Somatotropic axis components and nutrient partitioning in genetically diverse dairy cows managed under different feed allowances in a pasture system

Abstract

The somatotropic axis [including growth hormone (GH), GH receptor, and insulin-like growth factor (IGF)-I] is uncoupled in high-producing cows in early lactation so that the liver fails to respond to GH and produces less IGF-I. This uncoupling was implicated in the process of nutrient partitioning, enabling high milk production. Different genetic selection goals may affect functional components of the somatotropic axis. Thus, the somatotropic axis was examined in diverse genetic strains of dairy cows [North American Holstein 1990 (NA90), New Zealand Holstein-Friesian 1990 (NZ90), and New Zealand Holstein-Friesian 1970 (NZ70)] that were managed similarly within a pasture-based system but were offered feed allowances commensurate with their genetic ability to produce milk. The NA90 cows produced more milk (26.2 +/- 0.3, 24.1 +/- 0.3, and 20.1 +/- 0.4 kg/d, for NA90, NZ90, and NZ70, respectively), but had lower milk fat percentages (4.28 +/- 0.03, 4.69 +/- 0.03, and 4.58 +/- 0.04 kg/d for NA90, NZ90, and NZ70, respectively) compared with both NZ strains. Milk protein percentages (3.38 +/- 0.02, 3.52 +/- 0.02, and 3.29 +/- 0.03 kg/d for NA90, NZ90, and NZ70, respectively) were greater for NZ90 cows. During early lactation (wk 2 to 6), the total net energy produced in milk was greater in NA90 compared with NZ90 or NZ70 cows, but total net energy in milk after wk 6 was equivalent for NA90 and NZ90 cows. The greater milk production in early lactation in NA90 cows was associated with lower body condition scores (BCS; 1 to 10 scale; 4.0 +/- 0.1) elevated blood GH concentrations (1.6 +/- 0.1 ng/mL), and low blood IGF-I concentrations (14.8 +/- 1.1 ng/mL), indicating an uncoupled somatotropic axis. In comparison, the NZ70 cows retained a coupled somatotropic axis during early lactation, maintaining greater BCS (4.6 +/- 0.1), lower blood GH (0.7 +/- 0.1 ng/mL), and greater blood IGF-I (21.9 +/- 1.2 ng/mL). The degree of uncoupling in NZ90 cows was intermediate between the other 2 strains. Additional feed allowance failed to change blood IGF-I concentrations in NA90 cows but increased IGF-I concentrations in NZ90 cows (20.9 +/- 1.4 and 13.2 +/- 1.4 ng/mL for the high and low feed allowance, respectively). Furthermore, additional feed allowance in NZ90 cows lessened BCS loss in early lactation, but did not affect BCS loss in NA90 cows. Functional components of the somatotropic axis differed for the respective strains and were consistent with strain differences in milk production, BCS, and feed allowance.

Effects of herbage allowance of native grasslands in purebred and crossbred beef cows: metabolic, endocrine and hepatic gene expression profiles through the gestation–lactation cycle

“…In agreement with our results, the expression of GHR, GHR-1A and IGF1 mRNA did not change during the peripartum or early lactation period in beef cows (Jiang et al, 2005; Laporta, Astessiano, López-Mazz, Soca, Espasandin and Carriquiry Schneider et al, 2010) or during the transition period of low milk-producing (20 kg/day) dairy cows (Lucy et al, 2009). In the present study, milk yield level (4 to 5 kg/day) was in agreement with previous reports of milk production in a similar environment (Quintans et al, 2010) and with CR daughters of low milk-expected progeny difference A and H bulls (Minick et al, 2001).…”

Advances in predicting nutrient partitioning in the dairy cow: recognizing the central role of genotype and its expression through time

“…The difference in body condition score loss between high and low feeding regimes was also greater for Holstein cows . Similarly, significant differences in nutrient partitioning were found in a trial comparing two New Zealand strains (1970 and 1990 genetics) and a North American (1990) strain of Holstein-Friesian (Lucy et al, 2009). In this study, the North American strain produced more milk and mobilized more body reserves than the New Zealand 90 strain, which performed better than the New Zealand 70 strain.…”

“…In recent years, a significant number of breed, strain and selection line comparisons have shown clear differences in patterns of milk production and body reserve usage (Horan et al, 2005;Dillon et al, 2006;Roche et al, 2006;Yan et al, 2006;Cutullic et al, 2009;Delaby et al, 2009;Olson et al, 2010). Underlying these differences in performance are different patterns of endocrine profiles (Drackley et al, 2001;Gong et al, 2002;Lucy et al, 2009). Clearly, these differences are underpinned by differences in gene expression and enzyme profiles (Loor et al, 2006;Sumner-Thomson et al, 2011).…”

Nutritional sub-fertility in the dairy cow: towards improved reproductive management through a better biological understanding

“…Lipid re-esterification rates show the opposite pattern through lactation (Chilliard et al, 2000). These patterns are underpinned by the homeorhetic changes in the somatotropic axis (Etherton and Bauman, 1998;Lucy et al, 2009) interacting with the homoeostatic regulation of energy metabolites, primarily through insulin (Bauman, 2000). Leptin and other signalling molecules are also implicated (Ingvartsen and Boisclair, 2001;Vernon et al, 2001).…”