake. The delay caused to the development of dry feed consumption by diseases of the respiratory and digestive tracts was many times longer than the time of the clinical course. The above observations provided some cues for conclusions regarding the approach to be taken by the veterinarian to diagnosis, therapy, and rehabilitation of affected calves. Certain concepts were derived from the findings as to how to feed calves to forestall developmental disorders.     

Coccidiosis in suckling calves raised on large farms

In a large herd of pigs whose piglets suffered from diarrheas coprological examination revealed the great incidence of Isospora suis coccidia in piglets. The first oocysts were found out in seven-day piglets; the highest incidence was observed in twelve-day piglets (65.9%); the time of oocyst elimination (patency) was five to six days. The oocysts appeared in the excrements of piglets two to three days after the diarrhea onset. Individual examinations of piglets demonstrated the correlation between the intensity of clinical signs and the numbers of eliminated oocysts. No oocysts of I. suis were found either in sow excrements or gilt excrements. The I. suis oocysts were diagnosed in the excrements of piglets from first-farrowing sows and in the excrements of piglets from the sows, in the litters of which I. suis had already been demonstrated. Evaluating the therapeutic and preventive effects of the anticoccidic drug amprolium no significant difference was recorded in the I. suis incidence between the medicated group and the control group.     

The effect of unrestricted milk feeding on the growth and health of Jersey calves

This study was conducted to determine the effect of feeding high milk volumes on the growth rate, health and cross-sucking behaviour in group-fed Jersey calves. Three-day-old heifers (n = 120) in a seasonal calving dairy herd were randomly assigned to one of 6 treatment groups. Three groups received high milk volumes (HMV), consisting of ad libitum milk or milk replacer feeding twice a day, while 3 groups received restricted milk volumes (RMV), consisting of 2 l twice daily, during the pre-weaning period. After a pre-weaning period during which feeding was reduced to once daily, all calves were weaned at 42 days and monitored until 60 days of age. Adjusting for birth mass, birth date, dam parity and sire, average daily mass gain (ADG), both pre-weaning (days 0-42) and overall (days 0-60), was higher in HMV than in RMV calves (P < 0.001). After weaning, growth rates showed no differences and at 60 days of age the HMV calves maintained a 6.74 kg advantage in mean body mass (P < 0.001). The mean intake of dry starter feed was higher in RMV than in HMV calves. Overall feed conversion rate of HMV calves was 9.6 % better than RMV calves. However, the variable cost per kg mass gain was 12 % higher for HMV calves. In the RMV groups 75 % of calves showed cross-sucking behaviour pre-weaning and 18 % post-weaning, whereas in HMV calves the proportions were 2 % and 7 %, respectively. There was no significant effect of milk volume on the incidence of diarrhoea. We conclude that the feeding of high volumes of milk to Jersey calves has a positive effect on growth rate, without compromising health or reducing solid feed intake after weaning. However, the higher cost of such a feeding system may limit its implementation.     

The effect of milk intake on forage intake and growth of nursing calves

Thirty-nine Holstein steer calves were assigned to one of five treatments at birth and individually fed for 200 d with milk replacer reconstituted to equal the fat and protein concentration of beef cow milk. Treatment levels were the quantities of reconstituted milk fed per day based on lactation curves, which were based on peak milk levels (PML) of 2.72, 5.44, 8.16, 10.88, and 13.6 kg/d, respectively. In addition to reconstituted milk, chopped alfalfa hay was offered ad libitum to allow for maximal voluntary forage consumption. All calves were fed a high-energy diet postweaning until they reached a similar degree of fatness in the 12th rib (4 to 5% chemical fat) as determined by ultrasound. There were differences (P < 0.05) among groups in weaning weight, preweaning ADG, age, and weight at slaughter. During the preweaning phase, there was a linear relationship (P < 0.01) for daily milk and forage DE intake; however, DE intake per unit of BW did not differ across treatments (P = 0.06). Increasing PML resulted in a linear (P < 0.01) decrease in alfalfa hay intake in the preweaning phase, and G:F increased quadratically (P < 0.01). During the postweaning phase, preweaning milk intake had no meaningful effect on postweaning ADG, but overall ADG had a linear relationship (P < 0.01) with preweaning milk level. There was no effect of PML on the 12th-rib lipid percent, marbling score, or quality grade, but protein and fat concentration in the carcass and empty BW increased linearly (P < 0.01) with PML. The group fed at 2.72 kg/d PML was 58 kg lighter (P = 0.03) and required 34 d more (P < 0.01) to reach the predetermined degree of fatness at slaughter than the group fed at 13.6 kg/d PML, suggesting that increased milk production by the dam can decrease the number of days to the slaughter weight at which a similar rib lipid concentration is reached.     

The effect of zeranol on muscle structure and the development of the testes in bulls

The effect was investigated of the Ralgro preparation with the active substance zeranol on histological and histochemical properties of bull muscles. The anabolic effect was displayed by a trend toward greater thickness of muscle fibres in m. longissimus thoracis, m. semitendinosus and m. triceps brachii, whilst differences between the muscles of experimental and control animals were not statistically significant. The bulls administered zeranol had the higher proportions as well as the higher relative volumes of white (aW) muscle fibres, but neither were these differences statistically significant in comparison with the control. The growth and development of testicles are inhibited by zeranol. The inhibition is significant and persists during 30 days after the last administration. Later on, the rate of development and growth are increased with the testicles reaching the weight of the sexual glands of control animals in 90 days after the last administration; the coiled seminiferous tubules grow and spermiogenesis occurs.     

The effect of zeranol on live weight gain, feed intake and carcass composition of steers during compensatory growth

To evaluate the effect of zeranol implants in steers on compensatory ++growth, 80 steer calves (9 mo of age; 200 kg) were fed at two feeding levels (RO = 9.2 MJ ME/kg DM; R1 = 6.9 MJ ME/kg DM) for 119 d (Period 1). During Period 2, steers were full-fed to 400 kg BW with (Z1) or without (ZO) zeranol implants. Ten steers were slaughtered at the end of Period 1 to estimate carcass composition. Differences of 100 kg in BW were achieved by restriction in Period 1. Subsequent to restriction, cumulative ADG remained greater (P less than .05) up to the 24th wk of recuperation and implants increased (P less than .001) BW gain by 31% and 24% for RO and R1, respectively. The average daily energy intake (ME/W(.75) in Period 2 was similar for all treatments. Feed conversion was improved by 21.5% (P less than .05) by implants. At the end of Period 2 the R1ZO had 8.6 kg less muscle (P less than .001), 2.9 kg less bone (P less than .001) and 5.9 kg more fat (P less than .05) than the ROZO. In comparison, the carcasses of the implanted animals did not show significant differences (P greater than .05) due to restriction. Carcass daily gains were increased by previous restriction (P less than .01) and implants (P less than .05). Zeranol increased daily live weight gain and feed conversion in animals in continuous growth as well as in those observed in compensatory growth an tended to eliminate a tendency for higher content of fat in carcasses of nonimplanted animals making compensatory growth.     

The period between birth and first suckling in dairy calves.

The period between birth and first suckling was recorded for 82 dairy calves. 11 per cent of heifers' calves and 46 per cent of cows' calves had not suckled by 6 h after birth. All calves, whether suckling spontaneously or put to the teat at 6 hr, had adequate 48 h total serum immunoglobulin levels.