No abstract

Weaning of beef calves is usually done abruptly and early compared to the natural weaning of the species, and is associated with simultaneous exposure of calves to a range of social and environmental stressors. Behavioural and physiological responses to weaning indicate detrimental effects on the welfare of these animals. The development and assessment of weaning methods aiming at reducing or avoiding this problem must be supported by scientific knowledge of the morphological, physiological and psychological mechanisms involved in the establishment, maintenance and braking of the cow-calf bond. Solutions also depend on the understanding of the various stressors associated with weaning, among which are the change in diet, cessation of nursing, separation from the dam, the change to a new spatial environment and the need for social reorganization following removal of the adults from the group. This review discusses these issues and assesses the effectiveness of the methods so far proposed for improving the welfare of beef calves during the weaning period.

No abstract

No abstract

Two hundred and seventy-seven ewes were used in three experiments during late seasonal anoestrus to evaluate short-term progestogen primings for equine chorionic gonadotropin (eCG)-induced oestrus. In experiment 1, medroxy-progesterone acetate (MAP) sponges were inserted for 6, 9 or 13 days in nulliparous ewes. Percentage of ewes in oestrus (92.3, 85.7 and 96.4%, respectively) and conception rates (66.7, 75.0 and 63.0%, respectively) did not differ among groups (T > 0·05). In experiment 2, MAP sponges were inserted for 1, 2, 3, 6 or 12 days in multiparous ewes. Percentages of ewes in oestrus were higher with 3, 6 or 12 days than with 1 or 2 days of priming (72.2, 93.8 and 87.5% v. 25.0 and 33.3% respectively, P < 0.05) and maximum response was with 6-day priming. From both experiments we conclude that short-term progestogen (6 days) priming is as effective as long-term traditional primings for inducing oestrus. In experiment 3, level of progestogen priming was compared among treatments using a new progesterone releasing device (CIDR) for 6 days, a 6-day used CIDR for 6 days, or an 11-day used CIDR for 6 days. While percentages of oestrous response were similar among groups (95.9, 93.6 and 88.9%, respectively), pregnancy rates were higher with a new CIDR than with one that had been used for 11 days (57.1% v. 27.8%, P < 0.05), with the 6-day used CIDR being intermediate (51.1%). We conclude that a 6-day progestogen priming combined with eCG can be used successfully to induce fertile oestrus in seasonal anoestrous ewes if progestogen levels during priming are kept sufficiently high.

No abstract

The present review summarises knowledge of the reproductive response of anoestrous ewes to the introduction of rams - in other words, the ram effect. The ovarian and endocrine response, the factors that determine whether ewes will respond or not (associated with both the stimulus and the receptivity of the ewes) and some aspects of practical management are discussed. Information on the use of the ram effect to stimulate post-partum, prepubertal and cyclic ewes is also given. New insights are provided on ovarian response patterns, including recently collected information on luteal responses. The existence of delayed ovulation (5-7 days after the introduction of the rams) followed by luteal phases of normal or short length, luteal cysts and luteinised follicles is reported after scanning the ovaries with ultrasound. Endocrine parameters for depth of anoestrus, such as LH pulsatility and FSH concentrations, and how the concentrations of these hormones should be considered are discussed. Particular attention is paid to the observation of spontaneous, higher LH pulsatility and higher FSH concentrations in anoestrous ewes that respond to rams with luteal phases than in those that fail to respond. The use of progestogen priming and single progestogen administration and the possible advantages for synchronisation of oestrus are also discussed. Other factors that should be considered before the ram effect is applied, such as the strength of the stimulus and some practical considerations, are also included.

Early weaning is used to advance postpartum ovulation in beef cows, but triggers a stress response, affecting cows' and calves' welfare. Our aim was to compare the response to early weaning in multiparous and primiparous cows. Seventy-one days after birth, calves from 14 primiparous and 11 multiparous cows were weaned. Since birth, cow's body weight (BW), body condition (BC), milk yield and calves' BW were recorded. Basophil/neutrophil relationship, total protein and albumin concentrations were measured before and after weaning. The distance between each cow and its calf before weaning, as well as main behaviors of the cows before and after weaning were recorded using 10 min scan sampling. BW and BC were greater in multiparous than in primiparous cows ( P , 0.0001 for both). There was an interaction between parity ( P 5 0.004) and gender of the calf ( P 5 0.007): both BW and BC were greater in multiparous than primiparous cows, but multiparous cows with male calves had lower BW and BC than those with females ( P , 0.001 for both variables). Milk yield was greater in multiparous than in primiparous cows ( P 5 0.02), and there was an interaction, with greatest milk yield in multiparous cows that calved males ( P 5 0.02). Total protein blood concentration increased with time ( P , 0.0001), similarly in both groups. Albumin concentration profiles were similar despite parity, and decreased since 10 days after weaning ( P , 0.0001). Basophil/neutrophil ratio was not affected by parity, and increased the day of weaning, remaining high until day 10 ( P , 0.05). Frequency of standing decreased during the 2 days after weaning, with a greater decrease in multiparous than in primiparous cows ( P , 0.0001). Pacing increased after weaning ( P 5 0.001), but increased significantly more in multiparous cows ( P 5 0.006), with a significant time after weaning by parity interaction ( P 5 0.01) reflected in greater frequencies in multiparous cows in the 2 days. Walking increased with time ( P , 0.0001), and was more frequent in primiparous cows ( P 5 0.008). Ruminating, which was less frequent in multiparous cows ( P 5 0.014), decreased and remained low during the 3 days following weaning ( P , 0.0001), but there was a significant time by parity interaction ( P , 0.0001). The frequency of vocalizations increased dramatically after weaning ( P , 0.0001), and was greater in multiparous cows ( P 5 0.006), and decreased more slowly during the 2nd and 3rd days after weaning ( P 5 0.005) in these animals. In conclusion, behavioral changes induced by weaning were greater in multiparous than primiparous cows, indicating a more intense response to cow-calf separation in the multiparous animals.