In order to determine the quantity of methane (CH4) produced by lactating beef cows on pasture, 16 Hereford–Simmental first-calf heifers with a mean weight of 511.2 ± 5.8 kg were randomly selected from a larger group of cows (n = 60) on a grazing management experiment and used to evaluate the effects of pasture type on ruminal CH4 production using the sulfur hexafluoride (SF6) tracer-gas technique. Pasture treatments consisted of two pasture types, alfalfa-grass [78% alfalfa (Medicago sativa L.) – 22% meadow bromegrass (Bromus biebersteinii Roem and Schult.)] or 100% meadow bromegrass at each of two fertility levels (either unfertilized or soil test recommended fertilizer levels) with two replications of each pasture treatment (8 pastures). Cows were managed using a "put and take" stocking system to leave equal residual herbage mass on all treatments following the grazing period in each paddock. During the 69-d grazing season, two cows from each pasture were sampled to determine daily forage intake and CH...

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Impact of pasture type on methane production by lactating beef cows

Data on 185 Angus cows were used to study the effect of divergent selection for residual feed intake on maternal productivity across 3 mating seasons, starting from 2000. The cows were the result of 1 to 2.5 generations of selection (mean of 1.5), and differed in estimated breeding value for residual feed intake by 0.8 kg/day. In general, cows lost subcutaneous fat (measured 2 times a year) during the period when they were nursing calves, and gained fat thereafter. No significant selection line differences in fatness were observed except for those measured at the start of the 2000 (10.8 ± 0.4 v. 9.3 ± 0.4 mm), 2001 (11.3 ± 0.4 v. 9.8 ± 0.4 mm) and 2002 (7.0 ± 0.5 v. 5.7 ± 0.5 mm) mating seasons, where high residual feed intake cows had significantly (P<0.05) higher rib fat depths. No significant selection line differences in weight (measured 4 times a year) were observed. However, the cows either maintained or lost weight during the calf nursing period, and gained weight thereafter, with mean weights ranging from 450 to 658 kg. There were no significant selection line differences in pregnancy (mean 90.4%), calving (mean 88.7%) and weaning (mean of 80.8%) rates, milk yield (mean 7.7 kg/day) and weight of calf weaned per cow exposed to bull (mean 195 kg). The study indicates that after 1.5 generations of divergent selection for residual feed intake there are no significant selection line differences for maternal productivity traits.

Maternal productivity of Angus cows divergently selected for post-weaning residual feed intake

In order to determine the quantity of methane (CH4) produced by steers on pasture, 16 steers with a mean weight of 356 ± 25 kg were randomly selected from a larger group of cattle (n = 48) to evaluate the effects of grazing management and monensin controlled release capsule (CRC) administration on ruminal CH4 production using the sulphur hexafluoride (SF6) tracer-gas technique. Pasture management treatments consisted of two grazing systems (continuous stocking or 10-paddock rotational stocking) at each of two stocking rates (low, 1.1 steer ha−1 or high, 2.2 steers ha−1) with two replications of each pasture treatment. Half of the animals on each pasture treatment were administered a monensin CRC delivering 270 mg d−1, and untreated animals served as controls. During the 140-d grazing season, one steer from each treatment-replicate combination was sampled to determine daily intake and CH4 production on four occasions. The chemical composition of diets differed between grazing management treatments and samp...

Methane production by steers on pasture

Genetic improvement of beef cattle in New Zealand: breeding objectives

II Dedication This work is dedicated to my parents; my father Ato Awgichew Ayalew and my mother Woizero Elfinesh Kidanemariam and to my wife Woizero Etabezahu Eshetu and our children Henok, Mahlet and Bezaye. ACKNOWLEDGEMENTS III ACKNOWLEDGEMENTS I would like to express my deepest respect and most sincere gratitude to my supervisor, Prof. International Livestock Centre for Africa, for providing me the experimental animals and for allowing me to use its computer, library and laboratory facilities. My most sincere thanks and appreciation are also due to the staff of ILRI's experiment station at Debre Birhan for managing the experimental flock and for their tireless assistance in the data collection process. My heart felt thanks also go to the staff of the animal nutrition laboratory of ILRI in Addis Ababa for their kind assistance in analytical work. My deep gratitude also goes to Dr. Ed Rege for his guidance and assistance as co-supervisor and for allowing his staff to help in the data collection and compilation. My thanks and appreciation also go to the German Academic Exchange Service (DAAD) for giving me the scholarship which enabled me to undertake this study. The financial support I received from Humboldt University of Berlin at the latter part of my study is also highly appreciated. I am very grateful to Dr. Ursula Grawert of the International Students Office of Humboldt University for her kind consideration and support. I am also deeply indebted to Dr. Ulrike Funke and Mr. Christian Funke for their constant encouragement and support throughout. Without their unreserved support completion of this work would not have been possible. The support and encouragement I received from Dr. C. Kijora is highly appreciated. I would like to express my gratitude to Dr. Birgit Zumbach not only for her constant encouragement but also for reading and editing the manuscript, for her help in translating the summary to German and in the preparation of the transparencies required for the defence. My sincere thanks also go to Mrs. Friedlieb and Mr. Seekamp of the Faculty's computer centre in Dahlem for their help in data management. ACKNOWLEDGEMENTS IV I am also indebted to express my gratitude to Mrs and the other staff members of the department of Animal Breeding in the Tropics and sub-Tropics who have helped me in many ways throughout. I thank Mr. Solomon Melaku for reading and editing the manuscript. I also wish to thank …

Comparative performance evaluation of Horro and Menz sheep of Ethiopia under grazing and intensive feeding conditions

Faecal output of 287 beef cows consisting of Hereford (H × H), Simmental × Hereford (S × H), Friesian × Hereford (F × H) and Brahman × Hereford (B × H) breeding was estimated using controlled release of chromic oxide (Cr2O3). All cows were from 6 to 10 years of age and had grazed on one of three pasture systems in the subtropics of New South Wales since they were 7–8 months of age. These pastures were designated as being of high, medium and low nutritive value. Faecal organic matter output (FOMO) was estimated in each of four periods (early lactation, mid lactation, late lactation, and non-lactating) during one annual production cycle.Herbage mass exceeded 2 t/ha on all pasture systems, but estimates of organic-matter digestibility, nitrogen content and pasture composition indicated large differences in pasture quality (high > medium > low). Live weight of cows averaged 604, 488 and 393 kg live weight on the high, medium and low pastures, respectively. There were significant differences in live weight between genotypes on the medium (B × H > F × H and H × H) and low (S × H ≡ F × H ≡ B × H > H × H) pastures but not on the high pasture).FOMO and dry-matter intake (DMI) differed significantly between genotypes among lactating cows on all pasture systems. Rankings on high pastures were reasonably consistent in all periods: S × H ≡ F × H ≥ B × H ≥ H × H, as were those on low pastures, B × H ≥ S × H ≡ F × H ≥ H × H. Differences on medium pastures were significant only during mid-lactation when B × H ≡ S × H ≡ F × H > H × H. Significant differences between genotypes were observed among non-lactating cows on high pastures only, where H × H ≡ S × H ≡ F × H > B × H. Lactating females had significantly higher FOMO and DMI than non-lactating females when compared across genotypes during early lactation on all pastures.

Dry-matter intake of Hereford and first-cross cows measured by controlled release of chromic oxide on three pasture systems

Milk yield was determined by the weigh-suckle-weigh method over 2 years (1983 and 1984 calvings), for a total of 305 purebred Hereford (H x H) and first-cross Brahman x Hereford (B x H), Simmental x Hereford (S x H) and Friesian x Hereford (F x H) cows grazing three pasture systems at Grafton, New South Wales, Australia. The age of the cows ranged from 6 to 11 years. The data were used to evaluate different estimates of milk yield and to examine the effects of milk yield on growth of calves up to weaning. Of all the cow traits studied, average lactation milk yield (average of early, mid and late-lactation milk yields) had the highest correlation coefficient with calf 210-day weight (r = 0.73) and preweaning average daily gain (ADGtotal, r = 0.73), and explained > 50 % of the variation in the calf traits. However, milk yield was also moderately correlated with other cow traits (liveweight and body condition score). Thus, to predict calf performance, milk yield data may not be required if detailed data on other cow traits are available. This is supported by the finding that differences in the coefficients of determination (R 2 ) between models for calf 210-day weight and ADGtotal which included average lactation milk yield and other cow traits (highest R 2 = 69%) and models which included other cow traits but no milk yield estimate (highest R 2 = 57 %) were < 13 %. Cow breed rankings for average lactation milk yield were similar to those for calf 210-day weight and ADGtotal. On high quality pasture, S x H and F x H cows produced the most milk (S x H, 7.5 kg/day; F x H, 8.3 kg/day; B x H, 5.7 kg/day; H x H, 5.5 kg/day) and weaned the heaviest calves (S x H, 255 kg; F x H, 252 kg; B x H, 215 kg; H x H, 217 kg), while on low quality pasture, B x H and F x H cows produced the most milk (B x H, 4.2 kg/day; F x H, 3.7 kg/day; S x H, 2.9 kg/day; H x H, 2.7 kg/day) but B x H cows weaned the heaviest calves (B x H, 180 kg; F x H, 168 kg; S x H, 159 kg; H x H, 124 kg).

Evaluation of Hereford and first-cross cows on three pasture systems. III. Milk yield and its influence on calf performance

Preweaning growth of calves is influenced primarily by milk yield but also by other genetic and environmental factors. Is milk yield influenced by genotype by environment (GxE) interactions? At Grafton N.S.W., Hereford (HxH), Brahman x Hereford (BxH), Friesian x Hereford (FxH) and Simmental x Hereford (SxH) cows have been evaluated for productivity over their lifetime whilst grazing high, medium or low quality pastures (Hearnshaw 1993). The objective of this study was to determine milk yield from these mature cows and to examine its effect on growth of calves to weaning. Estimates of milk yield were determined for 305 cow/calf pairs using a weigh-suckle-weigh technique. Each pair had milk yields measured at 3 stages of lactation when calves averaged 49, 150 and 240 days of age. Milk yield was measured at noon and in the evening both estimates following a 6 hour cow/calf separation. The sum of the differences in calf liveweight before and after suckling at both noon and evening was used as the estimate of the cow’s 12 hour milk yield. Traits studied were 12 hour milk yield at early, mid and late lactation; the sum of these 3 milk yields (milk yield index); cow liveweight and body condition (CS), and calf liveweight and growth to weaning. Data were analysed using the GLM procedure of SAS (1990) and models included fixed effects of cow breed, pasture quality, calf sex and sire breed, year of estimation and all interactions. Since ‘time by breed by pasture’ was not significant in repeated measures analyses for milk yield, only ‘milk yield index’ results are presented. Simple and partial (adjusted for significant fixed effects) correlations among milk yield index and other maternal and calf traits were computed using data pooled across breed and pasture. Milk yield index was greatest on high quality pastures and least for low quality pastures. However rankings of genotypes varied between pasture systems indicating that miIk yield was affected by GxE (Table 1). Rankings changed from FxH=SxH>BxH=HxH (high quality pastures) to BxH>SxH=HxH with FxH intermediate between BxH and SxH (low quality pastures). Weaning weight and growth of calves followed similar trends for both this and a larger set of data (Heamshaw et al. 1994). Milk yield index was positively correlated with both calf weaning weight and growth (partial r = 0.5 1 and 0.52 respectively). Estimates were similar to other studies (eg Reynolds et al. 1978). Correlations with CS or CS change were negative, indicating cows with lower CS or greater change in CS had higher milk yield. Thus management or breeding strategies which increase milk yield within a particular environment will increase calf weights at weaning and overall productivity.

http://www.livestocklibrary.com.au/bitstream/handle/1234/8682/Hearnshaw96.PDF?sequence=1

P. J. Williamson

Papers

Dry-matter intake of Hereford and first-cross cows measured by controlled release of chromic oxide on three pasture systems

Evaluation of Hereford and first-cross cows on three pasture systems. III. Milk yield and its influence on calf performance

Effect of genotype and pasture quality on milk yield in beef cattle