Effect of Nursing Management and Skeletal Size at Weaning on Puberty, Skeletal Growth Rate, and Milk Production During First Lactation of Dairy Heifers

Abstract

Forty Israeli-Holstein 5-d-old calves were used to determine the effect of increasing calf body weight (BW) and skeletal size during the nursing period on age and skeletal size at puberty and on skeletal size and performance during first lactation. The calves were randomly allotted to 2 experimental groups as follows: milk replacer (MR) [calves were given 0.450 kg/d dry matter of milk replacer for the first 50 d of life] and milk-fed (MF) [calves had free access to milk in two 30-min meals/d]. From weaning to 180 d of age, all calves were fed the same diet. At 180 d of age, the MR and MF calves were each divided into 2 equal subgroups: one subgroup from each treatment was given only growing ration, and the other was given the same ration supplemented with fish meal to supply 2% crude protein (CP) (treatments MR + CP and MF + CP, respectively). Finally, at 270 d of age, all calves were housed together and fed a growing heifer's ration until first calving. During the entire nursing period, the MF calves consumed 9.8% more DM, 39.7% more CP, and 52.4% more metabolizable energy than the MR calves. At 60 d of age, BW and all skeletal parameters were higher in the MF calves than in the MR calves. During the entire rearing period (60 to 550 d), the average BW of the MF calves was greater by 16 kg than the BW of the MR calves. Nursing management did not affect differences in skeletal parameters at calving. Average age at puberty onset was 272 +/- 26.8 d; MF calves reached puberty 23 d earlier than MR calves. Yields of milk (kg/305 d) and fat-corrected milk (FCM, kg/d) were greater for the MF + CP heifers than for the MR heifers. It was concluded that nursing by ad libitum milk, as compared with milk replacer, affected BW but not skeletal size of the adult animal, decreased age of puberty onset, and increased FCM yield at first lactation. Supplementing the diet with 2% CP during the prepubertal period increased BW but not skeletal size of the adult animal and 305-d milk and FCM yields during first lactation.

Effects of feeding level and protein content of milk replacer on the performance of dairy herd replacements

“…Skeletal measurements and body condition score changes suggest that the live weight differences resulted from the enhanced deposition of both lean tissue and fat. Shamay et al (2005) found that differences in skeletal size that occurred during the preweaning phase disappeared post weaning. This observation was supported by results from the current study in which calves offered higher levels of MR were significantly larger in size at weaning, only for these differences to disappear shortly after weaning.…”

“…Long-term effects of pre-weaning nutrition Bar-Peled et al (1997), Shamay et al (2005), Moallem et al (2006) and Drackley et al (2007) all found a positive relationship between level of nutrition in early life and subsequent milk production. Additionally, Shamay et al (2005) reported a 23-day reduction in age at puberty and Bar-Peled et al (1997) demonstrated a 31-day reduction in first-calving age when heifer calves were offered a higher feed level up to weaning.…”

“…Additionally, Shamay et al (2005) reported a 23-day reduction in age at puberty and Bar-Peled et al (1997) demonstrated a 31-day reduction in first-calving age when heifer calves were offered a higher feed level up to weaning. However, many of these studies had confounding factors in their design.…”

“…However, many of these studies had confounding factors in their design. For example, level of feeding was confounded by feeding method in the study by Bar-Peled et al (1997) and by feed type (whole milk v. MR) in the studies by Shamay et al (2005) and Moallem et al (2006). Drackley et al (2007) demonstrated elevated milk and milk protein yields but similar milk fat yields in replacement heifers reared on an accelerated-growth regime, compared with a conventional limited-feed regime.…”

“…Studies that have examined the long-term effects of levels of pre-weaning nutrition on the performance of dairy herd replacements have frequently had confounding factors in their design. For example, level of feeding was confounded by differences in feeding method in the study by Bar-Peled et al (1997) and by differences in feed type (whole milk compared with MR) in that by Shamay et al (2005), while Blome et al (2003) and Brown et al (2005) used calves with a starting age of 2 to 3 weeks.…”