Effects of feeding level before and after calving, and restricted suckling frequency on postpartum reproductive and productive performance of Sarda and Charolais X Sarda beef cows

Two experiments were carried out on 48 Sarda (Sa) and 48 Charolais x Sarda (F1) grazing cows using a factorial design: 2 genotypes x 2 feeding levels targeted to low (2, L) and high (3, H) body condition scores (BCS) at calving and in the following 3 months x 2 suckling frequencies. These were ad libitum suckling (ADLIB) versus restricted (RESTR) to one suckling per day (45-90 days postpartum) in experiment 1 and ad libitum suckling (ADLIB) versus isolated (ISOL, one suckling daily between days 25 and 50 with no visual or auditory contacts between dams and calves outside the daily suckling period) in experiment 2. In experiment 1 postpartum anoestrus interval (PPI) was shorter in SaL than in F1L cows (P < 0.01). In experiment 2 BCS around calving exerted an overriding effect on PPI; Sa cows tended (P < 0.08) towards shorter PPI than F1 cows. Conception rate (CR) was higher in the 4th month postpartum in SaL than in F1L cows in experiment 1 (95 vs. 57%, P < 0.01) and in H than in L cows (58 vs. 14%, P < 0.001) in experiment 2. Suckling frequency affected CR of F1 cows by the 8th month postpartum in experiment 2: it was 90% in F1 ISOL cows and just 55% in F1 ADLIB cows (P < 0.02). It is concluded that in the less favoured areas of Sardinia, the Sarda breed gives better reproductive performance than F1 cows while maintained at low BCS during the calving period. Cross-bred, but not pure Sarda cows, can benefit from the implementation of suckling restriction with strict calf isolation. (C) 2002 Elsevier Science B.V. All rights reserved.