Animal最新文献

Fluctuating asymmetry (FA) is the small, random difference between the left and right sides of paired traits and is widely used as an indicator of developmental instability and animal welfare. This study investigated whether heat stress (HS) and access to elevated multifunctional platforms influence FA in live birds, carcasses, bones, and feathers, as well as feather morphology and microstructure. In each round, 560 male Ross 308 broilers were reared for 43 days. The facility had two compartments: one under thermoneutral (TN) conditions and the other subjected to HS. Each compartment housed one pen with platforms and one barren pen. HS was applied by raising the temperature to 32 °C for 6 h daily from day 29 to day 40 (except days 34-35). The experiment was conducted over three production cycles. On day 40, 20 birds per group per cycle were selected for live bilateral measurements. On day 42, the same birds were slaughtered and additional bilateral traits were recorded on carcasses and, after cleaning, on bones. First primary feathers from both wings were collected for morphometry and microstructure analyses. Composite FA did not differ for live birds (P = 0.079), carcasses (P = 0.429), or feathers (P = 0.336); however, bones showed a treatment effect (P = 0.029). Bone FA was lower in HS birds with platforms compared with TN birds in barren pens (P = 0.025), but did not differ from TN birds with platforms or HS birds in barren pens. Trait-specific effects were detected for tibiotarsus width (P = 0.026), femur length (P = 0.030) and femur width (P = 0.002). Feather morphometry showed interactions (temperature and enrichment) for rachis length (P < 0.001) and inner vane width (P = 0.001). HS birds in barren pens had the shortest rachises, whereas HS birds with platforms developed longer rachis. For microstructure, interactions were detected for barb width (P < 0.001). Barb width was greater in TN pens with platforms compared to HS pens with platforms. Overall, bone FA was significantly lower in the HS + platform group only when compared with the TN barren group. Feather morphometry and microstructure were highly plastic to treatments, reflecting adaptive responses that may also serve as welfare indicators.

Subclinical hypocalcaemia (SCH) is a significant metabolic disorder affecting dairy cattle. Research has shown that dairy cows experience three states of SCH, known as transient, delayed, and persistent SCH. Our objective was to identify potential risk factors for dairy cows with delayed and/or persistent SCH that are managed under grazing conditions. Grazing Holstein cows (n = 158) were randomly selected from eighteen farms in southern Chile, of which 39 were in their first lactation (24.7%), 30 were in their second lactation (19.0%), and 89 were in third or more lactations (56.3%). Lactation data and body condition score (BCS) at calving were recorded for each cow. Blood samples were collected at calving and 7 days postpartum to determine concentrations of plasma ionised calcium (iCa) and ionised magnesium (iMg). Using plasma iCa concentration thresholds of ≤ 0.92 mmol/L at calving and ≤ 1.05 mmol/L at 7 days postpartum, cows were classified as normocalcaemic (33.4%), transient SCH (13.3%), delayed SCH (29.3%), and persistent SCH (24.0%). Older cows had significantly higher SCH prevalence at calving compared to younger cows. However, by day 7 postpartum, the proportion of delayed/persistent SCH cases was similar across all three parity groups. The prevalence of SCH over this period remained consistent for first- and second-parity cows. A linear regression model was built to analyse the concentration of plasma iCa at 7 days postpartum. Results showed that plasma iMg concentration at 7 days postpartum, plasma iCa concentration at parturition, parity, and BCS at calving were significant predictors in the final model. A logistic regression model was used to identify risk factors for SCH at 7 days postpartum. The only significant variables in the final model were BCS at calving and plasma iMg concentration at 7 days postpartum. Cows with plasma iMg concentrations ≤ 0.5 mmol/L were 6.26 times more likely to develop persistent or delayed SCH at 7 days postpartum compared to those with plasma iMg concentrations > 0.5 mmol/L. Overall, our results demonstrate that plasma iMg at 7 days postpartum is an important risk factor associated with plasma iCa concentrations and the occurrence of delayed/persistent SCH in grazing dairy cows. Other potential risk factors, such as parity, plasma iCa concentration at calving, and BCS at calving, may also play a role in the presentation of these conditions.

In semi-extensive cattle systems, cows may be exposed to undernutrition, which may reduce the productivity of beef herds. The objective of this study was to evaluate the effects of undernutrition and supplementation with hydroxytyrosol (HT, polyphenol derived from olive leaves) during the last third of gestation on cow productivity, metabolic and hormonal profiles, transfer of passive immunity to calves via colostrum, and birth weight and vitality of newborn calves. A total of 109 pregnant beef cows (Parda de Montaña, n = 63; and Pirenaica, n = 46) were assigned into four feeding groups following a 2 × 2 factorial design, according to feeding level (100 vs 60% of nutritional requirements) and dietary HT supplementation (Control vs HT; 0 and 180 mg HT/kg total mixed ration) between 28 and 40 week of gestation. At week 28, all groups (100-Control, 100-HT, 60-Control and 60-HT) were balanced in BW, body condition score (BCS), breed and age. Cow BW and BCS were recorded, and plasma concentrations of non-esterified fatty acids (NEFAs), cholesterol, insulin-like growth factor 1 (IGF-1), glucose, fructosamine and urea were analysed every 3 weeks during the last third of gestation. Cow cortisol was measured in late pregnancy and shortly after parturition. Colostrum and plasma from cows and calves were analysed for immunoglobulin (IgM, IgG) concentrations. At birth, calf weight and a vitality test were recorded. Undernutrition in the last third of pregnancy reduced dam BW at parturition and induced fat mobilisation. Hydroxytyrosol supplementation in the 60-HT group led to a more moderate increase in NEFA and cholesterol levels, along with a lesser decline in IGF-1 levels. Hydroxytyrosol also decreased the dam plasma urea levels. Calves from HT-supplemented dams were heavier at birth. Undernutrition during the last third of gestation resulted in elevated plasma cortisol levels in newborn calves, which persisted for 1 month, while dam cortisol levels were not affected. Plasma IgG concentrations were higher in HT-supplemented dams regardless of feeding level, and higher concentrations of IgM and IgG in colostrum were maintained throughout the first 24 h postpartum in them. Calf vitality was only affected by calving difficulty. Overall, undernutrition during the last third of gestation had negative effects on dam BW, BCS and indicators of metabolic status, partially alleviated by HT supplementation, and increased cortisol levels in newborns. Moreover, HT supplementation increased calf birth weight and helped to maintain colostrum IgM and IgG concentration during the first 24 h after calving.