Effect of Feeding Level Pre- and Post-Puberty and Body Weight at First Calving on Growth, Milk Production, and Fertility in Grazing Dairy Cows

• Published in: Journal of dairy science 2005-09, Vol.88 (9), p.3363-3375
• Main Authors: Macdonald, K.A., Penno, J.W., Bryant, A.M., Roche, J.R.
• Format: Article
• Language: English
• Subjects: Animal productions; Animals; Biological and medical sciences; Body Composition; Body Weight; Breeding; Cattle - growth & development; Cattle - physiology; Dairy cattle; Diet; Energy Intake; Female; Fertility; Fertility - physiology; Food industries; Fundamental and applied biological sciences. Psychology; Health Status; heifer; Lactation - physiology; Lolium; Milk and cheese industries. Ice creams; Milk production; pasture; Poaceae; Pregnancy; Reproduction; Sexual Maturation; Terrestrial animal productions; Trifolium; Vertebrates
• ISSN: 0022-0302; 1525-3198
• DOI: 10.3168/jds.S0022-0302(05)73020-4

The effect of feeding to achieve differential growth rates in Holstein-Friesian (HF; n=259) and Jersey (n=430) heifers on time to puberty and first lactation milk production was investigated in a 3×2 factorial design. Holstein-Friesian and Jersey calves were reared to achieve a BW of 100 and 80kg, respectively, at 100 d. At target weight, all calves were randomly allocated to one of 3 feeding treatments to achieve different growth rates. Holstein-Friesian and Jersey calves were fed fresh pasture to achieve average daily growth rates of 0.77, 0.53, or 0.37kg of BW/d (HF) and 0.61, 0.48, or 0.30kg of BW/d (Jersey), respectively. Period 1 (prepubertal) was imposed until HF and Jersey treatment groups averaged 200 and 165kg of BW, respectively. Following period 1, HF and Jersey calves from each treatment group were randomly allocated to one of 2 feeding treatments to achieve average daily growth rates of 0.69 or 0.49kg of BW/d (HF) and 0.58 and 0.43kg of BW/d (Jersey), respectively. Period 2 (postpubertal) was imposed until 22 mo, when heifers were returned to their farms of origin. Body weight, body condition score, height, heart girth circumference (HGC), milk production, and fertility-related data were collected until the end of the third lactation. Time to reach puberty was negatively associated with level of feeding, and heifers attained puberty at the same BW (251±25.4 and 180±24.0kg for HF and Jersey heifers, respectively). Heifers on high feed allowances during periods 1 and 2 were heavier, taller, and had greater HGC than their slower grown counterparts until 39 mo of age when height and HGC measurements stopped. Body weight differences remained until 51 mo, when measurements ceased. High feed allowance during period 1 (prepubertal) did not affect milk production during the first 2 lactations, but did reduce milk production in lactation 3. It is possible that the expected negative effect of accelerated pre-pubertal growth was masked by greater calving BW, as BW-corrected milk yield declined in both breeds with increasing prepubertal feed allowance. Growth rate during period 2 was positively correlated with first lactation milk production. Milk yield increased 7% in first lactation heifers on the high feed allowance, which resulted in higher growth rate during period 2. Milk production during subsequent lactations was not affected. Results suggest that accelerated prepubertal growth may reduce mammary development in grazing dairy cows, but this does no