Medium Quality Pasture Research Articles

Which is the best phenotypic trait for use in a targeted selective treatment strategy for growing lambs in temperate climates?

Targeted selective treatment (TST) requires the ability to identify the animals for which anthelmintic treatment will result in the greatest benefit to the entire flock. Various phenotypic traits have previously been suggested as determinant criteria for TST; however, the weight gain benefit and impact on anthelmintic efficacy for each determinant criterion is expected to be dependent upon the level of nematode challenge and the timing of anthelmintic treatment. A mathematical model was used to simulate a population of 10,000 parasitologically naïve Scottish Blackface lambs (with heritable variation in host-parasite interactions) grazing on medium-quality pasture (grazing density=30 lambs/ha, crude protein=140g/kg DM, metabolisable energy=10MJ/kg DM) with an initial larval contamination of 1000, 3000 or 5000 Teladorsagia circumcincta L3/kg DM. Anthelmintic drenches were administered to 0, 50 or 100% of the population on a single occasion. The day of anthelmintic treatment was independently modelled for every day within the 121day simulation. Where TST scenarios were simulated (50% treated), lambs were either chosen by random selection or according to highest faecal egg count (FEC, eggs/g DM faeces), lowest live weight (LW, kg) or lowest growth rate (kg/day). Average lamb empty body weight (kg) and the resistance (R) allele frequency amongst the parasite population on pasture were recorded at slaughter (day 121) for each scenario. Average weight gain benefit and increase in R allele frequency for each determinant criterion, level of initial larval contamination and day of anthelmintic treatment were calculated by comparison to a non-treated population. Determinant criteria were evaluated according to average weight gain benefit divided by increase in R allele frequency to determine the benefit per R. Whilst positive phenotypic correlations were predicted between worm burden and FEC; using LW as the determinant criterion provided the greatest benefit per R for all levels of initial larval contamination and day of anthelmintic treatment. Hence, LW was identified as the best determinant criterion for use in a TST regime. This study supports the use of TST strategies as benefit per R predictions for all determinant criteria were greater than those predicted for the 100% treatment group, representing an increased long-term productive benefit resulting from the maintenance of anthelmintic efficacy. Whilst not included in this study, the model could be extended to consider other parasite species and host breed parameters, variation in climatic influences on larval availability and grass growth, repeated anthelmintic treatments and variable proportional flock treatments.

Genetic correlations between body weight change and reproduction traits in Merino ewes depend on age.

Merino sheep in Australia experience periods of variable feed supply. Merino sheep can be bred to be more resilient to this variation by losing less BW when grazing poor quality pasture and gaining more BW when grazing good quality pasture. Therefore, selection on BW change might be economically attractive but correlations with other traits in the breeding objective need to be known. The genetic correlations (rg) between BW, BW change, and reproduction were estimated using records from approximately 7,350 fully pedigreed Merino ewes managed at Katanning in Western Australia. Number of lambs and total weight of lambs born and weaned were measured on approximately 5,300 2-yr-old ewes, approximately 4,900 3-yr-old ewes, and approximately 3,600 4-yr-old ewes. On a proportion of these ewes BW change was measured: approximately 1,950 2-yr-old ewes, approximately 1,500 3-yr-old ewes, and approximately 1,100 4-yr-old ewes. The BW measurements were for 3 periods. The first period was during mating period over 42 d on poor pasture. The second period was during pregnancy over 90 d for ewes that got pregnant on poor and medium quality pasture. The third period was during lactation over 130 d for ewes that weaned a lamb on good quality pasture. Genetic correlations between weight change and reproduction were estimated within age classes. Genetic correlations were tested to be significantly greater magnitude than 0 using likelihood ratio tests. Nearly all BW had significant positive genetic correlations with all reproduction traits. In 2-yr-old ewes, BW change during the mating period had a positive genetic correlation with number of lambs weaned (rg = 0.58); BW change during pregnancy had a positive genetic correlation with total weight of lambs born (rg = 0.33) and a negative genetic correlation with number of lambs weaned (rg = -0.49). All other genetic correlations were not significantly greater magnitude than 0 but estimates of genetic correlations for 3-yr-old ewes were generally consistent with these findings. The direction of the genetic correlations mostly coincided with the energy requirements of the ewes and the stage of maturity of the ewes. In conclusion, optimized selection strategies on BW changes to increase resilience will depend on the genetic correlations with reproduction and are dependent on age.

Improved beef production from supplementation of Hereford, Brahman and crossbred cattle grazing low and medium quality pastures in the subtropics of Australia

AbstractSubtropical grasslands are low in organic matter digestibility (OMD) (0·60) and nitrogen (N) (15 g/kg) for much of the year and this limits cattle production which is characterized by low calving rates and low weaning weights. Production has been based on Bos taurus British breeds of cattle but this is changing and now many breeding herds comprise B. indicus cows and their crosses. This change has increased some aspects of production, but low calving rates persist.A 4-year study was undertaken with a view to improve calving rates and weaner output by supplementing cows grazing either native or improved pastures with a high protein oilseed meal (cottonseed meal; CSM) on four sites. These sites were subdivided into a total of 36 paddocks to allow for two replications in a 3 breeds × 3 supplementation rates × 2 pastures factorial design. Selected cows (no. = 216) from Hereford (H), Brahman (B) and Brahman × Hereford (BH) breed types were set to graze either native pastures (0·45 to 0·62 OMD, 8 to 15 gN per kg; low quality) or improved pastures (0·47 to 0·67 OMD, 10 to 22 g N per kg; medium quality). Cows were given either 0, 750 or 1500 glday of CSM for 130 days from calving until 4 weeks into a 12- to 13-week mating period. The CSM was given as two meals per week.Live weight at mating of cows on the low quality pasture was increased (P < 0·01) over those not supplemented by feeding either 750 g CSM per day (H and B cows) or 1500 g CSM per day (all cows). There was no significant effect of supplementation on the mating weights ofB cows grazing the medium quality sites. Calving rate ofB cows was not increased by their supplementation on either low (4-year mean 58·3 %) or medium quality pastures (66·8%) but did tend to be higher in H cows when supplemented at 1500 g CSM per day on the low (66·7 v. 78·0 (s.e. 6·09) %; P < 0·1) and medium quality pastures (70·5 v. 93·5 (s.e. 4·72) %). An increased calving rate (65·8 (s.e. 6·6) % to 83·2 (s.e. 5·82) % in supplemented BH cows grazing low quality pastures approached significance (P < 0·1) when given CSM at 1500 glday but there was no increased trend in calving rate when this breed type was supplemented on medium quality pastures.Weaning weights of calves from and B and BH cows were increased (P < 0·05) by supplementation of their dams at 750 glday and for calves weaned from H cows supplemented at 1500 glday of CSM. Supplementation at 1500 glday on low quality pastures increased weaner output per cow mated by 120% for H, by 65% for BH cows and by 50% for B cows. Weaner output was increased by 34 and 40%, respectively, for B and H cows when supplemented at 750 glday and grazing medium quality pastures but there was no significant effect of supplementation on output from BH cows. Responses in many parameters differed between years. These results were interpreted as a response to the protein in the oilseed meal supplement by B. taurus and B. taurus × B. indicus cross cows grazing on the subtropical pastures. The study also highlighted that responses to the meal differed between breed types, between the quality of the grazed pasture and between the years of supplementation.

Evaluation of Hereford and first-cross cows on three pasture systems. II. Growth of Hereford and Brahman sired calves out of mature cows

SUMMARYThe preweaning growth of the progeny of mature cows grazing high, medium or low quality pasture was evaluated. The cows were 5–9 years of age at the beginning of the study and were either purebred Hereford (H x H), first-cross Brahman x Hereford (B x H), Simmental x Hereford (S x H) or Friesian x Hereford (F x H). Hereford and Brahman bulls were mated to these cows for three mating seasons commencing in 1982, at Grafton, New South Wales, Australia. Records on 634 calves born over three consecutive years were used.Most traits were subject to significant sire breed or dam breed effects or their interactions with one or more of the other main effects (pasture, year of birth of calf, cow age and sex of calf). The incidences of calving difficulty and stillbirths were exceptions. Stillbirths (mean of 3·8%) were not affected by any of the effects studied, while calving difficulty was affected only by sex of calf effect (males, 3·9%; females, 0·8%). The mean calving date of Brahman-sired calves was 11·4 days later (P < 0·05) than that of Hereford-sired calves. Differences between Brahman-sired and Hereford-sired calves for weaning weight were not significant for S x H (Brahman, 237 kg; Hereford, 232 kg) and FxH (Brahman, 238kg; Hereford, 238kg) dams. For HxH dams however, calves sired by Brahman were heavier at weaning (205 kg) than those sired by Hereford (193 kg) bulls, while for B x H dams the reverse was true (Brahman, 222 kg; Hereford, 231 kg). For calves with B x H dams average daily gain (ADG) was the same (957 g/day) for each sire breed, while for the other dam breeds, Brahman-sired calves had a higher ADG than Hereford-sired calves (862 v. 779, 1014 v. 946 and 1022 v. 950 g/day for H x H, S x H and FxH, respectively). Calves sired by Brahman bulls had > 90% eyelid pigmentation while Hereford-sired calves had 44–74%. On high quality pasture, the weaning weights and ADG of calves of F x H and S x H dams were higher than those of B x H and HxH dams. On medium quality pasture, weaning weight of calves of crossbred dams (B x H, S x H and FxH) were similar but higher than those of H x H dams. On low quality pasture, mean weaning weight of calves of B x H was higher than those of S x H and F x H dams, which in turn, were higher than that of H x H dams.

Evaluation of Bos indicus and Bos taurus straightbreds and crosses. III. Direct and maternal genetic effects on growth traits

Data on Brahman and Hereford cattle and their crosses were used to estimate direct additive, direct heterosis, maternal additive and maternal heterosis effects for pre-weaning and post-weaning liveweights, average daily gain (ADG) and height at various ages. The cattle were born at Grafton, N.S.W., and raised on high, medium and low quality pastures until weaning. During the post-weaning period, the steers were grown in three environments in New South Wales, while the heifers remained at Grafton. Genetic effects were estimated by regression and the additive components expressed as deviations from Hereford effect. Weaning weight and pre-weaning ADG of Hereford calves (both sexes) were 237.8 kg and 827 g/day on high, 210.5 kg and 704 g/day on medium, and 128.3 kg and 425 g/day on low quality pastures respectively. Post-weaning ADG of Hereford steers (weaning to 36 months) and heifers (weaning to 30 months) was 296 and 240 g/day respectively. Direct heterosis was significant (P<0.05) for most traits. Estimates of direct heterosis for weaning weight were 24.9 and 20.2 kg, and for pre-weaning ADG were 79 and 68 g/day, on high and medium quality pastures respectively. Direct heterosis for ADG of steers (weaning to 36 months) and heifers (weaning to 30 months) was 91 and 76 g/day respectively. Estimates of maternal heterosis for weaning weights were 14.9, 30.9 and 37.8 kg and for pre-weaning ADG were 31 (not significant), 105 and 153 g/day, for high, medium and low quality pastures respectively. Maternal heterosis for ADG of steers (weaning to 36 months) was -47 g/day. There was a negative direct additive effect on post-weaning ADG in environments where pasture quality was good, but the effect was not significant on poor quality pasture. Maternal additive effect was negative for birth weight for high and medium quality pastures and positive for weaning weight and pre-weaning ADG on low quality pasture. The performance of untested crosses can be predicted from the estimates and models provided.

Evaluation of Bos indicus and Bos taurus straightbreds and crosses. II. Post-weaning growth, puberty, and pelvic size of heifers

Post-weaning growth and body condition, puberty and pelvic size of 197 heifers comprising straightbred Hereford (HxH) and Brahman (BxB), first-cross (BxH) and back-cross (HxBH and BxBH) heifers were evaluated. The heifers were born over a 3 year period, and grazed improved and semi-improved pastures following weaning at Grafton, New South Wales. Prior to weaning, heifers had been reared by dams on three pasture systems (high, medium and low quality pastures). Heifers from low quality pre-weaning pasture had higher (P < 0.05) post-weaning liveweight gain than those from high and medium quality pastures. BxH heifers gained 71 g/day more (P < 0.05) than the mean gain of their contemporaries of the other genotypes, whose gains were similar, from weaning to either 26 or to 30 months of age. Liveweight at all ages was influenced by genotype x pre-weaning pasture system interaction. At 30 months of age, BxH heifers from high and medium pre-weaning pastures were the heaviest. At the same age, but from low quality pre-weaning pasture, heifers with crossbred dams (HxBH and BxBH) were the heaviest. Wither height depended significantly (P < 0.05) on the proportion of Bos indicus genes, increasing from 113.8 cm in the HxH heifers to 124.4 cm in the BxB heifers at 30 months of age. BxH heifers had a higher (P < 0.05) body condition score than their contemporaries of the other genotypes, which were in similar condition, at 26 and 30 months of age. On average (across pre-weaning pasture system), 9% of BxB heifers had reached puberty by 22 months of age compared to 62, 95, 82 and 64% (s.e.= 9) for HxH, HxBH, BxH and BxBH heifers respectively. No significant genotype differences were obtained in the height, width and size of the pelvic opening of the heifers, measured just prior to the beginning of the mating season at 26 months of age.

Evaluation of Bos indicus and Bos taurus straightbreds and crosses. I. Post-weaning growth of steers in different environments

Post-weaning growth of 186 steers comprizing straightbred Hereford (H x H) and Brahman (B x B), first-cross (B x H) and back-cross (H x BH and B x BH) was evaluated. The steers had been raised to weaning (8 months of age) by dams which grazed either high, medium or low quality pasture (pre-weaning pasture system) at Grafton, N.S.W. The steers were grown on pasture from time of weaning in one of three locations in New South Wales representing subtropical, temperate-good, and temperate-good to poor environments, and slaughtered when the average fat cover of the back-cross steers in each environment was 4-10 mm at the 12113th rib. Pre-weaning pasture system had a significant effect on post-weaning growth, with mean post-weaning (8-48 months of age) average daily gain (ADG) of steers from low (327� 8 g/day) being higher than that of steers from medium (304�6 g/day), which in turn, was higher than that of steers from high (276�9 g/day) quality pre-weaning pasture, indicating that steers from low and medium quality pastures exhibited compensatory growth. From 8 to 24 months of age, first-cross BxH steers had the highest ADG in all environments. The ranking of the other genotypes differed across environments. In the environment where growth rate was lowest (178 g/day for B x H), B x B and B x BH steers grew faster than H x H and H x BH steers; where growth rate was highest (584 g/day for B x H), the order was reversed; and where growth rate was intermediate (323 g/day for B x H), there were no significant differences in ADG among H x H, H x BH, B x BH and B x B steers. Steers from only two environments were retained after 24 months of age. Mean ADG from 8 to 36 or 48 months of age was not significantly different among straightbred and back-cross steers, but was lower than that for the first-cross steers. Genotype x environment interaction for liveweight at slaughter was not significant. First-cross B x H steers were 56 kg (11%) heavier (P < 0.05) than back-cross steers, which in turn, were 37 kg (8%) heavier (P < 0.05) than straightbred steers at slaughter.

The Effect of Supplementation on the Fertility of Dairy Heifer Grazed on Medium Quality Pasture Under East African Conditions

The Effect of Supplementation on the Fertility of Dairy Heifer Grazed on Medium Quality Pasture Under East African Conditions

The Effect of Supplementation on the Growth of Dairy Heifers Grazed on Medium Quality Pasture Under East African Conditions

(1977). The Effect of Supplementation on the Growth of Dairy Heifers Grazed on Medium Quality Pasture Under East African Conditions. East African Agricultural and Forestry Journal: Vol. 42, No. 4, pp. 435-440.

Effect of Supplemental Feeding of Cows on Pasture on Milk Composition and Yield

Summary Thirty-five cows were used to study the effects on milk composition and production of supplementing medium-quality pasture with ground-shelled corn or corn silage. Rations were: 1) Corn; 2) corn plus silage; 3) corn (1 lb/6lb milk) plus silage; and 4) silage. Except for corn in Ration 3, feeds were fed ad libitum for 3 hr twice daily. Trial A compared Rations 1 and 4 and employed a reversal design with 40-day treatments. Trial B was a continuous study with 12-wk treatments. In Trial A, significant ration effects were noted for SNF, protein and fat in milk, and milk yields. Values for cows on corn and silage, respectively, were: 8.65, 3.22, 3.05%, and 39.9lb; 8.44, 3.11, 3.65%, and 35.8lb. In Trial B, persistency of production was over 80% for all groups. Cows on grain and silage had highest milk yields. SNF decreased as level of corn decreased (9.16, 8.92, 8.66, and 8.42% for consecutive groups). Milk protein accounted for most of the change in SNF. Fat in milk was lower on high-corn rations (2.53, 3.23, 3.50, and 3.59% for consecutive groups). Corn silage alleviated milk fat depression noted on high-corn rations. Treatment effects on milk composition were not complete until the 6th to 8th wk of treatment.

Animal Husbandry in Peru

Targeted selective treatment (TST) requires the ability to identify the animals for which anthelmintic treatment will result in the greatest benefit to the entire flock. Various phenotypic traits have previously been suggested as determinant criteria for TST; however, the weight gain benefit and impact on anthelmintic efficacy for each determinant criterion is expected to be dependent upon the level of nematode challenge and the timing of anthelmintic treatment. A mathematical model was used to simulate a population of 10,000 parasitologically naïve Scottish Blackface lambs (with heritable variation in host-parasite interactions) grazing on medium-quality pasture (grazing density = 30 lambs/ha, crude protein = 140 g/kg DM, metabolisable energy = 10 MJ/kg DM) with an initial larval contamination of 1000, 3000 or 5000 Teladorsagia circumcincta L3/kg DM. Anthelmintic drenches were administered to 0, 50 or 100% of the population on a single occasion. The day of anthelmintic treatment was independently modelled for every day within the 121 day simulation. Where TST scenarios were simulated (50% treated), lambs were either chosen by random selection or according to highest faecal egg count (FEC, eggs/g DM faeces), lowest live weight (LW, kg) or lowest growth rate (kg/day). Average lamb empty body weight (kg) and the resistance (R) allele frequency amongst the parasite population on pasture were recorded at slaughter (day 121) for each scenario. Average weight gain benefit and increase in R allele frequency for each determinant criterion, level of initial larval contamination and day of anthelmintic treatment were calculated by comparison to a non-treated population. Determinant criteria were evaluated according to average weight gain benefit divided by increase in R allele frequency to determine the benefit per R. Whilst positive phenotypic correlations were predicted between worm burden and FEC; using LW as the determinant criterion provided the greatest benefit per R for all levels of initial larval contamination and day of anthelmintic treatment. Hence, LW was identified as the best determinant criterion for use in a TST regime. This study supports the use of TST strategies as benefit per R predictions for all determinant criteria were greater than those predicted for the 100% treatment group, representing an increased long-term productive benefit resulting from the maintenance of anthelmintic efficacy. Whilst not included in this study, the model could be extended to consider other parasite species and host breed parameters, variation in climatic influences on larval availability and grass growth, repeated anthelmintic treatments and variable proportional flock treatments.