Modifying the NRC weight gain model to estimate daily gain for stockers grazing bermudagrass in the southern United States

The energy requirements, feed intake, and performance of grazing animals vary daily due to changes in weather conditions, forage nutritive values, and plant and animal maturity throughout the grazing season. Hence, realistic simulations of daily animal performance can be made only by the models that can address these changes. Given the dearth of simple, user-friendly models of this kind, especially for pastures, we developed a daily gain model for large-frame stockers grazing bermudagrass [Cynodon dactylon (L.) Pers.], a widely-used warm-season perennial grass in the southern United States. For model development, we first assembled some of the classic works in forage-beef modeling in the last 50 years into the National Research Council (NRC, 1984) weight gain model. Then, we tested it using the average daily gain (ADG) data obtained from several locations in the southern United States. The evaluation results showed that the performance of the NRC model was poor as it consistently underpredicted ADG throughout the grazing season. To improve the predictive accuracy of the NRC model to make it perform under bermudagrass grazing conditions, we made an adjustment on the model by adding the daily departures of the modeled values from the data trendline. Subsequently, we tested the revised model against an independent set of ADG data obtained from eight research locations in the region involving about 4,800 animals, using 30 years (1991-2020) of daily weather data. The values of the various measures of fit used, namely the Willmott index of 0.92, the modeling efficiency of 0.75, the R 2 of 0.76, the root mean square error of 0.13 kg d -1, and the prediction error relative to the mean observed data of 24% demonstrated that the revised model mimicked the pattern of observed ADG data satisfactorily. Unlike the original model, the revised model predicted more closely the ADG value throughout the grazing season. The revised model may be useful to accurately reflect the impacts of daily weather conditions, forage nutritive values, seasonality, and plant and animal maturity on animal performance.

Autumn de-worming

Autumn is traditionally a time when most horses are de-wormed with one or more products that are effective against tapeworms and both adult and larval roundworms. However, the increasing prevalence of resistance and availability of diagnostics should prompt scrutiny of whether blanket de-worming at this time of year is appropriate. If management is good and horses are at low-risk of clinical disease, then there may be no need to use anthelmintics. Serology provides a means of assessing exposure to both cyathostomins and tapeworms, but it has its limitations and does not provide a validated means of assessing the risk of parasitic disease. The results of serology, results of faecal worm egg counts performed in the population through the preceding grazing season, and knowledge of management practices in the population should all be considered when assessing whether the risk of the disease to the individual is such that it must take priority over the ever-increasing threat of resistance in the equine population.

PSXIV-21 Performance of hair lambs maintained on stockpiled permanent pasture mixed with Cleome gynandra L. at multiple stocking densities

Stockpiled forage may extend the grazing season for sheep, reducing feeding costs. Additionally, internal parasites are a problem in sheep managed under grazing conditions. Plants high in phenolic compounds have potential to reduce parasite problems. Cleome gynandra is one such plant that has traditionally been used to treat worms in humans. Thirty-six Katahdin × Dorper lambs (38.8 ± 0.7 kg) were used to investigate the effect of stockpiled forages on lamb performance at different stocking densities: (i) 23 lambs/ha (LOW), (ii) 46 lambs/ha (MED), and (iii) 92 lambs/ha (HIGH). To test C. gynandra for anthelmintic properties, lambs were assigned to (i) permanent pastures (PP), and (ii) PP inter-seeded with C. gynandra (CL). The LOW lambs had the highest ADG (83.8 ± 10.5 g/day), MED lambs were intermediate (48.4 ± 11.6 g/day) and HIGH lambs were lowest (11.0 ± 10.6 g/day; P < 0.001). Lamb BCS did not differ between stocking densities or pasture types (P > 0.10). Fecal egg counts did not differ (P > 0.10) between pasture treatments. In conclusion, stockpiled forages may extend the grazing season for yearling lambs in Southern California. The lack of effect on parasite egg counts may be attributed to grazing C. gynandra at mature stage when nutritional and medicinal values were at their lowest. Future research can clarify the economics of grazing stockpiled forages for sheep at different stages of production, and nutritional effect of C. gynandra on carcass quality.

Generic Relationships between Field Uses and Their Geographical Characteristics in Mountain-Area Dairy Cattle Farms

In mountain farms, challenges posed by the degree of land slope, altitude and harsh climate further compound multiple other possible constraints, particularly in relation to the distance of the farm from the farmstead. This study focused on how mountain-area dairy farmers factor the geographical characteristics of their fields into their field-use decisions. To that end, we surveyed 72 farmers who farm the traditional Salers breed of cattle and 28 specialised dairy system farmers in the central Massif region, France. Information was collected on the uses and geographical characteristics of all grassland fields (n = 2341) throughout the entire outdoor grazing season, without identifying farmers’ rationales for their field-use decisions. Field-use classes were constructed for the traditional Salers system per group of fields (grazed-only, cut-only, grazed-and-cut) and then used to classify fields in the specialized dairy system. The geographical characteristics, which were associated afterwards, were significantly different between the field groups and between field-use classes. Grazed-only fields were found to be more sloping and cut-only fields were smaller and further from the farmstead. Distance/area combinations were different according to field use (animal category, earliness of first cut, grazing and cutting sequence) and were decisive for all field-use classes. This study allowed the identification of generic relationships between field uses and their geographical characteristics in mountain-area dairy cattle farms.