A comparative study of three growth profiles during rearing in dairy heifers: Effect of feeding intensity during two successive winters on performances and longevity

An experiment was performed on 128 heifers (79 Holstein and 49 Normande heifers) born during four successive winters (1989-1992) and aimed at studying the effect of limiting average daily live weight gain (ADG) during two successive winters on performance and longevity when heifers first calved at 36 months of age. At the beginning of second (300-430 d of age on average) and third winter (660-780 d of age on average), animals were housed and subject to a feeding strategy aimed at reaching ADG of 800 (H), 600 (M) or 400 (L) g/d. ADGs observed were close to those expected. During pasture seasons, management and feeding were similar for all animals and treatments. During the second grazing season that followed the first winter treatment, ADG was 480, 569 and 723 g/d for H, M and L heifers, respectively. During the third grazing season, it was similar for M and L heifers (826 and 838 g/d, respectively) but significantly lower for H heifers (670 g/d). Body weight and wither height significantly differed between treatments at several growth stages. Overall fertility in heifers was not affected significantly by treatments, but the percentage of pregnant heifers after one artificial insemination was 53, 69 and 74% in L, M and H groups, respectively. No significant difference was noted thereafter. L and M cows produced significantly less milk on a 305-d basis per lactation (-250 kg on average) than H cows, with no difference in protein production. Lactation performance was not affected by feeding treatment during the first lactation, but for parities higher than two, milk yield calculated on a 305-d basis differed significantly, with H cows producing more milk (+250 kg or more) and more fat and protein (+10 kg or more). Of the 128 animals that started the experiment, nearly half of them (46%) were culled because of reproductive problems. This was probably due to seasonal calving strategy that required compacted calving period (three months). Less than 25% of L heifers started a third lactation, whereas more than 30% of H and M heifers completed their fourth lactation. Overall, most parameters were affected by breed: Holstein cows produced more 4%-fat-corrected milk and 305-d milk (+1600 kg), with more protein (+58 kg) and fat (+38 kg). These results indicated that in a seasonal 36 months of age first calving system, feed restriction for heifers during two successive winters have short-term effects (e.g., on fertility) but also long-term effects (e.g., lactation performances and longevity). (C) 2009 Elsevier B.V. All rights reserved.