ADLIB Animals Research Articles

Effect of dietary restriction and subsequent realimentation on hepatic oxidative phosphorylation in cattle

Compensatory growth (CG) is a naturally accelerated growth which occurs upon realimentation, following a prior period of dietary restriction. The process is harnessed worldwide as a management practice to reduce feed costs in beef cattle production. The objective of this study was to assess the potential contribution of hepatic cellular mitochondrial capacity to CG through global hepatic oxidative phosphorylation gene expression analyses as well as functional mitochondrial enzyme activity assays. Holstein–Friesian bulls were separated into two groups: (i) restricted feed allowance for 125 days (Period 1) (RES; n = 30) followed by ad-libitum feeding for 55 days (Period 2) or (ii) ad-libitum access to feed throughout (Periods 1 and 2) (ADLIB; n = 30). At the end of each period, 15 animals from each treatment group were slaughtered and hepatic tissue was collected. Tissue samples were subjected to RNAseq and spectrophotometric analysis for the functional assessment of mitochondria. RES and ADLIB groups grew at 0.6 kg/day and 1.9 kg/day, respectively, during Period 1. During Period 2, the RES group underwent CG growing at 2.5 kg/day, with ADLIB animals gaining 1.4 kg/day. Oxidative phosphorylation genes were differentially expressed in response to both dietary restriction and CG. Spectrophotometric assays indicated that mitochondrial abundance was greater in animals undergoing dietary restriction at the end of Period 1 and subsequently reduced during realimentation (P < 0.02). Results indicate that mitochondrial capacity may be enhanced during dietary restriction to more effectively utilize diet-derived nutrients. However, enhanced mitochondrial capacity does not appear to be directly contributing to CG in cattle.

PSII-34 Comparison of the activity level of high and low residual feed intake beef steers

Abstract Activity level may affect residual feed intake (RFI), and cattle that move more may have less energy for gain. We compared activity level in high and low RFI beef steers under different nutritional conditions. Lying time, lying duration and lying bouts were recorded at 1-minute intervals utilizing Hobo G Pendant Loggers attached to the right hind leg. To identify RFI classification, 57 Angus-cross steers were individually housed and offered ad libitum access to a TMR for 56 d. RFI was defined as the residual of the regression of DMI on mid-test BW0.75 and ADG. High and low RFI groups (14 steers each) were defined as &amp;gt; 0.5 SD above or below the mean of zero, respectively. Ad libitum feeding was followed by restricted feeding at 75% of previous ad libitum DMI/BW0.75. After 56 d ad libitum feeding, steers were moved to group pens, ad libitum fed 4 days (ADLIBFED), then fasted 4 days (ADLIBFASTED). This was followed by the 56 d individual restricted feeding, after which, steers were moved to group pens, fed 4 days of restricted DMI (RESTRICTFED), then fasted 4 days (RESTRICTFASTED). There was no difference in lying time (800 and 804 minutes/day, P = 0.85), lying bouts per day (9.8 and 11.4, P = 0.16) and lying duration (99 and 84 minutes/bout, P = 0.18) between low RFI and high RFI cattle, respectively. Fasted animals had less lying time each day (P &amp;lt; 0.05), manifested by fewer lying bouts per day (P &amp;lt; 0.05), that tended (P &amp;gt; 0.05) to be slightly longer than fed animals. Ad lib animals tended (P &amp;gt; 0.05) to have less lying time each day, with a similar number of lying bouts per day, that were slightly (P &amp;gt; 0.05) shorter than restricted animals. Although activity is not affected by RFI level, results suggest that periods of limited feed availability increases activity level.

Effect of dietary restriction and subsequent re-alimentation on the transcriptional profile of bovine jejunal epithelium.

Compensatory growth (CG), an accelerated growth phenomenon which occurs following a period of dietary restriction is utilised worldwide in animal production systems as a management practise to lower feed costs. The objective of this study was to evaluate the contribution of jejunal epithelial to CG in cattle through transcriptional profiling following a period of dietary restriction as well as subsequent re-alimentation induced CG. Sixty Holstein Friesian bulls were separated into two groups; RES and ADLIB, with 30 animals in each. RES animals were offered a restricted diet for 125 days (Period 1) followed by ad libitum feeding for 55 days (Period 2). ADLIB animals had ad libitum access to feed across both periods 1 and 2. At the end of each period, 15 animals from each treatment group were slaughtered, jejunal epithelium collected and RNAseq analysis performed. Animals that were previously diet restricted underwent CG, gaining 1.8 times the rate of their non-restricted counterparts. Twenty-four genes were differentially expressed in RES compared to ADLIB animals at the end of Period 1, with only one gene, GSTA1, differentially expressed between the two groups at the end of Period 2. When analysed within treatment (RES, Period 2 v Period 1), 31 genes were differentially expressed between diet restricted and animals undergoing CG. Dietary restriction and subsequent re-alimentation were associated with altered expression of genes involved in digestion and metabolism as well as those involved in cellular division and growth. Compensatory growth was also associated with greater expression of genes involved in cellular protection and detoxification in jejunal epithelium. This study highlights some of the molecular mechanisms regulating the response to dietary restriction and subsequent re-alimentation induced CG in cattle; however the gene expression results suggest that most of the CG in jejunal epithelium had occurred by day 55 of re-alimentation.

Intake, apparent digestibility, and nutrient requirements for growing Nellore heifers and steers fed two levels of calcium and phosphorus

Nutrient apparent digestibility, intake, performance, microbial efficiency, and energy and protein requirements for growing Nellore heifers and steers were evaluated, fifty animals were used, 32 Nellore heifers and 18 Nellore steers. Four animals of each gender used as baseline reference animals were slaughtered at the beginning of the experiment. Four animals from each gender were fed at MAIN receiving 11g/kgBW, whereas 10 steers and 24 heifers were assigned to the ADLIB group. The ADLIB heifers were divided further into 4 groups according to the dietary treatment: (1) Ca and P fed at their proposed requirements (CaPR) with a 50:50 roughage:concentrate (R:C) diet, (2) CaPR with a 70:30 R:C diet, (3) 43% of their proposed requirements for Ca and 80% of their requirements for P (CaPL) with a 50:50 R:C diet, and (4) CaPL with a 70:30 R:C diet. The ADLIB and MAIN steers were fed CaPR with a 50:50 R:C diet. Half of the ADLIB steers and heifers were slaughtered at day 50; the other ADLIB animals were slaughtered after 100 days of the feeding period, whereas all MAIN animals were slaughtered at day 100. Total feces and urine were collected from all animals for 72h prior to slaughter. After slaughter, EBW was measured. The NEm and MEm requirements were estimated by exponentially relating heat production with metabolizable energy intake; NEg was estimated from EBW and EBG. The NPg was estimated from EBG and RE. Dry matter digestibility and the apparent absorption and retention of Ca and P were similar across Ca and P treatments. Final body weight, and consequently ADG, was greater (P<0.05) for heifers receiving the high concentrate compared to the low concentrate diet, but dietary Ca and P concentration did not affect (P>0.05) performance. The NEm and MEm requirements were 294 and 496kJ/kgEBW0.75, respectively. Net protein for maintenance was 1.28g/kgBW0.75 and NEg and NPg were estimated from the following equations: NEg=0.222×EBW0.75×EBG0.6263 and NPg=137.53×EBG−0.038×RE, respectively. Under the conditions of this experiment, reducing the dietary concentrations of Ca and P had no significant impact on intake, digestibility, or performance of growing Nellore heifers and steers.

Brief Refeeding Restores Reproductive Readiness in Food-Restricted Female Musk Shrews (Suncus murinus)

Food deprivation blocks sexual behavior and disrupts estrous cycles in mammals. We asked whether reduced copulatory behavior, produced by limited food intake, could be reversed by brief refeeding intervals in the female musk shrew. In Experiment 1, animals were food restricted to 60% of ad lib (FR), and an additional group of FR females were refed for 90 min prior to testing (RF). Refed and ad lib (AL) fed females were significantly more likely to mate than FR females. To test the hypothesis that food-induced restoration of copulatory behavior is not the result of changes in peripheral steroids, we repeated Experiment 1 using ovariectomized and testosterone-implanted females. The results from Experiment 2 were similar to those found in the first study. Next, a more severe refeeding schedule was employed; females were restricted to 50% of ad lib intake. Females in the RF and FR groups were significantly less likely than the AL animals to mate. In the last experiment, females were food restricted to 50% and longer refeeding intervals were employed. Four and one-half hours of food intake did not reinstate sexual behavior, but females refed for 12 h were as likely to mate as ad lib fed controls. We also did not detect any differences in plasma concentrations of testosterone and cortisol in AL, FR, and RF ovary-intact animals. These results define a nutritional threshold for copulatory behavior in the musk shrew. Since this species is highly sensitive to small alterations in food intake, it is a useful model for studies of interactions between metabolic fuels and behavior.

The Effect of Food Intake from 2 to 24 Weeks of Age on LHRH-I Content in the Median Eminence and Gonadotrophin Levels in Pituitary and Plasma in Female Broiler Breeder Chickens

The present study describes the effect of long-term food restriction on hypothalamopituitary function in the broiler breeder hen during the period prior to sexual maturity. From 1 week of age onward, chickens were divided into 3 groups: one group received foodad libitum(Ad lib); a second group was fed a restricted quantity of food (Res); and a third group was restricted to obtain an intermediate body weight (Int) in between groups one and two. The effects of these feeding regimes on hypothalamopituitary function were assessed by measuring the amounts of cLHRH-I stored in the median eminence (ME) and the pituitary content and plasma levels of gonadotrophins. The Res group had significantly lower levels of cLHRH-I in the ME compared to the Ad lib animals. In all groups, there was a major increase in cLHRH-I in the median eminence about 3 weeks before onset of lay. The age of first oviposition was delayed by 2 and 6 weeks in the Int and Res groups, respectively, compared to the Ad lib animals, indicating that body weight gain patterns are not directly related to the appearance of the first egg. The attainment of sexual maturity may be associated with a threshold value of cLHRH-I stored in the ME in the Ad lib and Int birds. The pituitary LH and FSH contents (after week 16) were positively related to the amount of cLHRH-I in the ME. Plasma FSH concentrations in Ad lib and Int chickens peaked about 3 weeks before the first oviposition and this prepubertal peak was associated with increased pituitary FSH and ME cLHRH-I. There were however no relationships between plasma LH concentrations and pituitary LH content and between plasma LH and cLHRH-I amounts in the ME. The present study demonstrates that the delayed sexual maturation, caused by a chronic food restriction, may be associated with (1) delayed ovarian and oviductal growth, (2) decreased cLHRH-I storage in the ME, and (3) lower levels of LH and FSH in the pituitary. These hormones were however not directly related to levels of food restriction.

Nutritional status and behavior during lactation

Effects of chronic maternal food restriction and time of day on maternal and pup behaviors were examined in ovariectomized Sprague-Dawley rats ( n = 26). Dams were fed ad lib (AL) or were restricted to 85% (85 AL) or 70% (70 AL) of ad lib intake. Dams and their 5-pup litters were observed for 45 min at night on days 9, 14, and 19 of lactation and during the day on day 14. A novel behavioral instrument was used to observe maternal and pup behaviors. At night, food-restricted animals engaged in more nursing behaviors than AL animals. Differential pup stimuli may account for this difference. AL animals engaged in more nursing behaviors during the day than night, whereas 70 AL animals demonstrated the opposite diurnal pattern. Time of feeding may explain this difference. On the other hand, 85 AL animals behaved similarly during the day and at night. Therefore, alterations in circadian behavior patterns are less pronounced in rats mildly restricted (85 AL) than in rats more food restricted (70 AL).

Vasopressin deficiency and blood glucose interactions on passive avoidance behavior

The performance of a passive avoidance task (measured for two trials based upon number of complete step-downs and latency to respond) and blood glucose levels were examined in five groups of animals. The groups included vasopressin-deficient (DI) and vasopressin-containing (LE) rats under ad lib (AL) and food-restricted (FR) conditions, as well as DI-FR animals provided with access to an 8% sucrose solution (SUC). In the AL condition, no significant differences were found between DI and LE animals in either step-down occurrences or blood glucose levels. However, the DI animals were significantly slower in latency to respond in trial 1. With FR, the LE animals resembled the LE-AL animals in both passive avoidance behavior and blood glucose levels. The DI-FR animals that were not provided with SUC showed an impairment in passive avoidance behavior and low blood glucose levels, whereas DI-FR animals provided with SUC showed an amelioration of passive avoidance deficiencies and had blood glucose levels comparable to AL animals and LE-FR animals. On trial 2, a significant negative correlation was found between number of step-down occurrences and blood glucose levels, and a significant positive correlation was found between latency to respond and blood glucose levels. The experiment demonstrates that: 1) because DI rats have a different responsiveness in novel situations, caution must be exercised in using response latency as a measure of passive avoidance performance in the AL condition; 2) AL and FR conditions produce different responses in DI, but not LE, animals; 3) deficiencies in passive avoidance behavior in DI-FR rats can be ameliorated by the consumption of exogenous carbohydrate; and 4) there is a significant correlation between blood glucose levels and passive avoidance behavior.

Long-term potentiation is lost in aged rats but preserved by calorie restriction.

Recordings of synaptic population responses, post-tetanic potentiation (PTP) and long-term potentiation (LTP) were made from area CA1 in hippocampal slices from ad libitum-fed rats at about 2 and 24 months of age, and also in animals at about 24 months of age that had been restricted to 60% of the caloric intake of control animals since weaning. Both PTP and LTP were greatly reduced in the old ad-lib animals. Calorically-restricted rats at about 24 months of age showed hippocampal responses with initial peak amplitudes more like those of 2-month controls than the ad-lib animals at 24 months. These observations suggest that calorie restriction preserves nervous-system functions, including indicators of plasticity such as LTP, which are otherwise lost in aging.