ALBERT

Description: SummaryFaecal 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.

Description: SUMMARYTwenty-seven Hereford weaner steers (mean age 11 months, and live weight 142±17 kg) were used to study the effect of supplementation of an energy-rich grain (sorghum), and/or a protein meal on the live-weight change of cattle on a basal diet of low-quality grass hay over 48 days (Expt 1). The basal hay had an estimated energy value of 6·2 MJ metabolizable energy (ME)/kg dry matter (D.M.) and a nitrogen content of 6·2 g/kg D.M. Corresponding values for the sorghum supplement were 12·4 and 14·4, and for the protein meal 9·6 and 65. The daily rates of supplementation in Expt 1 were (g/head) 0 (nil), 600 (P1) or 1200 (P2) of protein meal pellets or 0 (nil), 560 (S1) or 1120 (S2) of sorghum and all combinations of P1 or P2 with S1 or S2. The carry-over effect of such supplementation on subsequent growth was recorded in Expt 2 when the steers grazed a kikuyu grass pasture for 100 days.In Expt 1, organic-matter intake of hay (HOMI) was increased (P 〈 0·01) by protein but decreased (P 〈 0·01) by the sorghum supplements. By 48 days, P1-supplemented steers were eating 29·5% more hay than non-supplemented steers, and P2 steers were eating 43·5% more hay than the non-supplemented steers. S1 supplemented steers were eating 29·5% less, and S2 steers 23% less hay than non-supplemented steers. Steers lost weight on the basal hay diet, and at the lower level of sorghum (S1) supplementation, but were able to maintain weight at the higher level (S2) of supplementation. In contrast, steers supplemented with protein gained weight (P 〈 0·01): 430 g/day on P1 and 700 g/day on P2 treatments. None of the steers offered combinations of P and S had live-weight changes as high as those offered only protein supplements. There was no evidence of compensatory gain by the smaller steers in Expt 2 when grazing and unsupplemented.Glucose kinetics in plasma were studied in each steer on day 35 of Expt 1 by means of a single intravenous injection of [2-3H]glucose. The quantity of glucose in the sampled pool and the total rate of glucose entry into the pool (GER) were higher (P 〈 0·01) in steers that were protein supplemented, with GER being related to both ME intake and to N intake per unit ME intake.Urea pool size and entry rate were also estimated on day 35 of Expt 1 using a single intravenous injection of [14C]urea. The quantity of urea in the sampled pool, and entry rate into the pool were increased significantly (P 〈 0·01) by protein, but reduced (P 〈 0·05) by sorghum, supplementation. Rumen ammonia concentrations were low in steers given the hay alone, and when supplemented with sorghum (10–15 mg N/l), but were significantly higher (70 mg N/l; P 〈 0·01) during protein supplementation.It was concluded that growth of cattle on the basal ration was restricted by low voluntary intakes of hay. Intake was increased substantially by protein supplementation. The consequent increase in live weight was due to a greater intake of organic matter which was accompanied by a greater synthesis of glucose and availability of amino acids in the animals.

Description: The study examined the reliability of predicting faeces output of cattle from chromium oxide (Cr2O3) released from a device (CRD) inserted in the rumen. Sixteen steers were selected from four genotypes and were offered a diet of low quality pasture hay with a protein meal supplement. The steers were placed in metabolism crates which allowed for total collection of faeces over two 5-day periods, days 6–9 (period 1), and days 13–16 (period 2), of a 20-day extrusion cycle of the CRD. Three faeces samples were taken from each steer per rectum; grab samples in the a.m. and p.m. and a daily subsample, that is, a sample of each daily total collected output. Cr2O3 release rates were derived for each sampling regime (a.m., p.m. and daily from the Cr2O3 content of faeces). These derived rates were compared with the release rate specified by the supplier to determine differences and any bias associated with the sampling regimes. Release rates were also derived from the predicted expiry date calculated from plunger travel in the CRD. Organic matter digestibility of the diet was determined from measurements of feed intake and faeces output over the 4 days for each steer and from an in vitro technique on diet samples. Predicted forage intakes were estimated using the mean faeces output collected over 4 days in combination with either the in vivo or in vitro digestibility estimates. Correlations between actual forage intake and predicted forage intake for each method were calculated and the bias in predicted forage intake between methods was compared.The daily data revealed significant effects of steer (and/or CRD) and sampling period on the estimated release rate of Cr2O3 from the CRD. However, whilst there was only a period effect on the release rate with p.m. sampling there was a linear decline in release rate with the a.m. sampling. The correlation between predicted and actual forage intake was greatly reduced when in vivo digestibility was replaced by in vitro digestibility.The results of this study suggest that the CRD had release rates less than specified and therefore devices should be calibrated for both the animals and the pastures prior to use. Furthermore, faeces sampling should be restricted to

Description: SUMMARYThe effects of supplements of protein meal or sorghum grain given to young cattle for 140 days during their first winter and spring post-weaning, were recorded over 560 days for cattle grazing on low quality pastures in subtropical Australia. The supplements were offered to steers in four treatment groups, replicated three times, at the following rates per head to late spring: (a) mineral mix (M) + cotton-seed hulls, 90g/day (control), (b) M + protein meal, 600 g/day (protein daily), (c) as for (b) but at 2·1 kg/3·5 days (protein twice-weekly), or (d) M + sorghum grain, 560 g/day (sorghum). For the next 130 days, to late summer, only supplement (c) was continued while the remaining three groups were not supplemented. None of the supplements was offered for the final 290 days of the experiment when the steers grazed an improved pasture.At the end of the first spring, the live weight of the steers supplemented daily and twice-weekly with protein was respectively 229 and 216 kg. These were significantly (p 〈 0·01) heavier than the sorghum-supplemented (174 kg) or control steers (160 kg). At the end of the first summer, the steers given supplements of protein meal twiceweekly, or daily, remained significantly heavier (265, 250 kg respectively) than sorghum-supplemented or control steers (209, 198 kg). By the second summer, the steers previously given protein supplements were still heavier than the steers from the control group (357 v. 317 kg, respectively).In steers which were offered the protein supplement during winter and spring, samples of blood taken at the end of spring had lower (P 〈 0·01) plasma ratios of glycine to branched-chain amino acids (valine, leucine and isoleucine) and a lower ratio of methionine: valine, than in the steers which were not offered the supplement. These ratios were significantly (P 〈 0·05) correlated with live-weight change over the preceding 140 days. On this basis it was considered that the improved growth of the steers offered the protein supplements was associated with an increased availability of specific essential amino acids, which may have initiated in the steers an increased appetite for pasture D.M.

Description: 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×H) and first-cross Brahman×Hereford (B×H), Simmental×Hereford (S×H) and Friesian×Hereford (F×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 pre-weaning 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 (R2) between models for calf 210-day weight and ADGtotal which included average lactation milk yield and other cow traits (highest R2=69%) and models which included other cow traits but no milk yield estimate (highest R2=57%) were

Description: Thirty steers were used in two pen experiments (Expts 1 and 2), and 27 of these in a third (Expt 3), to quantify their responses of hay intake, rumen ammonia nitrogen (RAN) concentrations, and liveweight to inputs of rumen soluble nitrogen (urea) and rumen undegradable protein (formaldehyde-treated casein; F-casein) when added to a basal diet of low quality hays. The hays were made from unimproved native pastures typical of those grazed by cattle in the subtropics of Australia and contained 7·8 g N/kg dry matter (DM) with coefficient of organic matter digestibility of 0·503 in Expts 1 and 2, and 5·2 g N/kg DM with a digestibility range from 0·385 to 0·448 in Expt 3. The steers (15 months old) were either Brahman (B), Hereford (H) or the F1 Brahman×Hereford (BH) cross. Steers were offered supplementary minerals with the hays in each experiment. In Expt 1 (35 days) urea was sprayed on part of the hay, allowing for daily urea intakes (g/steer) of either 0, 5, 11, 16 or 26. In Expt 2 (42 days), F-casein was offered daily (g/steer) at either 0, 75, 150, 225 or 300 and in Expt 3 (56 days) discrete offerings were made of soluble casein (225 g/day), of urea (18 g/day)+F-casein (225 g/day) or of nil.There were significant linear effects of urea intake upon hay intake and liveweight change of steers. However, B steers had smaller increases in intake and liveweight change than did H steers, and B steers did not have a linear increase in RAN concentrations with increasing urea intake as did H and BH steers. In Expt 2 there were significant linear effects of F-casein supplements on hay intake and liveweight change of steers and a significant improvement in their feed conversion ratio (i.e. DM intake: liveweight change). The B steers did not differ from H and BH steers in liveweight change but had significantly lower hay intakes and non-significantly smaller increases in RAN with increasing F-casein intake. In Expt 3, hay intake of the steers increased with soluble casein (by 16·8%) and with urea+F-casein (24·5%). Only steers given urea+F-casein had a high RAN concentration (94 mg/l) and a high liveweight gain. The B steers had a liveweight loss and a lower hay intake than H or BH steers in Expt 3 but a higher RAN concentration.These studies have indicated the importance of the form and quantity of additional N required by cattle of differing breed types to optimize their feed intake and liveweight gain when offered low-N, low-digestible hays.