Production response of multiparous Holstein cows treated with bovine somatotropin and fed diets enriched with n-3 or n-6 fatty acids

Abstract

Multiparous cows (n = 59) were blocked by expected calving date and previous milk yield and assigned randomly to treatments to determine the effects of bovine somatotropin (bST; Posilac, Monsanto Animal Agricultural Group, St. Louis, MO) and source of dietary fat on production responses. Diets were provided from calving and included whole, high-oil sunflower seeds [SS; 10% of dietary dry matter (DM); n-6:n-3 ratio of 4.6] as a source of linoleic acid (18:2) or a mixture of Alifet-High Energy and Alifet-Repro (AF; Alifet USA, Cincinnati, OH; 3.5 and 1.5% of dietary DM, respectively; n-6/n-3 ratio of 2.6) as a source of protected n-3 fatty acids. Diets contained 181 versus 188 g of crude protein and 183 versus 186 g of acid detergent fiber/kg of DM and 1.54 versus 1.66 Mcal of net energy for lactation at the actual DM intake for SS versus AF, respectively. Cows received 0 or 500 mg of bST every 10 d from 12 to 70 d in milk (DIM) and at 14-d intervals through 280 DIM. The 2 x 2 factorial combination of diet (SS or AF) with or without bST administration resulted in treatments designated as SSY, SSN, AFY, and AFN, respectively. Data were analyzed as repeated measures using mixed model procedures to determine the effects of diet, bST, and their interactions. Yield of 3.5% fat-corrected milk was not altered by diet, but was increased by 4.0 +/- 1.9 kg/d from 12 to 70 DIM and by 5.1 +/- 1.2 kg/d from 12 to 280 DIM by bST. Treatment did not affect DM intake or energy balance (EB) nadir. There was an interaction of bST and diet on EB because AF decreased the impact of bST on overall EB and allowed AFY cows to reach a positive EB earlier than SSY cows. Gross feed efficiency adjusted for body weight change was greater for bST-treated cows (1.03 vs. 1.15 +/- 0.03 kg of fat-corrected milk/Mcal of net energy for lactation). Circulating insulin-like growth factor-I concentrations were increased by bST (85 vs. 125 +/- 8 ng/mL). Body weight, body condition score, and backfat thickness were reduced by bST, but differences between treated and nontreated cows did not differ by 280 DIM. Results indicate cows responded to bST administration in early lactation, but the magnitude of the response was greater after 70 DIM. Source of dietary fat had a minimal effect on most production measurements, but relative to SS, AF decreased the impact of bST on overall EB. Results support the premise that bST administration prolongs the delay in postpartum tissue replenishment.

Fatty acid composition of milk from multiparous Holstein cows treated with bovine somatotropin and fed n-3 fatty acids in early lactation

“…diet, bST, and WOL was DHA (P = 0.028), which was not altered by WOL in cows fed SS and increased at 8 and 20 WOL in AFN and AFY cows, respectively. Yield of 3.5% FCM (41.7, 48.0, 43.3, and 47.2 kg/d for SSN, SSY, AFN, and AFY, respectively) was increased (P = 0.001) by bST, and this effect became more apparent (P = 0.019) as lactation progressed (Carriquiry et al, 2009). There were no effects or interaction of diet × bST administration on milk fat content (3.89, 4.22, 4.12, and 4.19% for SSN, SSY, AFN, and AFY, respectively; Carriquiry et al, 2009).…”

“…Diets were designed to differ only in the type of fatty acids they contained and were formulated to contain similar amounts of NE L (1.68 and 1.71 Mcal/kg, respectively) at a predicted peak DMI of 29.9 kg/d (4.7× maintenance; NRC, 2001), but NE L-Actual DMI values throughout the study were 1.54 and 1.66 Mcal/kg for SS and AF, respectively. Dietary content of all other major components differed by less than 4% between diets (Carriquiry et al, 2009).…”

“…Detailed descriptions of the diets, animal management, data and sample collection and analyses, and production responses have been reported (Carriquiry et al, 2009). Briefly, multiparous cows (n = 59) were fed the same dry cow diet beginning 3 wk before their expected calving date.…”

Evolutionary process of Bos taurus cattle in favourable versus unfavourable environments and its implications for genetic selection

“…1997; Galyean and Rivera 2003; McConnel et al. 2007; Carriquiry et al. 2009; Marcillac‐Embertson et al.…”

Effect of prepartum somatotropin injection in late-pregnant Holstein heifers on metabolism, milk production and postpartum resumption of ovulation

“…Somatotropin has direct effects on the partitioning of nutrients to target tissues (Bauman and Vernon, 1993), as well as indirect effects expressed in the mammary gland and other tissues that are mediated by IGF-I (Jones and Clemmons, 1995). In this regard, somatotropin injection during the peripartum period is able to increase serum IGF-I concentration and milk production (Putnam et al, 1999;Gulay et al, 2004;Carriquiry et al, 2009b). In addition, injection of somatotropin exclusively in the prepartum period can also lead to increased dry matter intake (DMI) in the early postpartum period (Putnam et al, 1999).…”