M.A. Brown

Different oilseed supplements alter fatty acid composition of different adipose tissues of adult ewes

Twenty-five mature Small Tail Han ewes were used to investigate the effects of supplemental oilseeds in the diet (sunflower seed, safflower seed, rapeseed, and linseed) on fatty acid composition in different tissues (longissimus lumborum muscle, tail fat, subcutaneous back fat and kidney fat). Averaged over tissue, safflower and sunflower seed was most effective (P<0.05) in enhancing the concentration of conjugated linoleic acid compared to rapeseed, linseed, and control (1.35% and 1.15% vs. 0.80%, 0.80%, and 0.75%, respectively). Linseed supplemented ewes had lesser n-6/n-3 value (2.48, P<0.05) compared to sunflower and safflower supplemented ewes (6.12 and 3.90, respectively). Fatty acid composition for most major fatty acids differed among tissues (P<0.05) but tissue differences varied depending on oilseed supplement (P<0.05). Proportions of conjugated linoleic acid were greatest in tail fat (1.54% vs. 0.82%, 0.79% and 0.70% for kidney, back, and muscle fat, P<0.05) as were total unsaturated fatty acids (49.1% vs. 42.4%, 36.7% and 33.4% for muscle, back, and kidney fat, P<0.05) and tail fat was the most responsive tissue to improvement in fatty acid profile through supplementation. Beneficial fatty acid content of tissues can be increased by oilseed supplementation, but the magnitude of increase varies according to tissue.

The effects of hair density of beef cattle on Haematobia irritans horn fly populations

Abstract We show the relationships that exist between the amount of hair and quantity of sebum on cattle skin and the population density of the horn fly, Haematobia irritans. Brahman and Chianina steers had means of 2390 and 1587 hairs per cm2, respectively, significantly more than the mean number of hairs on Angus, Brahman x Angus Crossbred, Charolais, and Red Poll steers. The Chianina steers had > 30% more sebum present on their skin and hair (0.58g/929cm2) than the Angus, Charolais, and Red Poll steers at the Beef Cattle Research Station Savoy, Arkansas. The Brahman steers had a significantly greater amount of sebum present on the skin (1.51 g/ 929 cm2) than the Crossbred and purebred Angus steers (0.55 and 0.25g/929cm2, respectively) at the South Central Family Farms Research Centre Booneville, Arkansas. The Brahman and Chianina steers had means of 61.9 and 17.0 horn flies per steer, respectively, during the fly season, whereas the Angus, Crossbred, Charolais and Red Poll steers had fly season means that ranged from 76.9 to 265.8 flies per steer. Regression analysis showed that an increase of 100 hairs per cm2, was associated with a reduction of 11 horn flies in the Angus II, 5 in Angus I, 20 in Charolais, 37 in Red Poll, and 0.4 in Chianina steers at the Savoy Station and a reduction of 6.6 horn flies for the Angus, Brahman, and Crossbred steers at the Booneville Centre. Regardless of cattle breed, an increase of 1.0 g of sebum per 929 cm2 output by the steer was associated with 478.5 additional hairs per cm2 on the animal. Each increase of 0.25 g of sebum per 929 cm2 resulted in a decrease of 9.2 horn flies per steer. We conclude that some of the factors responsible for fly‐resistance in cattle are hair density and the corresponding amount of sebum present on cattle skin and hair.

Influence of Live Weight Gain During the Winter Grazing Period on Subsequent Grazing and Feedlot Performance1

Abstract Crossbred steer (n = 297) and heifer (n = 125) calves were used in three experiments to determine the impact of restrictive ADG during the winter grazing period on subsequent BW gains. Calves were born in the spring, weaned in the fall, and transported from Northwest Arkansas (360 km; Experiments 1 and 2) or Southwest Texas (880 km; Experiment 3) to Central Oklahoma for grazing and finishing. Upon arrival, calves were assigned to one of the following treatments: 1) grazing winter wheat pasture, 2) grazing dormant tallgrass native prairie plus supplemental CP, or 3) limit fed a high-energy diet (Experiment 3 only). In March, winter stocker treatments (121 d) were ended, and calves grazed cool season grasses (76 d) until June when the feedlot phase began. In the feedlot phase, calves were either assigned to a conventional total confinement finishing system or to a warm-season grass pasture managed under intensive early stocking (9.9 calves/ha) followed by ad libitum access to a high-energy diet. In Experiments 1 and 2, calves on dormant native pasture gained less (P

Fatty Acid Profile in Milk Fat from Qinghai Plateau Yak at Different Altitudes and Parities1

Qinghai Plateau yak are the most important grazing livestock for milk and beef production on the Qinghai-Tibetan plateau because they are adapted to extremes of cold environment and higher elevation and can be grazed throughout the year. Milk samples (n = 47) from Qinghai Plateau yak cows of different parities and milk samples (n = 6) from Qinghai yellow cattle cows were analyzed using gas chromatography-mass spectrophotometry. Differences in fatty acid profiles of Qinghai Plateau yak milk fat from rangelands at 3 different elevations, at 2 parities, and between species were compared. Additionally, fatty acid profiles of forages from different elevations were analyzed. Fatty acid percentages (g/100 g total fatty acids) in milk fat of Qinghai Plateau yak from different rangelands were largely similar, but there were differences (P < 0.05) in individual fatty acids, including conjugated linoleic acid. There were also elevation differences in fatty acid percentages (e.g., cis-9, cis-12 C18:2 and cis-9, cis-12, cis-15 C18:3; g/100 g total fatty acids) of forage plants. Milk from multiparous Qinghai Plateau yak cows showed greater (P < 0.01) percentages of C18:1 and C18:2, total unsaturated fatty acids, total monounsaturated fatty acids, and total polyunsaturated fatty acids and lesser (P < 0.01) percentages of total saturated fatty acids than primiparous counterparts. The cis-9, trans-11 conjugated linoleic acid isomer percentage in milk fat from multiparous cows was greater (P < 0.01) than from primiparous cows. The study results also suggested that short-chained, medium-chained, and saturated fatty acid percentages of milk fat were greater (P < 0.05) for Qinghai Plateau yak compared with those of Qinghai yellow cattle.

Preweaning Performance of Beefmaster- and Brahman-Sired Calves from Angus and Brahman Cows on Three Forage Systems

Three years of data from 42 purebred Angus (AA) and 50 Brahman (BB) cows bred to purebred Beefmaster (BM) and purebred Brahman (BB) bulls were used to evaluate both breed of sire effects and different forage systems. Cows and calves were managed on one of three forage systems: endophyte-infected tall fescue (E+E+), common bermudagrass and endophyte-infected tall fescue (E+CB), and common bermudagrass and endophyte-free tall fescue (E−CB). Data from 215 calves born and 197 calves weaned were used in this study. The calves were weighed and tagged at birth and were not creep-fed. They were weaned at an average of 195 d of age and their weights and hip heights were taken. There was little evidence of sire breed, forage effects, or interactions of the two on the birthweight of calves from the BM or BB sires, which averaged 39 and 37 kg, respectively. The calves from the AA cows were 7.7 kg heavier at birth than those from the BB cows (P<0.01). There was evidence of a sire breed × dam breed × forage interaction (P<0.10) in calf 205-d weights. There was little evidence of any advantage in 205-d weight for calves on E+CB compared to those on E+E+ except for the BB × BB calves (P<0.10). Only the BB × AA calves seemed to benefit from the E−CB compared to E+CB (P<0.10), and 205-d weights were less for BB × BB calves on E−CB than on E+CB. Averaged over sire breed, the 205-d weights of calves on E−CB exceeded those on E+E+ by 15 kg (P<0.05). Averaged over forages, there was little evidence of differences between BM and BB sires when bred to Angus cows, although predictable decreases in 205-d weights were observed in BM × BB and BB × BB compared to the Angus crosses (P<0.05). The means for hip height averaged over sire and dam breed suggest an advantage for E−CB compared to E+E+ (P<0.10). These data do not suggest any notable advantage for any of the breed groups on any particular forage system. A predictable trend for improved performance as E+ is removed from the forage system is evident as is a similar trend as heterozygosity is increased in the progeny.

Effects of bovine cytochrome P450 single-nucleotide polymorphism, forage type and body condition on production traits in cattle*

Relating single-nucleotide polymorphisms (SNP) to cows with acceptable productivity could benefit cattle breeders in areas where tall fescue is the predominant forage. This study aimed to (i) identify SNPs in bovine cytochrome P450 3A28 (CYP3A28) and (ii) determine the associations between SNP genotype, forage and cow body condition (BC). Genotype (CC, CG or GG) and forage [Kentucky-31 wild-type endophyte-infected tall fescue (KY+) vs. bermudagrass] effects on milk volume and quality were determined in Herd 1 cows (123 cows); in Herd 2 (99 cows), genotype and BC (low vs. moderate) effects on ovarian follicle size, calving date and calving per cent were determined; and in Herd 3 (114 cows), effects of genotype and fescue cultivar [KY+ vs. non-toxic endophyte-infected tall fescue (HiMag4)] were related to calving per cent, calving date and weaning weights of both cow and her calf. A cytosine (C) to guanine (G) transversion at base 994 (C994G) in CYP3A28 was identified. There was a genotype × forage type interaction (p < 0.05) on milk protein in Herd 1 cows; CC cows grazing bermudagrass had greater milk protein percentage in relation to other cows in the herd. In Herd 2, BC and genotype × BC tended (p < 0.10) to influence follicle size and Julian calving date respectively. Diameter of the largest follicle tended to be larger in moderate BC than in low-BC cows; whereas, CC and CG cows in moderate BC and homozygous (CC and GG) cows in low BC tended to calve 14 days earlier in relation to CG cows in low BC. In Herd 3, there was a genotype × forage type interaction (p < 0.05) on calving per cent, Julian calving date and calf weaning weight. In this study, genetic alterations (G allele at C994G) coupled with nutritional factors (low BC and toxic tall fescue) resulted in overall lower productivity in cows.

Preweaning Performance of Calves from Bonsmara, Brangus, Charolais, Gelbvieh, Hereford, and Romosinuano Sires Bred to Brangus Cows Managed on Native Rangeland or Improved Forages1, 2

Abstract Preweaning data on 511 spring-born calves from 187 Brangus cows and 129 Bonsmara, Brangus, Charolais, Gelbvieh, Hereford, and Romosinuano sires were measured over a 4-yr period to determine sire breed, sex, and age of dam differences under 2 preweaning forage environments: 1) native tallgrass rangeland (native) or 2) improved warm-season forages (improved). Sire breed differences in birth weight varied across forage (P

Incidence of Mastitis-Causing Organisms in Angus, Brahman, and Reciprocal-Cross Cows Grazing Endophyte-Infected Tall Fescue or Common Bermudagrass1,2

Angus (A), Brahman (B), and reciprocal cross cows (AB, BA) were sampled in 1994 (67 head) and 1995 (47 head) to evaluate the effect of breed and forage on the presence of mastitis-causing organisms (MCO). In 1994, cows were managed on either endophyte-infected tall fescue (E+) or common bermudagrass (BG) and milk samples were taken in August, September, and October. In 1995, cows were managed on E+, BG, or both forages during the appropriate seasons. Milk samples for 1995 were taken in May, July, and September. In both years, aseptic techniques were used to sample from all four quarters of each cow for diagnostic bacteriology at the Immunology and Disease Resistance Laboratory, Beltsville, MD. Any cow having at least one quarter positive for MCO on a given date was designated positive. In 1994, the percentage of cows with MCO was 52.0, 29.1, 25.4, and 40.0% for A, AB, BA, and B, respectively, averaged over month. Heterosis was estimated as −18.7% (P<0.11) and there was a trend for MCO to be higher on E+ (43.0%) than BG (30.2%). In 1995, the percentage of cows with MCO was 41.8, 40.5, 3.7, and 42.4% for A, AB, BA, and B, respectively, averaged over month. Heterosis averaged −20.0% (P<0.10) and there was a trend for MCO to be higher on E+ (39.1%) than on BG (23.1%) or the E+ and BG combination (34.1%). There was little evidence that presence of MCO affected milk yield or calf preweaning performance. However, there was a negative relationship between milk production or calf preweaning performance and milk somatic cell count. These data suggest that favorable heterosis for absence of MCO is possible and that factors associated with E+ may increase MCO in cows grazing E+. (Key Words: Beef Cattle, Heterosis, Tall Fescue, Bermudagrass, Mastitis.)

Genotype × Environment Interactions in Horn Fly (Diptera:Muscidae) Resistance in Angus, Brahman, and F1 Reciprocal Crossbred Cows on Common Bermudagrass or Endophyte-Infected Tail Fescue1

Weekly horn fly (Diptera:Muscidae) counts were recorded on 125 Angus, Brahman, and F1 reciprocal crossbred heifers grazing endophyte-infected tall fescue or common bermudagrass during the fly seasons in 1990 and 1991. Direct heterosis, maternal breed, and direct breed effects for average fly infestation were estimated as linear contrasts among sire breed × dam breed least squares means in these heifers. Heterosis differed between forages (P<.05) and averaged –16.8 (P<.01) and –.9 (P=.88) flies per head per d on common bermudagrass and tall fescue, respectively. Maternal breed effects were not significant on either forage. Direct breed effects favored the Brahman, were larger on common bermudagrass compared to tall fescue (P<. 10), and averaged –213.0 (P<.01) flies per head per d on common bermudagrass and –167.5 (P<.01) flies per head per d on tall fescue. The results suggested that utilization of heterosis and direct breed effects in Bos indicus × Bos taurus crossbreeding systems was effective in substantially lowering horn fly infestation, but the efficacy of the genetic effects depended on the forage environment.

Relationships of Milk Production of Beef Cows to Postweaning Gain of the Calves12

Milk yield from 158 Brangus cows bred to 6 sire breeds (Bonsmara, Brangus, Charolais, Gelbvieh, Hereford, Romosinuano) was measured for 3 yr to estimate relationships of milk yield of cows and postweaning ADG of their calves on 2 postweaning systems (dry lot or wheat pasture). Milk yield was measured monthly 6 times per year and averaged over 1 mo. Calf postweaning ADG was calculated from the initiation of postweaning management treatments in the fall to the end of spring grazing in April. Calf ADG was regressed on dam 24-h milk yield, and interactions of linear and quadratic regression coefficients with calf sire breed and postweaning treatment of calf were evaluated. In general, regression analyses indicated that calf postweaning ADG was linearly related to dam milk yield, but the relationships depended on the calf sire breed and postweaning treatment (P < 0.01). On dry-lot management, greater cow milk production was associated with lesser postweaning ADG in Gelbvieh- (P < 0.05) and Bonsmara-sired (P < 0.01) calves, whereas greater cow milk production was associated with greater postweaning ADG in Brangus-sired calves (P < 0.01), and a similar trend was observed in Charolais-sired (P < 0.19) calves. On wheat pasture management, greater cow milk production was associated with greater postweaning ADG in Gelbvieh-sired calves (P < 0.11), with a trend for greater cow milk production to be associated with lower postweaning ADG in Romosinuano-sired calves (P < 0.25). Results indicate that accurate determination of the relationship of dam milk production and calf postweaning ADG will require consideration of both calf postweaning management and calf sire breed.