Quantification of cow milk yield and pre-weaning calf growth response in temperate pasture-based beef suckler systems: A meta-analysis

Comparison of deworming strategies for pre-weaned beef calves

While anthelmintic treatment in young calves at first vaccination has not proven repeatedly effective in improving weight gain, there is evidence that treatment 90 day prior to weaning can enhance weight gain. This is difficult in most California cow/calf operations as after initial vaccination, calves are not again handled until preconditioning just prior to weaning. In an attempt to increase weight gain without the need for anthelmintic retreatment prior to preconditioning, 130 cow/calf pairs were stratified and assigned to three treatments of eprinomectin extended release injection (150 d efficacy), doramectin conventional injection, and an untreated control. Dams and calves received the same treatment. All treatments were commingled on irrigated pasture in Northern California. Sampling included weight (d 0, 75, and 145), fecal parasite (d 0, 14, 75, and 145), cow body condition score (d 0, 75, and 145), and cow pregnancy detection (days bred). Calf weight gain was not impacted by anthelmintic treatment (P = 0.44). However, cow weight gain was impacted by treatment (P < 0.01), with eprinomectin extended release showing higher weight gain than both doramectin conventional and the control (ADG kg 0.29, 0.23, 0.22, respectively). Cow weight gain differences were expressed greater toward the end of the trial than early on. Fecal egg count sampling failed to explain the difference in cow weight gain. Cow body condition score (P = 0.15) and days bred (P = 0.50) were not significantly affected by treatment. Although cow weight gain increased with an extended release anthelmintic treatment, this effect did not seem to be evident in suckling calves on high quality irrigated pastures in Northern California when compared to a conventional injectable and control treatments. Neither anthelmintic treatment appeared beneficial over a control when administered to suckling calves during initial vaccination at approximately 90 days of age.

The Association between Charolais Cows' Age at First Calving, Parity, Breeding Seasonality, and Calf Growing Performance

The objective of this study was to evaluate the impact of cows' calving ages and newborn calf body weight on the pre-weaning growth rates of calves under the farming conditions of a northeastern European country. The females were purebred Charolais cows that calved between 2019 and 2022. A total of 130 calves (bulls = 76; heifers = 54) were observed during the evaluation. The investigation showed that, based on gender, bulls had a 4.28% higher birth weight than heifers (p < 0.05). The gender of the calves affected their weight, indicating that newborns bulls were significantly heavier. Calf gender affected calf growing performance. Male calves' weight gain was higher than that of females in the time before weaning (210 days). The highest gain of bulls was observed from 211 days to 365 days after birth. The average daily weight of male calves during this period was 6.16% (p < 0.001) higher compared to the period up to 210 days after birth. Heifers had a higher daily weight in the period up to 210 days after birth, and the daily weight gain was 12.9% (p < 0.001) higher in this period compared to the period from 211 to 365 days after birth. We observed a higher weight gain in calves from mothers with a higher number of calvings. Being born from cows with four or more calvings had a significant effect on the weight gain of calves in the period up to 210 days (p < 0.05). In the period up to 210 days, the weight gain of calves born from cows with two calvings was the lowest and was 9.79% lower compared to calves born from cows with four and more calvings (p < 0.05). The best weights were obtained from calves born in the spring and autumn seasons. Calves born in spring, summer, and autumn differed in weight by 0.37 kg. The calves of cows that were inseminated in the autumn season had the highest gain in the period up to 210 days and also from 210 to 365 days (p < 0.05). In our study, significantly higher average birth weight of calves was detected in autumn compared to summer and winter (p < 0.05). Also, the highest gain was found from 211 to 365 days after birth in the summer season, but the difference was only 1.47% (p < 0.05).

Beef cows' performance and metabolic response to short nutritional challenges in different months of lactation

Lactating cows can react to changes in nutrient availability with a range of behavioural and physiological mechanisms, which may differ among lactation stages. We investigated the effects of short feed restriction and refeeding periods on beef cows' performance and metabolic status in different months of lactation. For this, Parda de Montaña beef cows [n = 31; 626 ± 47.7 kg body weight (BW)] were subjected to short nutritional restriction and refeeding cycles, which were repeated in months 2, 3 and 4 of lactation. Each month, cows were consecutively fed a diet to meet 100% of their energy and protein requirements during a 4-day basal period, 55% during a 4-day restriction period, and again 100% during a 4-day refeeding period. The performance (energy balance, BW, milk yield and composition) and plasma metabolite concentrations (glucose, non-esterified fatty acids (NEFA), β-hydroxybutyrate (BHB), urea and malondialdehyde) were measured daily. Most of the traits were significantly affected by the interaction between feeding period and lactation month. Feed restriction induced milk yield loss, decreased milk protein and increased milk urea contents to different extents. The plasma NEFA concentrations rose with restriction in months 2, 3 and 4 but BHB and urea concentrations increased only in month 4. Most of these metabolites lowered to basal values during refeeding. These results suggest that beef cows use different adaptation strategies to cope with nutritional challenges as lactation advances, body fat mobilisation predominates in early lactation and protein catabolism prevails at later stages.

Modelling beef cows' individual response to short nutrient restriction in different lactation stages

Short-term nutrient restrictions can occur naturally in extensive beef cattle production systems due to low feed quality or availability. The aims of the study were to (1) model the curves of milk yield, plasma non-esterified fatty acids (NEFAs) and β-hydroxybutyrate (BHB) contents of beef cows in response to short nutritional challenges throughout lactation; (2) identify clusters of cows with different response profiles; (3) quantify differences in cows' response between the clusters and lactation stages. Data of BW, body condition score (BCS), milk yield, NEFA, and BHB plasma concentration from 31 adult beef cows (626 ± 48 kg at calving) were used to study the effect of 4-day feed restriction repeated over months 2, 3 and 4 of lactation. On each month, all cows received a single diet calculated to meet the requirements of the average cow: 100 % requirements for 4 days (d-4 to d-1, basal period), 55 % requirements on the next 4 days (d0 to d3, restriction period) and 100 % requirements for 4 days (d4 to d7, refeeding period). Natural cubic splines were used to model the response of milk yield, NEFA and BHB to restriction and refeeding in the 3 months. The new response variables [baseline value, peak value, days to peak and to regain baseline, and areas under the curve (AUC) during restriction and refeeding] were used to cluster cows according to their metabolic response (MR) into two groups: Low MR and High MR. The month of lactation affected all the traits, and basal values decreased as lactation advanced. Cows from both clusters had similar BW and BCS values, but those in the High MR cluster had higher basal milk yield, NEFA and BHB contents, and responded more intensely to restriction, with more marked peaks and AUCs. Reaction times were similar, and baseline values recovered during refeeding in both clusters. Our results suggest that the response was driven by cows' milk potential rather than size or body reserves, and despite high-responding cattle's higher milk yield, they were able to activate metabolic pathways to respond to and recover from the challenge.

Beta-Glucan Alters Gut Microbiota and Plasma Metabolites in Pre-Weaning Dairy Calves

The present study aims to evaluate the alterations in gut microbiome and plasma metabolites of dairy calves with β-glucan (BG) supplementation. Fourteen healthy newborn dairy calves with similar body weight were randomly divided into control (n = 7) and BG (n = 7) groups. All the calves were fed on the basal diet, while calves in the BG group were supplemented with oat BG on d 8 for 14 days. Serum markers, fecal microbiome, and plasma metabolites at d 21 were analyzed. The calves were weaned on d 60 and weighed. The mean weaning weight of the BG group was 4.29 kg heavier than that of the control group. Compared with the control group, the levels of serum globulin, albumin, and superoxide dismutase were increased in the BG group. Oat BG intake increased the gut microbiota richness and decreased the Firmicutes-to-Bacteroidetes ratio. Changes in serum markers were found to be correlated with the plasma metabolites, including sphingosine, trehalose, and 3-methoxy-4-hydroxyphenylglycol sulfate, and gut microbiota such as Ruminococcaceae_NK4A214, Alistipes, and Bacteroides. Overall, these results suggest that the BG promotes growth and health of pre-weaning dairy calves by affecting the interaction between the host and gut microbiota.

Effect of calving to timed artificial insemination interval on fertility of beef cows

The objectives of this study were to determine the effect of calving to timed artificial insemination (C-TAI) interval on fertility of Bos taurus and Bos indicus cows, and to determine the best C-TAI interval to include postpartum cows in TAI programs in each genotype (B. taurus and B. indicus). In experiment 1, a retrospective study was performed, with data from 2709 TAI in Bos taurus and Bos indicus cows with different C-TAI intervals. There was a positive linear effect of C-TAI interval on the pregnancy probability (P < 0.0001). However, there was no effect or interaction with the genotype. When C-TAI intervals were grouped in classes, pregnancy rate differed in groups (P < 0,05). Receiver operating characteristic (ROC) analysis was performed and it was observed that 52 days would be the better C-TAI interval to maximize fertility in beef cows. According to previous result, we further stratified into two C-TAI interval groups (≤ 52 days or > 52 days). Cows with C-TAI longer than 52 days (C-TAI>52) had greater pregnancy rate (56%) than cows with short C-TAI (46%; P < 0.01). In experiment 2, 18 postpartum beef cows were subjected to TAI protocol at different C-TAI intervals (n = 6 cows per group): 40, 60 or 80 days postpartum. Cows with 60 days of C-TAI had a greater preovulatory follicle diameter than cows with 80 days postpartum (P < 0.05). The C-TAI interval did not affect (P > 0.05) the ovulation rate nor the proportion of endometrial polymorphonuclear leukocytes. We conclude that C-TAI interval affects pregnancy rate in both Bos taurus and Bos indicus. We recommend a C-TAI interval longer than 52 days to increase fertility of beef cows included in TAI programs.