Interaction of breed type and endophyte-infected tall fescue on milk production and quality in beef cattle1

Abstract

Decreased milk production of beef cattle grazing endophyte-infected (EI) tall fescue (TF), an important cool season grass in the southeastern United States, can affect calf growth. The objective was to determine whether a thermal or heat-tolerant Bos taurus breed of cattle, Romosinuano (RO), would tolerate EI TF toxins relative to Angus (AN) cattle. Milk production and quality were examined on AN and RO cows grazing endophyte-free (EF; variety K-31; n = 36) or EI TF (variety K-31; n = 37) along with growth of their Charolais-sired calves in 2007 and 2008 in west central Arkansas. Cows calved between early February and late March (spring). Milk yield and quality, BW, rectal temperature, and serum prolactin were determined at 57.1 +/- 2.6 d postpartum and every 28 d thereafter between April and August. Milk yield was greater in AN compared with RO cows (P < 0.001), but not influenced by forage type (P > 0.88). Percent milk fat was greater in cows grazing EF TF in April, but greater for cows grazing EI TF in July (forage x month, P < 0.001). Percent milk fat was greater for RO than AN cows (P < 0.001). Percent milk protein (P < 0.001) was greater and somatic cell counts (log-transformed; P < 0.001) were less in RO than AN cows. Milk lactose was greater for RO compared with AN cows in June through August (breed x month, P = 0.004). Adjusted weaning BW of calves was similar between EF and EI TF in 2007, but greater for calves from EF than EI TF in 2008 (forage x year, P = 0.03). Rectal temperature was similar between RO cows grazing EF and EI TF, but greater in AN cows grazing EI compared with EF TF in most months (forage x breed x month x year, P < 0.001). Serum prolactin was reduced in both breeds of cows grazing EI TF between April and July of both years and greatest in RO cows grazing EF TF (breed, P < 0.001; forage x month, P < 0.001). These data suggest that RO cows were more thermal-tolerant, but still susceptible to toxins in EI TF as shown by a reduction in serum concentrations of prolactin. However, milk production was not influenced by EI TF as previously observed, but milk fat percent was decreased in early lactation in this group of cows. Milk yield and quality were different between AN and RO cows during the period of lactation observed.

Genetic effects for reproductive performance of straightbred and crossbred Romosinuano and Angus cows in a temperate zone

“…Such a notion, though not well supported, is intriguing given the background of the research Angus herd in Florida (Riley et al, 2007(Riley et al, , 2011(Riley et al, , 2014. In a subset of the purebred Angus and Romosinuano cows in this study, the Angus cows appeared to be more susceptible to the toxins in the tall fescue and heat stress during summer months than the Romosinuano cows (Burke et al, 2010). In addition, serum concentrations of prolactin were greater in Romosinuano than Angus cows.…”

“…Only straightbred cows were removed for inferior maternal performance, almost all of which were Romosinuano; those all had at least one reproductive failure. Burke et al (2010) observed lower milk production of Romosinuano relative to Angus.…”

“…pastures each year before the breeding season, and remained in pasture with that forage until the random assignment in the following year. In 2007 and 2008, subsets of cows were assigned to trials associated with the two types of tall fescue as treatments (Burke et al, 2010). Pasture fertilization for tall fescue (Burke et al, 2010) and bermudagrass (Brown et al, 1993) was described previously; the latter authors described the soil types.…”

“…In 2007 and 2008, subsets of cows were assigned to trials associated with the two types of tall fescue as treatments (Burke et al, 2010). Pasture fertilization for tall fescue (Burke et al, 2010) and bermudagrass (Brown et al, 1993) was described previously; the latter authors described the soil types. Stocking rate was 1.25 cows or cow-calf pairs/ha; tall fescue paddocks were 16 or 24 ha and bermudagrass paddocks were 16 ha.…”

“…Heterosis expressed by Criollo crossbred cattle for reproduction was characterized in tropical or subtropical regions (Vergara et al, 2009;Riley et al, 2014), but has been investigated to only a limited extent in a temperate zone of the world (Corva et al, 1995), and the productivity of Criollo cattle on a harsh forage such as fescue has been characterized minimally (characteristics of milk; Burke et al, 2010). The objectives of this work were to: (1) estimate heterosis and breed direct effects for cow reproduction traits, (2) assess the effects of the type of forage grazed during the breeding season on those traits and on the estimates of heterosis and breed effects, and (3) characterize calf loss and cow removal by breed type.…”