Weight Of Bulls Research Articles

Parameters for the estimation of live weight and for the visual appraisal of the muscular conformation in the (double-muscled) Belgian Blue beef breed

Abstract. In the double-muscled Belgian Blue beef breed, withers height and hearth girth are routinely measured. This is mainly done to prevent a decrease in growth potential when selecting for increased muscular conformation. The muscular conformation itself is subjectively scored. It was questioned if additional body measurements may improve the accuracy of estimating live weight and whether some of these body measurements may yield information for evaluating the muscular conformation hence the slaughter value of a live animal. It was found that hearth girth and shoulder width have a high correlation with the live weight of slaughter bulls. The width of the hind quarters and withers height are good estimators as well. Models combining these different traits to estimate live weight have reliability up to 83%. Shoulder width and width of the hind quarters are a good reflection of the value of the slaughter bull, which is expressed as Euro per kg cold carcass weight. The withers height is negatively correlated (r = −0.40) with the muscular conformation of the slaughter bulls. Hearth girth has no clear relation with the muscular conformation. The four body traits, withers height, hearth girth, shoulder width and width of hind quarters are interesting traits related to economical traits in the double-muscled Belgian Blue beef breed. Using these body measurements in selection might be worthwhile to consider.

Konstruktion von Indizes mit Restriktionen in Random Regression Modellen zur Veränderung der Wachstumskurve

Abstract. Title of the paper: Index construction with restrictions in random regression models to change the pattern of the growth curve Random regression models provide estimated breeding values (EBV) for the complete growth curve for any target age. The animal-specific curves can be described as the weighted sum of continuous covariates with random regression coefficients. By using the covariance matrix K of the additive genetic regression coefficients the response to index selection can be calculated for any age or time of the test period. In this study selection indexes with equality restrictions based on the eigenvectors of matrix K were used to modify the growth curve of the population. In order to demonstrate the index construction a matrix K was used, estimated from repeated measurements for body weight of bulls by using Legendre polynomials as covariates. Indexes for high and low growth rate until age at the reflection point were derived subject to the restriction of zero gain for initial and final body weight. Selection strategies for improving body weight at the end of the test period while holding the daily gain in a certain time interval on a desired level were compared. By using so-called "restrictive economic values", an aggregate breeding value for body weight was derived from EBV for individual growth curve.

Pembentukan Rumus Sederhana Pendugaan Bobot Hidup Sapi Persilangan Simental dengan PO Berdasarkan Ukuran Tubuh

The objective of the research was to find out the simple model of regression equation for estimation of body weight (y in kg) based on the data of other body parameters of Simmental and Ongole Cross cattle's. Sixty two bulls and thirty six cow kept by farmer in Padang Panjang, West Sumatra were measured their body of body length (x1 in cm), thorax circle (x2 in cm), shoulder high (x3 in cm). Criteria for choosing the best equation are R2, R2 Adjusted, Mean square Error (MSE). Thirty equation was considered for choosing the best equation. The best equation for predicting of body weight of bulls were y = 0,018(x2 -18)'2 and y = 0,000124(x1'2 * x2), while .for cows: y = 0,0156(x2 - 6)'2 and y = 0,000118(x1'2 * x2).

Seleção para peso pós-desmama em um rebanho Gir. 1. Resposta direta e correlacionada em 21 anos de seleção

A seleção para peso pós-desmama tem sido aplicada em um rebanho Gir (80 vacas, seis touros) desde 1976, e um rebanho Nelore Controle, NeC (60 vacas, quatro touros), tem sido mantido para avaliação da mudança ambiental. O critério de seleção dos machos foi o peso aos 378 dias (P378), obtido em prova de ganho de peso, e o das fêmeas, o peso aos 550 dias (P550) em recria a pasto. A média dos diferenciais de seleção efetivos dos pais foi, respectivamente, 19,5 e 1,8 kg para Gir e NeC, correspondendo a 0,72 e 0,07 unidades de desvio-padrão (u.d.p.). A média dos diferenciais de seleção efetivos acumulados dos pais, na progênie de 2001, foi 83,7 e 7,2 kg para Gir e NeC, correspondendo a 3,17 e 0,29 u.d.p. O intervalo de geração médio no rebanho Gir foi 5,65 anos e no NeC 5,0 anos e o coeficiente de geração médio individual na progênie de 2001 atingiu 4,25 (Gir) e 4,65 (NeC) gerações de seleção. As estimativas de tendência genética no rebanho Gir, obtidas por quadrados mínimos, foram PN = 0,16; P210 = 0,81 kg/ano; GPRE = 3,02 g/dia/ano; P378 = 2,88; P550 = 2,80 kg/ano; G112 = 11,2 g/dia/ano, AM = 0,003 e AF = 0,004 m/ano. Com base no modelo misto, as estimativas para essas características foram menores (0,03 e 0,28 kg/ano; 1,15 g/dia/ano; 1,45 e 1,07 kg/ano; 3,73 g/dia/ano; 0,003 e 0,002 m/ano). As estimativas de herdabilidade realizadas para P378 e P550 foram 0,69 e 0,64, respectivamente. Os resultados indicaram que a seleção para peso pós-desmama, com base na informação de desempenho individual, promoveu respostas genéticas significativas tanto nas características sob seleção direta quanto nas respostas correlacionadas em características de crescimento da fase pré e pós-desmama no rebanho Gir.

Genetic parameters for carcass traits and their live animal indicators in Simmental cattle.

The objective of this study was to estimate parameters required for genetic evaluation of Simmental carcass merit using carcass and live animal data. Carcass weight, fat thickness, longissimus muscle area, and marbling score were available from 5,750 steers and 1,504 heifers sired by Simmental bulls. Additionally, yearling ultrasound measurements of fat thickness, longissimus muscle area, and estimated percentage of intramuscular fat were available on Simmental bulls (n = 3,409) and heifers (n = 1,503). An extended pedigree was used to construct the relationship matrix (n = 23,968) linking bulls and heifers with ultrasound data to steers and heifers with carcass data. All data were obtained from the American Simmental Association. No animal had both ultrasound and carcass data. Using an animal model and treating corresponding ultrasound and carcass traits separately, genetic parameters were estimated using restricted maximum likelihood. Heritability estimates for carcass traits were 0.48 +/- 0.06, 0.35 +/- 0.05, 0.46 +/- 0.05, and 0.54 +/- 0.05 for carcass weight, fat thickness, longissimus muscle area, and marbling score, respectively. Heritability estimates for bull (heifer) ultrasound traits were 0.53 +/- 0.07 (0.69 +/- 0.09), 0.37 +/- 0.06 (0.51 +/- 0.09), and 0.47 +/- 0.06 (0.52 +/- 0.09) for fat thickness, longissimus muscle area, and intramuscular fat percentage, respectively. Heritability of weight at scan was 0.47 +/- 0.05. Using a bivariate weight model including scan weight of bulls and heifers with carcass weight of slaughter animals, a genetic correlation of 0.77 +/- 0.10 was obtained. Models for fat thickness, longissimus muscle area, and marbling score were each trivariate, including ultrasound measurements on yearling bulls and heifers, and corresponding carcass traits of slaughter animals. Genetic correlations of carcass fat thickness with bull and heifer ultrasound fat were 0.79 +/- 0.13 and 0.83 +/- 0.12, respectively. Genetic correlations of carcass longissimus muscle area with bull and heifer ultrasound longissimus muscle area were 0.80 +/- 0.11 and 0.54 +/- 0.12, respectively. Genetic correlations of carcass marbling score with bull and heifer ultrasound intramuscular fat percentage were 0.74 +/- 0.11 and 0.69 +/- 0.13, respectively. These results provide the parameter estimates necessary for genetic evaluation of Simmental carcass merit using both data from steer and heifer carcasses, and their ultrasound indicators on yearling bulls and heifers.

Historical and practical aspects of profitability in commercial beef production systems

The numbers of beef animals in New Zealand have increased markedly since 1960. In particular the number of animals (especially bulls) reared within the dairy industry for beef production has grown. Early research into aspects of intensive pasture-based beef production systems concentrated on high levels of pasture utilisation and beef production per ha. Farmers have adapted these results and systems and the carcass weight (CW) of bulls slaughtered now at 15-18 months of age have increased and often are over 300 kg CW. It is shown simplistically that profit/ ha will also increase with increasing CW and increased efficiency in use of feed within 1yr bull beef systems. In practice however, utilising more of the pasture dry matter (DM) grown and maintaining pasture quality are important issues. Two year bull systems are shown to be just as profitable as the more technically efficient 1yr bull system. Where beef production is carried out in conjunction with sheep production, especially on hill country, some commonly used benchmarks of technical and economic efficiency may be misleading with regard to overall system profitability and the contribution of various classes of beef animals. Keywords: beef animals, bulls, economic efficiency, feed efficiency, profitability

Efeito do nível de concentrado sobre o peso dos órgãos internos e do conteúdo gastrintestinal de bovinos Nelore não-castrados

O efeito de cinco níveis de concentrado na dieta foi avaliado sobre o conteúdo do trato gastrintestinal e o peso dos órgãos internos e dos compartimentos gastrintestinais de bovinos Nelore não-castrados. Vinte e cinco animais com peso médio de 330 kg e idade média de 20 meses foram distribuídos, em delineamento inteiramente casualizado, em cinco tratamentos com diferentes níveis de concentrado na matéria seca das dietas (25,0; 37,5; 50,0; 62,5; e 75,0%). Os animais, quando atingiram o peso de abate pré-estabelecido de 450 kg, foram abatidos e os pesos dos órgãos e das vísceras, registrados. Foram ajustadas equações de regressão para verificar o efeito da inclusão de concentrado na dieta sobre os pesos de cada órgão e, ou, víscera. Os pesos, tanto absolutos, quanto relativos, do conteúdo do trato gastrintestinal diminuíram linearmente, enquanto os pesos do fígado, dos rins e do baço aumentaram linearmente, em função dos níveis de concentrado nas dietas. Os pesos do rúmen-retículo foram influenciados quadraticamente pelos níveis de concentrado, com valores mínimos estimados em 6,45 kg e 1,60 kg/100 kg de peso vazio, para os níveis de 51,72 e 55,51% de concentrado nas dietas, em relação aos pesos absoluto e relativo, respectivamente. A quantidade de gordura interna aumentou linearmente com a inclusão de concentrado nas dietas.

The Occurrence of Tail Tip Alterations in Fattening Bulls Kept Under Different Husbandry Conditions

AbstractPathological alterations of the tail tip are a severe problem for fattening cattle husbandry with respect to animal welfare and economic losses. We compared the frequencies of tail tip lesions and less severe skin damage in bulls on farms with slatted-floor pens (slat, n = 10), slatted floor pens with prophylactic tail docking (slat/dock, n = 9), and deep bedding pens (straw, n = 10). In addition, the subjects’ weight, their space allotment and the season of the year were determined to test whether they were related to the frequency of tail tip lesions and skin damage. Results are based on 8782 tail inspections in 764 pens. The frequency of the more severe tail tip lesions was highest in slat farms, less high in slat/dock farms, and lowest in straw farms. However, the incidence of the less severe skin damage was highest in slat farms, less high in straw farms, and lowest in slat/dock farms. The frequency of tail tip lesions increased with the weight of bulls in slat and slat/dock farms, but not in straw farms. In addition, in slat and slat/dock farms the incidence of tail tip lesions increased with a decreasing space allotment. The frequency of skin damage increased with increasing weight of bulls in each housing condition. The effect of weight on the number of tail tip lesions and skin damage was stronger in autumn, ie the period following the warm season, compared to spring. Our results suggest that a soft floor and an enlarged space allotment are the most suitable means of preventing tail tip lesions in fattening bulls. Prophylactic tail docking can reduce the occurrence of tail tip lesions only to a lesser degree and may impair the animals’ welfare.

Genetic parameters for ultrasound and carcass measures of yield and quality among replacement and slaughter beef cattle.

Real time ultrasound (RTU) measures of longissimus muscle area and fat depth were taken at 12 and 14 mo of age on composite bulls (n = 404) and heifers (n = 514). Carcass longissimus muscle area and fat depth, hot carcass weight, estimated percentage lean yield, marbling score, Warner-Bratzler shear force, and 7-rib dissectable seam fat and lean percentages were measured on steers (n = 235). Additive genetic variances for longissimus muscle area were 76 and 77% larger in bulls at 12 and 14 mo than the corresponding estimates for heifers. Heritability estimates for longissimus muscle area were 0.61 and 0.52 in bulls and 0.49 and 0.47 in heifers at 12 and 14 mo, respectively. The genetic correlations of longissimus muscle area of bulls vs heifers were 0.61 and 0.84 at 12 and 14 mo, respectively. Genetic correlations of longissimus muscle area measured in steer carcasses were 0.71 and 0.67 with the longissimus muscle areas in bulls and heifers at 12 mo and 0.73 and 0.79 at 14 mo. Heritability estimates for fat depth were 0.50 and 0.35 in bulls and 0.44 and 0.49 in heifers at 12 and 14 mo, respectively. The genetic correlation of fat depth in bulls vs heifers at 12 mo was 0.65 and was 0.49 at 14 mo. Genetic correlations of fat depth measured in bulls at 12 and 14 mo with fat depth measured in steers at slaughter were 0.23 and 0.21, and the corresponding correlations of between heifers and steers were 0.66 and 0.86, respectively. Live weights at 12 and 14 mo were genetically equivalent (r(g) = 0.98). Genetic correlations between live weights of bulls and heifers with hot carcass weight of the steers were also high (r(g) > 0.80). Longissimus muscle area measured using RTU was positively correlated with carcass measures of longissimus muscle area, estimated percentage lean yield, and percentage lean in a 7-rib section from steers. Measures of backfat obtained using RTU were positively correlated with fat depth and dissectable seam fat from the 7-rib section of steer carcasses. Genetic correlations between measures of backfat obtained using RTU and marbling were negative but low. These results indicate that longissimus muscle area and backfat may be under sufficiently different genetic control in bulls vs heifers to warrant being treated as separate traits in genetic evaluation models. Further, traits measured using RTU in potential replacement bulls and heifers at 12 and 14 mo of age may be considered different from the corresponding carcass traits of steers.

Einfluss der rationsgestaltung auf die faecale phosphorausscheidung bei unterschiedlich schweren mastbullen*

Je 5 kleinere (mittlere Lebendmasse: 227,9 ± 23,7 kg/Tier) und größere Jungmastbullen (435,2±14,3 kg/Tier) wurden sowohl mit einer rauhfutterreichen (gehäckseltes Weizenstroh:Konzentrat‐Verhältnis=l:l) als auch mit einer rauhfutterarmen Ration (Stroh:Konzentrat = 1:4) gefuttert. Beide Rationen waren phosphorarm (1,1 bzw. 1,2 g P/kg DM). Die Tiere standen in Bilanzkäfigen; nach einer 20tägigen Vorperiode folgte eine l0tägige Sammelperiode. Wahrend die Lebendmasse keinen signifikanten Einfluß auf die scheinbare Verdaulichkeit der Rationsbestandteile ausübte, lag die scheinbare Verdaulichkeit der organischen Substanz bei rauhfutterreicher Fütterung signifikant unter der nach rauh‐futterarmer Rationsgestaltung (66,8 bzw. 74,4 %). Rationsgestaltung und Lebendmasse hatten keinen signifikanten Einfluß auf die untersuchten Stoffwechselkriterien des Mineralstoffstatus. Die faecale P‐Ausscheidung betrug bei rauhfutterreicher bzw. ‐armer Rationsgestaltung 0,94 bzw. 1,08 g/kg DM, zwischen den Altersgruppen bestanden keine Unterschiede. Bezogen auf die aufgenommene verdauliche organische Substanz variierte die faecale P‐Ausscheidung zwischen 1,44 und 1,58 g je kg ver‐dauter Substanz. Für Kalkulationen zum Phosphorbedarf wachsender Rinder konnen als unvermeidbare faecale Exkretion 1,0 bzw. 1,5 g P je kg DMI bzw. DOMI unterstellt werden.

Testes function and feedlot performance of bulls actively immunized against gonadotropin-releasing hormone: effect of age at immunization.

Testes function, feedlot performance, and carcass traits were evaluated in bulls actively immunized against gonadotropin-releasing hormone (GnRH) at different ages. Bull calves were randomly assigned to one of seven treatment groups (n = 15 calves/group). Calves were unimmunized (Group 1), immunized at 1.5, 4, 7, or 12 mo of age with a GnRH-keyhole limpet hemocyanin (KLH) conjugate (Groups 2 to 5, respectively), or castrated at 4 mo of age (Groups 6 and 7). Immunized bulls did not receive a secondary, or booster, immunization. Calves in group 6 received Synovex-C at castration and Synovex-S at weaning and feedlot entry. Anti-GnRH titer was evident at slaughter in all immunized bulls. However, the final immune response of bulls immunized at 1.5 mo was significantly lower than the response of bulls immunized at later stages of development. Final scrotal circumference and testis weight in bulls immunized at 4, 7, or 12 mo of age were significantly reduced relative to unimmunized bulls. The final live weight, feedlot gain, and carcass weight of immunized and unimmunized bulls did not differ (P > .05) from the same parameters in steers implanted with Synovex. Longissimus muscle area, marbling score, and backfat thickness did not differ between immunized and unimmunized bulls. The sex class score of the carcasses of immunized bulls did not differ from the score of steer carcasses. In contrast, a significantly higher proportion of carcasses from unimmunized bulls graded as bullock carcasses. Taken together, these data indicate that a single immunization against GnRH at 4 to 12 mo of age results in significant attenuation of testicular growth in bulls. These data also demonstrate that immunization against GnRH reduces the masculinity of carcasses from bulls, but does not affect feedlot performance, longissimus muscle area, marbling score, or backfat thickness. These results suggest that single immunization with the GnRH-KLH conjugate may have practical utility as a noninvasive alternative to surgical castration in management of beef cattle.

Growth of F1Bos Taurus × Bos indicus versus Bos indicus beef cattle in Venezuela1. II. Initial, final, and carcass weight of bulls, and breeding weight of heifers

Growth of F₁<i>Bos Taurus × Bos indicus</i> versus <i>Bos indicus</i> beef cattle in Venezuela¹. II. Initial, final, and carcass weight of bulls, and breeding weight of heifers

Age-related changes in scrotal circumference, testis size and sperm reserves in bulls of the tropically adapted Senepol breed

Testicular characteristics were measured in a random population of Senepol bulls representing three farms on St. Croix (17°N, 64°W), during a 5 year period. Bulls were maintained on native, tropical grass/legume pasture throughout all stages of development. Scrotal circumference (SC; 317 measurements, 267 bulls) increased in a curvilinear relationship ( P < 0.001) with both age ( r 2 = 0.816) and body weight ( r 2 = 0.856) and reached a mean maximum SC of 42.4 cm at 6–7 years of age. There was a linear relationship ( n=84; P<0.001) between SC and total testicular weight ( r 2=0.883), testis length ( r 2=0.800) and testis width ( r 2=0.969). Testicular weights and dimensions were highly correlated ( P<0.001) with epididymal weights. Mean daily sperm production rate (14.1 × 10 9 spermatozoa g −1) did not differ between pubertal ( n=5), postpubertal ( n=5) and mature bulls ( n = 5); however, total daily sperm production and epididymal reserves increased ( P< 0.05) from 4.9 × 10 9 and 6.9 × 10 9 to 10.1 × 10 9 and 42.1 × 10 9 spermatozoa in pubertal and mature bulls, respectively. The data indicate that SC, testicular weight and sperm reserves of Senepol bulls more closely resemble those reported for Bos taurus than Bos indicus genotypes.

Niacin in dairy and beef cattle nutrition.

Niacin functions metabolically as a component of the coenzymes NAD and NADP. Sources of niacin are feedstuffs and the enzymatic conversion of tryptophan and quinolinic acid into niacin. Niacin is synthesized by the microflora in the rumen of ruminants. Recent research suggests that microbial production of niacin may not be sufficient for the requirements of high producing cows. Supplemental niacin given to cows in early lactation may reduce the rate of fat mobilization, decrease the concentration of ketones in blood and increase blood glucose level. Niacin supplementation may increase propionate concentration and decrease butyrate concentration in rumen liquor. Ruminal microbial protein synthesis was enhanced by niacin. Not all experiments showed such clear results. The positive metabolic effects of niacin supplementation have resulted in most studies in an improved milk yield (3-4%) especially during early lactation. The milk constituents were mostly uninfluenced or only minimally increased. Reasons for the high variations of results are differences in ration formulation, level of milk performance, stage of lactation, age of cows, body conditions, level and duration of niacin supplementation and specific experimental conditions. Niacin supplemented cows lost less body weight during early lactation, were less days open and required fewer pellets per pregnancy. It would appear that niacin supplementation of about 6 grams per animal per day (200-400 mg per kg dry matter) for the first 60 to 100 days of lactation may be beneficial in selected high producing cows or heifers. In beef cattle niacin supplementation would appear to be beneficial (approximately 1 g per animal per day or about 100 mg per kg dry matter) when the body weight of bulls is lower than 300 kg, when the diets are poor in protein (10 tp 12% crude protein of dry matter) and during dietary adaptation periods.

Tarsal lameness of dairy bulls housed at two artificial insemination centers: 24 cases (1975-1987)

Summary Degenerative joint disease of the tarsi was diagnosed in 20 of 24 Holstein bulls with tarsal lameness at 2 artificial insemination centers from 1975 to 1987. Each of the 2 centers housed about 100 bulls/yr. Of the 24 bulls with tarsal lameness, 22 were from the artificial insemination center designated as A, and 2 were from the center designated as B. Examination of the housing and management procedures revealed that center A had concrete floors with cuboi-dal-shaped yards, whereas center B had deep sand flooring, with long, narrow yards. The only other difference between the 2 centers was that center A used 1- and 2-year-old bulls as teasers for older, heavier bulls to mount, whereas center B used, bulls that were at least 6 years old to withstand the stress placed on their hind limbs by the weight of bulls undergoing semen collection. Radiographic lesions of tarsi of bulls from both centers ranged from distention of the tibiotarsal joint pouch to hypertrophic degenerative osteoarthritis of the distal, intertarsal, and tarsometatarsal joints. It was concluded that the concrete flooring and the semen collecting practices were responsible for the high prevalence of tarsal lameness and degenerative joint disease of the tarsi in bulls housed at center A.

Effects of transport stress and electrolyte supplementation on body fluids and weights of bulls

The effects of offering water (W) or an electrolyte solution (E) or neither (control; C) on the manifestation of transportation stress were examined in sixty-five 550-kg crossbred bulls. Following a 4-h (150-km) transport treatment serum electrolytes as well as live animal, carcass, and rumen content weights were monitored on all animals. In addition, intravenous injections of sodium thiocyanate and T-1824 dyes were used to examine extracellular (ECF) and plasma (PV) volumes in 10 (4 control, 3 water, and 3 electrolyte treatment) of the animals. The lowest carcass yield occurred in bulls denied access to both water and electrolytes during transport and the following (18 h) in lairage. Hot carcass yield (g kg−1 of final farm wt) for the C, E and W groups were 577.9 (57.8%) ± 3.8a, 597.5 (59.8%) ± 4.1b, and 589.4 (58.9%) ± 3.8b, respectively (P ≤ 0.05). The control (C) animals also had the lowest ECF volume (92.5, 127.9, and 142.3 liters for C, E and W, respectively). The effectiveness of water and electrolytes in reducing weight loss and improving carcass yield appeared to be explained to a large extent by the differential retention of fluid between the extra and intracellular body fluid compartments. Key words: Cattle, transport stress, electrolytes, fluid volumes

The effect of postweaning level of dietary energy on sex drive and semen quality of young beef bulls

Two postweaning feeding trials were conducted on 112 bull calves from a beef synthetic breed group to examine the effects of postweaning level of dietary energy and change in the level of energy on sex drive and semen quality of young bulls in 1988 and 1989. Within each year, the test period was 168 d, which was divided in two periods of 77 d and separated by a 14-d adjustment period. Within each year the bulls were randomly assigned to eight pens. The pen population was balanced with respect to age and weight of bulls. Bulls in four of the pens were fed a high concentrate diet while those in the remaining four pens were fed a low concentrate diet consisting of one half of the high diet plus hay ad libitum in the first period. After the adjustment period, the diets of four pens of bulls were reversed from high to low or from low to high resulting in high-high, high-low, low-high and low-low dietary treatments. The year was a significant (P<0.05) source of variation for all the components of libido score except for number of services achieved. The effect of energy on components of libido and libido score was not significant (P>0.05). Bulls on high-high had significantly larger scrotal circumference but exhibited poorer semen characteristics than their contemporaries on high-low, low-high and low-low diets. Even though feeding of high energy diet throughout the feedlot test period showed a positive effect on scrotal circumference, its effect on semen quality was negative. It was found that feeding a low energy diet in either half of the feedlot test period may prevent the detrimental effects of prolonged high energy feeding on semen characteristics of young beef bulls.

Nitrogen fertiliser use in early lambing systems

Nitrogen fertiliser was applied in June 1990 to early-August lambing systems and production was compared with traditional September lambing. Nitrogen (30 kg N/ha) increased pasture growth rates by 3-4 kg DM/ha/day and increased production by 210 kg DM/ha during July-September inclusive, Nitrogen responses were greatest in southfacing paddocks; least on easy contoured paddocks; and did not differ between "resident" pastures and "improved" pastures that had been oversown with new pasture cultivars 5 years before. Compared with traditional September lambing, early-August lambing (plus N) resulted in20% fewer lambs at weaning; 2.4 kg heavier lamb weaning weights; similar ewe weaning weights; and similar bull live weights in January. While N applications to earlier lambing systems reduced the differences in ewe and bull weights previously recorded between the lambing date treatments, it was not a profitable strategy. Assessment of pasture response to N (30 kg N/ha) was repeated in 1991. Nitrogen increased production by 260 kg DM/ha and responses were similar for all paddock and pasture types. Keywords nitrogen fertiliser, early lambing, hill country

Finishing lambs in hill country

A series of farmlet experiments investigated the effects of lambing dates, grazing methods and weaning/disposal dates on lamb production. Ewe and bull performance was also assessed. Laud contour did not significantly affect November-January lamb growth rates. Slight weight differences (-1 kg) in lambs and ewes occurred with changes in weaning date, but later disposal of lambs reduced both ewe and bull weights. Lamb growth rates were best when weaned lambs grazed in front of ewes and bulls in a quick rotation (25 days). Lambing in early August compared with early September, increased lamb weights but reduced lamb number, bull weight gains and ewe liveweights. At current product values earlier lambing reduced returns per ha. Recommendations are made for finishing lambs within mixed livestock systems in hill country. Keywords lamb, grazing management, hill country, agricultural systems, lambing date

Determination of minimum weaning scrotal circumference in Santa Gertrudis bulls fed a low energy ration

The scrotal circumference (SC) of 374 Santa Gertrudis bulls was measured prior to and following a period of low energy feed intake. A step by step regression was performed to formulate prediction equations in which the future SC of young bulls could be determined. These equations accounted for only 30 to 50% of the variation. Analysis of variance was used to determine the minimum SC at 7, 8 and 10 mo of age needed to obtain a 30-cm SC by 1 yr of age. At 7 mo, the bulls with the largest final SC, were those with an SC larger than 18 cm (P < 0.01). As the 8-mo SC increased so did the 13-mo SC (P < 0.01). As the 10-mo SC increased, the 15-mo SC also increased but bulls with less than a 21-cm SC were smaller (P < 0.01). Differences were also found between the 7 and 8-mo old weights of bulls and the initial SC (P < 0.01). As the initial testicle size increased, the 7, 8 and 10-mo ages and the 10-mo weight tended to increase. Few differences were found in initial SC measurements between the bulls that reached a 30-cm SC and those that did not at the end of one year regarding weight and age within each SC. These findings indicate that the SC at the beginning of a low energy feed period can be useful in determining the minimum SC outcome by the end of the test period.