Restricted Cows Research Articles

Liquid supplement and forage intake by range beef cows.

One hundred eighty crossbred cows were assigned to one of six native range pastures during two winters to evaluate forage and supplement intake as affected by liquid supplement (yr 1: 50% crude protein, 84% from urea; yr 2: 57% crude protein, 91% from urea) delivery method and cow age (2, 3, 4, 5, or 6 yr). Treatments were: 1) no supplement (Control); 2) a lick-wheel feeder containing liquid supplement (ADLIB); and 3) a computer-controlled lick-wheel feeder that dispensed 0.9 kg x cow(-1) x d(-1) of liquid supplement (average 0.5 kg of dry matter x cow(-1) x d(-1); Restricted). Each treatment was applied to two pastures. Forage digestibility was increased (P = 0.03) by supplementation. Supplemented cows lost less (P = 0.05) body condition than unsupplemented cows (average -0.3 vs -0.6). Blood urea nitrogen (BUN) was highest (P = 0.001) for ADLIB (8.7 mg/dL), intermediate for Restricted (6.2 mg/dL), and lowest for Control (2.3 mg/dL). Forage DMI was 31% higher (P = 0.01) in 1995 than in 1996, and was increased (P = 0.02) by supplementation both years. Cows supplemented with ADLIB consumed 23% more forage dry matter than Control cows, whereas Restricted cows consumed 21% more dry matter than ADLIB cows. Supplement intake by cows on ADLIB was greater (P = 0.001) than by cows on Restricted in both years. Supplement intake was lowest (P = 0.002) by 2-yr-old cows, intermediate by 3-yr-olds, and greatest by 4-, 5-, and 6-yr-old cows. Variation in supplement intake by individual cows was higher (P = 0.09) for cows in the Restricted treatment (coefficient of variation [CV] = 117%) than those on ADLIB (CV = 68%) during the first year, but did not differ between supplement treatments (average CV = 62%) in the second year. The proportions of cows consuming less than 0.3 kg/d of supplement dry matter intake (DMI) and consuming less than the target amount of supplement (0.5 kg DMI) were less (P = 0.001) for ADLIB than for Restricted during both years. ADLIB cows spent more (P = 0.001) time at the supplement feeder and had more (P < 0.002) supplement feeding bouts than Restricted cows during both years. During the first year, 2- and 3-yr-old cows spent less (P < 0.01) time at the feeder and had fewer feeding bouts per day than 6-yr-old cows. Age had no effect (P > 0.24) on feeding behavior during the second year. Supplementation of beef cows grazing winter range with 50 to 57% crude protein liquid supplement increased forage digestibility and intake. Restricting supplement access increased forage consumption and variability of supplement intake.

Effect of dietary intake on steroid feedback on release of luteinizing hormone in ovariectomized cows.

This study tested the hypothesis that the decline in pulsatile release of luteinizing hormone (LH), resulting from steroid negative feedback, is greater in animals fed a low, compared with a high, plane of nutrition. Two-year-old cows were ovariectomized and six days later were fed diets to provide 1.5 x maintenance requirements (n = 6, supplemented) or 0.5 x maintenance requirements (n = 6, restricted) (Round 1). Pulsatile release of LH was measured over a 14-h period on the fifth day of feeding these diets (Day 1); at 6 h, all animals were treated with an intravaginal insert containing 1.38 g progesterone, which remained in place until the end of Day 3. Pulsatile release of LH was again measured for 14 h on Day 3; at 6 h, all animals were injected intramuscularly with oestradiol benzoate (ODB; 1 mg per 500 kg live weight). Three days later, this protocol was repeated, in a cross-over design, with cows that were previously restricted now being supplemented and those cows previously supplemented, now restricted (Round 2). Plasma concentrations of progesterone after intravaginal progesterone treatment were 1.01 ng mL(-1) higher in restricted cows compared with supplemented cows (P < 0.001) and were also higher in Round 1 than in Round 2 and on Day 1 than on Day 3 (P < 0.001). Plasma concentrations of oestradiol following injection with ODB did not differ between supplemented and restricted cows (P > 0.1). Dietary intake did not affect mean concentrations of LH, pulse frequency or amplitude during the 6-h period before steroid treatment or the change in these variables following steroid treatment; however, the slope of the decline in concentrations of LH following progesterone treatment was significantly more negative in cows fed restricted diets compared with those fed supplemented diets. In Round 2, mean concentrations of LH were higher preceding, and decreased more following, progesterone treatment compared with the decrease after ODB treatment. In conclusion, acute dietary restriction resulted in a more rapid decline in the release of LH following treatment with intravaginal progesterone, and was associated with higher concentrations of progesterone in plasma.

Effects of level of feeding and progesterone dose on plasma and faecal progesterone in ovariectomised cows

The effects of two levels of feeding and two doses of progesterone (P4) on plasma and faecal progesterone metabolites (FP4M) were studied using a total of 24 ovariectomised (OVX), non-lactating, Holstein–Friesian cows. Cows were grazed on improved ryegrass/white clover pastures and allowed ad libitum access to pasture or were restricted to grazing for a total of 4 h per day in two 2 h periods. Progesterone (P4) was administered as one or two, simultaneous, intravaginal progesterone devices (CIDR). The cows were adapted to their pasture supply for 2 weeks before the start of the progesterone treatments. The progesterone devices were administered for 11 days and the cows were dosed with slow release chromic oxide capsules during the P4 treatment to allow faecal output (FO) to be estimated. Daily blood samples for P4 assay and weekly samples for blood metabolite assay were collected. Faecal samples were collected per rectum daily and assayed for pregnanes containing a 20-oxo-, 20α- or a 20β-OH group by enzyme immunoassay (EIA). Daily FO was higher ( P<0.001) for ad libitum than pasture restricted cows (6.3 vs 4.1 kg DM) but was similar for both doses of P4. The average mass of P4 released from a CIDR device over a 11-day period was higher for cows allowed ad libitum pasture compared with those on restricted pasture (0.64 vs 0.60 g; P=0.04). Plasma P4 concentrations, however, were higher in restricted than ad libitum fed cows (1× CIDR: 1.81 vs 1.41 ng/ml; 2× CIDR: 4.10 vs 3.46 ng/ml). Increasing the progesterone dose significantly ( P<0.001) increased both the concentrations and daily totals of the faecal pregnanes assayed and total FP4M. Restricted pasture cows had higher ( P<0.001) pregnanes and FP4M concentrations than cows fed ad libitum. Daily total faecal pregnane and FP4M did not differ between feeding levels except for faecal 20α-pregnane which was highest for ad libitum fed cows ( P<0.05). These results showed that the plasma concentrations of P4 in CIDR-treated OVX cows were negatively associated with the level of feeding. Level of feeding and dose of P4 affected the concentrations of FP4M, but the daily excretion rate of FP4M was not positively influenced by the level of feeding.

Etiology of Fatty Liver in Dairy Cattle: Effects of Nutritional and Hormonal Status on Hepatic Microsomal Triglyceride Transfer Protein

We conducted three experiments to determine the effects of nutritional and hormonal status on microsomal triglyceride transfer protein (MTP) activity and mass. In experiment 1, 18 nonlactating Holstein cows, 75 d before expected calving date, in their second gestation or greater were monitored from d 75 to 55 prepartum. Cows were fed a control diet from d 75 to 62 prepartum for covariable measurements. From d 61 to 55 prepartum, six cows continued to receive the control diet, six cows were restricted to 2.3kg of grass hay/d, and six cows were fed the control diet plus 1.8kg of concentrate/ d and 500ml of propylene glycol given 2 times/d as an oral drench. Plasma glucose and serum insulin concentrations were highest in cows that received propylene glycol and lowest in feed restricted cows. Plasma nonesterified fatty acids (NEFA) and liver triglyceride (TG) concentrations were highest in feed restricted cows and not different between cows that received the control diet and cows that received propylene glycol. Hepatic MTP activity and mass were not affected by treatment in experiment 1. In experiment 2, bovine hepatocytes isolated from the caudate process of five preruminating Holstein bull calves were incubated with either 0, 0.5, 1.0, or 2.0mM NEFA for 48h. Intracellular TG increased linearly as NEFA concentration in the media increased. Concentration of NEFA in the incubation media had no effect on MTP activity or mass. There was a quadratic effect of concentration of NEFA in the incubation media on MTP mRNA. In experiment 3, bovine hepatocytes isolated from the caudate process of five preruminating Holstein bull calves were incubated with 2mM [1–14C]oleate for 24h to accumulate TG, followed by a 36-h period of TG depletion, during which hepatocytes were incubated with no hormone, 10 nM insulin, or 10 nM glucagon. There was no effect of insulin or glucagon on intracellular TG, MTP activity or mass. Cells incubated with no hormone had higher levels of MTP mRNA compared to cells incubated with insulin or glucagon during the depletion period. Results suggest that hepatic MTP mRNA may be affected by TG accumulation, insulin, and glucagon in vitro. However, hepatic MTP activity and mass are not affected by nutritional status of nonlactating dairy cows, TG accumulation in vitro, or insulin and glucagon in vitro.

Influence of pasture allowance on the composition and cheese-yielding potential of milk.

Effects of pasture allowance on the yield, composition and cheese-yielding potential of milk were investigated using 48 Friesian cows in crossover experiments during spring (~60 days after calving) and summer (~180 days after calving). All cows were subjected to two nutritional treatments: ad lib. grazing (pasture allowance &gt;45 kg DM/cow/day) and restricted grazing (16-18 kg DM/cow/day). Milk samples were collected from each cow on the final day of each treatment period and analysed for a range of components. Pasture dry matter intakes (DMI) during treatment periods were determined using the n-alkane technique. Increasing pasture allowance resulted in increased DMI. Cows grazing ad lib. had higher milk yields, concentrations of protein (spring only), casein, whey protein (spring only), casein:whey protein ratio (summer only), α-casein, β-casein and urea, but lower concentrations of serum albumin and immunoglobulin, than cows grazing a restricted pasture allowance. Nutritional effects on milk composition were greatest in spring, at which time theoretical Cheddar cheese yields were greater for milk from cows grazing ad lib. than restricted cows. Concentrations of some milk components were correlated with DMI of cows. These results provide evidence that on-farm management practices can affect milk composition and the potential yield of dairy products. Maintaining an adequate pasture allowance for dairy cows is important not only to maximise milk production, but also to optimise the manufacturing potential of milk. Keywords: casein, cheese, milk, pasture allowance, protein

The effects of pre- and early post-calving management on reproductive performance of beef cows

One hundred and thirty-four pregnant beef cows (liveweight = 544.3 kg ± 73 3 kg SD; condition score = 3.5 ± 0.3 SD), were randomly assigned in January to five management treatments (combinations of feed restriction and weaning time) to study the effects on calving and rebreeding performance. Twenty-seven were feed-restricted (54.7 MJ DE d−1) for the last 3 mo of pregnancy then realimented (3REST); their calves were weaned in October. Thirty were feed-restricted for the last 3 mo of pregnancy (54.7 MJ DE d−1) and the first 2 mo of lactation (99.6 MJ DE d−1), then their calves were weaned and turned out to graze in June (5REST). The remaining 77 cows (UNREST) were supplemented on range with 153.5 MJ DE d−1 from January until calving. Their calves were weaned in either August (one group of 26 calves directly into a feedlot, a second group of 26 onto unsupplemented range) or October (25 calves directly into a feedlot). All cows grazed together on the range from June onwards. After calving, the restricted (3REST and 5REST) cows were significantly lighter (464.4 and 469.5 kg vs. 506.9 kg) and thinner (condition scores 2.5 and 2.6 vs. 3.0) than the UNREST cows, but the percentage of cows calving calf mortality, assisted births calving dates, udder scores and mean birth weight of calves were not affected (P &gt; 0.05) by pre-calving nutrition. Catch-up growth was evident in both the 3REST and 5REST cows once exposed to higher energy feeding. There were no significant effects (P &gt; 0.05) of the management (nutrition and weaning) treatments on the following year s breeding and calving performance. It is concluded that the combinations of nutrition and weaning used in this study did not necessarily impair calving or rebreeding performance of beef cows, which calved in condition score 2.5 or above. Key words: Beef cows, feed restriction, reproduction, condition score, rebreeding, birthweight

Influence of diet and ambient temperature on bovine serum insulin-like growth factor-I and thyroxine: relationships with non-esterified fatty acids, glucose, insulin, luteinizing hormone and progesterone

Multiparous, nonlactating, Hereford cows were fed maintenance (M; n = 11) or restricted (R; n = 11) diets for 41 weeks to evaluate changes in insulin-like growth factor-I (IGF-I) and thyroxine during the onset of nutritionally induced anoestrus and during realimentation. Cows had a moderate body condition score (BCS = 5.5 ± 0.1; 1 indicating emaciated and 9 indicating obese) at the start of treatment. Cows on M diets maintained body weight (BW) and BCS, and R cows lost 1% of their initial BW weekly until they were anoestrus. When R cows were anoestrus their diets were increased to allow BW gain and resumption of ovarian activity. Relationships among concentrations of IGF-I, thyroxine, non-esterified fatty acids (NEFA), glucose, insulin, luteinizing hormone (LH), and progesterone in blood samples were determined. Anoestrus occurred when restricted cows had lost 24 ± 0.9% of their BW, had a BCS of 3.5 ± 0.1, and had nadir concentrations of IGF-I and thyroxine. Serum concentrations of IGF-I and thyroxine were reduced (P < 0.01) in R compared with M cows, except during realimentation when R cows had greater concentrations of thyroxine. Concentrations of IGF-I in M cows were positively correlated with concentrations of insulin (r = 0.31), glucose (r = 0.21) and progesterone (r = 0.24). In R cows, concentrations of IGF-I were positively correlated with insulin (r = 0.39), glucose (r = 0.23) and LH (r = 0.37). Mean weekly ambient temperatures were negatively correlated with IGF-I (r = −0.16), glucose (r = −0.37) and thyroxine (r = −0.40) in M cows. Our data indicate that ambient temperature and nutrient intake may both work to regulate concentrations of hormones and reproductive function in cattle.

Effects of supplementary feeding and suckling intensity on postpartum reproductive performance of small East African Zebu cows

Small East African Zebu cows (n = 120) which calved during the dry season were used to determine the effects of postpartum nutritional supplementation and suckling intensity on body weight, body condition score, reproductive performance and on calf mortality and preweaning growth performance. Cows were allocated based on calving body weight to either receive a supplementary feed of molasses blocks containing 10% urea or to serve as controls and to be grazed only. Within nutritional groups, cows were further assigned either to continuous suckling or to restricted suckling twice daily. Intact bulls were introduced 21 days after the first cow had calved, and data were collected for 8 months. Calving body weight and body condition score of dams ranged from 186 to 192 kg and from 3.8 to 4.2 and did not differ among the treatment groups. Supplementary feeding significantly (P<0.05) reduced calf mortality from 40 to 20%, while restricted suckling reduced mortality by 13% from 36 to 23%. Body weight and body condition score did not vary between groups during the supplementation period. Over the 8-month period, 65% of supplemented and 53% of control cows exhibited estrus (P>0.05). A significantly (P<0.05) karger percentage of restricted suckled cows showed estrus than of continuously suckled cows (74 vs 42%). The postpartum estrus interval was shorter by 54 days in supplemented than in control cows and by 13 days in restricted than in continuously suckled cows. The pregnancy rate was higher in supplemented than in control cows (37 vs 33%; P>0.05) and in restricted than in continuously suckled (46 vs 22%; P>0.05) cows.

Insulin-like growth factor I in follicular development and function in postpartum beef cows.

The objective of this study was to determine whether nutrition affects follicular growth and(or) steroid and insulin-like growth factor I (IGF-I) concentrations in follicular fluid. Beginning 6 d after calving, Hereford-cross cows (n = 28) were fed either 14 (ad libitum) or 7 (restricted) kg.animal1.d-1 of chopped alfalfa-brome hay. Half the cows in each treatment were ovariectomized on d 20 (OVX-20) and the remaining half on d 35 (OVX-35) postpartum. Cow weight and condition score were recorded weekly, and blood was collected thrice weekly for determination of insulin, IGF-I, glucose, and free fatty acid (FFA) concentrations. At ovariectomy, follicular fluid from each follicle greater than or equal to 4 mm in diameter was aspirated for determination of IGF-I, progesterone (P4), and estradiol-17 beta (E2) concentrations. Restricted cows lost more weight after calving than did ad libitum cows (P less than .0001), although all cows lost similar amounts of body condition (time postpartum, P = .008). Concentrations of FFA were elevated (P less than .0001) in restricted cows from wk 2 through 5 after calving but did not change with time in ad libitum cows. Plasma concentrations of glucose were lower in restricted than in ad libitum cows (59.6 +/- .4 vs 61.8 +/- .4 mg/dl; P = .05), but insulin and IGF-I were similar (P greater than .10) between dietary treatments.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of nutritional restriction during late gestation on production measures and passive immunity in beef cattle.

A 2-yr study was conducted to examine the effects of nutritional restriction of beef cows during the last 90 d of gestation on neonatal immunity and production. Cows were fed corn silage, soybean meal diets; dietary treatments consisted of 1) control (CO), 100% of the NRC (1984) requirements for protein and energy, or 2) restricted (RS), 57% of the NRC requirements for energy and protein. All cows received adequate amounts of this diet postpartum. Each year, 26 Angus cows were grouped by age and weight:height ratio (WT:HT) and allotted randomly to treatments. Calves born to dams within each nutritional treatment group were allotted to one of two colostral treatments: 1) colostrum from their dam, or 2) colostrum from a cow from the other nutritional treatment group. Calves from restricted dams had higher cortisol (33.8 vs 26.1 ng/ml) and lower triiodothyronine (T3) (3.82 vs 4.01 ng/ml) concentrations (P less than .05). Maternal nutrition did not affect either colostrum immunoglobulin G (IgG) concentration (43.0 vs 39.5 mg/ml for RS and CO, respectively) or the calves' serum IgG concentration (19.06 vs 20.17 mg/ml IgG at 24 h for RS and CO, respectively). Yet, calves fed colostrum from restricted cows tended to have lower serum IgG concentration (17.2 vs 22.0 mg/ml IgG at 24 h).

Nutritional anestrus in beef cows: body weight change, body condition, luteinizing hormone in serum and ovarian activity.

Multiparous Hereford cows (n = 22) with moderate to good body condition scores (BCS) were randomly allotted to maintenance (M) or restricted (R) diets under drylot conditions. Cows on M diets received adequate feed to maintain initial BW, whereas R cows were fed to lose 1% of their initial BW weekly until luteal activity ceased. When most of the R cows became anestrous, their diet was increased to allow BW gain and resumption of ovarian cyclicity. Body weights and BCS were recorded weekly and luteal activity was assessed by weekly determination of progesterone in plasma. Concentrations of LH in serum were quantified in weekly samples and in samples obtained frequently at four selected times. Restricted cows had reduced BW (P less than .01) by 5 wk and reduced BCS (P less than .01) by 15 wk compared with M cows. Luteal activity ceased after 26 +/- 1 wk of reduced nutrient intake in 91% of the R cows; R cows had lost 24.0 +/- .9% of their initial BW and had a BCS of 3.5 +/- .3. Lack of luteal activity was associated with absence of behavioral estrus. Estrous cycles resumed 9 +/- 2 wk after the diet of R cows was increased, at which time R cows weighed 12 +/- 3% less than at the start of the experiment and had a BCS of 4.6 +/- .2. Concentrations of LH in serum samples obtained weekly were reduced (P less than .01) in R cows compared with M cows. In addition, LH pulse frequency was reduced (P less than .05) when R cows were initiating anestrus.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunoglobulin levels in serum and colostral whey of protein-metabolisable energy restricted beef cows

Aberdeen Angus cows were fed adequate diets or diets restricted in protein and, or metabolisable energy for the last 156 days of gestation to determine effects of nutritional restriction on concentrations of immunoglobulins in serum and colostral whey. There were no significant interactions between the effects of low protein and metabolisable energy on immunoglobulin concentrations. Thus, observed differences in immunoglobulin concentrations between the restricted and adequate dietary groups were attributed to the main effects of treatment. Low protein or metabolisable energy had little overall effect on serum IgM concentrations although levels began to decrease sooner in gestation in restricted animals than in those fed adequate diets. Concentrations of IgG1 in serum of all animals were similar and a precipitous decrease in concentration was noted at about 240 days of gestation and this decrease continued until parturition. Serum IgG2 concentrations increased in all animals as parturition approached. Immunoglobulin concentrations in colostral whey were either similar to or tended to be slightly higher in dietary restricted animals than in animals fed adequate diets although the differences were not significant.

Phospholipids and Fat Secretion by Cows on Normal and Low Fiber Diets: Lactational Trends

Daily yields of milk, milk fat, phospholipids, and fatty acids were measured weekly during lactations of two groups of cows on a normal and restricted roughage diet. Milk yield was higher in normal cows during the initial 15 wk of lactation. Fat production decreased and was consistently lower in milk from cows on restricted roughage (from 1.2 to .4 in normal and from .8 to .3 kg/day for restricted). Phospholipid secretion decreased from an average 7g to 3 g/day in both groups. The concentration of phospholipid in both milks fluctuated during lactation (20 to 30 mg/100ml milk), but in milks from restricted cows it tended to increase with progress of lactation. Milk lipids from cows on restricted diets had higher phospholipid to fat ratio, (1.0 to 1.5 compared to .5 to .6g phospholipid/100g fat for milk from normal cows). Composition of the phospholipid classes changed slightly during lactation. Phosphatidylinositol changed most, increasing from 4 to 10 and 6 to 8% in normal and restricted milks, respectively. Fatty acids of short and medium chain lengths (C6 to C14) followed a typical quadratic regression in normal milks increasing from 10 to 30% of the total fatty acids during the first 25 wk of lactation. In restricted milk these fatty acids were already high (25%) within 2 wk and followed a linear regression with lactation. Both palmitic and stearic acid were lower in milk from restricted cows while oleic and linoleic acid were higher particularly after 10 wk of lactation.

Environmental Heat and Partial Water Restriction Effects on Body Fluid Spaces, Water Loss, Body Temperature, and Metabolism of Holstein Cows

The effects of partial water restriction on metabolism, body fluid compartments, and water balance were measured in seven mature nonlactating Holstein cows at two constant environmental temperatures, 18 and 32C. For 7 days at each temperature, water was restricted to 50% of ad libitum consumption.Partial water restriction at 18C caused a 50% reduction in water loss with a reduction in total body fluid volume mainly from the extravascular fluid compartment. This was followed by a reduction in feed consumption and metabolism. At 32C partial water restriction caused a great reduction in water loss through urine and feces, allowing more of the water to be used for heat loss by vaporization.Partial water restriction, unlike total water withdrawal, did not change the volumes of vascular compartments at either normal or high temperatures. However, animals exposed to normal and high temperatures respond differently to water restriction. At 18C similar percentage reductions (approximately 50%) occur in urine, fecal water, and total vaporization to reduce water loss during water restriction. But at 32C water loss is reduced mainly by reduction of urine and fecal water, rather than vaporization.Comparison between ad libitum animals at the two temperatures showed that heat caused a 15.9% reduction in metabolism. Water restricted cows, compared to ad libitum cows at 32C, showed a 17.0% reduction in metabolism. Results suggest the reduced metabolism is a compensatory mechanism to reduce internal heat production in an environment of high external heat and low water availability. Also, insignificant reduction in blood and plasma volumes produced available fluids for heat loss through vaporization when water was restricted at a high temperature.